Dissertations / Theses on the topic 'Offshore geothermal energy system'

Ice rinks are energy intense industrial applications. A typical single sheet ice rink in Sweden uses about 1000 MWh/season. A state-of-the art ice rink systems can use less than 500 MWh/season, indicating the potential for improvements. According to several investigations CO2 refrigeration system with heat recovery has proven to be energy-efficient and cost-effective solution in ice rinks.To further improve the efficiency, geothermal function may be added feature. The objective of this study is to evaluate the geothermal function from techno-economic perspective for a typical ice rink in Sweden. Modelling of several scenarios has been performed. Obtained results suggest that CO2 refrigeration system with 2-stage heat recovery, if upgraded with geothermal function, can save between 1.7 to 6.8% of energy annually. In the best case, this study suggests the geothermal function would pay back in 16.4 years.
Ishallar är energikrävande industriella applikationer. En typisk ishall i Sverige använder cirka 1000 MWh / säsong. Ett toppmodernt ishallsystem kan använda mindre än 500 MWh / säsong, vilket indikerar stora förbättringsmöjligheter. Enligt flera undersökningar har CO2-kylsystem med värmeåtervinning visat sig vara energieffektivt och kostnadseffektivt i ishallar.För att ytterligare förbättra effektiviteten kan geotermisk funktion läggas till. Syftet med denna studie är att utvärdera den geotermiska funktionen ur ett tekno-ekonomiskt perspektiv för en typisk ishall i Sverige. En modellering av flera scenarier har utförts. Resultaten antyder att CO2-kylsystem med 2-steg värmeåtervinning, om det uppgraderas med geotermisk funktion, kan spara mellan 1,7 och 6,8% energi årligen. I bästa fall antyder denna studie att den geotermiska funktionen skulle betala tillbaka om 16,4 år.

The Mountain Home (MH) geothermal system of the western Snake River Plain (SRP) magmatic province was discovered in 2012 by the Snake River Geothermal Drilling Project. Artesian flowing water with a temperature of 150°C was encountered at a depth of 1745 m below ground surface (mbgs) and extensive mineralized fracture networks of pectolite-prehnite, calcite, and laumontite were discovered in the recovered core. The objectives of this study are to: 1) describe the thermal and compositional history of past geothermal fluids, and 2) compare these fluids to modern fluids in order to characterize the evolution of the MH geothermal system and the geothermal potential of the western SRP. Core observations, thin section petrography, X-ray diffraction, and Electron Microprobe analyses were performed in order to describe mineral parageneses of various alteration zones. Carbon and oxygen stable isotope ratios along with temperatures of homogenization from fluid inclusions in hydrothermally precipitated calcite were measured along ~100 m of basalt core from 1709-1809 mbgs. The d13CPDB values in calcite range from -7.2 to -0.43 ‰ and d18OPDB values range between -20.5 and -15.9 ‰. An anomalous zone from 1722-1725 m depth displays a range in d13CPDB and d18OPDB of -1.9 to +0.88 ‰ and -17.1 to -8.1 ‰, respectively, suggesting non-equilibrium fractionation due to boiling. Carbon isotopic ratios suggest a mixture of deep-seated mantle derived and meteoric fluids. Fluid inclusion microthermometry has identified primary inclusions with trapping temperatures ranging from 168-368°C. A calcite-water geothermometer used to calculate paleo-fluid oxygen isotopic composition (-0.43 to +7.2 ‰ SMOW) and a comparison with present-day fluid oxygen isotopic composition (-3.2 ‰ SMOW) reveals a cooling trend with potential mixing of meteoric waters and deeply derived fluid. The MH geothermal system has cooled over time and reflects potentially less, if any magmatic fluid input presently into the system as there was in the past.

A comparison between a traditional fixed high voltage direct current energy transmission system and a mobile transmission system utilizing vanadium redox flow batteries has been conducted in this degree work.  The purpose of this comparison was to evaluate if a mobile energy transmission system could be competitive in terms of energy efficiency and cost-effectiveness for use in offshore wind power applications. A literary study was made to fully grasp the various technologies and to create empirical ground of which cost estimation methods and energy calculations could be derived. A specific scenario was designed to compare the two transmission systems with the same conditions. To perform the comparison, a model was designed and simulated in MATLAB. The results from the model showed that the flow battery system fell behind in energy efficiency with a total energy loss of 33.3 % compared to the 11.7 % of the traditional system, future efficiency estimations landed it at a more competitive 17.5 %. The techno-economic results proved that a mobile flow battery system would be up to nine times more expensive in comparison to a traditional transmission system, with the best-case scenario resulting in it being roughly two times more expensive. The main cause of this was found out to be the expensive energy subsystem, specifically the electrolyte, used in the flow battery system. Several environmental risks arise when using a flow battery system with this electrolyte as well which could harm marine life severely. In conclusion; with further development and cost reductions, a case could be made for the advantages of a truly mobile energy transmission system. Specifically, in terms of the pure flexibility and mobility of the system, allowing it to circumvent certain complications. The mobility of the system gives the possibility of selling energy where the spot prices are at their highest, providing a higher revenue potential compared to a traditional fixed system. As for now though, it is simply too expensive to be a viable solution.

The ground source resources are becoming more and more popular and now the ground source heat pumps are frequently used for heating and cooling different types of buildings. This thesis aims at giving a contribution in the development of the thermal modelling of borehole heat storage systems. Furthermore, its objective is to investigate the possibility of implementing of a GSHP (ground source heat pump) with vertical boreholes, in order to deliver the heating and cooling demand for a passive house and to emphasize some certain advantages of this equipment even in the case of a small building (e.g. residential house). A case study is presented to a suitable modelling tool for the estimation of the thermal behaviour of these systems GSHP by combining the outcome from different modelling programs. In order to do that, a very efficient residential solar house (EFden House – a passive residential single-family house, which was projected and built in Bucharest with academic purposes) is being analysed. The numerical results are produced using the software DesignBuilder, EED (Earth Energy Designer) and a sizing method for the length of the boreholes (ASHRAE method). The idea of using 2 different modelling programs and another sizing method for the borehole heat exchanger design (ASHRAE method) is to make sure that all the calculations and results are valid and reliable when analysing such a system theoretically (in the first phases of implementing a project), before performing a geotechnical study or a thermal response test in order to assess the feasibility of such a project beforehand. The results highlight that the length of the borehole, which is the main design parameter and also a good index in estimating the cost of the system, is directly influenced by the other fundamental variables like thermal conductivity of the grout, of the soil and the heat carrier fluid. Also, some correlations between these parameters and the COP (coefficient of performance) of the system were made. The idea of sizing the length of boreholes using two different methods shows the reliability of the modelling tool. The results showed a difference of only 2.5%.  Moreover, the length of borehole is very important as it was calculated that can trigger a difference in electricity consumption of the GSHP up to 28%. It also showed the fact that the design of the whole system can be done beforehand just using modelling tools, without performing tests in-situ. The method aims at being considered as an efficient tool to estimate the length of the borehole of a GSHP system using several modelling tools.

The presentation was made via Skype due to the programme being online based

Offshore renewable energy systems, such as Wave Energy Converters or an Offshore Wind Turbine, must be designed to withstand extremes of the weather environment. For this, it is crucial both to have a good understanding of the wave and wind climate at the intended offshore site, and of the system reaction and possible failures to different weather scenarios. Based on these considerations, the first objective of this thesis was to model and identify the extreme wind speed and significant wave height at an offshore site, based on measured wave and wind data. The extreme wind speeds and wave heights were characterized as return values after 10, 25, 50, and 100 years, using the Generalized Extreme Value method. Based on a literature review, fragility curves for wave and wind energy systems were identified as function of significant wave height and wind speed. For a wave energy system, a varying failure rate as function of the wave height was obtained from the fragility curves, and used to model the resilience of a wave energy farm as a function of the wave climate. The cases of non-constant and constant failure rates were compared, and it was found that the non-constant failure rate had a high impact on the wave energy farm's resilience. When a non-constant failure rate as a function of wave height was applied to the energy wave farm, the number of Wave Energy Converters available in the farm and the absorbed energy from the farm are nearly zero. The cases for non-constant and an averaged constant failure of the instantaneous non-constant failure rate as a function of wave height were also compared, and it was discovered that investigating the resilience of the wave energy farm using the averaged constant failure rate of the non-constant failure rate results in better resilience. So, based on the findings of this thesis, it is recommended that identifying and characterizing offshore extreme weather climates, having a high repair rate, and having a high threshold limit repair vessel to withstand the harsh offshore weather environment.

The demand for energy is increasing worldwide. All applications contributed to increase the demand of all energy industry, and therefore the effect on the environment and the rise in pollution increased significantly. This is considered a large problem, and researchers focused their research on renewable energy for reducing the cost of energy in the future. Geothermal energy has significant impact as a source of electricity generation since it will not harm the environment. There are more than twenty countries that benefit from geothermal plants, which generate more than 6000 megawatts .Three alternatives of geothermal energy technology (GHP, Direct use of Geothermal Heat, and Geothermal Electricity) can be used for supporting electrical systems in Oregon. At the same time, the success of using the geothermal energy alternatives in Oregon relies on different goals for achieving the best geothermal development. Oregon has been ranked third in the potential use of geothermal energy after Nevada and California. The objective from the research study was to develop an assessment model framework that can be used for supporting cost effective renewable energy in Oregon by the development of geothermal energy sources. This research of study was done by using the Hierarchical Decision Model (HDM) and consisted of four levels: Mission, objectives, goals, and alternative. Criteria used in this research study are based on five objectives to know what are the most important factors in the decision-making process. These objectives are: social, environmental, economical, technical, and political. The decision model connected objectives, goals, and alternative for obtaining the accurate decision. HDM used for this purpose to analyze the result of data collected from experts. Seven experts who had experience in the geothermal field participated in this research study, and they gave their judgment in the questionnaire survey link by using pair-wise comparison method. The outcome analysis of the results showed that in terms of objectives that Minimizing Environmental Impact was rated at the highest value at 0.26 with respect to the mission. Within the category of Minimizing Environmental Impact, Seismic Activity and GHG Emissions had higher values. The results show that "Geothermal Electricity," with a rating of 43%, was ranked as the most important alternative with respect to mission, objectives, and goals. "Direct Use of Geothermal Heat" was ranked as the second most important alternative with 31%. The results of this research study were discussed with the experts to get their feedback, and learn from them what requirements are necessary for improvement in the geotechnical energy sector for future research. The experts agreed that this methodology is a good approach to help reach the right decision since this methodology (HDM) divides the problem into small sets, which will make the decision process easier.

