Rozprawy doktorskie na temat „Low head pumps”

Buildings are responsible for over one third of the energy demand in Europe. Thus, reducing their energy consumption, increasing energy efficiency and integrating low carbon energy sources have become primary goals in the transition towards a sustainable society. District heating and cooling (DHC) systems play a key role to achieve these targets, as they allow any available source of heat to be exploited, including waste heat and renewable heat sources such as geothermal or solar heat. Nowadays, state-of-the-art DH networks have sup-ply temperatures of 70°C in winter and 55°C in summer. Due to their top-down structure, today’s networks are not well-suited for decentralized heat supply. The present thesis explores the potential of a new generation of DHC systems, that distribute heat at lower temperature (from 15°C to 45°C) and use booster heat pumps in the customers substations to raise the temperature level according to the needs of the building served. This concept brings several advantages over conventional networks, such as the abatement of thermal losses, the extension of the temperature range of recoverable heat sources and the potential decentralization of heat supply. In a preliminary analysis, the implementation of the system was investigated for a small town in the North-East of Italy with a large amount of available wastewater in a tem-perature range between 45 and 55°C. In this case-study, the DH system with booster heat pumps reduced the primary energy consumption of about 70% compared to a heat supply sce-nario based on individual gas boilers and of 30% compared to a traditional DH system with a central heat pump and an auxiliary gas boiler. Such improvement occurs also because the dis-tributed heat pumps can be adapted to the supplied buildings: this is particularly relevant con-sidering the heterogeneneity of the building stock in the urban environment. The optimal de-sign and management of this kind of networks is a new topic in the scientific literature. There-fore, the first part of the work tries to answer the following general question: “What are the most critical aspects in the system design?” The thesis analyses the effect of some critical design parameters on the cost of heat for the final user, using the payback time for the DH utility as a fixed constraint. It emerges that a higher supply temperature leads to two positive effects: the heat sales increase and the ex-penditure for electrical energy is reduced. The levelized cost of energy of the system drops by 17% when the network supply temperature goes from 40°C to 20°C, provided that the heat can be recovered at the same price. Moreover, the network temperature difference plays an important role in the design phase. Depending on the business model adopted by the DH utili-ty to purchase the heat and on the specific energy consumption of the considered building stock, an optimal temperature difference may arise from the trade-off between low initial in-vestment and low operational costs. The decentralized structure of these networks also intro-duces new challenges in the control strategies. Indeed, if the utility purchases and/or produces the electricity needed by the heat pumps, the control strategy should possibly take into ac-count the price and/or the production cost of electricity. Secondly, the control system of the network manager must be able to react on increasing shares of decentralized heat supply from the prosumers. These issues can be summarized by the following research question: “How can the network manager control its heat supply units in a smart way?” This part of the thesis was developed within the H2020 Project FLEXYNETS. In order to minimize the operational cost for the network manager, an intelligent control method based on MILP optimization was developed and tested via computer simulations. The proposed control system proved capable of self-adapting to the current situation of heat demand, waste heat availability and electricity price, such as to increase the share of electricity self-consumption and the share of low-grade heat recovered from the remote prosumers. During two simulated winter months, the advanced control strategy was able to reduce operational costs by 11% compared to a conventional rule-based control. The receding horizon scheme makes the sys-tem potentially feasible for real-time applications. The novelty of this work consists not only in the aforementioned findings per se, but also in the methodological framework that led to those results. In fact, the developed models allowed to integrate the whole energy system (buildings, substations, district heating network and heat supply stations) into a unique simulation environment.
Gli edifici sono responsabili di oltre un terzo della domanda di energia in Europa. Ridurre il consumo di energia, aumentare l’efficienza energetica ed integrare fonti di energia a basso impatto ambientale sono diventati obiettivi fondamentali nella transizione verso un futuro sostenibile. Le reti di teleriscaldamento e teleraffrescamento hanno un ruolo fondamen-tale nel raggiungimento di questi obiettivi, in quanto permettono di recuperare ed utilizzare il calore da qualsiasi fonte sia disponibile a livello locale: dal calore di scarto al calore di fonti rinnovabili come il geotermico e il solare. Oggi le reti di teleriscaldamento più efficienti hanno temperature di mandata pari a circa 70°C in inverno e 55°C d’estate. A causa della loro struttura centralizzata, le reti di oggi non sono predisposte per la generazione distribuita del calore. Questa tesi analizza il potenziale di una nuova generazione di reti, che distribuiscono il calore ad una temperatura più bassa (in generale tra 15°C e 45°C) e usano pompe di calore di rilancio nelle sottostazioni d’utenza per fornire calore alla temperatura desiderata da ogni sin-golo edificio. Questa nuova filosofia progettuale porta diversi benefici rispetto alle reti tradi-zionali, come l’abbattimento delle perdite di calore, la possibilità di integrare fonti a più bassa temperatura e la decentralizzazione del sistema. In una analisi preliminare, l’implementazione del sistema proposto è stata studiata per una cittadina italiana in cui è presente un’ingente quantità di acqua di risulta tra i 45°C e i 55°C. In questo caso studio, la rete di teleriscalda-mento con le pompe di calore distribuite riduce il consumo di energia primaria e le emissioni di anidride carbonica di circa il 70% rispetto allo sceanrio costituito da caldaie autonome e del 30% rispetto ad una rete tradizionale con pompa di calore centralizzata e caldaia a gas di inte-grazione. Questo miglioramento si verifica anche perché ogni pompa di calore viene adattata all’edificio, il che assume notevole importanza in virtù dell’eterogeneità del parco edilizio normalmente presente nel contesto urbano. La progettazione e la gestione di questo tipo di reti è un argomento nuovo nella letteratura scientifica. La prima parte della Tesi cerca perciò di rispondere ad una domanda di carattere generale: “Quali sono gli aspetti più importanti nella progettazione del sistema?” La tesi analizza gli effetti di alcuni parametri di progetto sul costo dell’energia all’utente fina-le, mantenendo fisso il tempo di rientro dell’utility. Ne è emerso che una elevata temperatura di mandata porta a due benefici: (a) aumentano le vendite di calore da parte dell’utility e (b) si riduce il consumo di energia elettrica delle pompe di calore. Come conseguenza, passando da 40°C a 20°C ato dell’energia si abbassa del 17% a parità di costo del calore che alimenta la rete. In più, anche la differenza di temperatura tra mandata e ritorno ha un ruolo importante nella fase di progetto della rete. Il compromesso che nasce per contenere da un lato l’investimento iniziale e dall’altro i costi operativi può portare ad una differenza di temperatu-ra ottimale tra mandata e ritorno. La struttura decentralizzata di queste reti inoltre fa nascere la necessità di studiare nuove strategie di controllo. Infatti, se l’utility compra e/o produce l’energia elettrica di cui le pompe di calore necessitano, la strategia di controllo deve tenere in considerazione anche il prezzo e/o il costo di produzione dell’energia elettrica. Inoltre, il si-stema di controllo del gestore della rete deve essere in grado di far fronte a quantità ingenti di calore fornito dai prosumers. Questi problemi possono essere riassunti nel seguente quesito: “In che modo il gestore di rete può controllare i suoi impianti?” Questa parte della tesi è stata sviluppata nell’ambito del progetto H2020 FLEXYNETS. Al fine di minimizzare il costo operativo per il gestore di rete è stato sviluppato e successivamente testato attraverso simulazioni un metodo di controllo intelligente basato su ottimizzazione MILP. Col metodo proposto il sistema è stato in grado di adattarsi alla situazione di domanda di calore, disponibilità di energia da parte dei prosumers e prezzo dell’elettricità in modo tale da aumentare la quota di autoconsumo e aumentare la quota di energia recuperata dai prosu-mers. Durante i due mesi di simulazione, la strategia di controllo è stata in grado di ridurre i costi operativi dell’11% rispetto ad un sistema di controllo convenzionale. Lo schema “rece-ding horizon” rende il metodo potenzialmente fruibile in applicazioni real-time. Il contributo della tesi non è solamente relativo ai risultati in quanto tali, ma anche alla metodologia utiliz-zata per raggiungerli. Infatti i modelli sviluppati hanno permesso di studiare il sistema energe-tico nel suo insieme.

