Dissertations / Theses on the topic 'Energy Systems Integration'

This thesis concerns the design, implementation and operation of a hydrogen energy storage facility that has been added to an existing renewable energy system at West Beacon Farm, Leicestershire, UK. The hydrogen system consists of an electrolyser, a pressurised gas store and fuel cells. At times of surplus electrical supply, the electrolyser converts electrical energy into chemical energy in the form of hydrogen. This hydrogen is stored until there is a shortage of electrical energy to power the loads on the system, at which point it is reconverted back to electricity by the process of reverse-electrolysis that takes place within a fuel cell. The renewable energy sources, supplying electrical power to domestic and office loads at the site, are photovoltaic, wind and micro-hydroelectric. This work is being carried out through a project, conceived and overseen by the author, known as the Hydrogen and Renewables Integration (HARI) project. The purpose of this study is to demonstrate and gain experience in the integration of hydrogen energy storage with renewable energy systems and, most importantly, to develop software models that could be used for the design of future systems of this type in a range of applications. Effective models have been created and verified against the real-world operation of the system. These models have been largely completed, although some minor details remain unfinished as the are dependant upon studies linked to this one which are yet to be concluded. Subject to some fine tuning that this would entail, then, the models can be used to design a stand-alone, integrated hydrogen and renewable energy system, where only the load profile and weather conditions of a site are known. Significant practical experience has been gained through the design, installation and two years' of operation of the system. Many important insights have been obtained in relation to the integration of the system and the design and operation of its components.

Many countries are advancing down the road of electricity privatization, deregulation, and competition as a solution to their growing electricity demand and other challenges posed by the monopolistic nature of the existing structure. Presently, Nigeria has a supply deficit of electricity as a result of the growing demand. This imbalance has negatively affected the economy of the country and the social-economic well-being of the population. Hence, there is an urgent need to reform the power sector for greater efficiency and better performance. The objectives of the reform are to meet the growing power demand by increasing the electric power generation and also by increasing competitiveness through the participation of more private sector entities. The renewable energy integration is one way of increasing the electricity generation in the country in order to cater for the growing demand adequately. Examples of the renewable energy that is available in the country include wind, geothermal, solar and hydro. They are considered to be environmentally friendly, replenishable and do not contribute to the climate change phenomena. The country presently generates the bulk of its electricity from both thermal (85%) and hydroelectric (15%) power plants. While electricity generation from the thermal power stations constitutes the largest share of greenhouse emission, this is mostly from burning coal and natural gas. The effect of this high proportion of greenhouse emission causes climate change which is referred to as a variation in the climate system statistical properties over a long period of time. It has been observed that many of the activities of human beings are contributory factors to the release of these greenhouse gases (GHG). But, as the traditional sources of energy continue to threaten the present and future existence on the planet earth, it is, therefore, imperative to increase the integration of the variable renewable energy sources in a sustainable and eco-friendly manner over a long period of time. The variability and the uncertainties of the renewable energy source's output, present a major challenge in the design of an efficient electricity market in a deregulated environment. The system deregulation and the use of renewable sources for the generation of electricity are major changes presently being experienced in power system. In a deregulated power system, the integration of renewable generation and its penetration affects both the physical and the economic operations. The main focus of this research is on the integration of wind energy into Nigerian power systems. Up till now, research on the availability of the wind energy and its economic impacts has been limited in Nigeria. Generally, the previous study of wind energy availability in Nigeria has been limited in scope. The wind energy assessment study has not been detailed enough to be able to ascertain the wind energy potential of the country. To cope with this shortcoming, a detailed statistical wind modeling and forecasting methodology have been used in this thesis to determine the amount of extractable wind energy in six selected locations in Nigeria using historical wind speed data for 30 years. The accuracy test of the statistical models was also carried using the Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and Chi-Square methods to determine the inherent error margin in the modeling and analysis. It is found that the error margin of the evaluations falls within the expected permissible tolerance range. For a more detailed wind assessment study of the Nigeria weather, the seasonal variation of the weather conditions as it affects the wind speed and availability during the two major seasons of dry and rainy was considered. A Self-Adaptive Differential Evolution (SADE) was used to solve the economic load dispatch problem that considers the valve-point effects and the transmission losses subject to many constraints. The results obtained were compared with those obtained using the "standard" Differential Evolution (DE), Genetic Algorithm (GA), and traditional Gradient Descent method. The results of the SADE obtained when compared with the GA, DE, and Gradient descent show the superiority of SADE over all the other methods. The research work shows that the wind energy is available in commercial quantity for generation of electricity in Nigeria. And, if tapped would help reduce the gap between the demand and supply of electricity in the country. It was also demonstrated that the wind energy integration into the power systems affects the generators total production cost.

The boom experienced by renewable sources in recent years has changed their consideration as a marginal component of the electrical system mix into a major player with an important role in the demand coverage in many countries. Regarding the PV technology, its weight within the electrical systems in countries such as Germany, Spain and Japan suggests that integration problems may arise if the current installation trends are maintained. Most of these problems are connected to one of its main handicaps: its stochasticity and its high level of intermittency, both characteristics clearly dependent on weather. This work is dedicated to the analysis of one possible solution to achieve a higher penetration rate of the photovoltaic technology in the grid which is, according to the literature, the introduction of an energy storage system in parallel with PV plants. The ultimate objective in the study reported in this Thesis dissertation is to provide PV power plants with the ability to generate solar energy in a controlled and, if possible, constant way so that these could access both the day and intraday electricity markets. The analysis of the storage system characteristics , focusing the interest on the amount of energy and power that this system would require when operating the photovoltaic plant in accordance with a specific energy management strategy while avoiding saturations, requires a good knowledge of solar resource. At present, there has not been any major and exhaustive campaign to measure the radiation with sampling periods below 15 minutes. Therefore, the solar resource can only be estimated by using statistically-based data and weighted averages. These data come from sources in the space (satellites) and from meteorological stations in the Earth's surface. This work uses information extracted from one of the most accepted solar radiation databases, the PVGIS database developed by the European Union. Moreover, real data measured in a particular place in the south of the Iberian Peninsula, where the analysis of the energy storage requirements has been centered, are also used. Both data sets have been cross validated in order to verify their credibility and agreement degree. On the other hand, there are multiple energy storage technologies that can be currently identified as potential candidates to be included in photovoltaic power plants to integrate future hybrid plants with controlled production. A review of these technologies, along with a description of their main features highlighting their strengths and limitations, is included in this Thesis work. Using the comparison as a method, which has been performed considering various factors associated to the storage technology itself (geographical dependence, state of development, energy and power rated levels achieved by each technology) but also taking into account the operation conditions at which the storage will be subject in a photovoltaic power plant, one technology is highlighted as the candidate to be used in this application. Finally, this Thesis proposes various energy management strategies to control power production in photovoltaic power plants integrating an energy storage system. Some of these strategies are directed to incorporate the plant to the electricity market while others simply pretend to reduce the variability of the production. For each of them, an estimate of the energy storage system required energy capacity has been obtained. These estimates allow having a rough approximation of the energy requirements, as well as an estimate of the additional cost, that this solution would imply. Among the various energy management configurations proposed, some of them provide results technically feasible on the one hand and, on the other hand, also interesting outcomes from an economic point of view, as the regulatory framework governing the electricity markets becomes gradually adapted to the new and evolving reality of the electric power system.

The objective of this work was to develop a systematic methodology for simultaneously targeting and optimizing heating, cooling, power cogeneration, and waste management for any processing facility. A systems approach was used to characterize the complex interactions between the various forms of material and energy utilities as well as their interactions with the core processing units. Two approaches were developed: graphical and mathematical. In both approaches, a hierarchical procedure was developed to decompose the problem into successive stages that were globally solvable then. The solution fragments were then merged into overall process solutions and targets. The whole approach was a systems approach of solving problems. The methodology was developed from the insights from several state of the art process integration techniques. In particular, the dissertation introduced a consistent framework for simultaneously addressing heat-exchange networks, material-recovery networks, combined heat and power, fuel optimization, and waste management. The graphical approach relied on decomposing the problem into sequential tasks that could be addressed using visualization tools. The mathematical approach enabled the simultaneous solution of critical subproblems. Because of the non-convexity of the mathematical formulation, a global optimization technique was developed through problem reformulation and discretization. A case study was solved and analyzed to illustrate the effectiveness of the devised methodology.

Small-scale, residential, and distributed energy resources (DER), which are electric vehicles (EVs), heat pumps (HPs), and photovoltaic (PV) arrays, were studied to evaluate their impact on the UK future residential demand and their impact on UK distribution networks. Centralized and decentralized controllers were planned in order to defer reinforcement, while connecting DER units to distribution networks. The centralized controller allocates EV charging durations considering network constraints. The decentralized controller adjusts EV and HP loads based on consumer satisfaction, network constraints, and electricity prices. Normal probability distribution and median filter were used to predict aggregated power of EVs, HPs, and PV arrays on a half-hourly basis over a year. Because of an expected surplus of PV power generation, a considerable demand reduction followed by a sharp demand increase will occur with these residential DER units during summer days in 2035. A low voltage section of test network was used to study the impact of uncontrolled EV charging loads on a three-phase four-wire system. Different combinations of EVs, HPs, and PV arrays were used to investigate their uncertainties in a low voltage section of real network. Real-world trials were used to generate the individual power of residential customers and DER units. Results of unbalanced power flow indicated that network constraints exceeded their limits with a high number of these low carbon technologies. Using an extended section of the test network, the central controller maintains voltage magnitudes, voltage unbalance factors, and power flows within their limits, by re-allocating EV charging durations accordingly. The decentralized controller was designed to minimize electricity bills of EV and HP users. This controller adjusts EV and HP loads to maintain consumer satisfaction and network constraints within their specified boundaries. Consumer satisfaction was determined using mathematical models of EV battery state-of-charge levels and the indoor temperatures of HP houses. The decentralized controller was used to connect predicted numbers of EVs and HPs to a real distribution network, while overcoming the need for network reinforcement, third parties (aggregators), and extensive communication systems.

