Optimal sizing of storage technologies for on-grid and off-grid systems




Rahimzadeh, Azin

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The challenge of managing the present and projected electricity energy needs along with targets of mitigating CO2 emissions leads to the need for energy systems to reduce reliance on fossil fuels and rely on more energy from renewable sources. The integration of more renewable energy technologies to meet present and future electricity demand leads to more challenges in matching the trade-o between economic, resilient, reliable and environmentally friendly solutions. Energy storage technologies can provide temporal resilience to energy systems by solving these challenges. Energy storage systems can improve the reliability of energy systems by reducing the mismatch between supply and demand due to the intermittency of renewable energy sources. This thesis presents a comprehensive analysis of various energy storage systems, analyzing their speci c characteristics including capital cost, e ciency, lifetime and their usefulness in di erent applications. Di erent hybrid energy systems are designed to analyze the impacts of renewable and non-renewable energy sources and energy storage systems in residential on-grid and o -grid buildings and districts. An optimization analysis is performed to determine which technology combinations provide the most economic solution to meet electric energy demands. The optimization analysis is solved using the "energy hub" model formulation which optimizes energy system operation and capacity of di erent technologies. Di erent energy systems can be optimized by using energy hub model, including multiple input energy carriers that are converted to multiple energy outputs. The analysis in this thesis employs a building simulation tool to model residential building, and real data sets to explore the di erent electricity pro le e ects on the results. The environmental e ect of hybrid energy systems comparing with base cases of conventional energy systems or grid connection are also analyzed. Results show that the feasibility of energy storage systems is a factor of di erent variables including capital cost of energy converters and energy storage systems, cost of input streams (grid electricity in on-grid systems and diesel fuel in o -grid systems, energy demand pro les and availability of renewable energy sources. The on-grid single and district buildings do not select storage technologies at current costs due to cheap grid electricity. Reduction in the cost of renewable energy technologies and/or energy storage systems (e.g. Li-ion batteries) results in more energy storage installations. In o -grid systems (single buildings and districts), Li-ion battery and pumped hydro are the main storage systems that can balance the daily and seasonal energy demands.



Storage technology, Hybrid energy system, On-grid system, Off-grid system