One of the major challenges of this decade is developing more sustainable energy systems that contribute to environmental concern, especially climate change mitigation. Extending the operating conditions of the heat pump technology to higher temperatures will allow decarbonising the industrial sector from two slopes: recovering heat from waste heat sources that currently is being rejected to the ambient and produce heat at the required industrial thermal levels that become useful for the industrial processes. Both challenges will make possible reduce the equivalent CO2 emissions of the industrial sector and operate at high temperatures that conventional heat pumps. This thesis deals with the development of high temperature heat pumps through a comprehensive theoretical and experimental analysis to overcome different technology challenge: architecture, refrigerants, experimental prototype, advanced applications and system integration, providing new knowledge that represents a step forward in high temperature heat pump technology.
Uno de los mayores desafíos de esta década recae en el desarrollo de sistemas energéticos más sostenibles que contribuyan a la preocupación medioambiental, especialmente la mitigación del cambio climático. Extender las condiciones de funcionamiento de la tecnología de bomba de calor a temperaturas más elevadas permitirá descarbonizar el sector industrial desde dos vertientes: recuperando calor de fuentes de calor residual, actualmente disipado al ambiente y producir calor a los niveles térmicos requeridos, útiles para los procesos industriales, reduciendo así las emisiones de CO2 equivalentes del sector industrial y contribuyendo al desarrollo sostenible. Esta tesis pretende abordar el desarrollo de bombas de calor de alta temperatura a través de un análisis teórico y experimental, para abordar diferentes desafíos tecnológicos: arquitectura, refrigerantes, prototipo experimental, aplicaciones avanzadas e integración de sistemas, generando nuevos conocimientos que representan un paso adelante en la tecnología de bombas de calor de alta temperatura.
Programa de Doctorat en Tecnologies Industrials i Materials

The European standard EN15450 states that the Coefficient of Performance (COP) target range for a Ground Source Heat Pump (GSHP) installation should lie within the range of 3.5 to 4.5; when used for heating a building, and a typical Air-Source Heat Pump (ASHP) has a COP of 2.0 to 3.0 at the beginning of the heating season and then decrease gradually as the ambient air becomes cooler, whereas a typical GSHP is in the range of 3.5 –4.0, also at the beginning of the heating season and then decrease gradually as heat is drawn from the ground. For these reasons, in the middle of winter, when the COP drop, the heat pumps can generally only be considered as a ‘pre-heating’ method for producing higher temperature heat such as domestic hot water. In addition soil presents certain difficulties, due to the high cost of drilling to position coils in the ground compare to air source, although frost formation on the evaporator in winter limits also limit the use of air source. Though technology advances or are needed to overcome those issues. The aims of this project, therefore, were firstly to reduce the drilling length of the ground heat exchanger of the ground source heat pumps and to maintain high COPs of the air and ground source heat pumps from beginning to the end of the heating season; and secondly to develop a viable alternative evaporator for air source heat pumps to reduce frost formation during winter. These were achieved; the first aim through the combination of ground loops with solar-air panels or solar roof/collectors roof to ground heat exchangers loops to reduce the length of the boreholes, and to reduce the freezing effects around the boreholes, hence increase or maintain a constant temperature during heating season. The second aim was also achieved through development and validation of novel air source heat pump evaporator, using Direct Expansion (DX) black flat plate absorber or/and vacuum tubes for frost reduction. In this thesis, in order to achieve the above aims; four aspects of investigations have been independently investigated as following: 1- Preliminary investigation on Direct Expansion (DX) Solar Source Heat Pump system. 2- Investigation on the performance of the DX- PV/heat pipe heat pump system to reduce frost and enhance the COP of the air source heat pumps, 3- A small scale testing on the heat injection on energy piles for residential buildings for earth charging by means of solar roof/collectors 4- A field trial testing of the performance of the combination of solar-air thermal collectors with conventional GSHP with shorter ground heat exchangers (48m deep) to charge the ground and reduce freezing effects around the piles after heating cycle. From the simulation results, the novel PV/hp-HP system has a COP ranging from 4.65 to 6.16 with an average of 5.35. The condenser capacity ranging from 33 to 174 W would provide the heat source for space heating and domestic hot water. The energy performance of the novel PV/hp-heat pump was not as good as expected due to the low solar radiation. It should be much better in some low latitude locations with better solar radiation. The results of this thesis have shown that the length of ground source boreholes could be considerably reduce by about 60% compare to conventional boreholes using a combination of solar-air collectors with the GSHP and the average COP of 3.7 was achieved.

The building sector is a prioritized area in the European Unions (EU) ambition to reduce the total final energy use by 20 %; lower the emission of greenhouse gases by 20 % and using energy 20 % more efficient by 2020. The residential sector in the European Union accounts for 27% of the un-ion’s final energy use and the EU views decentralized energy generation and heat pumps as important measures in reducing the energy demand in the building sector. In recent years a rapid decrease in photovoltaic system prices has led to a growing popularity in Sweden. This fact in combination with a large in-crease of heat pump systems in residential buildings the last decade makes a combination of heat pumps and solar energy systems an interesting sys-tem configuration to analyze. In addition, the electricity price structure in Sweden and the uncertainty of the sustainability of the Swedish solar energy support schemes makes the topic of self-consumption an important research area. Different solar energy systems for residential buildings and two different storage technologies, batteries and hot water storage tanks, have been analyzed with regards to profitability, solar energy fraction and self-consumption levels. The results suggest that the system with a heat pump in combination with a photovoltaic system can be profitable and have high solar energy fractions and high levels of self-consumption and that the systems with storage are not profitable but give high levels of self-consumption and relatively high solar energy fractions. The hot water storage gives almost as high level of self-consumption as batteries but have half of the batteries levelized cost of electricity. A system with a ground source heat pump and a solar thermal system are ineffective, unprofitable and give low solar energy fractions. A system with a weather forecast controller gives a small increase in self-consumption and is unprofitable. The proposed near energy zero building definition proposed by the Swedish National Board of Housing, Building and Planning in 2015 is unclear in terms of what electrical load the PV electricity reduces in the building. This has a fairly large impact on the building specific energy demand.

The main outcome of this research is the development of a Probabilistic Impact Assessment methodology to comprehensively understand the effects of low carbon technologies (LCTs) in low voltage (LV) distribution networks and the potential solutions available to increase their adoption. The adoption of LCTs by domestic customers is an alternative to decreasing carbon emissions. Given that these customers are connected to LV distribution networks, these assets are likely to face the first impacts of LCTs. Thus, to quantify these problems a Monte Carlo-based Probabilistic Impact Assessment methodology is proposed in this Thesis. This methodology embeds the uncertainties related to four LCTs (PV, EHPs, µCHP and EVs). Penetration levels as a percentage of houses with a particular LCT, ranging from 0 to 100% in steps of 10%, are investigated. Five minute time-series profiles and three-phase four-wire LV networks are adopted. Performance metrics related to voltage and congestion are computed for each of the 100 simulations per penetration level. Given the probabilistic nature of the approach, results can be used by decision makers to determine the occurrence of problems according to an acceptable probability of technical issues. To implement the proposed methodology, electrical models of real LV networks and high resolution profiles for loads and LCTs are also developed. Due to the historic passive nature of LV circuits, many Distribution Network Operators (DNOs) have no model for them. In most cases, the information is limited to Geographic Information Systems (GIS) typically produced for asset management purposes and sometimes with connectivity issues. Hence, this Thesis develops a methodology to transform GIS data into suitable computer-based models. In addition, thousands of residential load, PV, µCHP, EHP and EV profiles are created. These daily profiles have a resolution of five minutes. To understand the average behaviour of LCTs and their relationship with load profiles, the average peak demand is calculated for different numbers of loads with and without each LCT.The Probabilistic Impact Assessment methodology is applied over 25 UK LV networks (i.e., 128 feeders) for the four LCTs under analysis. Findings show that about half of the studied feeders are capable of having 100% of the houses with a given LCT. A regression analysis is carried out per LCT, to identify the relationships between the first occurrence of problems and key feeder parameters (length, number of customers, etc.). These results can be translated into lookup tables that can help DNOs produce preliminary and quick estimates of the LCT impacts on a particular feeder without performing detailed studies. To increase the adoption of LCTs in the feeders with problems, four solutions are investigated: feeder reinforcement, three-phase connection of LCTs, loop connection of LV feeders and implementation of OLTCs (on-load tap changers) in LV networks. All these solutions are embedded in the Probabilistic Impact Assessment. The technical and economic benefits of each of the solutions are quantified for the 25 networks implemented.