The present work addresses the thermodynamic optimization of small binary-cycle geothermal power plants. The optimization process and entropy generation minimization analysis were performed to minimize the overall exergy loss of the power plant, and the irreversibilities associated with heat transfer and fluid friction caused by the system components. The effect of the geothermal resource temperature to impact on the cycle power output was studied, and it was found that the maximum cycle power output increases exponentially with the geothermal resource temperature. In addition, an optimal turbine inlet temperature was determined, and observed to increase almost linearly with the increase in the geothermal heat source. Furthermore, a coaxial geothermal heat exchanger was modeled and sized for minimum pumping power and maximum extracted heat energy. The geofluid circulation flow rate was also optimized, subject to a nearly linear increase in geothermal gradient. In both limits of the fully turbulent and laminar fully-developed flows, a nearly identical diameter ratio of the coaxial pipes was determined irrespective of the flow regime, whereas the optimal geofluid mass flow rate increased exponentially with the Reynolds number. SeveORCs were observed to yield maximum cycle power output. The addition of an IHE and/or an Oral organic Rankine Cycles were also considered as part of the study. The basic types of the FOH improved significantly the effectiveness of the conversion of the available geothermal energy into useful work, and increased the thermal efficiency of the geothermal power plant. Therefore, the regenerative ORCs were preferred for high-grade geothermal heat. In addition, a performance analysis of several organic fluids was conducted under saturation temperature and subcritical pressure operating conditions of the turbine. Organic fluids with higher boiling point temperature, such as n-pentane, were recommended for the basic type of ORCs, whereas those with lower vapour specific heat capacity, such as butane, were more suitable for the regenerative ORCs.
Dissertation (MEng)--University of Pretoria, 2013.
Mechanical and Aeronautical Engineering
unrestricted

The building stock in the European Union accounts for over 40% of final energy use, where the usage of non-residential buildings may be up to 40% higher than the residential sector. Improving building energy efficiency across all categories of buildings is one key goal of the European energy policies, made prominent by the Climate and Energy package, Energy Performance of Building Directive (EPBD) and Energy Efficiency Directive (EED). In this study, a simulation model of an office-building complex utilizing district heating was created using transient simulation software TRNSYS. The model was validated using consumption data provided by the facility owner, after which an investigation of the energy saving potential along with the economic viability of adapting a new heat- and power supply system was conducted. The system designs were comprised of a geothermal energy system in combination with a PV-system and electricity storage. It was concluded that the systems were sufficient in maintaining an adequate indoor climate. Furthermore, the investments were ascertained as profitable and resulted in a decreased building specific energy demand.

Major changes are taking place in the Sweden’s electricity system and steel industry. Through political agreements, the current government has set national goals of 100% renewable electricity generation and a net zero GHG emissions industry by 2040. This will be achieved by increasing renewable power generation, mainly wind power. In the steel industry, the steel manufacturing groups are beginning to transition to an electricity-based steel manufacturing processes to reduce their GHG emissions. The Swedish steel manufacturing group SSAB and the mining group LKAB, together with Vattenfall, are developing an alternative steel production process free from fossil-based sources. It is called HYBRIT, an alternative technique to reduce iron ore with hydrogen gas, instead of coal which is used today. By producing hydrogen with electrolysis, applying hydrogen reduction technology, and replacing coal powered blast furnaces with electrified arc furnaces for melting the steel, it is possible to create a green and environmentally friendly steel industry. This technique was simulated in a computer model where electricity flows and system component capacity requirements were calculated. The simulation was made of an existing steel manufacturing plant in Oxelösund. A hypothetical case was made where the plant has a fully incorporated HYBRIT steel production chain. Its main power source was a nearby offshore wind power farm which is a planned project by Svea Vind Offshore. Previous studies have simulated HYBRIT steel manufacturing in computer models. However, no similar studies have been made on how these systems operate with variable availability of renewable power. From two studied wind power farm layouts, the results found a relationship between the needed electrolysis capacity as a function of the concentration recycled steel used in the process and the yearly steel production demand. Using the stated goal of SSAB where they use 50% recycled steel as a reference, it was calculated that 286 – 309 MW electrolysis unitsis needed for a yearly steel production of 1.6 million tonnes.
Det sker stora förändringar inom Sveriges elkraftsystem och stålindustri. Den nuvarande regeringen har genom politiska överenskommelser satt nationella mål på 100% förnybar elproduktion, och nollnetto GHG utsläpp inom industrin, tills 2040. Det ska nås genom att öka förnyelsebar elproduktion, huvudsakligen vindkraft. I stålindustrin har ståltillverkningskoncernerna börjat övergå till en elektrifierad ståltillverkningsprocess för att minska utsläppen. Den svenska stålkoncernen SSAB, och gruvdriftskoncernen LKAB, tillsammans med Vattenfall utvecklar en alternativ ståltillverkningsprocess som är fri från fossila källor. Det heter HYBRIT, och är en alternativ metod för att reducera järnmalm med vätgas, i stället för kol som används idag. Genom att producera vätgas med elektrolys, installera vätgasreduktionsteknik, och ersätta de koldrivna masugnarna med eldrivna ljusbågsugnar för att smälta stålet, är det möjligt att skapa en grön och miljövänlig stålindustri. Denna teknik simulerades i en datormodell där elektricitetsflöden och begränsningarna på kapaciteten på systemkomponenterna beräknades. Simuleringen gjordes på ett existerande stålverk i Oxelösund. Ett hypotetiskt fall sattes upp där verket har inkorporerat hela HYBRIT stålproduktionskedjan. Den huvudsakliga kraftkällan var en närliggande havsbaserad vindkraftspark som är ett föreslagit projekt av Svea Vind Offshore. Tidigare studier har simulerat ståltillverkning med HYBRIT teknik i datamodeller. Men, det finns ingen liknade studie som har studerat hur dessa system fungerar med en varierande tillgänglighet på förnyelsebar effekt. Utifrån två studerade vindkraftsparkdesigner blev resultatet en relation mellan den behövda elektrolyskapaciteten som en funktion av andelen återvunnet stål i processen samt det årliga stålproduktionsbehovet. Genom att använda SSAB:s framtida mål där de använder 50% återvunnet stål som referens, beräknades det att 286 – 309 MW elektrolysenheter behövs för en årlig produktion på 1.6 millioner ton stål.

This thesis deals with a system for operation of directly driven offshore wave energy converters. The work that has been carried out includes laboratory testing of a permanent magnet linear generator, wave energy converter mechanical design and offshore testing, and finally design, implementation, and offshore testing of an underwater collector substation. Long-term testing of a single point absorber, which was installed in March 2006, has been performed in real ocean waves in linear and in non-linear damping mode. The two different damping modes were realized by, first, a resistive load, and second, a rectifier with voltage smoothing capacitors and a resistive load in the DC-link. The loads are placed on land about 2 km east of the Lysekil wave energy research site, where the offshore experiments have been conducted. In the spring of 2009, another two wave energy converter prototypes were installed. Records of array operation were taken with two and three devices in the array. With two units, non-linear damping was used, and with three units, linear damping was employed. The point absorbers in the array are connected to the underwater substation, which is based on a 3 m3 pressure vessel standing on the seabed. In the substation, rectification of the frequency and amplitude modulated voltages from the linear generators is made. The DC voltage is smoothened by capacitors and inverted to 50 Hz electrical frequency, transformed and finally transmitted to the on-shore measuring station. Results show that the absorption is heavily dependent on the damping. It has also been shown that by increasing the damping, the standard deviation of electrical power can be reduced. The standard deviation of electrical power is reduced by array operation compared to single unit operation. Ongoing and future work include the construction and installation of a second underwater substation, which will connect the first substation and seven new WECs.

The sustainable development of the offshore wind and wave energy sectors requires optimising the exploitation of the resources, and it is in relation to this and the shared challenge for both industries to reduce their costs that the option of integrating offshore wind and wave energy arose during the past decade. The relevant aspects of this integration are addressed in this work, and in particular the evaluation of the Wave Energy Converter (WEC) sub-system of a hybrid wind-wave energy converter: the state of the art of combined technologies; the definition of a novel hybrid prototype, based on a preliminary feasibility analysis of a conceptual proposal; and the evaluation of a simplified version of this prototype by means of physical and numerical modelling as a mean to set the reference and define new tools and methods for future evaluation and optimisation of the prototype. Because of the novelty of combined wave and offshore wind systems, fundamental knowledge was lacking as, for example a comprehensive review and classification, which was published as a journal paper framed in the present work. In particular, the core of this PhD thesis deals with the WEC sub-system of a hybrid device that integrates an Oscillating Water Column (OWC) device into the typical monopile substructure of an offshore wind turbine. A new prototype of the hybrid energy converter has been proposed, and a patent application was filled. Furthermore, an experimental set-up was designed, built and tested at a wave flume. On the basis of this experimental campaign the performance of the device is analysed. Finally, a full 3D-numerical mirror of the experimental set-up, including the hybrid energy converter, is defined and validated, and the flume enclosure effects studied for regular waves.

District heating and geothermal heating are in present times two established heating systems that are often compared against each other. The purpose of this work is to describe which factors influence the choice of heating system during the planning stage and what the costs are for each system. In this paper, a typical house model has been developed and used as a basis for the comparison of both systems. The comparison has been made in the form of energy calculations in the energy calculation program BV2, where heat requirements and regulatory requirements for energy performance have been compared in different geographical areas in Sweden. Furthermore, cost calculations have been carried out based on the energy calculations' results, where investment costs and annual costs have been set against each other. The result of the work shows how the measurement of energy performance differs from the actual amount of purchased energy due to geographical conditions. In the southern parts of Sweden, where the geographical correction factor is below 0, consumers are penalized by raising the primary energy number, unlike the northern parts where the primary energy number is instead lowered. Based on the cost calculations, it can be concluded that district heating, when available, is more economically advantageous in the short term. Geothermal heating on the other hand is a more profitable alternative in the long run.
Fjärrvärme och bergvärme är idag två etablerade värmesystem som ofta ställs mot varandra. Syftet med det här arbetet är att redogöra vilka faktorer som påverkar valet av värmesystem under projekteringsstadiet och vilka kostnaderna som finns för respektive system. I arbetet har en typisk husmodel tagits fram och använts som grund för jämförelsen av båda systemen. Jämförelsen har dels gjorts i form av energiberäkningar i energiberäkningsprogrammet BV2 där värmebehov och myndighetskrav på energiprestanda har jämförts i olika geografiska områden i Sverige. Vidare har kostnadsberäkningar genomförts utifrån energiberäkningarnas resultat där investeringskostnader och årliga kostnader har ställts mot varandra. Resultatet av arbetet visar hur måttet på energiprestanda skiljer sig från den faktiska mängden köpt energi på grund ut av geografiska förhållanden. I de södra delarna i Sverige där den geografiska korrigeringsfaktorn understiger 0 straffas konsumenter genom att primärenergitalet höjs, till skillnad mot de norra delarna där primärenergitalet istället sänks. Utifrån kostnadsberäkningarna kan man dra slutsatsen att fjärrvärme, när den finns tillgänglig, är mer ekonomiskt fördelaktigt på kort sikt. Bergvärme å andra sidan är ett mer lönsamt alternativ på lång sikt.