Food retail with large supermarkets consumes significant amounts of energy. The environmental impact is also significant because of the indirect effect from CO2 emissions at the power stations and due to the direct effect arising from refrigerant leakage to the atmosphere. The application of trigeneration (local combined heat, power and refrigeration) can provide substantial improvements in the overall energy efficiency over the conventional supermarket energy approach of separate provision of electrical power and thermal energy. The use of natural refrigerants such as CO2 offers the opportunity to reduce the direct impacts of refrigeration compared to conventional systems employing HFC refrigerants that possess high global warming potential. One approach through which the overall energy efficiency can be increased and the environmental impacts reduced, is through the integration of trigeneration and CO2 refrigeration systems where the cooling generated by the trigeneration system is used to condense the CO2 refrigerant in a cascade arrangement. This research project investigates experimentally and theoretically, through mathematical modelling and simulation, such a system and its potential application to supermarkets. A small size CO2 refrigeration system for low and medium food temperature applications was designed and constructed to enable it to be integrated with an existing trigeneration system in the refrigeration laboratory at Brunel University to form an integrated trigeneration and CO2 refrigeration test facility. Prior to the construction, the design of the system was investigated using mathematical models developed for this purpose. The simulations included the CO2 refrigeration system, CO2 evaporator coils and the integration of the trigeneration and CO2 refrigeration systems. The physical size of the design and component arrangement was also optimised in a 3D AutoCAD model. A series of experimental tests were carried out and the results showed that the medium temperature system could achieve a very good COP, ranging from 32 to 60 due to the low pumping power requirement of the liquid refrigerant. The low temperature system performed with average steady state COP of 4, giving an overall refrigeration system COP in the range between 5.5 and 6. Mathematical models were also developed to investigate the application of the integrated trigeneration and CO2 refrigeration system in a case study supermarket. The models were validated against test results in the laboratory and manufacturers’ data. The fuel utilisation efficiency and environmental impacts of different trigeneration and CO2 refrigeration arrangements were also evaluated. The results indicated that a system comprising of a sub-critical CO2 refrigeration system integrated with a trigeneration system consisting of a micro-turbine based Combined Heat and Power (CHP) unit and ammonia-water absorption refrigeration system could provide energy savings of the order of 15% and CO2 emission savings of the order of 30% compared to conventional supermarket energy systems. Employing a trigeneration system with a natural gas engine based CHP and Lithium Bromide-Water sorption refrigeration system, could offer energy savings of 30% and CO2 emission savings of 43% over a conventional energy system arrangement. Economic analysis of the system has shown a promising payback period of just over 3 years compared to conventional systems.

Securing access to affordable energy services is of central importance to our societies. To do this sustainably, energy systems design should be – amongst other things – environmentally compliant and reconcile with the integrated management of potentially limiting resources. This work considers the role for so-called 'Smart Grids' to improve the delivery of energy services. It deals with the integration of renewable energy technologies to mitigate climate change. It further demonstrates an approach to harmonise potentially conflicting energy, water and land-use strategies. Each presents particular challenges to energy systems analysis. Computer aided models can help identify energy systems that most effectively meet the multiple demands placed on them. As models constitute a simple abstraction of reality, it is important to ensure that those dynamics that considerably impact results are suitably integrated. In its three parts, this thesis extends long-term energy system models to consider improved integration between: (A) supply and demand through Smart Grids; (B) timeframes by incorporating short-term operating constraints into long-term models; and (C) resource systems by linking multiple modelling tools. In Part A, the thesis explores the potential of Smart Grids to accelerate and improve electrification efforts in developing countries. Further, a long-term energy system model is enhanced to investigate the Smart Grid benefits associated with a closer integration of supply, storage and demand-side options. In Part B, the same model is extended to integrate flexibility requirements. The benefits of this integration are illustrated on an Irish case study on high levels of wind power penetrations. In Part C, an energy model is calibrated to consider climate change scenarios and linkages with land-use and water models. This serves to assess the implications of introducing biofuels on the small island developing state of Mauritius. The thesis demonstrates that too weak integration between models and resource systems can produce significantly diverging results. The system configurations derived may consequently generate different – and potentially erroneous – policy and investment insights.
Säker och prisvärd tillgång till energitjänster är en central fråga för dagens samhällen. För att tillgodose samhällen med hållbara energitjänster bör energisystemen designas för att – bland annat – möta de miljömässiga kraven samt hantera potentiellt begränsade resurser. Den här avhandlingen undersöker de ”smarta” elnätens roll för bättre tillhandahållande av energitjänster. Avhandlingen behandlar integration av förnybar energiteknik för minskad klimatpåverkan samt demonstrerar ett tillvägagångssätt för att förena potentiellt motstridiga energi-, vatten- och markanvändningsstrategier. Dessa uppvisar särskilda utmaningar i energisystemanalyser. Datorstödda modeller kan användas för att identifiera energisystem som på effektivast sätt möter samhällets krav. Datorstödda modeller är, per definition, förenklingar av verkligheten och det är därför viktigt att säkerställa en korrekt representation av det verkliga systemets dynamik. Den här avhandlingen förstärker energisystemmodeller för långsiktsprognoser utifrån tre aspekter: förbättra integrationen av (A) tillgång och efterfrågan genom smarta elnät; (B) olika tidsaspekter genom att inkludera kortsiktiga operativa begränsningar; samt (C) resurssystem genom att sammanlänka olika modelleringsverktyg. I del A utforskades de smarta elnätens potential för att förbättra elektriska system i utvecklingsländer. En befintlig energisystemmodell förstärktes för att behandla smarta elnät och kan därmed fånga fördelarna förknippade med energilagring och energianvändning. I del B utvidgades en energisystemmodell för långsiktsprognoser med flexibilitet för kortsiktiga operativa begränsningar. En fallstudie fokuserad på ett vindkraftsdominerat irländskt elnät genomfördes för att demonstrera fördelarna av modellutvecklingen. I del C kalibrerades en energisystemmodell för att ta klimatscenarier i beaktande samt energisystemets kopplingar till markanvändning och vattenresurssystem. En fallstudie fokuserad på Mauritius energisystem genomfördes för att undersöka konsekvenserna av en potentiell introducering av biobränslen. Avhandlingen demonstrerar att undermålig integration av energimodeller och resurssystem kan leda till avsevärda avvikelser i resultaten. Slutsatser som dras utifrån dessa resultat kan därmed leda till vitt skilda – och potentiellt felaktiga – underlag för investeringar och energipolitiska rekommendationer.

QC 20131118

Alongside other photovoltaic technologies, Concentrator photovoltaics (CPV) capitalise on the recent progress for high-efficiency III:V based multi-junction photovoltaic cells, combining them with low cost optics for increased power production. Thermoelectrics are semiconductor devices that can act as solid-state heat pumps (Peltier mode) or to generate electrical power from temperature differentials (Seebeck effect). In this work, new designs for the integration of a thermoelectric module within a CPV cell receiver were proposed and substantiated as a reliable and accurate temperature control platform. The thermoelectric was used for accurate and repeatable cooling, exhibiting high temporal-thermal sensitivity. Testing was done under varying irradiance and temperature conditions. A novel Closed Loop Integrated Cooler (CLIC) technique was tested, demonstrated and validated as a useful experimental metrology tool for measuring sub-degree cell temperature within hybrid devices using the material properties of the thermoelectric module. Proof-of-concept circuitry and a LabVIEW based deployment of the technique were designed built and characterised. The technique was able to detect thermal anomalies and fluctuations present when undertaking an I-V curve, something otherwise infeasible with a standard k or t-type thermocouple. A full CPV-TE hybrid module with primary and secondary optical elements (POE-SOE-CPV-TE) was built using a further optimised receiver design and tested on-sun for evaluation under outdoor operation conditions in southern Spain. A unique TE-based “self-soldering” process was investigated to improve manufacture repeatability, reproducibility and minimise thermal resistance. A manually-tracked gyroscopic test rig was designed, built and used to gain valuable outdoor baseline comparison data for a commercially available CPV module and a Heterojunction Intrinsic Thinlayer (HIT) flat plate panel with the POE-SOE-CPV-TE hybrid device. An energetic break-even between the power consumed by the TE and the power gain of the CPV cell from induced temperature change was experimentally measured. This work demonstrated the unique functionalities a thermoelectric device can improve CPV power generation. The potential of a TEM to improve CPV power generation through active cooling was highlighted and quantified.