Geothermal heat pumps represent an interesting technology that is expected to contribute significantly to the reduction of primary energy use for heating and cooling and meet the targets set by the European Union. Additional benefits of this technology are related to the integration with discontinuous energy resources, in particular wind, combining heat and power. The replacement of conventional heating systems such as boilers, with heat pump systems allows the de-localization of emissions of micropollutants from urban centers to the sites in which thermal power stations are operating. This also enhances emissions monitoring and control. Furthermore, the use of distributed production systems based on the use of renewable sources reduces also CO2 emissions. (Lo Russo et al., 2011) In this general context, the increasing implementation in several areas of the world of the open-loop groundwater heat pumps technology which discharge into the aquifer for cooling and heating buildings could potentially cause, even in the short term, a significant environmental impact associated with thermal interference with groundwater, particularly in the shallow aquifers. The discharge of water at different temperatures compared to baseline (warmer in summer and colder in winter) poses a number of problems in relation to the potential functionality of many existing situations of use of the groundwater (drinking water wells, agricultural, industrial, etc.). In addition, there may be cases of interference between systems, especially in the more densely urbanized. This means that the alteration of the temperature of the groundwater determined by a plant may affect the installations located downstream, with significant alterations of the performances of the systems themselves. These issues highlight how it is crucial for the compatible development of the technology of groundwater heat pumps discharging into aquifers that it shall be a fair assessment and technically effective both for cooling and heating plants and pumping and injection systems in ground. The current legislation related to withdrawals and discharges into aquifers design a framework suitable for the protection of groundwater and permit to decide the 3 best configuration of the plant with a case by case approach. Appropriate specialized hydrogeological investigations should be performed for the characterization of the main hydrogeological parameters of the subsoil at the considered site. In this thesis some important aspects related to the development of open-loop heat pumps have been explored in a typical urban contest (Torino city, NW Italy). The results of the work have allowed to define several fundamental aspects in order to optimize the design choices of GroundWater Heat Pump (GWHP) systems. After a general description of the low enthalpy geothermal heat pumps technologies (Chapter 1), the analysis and comparison of the current hydrogeology problems in urban area are described, considering the impact of groundwater heat pump system in a urban contest (Chapter 2). Urban and industrial development can impose major stresses on groundwater resources. The conceptual model for the groundwater flow system, the schematization of the aquifer boundaries and the estimation of basic hydrogeological parameters are among the main issues which should be investigated in the development of open-loop heat pumps plants. In particular, some characteristics of urban elements require particular attention if compared to less anthropized areas. In Chapter 3 the geological and hydro-stratigraphical characteristics of the Torino test site have been described. This chapter includes a complete description of the GWHP system plant and monitoring system that has been installed in the Politecnico di Torino and the illustration of the fundamentals of the numerical modelling we performed using a specific commercial code (FEFLOW® Diersch, 2010). In Chapter 4 the relative significance of the different subsurface parameters that mostly characterize the developed thermal plume is determined through a detailed sensitivity analysis under different simulation conditions. In Chapter 5 we explore the importance of the compliance between real and simulated variable input flow data (discharge and injection temperatures) to obtain reliable simulation results. In the following Chapter (6) we explore the potential alternative to Finite Element Modeling (FEM) tools in the spatial and temporal prediction of the thermal plume development by considering the use of Artificial Neural Networks (ANNs). Finally, in 4 Chapter 7, we consider the potential alternatives to traditional vertical drilled wells to disperse the thermal energy in the aquifer comparing such technology with the alternative use of gabions draining. The results highlighted some important aspects that should be considered in the modeling of the open-loop heat pumps that are summarized in the Conclusions. The research individuated some important aspects and reached important results but, as clearly highlighted, several aspects of the analysis of these kind of technology should be further investigated by research and practical monitoring observations in the future. However, even taking into account all the limitations of the open-loop heat pumps technology, we believe that these systems represent one of the most promising potential clean energy source especially in the urban areas under transformation in order to reach the important goal of greenhouse-gas emission reduction of the future Smart liveable Cities.

This thesis investigates a novel combination of a jet-pump refrigeration cycle and a thermal (ice) storage (TIS) system that could substantially reduce the electrical energy requirements attributable to comfort cooling.Two methods of TIS were identified; spray ice TIS would use evaporative freezing to store ice on a vertical surface,and encapsulated ice TIS would freeze a bed of encapsulated elements by sublimation freezing.Thestudy also investigates jet-pump refrigeration at partload and a convergent-divergent design manufactured from a thermoset plastic to make recommendations for performance enhancement for a system that has a low COP. An experimental rig was built to investigate the novel concepts in the laboratory. Encapsulated ice TIS was superior to spray ice TIS because, for the same nominal secondary flow, sublimation freezing causes an increase in coolth storage rate of about 10 % compared to evaporative freezing. Encapsulated ice stores experience difficulties in fully discharging their coolth (approximately 6% in this case), but spray ice TIS can be used to produce an ice/brine slurry enabling all of the ice to be used, and so may be more suitable if the unmelted ice represents a large proportion of the cooling capacity. Approximately 85 % to 90 % of the ice formed on the vertical surface during spray ice TIS testing was formed by evaporative freezing from a falling film. At high saturation conditions, heat is transferred mainly by conduction across the falling film. Both the growth of an ice layer on a vertical surface and freezing of encapsulated elements were found to be successful, but a large data spread was observed during spray ice TIS testing. It was thought that a variation in the steady-state saturation conditions in the evaporator/ice store was caused by variability of droplet size distribution from the spray nozzle flow, which may make a full-scale system unreliable. The COP of the spray ice TIS system was approximately 0.15 compared to a COP of approximately 0.25 found during encapsulated ice TIS testing. The difference was because of the use of an over-expanded primary nozzle, which restricted secondary flow and increased momentum losses. A primary nozzle that expands close to the design evaporator saturation conditions should be used to maximise entrainment ratio. The COP of a jet-pump TIS is low, but a system designed to operate at off-peak periods could increase the COP to about 0.8 by taking advantage of the lower ambient conditions. The measurement of entrainment ratio was used successfully to determine ice storage rate and COP. This was valid because of the assumption that the saturation conditions in the evaporator/ice store approached steady-state. However, over longer periods that would be found in large-scale systems, the ice storage rate and entrainment ratio may fall substantially. The steady-state assumption could still be used to observe the change in evaporator conditions by sampling over short time intervals (30 minutes). At part-load, increases in evaporator saturation temperature could increase entrainment ratio substantially (50 % increase) for only a small reduction in critical pressure lift ratio Ns *(15 % reduction). A variation in chilled water temperature could be used to boost entrainment ratio at the peak demand. The variation in Ns* is too small to use this strategy to control the jet-pump with respect to condenser operating conditions. The entrainment ratio is approximately proportional to the diff-user to primary nozzle area ratio. A doubling of entrainment ratio was attained for only a 15% reduction in Ns*. The change in geometry from a constant area throat to a convergent-divergent design caused the flow through the jet-pump to vary with outlet conditions indicating that secondary flow was not choked. Higher entrainment ratios and pressure lift ratios were observed, but the entrainment ratio varied with outlet conditions in the form of peaks and troughs, making its operation unpredictable. This was thought to be caused by the restriction in secondary flow area due to the interaction of the primary jet and the curved wall. The convergent-divergent design manufactured from a thermoset plastic was successfully tested, showing that a plastic material can be used as a material of construction. In principle, a large number of jet-pump units could be manufactured from a single mould, reducing the first cost. The investigation proved the concept of jet-pump TIS. Waste-heat could be utilised over 24 hours and year round, increasing the efficiency of the process. The use of a convergent-divergent throat design, multiple geometry jet-pumps and operation at off-peak periods can maximise the performance over a cooling season, and be competitive with other TIS and chiller systems. The mass production of jet-pumps using injection moulding techniques could reduce substantially the capital cost of a system. All of these factors should encourage the development of such systems, so that the harmful emissions caused by the use of air conditioning systems can be minimised.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 63).
An analytical model for the functionality of a permanent-magnet synchronous motor is developed. Taking as input a specific geometry, it predicts steady-state losses of a design at an average rate of 0.85 seconds per analysis, orders of magnitude faster than existing finite-element methods. A wide design space is analyzed and, based on the necessary motor profile and manufacturing limits, an optimal design is selected. Subsequently, this motor was fabricated and integrated with a prototype design of a high-density heat pump. This application requires an unusually low motor profile - with the motor width being much (~ 10 x ) larger than its thickness - which has not been explored by other researchers. Furthermore, the design metrics specify a tight upper bound of 33.3 W on available power. Electrical characteristics are modeled and tested to determine optimal phase-excitation waveforms. Finally, power electronics with a sensorless control scheme are designed and incorporated using a custom-designed printed circuit board at an all-inclusive cost of under $50, which is well below the price of typical development control boards used to test prototype motors. Speeds of up to 7000 RPM were observed. At the design point of 5000 RPM, the motor delivered 35 mN-m of torque and drew 23.8 W of power, significantly below the available power budget.
by David P. Jenicek.
M.Eng.

