Efficient Energy Optimization for Smart Grid and Smart Community

The electric power industry has undergone significant changes in response to the environmental concerns during the past decades. Nowadays, due to the integration of different distributed energy systems in the smart grid, the balancing between power generation and load demand becomes a critical problem. Specifically, due to the intermittent nature of renewable energy sources (RESs) , power system optimization becomes significantly complicated. Due to the uncertain nature of RESs, the system may fail to ensure the power quality which may cause increased operating costs for committing costly reserve units or penalty costs for curtailing load demands. This dissertation presents three projects to study the optimization and control for smart grid and smart community. First, optimal operation of battery energy storage system (BESS) in grid-connected microgrid is studied. Near optimal operation/allocation of the BESS is investigated with the consideration of battery lifetime characteristics. Approximate dynamic programming (ADP) is proposed to solve optimal control policy for time-dependent and finite-horizon BESS problems and performance comparison is done with classical dynamic programming approach. The results show that the ADP can optimize the system operation under different scenarios to maximize the total system revenue. Second, optimal operation of the BESS in islanded microgrid is also studied. Specifically, a new islanded microgrid model is formulated based on Markov decision process. A computationally efficient ADP approach is proposed to solve this energy optimization problem, and achieve near minimum operational cost efficiently. Simulation results show that the proposed ADP can achieve 100% and at least 98% of optimality for deterministic and stochastic case studies, respectively. The performance of the proposed ADP approach also achieved 18:69 times faster response than that of the traditional DP approach for 0:5 million of data samples. Third, a demand side management technique is proposed for the optimization of residential demands with financial incentives. A new design of comfort indicator is proposed considering both thermal and other electric appliances based on consumers’ comfort level. The proposed approach is compared with two existing demand response approaches for both 10-houses and 100-houses simulation studies. For both cases, the proposed approach outperformed the existing approaches in terms of reward incentives and comfort levels

Microgrid design, control, and performance evaluation for sustainable energy management in manufacturing

This research studies the capacity sizing, control strategies, and performance evaluation of the microgrids with hybrid renewable sources for manufacturing end use customers towards a distributed sustainable energy system paradigm. Microgrid technology has been widely investigated and applied in commercial and residential sector, while for manufacturers, it has been less explored and utilized. To fill the gap, the dissertation first proposes a cost-effective sizing model to identify the capacities as well as control strategies of the components in microgrids considering a commonly used energy tariff, i.e., Time of Use (TOU). Then, the sizing model is extended by integrating control strategies for both microgrid components and manufacturing systems considering a typical demand response program, i.e., Critical Peak Pricing (CPP), where customer side load adjustment is highly encouraged. After that, the control strategy of the manufacturers in an overgeneration mitigation-oriented demand response program is further investigated based on the identified optimal size of onsite microgrid to minimize the energy cost. Later, the system is analyzed from its higher level of abstraction where a prosumer community is developed by aggregating such manufacturers with onsite microgrid system. To enhance the reliable energy operation in the community, the performance of the microgrid is investigated through the estimation of the lifetime of Battery Energy Storage System (BESS), a critical design parameter the architecture. Finally, conclusions are presented and future research on real-time joint control strategy for both microgrids and manufacturing systems and identification as well as optimal energy management of the controllable loads in manufacturing system are discussed --Abstract, page iii

Optimal Planning of Microgrid-Integrated Battery Energy Storage

Battery energy storage (BES) is a core component in reliable, resilient, and cost-effective operation of microgrids. When appropriately sized, BES can provide the microgrid with both economic and technical benefits. Besides the BES size, it is found that there are mainly three planning parameters that impact the BES performance, including the BES integration configuration, technology, and depth of discharge. In this dissertation, the impact of each one of these parameters on the microgrid-integrated BES planning problem is investigated. Three microgrid-integrated BES planning models are developed to individually find the optimal values for the aforementioned parameters. These three microgrid-integrated BES planning models are then combined and extended, by including the impact of microgrid islanding incidents on the BES planning solution, to develop a comprehensive planning model that can be used by microgrid planners to simultaneously determine the installed BES optimal size, integration configuration, technology, and maximum depth of discharge. Besides applications in microgrids, this dissertation investigates the integration of BES to provide other types of support in distribution networks such as load management of commercial and industrial customers, distribution network expansion, and solar PV ramp rate control