Energy systems across the globe are going through a radical transformation as a result of technological and institutional changes, depletion of fossil fuel resources, and climate change. Accordingly, local energy initiatives are emerging and increasing number of the business models are focusing on the end-users. This requires the present centralized energy systems to be re-organized. In this context, Integrated community energy systems (ICESs) are emerging as a modern development to re-organize local energy systems allowing simultaneous integration of distributed energy resources (DERs) and engagement of local communities. With the emergence of ICESs new roles and responsibilities as well as interactions and dynamics are expected in the energy system. Although local energy initiatives such as ICESs are rapidly emerging due to community objectives, such as cost and emission reductions as well as resiliency, assessment and evaluation of the value that these systems can provide to both local communities and the whole energy system are still lacking. The value of ICESs is also impacted by the institutional settings internal and external to the system. With this background, this thesis aims to understand the ways in which ICESs can contribute to enhancing the energy transition. This thesis utilizes a conceptual framework consisting of institutional and societal levels in order to understand the interaction and dynamics of ICESs implementation.  Current energy trends and the associated technological, socio-economic, environmental and institutional issues are reviewed. The developed ICES model performs optimal planning and operation of ICESs and assesses their performance based on economic and environmental metrics. For the considered community size and local conditions, grid-connected ICESs are already beneficial to the alternative of solely being supplied from the grid, both in terms of total energy costs and CO2 emissions, whereas grid-defected systems, although performing very well in terms of CO2 emissions reduction, are still rather expensive. ICESs ensure self-provision of energy and can provide essential system services to the larger energy system. This thesis has demonstrated the added value of ICESs to the individual households, local communities and the society. A comprehensive institutional design considering techno-economic and institutional perspectives is necessary to ensure effective contribution of ICESs in the energy transition.
Energisystem över hela världen går igenom en radikal omvandling till följd av tekniska och institutionella förändringar, utarmning av fossila bränsleresurser och klimatförändringar. Följaktligen växer lokala energiinitiativ fram och ett ökande antal affärsmodeller fokuserar på slutanvändarna. Detta förutsätter att de nuvarande centraliserade energisystemen omorganiseras. I det här sammanhanget utvecklas integrerade samhällsenergisystem (ICES) som en modern utveckling för att omorganisera lokala energisystem som möjliggör samtidig integration av distribuerade energiresurser och engagemang från lokala samhällen. Med framväxten av ICES nya roller och ansvarsområden samt interaktioner och dynamik förväntas i energisystemet. Även om lokala energiinitiativ som ICES snabbt framträder på grund av samhällsmål, såsom kostnad och utsläppsminskningar samt resiliens, bedömning och utvärdering av det värde som dessa system kan ge till både lokala samhällen och hela energisystemet saknas fortfarande. Värdet av ICES-värden påverkas också av de institutionella inställningarna internt och externt för systemet. Med denna bakgrund syftar denna avhandling till att förstå hur ICES kan bidra till att förbättra energiövergången. Denna avhandling använder en konceptuell ram som består av institutionella och samhälleliga nivåer för att förstå samspelet och dynamiken i ICES-genomförandet. Nuvarande energitrender och de därtill hörande tekniska, socioekonomiska, miljömässiga och institutionella frågorna ses över. Den utvecklade ICES-modellen utför optimal planering och drift av ICES och bedömer deras prestanda baserat på ekonomiska och miljömässiga mätvärden. För den ansedda samhällsstorleken och lokala förhållandena är nätanslutna ICES redan fördelaktiga jämfört med alternativet att endast försörjas från nätet, både när det gäller totala energikostnader och koldioxidutsläpp, medan nät-defekterade system, även om de fungerar väldigt bra i termer av minskningen av koldioxidutsläppen fortfarande är ganska dyra. ICES garanterar självförsörjning av energi och kan tillhandahålla viktiga systemtjänster till det större energisystemet. Denna avhandling har visat mervärdet av ICES till de enskilda hushållen, lokalsamhällena och samhället. En omfattande institutionell utformning med hänsyn till de tekno-ekonomiska och institutionella perspektiven är nödvändigt för att säkerställa ett effektivt bidrag från ICES i energiövergången.
Los sistemas energéticos en todo el mundo atraviesan una transformación radical como resultado de cambios tecnológicos e institucionales, el agotamiento de combustibles fósiles y el cambio climático. Por consiguiente, las iniciativas locales de energía están surgiendo y los modelos de negocio se centran cada vez más en los usuarios finales. Esto requiere la reorganización de los actuales sistemas energéticos centralizados. En este contexto, los sistemas integrados de energía comunitaria (ICES, por sus siglas en inglés) están emergiendo como un desarrollo moderno para reorganizar los sistemas energéticos locales, permitiendo la integración simultánea de los recursos energéticos distribuidos y la participación de las comunidades locales. Con la aparición de ICESs se esperan nuevos roles y responsabilidades, así como interacciones y dinámicas, en el sistema energético. Aunque las iniciativas locales en materia de energía, como las ICESs, están surgiendo rápidamente debido a los objetivos de la comunidad, tales como la reducción de costos y emisiones, así como la resiliencia, y la evaluación, siguen careciendo del valor que estos sistemas pueden brindar tanto a las comunidades locales como a todo el sistema energético. El valor de los ICESs también se ve afectado por los entornos institucionales tanto internos como externos al sistema. Con este trasfondo, esta tesis pretende comprender las formas en que los ICESs pueden contribuir a mejorar la transición energética. Esta tesis utiliza un marco conceptual que consiste en niveles institucionales y sociales para comprender la interacción y dinámica de la implementación de los ICESs.  Además, esta tesis revisa las tendencias actuales de energía y los problemas tecnológicos, socioeconómicos, ambientales e institucionales asociados. La tesis desarrolla un modelo que optimiza la planificación y el funcionamiento óptimos de ICESs y evalúa su funcionamiento basado en métricas económicas y ambientales. Para el tamaño de la comunidad y las condiciones locales consideradas, los ICESs conectados a la red ya son beneficiosos tanto en términos de costos totales de energía como de emisiones de CO2 comparado con la alternativa de ser suministrados únicamente desde la red, mientras que los sistemas aislados y desconectados de la red, aunque desempeñándose muy bien en términos de reducción emisiones de CO2, siguen siendo bastante más costosos. Los ICESs garantizan el autoabastecimiento de energía y pueden proporcionar servicios esenciales al resto del sistema energético. Esta tesis demuestra el valor añadido de los ICESs a los hogares individuales, las comunidades locales y la sociedad. Un diseño integral que considere las perspectivas tecno-económicas e institucionales es necesario para asegurar la contribución efectiva de los ICESs en la transición energética.
Energiesystemen over de hele wereld gaan door een radicale transformatie als gevolg van technologische en institutionele veranderingen, uitputting van fossiele brandstoffen en klimaatverandering. Bijgevolg komen lokale energie-initiatieven op en richten steeds meer verdienmodellen zich op de eindgebruikers. Dit vereist dat de huidige gecentraliseerde energiesystemen opnieuw worden georganiseerd. In deze context komen geïntegreerde energiegemeenschapssystemen (ICESs) op als een moderne ontwikkeling om lokale energiesystemen te reorganiseren, welke gelijktijdige integratie van lokale energiebronnen en betrokkenheid van lokale gemeenschappen mogelijk maakt. Het wordt verwacht dat de opkomst van ICESs zowel nieuwe rollen en verantwoordelijkheden met zich meebrengt. Hoewel lokale energie-initiatieven zoals ICESs snel opkomen door de  doelstellingen van de gemeenschap, zoals kosten- en emissiereducties en veerkracht, schort het nog steeds aan beoordeling en evaluatie van de waarde die deze systemen kunnen hebben voor zowel de lokale gemeenschappen als het hele energiesysteem. De waarde van ICESs wordt ook beïnvloed door de institutionele kenmerken binnen en buiten het systeem. Met deze achtergrond beoogt dit proefschrift te begrijpen op welke manieren de ICESs kunnen bijdragen aan de verbetering van de energietransitie. Dit proefschrift maakt gebruik van een conceptueel raamwerk bestaande uit institutionele en maatschappelijke niveaus om de interactie en dynamiek van de implementatie van de ICES te begrijpen. De huidige energietrends en de bijbehorende technologische, sociaal-economische, milieu- en institutionele problemen worden beoordeeld. Het ontwikkelde ICES-model voert optimale planning en gebruik van ICESs uit en beoordeelt hun prestaties op basis van economische en milieu-indicatoren. Voor de beschouwde gemeenschapsgrootte en lokale omstandigheden zijn  op het net aangesloten ICESs al voordelig ten opzichte van het alternatief waarbij uitsluitend vanuit het net wordt geleverd, zowel wat betreft de totale energiekosten als de CO2-uitstoot, terwijl de grid-defected systemen, hoewel heel goed presterend in termen van CO2-emissiereductie, nog steeds vrij duur zijn. ICESs zorgen voor zelfvoorziening van energie en kunnen essentiële systeemdiensten leveren aan het grotere energiesysteem. Dit proefschrift heeft de toegevoegde waarde van ICESs voor de individuele huishoudens, lokale gemeenschappen en de samenleving aangetoond. Een uitgebreid institutioneel ontwerp met inachtneming van techno-economische en institutionele perspectieven is nodig om de effectieve bijdrage van de ICESs in de energietransitie te waarborgen.

QC 20170911

Sustainable Energy Technologies and Strategies

Thesis: S.M. in Technology and Policy, Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2014.
111
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 68-73).
China leads the world in installed wind capacity, which forms an integral part of its long-term goals to reduce the environmental impacts of the electricity sector. This primarily centrally-managed wind policy has concentrated wind development in a handful of regions, challenging regulatory frameworks and grid architectures to cost-effectively integrate wind. In 2013, according to official statistics, wind accounted for 2.7% of national generation, while the rate of curtailment (available wind not accepted by the grid operator onto the system) reached 12%. Wind integration challenges have arisen in China for technical, economic and institutional reasons. From a technology standpoint, the variability and unpredictability of wind resources interact with technical limits of conventional generators, resulting in efficiency losses and grid stability concerns. Existing coal-based electricity and district heating installations play a large role in grid integration challenges because of the inflexible operation of coal plants relative to natural gas and hydropower, and the "must-run" nature of cogeneration units supplying residential heat. A competing set of hypotheses to explain current rates of wind spillage focus on institutional imperfections in China's power sector, such as poorly designed market incentives, inadequate oversight, and a mixture of conflicting policies that are the result of an incomplete transition to a market-driven electricity system. A unit commitment and dispatch optimization was developed to understand the underlying technical factors leading to wind curtailment in northeastern China. It incorporates electricity output restrictions from exogenous district heating demands, a hydro-thermal coordination component considering inter-seasonal storage, and transmission between adjacent provincial nodes. Averaging over six historic wind profiles, a curtailment rate of 6.6% was observed in the reference case from various forms of inflexibility and insufficient demand. The impacts of several technology-based solutions on total cost, coal use and wind curtailment, were also examined: more flexible operation of coal units, temporary heat storage and minimum cogeneration outputs that vary with heat load. Contributing to the existing body of qualitative work on the effects of these factors, this thesis developed a straightforward methodology to assess the relative contribution of regulatory and technical causes. Two important institutional arrangements - the decentralization of dispatch to individual provinces and minimum generation quotas allocated to all coal generators - were quantified in an optimization framework, and found to be significant contributors of power system operational inflexibility.
by Michael Davidson.
S.M. in Technology and Policy

The thesis addresses electronic power distribution systems for the residential applications. Presented are both, renewable energy ac-nanogrid system along with the vehicle-to-grid technology implementation, and envisioned structure and operation of dc-nanogrid addressing all system components chosen as an inherent part of the future electrical architecture. The large-scale model is built and tested in the laboratory environment covering a few operational modes of the ac-nanogrid, while later in the thesis is shown how dc bus signaling technique could be contemplated for the energy management of the renewable energy sources and their maximal utilization. Thesis however puts more focus on the dc-nanogrid system to explore its benefits and advantages for the electrical systems of the future homes that can easily impact not only residential, but also microgrid, grid and intergrid levels. Thus, presented is low frequency terminal behavioral modeling of the system components in dc-nanogrid motivated by the fact that system engineers working on the system-level design rarely have access to all the information required to model converters and system components, other than specification and data given in the datasheets. Using terminal behavioral modeling, converters are measured on-line and their low frequency dynamics is identified by the means of the four transfer functions characteristically used in two port network models. This approach could significantly improve system-level design and simulations. In addition to previously mentioned, thesis addresses terminal behavioral modeling of dc-dc converters with non-linear static behavior showing hybrid behavioral models based on the Hammerstein approach.
Master of Science