The Ground Source Heat Pump (GSHP) is a promising technology for the heating and cooling of buildings with renewable energy sources. Borehole Heat Exchangers, in which heat is exchanged by circulating a heat carrier fluid into a pipe closed loop, are the most used typology. The energy performances of these plants depend from the properties of the BHE and of the soil. In this work, the operation of BHE for a period of 30 years has been simulated, using a finite-element subsurface flow and heat transport modelling code (FEFLOW). The relative influence of each BHE, hydrogeological and thermal soil property has been investigated, running a set of simulations and analyzing the resulting fluid temperatures in the closed loop to estimate the heat pump energy consumption. Comparing the results, we observe that the length is the most important BHE property, and it should be optimized in order to minimize the overall expense (installation and maintenance); also the pipe distance, the grout heat conductivity and the properties of the heat carrier fluid play an important role. The soil heat conductivity heavily influences the resulting fluid temperatures, and in-situ tests should be carried to predict the plant operation accurately. The presence of subsurface flow enhances the heat transfer in the subsoil, improving the heat pump performances. The heat dispersivity spatial dependence is still unknown, and this causes a strong uncertainty in the prediction of BHE operation in presence of groundwater flow.

The following project aims to create a decentralised heat network development methodology which makes best use of heat sources and loads and can be widely applied to evaluate the energy economics of a heat network scheme and energy centre. As the energy transition takes shape, the key is connectivity and the potential now, or in the future to aid progressive development of energy systems and technologies rather than traditional models that consider schemes individually in isolation and not holistically; where with the latter we’re more likely to end up with robust, future-proof solutions.   A methodology was formulated which encompassed various elements of decentralised energy masterplanning approaches and enabled heat demand loads and associated profiles to be simulated. The development of an optimisation model enabled strategies to be devised (maximisation of energy generation and revenue independently) over a set technology lifetime for the energy centre.   The results have concluded that the maximisation of revenue optimisation strategy is the most viable economically. An energy generation optimisation for the energy centre produced optimal results in terms of its heat generation profile, however, the scheme was not economically viable due to significantly high capital costs associated with piping connections to multiple clusters.   A CO2 emission analysis was carried out for a selection of energy technologies (CHP, heat pumps and gas boilers) for the heat network energy centre. An evaluation of the results has concluded that the optimal selection of technology for the energy centre for the minimisation of CO2 emissions is heat pumps. When selecting combinations of technologies for peak and base loads within the energy centre, heat pumps (base load) and gas boilers (peak load) are optimal when aiming to maximise revenue generation whilst minimising CO2 emissions. In this case, reductions in associated CO2 emissions have been calculated to achieve up to 89.07% when compared to a base case gas boiler technology (energy centre) scenario alone.   The methodology and models developed in this project can be widely applied to decentralised heat network projects in London in order to identify optimal development and expansion strategies and evaluate the energy economics of schemes.

The geothermal heat pump systems have been developed in Italy only during the last few years and today only some regions are investing in this field. In particular, the Tuscany Region and the Autonomus Bolzano Province have promoted the study of these systems with the objective of being able to promote and to disclose in the time this technology. A fundamental aspect for a oculata planning and a greater knowledge of the real predisposition of the territory to the installation is sure the acquaintance of the specification of the geological, geophysical, geotechnical and hidrogeological systems and the parameters that enter at stake. The fundamental parameter in a position to discriminating from a point of view not only economic but also of real thermal yield is the thermal conductivity that the determinated site is able to offer. This research examines the essential elements that they characterize a system of geothermal heat pump system. It has been to such respect important to study at first the various type of systems from a technical-engineering point of view that of principle operation. In a second phase, the parameters were characterized to consider in phase of thermal characterization, therefore the study of the heat conductivity, the transmission of heat between probe and land, the thermal stability and the thermal behavior of the ground. In particular, regarding the study of the heat conductivity, in the Capitol 3 are given the tools used for the acquisition of such parameter through investigations in the laboratory and in situ. Successively the normatives elements that regulate the phases of authorization were characterized and analyzed, afterwards planning and installation of the heat pumps systems in the various international and national contexts were considered. A panoramic pre-emptive of the normative picture of the Nations and Regions was drawn to the vanguard in the field of geothermal energy to low and the lowest entalpy. This was dictated by the requirement to define the problematic ones met from the agencies that have legislated in matter and to put of in evidence virtues and criticality. The checks carried out both in terms of legal and procedural provided an inspiration for the creation of authorization processes and procedures for the installation of various types of geothermal heat pump systems in various geological contexts, in order to assess the possible impacts that these systems can cause on the environmental matrices. Central part of the research project is the study of the heat conductivity, parameter key for the development of a useful cartography in this field. It was decided to perform a literature search of that parameter, in order to process and then compare the data of thermal conductivity obtained from detailed investigation carried out in a pilot site and found through the stratigraphy. In fact, nowadays the available data measured on lithologies of the Italian territory are few and hard to find. The literature research has allowed later to thermally classify the lithostratigraphic units of the geological legend of Sardinia Region, in scale 1:10000, one of the few regions to boast of an updated geological territorial Continuum. The performed research is based on the possibility of drawing up maps of the thermal conductivity from the investigation and trying different methods, ultimately, to compare the two approaches. The first method concerned a detailed investigation of the pilot site located in proximity of Lago Baratz (Municipality of Sassari) through a geological and hidrogeological framework, a pedologic survey and at last, investigations of geoelectrical type. The detailed study has afforded to frame the site potentially interesting to the installation of a system being afforded to characterize from a thermal point of view the area. Therefore, it has been possible to calculate the value of thermal yield for 1800 – 2400 hours of operation of the system in modality cooling and heating. By means of the second method of calculation, it was considered appropriate to disclose a test personally conducted in the territory of the Arezzo Province. Thus, it is reported below an example of processing of the data of thermal conductivity from the stratigraphic information. Giving the high number of information (about 12566 stratigraphic data points), it was decided to perform a first test in order to verify and consolidate the processing procedure. In the Chapter 7 all the passages executed for the elaboration of the thermal conductivity data from the stratigraphic information for the provincial territory are illustrated. Three maps for the depths of interest of 30, 60 and 100 meters Were elaborated. Successively the respective papers of the errors were calculated, allowing to divide the province territory in areas for which it can be identified different planes of address to be followed in the process of thermal characterization. The last chapter contains a possible synthesis of a procedural iter initially for defining the parts that enter as stake in phase of realization of a system. They will follow some detailed lists reported to the criteria to follow, in sensitive areas, for the study and the control from a thermal point of view, of a potentially apt site to the installation of a system The entire research aims to set an example as well as the application of geological information at a scale of detail, the stratigraphic information and spread knowledge of the parameters involved can be combined to create thematic maps useful for public authorities and citizens.

The master's thesis deals with the description of heat pump technology (HP) and its use for apartment buildings. The theoretical part contains an introduction, performance of heat pump technology, in particular a compressor heat pump (CHP). In this section is also mentioned about heat pumps for an apartment buildings. Main focus of this thesis is a design of a compact air-water heat pump for the company AISECO spol. s.r.o. This section is focused a design of an individual components of cooling circulation together with proposal of the circulation and principle of operation.

The master's thesis is focused on heat pumps as a device using sources of a low-potential heat for building's heating. There are individual types of these devices characterized by a principle of operation and used media. Main focus of this thesis is a design of a compact air-water heat pump for the company PZP HEATING a.s. consisting of a cooling circulation’s design and individual components of this circulation. Finally there is a proposal of the heat pump’s case presented at the end of this work.

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

The present work is concerned with the plant of the sport palace “Carmine Romanzi”, known also as “Palacus”, of University of Genoa (Italy). The facility consists of a heat pump coupled, on the cold side, with the thermal part of a solar hybrid field. The hot side of the heat pump has been designed to satisfy the space heating and domestic hot water needs of the structure. The photovoltaic production of the solar hybrid field grants the electricity need of the heat pump and any other electric auxiliary within the plant. Two traditional gas burners integrate the space heating or the domestic hot water production in case of severe boundary conditions (e.g. users’ needs and environmental conditions). Finally there is also a data acquisition and monitoring system in the installation to allow an almost continuous monitoring of the plant. The research topic is about the plant monitoring with the aim of optimal strategies definition in order to maximize the exploitation of the renewable part of the plant. This objective has been achieved thanks to both the data acquired by means of the monitoring system and numerical dynamic simulations carried out with numerical codes (Matlab and TRNSYS). In my opinion, the technology of the solar assisted heat pump (SAHP) still hasn’t been fully appreciated for technical and complexity reasons. Besides the academic and practical issues, the underlying goal of this work is to give a little contribution to reach more competitive and attractive asset. The expectation is to transmit the “hands-on” experience gained along the past three years of my PhD and make it available for others who might treasure it. This study shows a very high level of multidisciplinary since the pilot plant provides the thermal needs of a real structure with real users. It no-longer belongs to a didactic workbench where the boundary conditions (e.g. external temperature, irradiance, thermal loads) were simulated “ad hoc”. The plant faces every day the double challenge of the competition with the traditional heating installation trying to provide the users’ needs (space heating, domestic hot water) with the maximum, optimal exploitation of the renewable sources. The structure of the following chapters is conceived as a report journal where each relevant issue has been illustrated in a specific section. The common goal is the achievement of a low consumption and energy efficient system that can be managed from two main approaches. Firstly, the topic of acceptance namely how the end users’ agreeement influences the usage of the plant and therefore its performance (Chapter 2). Secondly, the field of numerical transient simulations for complex plants has been enquired by means of applications in Trnsys environment (Chapter 3). The two paths have led both to significative material improvements of the plant which have been realised during the past three years and they have provided the chance to deepen specific academic topics (e.g. stratification, validation of different numerical models to simulate specific subsystems of the plant, introduction of new methods to asses a level of acceptance of the facility). In the end, the knowledge acquired by means of the almost continuous monitoring of the plant has been applied to support both the decision making and the design teams in the choice of the new configuration to give to the plant according to the revamping intervention which is taking place. In other words, the key concepts introduced in the last part of this work have been implemented in the revamping design to reach a better plant performance and they are the result of the experience, data acquisition and management, numerical analyses and simulations about the pilot plant performed during the past three years (Chapter 4).