In the past two decades, a growing interest in alternative energy resources as a replacement to the non-renewable resources used now days. These alternatives include geothermal energy which can be used to generate power and reduce the demands on energy used to heat and cool buildings. Ground-coupled ventilation system is one of the many applications of the geothermal energy that have a lot of attention in the early 80â s and 90â s but all designs of the system where based on single case situations. On the other hand, computational fluid dynamics tools are used to simulate heat and fluid flow in any real life situation. They start to develop rapidly with the fast development of computers and processors. These tools provide a great opportunity to simulate and predict the outcome of most problems with minimum loss and better way to develop new designs. By using these CFD tools in GCV systems designing procedure, energy can be conserved and designs going to be improved. The main objective of this study is to find and develop a CFD modeling strategy for GCV systems. To accomplish this objective, a case study must be selected, a proper CFD tool chosen, modeling and meshing method determined, and finally running simulations and analyzing results. All factors that affect the performance of GCV should be taken under consideration in that process such as soil, backfill, and pipes thermal properties. Multiple methods of simulation were proposed and compared to determine the best modeling approach.
Master of Science

The wave energy converter developed at Uppsala University consists of a linear generator at the seabed driven by the motion of a buoy on the water surface. The energy absorbed by the generator is negatively affected by variations of the mean sea level caused by tides, changes in barometric pressure, strong winds, and storm surges. The work presented in this doctoral thesis aims to investigate the losses in energy absorption for the present generation wave energy converter due to the effect of sea level variations, mainly caused by tides. This goal is achieved through the modeling of the interaction between the waves and the point absorber. An estimation of the economic cost that these losses imply is also made. Moreover, solutions on how to reduce the negative effect of sea level variations are discussed. To this end, two compensation systems which adjust the length of the connection line between the floater and the generator are designed, and the first prototype is built and tested near the Lysekil research site. The theoretical study assesses the energy loss at about 400 coastal points all over the world and for one generator design. The results highlight critical locations where the need for a compensation system appears compelling. The same hydro-mechanic model is applied to a specific site, the Wave Hub on the west coast of Cornwall, United Kingdom, where the energy loss is calculated to be about 53 %. The experimental work led to the construction of a buoy equipped with a screw jack together with its control, measurement and communication systems. The prototype, suitable for sea level variations of small range, is tested and its performance evaluated. A second prototype, suitable for high range variations, is also designed and is currently under construction. One main conclusion is that including the compensation systems in the design of the wave energy converter will increase the competitiveness of the technology from an economic point of view by decreasing its cost per kWh. The need for a cost-effective wave energy converter with increased survivability emphasizes the importance of the presented research and its future development.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.
The recent climate change has forced people to live in extreme conditions, either excessive heat or cold, implying that they must adapt to survive in these situations. However, there are people who, because of their geographical condition and lack of resources, lack the means and tools to combat these climate changes. The context of this study is provided in a rural town located in the Arequipa region (Peru), whose inhabitants have to fight against frosts of up to −20 °C in an area without electricity. A viable solution to this problem is found through the design and implementation of a heating system using geothermal and photovoltaic energy, which are resources found in the area, according to a report of the Ministry of Energy and Mines. This study analyzes and researches the geographical and meteorological conditions of the region, for validating, through theory and simulations, whether the proposed system can supply the thermal energy required to maintain the indoor temperature at a minimum of 15 °C under extreme conditions. The system is designed after analyzing the best technological options and techniques currently available in the context studied for its ultimate financing and establishing guidelines and indicators for monitoring results.

Heating, Ventilating and Air Conditioning Systems (HVAC) are not only one of the most energy consuming components in buildings but also contribute to green house gas emissions. As a result often environmental design strategies are focused on the performance of these systems. New HVAC technologies such as Geothermal Heat Pump systems have relatively high performance efficiencies when compared to typical systems and therefore could be part of whole-building performance design strategies.

In collaboration with the Virginia Tech Corporate Research Center, Inc., this research studies the energy consumption and cost benefits of the Geothermal Heat Pump System that has been integrated and operated in the KnowledgeWorks I and II buildings located on the Virginia Tech campus.

The purpose of this thesis is to understand the energy and cost benefits of the Geothermal Heat Pumps System when compared to the conventional package variable air volume (VAV) with hot water coil heating and air-source heat pump systems using computer simulation and statistical models. The quantitative methods of building energy performance and life-cycle cost analyses are applied to evaluate the results of simulation models, the in-situ monitoring data, and the associated documents. This understanding can be expanded to the higher level of architectural systems integration.
Master of Science

Floating offshore wind power is a relatively new technology that enables wind turbines to float above the sea level, tied by anchors at the seabed. The purpose of this work is to develop an economic model for the technology in order to calculate the total cost of a planned wind farm. Cost data are retrieved from reports and academic journals available online. Based on these data, a model in Microsoft Excel is developed which calculates the Levelized cost of energy (LCOE) for floating wind power plants as a function of several input values. As an addition to this model, financing offshore projects are described using literature study and by doing interviews with three major companies, currently investing in offshore wind. As a result, the model allows the user to calculate Capital expenditures, Operating expenditures and LCOE for projects at any given size and at any given site. The current LCOE for a large floating offshore wind farm is indicated to be in the range of 138-147 £/MWh. The outline from interviews was that today there is no shortage of capital for funding wind projects. However, in order to attract capital, the governmental regulatory of that market has to be suitable since it has a crucial impact on price risks of a project.

Ground-coupled ventilation (GCV) is a system that exchanges heat with the soil. Because ground temperatures are relatively higher during the cold season and lower during the hot season, the system takes advantage of this natural phenomenon. This research focused on designing a ground-coupled ventilation system evaluation tool of many factors that affect system performance. The tool predicts the performance of GCV system design based on the GCV system design parameters including the location of the system, pipe length, pipe depth, pipe diameter, soil type, number of pipes, volume flow rate, and bypass system. The tool uses regression equations created from many GCV system design simulation data using Autodesk Computational Fluid Dynamics software. As a result, this tool helps users choose the most suitable GCV system design by comparing multiple GCV systems' design performances and allows them to save time, money, and effort.
Doctor of Philosophy

Wind power is a rapidly growing industry worldwide, both on- andoffshore. Most of the good locations onshore in continental Europeare in use today, which has prompted a move offshore in recentyears. Europe has by far the most offshore wind turbinesinstalled, mostly located in the North sea.The low hanging fruits are locations with relatively shallowwaters (up to 45-50 meters), a high and steady wind speed and isclose to grid connections onshore. Big parts of the North Sea aresuitable for this, but many places with good wind conditionsworldwide are too deep. The next step for the industry is to moveto these deeper waters, with the help of floating wind turbines.The first prototype floating turbines have been running for acouple of years, with even larger, albeit still pretty small, windfarms in the planning stage.This thesis looks on the possibility of building large floatingwind farms in the future, specifically in the eastern most part ofthe North Sea - Skagerrak. Several different factors andstakeholders have been mapped out and important factors such aswater depth, wind speed and seabed conditions considered to createfour different future scenarios. Each scenario has been evaluatedtechnically and Levelized Cost of Energy (LCOE) has beencalculated to be able to compare the different locations.Since the technology is very new and under development, theinitial costs are high. This gives the lower LCOE of 149 €/MWh.Many new developments are however expected in the years to come,which would lower the investment cost considerably, by up to 40%according to some sources. This would lower the LCOE to under 100€/MWh.It is however also found that these investments carry many otherpositive effects, such as developing a new carbon neutraltechnology in Scandinavia which could become a big exportworldwide. The social acceptance of bottom fixed foundationoffshore (close to shore) and onshore wind power is also falling,and this would also be a big plus for floating offshore wind as itcan be built so far offshore it can't be seen from land. BothSweden and Denmark have big power plants closing in the comingdecades, nuclear power in Sweden and coal fired power plants inDenmark. These need to be replaced either by import or by newcarbon neutral power production.

On March 13th, 2006, the Division of Electricity at Uppsala University deployed its first wave energy converter, L1, in the ocean southwest of Lysekil. L1 consisted of a buoy at the surface, connected through a line to a linear generator on the seabed. Since the deployment, continuous investigations of how L1 works in the waves have been conducted, and several additional wave energy converters have been deployed. This thesis is based on ten publications, which focus on different aspects of the interaction between wave, buoy, and generator. In order to evaluate different measurement systems, the motion of the buoy was measured optically and using accelerometers, and compared to measurements of the motion of the movable part of the generator - the translator. These measurements were found to correlate well. Simulations of buoy and translator motion were found to match the measured values. The variation of performance of L1 with changing water levels, wave heights, and spectral shapes was also investigated. Performance is here defined as the ratio of absorbed power to incoming power. It was found that the performance decreases for large wave heights. This is in accordance with the theoretical predictions, since the area for which the stator and the translator overlap decreases for large translator motions. Shifting water levels were predicted to have the same effect, but this could not be seen as clearly. The width of the wave energy spectrum has been proposed by some as a factor that also affects the performance of a wave energy converter, for a set wave height and period. Therefore the relation between performance and several different parameters for spectral width was investigated. It was found that some of the parameters were in fact correlated to performance, but that the correlation was not very strong. As a background on ocean measurements in wave energy, a thorough literature review was conducted. It turns out that the Lysekil project is one of quite few projects that have published descriptions of on-site wave energy measurements.

The master's thesis contains 97 pages, 29 tables, 33 figures and 43 sources of literature. The paper presents a study on increasing the efficiency of the power supply of remote offshore oil and gas facilities through the use of horizontal-axial tidal stream turbines. A general theoretical description of floating semi-submersible drilling rigs and a more detailed description of semi-submersible drilling unit 6000/200 type "Shelf" are presented. A theoretical description of various devices that transform the kinetic energy of water into electric power is also presented, and horizontal-axial tidal stream turbines are considered in more detail. The technical calculation for determining the parameters of turbines is carried out. The calculation was used for the case where one or several turbines are used. Economic analysis was carried out with different indicators, namely: the price of diesel fuel, the price of equipment, the load factor of hydro generators, the discount rate and the productivity of the drilling unit. An analysis of the reduction of carbon dioxide emissions was also carried out. Conclusions were presented on the effectiveness of the introduction of this method of energy supply.
Magisteruppsatsen innehåller 97 sidor, 29 tabeller, 33 figurer och 43 litteraturkällor. I papperet presenteras en studie om att effektiviteten i kraftförsörjningen av avlägsna offshore olje- och gasanläggningar ökar genom användning av horisontella axiella tidvattenströmsturbiner. En generell teoretisk beskrivning av flytande halvdämpbara borriggar och en mer detaljerad beskrivning av semi-submersible borrningsenhet 6000/200 typ "Hylla" presenteras. En teoretisk beskrivning av olika anordningar som omvandlar den kinetiska energin hos vatten till elkraft presenteras också, och horisontella axiella tidvattenströmsturbiner behandlas mer detaljerat. Den tekniska beräkningen för att bestämma parametrarna för turbiner utförs. Beräkningen användes för det fall där en eller flera turbiner används. Ekonomisk analys utfördes med olika indikatorer, nämligen: priset på dieselbränsle, priset på utrustning, belastningsfaktorn för hydrageneratorer, diskonteringsräntan och borrningens produktivitet. En analys av minskningen av koldioxidutsläpp gjordes också. Slutsatser presenterades om effektiviteten av införandet av denna metod för energiförsörjning.

The search for new solutions for the generation of energy is becoming more and more important for our future. Big arguments and disagreements on e.g. the questions of gas transport or the dependence on energy supplied by other countries raise demands on the development of new forms of alternative energy resources. Wave power is one of the main sources of renewable energy due to the high power density stored in ocean waves. Nevertheless, the dynamic forces of waves are so large that serious questions popped up on how to design a system which could work even in an unfavourable wave climate or could at least retain working capabilities after big storms without significant damages. This thesis studies the reliability of the mechanical parts of a linear direct driven permanent magnet generator. The results of offshore experiment where strain gauge sensors instrumented on the capsule and the inner framework structure are presented. Stress estimation analyses using strain gauges are carried out. A method for measuring forces and moments in the mechanical structure of the WEC is developed. Evaluation of the lateral force acting on the outer structure is a key factor for the design and construction of the WEC. A method for the measurement of the lateral force acting on the capsule has been developed. A study of the inclination angle between the Wave Energy Converter and the floating buoy has been carried out. The aim of this work is to contribute to the development of wave energy conversion system, and especially to the estimation of structural loads which are important for the survivability of the system under hard sea states. This work is a step that may influence future design of wave energy devices in terms of material aspect, survivability in a hard wave climate and cost-effective renewable energies.