This thesis presents advances in integration of photovoltaic (PV) power and energy in practical systems, such as existing power plants in buildings or directly integrated in the public electrical grid. It starts by providing an analyze of the current state of PV power and some of its limitations. The work done in this thesis begins by providing a model to compute mutual shading in large PV plants, and after provides a study of the integration of a PV plant in a biogas power plant. The remainder sections focus on the work done for project PVCROPS, which consisted on the construction and operation of two prototypes composed of a PV system and a novel battery connected to a building and to the public electrical grid. These prototypes were then used to test energy management strategies and validate the suitability of the two advanced batteries (a lithium-ion battery and a vanadium redox ow battery) for households (BIPV) and PV plants. This thesis is divided in 7 chapters: Chapter 1 provides an introduction to explain and develop the main research questions studied for this thesis; Chapter 2 presents the development of a ray-tracing model to compute shading in large PV elds (with or without trackers); Chapter 3 shows the simulation of hybridizing a biogas plant with a PV plant, using biogas as energy storage; Chapters 4 and 5 present the construction, programming, and initial operation of both prototypes (Chapter 4), EMS testing oriented to BIPV systems (Chapter 5). Finally, Chapters 6 provides some future lines of investigation that can follow this thesis, and Chapter 7 shows a synopsis of the main conclusions of this work; Resumo: Avanços na integracão de potência fotovoltaica e producão de energia em sistemas práticos Esta tese apresenta avanços na integração de potência e energia fotovoltaica (PV) em sistemas práticos, tais como centrais existentes ou a rede eléctrica pública. Come ça por analisar o estado corrente do fotovoltaico no mundo e aborda algumas das suas limitações. O trabalho feito para esta tese de doutoramento começou pelo desenvolvimento de um modelo para calcular os sombreamentos que ocorrem em grandes campos fotovoltaicos, e depois apresenta um estudo sobre a integração um sistema fotovoltaico em uma central eléctrica a bióg as. As ultimas secções da tese focam-se no trabalho feito para o projecto PVCROPS, que consistiu na construção e operação de dois demonstratores, cada um formado por um sistema fotovoltaico e bateria conectados a um edíficio e a rede eléctrica pública. Estes protótipos foram posteriormente utilizados para testar estratégias de gestão de energia (EMS) e para validar a operação de duas baterias avançadas (bateria de Iões de Li tio e bateria de Fluxo Redox de Van adio) e a sua utiliza ção para habitações e centrais PV. A tese está dividida em 7 capitulos: O capitulo 1 apresenta uma introdução para explicar e desenvolver as principais questões que foram investigadas nesta tese; O capitulo 2 mostra o desenvolvimento de um modelo baseado em traçados de raios para calcular sombreamentos mútuos em grandes centrais PV (com e sem seguidores); O capitulo 3 mostra a simulação da hibridização de uma central electrica a biogas com uma central PV, e utilizando o biógas como armazenamento de energia. Os capitulos 4 e 5 apresentam a construção, programação e operação inicial dos dois demonstradores (Capitúlo 4), o teste de EMS orientadas para sistemas PV em habitações (Capítulo 5). Finalmente, o capítulo 6 sugere algumas futuras linhas de investigação que poderão seguir esta tese, e o Capítulo 7 faz uma sinopse das principais conclusões deste trabalho.

The demand for cooling and air-conditioning of building is increasingly ever growing. This increase is mostly due to population and economic growth in developing countries, and also desire for a higher quality of thermal comfort. Increase in the use of conventional cooling systems results in larger carbon footprint and more greenhouse gases considering their higher electricity consumption, and it occasionally creates peaks in electricity demand from power supply grid. Solar energy as a renewable energy source is an alternative to drive the cooling machines since the cooling load is generally high when solar radiation is high. This thesis examines the performance of PV/T solar collector manufactured by Solarus company in a solar cooling system for an office building in Dubai, New Delhi, Los Angeles and Cape Town. The study is carried out by analyzing climate data and the requirements for thermal comfort in office buildings. Cooling systems strongly depend on weather conditions and local climate. Cooling load of buildings depend on many parameters such as ambient temperature, indoor comfort temperature, solar gain to the building and internal gains including; number of occupant and electrical devices. The simulations were carried out by selecting a suitable thermally driven chiller and modeling it with PV/T solar collector in Polysun software. Fractional primary energy saving and solar fraction were introduced as key figures of the project to evaluate the performance of cooling system. Several parametric studies and simulations were determined according to PV/T aperture area and hot water storage tank volume. The fractional primary energy saving analysis revealed that thermally driven chillers, particularly adsorption chillers are not suitable to be utilizing in small size of solar cooling systems in hot and tropic climates such as Dubai and New Delhi. Adsorption chillers require more thermal energy to meet the cooling load in hot and dry climates. The adsorption chillers operate in their full capacity and in higher coefficient of performance when they run in a moderate climate since they can properly reject the exhaust heat. The simulation results also indicated that PV/T solar collector have higher efficiency in warmer climates, however it requires a larger size of PV/T collectors to supply the thermally driven chillers for providing cooling in hot climates. Therefore using an electrical chiller as backup gives much better results in terms of primary energy savings, since PV/T electrical production also can be used for backup electrical chiller in a net metering mechanism.

This master thesis examines if a PV system in “norra Djurgårdsstaden” (Stockholm) can be optimized by the addition of a battery storage system. Both in terms of increasing the usage of the produced PV energy and also (partly as a consequence) becoming more efficient and environment friendly. Simulations were run in both MATLAB and PVsyst. The simulations were based on measured data - PV production and consumption - and different scenarios were examined. Though the central aspect was to maximize the amount of PV energy used, simulations for peak shaving and a combination of the two were also examined.  The major differences between simulation in MATLAB and PVsyst were firstly, the fact that the input for consumption was monthly in PVsyst and hourly measurement (given by Incoord) was used in MATLAB and secondly, that different types of battery types had to be used. The battery type used in the MATLAB simulation was a NiMH battery from a company called Nilar. This battery type has the ability to be rejuvenated and thereby extend its lifetime. This type of battery did not exist as an option in PVsyst. Due to this the result of the simulation was not exactly the same. They were however similar enough to be useful; they showed similar patterns even at points of divergence.  Although the real estate was planned and built to be very energy efficient and environmentally friendly, the integration of a battery storage system was definitely able to optimize the PV system. Of the different integration options examined the most optimal was determined to be when the battery system was fed by the surplus energy from the existing PV system; after it has met momentary consumption needs. At the largest, battery storage system (10 batteries) the primary energy number (EPpet) decreased with almost 8 kWh/m2 - i.e. from 48,2 to just above40 kWh/m2. Self - consumption and self - sufficient was also positively affected by the battery storage with the former going from 59 to 77 % and the latter from 31 to 41 %. Furthermore with around 4 batteries in the battery storage system the EPpet decreased such as the real estate entered a higher order of environmental classification.  The battery system will always be an expense, however this expense is lessened by utilizing as much as possible of the PV energy, i.e. when the momentary consumption is met by the PV system before the surplus PV energy is directed to the storage in order to maximize self - consumption.

Thesis: S.M. in Engineering and Management, Massachusetts Institute of Technology, Engineering Systems Division, System Design and Management Program, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 83-84).
Electric power systems are more than just networks of generation, transmission and distribution assets. They are socio-technical systems, involving regulation, markets and technology availability. Presently, the dynamic relation among these aspects is creating new consumer needs in many power systems around the world, which incumbent electricity utilities do not seem well suited to meet at the required pace. In this context, the integration of Distributed Energy Systems (DESs) and their related business models appears as a flexible and often more affordable option to deliver value, by fulfilling the unmet needs of both consumers and utilities. To advice Chilean electric power system's stakeholders about the adequacy of a set of DES-related business models to Chilean needs, this document presents a systematic analysis, which focuses on the interrelation between business model attributes, involved DES technologies, and stakeholder needs. Specifically, an analytic framework is developed and applied to some business models currently operative in other markets, measuring their adequacy to meet stakeholders' needs in a set of envisioned scenarios of Chile's power system. This work provides a systematic tool for decision-making processes in selecting business models, when the decision must be made with qualitative data. Moreover, the evaluation in the Chilean system of actual business models shows results that should be valuable for consumers, utilities, and regulators.
by Jorge I. Le Dantec.
S.M. in Engineering and Management

The major achievements of this work are based on two categories: (A) introduction of an advanced simulation technique in both time domain and frequency domain, and (B) realistic and reliable models for converters applicable to analysis of alternative transmission systems. The proposed modeling-methodology using a combination of model quadratization and quadratic integration (QMQI) is demonstrated as a more robust, stable, and accurate method than previous modeling methodologies for power system analyses. The quadratic-integration method is free of artificial numerical-oscillations exhibited by trapezoidal integration (which is the most popularly used method in power system analyses). Artificial numerical oscillations can be the direct reason for switching malfunction of switching systems. However, the quadratic-integration method has a natural characteristic to eliminate fictitious oscillations with great simulation accuracy. Also, model quadratization permits nonlinear equations to be solved without simplification or approximation, leading to realistic models of nonlinearities. Therefore, the QMQI method is suitable for simulations of network systems with nonlinear components and switching subsystems. Realistic and reliable converter models by the application of the QMQI method can be used for advanced designs and optimization studies for alternative transmission systems; they can also be used to perform a comprehensive evaluation of the technical performance and economics of alternative transmission systems. For example, the converters can be used for comprehensive methodology for determining the optimal topology, kV-levels, etc. of alternative transmission systems for wind farms, for given distances of wind farms from major power grid substations. In this case, a comprehensive evaluation may help make more-informed decisions for the type of transmission (HVAC, HVDC, and LFAC) for wind farms.

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.