Baigiamajame magistro darbe nagrinėjamos grunto ir atliekinės pastato šilumos panaudojimo galimybės mažaenergiame pastate, Vilniaus mieste, Lietuvoje. Suskaičiuoti keturi pastato energijos balansų variantai, naudojant ”CASAnova” kompiuterinę skaičiavimo programą, su skirtingais atitvarų šilumos perdavimo koeficientais. Pastate taikomos dvi energijos taupymo priemonės. Pirmoji yra gruntinis šilumokaitis naudojamas šviežio oro pirminiam pašildymui mechaninio vėdinimo sistemoje, kurio skaičiavimai atliekami ”GAEA” programa. Antroji yra nuotekų šilumos atgavimo šilumokaitis, naudojamas į pastatą tiekiamo šalto vandens pirminiam pašildymui, atgaunant dalį šilumos iš duše susidariusių nuotekų. Pastatui reikiamas metinis šilumos ir vėsos energijos kiekis gaminamas šilumos siurbliu su vertikaliu gręžiniu grunte, kurio skaičiavimams naudojama ”EED” programa. Gręžinių gyliai yra suskaičiuoti kiekvienam pastato energijos balansų variantui. Atlikti ekonominiai skaičiavimai rodo gruntinio ir nuotekų šilumos atgavimo šilumokaičių įdiegimo pastate ekonominę naudą. Pateikti rezultatai rodo kiekvieno varianto energijos poreikius ir gręžinio grunte gylį priklausomai nuo pastato varianto atitvarų šiluminių savybių bei taikomų energijos taupymo sprendimų. Darbą sudaro 9 dalys: įvadas, 6 skyriai, išvados ir pasiūlymai, literatūros sąrašas. Darbo apimtis – 64 psl. teksto, 41 paveikslai, 14 lentelės, 31 bibliografinis šaltinis.
The final master thesis presents technical analysis of low-energy residential building in Vilnius, Lithuania. Building has low temperature floor heating, mechanical ventilation with heat recovery unit and hot water preparation with buffer tank systems. Using “CASAnova” software is calculated fourth energy balances of building according fourth different heat transfer coefficients of the walls. All heating and cooling energy demand of a building is generated from the ground. It is made by using a heat pump with single borehole. A calculation of borehole sizing is made with “EED” software. Two energy saving technologies are analysed for a building. The first idea is to reduce heat energy consumption of hot water preparation. There is calculated benefit of waste water heat recovery heat exchanger which function is to pre-heat hot water using waste water from the shower. Second idea is to reduce heat energy consumption for fresh air heating in air handling unit. There is calculated benefit of earth-to-air heat exchanger using “GAEA” software. Final result of all calculations shows influence of heat transfer coefficient and energy saving technologies to building annual energy balance and depth of borehole. Economic benefit of using energy saving technologies is calculated. Structure: introduction, 6 chapters, conclusions and suggestions, references. Thesis consists of 64 p. of text, 41 figures, 14 tables and 31 bibliographical entries.

This diploma thesis provides basic information about the thermal pumps and photovoltaic systems. The heat pumps are described regarding their construction and sources of low potential heat. The description of photovoltaic systems explains the main principle of transformation the solar light to electric power and possible cooperation of this systems with the heat pumps. In practical part of the thesis there is a description of the assessed building and calculation of its thermal losses. It is followed by three designs of the thermal pump systems which are supposed to replace the original way of heating - the electric boiler. One of the designs is supported by photovoltaic system. The final part of the thesis provides the calculation of required heat sources for house and water heating, the operation expanses of all three heat pump designs, prices of electric energy and economical reliability of described solutions.

This thesis is concerned with the design of a heat pump that does not use a ventilator during operation. In the introductory chapter, the functioning and the basic components of this device and other types of heat pumps are described. Properties of some commonly used refrigerants and oils as well as their classifications are stated. Due to the absence of a ventilator, a special heat exchanger was designed to achieve the required heat power. The choice of components in this refrigeration system takes into consideration the efficiency and functionality of the device.

Voltage imbalance in low voltage (LV) networks is expected to deteriorate as low carbon technologies, e.g. electric vehicles (EVs) and heat pumps (HPs) are increasingly deployed. The new electrical demand attributable to EVs and HPs would increase the voltage magnitude variation, increasing the possibility of voltages moving outside the statutory LV magnitude limits. Moreover, the single-phase nature of EVs and HPs, which will be connected via a single-phase 'line & neutral' cable to a 3-phase four-wire LV mains cable buried beneath the street, further entangles this voltage management problem; the non-balanced voltage variations in the three phases boost the levels of voltage imbalance. Excessive voltage imbalance and magnitude variation need to be mitigated to limit their adverse effects on the electric network and connected plant. The voltage imbalance in LV networks is conventionally reduced by reinforcing the network, generally at a high cost. Some modern methods for voltage imbalance mitigation have been introduced in recent years. The power electronic converter based methods are inadequate due to the generation of harmonics, significant power losses and short lifetime. Besides, automatic supply phase selection and smart EV charging rely on an advanced smart communication system, which currently is not available. This project aims to develop alternative solutions that mitigate the voltage imbalance seen in LV networks. A voltage balancing method based on Scott transformer (ST) is proposed. This method does not generate harmonics and is independent of the smart communication system. Computer simulations demonstrated the proposed method is able to convert a non-balanced 3-phase voltage into a balanced 3-phase voltage at either a point on the LV feeder or a 3-phase load supply point with the predefined voltage magnitude. Besides, a physical voltage balancing system was created based on the proposed method and it was tested in an LV network in the laboratory. The test results show the balancing system is capable of maintaining a low level of voltage imbalance on the LV feeder by rapidly compensating for the voltage rises and sags caused by single-phase load variations. This voltage balancing method is a potential solution for the network utilities to accommodate the significant penetration of low carbon technologies without breaching the network voltage limits. The impact of EVs and HPs on the LV network voltages is investigated based on a Monte Carlo (MC) simulation platform, which comprises a statistical model of EV charging demand, profiles generators of residential and HP electrical demand, and a distribution network model. The MC simulation indicates the impact of EVs and HPs is related to their distribution; when more than 21EVs and 13HPs are non-evenly distributed on a 96-customer LV feeder, the voltage limits are likely to be violated. Moreover, the effectiveness of the ST based voltage balancing method and the demand response based TOU tariff, implemented either alone or together, in mitigating the impact of EVs and HPs is investigated based on the established MC simulation platform. The results indicate the ST based balancing method alone is able to completely mitigate the voltage limit violations regardless of the penetration levels of EVs and HPs. Moreover, using both of the two investigated methods further enhances the balancing effectiveness of the ST based voltage balancing method.

2008-05-26

Bedrock heat as an energy source

The sun has warmed up the bedrock and this heat can be used for warming up houses. Approximately 100 – 200 meters down in the bedrock the temperature of the heat is stable. This is a source of energy that can be used by installing a heat pump system. The ground source heat pumps are low maintenance and can last for many years. There is also a pollution risk for the groundwater and therefore the wells in the area. Before the ground source heat pump can be installed the municipality need to give permission, according to the environmental code. To install the system without permission is a crime against the environmental code. A requirement when applying for permission to install the heat pump system is to get the neighbours to agree with the place for the bore hole. The neighbour can appeal against the environmental and health authorities’ decision to give permission to install the ground source heat pump system. However there needs to be more research done regarding the environmental effects that may occur in the future, if the ground source heatpump system continues to increase as rapidly as today.

This diploma thesis deals with the issue of heat pumps as devices using low-potential heat of the surrounding environment for heating of buildings. In the theoretical part of the thesis there are described various types of these devices, the sources of low-potential heat and the possibilities of heat energy accumulation. The practical part of the thesis is focused on processing and evaluation of operational data of air/water heat pump used for heating of family house and assessment of importance of accumulation tank in heating system. Part of the thesis is also a proposal of optimization of heat pump control.