My thesis presents comprehensive proposals for a system of ecological governance. The objective of governance would be to alleviate the threats to ecosystem health that anthropogenic interference gives rise to. I argue that it is necessary to reduce ecological stresses generated by human activities in view of the profound uncertainty over how these combine to undermine the functionality of ecosystems. I also argue that, from an ethical perspective, the healthy functioning of ecosystems should be regarded as being of supervening value for human well-being, and, accordingly, that it should be prioritised in decision making over economic and social goals. I propose legal and institutional structures that are designed both to reflect the supervening valuation of ecosystem health and to secure progressive reductions in ecological impacts. I consider how visions of an ecological transition might be formed through instituting a proactive policy-making process. I then go on to explore how these visions might be given practical effect. I argue that the state must take the lead in advancing ecological objectives and consider the capacities that it would need to possess and the relationships that it should have with other actors in governance. I propose a framework for ecological planning that would give legal structure to these relationships and lay down the goals and principles to be observed by participants in decision-making. In addition, I consider the potential for deliberative participatory institutions to promote the change in peoples’ values that would be necessary if an ecological transition is to enjoy public support. I conclude by examining the importance of an improved understanding of ecosystem behaviour for enhanced ecological protection, and consider the role of law in driving the production of the requisite information.

La raréfaction des sources de production conventionnelles et leurs émissions nocives ont favorisé l’essor notable de la production renouvelable, plus durable et mieux répartie géographiquement. Toutefois, son intégration au système électrique est problématique. En effet, la production renouvelable est peu prédictible et issue de sources majoritairement incontrôlables, ce qui compromet la stabilité du réseau, la viabilité économique des producteurs et rend nécessaire la définition de solutions adaptées pour leur participation au marché de l’électricité. Dans ce contexte, le projet scientifique Winpower propose de relier par un réseau à courant continu les ressources de plusieurs acteurs possédant respectivement des fermes éoliennes offshore (acteurs EnR) et des centrales de stockage de masse (acteurs CSM). Cette configuration impose aux acteurs d’assurer conjointement la gestion du réseau électrique.Nous supposons que les acteurs participent au marché comme une entité unique : cette hypothèse permet aux acteurs EnR de tirer profit de la flexibilité des ressources contrôlables pour minimiser le risque de pénalités sur le marché de l’électricité, aux acteurs CSM de valoriser leurs ressources auprès des acteurs EnR et/ou auprès du marché et à la coalition de faciliter la gestion des déséquilibres sur le réseau électrique, en agrégeant les ressources disponibles. Dans ce cadre, notre travail s’attaque à la problématique de la participation au marché EPEX SPOT Day-Ahead de la coalition comme une centrale électrique virtuelle ou CVPP (Cooperative Virtual Power Plant). Nous proposons une architecture de pilotage multi-acteurs basée sur les systèmes multi-agents (SMA) : elle permet d’allier les objectifs et contraintes locaux des acteurs et les objectifs globaux de la coalition.Nous formalisons alors l’agrégation et la planification de l’utilisation des ressources comme un processus décisionnel de Markov (MDP), un modèle formel adapté à la décision séquentielle en environnement incertain, pour déterminer la séquence d’actions sur les ressources contrôlables qui maximise l’espérance des revenus effectifs de la coalition. Toutefois, au moment de la planification des ressources de la coalition, l’état de la production renouvelable n’est pas connue et le MDP n’est pas résoluble en l’état : on parle de MDP partiellement observable (POMDP). Nous décomposons le POMDP en un MDP classique et un état d’information (la distribution de probabilités des erreurs de prévision de la production renouvelable) ; en extrayant cet état d’information de l’expression du POMDP, nous obtenons un MDP à état d’information (IS-MDP), pour la résolution duquel nous proposons une adaptation d’un algorithme de résolution classique des MDP, le Backwards Induction.Nous décrivons alors un cadre de simulation commun pour comparer dans les mêmes conditions nos propositions et quelques autres stratégies de participation au marché dont l’état de l’art dans la gestion des ressources renouvelables et contrôlables. Les résultats obtenus confortent l’hypothèse de la minimisation du risque associé à la production renouvelable, grâce à l’agrégation des ressources et confirment l’intérêt de la coopération des acteurs EnR et CSM dans leur participation au marché de l’électricité. Enfin, l’architecture proposée offre la possibilité de distribuer le processus de décision optimale entre les différents acteurs de la coalition : nous proposons quelques pistes de solution dans cette direction
Renewable Energy Sources (RES) has grown remarkably in last few decades. Compared to conventional energy sources, renewable generation is more available, sustainable and environment-friendly - for example, there is no greenhouse gases emission during the energy generation. However, while electrical network stability requires production and consumption equality and the electricity market constrains producers to contract future production a priori and respect their furniture commitments or pay substantial penalties, RES are mainly uncontrollable and their behavior is difficult to forecast accurately. De facto, they jeopardize the stability of the physical network and renewable producers competitiveness in the market. The Winpower project aims to design realistic, robust and stable control strategies for offshore networks connecting to the main electricity system renewable sources and controllable storage devices owned by different autonomous actors. Each actor must embed its own local physical device control strategy but a global network management mechanism, jointly decided between connected actors, should be designed as well.We assume a market participation of the actors as an unique entity (the coalition of actors connected by the Winpower network) allowing the coalition to facilitate the network management through resources aggregation, renewable producers to take advantage of controllable sources flexibility to handle market penalties risks, as well as storage devices owners to leverage their resources on the market and/or with the management of renewable imbalances. This work tackles the market participation of the coalition as a Cooperative Virtual Power Plant. For this purpose, we describe a multi-agent architecture trough the definition of intelligent agents managing and operating actors resources and the description of these agents interactions; it allows the alliance of local constraints and objectives and the global network management objective.We formalize the aggregation and planning of resources utilization as a Markov Decision Process (MDP), a formal model suited for sequential decision making in uncertain environments. Its aim is to define the sequence of actions which maximize expected actual incomes of the market participation, while decisions over controllable resources have uncertain outcomes. However, market participation decision is prior to the actual operation when renewable generation still is uncertain. Thus, the Markov Decision Process is intractable as its state in each decision time-slot is not fully observable. To solve such a Partially Observable MDP (POMDP), we decompose it into a classical MDP and an information state (a probability distribution over renewable generation errors). The Information State MDP (IS-MDP) obtained is solved with an adaptation of the Backwards Induction, a classical MDP resolution algorithm.Then, we describe a common simulation framework to compare our proposed methodology to some other strategies, including the state of the art in renewable generation market participation. Simulations results validate the resources aggregation strategy and confirm that cooperation is beneficial to renewable producers and storage devices owners when they participate in electricity market. The proposed architecture is designed to allow the distribution of the decision making between the coalition’s actors, through the implementation of a suitable coordination mechanism. We propose some distribution methodologies, to this end

Different wave power technologies are in development around the world in different stages of prototype testing. So far only a few devices have been deployed offshore at full scale for extended periods of time. Little data is published about how these different devices perform. This thesis presents results from experiments with the full-scale offshore wave energy converters at the Lysekil research site on the Swedish west coast. The theories, experiments, measurements, performance evaluations and developments of the submerged transmission in the direct driven permanent magnet linear generator are in focus. The reciprocating submerged transmission fulfills the purpose of transmitting the absorbed mechanical wave energy through the capsule wall into the generator, while preventing the seawater from entering the capsule and reducing the life time of the converter. A measuring system with seven laser triangulation sensors has been developed to measure small relative displacements between piston rod and seal housing in the submerged transmission with excellent accuracy for the purpose of evaluating both functional behavior and successive wear in-situ. A method for calculating relative tilt angles, azimuth angles, differential tilt angles, and successive wear in the submerged transmission has been developed. Additional sensors systems have been installed in the converter enabling correlation and a thorough investigation into the operating conditions of the transmission and the converter. The thesis presents unique results from the measurements. A data acquisition system transmits the signals from the converter on the seabed to an onshore measuring station. Results are presented in time-, frequency- and the time-frequency domain. The results have given important information for further development of the submerged transmission, which is important to the survivability of the system. The thesis describes the status of research, and is a step that may influence future designs of wave energy devices for reaching survivability and a cost-effective renewable energy system.

Published is a preprint version of the full text and should be combined by the errata.

The Lysekil Wave Power Project

The thesis concerns of the possibility by using alternative decentralized sources of energy. The first chapter describes current energy situation in the Czech Republic and consideration of future electrical energy consumption and the coverage by the renewable sources. Another part of this chapter describes each types of renewable energy with their advantages and disadvantages related to the Czech Republic. In the second chapter are introduced inputs which are appropriate for the plan of energetic system. The following theoretical chapter deals with each types of alternative energy sources using renewable source including the possibility of the installation and plan for the building. These alternative sources are sorted out by the way of using renewable sources of energy. The theoretical-practical fourth chapter concerns of the heating by the heat pump. For the detailed description was chosen the heat pump which is currently denote as appropriate alternative source of heat in household. With appropriate plan, which the thesis deals with, is this alternative source considered as proper investment. In the last chapter was assembled programme for creating models of energetic flux and calculation for the plan of heating by the heating pump air/water. This model is taken for concrete buildings related to exact outdoor temperature from previous years in concrete locality. In the end was realized validation of the software with the real measurement in concrete building.