Feasibility Study of Energy Storage Technologies for Remote Microgrid’s Energy Management System

Energy storage systems (ESSs) play a significant role in remote microgrids energy management system (EMS) with the large penetration rate of renewable energy which is intermittent in nature. Energy storage improves system reliability and efficiency in remote microgrids by optimizing the power demand and generation to reduce operational costs. Moreover, it increases the dispatch ability of the energy sources in remote microgrid systems. Lead acid battery (PbA) can be used as an energy storage device in remote microgrids due to its low cost; however, the response rate, short life cycle, and depth of discharge (DoD) lead to high operational costs. Ultracapacitor has a considerably longer life cycle, its energy density is low, and the initial cost is very high. Lithium-ion (Li-ion) and hybrid ion batteries may have comparatively better economical prospects in terms of DoD, life cycle, and operational cost. In this thesis, different energy storage technologies are considered for remote microgrids energy management systems. In addition, the Schiffer weighted Ah throughput model introduces two weight factors to describe that a battery degrades faster in real time operation than the standard test conditions due to different stress factors. These weight factors virtually increase the battery throughput, and accelerate the degradation. To mitigate this problem, different periodical and auto cycling strategies were investigated in this thesis. However, the results demonstrated that frequent full charging prevents the battery from over degradation. Auto cycling strategy was found more cost effective than the periodical cycling. Applying this cycling strategy, the yearly total operational cost of a microgrid system with a 142 kWh PbA battery bank was reduced by 0.62% ($826). Results also showed that the wear cost is an important factor to consider while designing the energy management system. Li-ion and hybrid-ion batteries had lower wear costs and showed great potentiality, although the EMS with a Li-ion battery was found to be 2.55% more cost effective and 1.5% more fuel efficient than hybrid ion batteries. The reduction in operational cost ensures the access to low cost electricity for the people in remote areas. It will accelerate the development of industries, communications, technologies, and the standard of living including the remote health clinics in those areas. Furthermore, the reduction in generators fuel consumption will reduce CO2 emission which will lower the global warming and the greenhouse effect. In this thesis, one of the objectives was to prolong the battery lifetime by preventing the degradation, that may lower the number of yearly battery disposals which are hazardous to the human health and the environment

Power Management of Remote Microgrids Considering Battery Lifetime

Currently, 20% (1.3 billion) of the world’s population still lacks access to electricity and many live in remote areas where connection to the grid is not economical or practical. Remote microgrids could be the solution to the problem because they are designed to provide power for small communities within clearly defined electrical boundaries. Reducing the cost of electricity for remote microgrids can help to increase access to electricity for populations in remote areas and developing countries. The integration of renewable energy and batteries in diesel based microgrids has shown to be effective in reducing fuel consumption. However, the operational cost remains high due to the low lifetime of batteries, which are heavily used to improve the system\u27s efficiency. In microgrid operation, a battery can act as a source to augment the generator or a load to ensure full load operation. In addition, a battery increases the utilization of PV by storing extra energy. However, the battery has a limited energy throughput. Therefore, it is required to provide a balance between fuel consumption and battery lifetime throughput in order to lower the cost of operation. This work presents a two-layer power management system for remote microgrids. The first layer is day ahead scheduling, where power set points of dispatchable resources were calculated. The second layer is real-time dispatch, where schedule set points from the first layer are accepted and resources are dispatched accordingly. A novel scheduling algorithm is proposed for a dispatch layer, which considers the battery lifetime in optimization and is expected to reduce the operational cost of the microgrid. This method is based on a goal programming approach which has the fuel and the battery wear cost as two objectives to achieve. The effectiveness of this method was evaluated through a simulation study of a PV-diesel hybrid microgrid using deterministic and stochastic approach of optimization

Optimal integration of wind energy with a renewable based microgrid for industrial applications.