Photovoltaic (PV) systems are popular in rural areas because they provide low cost and clean electricity for homes and irrigation systems. The primary challenge of PV systems is their intermittent nature. The typical solution is storing energy in batteries; however, they are expensive and possess a short lifespan. This research proposes a new type of pumped hydro storage (PHS) which can be implemented as an alternative to batteries. The components of the system are modelled to consider losses of the system accurately. The mathematic model developed in this project assists the management system to make more efficient decisions. The proposed storage is integrated into a farmhouse that has a PV pumping system where economic aspects of implementing the proposed storage is investigated. The integration of the proposed PHS into a microgrid needs a management system to make this system efficient and 3 cost-effective. This research proposes a multi-stage management system to schedule and control the microgrid components for optimal integration of the PHS. The designed management system is able to manage the pump, turbine, and irrigation time on real-time taking into account both present and future conditions of the microgrid. This study investigates the technical aspects of the proposed system. The PHS and the management system are tested experimentally in a setup installed at smart energy laboratory at Edith Cowan university. Data used in this project are real data collected in the laboratory in order to have a realistic analysis. Economic analysis is done in different sizes with different conditions. Results indicate that the proposed system has a short payback period and a large lifetime benefit, featuring as a cost-effective and sustainable energy storage system for use in rural areas. Video abstract: https://youtu.be/VuyEvHRY7W8

Environmental concerns about the effect of greenhouse gases have led governments to regulate industrial CO2 emissions, including through emissions caps, trading and penalties, thus creating economic incentives to reduce CO2 emissions. This research focuses on strategies to reduce CO2 emissions from energy systems in the context of the process industries. In the process industries, energy systems consume fuel to generate steam and power for site process units. Improving energy efficiency can reduce costs of energy generation and use, as well as CO2 emissions. This research develops an integrated design and optimisation methodology for energy systems, allowing effective capture and control of carbon dioxide emissions. The first focus of this study is to develop a systematic approach to evaluate combinatorial strategies for reducing CO2 emissions, based on a techno-economic analysis. A conceptual design procedure with hierarchical decision-making is introduced to combine CO2 emissions reduction strategies, accounting for interactions between site components, including the heat exchanger network and utility system. CO2 emissions reduction options considered in development of this procedure include process integration techniques for improving the energy efficiency of the site and fuel switching. The proposed approach considers trade-offs between the economy of energy retrofit and CO2 emissions penalties. Opportunity for reducing the CO2 penalty is included in the economic evaluation of the combined emissions reduction strategies. A mathematical model for simultaneous optimization of emissions reduction strategies is developed. In addition to emissions reduction strategies, options for trading CO2 allowances are considered in the model. The proposed mathematical method applies Mixed Integer Non Linear Programming (MINLP) optimization, which employs a superstructure of the strategies for CO2 reduction. The proposed mathematical model relates the selected options to their operating and capital costs and to their associated CO2 emissions, allowing the optimizer to search for the optimal combination of emissions reduction strategies. While the reduction in CO2 emissions through process integration techniques is based on the existing configuration of a site and the associated structural limitations, integration of Carbon Capture and Storage (CCS) technologies can provide greater mitigation of CO2 emissions from a site. However, important challenges of implementing CCS in the process industries are the energetic and economic impact of the CCS plant on the integrated site. In the second part of this study, these energy-economic issues are explored. The CCS technologies addressed in this thesis include post- and pre-combustion CO2 capture techniques. Simulation of each capture technique is carried out in process simulation software to characterize the energy performance of the CO2 capture plant. Sensitivity analyses are carried out for key parameters of the CO2 capture plant. The relationship between these key parameters and the energy balance of the capture plant is represented using a simple energy performance model for the CO2 capture plant. This model allows the integration of the CO2 capture plant with the site utility system to be explored. Interactions between the utility system and CO2 capture plant are considered. The site utility system, together with the CO2 capture plant, is optimized for minimum operating cost. The proposed procedures are illustrated by application to a case study of a medium-scale oil refinery. The results illustrate that to reduce CO2 emissions, heat integration, utility system optimization and fuel switching provide more cost-effective solutions than integrating CCS technologies. The mathematical model allows more cost-effective solutions to be identified than using sequential, conceptual methods, but the value of the conceptual method for developing insights is also illustrated. The results demonstrate that, depending on the potential of the site for increasing heat recovery and the type of fuel used on site, solutions that combine energy efficiency and fuel switching can provide up to 40% reduction in site CO2 emissions. Integrating a post-combustion CO2 capture plant with the site utility system can provide up to 90 mol% pure CO2 for sequestration; however, the high capital cost of the capture plant reduces the economic performance of the integrated site. The high heat demand of post-combustion CO2 capture for solvent regeneration increases the fuel consumption of the site and its utility system, which in turn reduces the recovery of CO2. The results reveal that pre-combustion CO2 capture can provide opportunities for heat and power generation to improve the techno-economic performance of the overall integrated site.

The integration of wind energy into the utility network has increased significantly over the past years largely as a result of the increasing environmental concerns arising from the use of fossil fuels, coupled with the anticipated global increase in oil. In South Africa, the wind energy industry is still in its infancy, with the Klipheuwel (about 3.2 MW) and Darling (about 4.2 MW) wind farms being the only grid connected projects in the country. However, grid integration studies carried out in [1] have shown that there are over 7 000 MW potential ideas for wind power in the Western Cape alone and this is a clear indication that there is a growing interest in wind development locally. The Government has also set a 4% target for the development of the renewable energy in the country by 2013. In light of the above, this thesis discusses some of the technical requirements and power quality issues that need to be addressed in order to fully integrate wind power into the network without adversely affecting the operation of the grid. These have been researched through reviewing the various standards and grid codes for wind power that have been implemented in other leading countries, in order to identify some of the requirements that can be adapted to suit our local integration process. Some of the main technical issues that are discussed in this thesis include the strength of the grid (fault levels), permitted penetration levels, choice of wind turbine and the reactive power requirements of the network. All these issues contribute towards the resolution of the impact of wind turbines on the power quality of the network, especially at the point of common coupling or connection (PCC). Various power quality phenomena were discussed in the literature but the ones that were further investigated included the voltage level profile, harmonic distortions as well as reactive power requirements from the wind turbines. These were determined both during the steady operation of the network and during a network disturbance.

Renewable energy (i.e., biomass, wind and solar) and Battery Energy Storage (BES) are emerging as sustainable solutions for electricity generation. In the last decade, the smart grid has been introduced to accommodate high penetration of such renewable resources and make the power grid more efficient, reliable and resilient. The smart grid is formulated as a combination of power systems, telecommunication communication and information technology. As an integral part of the smart grid, a smart integration approach is presented in this thesis. The main idea behind the smart integration is locating, sizing and operating renewable-based Distributed Generation (DG) resources and associated BES units in distribution networks strategically by considering various technical, economical and environmental issues. Hence, the aim of the thesis is to develop methodologies for strategic planning and operations of high renewable DG penetration along with an efficient usage of BES units. The first contribution of the thesis is to present three alternative analytical expressions to identify the location, size and power factor of a single DG unit with a goal of minimising power losses. These expressions are easily adapted to accommodate different types of renewable DG units for minimizing energy losses by considering the time-varying demand and different operating conditions of DG units. Both dispatchable and non-dispatchable renewable DG units are investigated in the study. Secondly, a methodology is also introduced in the thesis for the integration of multiple dispatchable biomass and nondispatchable wind units. The concept behind this methodology is that each nondispatchable wind unit is converted into a dispatchable source by adding a biomass unit with sufficient capacity to retain the energy loss at a minimum level. Thirdly, the thesis studies the determination of nondispatchable photovoltaic (PV) penetration into distribution systems while considering time-varying voltage-dependent load models and probabilistic generation. The system loads are classified as an industrial, commercial or residential type or a mix of them with different normalised daily patterns. The Beta probability density function model is used to describe the probabilistic nature of solar irradiance. An analytical expression is proposed to size a PV unit. This expression is based on the derivation of a multiobjective index (IMO) that is formulated as a combination of three indices, namely active power loss, reactive power loss and voltage deviation. The IMO is minimised in determining the optimal size and power factor of a PV unit. Fourthly, the thesis discusses the integration of PV and BES units considering optimal power dispatch. In this work, each nondispatchable PV unit is converted into a dispatchable source by adding a BES unit with sufficient capacity. An analytical expression is proposed to determine the optimal size and power factor of PV and BES units for reducing energy losses and enhancing voltage stability. A self-correction algorithm is then developed for sizing multiple PV and BES units. Finally, the thesis presents a comprehensive framework for DG planning. In this framework, analytical expressions are proposed to efficiently capture the optimal power factor of each DG unit with a standard size for minimising energy losses and enhancing voltage stability. The decision for the optimal location, size and number of DG units is obtained through a benefit-cost analysis over a given planning horizon. Here, the total benefit includes energy sales, loss reduction, network investment deferral and emission reduction, while the total cost is a sum of capital, operation and maintenance expenses. The study reveals that the time-varying demand and generation models play a significant role in renewable DG planning. Depending on the characteristics of demand and generation, a distribution system would accommodate up to an estimated 48% of the nondispatchable renewable DG penetration. A higher penetration level could be obtained for dispatchable DG technologies such as biomass and a hybrid of PV and BES units. More importantly, the study also indicates that optimal power factor operation could be one of the aspects to be considered in the strategy of smart renewable DG integration. A significant energy loss reduction and voltage stability enhancement can be achieved for all the proposed scenarios with DG operation at optimal power factor when compared to DG generation at unity power factor which follows the current standard IEEE 1547. Consequently, the thesis recommends an appropriate modification to the grid code to reflect the optimal or near optimal power factor operation of DG as well as BES units. In addition, it is shown that inclusion of energy loss reduction together with other benefits such as network investment deferral and emission reduction in the analysis would recover DG investments faster.