Systemtemperaturer i värmesystem är en debatterad fråga i Sverige. Vid projektering av ett värmesystem har valet av systemtemperatur en avgörande roll för kostnaden av värmesystemet. Frågan vilka systemtemperaturer i värmesystemen som är det mest ekonomiska är viktig för att värmesystemet ska ha en fördel jämfört med konkurrenterna på marknaden. Historiskt sett har systemtemperaturerna i de svenska värmesystemen varit 80/60 medans idag är den vanligaste temperaturerna 55/45. Under 60-talet stod Östen Sandberg som förespråkare för ett nytänkande värmesystem kallat lågflödesystem (LF). Detta värmesystem använder sig av låga flöden i rörledningarna och stora temperaturskillnader på framledningen och returledningen. Förespråkare av dessa lågflödesystem hävdar att vid rätt användning kan en omjustering av det befintliga värmesystemet från ett högflödesystem (HF) till ett lågflödesystem drastigt reducera energiförbrukningen för fastigheten och samtidigt uppnå acceptabla inomhusförhållanden. Hade ett LFsystem kunnat konkurrera mot ett HFsystem ekonomiskt? För att undersöka detta kommer ett 55/45-HFsystem att användas som ursprungsfall vid jämförelser mellan HFsystem och LFsystem med olika systemtemperaturer för att utreda om ett 55/45-HFsystem är det mest ekonomiska värmesystemet. Studien visar många fördelar med 55/45-HFsystemet. Ett 55/45-HFsystem har relativt låga investeringskostnader vid projekteringen i jämförelse med de andra värmesystemen. En annan fördel är att detta värmesystem är kompatibelt med både fjärrvärme samt bergvärme vilket gör detta system passande som ett standardiserat värmesystem. Det mest ekonomiska värmesystemet är ett 80/60-HFsystem, vilket har lägre investeringskostnader för både radiatorer samt rörkostnader. Förespråkare av LFsystem hävdar att de reducerade flödena medför reducerade elkostnader för cirkulationspumpen vilket i längden gör LFsystemet energisnålare. Denna studie visar att de reducerade flödena och dess påverkan av energiförbrukningen hos cirkulationspumpen är förhållandevis så låga i jämförelse med de totala energiförbrukningen hos värmesystemet att den möjliga vinsten är försumbar. Däremot kan de reducerade flödena minska risken för en snedfördelad värmefördelning i fastigheten. LFsystemens stora nackdel är ökade investeringskostnader jämfört med HFsystemen.
The choice of temperatures in heating systems has long been a question for debate in Sweden. For the design engineer, the choice of system temperatures in a heating system has a decisive impact on the cost and in order to stay competitive on the market it is crucial to design the heating system as cost effective as possible. Historically the system temperature in Swedish heating systems has been 80/60 but today we see that the most common temperatures are 55/45. During the 1960´s Östen Sandberg became the leading advocate for a new type of heating system using a low flow principle (LF) for heat distribution. The LF principle requires a larger temperatur difference between the supply and return temperatures for the adequate heating. Advocates of the LF principle claims that large energy savings are possible if an exsisting high flow heating system (HF) undergoes an adjustment to a LF heating system. The question is how accurate is this claim? This article shows many advantages with the nowadays common 55/45-HFsystem. A 55/45-HFsystem has relatively low investment costs in comparison with other types of heating systems. Another advantage is the fact that the 55/45-HFsystem is compatible with both district heating and geothermal heat pump heating systems which makes this radiator system suitable as a standardized system. The most economical radiator system is the 80/60-HFsystem, which has a lower investment cost for both radiators and piping in comparison with a 55/45-HFsystem. The claim that LFsystems and the associated LF principle could result in a reduced energy cost for the heating system was not supported. This article shows that the energy savings that comes from the LF principle is negligible in comparison with the heating systems total energy cost. The LF principle could however reduce the risk of an uneven heating distribution in the building due to a more unpredictable regulation of the flow through the radiators. LFsystem disadvantage is an general overall larger investment cost in comparison with a HFsystem.

En el país es poco común el uso de energías renovables, por ello es importante que se difundan las tecnologías asociadas al uso de este tipo de recursos. La energía geotérmica superficial es un recurso que se puede aprovechar prácticamente en toda la corteza terrestre, no proporciona una cantidad de energía elevada, pero si tiene aplicaciones que reducen la producción de CO2 (por sistemas de calefacción) y el consumo de energía. En la investigación se analizan los sistemas geotérmicos de baja entalpia, específicamente las cimentaciones termoactivas, las cuales consisten en incorporar el intercambiador de calor en la estructura de la cimentación, esto aunado a la bomba de calor y el sistema de distribución constituye un uso importante de la energía geotérmica somera en los sistemas de calefacción de edificaciones. Para desarrollar las cimentaciones termoactivas es necesario realizar estudios previos tales como, estudio de características geotécnicas y térmicas del suelo, hidrogeología y geología.
The use of renewable energies is rare in the country, so it is important that the technologies associated with the use of this type of resources be disseminated. Surface geothermal energy is a resource that can be used practically throughout the earth's crust, it does not provide a high amount of energy but it does have applications that reduce CO2 production (by heating systems) and energy consumption. The research analyzes low enthalpy geothermal systems, specifically thermoactive foundations, which consist of incorporating the heat exchanger in the foundation structure, this together with the heat pump and the distribution system constitutes an important use of shallow geothermal energy in building heating systems. To develop thermoactive foundations it is necessary to carry out previous studies such as a study of the geotechnical and thermal characteristics of the soil, hydrogeology and geology.
Tesis

Le développement de Geps Techno est basé sur un concept innovant de structure flottante destinée à produire de l'énergie électrique à partir de plusieurs sources d'énergies marines renouvelables dont la source houlomotrice. Le système houlomoteur développé par Geps Techno repose sur la mise en circulation d'eau et la création d'un tourbillon en son sein. En profitant du phénomène de carène liquide, le concept est également déclinable en un système de stabilisation de navire ou de toute autre plateforme flottante. L'objectif à court terme de la société est le développement de cette technologie permettant la stabilisation et la récupération de l'énergie des vagues et pour lequel il reste des verrous technologiques à lever afin d'arriver à la viabilité et la rentabilité du système. Pour cela, Geps Techno a lancé en octobre 2015 le projet IHES (Integrated Harvesting Energy System) qui consiste à construire un démonstrateur de son concept de plateforme houlomotrice. Le projet IHES est un des projets de la feuille de route du plan "Navires écologiques" de la Nouvelle France Industrielle. Il est soutenu par Bpifrance dans le cadre du programme d'Investissements d'Avenir - Projets Industriels d'Avenir. Afin de maîtriser les objectifs de stabilisation et de récupération d'énergie, Geps Techno étudie les volets technologiques nécessaires permettant de passer de l'énergie disponible au niveau des vagues jusqu'à celle disponible au niveau de la turbine du houlomoteur. Les travaux de thèse soutenus par Fourestier en mai 2017 portaient sur un premier volet "Définition et contrôle des écoulements internes au système houlomoteur". A l'aide d'une modélisation des fluides numériques, ces derniers ont abouti à des modèles opérationnels caractérisant les écoulements internes. La présente thèse Cifre s'inscrit dans la continuité des travaux de Fourestier et traite d'un second volet "Modélisation du système couplé plateforme / houlomoteur". L'ensemble de ces travaux devra aboutir à un code de calcul opérationnel et corrélé à des résultats expérimentaux permettant d'étudier l'écoulement interne et le comportement du flotteur soumis à la houle
Geps Techno's development is based on an innovative concept of a floating structure intended to produce electrical energy from several renewable marine energy sources, including wave power. The wave power system developed by Geps Techno is based on circulating water and creating a vortex within it. By taking advantage of the liquid hull phenomenon, the concept can also be used as a stabilization system for a ship or any other floating platform. The short-term objective of the company is the development of this technology allowing the stabilization and recovery of wave energy and for which there remain technological obstacles to be removed in order to achieve the viability and profitability of the system. To do this, in October 2015 Geps Techno launched the IHES (Integrated Harvesting Energy System) project, which consists of building a demonstrator of its wave power platform concept. The IHES project is one of the projects of the roadmap of the "Ecological ships" plan of New Industrial France. It is supported by Bpifrance within the framework of the Investments for the Future - Industrial Projects for the Future program. In order to master the objectives of stabilization and energy recovery, Geps Techno is studying the technological aspects necessary to switch from the energy available at wave level to that available at the wave turbine turbine. The Ph.D. thesis work supported by Fourestier in May 2017 focused on a first part "Definition and control of internal flows in the wave power system". Using CFD modeling, the latter resulted in operational models characterizing internal flows. This Cifre Ph.D. thesis follows on from Fourestier's work and deals with a second part "Modeling of the coupled platform / wave power system". All of this work should lead to an operational computer code correlated with experimental results making it possible to study the internal flow and the behavior of the float subjected to swell

Mathematical modeling and simulations of a submerged renewable storage system integrated to a wind farm, chosen based on the geographical and wind conditions at the Baltic Sea, gives insight on the feasibility of the submerged renewable storage and an approximation of the payback period and profits that could be generated. Genetic Algorithms were used to obtain the optimal number of spheres for a certain depth, based on 2 objective functions I.e. Minimum Life Cycle Cost (LCC) and maximum reduction in wind curtailment. The new arrangement concept shows that the Initial Capital Cost (ICC) could be decreased by 25% to 60% depending upon the number of sphere employed. Based on the inputs considered in the study, the results prove that the submerged renewable storage system would be feasible, and the profits ranging from 15 Million Euro to 29 Million Euro can be achieved at the chosen location, towards the Swedish side of the Baltic sea. Although, in a real life scenario it is assumed that only up to half of the profits obtained in the results would be achievable. The results also show that, the Pump/Turbine with a high turbine efficiency and lower pump efficiency, generated better profits, compared to a Pump/Turbine running with a higher pump efficiency and lower turbine efficiency. An attempt to increase the round-trip efficiency by adding a multi stage submersible pump, resulted in additional ICC and LCC, which saw a decrease in profits.