Wind energy in urban environments is a rapidly developing technology influenced by the terrain specifications, local wind characteristics and urban environments such as buildings architecture. The urban terrain is more complex than for open spaces and has a critical influence on wind flow at the studied site. This approach proposes an integration of the surrounding buildings in the studied site and then simulating the wind flow, considering both simple and advanced turbulence models to quantify and simulate the wind flow fields in an urban environment and evaluate the potential wind energy. These simulations are conducted with an accessible computational fluid dynamic tool (Windsim) implementing available commercial wind turbines and performed on a case study at Agder county in the southern part of Norway for an industrial facility specialized in food production. Several simulations were considered and repeated to achieve a convergence after adding the buildings to the domain, which mainly simulates the wind flow patterns, power density, and annual energy production. These simulations will be compared with previous results, which adapted different manipulation techniques applied on the same site where the elevation and roughness data were manipulated to mimic the actual conditions in the studied urban site. The current approach (adding the buildings) showed a reduction in the average wind speed and annual energy production for certain levels with increased turbulence intensity surrounding the buildings. Moreover, a feasibility study is conducted to analyze the techno-economic of the facility's hybrid system, including the planned installation of a wind energy system using commercial software (HOMER). The simulation results indicated that HOMER is conservative in estimating the annual energy production of both wind and solar power systems. Nevertheless, the analysis showed that integrating a wind turbine of 600 kW would significantly reduce the dependence on the grid and transform the facility into a prosumer with more than 1.6 GWh traded with the grid annually. However, the proposed system's net present cost would be 1.43 M USD based on installation, maintenance, and trading with the grid, without including self-consumption, which counts for approximately 1.5 GWh annually. Moreover, the proposed system has a low levelized cost of energy of 0.039$ per kWh, which is slightly above the levelized cost of wind energy but 2 to 4 times less than the installed solar panels

Integration, control and optimization of the solar photovoltaic-battery system in microgrids

This document composes the work realised and the research results developed within the scope of electric energy storage at the Renewable Energy Chair of the University of Évora. The current legal and technological framework of electrochemical energy storage technologies is reported, and its framework is demonstrated in the Portuguese and European contexts. Next, the experimental microgrid that comprises several electric energy storage technologies is described. The lithium-ion and vanadium redox flow technologies were tested and characterized for later validation of the electrical models that describe their performance. A state-of-the-art review allowed the experimentation of energy management strategies that fit the technologies studied, allowing smarter management in residential and services sectors. In this thesis, management algorithms, battery models, and an indication of technical, economic and energy parameters were combined in a tool to study the simulation of the operation of these technologies, allowing to define different operating objectives, fine-tune parameters and even join the operation of different technologies. This work was accompanied by national and international projects, attempting to respond to existing problems in the operation of real systems and gaps identified in the design phase, such as a robust dimensioning tool, with the integration of different battery managing methods; Integração, controlo e otimização do sistema solar fotovoltaico-bateria em microrredes Resumo: Este documento compõe o trabalho realizado e respetivos resultados da investigação desenvolvida no âmbito do armazenamento de energia elétrica na Cátedra Energias Renováveis da Universidade de Évora. Os atuais enquadramentos legais e tecnológicos das tecnologias eletroquímicas de armazenamento de energia são relatados, nos contextos português e europeu. Seguidamente, uma microrrede experimental que inclui diversas tecnologias de armazenamento de energia elétrica é descrita. As tecnologias de fluxo redox de vanádio e de iões de lítio foram objeto de ensaio e caracterização, para posterior validação dos correspondentes modelos que descrevem a sua performance elétrica. A revisão do estado da arte permitiu a experimentação de estratégias de gestão de energia que se adequam às tecnologias estudadas, que permitam a sua gestão inteligente, no contexto residencial e de serviços. Nesta tese, os algoritmos de gestão, os modelos das baterias, a indicação de parâmetros técnicos, económicos e energéticos foram combinados numa ferramenta para estudo da simulação da operação destas tecnologias permitindo definir diferente objetivos, afinar parâmetros e até operar conjuntamente diferentes tecnologias. Este trabalho foi acompanhado pelo paralelismo de projetos nacionais e internacionais, tentado dar resposta a problemas existentes na operação de sistemas reais, e lacunas identificadas na fase de projeto, tal como uma ferramenta de dimensionamento robusto, com a integração de diferentes formas de gerir baterias