Wind and solar energy are clean, free of fuel cost and likely to have great potential in the future. However, besides the technical difficulties associated with integrating variable sources of generation with the electric grid, high capital cost and other indirect costs to power system operations, such as ancillary service requirements, delay more widespread investment in wind and solar power plants. Current energy policies, especially renewable incentives and CO2 emission regulations, remain controversial and uncertain. Pumped-hydroelectric energy storage has proven to be valuable as bulk energy storage for energy arbitrage coordinating with conventional thermal generators. In the future grid, there are uncertainties, in terms of modeling and optimization, of assessing the value of bulk energy storage coordinating less with thermal generators and more with wind and solar. Moreover, the price of natural gas is predicted to have large variations in the next several decades. It is therefore necessary to construct a generation planning model with comprehensive modeling of wind, solar and energy storage under multiple scenarios of energy policies and natural gas prices. This dissertation presents such an optimal planning model using a multi-period optimization formulation and its implementation in the MATPOWER's extensible optimal power flow structure. A 3-bus test system is constructed to test the sensitivity of the planning model. This model is further applied to the reduced 240-bus Western Electric Coordinating Council (WECC) system to study more practical planning results.
Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science

Numerous countries are trying to reach almost 100\% renewable penetration. Variable renewable energy (VRE), for instance wind and PV, will be the main provider of the future grid. The efforts to decrease the greenhouse gasses are promising on the current remarkable growth of grid connected photovoltaic (PV) capacity. This thesis provides an overview of the presented techniques, standards and grid interface of the PV systems in distribution and transmission level. This thesis reviews the most-adopted grid codes which required by system operators on large-scale grid connected Photovoltaic systems. The adopted topologies of the converters, the control methodologies for active - reactive power, maximum power point tracking (MPPT), as well as their arrangement in solar farms are studied. The unique L(LCL)2 filter is designed, developed and introduced in this thesis. This study will help researchers and industry users to establish their research based on connection requirements and compare between different existing technologies. Another, major aspect of the work is the development of Virtual Inertia Emulator (VIE) in the combination of hybrid energy storage system addressing major challenges with VRE implementations. Operation of a photovoltaic (PV) generating system under intermittent solar radiation is a challenging task. Furthermore, with high-penetration levels of photovoltaic energy sources being integrated into the current electric power grid, the performance of the conventional synchronous generators is being changed and grid inertial response is deteriorating. From an engineering standpoint, additional technical measures by the grid operators will be done to confirm the increasingly strict supply criteria in the new inverter dominated grid conditions. This dissertation proposes a combined virtual inertia emulator (VIE) and a hybrid battery-supercapacitor-based energy storage system . VIE provides a method which is based on power devices (like inverters), which makes a compatible weak grid for integration of renewable generators of electricity. This method makes the power inverters behave more similar to synchronous machines. Consequently, the synchronous machine properties, which have described the attributes of the grid up to now, will remain active, although after integration of renewable energies. Examples of some of these properties are grid and generator interactions in the function of a remote power dispatch, transients reactions, and the electrical outcomes of a rotating bulk mass. The hybrid energy storage system (HESS) is implemented to smooth the short-term power fluctuations and main reserve that allows renewable electricity generators such as PV to be considered very closely like regular rotating power generators. The objective of utilizing the HESS is to add/subtract power to/from the PV output in order to smooth out the high frequency fluctuations of the PV power, which may occur due to shadows of passing cloud on the PV panels. A control system designed and challenged by providing a solution to reduce short-term PV output variability, stabilizing the DC link voltage and avoiding short term shocks to the battery in terms of capacity and ramp rate capability. Not only could the suggested system overcome the slow response of battery system (including dynamics of battery, controller, and converter operation) by redirecting the power surges to the supercapacitor system, but also enhance the inertial response by emulating the kinetic inertia of synchronous generator.

The first part is concerned with dynamic aggregated modelling of large offshore wind farms and their integration into power systems via VSC-HVDC links. The dynamic aggregated modelling of offshore wind farms including WT-DFIGs and WT-PMSGs are proposed to achieve effective representations of wind farms in terms of computational time and simulation accuracy for transient stability analysis. Modelling and control of VSC-HVDC systems for integration of offshore wind farms are investigated. Comparisons of two control schemes of rectifier-side converter are carried out to evaluate their dynamic performance for integration of these offshore wind farms in terms of transient stability. The second part is to address the advanced transmission systems with innovative HVDC configurations. Feasibility studies of updated schemes of monoplolar CSC-HVDC link with support of monopolar VSC-HVDC link as the hybrid bipolar CSC/I{VDC system is carried out to deal with two key issues of CSC-HVDC. Small-signal modelling of MTDC grids is investigated and parameter optimisation of PI controller of converters in MTDC grids is carried out using PSO method based on small-signal models of the system at multiple operating points to obtain optimised parameters of PI controllers to improve dynamic performance of MTDC grids at multiple operating points.

Electric energy constitutes one of the most crucial elements to almost every aspect of life of people. The modern electric power systems face several challenges such as efficiency, economics, sustainability, and reliability. Increase in electrical energy demand, distributed generations, integration of uncertain renewable energy resources, and demand side management are among the main underlying reasons of such growing complexity. Additionally, the elements of power systems are often vulnerable to failures because of many reasons, such as system limits, weak conditions, unexpected events, hidden failures, human errors, terrorist attacks, and natural disasters. One common factor complicating the operation of electrical power systems is the underlying uncertainties from the demands, supplies and failures of system components. Stochastic programming provides a mathematical framework for decision making under uncertainty. It enables a decision maker to incorporate some knowledge of the intrinsic uncertainty into the decision making process. In this dissertation, we focus on application of two-stage and multistage stochastic programming approaches to electric energy systems modeling and optimization. Particularly, we develop models and algorithms addressing the sustainability and reliability issues in power systems. First, we consider how to improve the reliability of power systems under severe failures or contingencies prone to cascading blackouts by so called islanding operations. We present a two-stage stochastic mixed-integer model to find optimal islanding operations as a powerful preventive action against cascading failures in case of extreme contingencies. Further, we study the properties of this problem and propose efficient solution methods to solve this problem for large-scale power systems. We present the numerical results showing the effectiveness of the model and investigate the performance of the solution methods. Next, we address the sustainability issue considering the integration of renewable energy resources into production planning of energy-intensive manufacturing industries. Recently, a growing number of manufacturing companies are considering renewable energies to meet their energy requirements to move towards green manufacturing as well as decreasing their energy costs. However, the intermittent nature of renewable energies imposes several difficulties in long term planning of how to efficiently exploit renewables. In this study, we propose a scheme for manufacturing companies to use onsite and grid renewable energies provided by their own investments and energy utilities as well as conventional grid energy to satisfy their energy requirements. We propose a multistage stochastic programming model and study an efficient solution method to solve this problem. We examine the proposed framework on a test case simulated based on a real-world semiconductor company. Moreover, we evaluate long-term profitability of such scheme via so called value of multistage stochastic programming.

Electric power is one of the most critical parts of everyday life; from lighting, heating, and cooling homes to powering televisions and computers. The modern power grids face several challenges such as efficiency, sustainability, and reliability. Increase in electrical energy demand, distributed generations, integration of uncertain renewable energy resources, and demand side management are among the main underlying reasons of such growing complexity. Additionally, the elements of power systems are often vulnerable to failures because of many reasons, such as system limits, poor maintenance, human errors, terrorist/cyber attacks, and natural phenomena. One common factor complicating the operation of electrical power systems is the underlying uncertainties from the demands, supplies and failures of system components. Stochastic optimization approaches provide mathematical frameworks for decision making under uncertainty. It enables a decision maker to incorporate some knowledge of the uncertainty into the decision making process to find an optimal trade off between cost and risk. In this dissertation, we focus on application of three risk-averse approaches to power systems modeling and optimization. Particularly, we develop models and algorithms addressing the cost-effectiveness and reliability issues in power grids with integrations of renewable energy resources. First, we consider a unit commitment problem for centralized hydrothermal systems where we study improving reliability of such systems under water inflow uncertainty. We present a two-stage robust mixed-integer model to find optimal unit commitment and economic dispatch decisions against extreme weather conditions such as drought years. Further, we employ time series analysis (specifically vector autoregressive models) to construct physical based uncertainty sets for water inflow into the reservoirs. Since extensive formulation is impractical to solve for moderate size networks we develop an efficient Benders' decomposition algorithm to solve this problem. We present the numerical results on real-life case study showing the effectiveness of the model and the proposed solution method. Next, we address the cost effectiveness and reliability issues considering the integration of solar energy in distributed (decentralized) generation (DG) such as microgrids. In particular, we consider optimal placement and sizing of DG units as well as long term generation planning to efficiently balance electric power demand and supply. However, the intermittent nature of renewable energy resources such as solar irradiance imposes several difficulties in decision making process. We propose two-stage stochastic programming model with chance constraints to control the risk of load shedding (i.e., power shortage) in distributed generation. We take advantage of another time series modeling approach known as autoregressive integrated moving average (ARIMA) model to characterize the uncertain solar irradiance more accurately. Additionally, we develop a combined sample average approximation (SAA) and linearization techniques to solve the problem more efficiently. We examine the proposed framework with numerical tests on a radial network in Arizona. Lastly, we address the robustness of strategic networks including power grids and airports in general. One of the key robustness requirements is the connectivity between each pair of nodes through a sufficiently short path, which makes a network cluster more robust with respect to potential disruptions such as man-made or natural disasters. If one can reinforce the network components against future threats, the goal is to determine optimal reinforcements that would yield a cluster with minimum risk of disruptions. We propose a risk-averse model where clusters represents a R-robust 2-club, which by definition is a subgraph with at least R node/edge disjoint paths connecting each pair of nodes, where each path consists of at most 2 edges. And, develop a combinatorial branch-and-bound algorithm to compare with an equivalent mathematical programming approach on random and real-world networks.

Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2018.
A smart grid is an intelligent power delivery system integrating traditional and advanced control, monitoring, and protection systems for enhanced reliability, improved efficiency, and quality of supply. To achieve a smart grid, technical challenges such as voltage instability; power loss; and unscheduled power interruptions should be mitigated. Therefore, future smart grids will require intelligent solutions at transmission and distribution levels, and optimal placement & sizing of grid components for optimal steady state and dynamic operation of the power systems. At distribution levels, feeder reconfiguration and Distributed Generation (DG) can be used to improve the distribution network performance. Feeder reconfiguration consists of readjusting the topology of the primary distribution network by remote control of the tie and sectionalizing switches under normal and abnormal conditions. Its main applications include service restoration after a power outage, load balancing by relieving overloads from some feeders to adjacent feeders, and power loss minimisation for better efficiency. On the other hand, the DG placement problem entails finding the optimal location and size of the DG for integration in a distribution network to boost the network performance. This research aims to develop Particle Swarm Optimization (PSO) algorithms to solve the distribution network feeder reconfiguration and DG placement & sizing problems. Initially, the feeder reconfiguration problem is treated as a single-objective optimisation problem (real power loss minimisation) and then converted into a multi-objective optimisation problem (real power loss minimisation and load balancing). Similarly, the DG placement problem is treated as a single-objective problem (real power loss minimisation) and then converted into a multi-objective optimisation problem (real power loss minimisation, voltage deviation minimisation, Voltage stability Index maximisation). The developed PSO algorithms are implemented and tested for the 16-bus, the 33-bus, and the 69-bus IEEE distribution systems. Additionally, a parallel computing method is developed to study the operation of a distribution network with a feeder reconfiguration scheme under dynamic loading conditions.