2013/2014
La domanda alla base di questa ricerca è stata se il metodo della gravimetria satellitare possa essere utilizzato per seguire le unità geologiche anche in luoghi difficilmente accessibili. L’obiettivo di questa ricerca è di verificare se le missioni satellitari di nuova generazione permettano di identificare la più grande delle province ignee della Terra (Bertrand et al., 2013), nota come CAMP (Central Atlantic Magmatic Province) in Africa nord-occidentale. Oltre alle motivazioni scientifiche, una possibile applicazione è l’esplorazione di risorse minerarie e lo sfruttamento di energia geotermica. Tale provincia ignea è una LIP (Large Igneous Province) che si estende in Nord e Sud America, Atlantico, Europa ed Africa (istituita in Marzoli et al. 1999). Essa si è sviluppata a seguito della frammentazione del super-continente Pangea al limite Triassico-Giurassico, ca. 200 Ma fa. A causa probabilmente del riscaldamento globale del mantello e/o dalla convezione dello stesso innescata da dislivelli di blocchi litosferici, dai dicchi-sorgente si produssero i cosiddetti basalti da flusso e si verificò un intenso vulcanismo con imponenti colate laviche tali da suggerire a taluni ricercatori che gli elementi volatili presenti nel magma abbiano contribuito ad aumentare i gas serra con conseguenze nel clima globale e nelle estinzioni di massa. I depositi in esame sono costituiti da lave, tholeiti continentali, doleriti, basalti e gabbri. Ciò che rimane di questa attività vulcanica sono dicchi singoli o in sciami, batoliti, sill, colate laviche e plateau basaltici (nei fondali oceanici). L’Africa nord-occidentale è costituita principalmente da un cratone composto da rocce molto antiche dell’Archeano (3000-2500 Ma). Esso emerge a nord nello scudo Reguibat e, a sud, la dorsale dell’Uomo o del Leone (Lucazeau et al., 1991). Il cratone è circondato dalle zone di geosutura (greenstone e cinture mobili) associate al cosiddetto evento termo-tettonico Pan-Africano, verificatosi ca. 650 Ma fa con l’assemblaggio del continente africano da blocchi crostali più piccoli. Nelle Mauritanidi affiora il basamento ercinico (ca. 350 Ma) mentre negli Atlas e nelle Magrebidi prevalgono rocce più recenti connesse all’orogenesi alpina (0-150 Ma). Al centro del cratone si trova il bacino paleozoico Taoudenni che riempie una vasta area depressa. Tutto il territorio in esame è caratterizzato da una forte presenza di rocce metamorfiche dense e magmatiche di ogni età, con presenza di più di un “punto caldo” che potrebbe essere definito un terreno igneo (Bryan et al. (2008) con più LIP spesso sovrapposte o limitrofe. Mediamente, tutte queste rocce magmatiche e metamorfiche hanno una densità di 3000 kg/m3 (Kröner, 1977 ), maggiore di quella della crosta standard e dei sedimenti. Particolare attenzione è stata dedicata ad un lineamento tettonico noto come Pelusium Megashare System (PMS) che attraversa tutta l’Africa nord-occidentale (Neev et al., 1982) chiaramente visibile in tutte le immagini satellitari di Google Earth ma che è riportato solo in pochissime pubblicazioni. Per la prima volta in questa tesi si ipotizza un collegamento tra la CAMP e PMS. La gravimetria satellitare consente di rilevare variazioni di densità nella crosta terrestre. Ove vi sono rocce più dense, il segnale rilevato (detto anomalia gravimetrica) è positivo e viceversa. La gravimetria da satellite si è rivelata un valido strumento per identificare le aree con surplus di massa. La risposta all’interrogativo iniziale è dunque affermativa anche se, da quanto esposto, risulta difficile o impossibile associare ad un certo segnale positivo una data LIP. L’elaborazione dei segnali è avvenuta partendo dai dati del satellite GOCE (ultima generazione, a un’orbita di 250 km ma già ammarato) e GRACE (obsoleto ma tuttora in orbita a ca. 450 km). I dati utilizzati sono dei modelli del campo di gravità terrestre che contengono i coefficienti di Stokes per lo sviluppo in armoniche sferiche del potenziale. I modelli utilizzati sono l’EGM2008 (comprendente anche dati di terra, con risoluzione massima 10 km se sviluppato al massimo ordine di 2159) e GOCO TIM R4 (con una risoluzione massima di 80 km, la migliore mai ottenuta da dati satellitari globali). Il modello EGM2008 è stato sviluppato fino all’ordine e grado 720 per eliminare dati spuri (Pavlis, 2012) e, in tal modo, ha permesso di raggiungere una risoluzione di ca. 27 km se si considera metà lunghezza d’onda. Dopo il controllo della qualità dei dati, essi sono stati elaborati nel seguente modo, come esposto nei capitoli 2, 3 e 4. Ai dati grezzi sono state applicate tre riduzioni per sottrarre gli effetti di gravità indesiderati che mascherano il segnale cercato più debole. È stato sottratto l’effetto di gravità della topografia, dei sedimenti e dell’interfaccia crosta-mantello (ICM). Partendo dall’anomalia “in aria libera” (FA), è stata quindi ottenuta l’anomalia di Bouguer (BA) e la BA corretta per i sedimenti. Poi, calcolata la Moho (ICM) isostatica, si è prodotto il residuo isostatico corretto per i sedimenti. I campi elaborati sono la gravità gz (espressa in milli Gal, mGal) ed il gradiente Tzz (misurato in Eötvös, E). Sono state usate le risoluzioni di 0.5° e di 0.05°, computati ad una quota di 4000 m s.l. m perché maggiore del più altro rilievo montuoso dell’area. Dopo aver modellato dei casi a geometria semplice (cap. 6) si è passati alla modellizzazione di tre casi reali. I tre siti scelti per l’approfondimento sono: Tindouf (Algeria), Taoudenni (Mali), Timbuktu (Mali). Nel bacino di Tindouf un sill doleritico CAMP è annesso al suo probabile dicco-sorgente reso evidente dalla gravimetria che identifica bene anche una vicina miniera di Ferro. Nel bacino Taoudenni, le due anomalie principali suggeriscono la presenza di cumuliti magmatici spessi una dozzina di chilometri e connessi con la superficie attraverso dicchi obliqui. Il sito presso Timbuktu è trattato nel dettaglio perché al di sotto del vicino lago Faguibine è stata rivelata un’intrusione magmatica lunga ca. 250 km. In superficie vi sono evidenze di magmatismo (per es. fumarole) tali da preoccupare le popolazioni locali (El Abbass et al., 1993). Tra i risultati inaspettati, si ricorda il forte segnale gravimetrico generato dalle peridotiti in Marocco ed un’importante anomalia (80 mGal) nel Grand Erg Occidental (Algeria) al di sotto del Sahara che sembrerebbe essere causata da un corpo denso lungo ca. 600 km.
The question behind this research was whether the method of satellite gravimetry can be used to follow the geological units even in inaccessible places. The goal of this research is to verify if the new generation of satellite missions serve to identify the largest of the Earth's igneous provinces (Bertrand et al., 2013), known as CAMP (Central Atlantic Magmatic Province) in Northwest Africa . Besides the scientific reasons, a possible application is the exploration of mineral resources and the exploitation of geothermal energy. This is an igneous province (LIP Large Igneous Provinces) that extends throughout North and South America, the Atlantic Ocean, Europe and Africa (established in Marzoli et al. 1999). It developed as a result of the fragmentation of the super-continent Pangea at Triassic-Jurassic limit, ca. 200 My ago. Probably because of mantel global warming and/or its convection triggered by differences in thickness of lithospheric blocks, from source-dikes were produced the so-called continental flow basalts (CFB) and there was an intense volcanism with massive lava flows that this would suggest to certain researchers volatile elements present in the magma have contributed to increasing greenhouse gases with consequences in the global climate and mass extinctions. The deposits in question consist of lavas, tholeites continental dolerites, basalts and gabbros. What remains of this volcanic activity are individual dykes or in swarms, batholiths, sills, lava flows and basaltic plateau (in the ocean). The north-western Africa consists mainly of a craton made of most ancient rocks dell'Archean (3000-2500 Ma). It emerges in the shield Reguibat north and on the south, the Man or the Lion shield (Lucazeau et al., 1991). The craton is surrounded by areas of geosutura (greenstone belts and mobile belts) associated with the so-called Pan-African thermo-tectonic event, occurred ca. 650 Ma ago with the assembly of the African continent by smaller crustal blocks. Mauritanides emerges in the Hercynian basement (ca. 350 Ma) while in the Atlas and Magrebides prevail younger rocks (Alpine orogenesis, 0-150 Ma). At the center of the craton is the Paleozoic basin Taoudenni that fills a large area depressed. All the territory concerned is characterized by a strong presence of dense magmatic and metamorphic rocks of all ages, with the presence of more than a "hot spot" that could be called “igneous terrane” (Bryan et al. (2008) with more LIPs overlapping or adjacent. On average, these igneous and metamorphic rocks have a density of 3000 kg / m3 (Kröner, 1977), greater than that of the standard crust and the sediments. Particular attention was dedicated to a tectonic lineament known as Pelusium Megashare System (PMS) that runs through the north-western Africa (Neev et al., 1982) clearly visible in all the satellite images of Google Earth but is reported only in very few publications. For the first time this thesis suggests a link between CAMP and PMS. Satellite gravimetry can detect density variations in the Earth's crust. Where there are rocks denser, the detected signal (called gravity anomaly) is positive and vice versa. The gravimetry by satellite has proved a valuable tool to identify areas with surplus Mass. The initial response to the question is therefore affirmative although, from the above, it is difficult or impossible to associate a positive signal a date LIP. Signals processing occurred from the data of the GOCE satellite (last generation, in an orbit of 250 km, mission already finished) and GRACE (obsolete but still in orbit at ca. 450 km). The data used are the models of the Earth's gravity field containing the coefficients of Stokes for the development of potential in spherical harmonics. The models used are the EGM2008 (also including land data, with a maximum resolution 10 km if developed to the maximum order of 2159) and TIM GOCO R4 (with a maximum resolution of 80 km, the best ever obtained by global satellite data). The model EGM2008 has been developed up to the order and degree 720 to remove spurious data (Pavlis, 2012) and, thus, allowed to reach a resolution of ca. 27 km considering half wavelength. After quality control of the data, they were processed in the following flowchart, as discussed in Chapters 2, 3 and 4. Raw data were processed applying three reductions to subtract the effects of gravity that mask the signal. It was reduced by the effect of gravity of the topography, sediment and crust-mantle interface (CMI). Starting by the anomaly "free air" (FA), was thus obtained the Bouguer anomaly (BA) and BA correct for sediment. Then, once calculated the isostatic Moho (CMI), has produced the sediment-corrected-isostatic residual. The fields processed are gravity gz (in milli Gal, mGal) and gradient tzz (measured in Eötvös, E). It has been used the resolutions of 0.5 ° and 0.05 °, computed at an altitude of 4000 m a.s.l., higher of mountains in the area. After mng cases with simple geometry (ch. 6) we moved to the modeling of three real case histories. The three sites chosen for the study are: Tindouf (Algeria), Taoudenni (Mali), Timbuktu (Mali). In the basin of Tindouf a CAMP doleritic sill is attached to its likely source source-dyke evident by gravimetry that identifies well a nearby mine of Iron. In the Taoudenni basin, the two main anomalies suggest the presence of magmatic cumulites a dozen kilometers thick and connected with the surface through oblique dikes. The site at Timbuktu is discussed in detail because in the nearby lake Faguibine was revealed a magmatic intrusion long ca. 250 km. On the surface there is evidence of magmatism (e.g. Fumaroles) such that worry local populations (El Abbass et al., 1993) .Among the unexpected results, please note the strong signal generated by gravimetric peridotites in Morocco and a major anomaly (80 mGal) in the Grand Erg Occidental (Algeria) below the Sahara that would seem to be caused by a dense body ca. 600 km long.
XXVI Ciclo
1972

碩士
國立臺北科技大學
能源與冷凍空調工程系碩士班
97
Due to the limited indigenous resources in Taiwan, most energy resource are relied and imported from other countries. In addition, people are aware of carbon dioxide reducing and also the importance of clean renewable energy. With the inefficiency of the traditional fossil fuel systems and the pollutant emission, we need to look for any clean energetic system. Traditional refrigeration and air-conditioning are vapor compression refrigeration cycle that not only causes an enormous amount of electrical energy but leads to ozone-depleting and the global warming by releasing synthetic refrigerant substances. The reason why we need to seek the alternative refrigerant or even other energy lies in driven refrigeration and air-conditioning system. Because of the abundance of natural geothermal resources in Taiwan, the thesis presents mainly on（1）Using low temperature geothermal energy to drive LiBr/H2O absorption system and analyze the performances of it. Furthermore, this thesis compares primary energy ratio (PER) and carbon dioxide emission of the various energy-driven absorption systems.（2）Using high temperature geothermal energy to drive district cogeneration system that provides thermal energy, electricity and cooling energy to the residence of the region. Analyze the geothermal energy cogeneration system with thermodynamic first and second laws, showing the analysis of the energy losses and efficiency of each subsystem and entire cogeneration system. Therefore, the results of this research can be used to improve the further systematical performance and achieve optimum of district geothermal energy cogeneration system.

碩士
國立臺灣大學
機械工程學研究所
105
Traditional air-conditioning cooling systems usually use cooling tower to dissipate condense heat into outdoor air. However, the outdoor temperature and humidity, which vary over time, limit the cooling performance of cooling tower. Furthermore, the use of cooling tower has many disadvantages such as noise, vibration, and also providing a proper environment for bacteria breeding. Therefore, the aim of this thesis is to replace cooling tower system with a new cooling system—the shallow geothermal cooling system. This new cooling system dissipates condense heat into the shallow ground. Because of having a relatively small temperature variation, the shallow ground can be a stable heat sink for air-conditioning cooling.In this study, we used two types of shallow geothermal cooling system: groundwater borehole and raft foundation water. According to the experiment results, the groundwater cooling system could stably cool the condenser and reached thermal equilibrium state, but the temperature of raft foundation water was continuously rising during operation. Therefore, the groundwater cooling system can be a proper alternative for replacing cooling tower system. On the other hands, the raft foundation water cooling system could be another choice through optimized operating method.