The aim of this thesis is to design a low temperature heating system which will be operating in multifunctional wooden house. Ground souce heat pump being the pruducer of the energy in this systém, while the underfloor heating.being the consumer. After a short brief on theoretical level of used systems and devices, there comes a practical part of equations, designing and finding of a best solutions for all necessary parts of heating system. All imporant generated data are packed in a lucid charts. Thesis is trying to be somewhat brief but factical, and just a little bit stylish. At the end of the work there are some economical conclusions of used system like annual energy consumption cost, payback periods comparisons to other systems etc.

La present tesi realitza un estudi experimental de l'procés de desorció de la barreja CO2 / acetona en un intercanviador de calor de plaques. S'ha realitzat una revisió bibliogràfica de la demanda energètica a nivell industrial per a identificar rangs de temperatures en els quals pot implementar la tecnologia de bomba de calor. El cicle de bomba de calor per compressió / resorció es defineix com una alternativa factible per a l'aprofitament de calor residual a baixa i mitja temperatura (30 - 60ºC) fins a temperatures útils per a processos industrials (> 80ºC). Es realitza la modelització de propietats termodinàmiques de la mescla CO2 / Acetona i de el cicle de bomba de calor per compressió / resorció. Es va realitzar un estudi paramètric de les variables independents i es van obtenir rangs d'operació respecte a pressió, temperatura i composició en els quals el cicle funciona com a bomba de calor. Es van obtenir resultats de l'eficiència de l'cicle i de la relació de cabals. S'han obtingut les condicions d'operació per a dur a terme l'estudi experimental de l'procés de desorció de la barreja en un intercanviador de plaques format per 4 plaques / 3 canals. S'ha dissenyat i construït un equip experimental per caracteritzar el procés de desorció de la barreja CO2 / acetona a l'intercanviador de calor de plaques. S'han obtinguts resultats per al coeficient de transferència de calor de la solució, flux de calor i flux màssic de desorció a l'intercanviador de calor de plaques.
La presente tesis realiza un estudio experimental del proceso de desorción de la mezcla CO2/acetona en un intercambiador de calor de placas. Se ha realizado una revisión bibliográfica de la demanda energética a nivel industrial para identificar rangos de temperaturas en los cuales puede implementarse la tecnología de bomba de calor. El ciclo de bomba de calor por compresión/resorción se define como una alternativa factible para el aprovechamiento de calor residual a baja y media temperatura (30 – 60ºC) hasta temperaturas útiles para procesos industriales (>80ºC). Se realiza la modelización de propiedades termodinámicas de la mezcla CO2/Acetona y del ciclo de bomba de calor por compresión/resorción. Se realizó un estudio paramétrico de las variables independientes y se obtuvieron rangos de operación respecto a presión, temperatura y composición en los cuales el ciclo funciona como bomba de calor. Se obtuvieron resultados de la eficiencia del ciclo y de la relación de caudales. Se han obtenido las condiciones de operación para llevar a cabo el estudio experimental del proceso de desorción de la mezcla en un intercambiador de placas formado por 4 placas/3 canales. Se ha diseñado y construido un equipo experimental para caracterizar el proceso de desorción de la mezcla CO2/acetona en el intercambiador de calor de placas. Se han obtenidos resultados para el coeficiente de transferencia de calor de la solución, flujo de calor y flujo másico de desorción en el intercambiador de calor de placas.
Heat pump technology is an interesting option to recover waste heat at low temperatures (40 – 60ºC) and upgrade it to temperatures above 80ºC to meet the heat demand in industrial processes, and thus reduce consumption of primary energy and associated CO2 emissions. Current heat pump technologies are limited by the thermodynamic properties of working fluids and the resistance of their components. Compression/resorption heat pumps using refrigerant/absorbent working fluid mixtures such as CO2/acetone can operate at low high pressures with good performances. This research aims to experimentally study the desorption process in a plate heat exchanger of the CO2/Acetone mixture as an alternative for its use in the compression/ resorption heat pump cycle. The experimental results show values for the heat transfer coefficient (hs) between 0.2 and 0.5 kW/ m2K. An increase in the temperature of the heating water and a low temperature difference between the heating water and the temperature of the solution at the desorber´s inlet enhance the heat transfer. The hs value decreases as the pressure of the experiment increases. The heat transfer in the heat exchanger improves with low mass fractions of CO2 in the CO2/Acetone solution (22 % - 25%). The calculated mean vapour quality reaches a maximum value of 16% at a test pressure of 12 bar. The calculated heat transfer in the heat exchanger is between the 1.5 and 5 kW/ m2 range. The calculated desorption flow is between 0.002 and 0.005 kg/s.

This diploma thesis deals with design of air-water heat pump which uses natural refrigerant, propane. In the thesis there are mentioned various types of devices using the source of low-potential heat for heating. The main part of the thesis is the design of the heat pump cooling circuit. In this section, individual components are designed, the calculation and comparison of the heating factor for different operating parameters is performed. Finally, the construction of the coolant circuit and the air exchanger is designed.

This thesis investigated application of the heat recovery ventilation using an exhaust air heat pump and a roof top photovoltaic (PV) system for a group of three multi-family houses located in Ludvika, Sunnansjö. The buildings in the existing condition have mechanical ventilation and a centralized heating system consists of a pellet boiler as the main source and an oil boiler as back up. Exhaust air heat pump (EAHP) has been known by the previous relevant researches as an effective solution to promote the energy efficiency in the buildings. Furthermore, reduction in PV cost has made the PV as a financially viable option to be contributed in supplying electricity demand. In this respect, this thesis aimed to calculate the potential of energy saving in the case study using the combination of EAHP and PV. For this purpose, the buildings and the proposed energy system were simulated to enable the comparison of energy demand before and after the renovation. The simulation was gradually progressed through several phases and each stage created the prerequisites of the next. Since the buildings were relatively similar in terms of boundary conditions, one of the buildings were initially modeled and the concluded space heating (SH) demand was extrapolated to the three buildings scope. The simulation of the building was done using 3dimensional thermal model offered by Trnsys3d. The primary results were also calibrated against the available annual fuel consumption data. In the second phase, a pre-developed TRNSYS model of the energy system was completed using the result of previous step as the total SH demand as well as the estimated domestic hot water (DHW) consumption from a stochastic model. This simulation produced the electricity demand profile of the heat pump when the heat pump provided the total heat demand. Subsequently, the electricity consumption of the flats and operational equipment were estimated using stochastic model and available monthly measurement, respectively. Since the feasibility and optimal placement of 74 𝑘𝑊 PV modules offered for these buildings had been already examined by the author in another study, the final simulation were performed in an hourly basis considering PV production and total electricity demand; i.e. EAHP, flats consumption and operational equipment. The results of the simulation showed that 21 % of total electricity demand during a year could be supplied by the proposed PV system even without any electrical storage, whereas 74 % of total yearly PV production is consumed by the local loads. The results also proved that removing old inefficient oil boiler and supplementing the pellet boiler with the combination of EAHP and PV could mitigate the annual purchased energy (including electricity and pellet) by approximately 40 % compared to the current condition.