As electric vehicles (EVs) become more popular, the utility companies are forced to increase power generations in the grid. However, these EVs are capable of providing power to the grid to deliver different grid ancillary services in a concept known as vehicle-to-grid (V2G) and grid-to-vehicle (G2V), in which the EV can serve as a load or source at the same time. These services can provide more benefits when they are integrated with Photovoltaic (PV) generation. The proper modeling, design and control for the power conversion systems that provide the optimum integration among the EVs, PV generations and grid are investigated in this thesis. The coupling between the PV generation and integration bus is accomplished through a unidirectional converter. Precise dynamic and small-signal models for the grid-connected PV power system are developed and utilized to predict the system’s performance during the different operating conditions. An advanced intelligent maximum power point tracker based on fuzzy logic control is developed and designed using a mix between the analytical model and genetic algorithm optimization. The EV is connected to the integration bus through a bidirectional inductive wireless power transfer system (BIWPTS), which allows the EV to be charged and discharged wirelessly during the long-term parking, transient stops and movement. Accurate analytical and physics-based models for the BIWPTS are developed and utilized to forecast its performance, and novel practical limitations for the active and reactive power-flow during G2V and V2G operations are stated. A comparative and assessment analysis for the different compensation topologies in the symmetrical BIWPTS was performed based on analytical, simulation and experimental data. Also, a magnetic design optimization for the double-D power pad based on finite-element analysis is achieved. The nonlinearities in the BIWPTS due to the magnetic material and the high-frequency components are investigated rely on a physics-based co-simulation platform. Also, a novel two-layer predictive power-flow controller that manages the bidirectional power-flow between the EV and grid is developed, implemented and tested. In addition, the feasibility of deploying the quasi-dynamic wireless power transfer technology on the road to charge the EV during the transient stops at the traffic signals is proven.

Several CO2 transcritical booster systems in supermarkets use the potential of integrating geothermal storage, enabling subcooling during warm climate conditions as well as being a heat source during cold climate conditions. First of all, field measurements of one of these systems located in Sweden were analysed with particular focus on the heat-recovery performance. The best theoretical operational strategy was compared to the one really implemented and the differences in the annual energy usage were assessed through modelling. The results show that an alternative to the best theoretical operational strategy exists; heat can be extracted from the ground while low-temperature heat is rejected by the gas cooler. Such an alternative strategy has important technical advantages with a negligible increment of the energy usage. In the second part of this work, the benefits of geothermal subcooling were evaluated. Applying the BIN hours method, it was demonstrated that this system is expected to save on average roughly 5% of the total power consumption, in Stockholm’s climate. The models utilized for the winter and summer season were combined to find the relationship between geothermal storage size and annual energy savings. In this way, it was possible to calculate the present value of the operational savings for the study case. Furthermore, a general methodology for assessing the economic feasibility of this system solution is presented. Finally, several scenarios were investigated to produce parametric curves and to perform a sensitivity analysis. Comparing the results with the typical Swedish prices for boreholes, the cases where this system solution is economically justified were identified. These are supermarkets with a Heat Recovery Ratio (HRR) higher than the average. For examples, supermarkets supplying heat to the neighbouring buildings (considering the Stockholm’s climate, systems with an annual average HRR of at least 70%). Relying only on savings from subcooling was found to be not enough to justify a geothermal storage, a not-negligible amount of heat must be extracted in winter. Finally, some interesting concepts and alternatives to a geothermal integration are presented to point out relevant future work.

Neste trabalho é analisado, por via numérica e experimental, o comportamento térmico e eléctrico de um sistema fotovoltaico/térmico integrado em edifício, recorrendo a material de mudança de fase para regularização da diferença de temperatura entre interior e exterior e para a estabilização da temperatura do módulo fotovoltaico. Foi realizado uma revisão da literatura sobre o tema. Um modelo de cálculo dos fenómenos de transferência de calor e massa foi desenvolvido, assim como da produção de energia eléctrica, e implementado em software de cálculo Matlab/Simulink®. Paralelamente foram conduzidos ensaios experimentais a fim de analisar o comportamento térmico do sistema e respectiva validação do modelo numérico. De modo a melhorar a eficiência total do sistema, foi aplicado um processo de optimização com o método dos algoritmos genéticos. Do estudo, conclui-se que o sistema pode alcançar uma eficiência máxima total de 64% na configuração de inverno e de 32% na configuração de verão; ABSTRACT: This work presents a numerical and experimental analysis of the thermal and electrical performance of a building integrated photovoltaic/thermal system (BIPV/T), with the use of phase change material for stabilize the temperature difference between indoors and outdoors and a rapid stabilization of the PV modules’ temperature. A literature review was conducted on the topic. A calculation model was developed of the heat and mass transfer phenomena, as well as a model of a photovoltaic module, which were implemented in Matlab/Simulink®. Experimental tests were performed to analyze the thermal performance of the system and the validation of the numerical model. To improve overall system efficiency, an optimization process with the method of genetic algorithms was applied. From the study, it is concluded that the system can achieve a maximum total efficiency of 64% with winter configuration and 32% with summer configuration.

The following thesis deals with the energy production comparison between two different conversion technologies for photovoltaic systems: central-inverter conversion versus micro-inverter conversion. After an analysis over the many energy production systems, the thesis focuses on photovoltaic energy systems. The study of cell, module and system efficiencies will explain all causes of energy losses that can affect the photovoltaic energy generation. The second part of the thesis is focused on the micro-inverter technology and the differences with the central-inverter systems. Data analyses have been made on many systems in different locations (with almost the same sun radiation received), different azimuth and tilt angles, and different shading percentage. The analyses will show how micro-inverter systems can improve energy production not only during shaded but also in not-shaded conditions. At the end an economic comparison between the two different technologies will try to justify the use of micro-inverter systems not only for energy production efficiency but even for economic affordability.

This thesis centres on issues of economic efficiency originating from the large-scale development of intermittent renewable energy sources (RES) in Europe. The flexible resources that are necessary to cope with their specificities (variability, low-predictability, site specificity) are already known, but adequate signals are required to foster efficient operation and investment in these resources. A first question is to what extent intermittent RES can remain out of the market at times when they are the main driver of investment and operation in power systems. A second question is whether the current market design is adapted to their specificities. These two questions are tackled in four distinct contributions.The first chapter is a critical literature review. This analysis introduces and confronts two (often implicit) paradigms for RES integration. It then identifies and discusses a set of evolutions required to develop a market design adapted to the large-scale development of RES, such as new definitions of the products exchanged and reorganisation of the sequence of electricity markets.In the second chapter, an analytical model is used to assess the potential of intraday markets as a flexibility provider to intermittent RES with low production predictability. This study highlights and demonstrates how the potential of intraday markets is heavily dependent on the evolution of the forecast errors.The third chapter focuses on the benefits of curtailing the production by intermittent RES, as a tool to smooth out their variability and reduce overall generation costs. Another analytical model is employed to anatomize the relationship between these benefits and a set of pivotal parameters. Special attention is also paid to the allocation of these benefits between the different stakeholders.In the fourth chapter, a numerical simulation is used to evaluate the ability of the European transmission system operators to tackle the investment wave required in order to manage the production of intermittent RES. Alternative financing strategies are then assessed. The findings reveal that under the current trend of tariffs, the volumes of investment forecasted will be highly challenging for transmission system operators.