碩士
國立臺灣大學
機械工程學研究所
107
The earth air heat exchanger (EAHE) is a low-energy ventilation technique using the stable temperature of earth. In the past decade, many experimental studies deal with the performance evaluation of EAHE system worldwide; however, in Taiwan these kinds of researches are still uncommon. This research focus on the performance of soil-based EAHE and water-based EAHE using numerical methods. Soil-based EAHE includes 4 PVC air pipes each with 52.95m in length, 0.15m in diameter and buried 4.7m beneath ground surface. Its arranged ventilation is 3150 CMH, working 9 a.m. to 9 p.m. Water-based EAHE consists of 3 PVC air pipes each with 75m in length, 0.15m in diameter and buried 9.5m underground. Its arranged ventilation is 990 CMH, working 9 a.m. to 9 p.m. This research uses ANSYS Fluent for simulating various system status over time. Initial conditions are ventilation, seasonal introduced air temperatures and seasonal introduced air humidity. After simulation, EAHE system’s seasonal outlet temperature, outlet humidity, heat transfer rates, temperature distributions in raft foundation water and soil of 2 meters around air pipes can be generated. Through heat transfer rates, seasonal energy saving efficiency can be recognized, such as cooling load in summer and heating load in winter, as well as the percentage of latent heat transfer rates through the examination of humidity difference. This analysis benefits future applications for selecting suitable areas to adjust and improve the energy saving efficiency of EAHE systems. By analyzing raft foundation water temperature distribution, the range of water affected by EAHE and its most efficient operating period can be recognized to maintain stable water temperature and its heat transfer rate for preserving EAHE’s energy saving efficiency. Through analyzing surrounding soil temperature distribution, the range and extent of soil affected by EAHE can be realized. Selecting suitable soil allows soil to maintain its stable temperature, heat transfer rates and its self-recovering ability to sustain EAHE’s energy saving efficiency. From simulation results, the influence of pipe materials, such as stainless steel, copper, aluminum and PVC on the performance of EAHE can be known, thus suitable pipe materials can be determined. From temperature distribution of introduced air within air pipes, effective length for regulating can be discerned for future applications. Besides, although increasing airflow velocities promotes heat transfer rates, heat exchange time between introduced air and air pipes also decreases. Therefore, through simulation, the optimal airflow velocities are discovered. Airflow velocities of 2m/s, 5 m/s, 9 m/s and 12 m/s are considered in this research. Finally, the influence of water temperature 21℃, 23℃, 25℃ and water storage of full, 0.75-full, half-full on the performance of EAHE and recovery during shut down period is discussed. By the simulation with mentioned settings, systems’ seasonal air regulation, energy saving efficiency, efficient operating period, influence of pipe materials, effective length, affected range of surrounding soil and water, suitable soil types, appropriate airflow velocities, the influence of water temperature and water storage can be acknowledged.

Geothermal energy is the energy naturally present inside the earth crust. When a large volume of hot water and steam is trapped in subsurface porous and permeable rock structure and a convective circulating current is set up, it forms a geothermal reservoir. A geothermal system can be defined as - convective water in the upper crust of earth, which transfers heat from a heat source (in the reservoir) to a heat sink, usually the free surface. A geothermal system is made up of three main elements: a heat source, a reservoir and a fluid, which is the carrier that transfers the heat. As an alternative source of energy geothermal energy has been under attention of the researchers for quite some time. The reason behind this is the existence of several benefits like clean and renewable source of energy which has considerable environmental advantage, with no chemical pollutants or wastes are generated due to geothermal emissions, and the reliability of the power resource. Hence research has been directed in several directions like exploration of geothermal resources, modeling the characteristics of different types of geothermal reservoirs and technologies to extract energy from them. The target of these models has been the prediction of the production of the hot water and steam and thus the estimation of the electricity generating potential of a geothermal reservoir in future years. In a geothermal power plant reinjection of the heat depleted water extracted from the geothermal reservoir has been a common practice for quite some time. This started for safe wastewater disposal and later on the technology was employed to obtain higher efficiency of heat and energy extraction. In most of the cases a very small fraction of the thermal energy present in the reservoir can be recovered without the reinjection of geothermal fluid. Also maintaining the reservoir pressure is essential which gradually reduces due to continuous extraction of reservoir fluid without reinjection, especially for reservoirs with low permeabilities. Although reinjection of cold-water has several benefits, the possibility of premature breakthrough of the cold-water front, from injection well zone to production well zone, reduces the efficiency of the reservoir operation drastically. Hence for maintaining the reservoir efficiency and longer life of the reservoir, the injectionproduction well scheme is to be properly designed and injection and extraction rates are to be properly fixed. Modeling of flow and heat transport in a geothermal reservoir due to reinjection of coldwater has been attempted by several researchers analytically, numerically and experimentally. The analytical models which exist in this field deal mostly with a single injection well model injecting cold-water into a confined homogeneous porous-fractured geothermal reservoir. Often the thermal conductivity is neglected in the analytical study considering it to be negligible which is not always so, as proved in this study. Moreover heterogeneity in the reservoir is also a major factor which has not been considered in any such analytical study. In the field of numerical modeling there also exists a need of a general coupled three-dimensional thermo-hydrogeological model including all the modes of heat transport (advection and conduction), the heat loss to the confining rocks, the regional groundwater flow and the geothermal gradient. No study existing so far reported such a numerical model including those mentioned above. The present study is concerned about modeling the non-isothermal flow and heat transport in a geothermal reservoir due to reinjection of heat depleted water into a geothermal reservoir. Analytical and numerical models are developed here for the transient temperature distributions and advancement of the thermal front in a geothermal reservoir which is generated due to the cold-water injection. First homogeneous geothermal aquifers are considered and later heterogeneities of different kinds are brought into picture. Threedimensional numerical models are developed using a software code DuMux which solves flow and heat transport problems in porous media and can handle both single and multiphase flows. The results derived by the numerical models have been validated using the results from the analytical models derived in this study. Chapter 1 of the thesis gives a brief introduction about different types of geothermal reservoirs, followed by discussion on the governing differential equations, the conceptual model of a geothermal reservoir system, the efficiency of geothermal reservoirs, the modeling and simulation concepts (models construction, boundary conditions, model calibration etc.). Some problems related with geothermal reservoirs and geothermal power is also discussed. The scenario of India in the context having a huge geothermal power potential is described and different potential geothermal sites have been pointed out. In Chapter 2, the concept of reinjection of the heat depleted (cold) water into the geothermal reservoir is introduced. Starting with a brief history of the geothermal reinjection, the chapter describes the purpose and the need of reinjection of geothermal fluid giving examples of different geothermal fields over the world where reinjection has been in practice and benefitted by that. The chapter further discusses on the problems and obstacles faced by the geothermal projects resulting from the geothermal reinjection, most important of which is the thermal-breakthrough and cooling of production wells. Lastly the problem of this thesis is discussed which is to model the transient temperature distribution and the movement of the cold-water thermal front generated due to the reinjection. The need of this modeling is elaborated which represents the motivation of taking up the problem of the thesis. Chapter 3 describes an analytical model developed for the transient temperature in a porous geothermal reservoir due to injection of cold-water. The reservoir is composed of a confined aquifer, sandwiched between rocks of different thermo-geological properties. The heat transport processes considered are advection, longitudinal conduction in the geothermal aquifer, and the conductive heat transfer to the underlying and overlying rocks of different geological properties. The one-dimensional heat transfer equation has been solved using the Laplace transform with the assumption of constant density and thermal properties of both rock and fluid. Two simple solutions are derived afterwards, first neglecting the longitudinal conductive heat transport and then heat transport to confining rocks. The analytical solutions represent the transient temperature distribution in the geothermal aquifer and the confining rocks and model the movement of the cold-water thermal front in them. The results show that the heat transport to the confining rocks plays an influential role in the transient heat transport here. The influence of some parameters, e.g. the volumetric injection rate, the longitudinal thermal conductivity and the porosity of the porous media, on the transient heat transport phenomenon is judged by observing the variation of the transient temperature distribution with different values of the parameters. The effects of injection rate and thermal conductivity have been found to be high on the results. Chapter 4 represents another analytical model for transient temperature distribution in a heterogeneous geothermal reservoir underlain and overlain by impermeable rocks due to injection of cold-water. The heterogeneity of the porous medium is expressed by the spatial variation of the flow velocity and the longitudinal effective thermal conductivity of the medium. Simpler solutions are also derived afterwards first neglecting the longitudinal conduction, then the heat loss to the confining rocks depending on the situation where the contribution of them to the transient heat transport phenomenon in the porous media is negligible. Solution for a homogeneous aquifer with constant values of the rock and fluid parameters is also derived with an aim to compare the results with that of the heterogeneous one. The effect of heat loss to the confining rocks in this case is also determined and the influence of some of the parameters involved, on the transient heat transport phenomenon is assessed by observing the variation of the results with different magnitudes of those parameters. Results show that the heterogeneity plays a major role in controlling the cold-water thermal front movement. The transient temperature distribution in the geothermal reservoir depends on the type of heterogeneity. The heat loss to the confining rocks of the geothermal aquifer also has influence on the heat transport phenomenon. In Chapter 5 another analytical model is derived for a heterogeneous reservoir where the heterogeneous geothermal aquifer considered is a confined aquifer consisted of homogeneous layers of finite length and overlain and underlain by impermeable rock media. All the different layers in the aquifer and the overlying and underlying rocks are of different thermo-hydrogeological properties. Results show that the advancement of the cold-water thermal front is highly influenced by the layered heterogeneity of the aquifer. As the cold-water thermal front encounters layers of different thermo-hydrogeological properties the movement of it changes accordingly. The analytical solution derived here has been compared with a numerical model developed by the multiphysics software code COMSOL which shows excellent agreement with each other. Lastly it is shown that approximation of the properties of a geothermal aquifer by taking mean of the properties of all the layers present will lead to erroneous estimation of the temperature distribution. Chapter 6 represents a coupled three-dimensional thermo-hydrogeological numerical model for transient temperature distribution in a confined porous geothermal aquifer due to cold-water injection. This 3D numerical model is developed for solving more practical problems which eliminate the assumptions taken into account in analytical models. The numerical modeling is performed using a software code DuMux as mentioned before. Besides modeling the three-dimensional transient temperature distribution in the model domain, the chapter investigates the regional groundwater flow has been found to be a very important parameter to consider. The movement of the thermal front accelerates or decelerates depending on the direction of the flow. Influence of a few parameters involved in the study on the transient heat transport phenomenon in the geothermal reservoir domain, namely the injection rate, the permeability of the confining rocks and the thermal conductivity of the geothermal aquifer is also evaluated in this chapter. The models have been validated using analytical solutions derived in this thesis. The results are in very good agreement with each other. In Chapter 7 the main conclusions drawn from the study have been enlisted and the scope of further research is also pointed out.

博士
國立臺灣大學
機械工程學研究所
100
The purpose of this dissertation is to investigate the optimal design of geothermal heat pump. This dissertation experimentally and mathematically investigates the performance of the geothermal heat pump system which consists of a heat pump and a borehole heat exchanger. Furthermore, optimal method for analyzing the cost influences of the life cycle of the system were developed based on different operation strategies and the capacity of the equipment (combination of heat pumps and borehole heat exchangers). For the performance of the heat pump system, the comparison between the mathematical modeling and the experimental approaches are identical. The relation of correlation R2 is about 0.9867. On the contrary, the capability of the borehole heat exchangers was investigated. The variation of the water temperature inside the cylindrical tube and the outlet water temperature in the spiral pipe were solved by using the thermal resistance method. The result shows that the error of the temperature for spiral pipe outlet and water temperature inside the cylindrical tube with compare to the mathematical model is 0.31% and 3.12%. While in the optimum design, it compares the performances of four updating rules of the particle swarm optimization (PSO) through applying five mathematic problems. The linear-decayed inertia weight method is favorable for this study because stability of solutions can be obtained. This dissertation also developed a solution for the discrete problem of the on-off system in the water pump and heat pump by using PSO with Roulette Wheel Method. Finally a case study was conducted. The geothermal heat pump system was developed in a factory in order to obtain the optimization. The primary parameters include the turn-off states of heat pump and water pump, the heat pump capacity, the UA of heat exchanger, the initial cold and heat water temperature and the capacity of cold and heat tank. The results indicated that the cost of life cycle of the geothermal heat pump system can be reduced by NT 1,446,552, the ratio of energy saving is 56.23%. The energy consumption decrement is 965,756 kJ/day, the ratio of energy saving is 46.50% and the reduction of CO2 emissions is 167 kg/day for a period of 10 years which compare to the conventional boiler combined with chiller.