The high energy use in the European building stock is attributable to the large share of old buildings with poor energy performance. Energy renovation of buildings is therefore vital in the work towards energy efficiency and reduced environmental impact in the EU. Yet, the strategies and energy system implications of this work have not been made clear, and the rate of building renovation is currently very low. The aim of this thesis is to investigate the economic and environmental aspects of energy renovation strategies, with two main objectives: Renovation of Swedish district heated multi-family houses, including life-cycle cost and environmental analysis and impact on the local energy system; Renovation of European residential and office buildings, including life-cycle cost and environmental analysis and influence of climatic conditions. Buildings typical for the respective regions and the period of construction 1945-1970 were simulated, in order to determine the feasibility and energy saving potential of energy renovation measures in European climates. A variety of systems for heating, cooling and ventilation were studied, as well as solar energy systems, with focus on heat pumps, district heating, low-temperature heating systems and air heat recovery. Compared to normal building renovation, energy renovation can often reduce the life-cycle costs and environmental impact. In renovation of typical European office buildings, as well as Southern European multi-family houses, more ambitious renovation levels can also be more profitable. Exhaust air heat pumps can be cost-effective complements in district heated multi-family houses, while ventilation with heat recovery is more expensive but also more likely to reduce the primary energy use. From a system perspective, simple exhaust ventilation can reduce the primary energy use in the district-heating plant as much as an exhaust air heat pump, due to the lower electricity use.
Byggnadssektorn står för omkring 40 % av den totala energianvändningen i EU. Den höga energianvändningen i Europeiska byggnader kan till stor del tillskrivas den stora andelen gamla byggnader med dålig energiprestanda. Energirenovering av byggnader, eller energieffektivisering genom renovering, kan därför anses utgöra en central del i arbetet mot EU:s klimat- och energimål för år 2030. Trots detta är det ännu inte helt klarlagt vilka strategier som ska tillämpas för att uppnå detta och hur det påverkar energisystemet, och i nuläget är renoveringstakten fortfarande väldigt låg. Målet med denna avhandling är att undersöka ekonomiska och miljömässiga aspekter av strategier för energirenovering, såväl byggnadsskalsåtgärder som aktiva system, för typiska bostads- och kontorsbyggnader i Sverige och i andra Europeiska regioner. Mer specifikt har arbetet följande två inriktningar: Renovering av svenska, fjärrvärmevärmda flerfamiljshus, inklusive livscykelkostnadsanalys och livscykelmiljöanalys samt påverkan på det lokala energisystemet; Renovering av Europeiska bostads- och kontorsbyggnader, inklusive livscykelkostnadsanalys och livscykelmiljöanalys samt påverkan av klimatförutsättningar. Byggnader typiska för respektive region och byggnadsperioden 1945-1970 modellerades och användes i simuleringar för att fastställa den övergripande möjligheten och energibesparingspotentialen för olika renoveringsåtgärder i Europeiska klimat. En rad system för värme, kyla och ventilation studeras, samt solenergisystem, med fokus på värmepumpar, fjärrvärme, lågtemperaturvärmesystem och värmeåtervinning ur frånluft. Jämfört med renovering av byggnader utan energieffektiviseringsåtgärder kan energirenovering i många fall minska såväl livscykelkostnaden som miljöpåverkan. Vid renovering av typiska Europeiska kontorsbyggnader lönar det sig mer att renovera ner till ett uppvärmningsbehov på 25 kWh/(m²∙år) än 45 kWh/(m²∙år), då den minskade kostnaden för köpt energi väger upp den ökade kostnaden för isolering. För flerfamiljshus i södra Europa kan mer ambitiösa mål gällande värmebehov också vara lönsamma, medan en mer måttlig nivå är lämplig för småhus. Solvärme- eller solelsystem kan användas för att minska byggnaders miljöpåverkan. Utan subventioner eller inmatningstariff för överskottsel kan det bli svårt att få lönsamhet i dessa system för kontorsbyggnader i Nord- och Centraleuropa samt för småhus. För flerfamiljshus kan solenergisystem dock sänka den totala livscykelkostnaden, såväl i södra som i norra Europa. Värmeåtervinning och lågtemperaturvärmesystem visade sig båda ha större inverkan i kallare klimat. Lågtemperaturvärmesystem förbättrar värmefaktorn för värmepumpar, i synnerhet när uppvärmningsbehovet är stort i förhållande till varmvattenbehovet. Vid renovering av byggnader med vattenburna radiatorer kan konvertering till tilluftsradiatorer sänka framledningstemperaturen i värmesystemet. I svenska flerfamiljshus kan frånluftsvärmepump vara ett kostnadseffektivt komplement till fjärrvärme, medan från- och tilluftsventilation med värmeåtervinning är dyrare men mer sannolikt att ge en minskad primärenergianvändning. I ett systemperspektiv kan frånluftsventilation utan värmeåtervinning minska primärenergianvändningen i fjärrvärmeverket lika mycket som en frånluftsvärmepump, tack vare den lägre elanvändningen.

QC 20170509

iNSPiRe

Le travail présenté ici a pour objectifs d’étudier et d’optimiser les performances énergétiques d’un chauffe-eau thermodynamique couplé à un stockage par chaleur sensible. La ressource utilisée consiste en la récupération de chaleur sur l’air extrait d’un logement de type collectif. L’enjeu est de caractériser les conditions dans lesquelles le système est capable d’assurer les besoins avec des performances requises lorsque les conditions aux limites sont très fluctuantes. Sur le plan fonctionnel, le système doit être le plus simple possible du point de vue de sa configuration hydraulique et de sa stratégie de régulation.Pour cette étude, nous avons développé un modèle physico-corrélatif sur TRNSYS pour simuler et analyser les différents scenarios et les couplages thermohydrauliques entre les composants du système. En parallèle de cette démarche de modélisation, nous avons conçu et mis en œuvre un dispositif expérimental à l’échelle 1 à des fins de validation du modèle sur une large plage de conditions opératoires.L’analyse des résultats, notamment sur la nature des écoulements au sein du ballon de stockage, a mis en évidence l’influence majeure d’un certain nombre de paramètres sur les performances du système. En particulier, la robustesse des performances face à des fluctuations importantes des conditions aux limites peut être assurée grâce à une stratégie de régulation adaptée.Cette étude a finalement conduit à proposer un modèle réduit pour le dimensionnement du système qui prend en compte les paramètres le plus pertinents pour la stratégie de régulation
The work presented here aims to study and optimize the energy efficiency of a heat pump water heater coupled with a sensible heat storage. The resource used consists of heat recovery from exhaust air of a collective type of housing. The challenge is to characterize the conditions in which the system is capable of ensuring the needs with performance required when the boundary conditions are very volatile. Functionally, the system should be as simple as possible from the viewpoint of its hydraulic configuration and its control strategy.For this study, we developed a TRNSYS numerical model to simulate and analyze different scenarios and thermal hydraulic couplings between the system components. In parallel with this modeling approach, we designed and implemented an experimental set up with realistic scale to validate the model over a wide range of operating conditions.The analysis of the results, including the nature of flows within the storage tank, highlighted the major influence on a number of parameters on the system performance. In particular, the robust performance in the face of significant fluctuations of the boundary conditions can be ensured through appropriate control strategy.This study eventually led to propose a model for the design of the system that takes into account the most relevant parameters for the control strategy

This master´s thesis addresses heating of the new three - storey office building, which is located in Brno Pisárky. The heating system is designed as a low-temperature system with forced circulation of water using mostly panel radiators. As the heat source was designed two variants. The first heat source is the heat pump air - water, which is installationed inside. The second heat source is a gas condensing boiler. The part of design is preparation hot water. Ventilation of the building is equal-forced. Experimental part of master´s thesis is focused on measuring the amount of electricity produced per year by photovoltaic panels on the existing house in Brno Pisárky. Thesis also includes measuring outdoor temperature and intensity of solar radiation. The result is a comparison of the need for electricity for the heat pump for heating family house, total electricity consumption family house and amount of electricity produced by photovoltaic panels.

This master thesis describes the design of heating in a new one-storey nursery school in Kuřim. The heating systém is designed as a low-temperature systém with a forced circulation of water and a horizontal piping. Three kinds of radiators are used in the design. The panel radiators, tube radiators and free-standing convectors. In this project there are two varinats of the heat source for buliding. The first variant is two gas condensing boilers and the second variant is two heat pumps of an air/water split design. The disign includes air heating in the unit of air conditioning and hot water preparation. The experimental part of the master thesis is focused on microbial microclimate in buildings and radiators contamination by microorganisms. It contains four different experiments, their realization, results and evaluation.

The diploma thesis is divided into three parts. The first part is theoretical devoted to the introduction of BETONG building material. And next It is also devoted to themes of low - energy buildings and nearly zero-energy buildings, heat sharing and thermal comfort. In the second part is the concept of the heating system elaborated in three variants of the design in the scope of the study for the new family house. The third part is devoted to use of shell blocks of the BETONG with internal contact insulation compared to other masonry systems.

The aim of this thesis is to elaborate project documentation for new construction of low-energy residential building with 16 luxury apartments, apartment without barriers and with pharmacy of basic type. It is a four-storey detached building without basement, with flat roof, roof terraces and with balconies. Residential building is located in one of the most enjoyable parts of the city of Zlín – Jižní Svahy II in the vicinity of Central park with bicycle path and with beautiful view of the Zlín. The building will be located on land plot No. 2144/46, where is still situated unfinished building "Torso" from the late 80 years. The residential building is designed in brick system Heluz, ceiling construction is made up of prestressed hollow core slabs, perimeter walls are with external thermal insulation composite system and external doors and windows are made of plastic and aluminum with triple glazing. For heating and water heating will be utilized renewables energy, such as heat pump and solar collectors. Residential units with three residential rooms are designed with a forced ventilation by means of ventilation units with heat recovery. The building also uses modern shielding elements such as outdoor blinds and horizontal sun breakers. The part of the project are also disposition studies, seminar work and energy part.