The massive global use of fossil fuels has resulted in a lack of oil that opens up for an increased demand for renewable resources. Decreasing the dependence on fossil fuels is a global goal where a fossil free energy market is a vital part in the solution. Cuba is a country whose electricity production is very dependent of oil, although there is a national goal to achieve a 24 percent renewable electricity until year 2030. The incentives behind this decision are that the production cost for electricity is high in Cuba and the emissions of carbon dioxide and other particles are causing local and global environmental problems. Placetas is a municipality in Cuba that have the largest pork production in the country and furthermore many aluminum industries. These industries have been shown to emit particles that significantly reduces the air quality in the municipality and hence also the inhabitant’s quality of life.    Biogas is a mixture of gases and mainly consists of methane and carbon dioxide. It is manufactured by anaerobic digestion of biomass, which refers to for example pig manure. For a municipality like Placetas with severe air pollutions, biogas possesses a potential to replace a part of the current fuel that is used in the industries and reduce the emissions of air pollutions. Hence, this study aims to investigate, by literature and field study, the potential to replace the fuel oil in the aluminum industries in Placetas with biogas from pig manure. Furthermore, it will investigate whether the biogas can be used in the households to reduce the consumption of electricity, which is generated from fossil fuels. The potential of generating electricity directly from biogas is also assessed. These scenarios with different utilizations of biogas are based on a central assumption where if all municipalities in Cuba achieve an electricity generation from renewable resources of 24 percent of the consumption, the whole country does. Hence, the study investigates if it is possible to achieve this in Placetas. To do this and still meet the electricity demand, the potential of solar photovoltaic (PV) to complement the biogas will be investigated. Moreover, an environmental assessment and economic evaluation of the costs and savings due to the transition to renewable will be done. Also, the required area for the solar PV and the volume of the digester will be calculated.    These investigations and calculations result in two different scenarios in which the biogas in both is assumed to be primarily distributed to the aluminum industries. The remaining biogas will in the first scenario be generated as electricity and together with solar power aim to cover 24 percent of the consumption in Placetas. In the second scenario the biogases potential to replace the consumed electricity in the households is investigated. To reach the goal of 24 percent, 24 percent of the electricity will be generated from solar power. The conclusions show an annual electricity consumption in Placetas of 2,526.2 MWh. From the crude oil used in this electricity generation, 260 tons of CO2emissions can be derived. The energy consumption in the industries using fuel oil is 21,271 GJ and the emissions of particles due to this was in some locations 270 percent higher than allowed. The generated biogas from pig manure corresponds to 24,430 GJ energy or2,375,000 kWh electricity. Lastly, scenario 1 is found to be most feasible in terms of environmental and social aspects.
Konsekvenserna av det fossildrivna globala samhället har resulterat i en oljebrist som lämnat utrymme för utveckling av förnybara energilösningar. Att därmed minska användningen av fossila bränslen har kommit att bli ett globalt mål där en övergång till en fossilfri energimarknad är en vital del av bedriften. Kuba är i dagsläget väldigt beroende av olja för sin elproduktion, men har som syfte att 24 procent av landets energimix till år 2030 ska innefatta förnybara källor. Incitamenten som kan ha drivit fram ett sådant beslut är dels grundat i att produktionskostnaden för elektricitet är väldigt hög på Kuba men även att utsläppen av koldioxid och diverse miljöfarliga partiklar bidragit till globala och lokala miljöproblem. Placetas är en kommun på Kuba som inte bara besitter landets största grisproduktion utan även många aluminiumindustrier. Dessa industrier har visat sig släppa ut farliga partiklar som avsevärt försämrar luftkvalitén i området och därmed även människans livskvalitet.    Biogas som är en blandning av gaser och till största del innehåller metan och koldioxid, går att genereras från grisgödsel. För en kommun som Placetas med miljöproblem i form av luftföroreningar som resultat av användningen av fossila bränslen i aluminiumindustrin, kan biogasen från grisgödsel ersätta en del av bränslet och minska utsläppen av luftföroreningar. Därmed undersöker den här studien, genom litteraturstudie, fältstudie och scenarioanalys, potentialen hos biogasen från grisgödsel att ersätta bränslet i aluminiumindustrierna i Placetas. Dessutom undersöks det i två scenarion huruvida biogasen kan användas för att generera elektricitet eller för att minska användningen av denna i hushållen. Dessa scenarier utgår från ett centralt antagande att om alla kommuner på Kuba uppnår en andel av 24 procent förnybart av kommunens elkonsumtion, gör hela landet det. Därav kommer studien undersöka huruvida det går att uppfylla det målet i Placetas. För att uppfylla behovet undersöks då även potentialen hos solceller att komplettera den andel som biogasen inte kan täcka. Vidare utförs miljöevaluering och ekonomisk analys av kostnader och besparingar för övergången till förnybar energi. Även arean som solcellerna behöver och volymen av biogasanläggningen för att möta energibehovet i kommunen beräknas.    Dessa beräkningar och undersökningar resulterar i två olika scenarier inom vilket biogasen i samtliga scenarion ska antas i första hand gå till aluminiumindustrin. Den biogasen som därefter är tillgänglig kommer i det första scenariot omvandlas till elektricitet som tillsammans med solkraften ska nå det nationella målet om 24 procent förnybar energi i den genererade elektriciteten. Det andra scenariot undersöker huruvida biogasen kan användas för att ersätta den konsumerade hushållselen i Placetas. Solkraft antas enskilt stå för det förnybara i att uppnå målet om 24 procent. Slutsatser av studien blir att den årliga elkonsumtionen i Placetas är 2,526.2 MWh. Förbränning av råolja i genereringen av denna elektricitet resulterar i koldioxidutsläpp om 260 ton. Energikonsumtionen inom aluminiumindustrierna är 21,271 GJ, där förbränning av bränslet bidrar till koldioxidutsläpp och försämrad luftkvalité på grund av partikelutsläpp. Mängden av dessa partiklar var på vissa platser 270 procent högre än tillåtet. Biogasen som kan genereras från grisgödsel motsvarar 24,430 GJ energi eller 2,375,000 kWh elektricitet. Slutligen visas första scenariot mest lämpligt baserat på miljö- och sociala aspekter.

During the 21st century there has been a tremendous increase in grid-connected photovoltaic (PV) capacity globally, due to falling prices and introduction of economic incentives. PV systems are in most cases small-scale, installed on residential dwellings, which means that the power production is widely distributed and close to the end-user of electricity. In this licentiate thesis the distributed PV in the built environment is studied. A methodology for assessing short-term (sub-minute) solar variability was developed, which in the continuation of this PhD project could be used to study the aggregated impact on the local distribution grid from dispersed PV systems. In order to identify potential locations for PV systems in a future scenario, methodology was developed to assess the rooftop topography on both local level using LiDAR data and nationally through building statistics. Impacts on the distribution grid were investigated through a case study on a rural municipality in Sweden. It was found that the hosting capacity, i.e. the amount of PV power generation that can be integrated in the grid without exceeding certain power quality measures, is high, at least 30%. However, the hosting capacity on transmission level needs further investigation. As a first step a methodology was developed in order to model scenarios for hourly solar power generation, aggregated over wide areas, here applied to the whole Swedish power system. The model showed high correlation compared to PV power production reported to the Swedish transmission system operator (TSO). Furthermore, it was used to model scenarios of high PV penetration in Sweden, which give some indications on the impact on the power system, in terms of higher frequency of extreme ramps.

Passive ventilation and cooling systems can offer energy savings when combined into a mechanical ventilation and cooling strategy for office buildings. At early design stages, it is difficult to predict actual energy savings as current design and calculation tools are limited and do not allow assessment for energy reductions when attempting to use typical passive options such as solar chimneys, rain screen facades, ventilated double facades, passive downdraught evaporative cooling and earth ducts. The only passive systems that are directly incumbent to dynamic thermal modelling software are natural ventilation and external solar shading. Currently, impacts of passive systems on annual building energy performance is unclear and lacks clarity. In hot climates, this is even more problematic as buildings need to endure higher external temperatures and solar irradiation. Understanding minimal energy performance reductions for each passive system can aid with design decisions regarding building ventilation and cooling strategies. The aim of this study is to investigate how existing passive ventilation and cooling system design and operational strategies can be improved to reduce mechanical ventilation and cooling energy consumption for commercial buildings in hot climates. Theoretical commercial building models are created using dynamic thermal simulation software to determine minimum mechanical ventilation and cooling energy values, which are verified against published bench marks, known as base case models. These base case models are simulated using weather data from four different hot climates (Egypt, Portugal, Kenya and Abu Dhabi). Impacts of passive system energy performance are afforded by using either dynamic thermal simulation or fundamental steady state analysis identifying approximate passive ventilation and cooling potentials for reducing mechanical energy. These percentage reductions are created based upon passive system parameters and weather data, using appropriate methodology. From these findings new simplified design guidelines, integration strategies and performance design tools are created including a new passive system energy assessment tool (PSEAT) using Microsoft Excel platform to ensure that a wider audience can be achieved in industry. The design guidance and integration strategies are developed and simplified to enable architects, building services engineers and alike, to apply with speed and accuracy influencing the design process and improve confidence in desired passive solution.

The needs to the sustainable development of electricity, energy efficiency improvement, and environment pollution reduction have favored the development of distributed generation (DG). But the problems come with increasing DG penetration in distribution networks. This thesis presents the Solar Energy Grid Integration System (SEGIS) Stage III project done by Portland General Electric (PGE), Advanced Energy, Sandia National Lab on a PGE selected distribution feeder. The feeder has six monitored commercial solar PV systems connected. The total power output from the PV systems has the potential to reach 30% of the feeder load. The author analyzes the performance of the solar feeder on both generation and voltage effects. As a project report, it introduced a new islanding detection done by other team members to give an islanding solution of future high penetration distribution networks. At last, the author describes micro-grid and grid support concepts in a SEGIS concept paper with some examples.

Memory design is a crucial component of VLSI system design from area, power and performance perspectives. To meet the increasingly challenging system specifications, architecture, circuit and device level innovations are required for existing memory technologies. Emerging memory solutions are widely explored to cater to strict budgets. This thesis presents design methodologies for custom memory design with the objective of power-performance benefits across specific applications. Taking example of STTRAM (spin transfer torque random access memory) as an emerging memory candidate, the design space is explored to find optimal energy design solution. A thorough thermal reliability study is performed to estimate detection reliability challenges and circuit solutions are proposed to ensure reliable operation. Adoption of the application-specific optimal energy solution is shown to yield considerable energy benefits in a read-heavy application called MBC (memory based computing). Circuit level customizations are studied for the volatile SRAM (static random access memory) memory, which will provide improved energy-delay product (EDP) for the same MBC application. Memory design has to be aware of upcoming challenges from not only the application nature but also from the packaging front. Taking 3D die-folding as an example, SRAM performance shift under die-folding is illustrated. Overall the thesis demonstrates how knowledge of the system and packaging can help in achieving power efficient and high performance memory design.

In the recent past, energy and environment have played opposite roles in human progress. Energy has been as an engine for the development and the environment has been as the breaker of it. Only after a more conscious and rigorous international policy on environment protection, not opposed to the development, energy and environmental matters have become unified behind a new sustainable model. This has determined new strategies in the energy sector. Hence, renewable sources have become a must in this new sustainable model. The key role in the last decade has been played by the Distributed Power Generation Systems (DPGS) which present an efficient and economic way of generating electricity closer to the load(s). The DPGS can contribute to an efficient and renewable electricity future by potentially: increasing the use of renewable sources of energy; improving the efficiency of the electricity system by reducing transmission and distribution losses; improving the security of the electricity supply through increased diversity of supply and reduced vulnerability to simultaneous system failures. However, the new trend of using DPGS comes also with a suite of new challenges. One of the challenges is the interaction between the DPGS and the utility grid. As a consequence, grid interconnection requirements applied to the distributed generation are continuously updated in order to maintain the quality and the stability of the utility grid. Consequently, the major tasks of this thesis were to analyze and to develop new strategies for solar energy conversion addressing efficiency and quality in order to allow the DPGS not only to deliver power with high efficiency to the utility grid but also to sustain it. This thesis was divided into three main parts, as follows: à ¢ Small Photovoltaic System: AC moduleà ¢ , à ¢ Control of DPGSà ¢ and à ¢ New Topologies and Devices, technologies for multilevel inverter addressing grid connectionà ¢ . 8 In the first part, the main focus was on topologies for module integration. Additionally, a new topology has been proposed and developed and successfully tested. In the second part, the main focus was c on Control, PWM techniques and ancillary function as grid-connection algorithms. In the third part, the main reported research was concentrated around the role of multilevel inverter in the next future of DPGS. Focusing on topologies and technologies device.