碩士
國立臺灣大學
機械工程學研究所
107
When the world began to promote energy conservation issues, the energy-saving benefits of air-conditioning systems are valued by many countries. The proportion of power consumption for energy dissipation is huge. Taiwan is hot in summer. The demand for air conditioning is great, which not only cost a lot, but also cause greatly environmental burden with carbon emissions. If it can directly use solar energy as a source of heat for air conditioners and use shallow geothermal energy to cooling, this way will greatly reduce power consumption and make air conditioners more energy efficient and environmentally friendly. This study use different parameters way to explore the performance of adsorption chillers combined with solar thermal energy and shallow geothermal energy . The COP of the adsorption chiller achieve 0.51 under the operating conditions, of 70 °C regenerative temperature, 22°C cooling water temperature, and 13~15 °C cold water temperature. Under the average radiation amount is about 860 W/m2, the thermal efficiency of the solar collector is about 0.6 and the overall system performance coefficient is about 0.31. It is estimated that use shallow geothermal energy instead of cooling tower system can save 44.6 m3 of water in summer. And it uses less 1.08 kW than cooling tower system.

碩士
國立臺灣大學
機械工程學研究所
105
A Study of Household or Commercial Heat Pump System with Shallow Geothermal Energy By Yung-Nan Chen Master Degree of Engineering, Department of Mechanical Engineering National Taiwan University July 2016 Adviser：Sih-Li Chen, Ph.D. The purpose of this study is to test a geothermal heat pump system with two apply ways, which includes raft foundation water energy and groundwater energy. For shallow geothermal energy which temperature is lower than outdoor air in summer and higher in the winter. With this property, we want to replace the traditional heating and cooling equipment by geothermal heat pump system. In the application of raft foundation water energy and groundwater energy we via six different mode to combine heat pump system with geothermal energy for heating and cooling purpose. For groundwater energy, we used Multi-U type Borehole Heat Exchangers (MUBHEs), made of PVC material tubes to exchange heat from the evaporator or condenser of heat pump. Through experiment, we want to realize the advantages and disadvantages for this two different ways in using shallow geothermal energy. At the same time, we will compare the efficiency and cost with commonly heating and cooling household equipment in Taiwan. According to the experiment, the heating mode with raft foundation water, a high efficiency in COP 4.3 is present. And the cooling mode with raft foundation water has cooling efficiency in COP 4 with providing refrigerating capacity 18 kW. Besides, the dual mode that heating and cooling simultaneously, can provide high efficiency when operating heat pump system in right situation. In the study of these experiment, we will compare two apply modes of geothermal energy and conclusion experimental analysis, find the way to improve design to reach more high efficiency. Keywords : Shallow Geothermal Energy, Heat pump, Multi-U type Borehole Heat Exchangers, raft foundation water

碩士
國立中山大學
電機工程學系研究所
106
This paper investigates the control strategy of Battery Energy Storage System (BESS) to improve the system disturbance for Cimei Island caused by the photovoltaic generation system(PVGS) due to intermittent output and sudden tripping. According to the frequency response of testing on-site BESS discharge, the mathematical models with the corresponding parameters of both diesel-generators and BESS have been confirmed. The transient stability analysis of Cimei grid is executed for step increase of various levels of system loading. Finally, the relationship between the load variation and the time required for frequency drop to 59Hz is derived with regression analysis, which is embedded in the control strategy of BESS. This thesis selects the Cimei Island for case study to illustrate the effectiveness of the proposed BESS control strategy. The data of power grid such as the generators, transformers, distribution, feeder and load demand are collected. The voltage variation due to PV power generation is calculated for peak and off-peak period respectively. The transient stability analysis of Cimei power system is performed considering BESS high-speed discharge control to solve the system frequency response for variation of PV power generation and tripping of whole PV system. It is found that the implementation of BESS is very critical to maintain good transient stability and voltage quality for the offshore island power grid with high penetration of renewable energy.

碩士
國立中山大學
電機工程學系研究所
104
This thesis develops the power system models of Chimei Island and Dongji Island, including generator model and parameter, translator, feeder and loading data. The thesis investigates load flow analysis and transient stability analysis for Chimei Island in both heavy load and light load scenarios by PSSE-32. Then the transient stability analysis is executed by considering the tripping and power variation with various ramp-rates of photovoltaic generation system. Power supply instability and frequency fluctuations become longer with high penetration of renewable energy. This paper reports on power stability control and frequency compensation by using an energy storage device. The use of an energy storage device improves the energy efficiency of the offshore island power systems depending on time and weather conditions. Keywords: Photovoltaic Generation System, Energy Storage, Load Trip, Transient Stability, Chimei Island

碩士
國立高雄科技大學
電機工程系
107
This thesis presents control strategies that involve a battery energy storage system (BESS) for a microgrid power system on an offshore island with a high penetration of PV renewable energy. An energy management system performs the supervisory control and data acquisition of diesel generators (DGs), distribution feeders, a PV system and the BESS. The simulation uses mathematical models of the diesel generators, the PV system and the BESS. The parameters of the generator models are validated using real test data concerning the microgrid response to the power control of the BESS to simulate a step change in the system load demand. An expert system is embedded in the iEMS to support decision-making for fast discharging of power from the BESS to improve the transient stability of the grid under large disturbances, such as the tripping of the DGs or the PV farm. To support the economic dispatch of the microgrid, a strategy of peak shaving and valley filling of the net system load profile is perform to improve the system load factor using the BESS; the strategy considers hourly forecasting of the system loading and solar power generation. The results of a system simulation and field test demonstrate that the proposed control strategies that involve the BESS significantly improve the power service quality and transient stability of the system in the island microgrid, which has a high penetration of renewable generation.

碩士
國立臺北科技大學
建築與都市設計研究所
100
As we know, the nature resources in Taiwan is not sufficient, geothermal energy is one of important nature energy. So far 26 famous geothermal places were developed and used in Taiwan. Geothermal energy can be used to generate power, warm up the air condition system, and heat the water; as well as develop the tourism of spring water for leisure and other multiple functions. The operation of air condition unit is occupied 30% of energy consumption in the building equipment. To analyze different parts of the operation of air condition, main power station is occupied 60% sharing, water pump is 11%, air condition box and indoor fan is 13% and others is 16%. Using geothermal energy to assist air condition system will reduce the power consumption on the start of main station and decrease the energy exhaustion. Comparing with traditional air condition, geothermal energy can save the energy, prolong the time of maintenance, extend the life cycle of air condition system and reduce the cost for operation. The thesis is a study of geothermal energy application to assist air-conditioning system to save energy-a case study of Taiwan Sea Gaia Spring Hotel, using spring water with the temperature 90℃~100℃ to assist main power station of air condition, to discuss the possibility to save main power station energy consumption and reduce the energy exhaustion.

According to U.S. Department of Energy, offshore wind energy has the potential to generate 7,200 TWh of energy annually, which is nearly twice the current annual energy consumption in the United States. With technical advances in the offshore wind industry, particularly in the floating platforms, windfarms are pushing further into the ocean. This creates new engineering challenges for transmission of energy from offshore site to onshore. One possible solution is to convert the energy produced into chemical energy of ammonia, which was investigated by Dr. Eric Morgan. In his doctoral dissertation, he assessed the technical requirements and economics of a 300 tons/day capacity ammonia plant powered by offshore wind. However, in his dissertation, one of the assumptions was connection to the grid which provided auxiliary power to keep the ammonia plant operational and produce at rated capacity. It also allowed selling of excess power to the grid in the scenario of excess power production by wind farm during high winds. This thesis explores the technical and economical feasibility of a similar system, except that the ammonia plant will be on a plantship and there is no connection to the grid. This creates a challenge as the ammonia synthesis plant must operate between 65-100% loads. Thus, the concept of multiple mini-ammonia plants is used to address the scenario of wind energy production at less than rated power. This will allow operation of one or more mini-ammonia plant (corresponding to the available energy from offshore wind). In the event of wind speed lower than the cutoff wind speed for the turbine, the ammonia plant will use the produced ammonia as fuel, with the help of a gas turbine running on either Brayton cycle or combined cycle, to keep the plant idling. It will maintain the reaction conditions of the synthesis chamber and will not produce any ammonia. This is an important step as it takes days to reach the reaction conditions to start ammonia production again after shutting down due to unavailability of energy at low winds. Thus, at any windspeed, a mini-ammonia plant would either idle or operate between 65-100% load. This model will be used to simulate the total energy consumption, total energy captured by the wind farm, and the total ammonia produced. This will further help in assessing the final cost of producing, transporting, and consuming ammonia as fuel and thereby provide a better understanding of the feasibility of implementing this technology. According to U.S. Department of Energy, offshore wind energy has the potential to generate 7,200 TWh of energy annually, which is nearly twice the current annual energy consumption in the United States. With technical advances in the offshore wind industry, particularly in the floating platforms, windfarms are pushing further into the ocean. This creates new engineering challenges for transmission of energy from offshore site to onshore. One possible solution is to convert the energy produced into chemical energy of ammonia, which was investigated by Dr. Eric Morgan. In his doctoral dissertation, he assessed the technical requirements and economics of a 300 tons/day capacity ammonia plant powered by offshore wind. However, in his dissertation, one of the assumptions was connection to the grid which provided auxiliary power to keep the ammonia plant operational and produce at rated capacity. It also allowed selling of excess power to the grid in the scenario of excess power production by wind farm during high winds.\\ \par This thesis explores the technical and economical feasibility of a similar system, except that the ammonia plant will be on a plantship and there is no connection to the grid. This creates a challenge as the ammonia synthesis plant must operate between 65-100\% loads. Thus, the concept of multiple mini-ammonia plants is used to address the scenario of wind energy production at less than rated power. This will allow operation of one or more mini-ammonia plant (corresponding to the available energy from offshore wind). In the event of wind speed lower than the cutoff wind speed for the turbine, the ammonia plant will use the produced ammonia as fuel, with the help of a gas turbine running on either Brayton cycle or combined cycle, to keep the plant idling. It will maintain the reaction conditions of the synthesis chamber and will not produce any ammonia. This is an important step as it takes days to reach the reaction conditions to start ammonia production again after shutting down due to unavailability of energy at low winds. Thus, at any windspeed, a mini-ammonia plant would either idle or operate between 65-100\% load. This model will be used to simulate the total energy consumption, total energy captured by the wind farm, and the total ammonia produced. This will further help in assessing the final cost of producing, transporting, and consuming ammonia as fuel and thereby provide a better understanding of the feasibility of implementing this technology.