Water energy is essential for economic expansion and human development. Social progress and economic growth depend on meeting water energy needs sustainably. The use of non renewable energy sources for pumping water to high heads from a low head (surface flow or groundwater) has led to a global imbalance, leaving society vulnerable to an uncertain future. The thesis aims to bypass electrical energy for pumping water in a niche region of people near river basins, promoting interdependence and minimizing consumption. Technical engineering solutions applied in this work use the flow from rivers or streams as their primary input energy sources to pump 5 to 10 percent of the water needed for sustenance at higher elevations while returning 90 to 95 percent of the water that is used for pumping back to the stream. This endeavour has the potential to assist around 5% of the world's population who currently live along the river basins. The Taipadar village case study is illustrated, which is situated in the Tiriya river basin of the Chhattisgarh state, Bastar, in central-east India, to demonstrate the implementation of such technical solutions in the real world. The emphasis is given to the effectiveness of converting two hydraulic powers: input river flow and head and output delivered flow and delivery head. Afterward, in this research, the two appropriate engineering solutions of the Taipadar village, namely the Ram pump and Turbine pump, have been examined for their best performance, and monograms have been created to enable technicians and field personnel to develop their customized systems. A detailed comparison of two technologies (i.e., Ram pump and Turbine pump) is made with a discussion of their working principles and the results of tests conducted at a field station in central-east India. The H-Q-D (Head-Discharge-Diameter) chart is also developed to serve as a helpful tool for interpreting the technology concerning boundary circumstances and serves as a roadmap for upcoming innovations in such renewable hydro pumping devices. It is crucial to investigate the technologies' combined or individual overall optimum performance for the system design. To gain insights into the performance of the turbine pump, its blade geometry, represented by the blade thickness to chord length ratio (t/l), is analysed. This study on t/l highlights its effect on the specific speed of the turbine and, therefore, the pumping efficiency. This comprehensive work on t/l is a novel area of investigation that has been previously ignored or overlooked, but its findings have opened up new avenues for optimizing the performance of hydro turbines. The scaling effect of axial flow propellers while maintaining a constant t/l ratio, as well as varying chord lengths and blade numbers, is also addressed. A comprehensive qualitative theory of energy transfer and corresponding loss mechanisms is also provided, along with an analytical method. Moreover, in order to examine the performance of a hydraulic ram, this study analysed the stroke rate of the impulse valve, as well as the valve setting, drive head, and length, using two analytical models. These models (i.e., Tacke and Iversen) have validated the results that show good conformance with matching delivered flow. The analysis of the effect of control variables on input variables demonstrates that the field setup outperformed the lab setup. 4 The thesis, in the end, will provide the fundamentals, design, conceptualization, construction, evaluation, and field validation guidelines for implementing low-head micro hydro pump technologies to deliver water, generate electricity, and, most notably, convince society and policymakers to shift their current reductionist approach. The scaling and design of the turbine pump, pump selection, and flow output estimation with a technical-economic feasibility study procedure are also discussed.

碩士
國立屏東科技大學
機械工程系
92
The traditional drying methods adopted for agricultural products are commonly fire-based or electricity-based, more specifically, using high temperature between 50~120℃ to dry agricultural products. In general, those methods are energy consuming, costly, pollutant, fire hazardous, and short in product life. Therefore, this study aims to develop a heat-pump low-temperature dehumidifying dryer (operating at temperature between 10~55℃) for energy saving and safety purposes. The concept of this dryer is based pm replacing the freezing compressor with the traditional diesel or electric heater inside a dryer, then condensing and recycling the thermal energy contained in the air discharged in a drying room as the heating energy. Such method can save a considerable amount of energy. The features of the heat-pump low-temperature dehumidifying dryer developed by this study are as follows: 1. The variation of wind velocity of upper and lower layer is between 0.1~0.3m/s. 2. The operating temperature is between 10~55℃ and the drying time is between 2.5-4 hours. 3. The single-dot temperature variation of the temperature change in the dryer can be controlled within 1℃; operating under 50℃±3℃, the difference of high and low temperatures can be controlled within 5.0℃ with average temperature difference at 0.97℃ and the standard deviation of temperature is 0.28. 4. The humidity of the dryer is between10%RH~95%RH; and drops from58.4% to 10%RH when the temperature increases to 49℃; and between 10.1%RH~40.9%RH when the temperature drops from 47℃ to 10℃. Furthermore, the heat-pump low-temperature dehumidifying dryer had undergone larval fish drying experiment. The results showed that: 1. The ideal temperature for drying larval fish is between 32℃~38℃ for time span of 2.5~4.0 hours; if the thickness of fry stack is between 1~2cm, the water content after drying is between 12.95~18.25%; 2. Compared with hot-air dryer, the physiology, water activity, color change, fatty acid valence, and VBN of the larval fish dried by heat-pump low-temperature dehumidifying dryer prevailed; 3. Evaluation on the larval fish production over one year of fishing season in Finagling showed that the profitability of larval fish dried with the heat-pump low-temperature dehumidifying dryer can surpass the larval fish dried with the traditional freezing or steam-dried larval fish. According to measurements of dry bulb temperature and absolute humidity, and the mutual proof supported by the thermodynamic equation and air-humidity curve, the dryer developed by this study carried respectable credibility, applicability, and validity, as well as values in practical utility. In future, improvements on the variance in wind direction and velocity can extend its applicable fields.

碩士
國立臺灣大學
電機工程學研究所
96
Static random access memory (SRAM) has its own name known loud and clear in the hood of the high speed memory applications. From the level 2 (L2) caches in the gigahertz multi-core central processing units (CPUs), level 3 (L3) caches in the high speed switches, hubs and network servers to the embedded uses such as the liquid crystal display (LCD) driver ICs, system-on-a-chips (SoCs) and cell phone integrations, SRAM works all. It aims to the field of the high speed data rate use in a rather smaller memory size in both memory capacity and die area with full of the flexibility and integrability. Despite the mostly adopted 6-T memory cell is so classic and seemingly flawless. When talking of the necessarily active area issue then is another story. Less is more, hence we assume the 4-T cell to be the memory core of our design. With the aid of the negative word line scheme, the dramatically increased sub-threshold leakage in the sub-micron technology is then effectively eliminated without using any special process fabrication technology. As to noise, boosting the cell supply voltage gains us a significantly static noise margin (SNM) improved with a little extra power penalty. Meanwhile, the CMOS technology is the chosen one for us with the higher-level system integration and lower-cost manufacturing requirement. Looking forward to be in the way of making it powerful but not power hungry. In this thesis, we propose a SNM improved, low power consumption 1k 4-T SRAM structure with the boosted cell power supply by the proposing voltage heap pump, and the negative word line scheme in order to minimize the stand-by gate leakage current. Further, by proposing a current to voltage type current sense amplifier with Schmitt trigger adds a little help to fight for the noise interference. Simulated in the TSMC 0.18um CMOS process, the SNM of this 1k SRAM circuit is 530mV with the stand-by leakage current about 0.082mA, and consumes only 0.18mW, 9.43mW and 7.38mW in stand-by, read and write, respectively.

This thesis aims to provide an overview of possibilities of using low-potential waste heat produced at the CEZ Temelin Nuclear Power Plant. It also shows current technological possibilities of using low-potential heat sources in the primary form or as a waste by-product in leisure time aquapark, eventually the waste heat used as a source of central heat system supply victim village.

Кравченко С. І. Аналіз можливості використання низькопотенційної теплоти для потреб багатоквартирних будинків : кваліфікаційна робота магістра спеціальності 144 "Теплоенергетика" / наук. керівник О. І. Осаул. Запоріжжя : ЗНУ, 2020. 84 с.
UA : Робота викладена на 84 сторінках друкованого тексту, містить 12 таблиць, 28 рисунків. Перелік посилань включає 40 джерел з них на іноземній мові 1. Особлива увага приділена низькопотенційним поновлюваним джерелам енергії відхідних вентиляційних газів багатоповерхових будинків. Для визначення можливого потенціалу та економічного обґрунтування доцільності використання таких джерел енергії, проведено експеримент, у ході якого були визначені температури та величини теплових потоків у шахтах будівель. На підставі виконаних досліджень та розрахунків, розроблено схему утилізаційної установки та підібрано необхідне основне та допоміжне обладнання. відхідних вентиляційних газів багатоповерхових будинків. Для визначення можливого потенціалу та економічного обґрунтування доцільності використання таких джерел енергії, проведено експеримент, у ході якого були визначені температури та величини теплових потоків у шахтах будівель. На підставі виконаних досліджень та розрахунків, розроблено схему утилізаційної установки та підібрано необхідне основне та допоміжне обладнання.
EN : The work is presented on 84 pages of printed text, contains 12 tables, 28 figures. The list of references includes 40 sources, 1 of them in foreign language. Particular attention is paid to low-potential renewable energy sources -exhaust gases of multi- storey buildings. To determine the possible potential and economic justification of the feasibility of using such energy sources, an experiment was conducted, during which temperatures and heat fluxes in the mines of buildings were determined. On the basis of the performed researches and calculations, the scheme of the utilization installation is developed and the necessary basic and auxiliary equipment is selected.