Author: Liu, Jia
Title: Study on hybrid renewable energy and electrical energy storage systems for power supply to buildings in urban areas
Advisors: Yang, Hongxing (BSE)
Cao, Sunliang (BSE)
Degree: Ph.D.
Year: 2021
Award: FCE Awards for Outstanding PhD Theses (2021/22)
Subject: Hybrid power systems
Buildings -- Power supply
Hong Kong Polytechnic University -- Dissertations
Department: Department of Building Services Engineering
Pages: xxix, 259 pages : color illustrations
Language: English
Abstract: The building sector accounts for 30% of the global final energy use and 28% of energy-related carbon emissions in 2019 as the largest contributor in the world, where reductions of 13% and 50% are expected to be achieved by 2040 from 2018 levels according to the International Energy Agency's sustainable development scenario. Renewable energy is projected to share up to 86% of total electricity generation and all buildings must adopt renewable energy strategies by 2050, to meet net-zero energy and net-zero carbon requirements at community scales. It is of great significance to develop renewable energy applications for power supply to buildings and communities in urban areas, as majority of carbon emissions in a country are mainly attributed to just several domestic cities. Especially for high-density cities like Hong Kong, the second largest carbon emitter in China, its building sector accounts for over 90% of total electricity consumption and 60% of carbon emissions. Renewable energy sources, such as solar photovoltaic power and wind power, are usually intermittent and unstable depending on weather conditions, and therefore not consistent with the fluctuating building energy demand. So electrical energy storage technologies, such as battery and hydrogen storage, should be integrated with renewable energy systems to enhance the energy autonomy and flexibility. This thesis presents a comprehensive and systematic study on the hybrid renewable energy and electrical energy storage systems for power supply to both a single building and building communities in urban regions, for achieving carbon neutrality in the near future. The novel energy management strategies, flexible grid integration models, robust system planning optimizations, and systematic peer-to-peer energy trading management and optimization platforms are proposed for the hybrid renewable energy and storage system developments. Applications of typical electrical energy storage technologies are investigated, including stationary battery storage, mobile battery vehicle storage, mobile hydrogen vehicle storage and their hybrids, by practical experiments, transient system simulations (TRNSYS), coupled multi-objective optimizations (jEplus+EA), techno-economic-environmental assessments and sensitivity analyses. Firstly, novel energy management strategies, robust energy planning, improved technical and economic evaluation criteria, and integrated design optimization approaches of hybrid renewable energy and storage systems are developed in this thesis, for power supply to a single building in urban areas by establishing transient simulation models validated by practical experiments. Specifically, an effective design optimization framework of a photovoltaic and battery storage system is developed for a real low-energy building in Shenzhen of China, proposing a novel energy management strategy considering the battery cycling aging, grid relief and local time-of-use pricing. Both single-criterion and multi-criterion optimizations are conducted by comprehensively considering technical, economic and environmental performances of the system. Meanwhile, improved technical and economic optimization criteria of hybrid renewable energy and storage systems are proposed for typical system applications in a standard high-rise residential building in Hong Kong, including photovoltaic systems, hybrid photovoltaic-wind systems and hybrid photovoltaic-wind-battery systems. A comprehensive technical optimization criterion is proposed integrating the energy supply, battery storage, building demand and grid relief indicators. And the improved levelized cost of energy considering detailed renewable energy benefits is formulated including the feed-in tariff, transmission loss saving, network expansion saving and carbon reduction benefits. The practical experiments on a photovoltaic and battery storage system, under the maximizing self-consumption and time-of-use strategies, are conducted to study the system performance and validate the energy balance based battery and energy management models.
Moreover, a robust energy planning and optimization approach for hybrid photovoltaic-wind systems integrated with stationary battery and mobile hydrogen vehicle storage is developed, for a typical high-rise residential building in Hong Kong, considering different vehicle-to-building schedules. Two energy management strategies with different priorities of battery and hydrogen storage operations are proposed to compare and optimize the impact of charging and discharging orders of the battery tank and hydrogen vehicle storage on the system technical and economic performances. Multiple design criteria including the supply performance, grid integration and lifetime net present value are formulated, to size the hybrid system and select the optimal energy management strategy. Four decision-making strategies based on the minimum distance to the utopia point and analytical hierarchy process methods are applied, to determine the final optimum solutions for major stakeholders with different preferences (i.e. the end-user, transmission system operator and investor) for high-rise residential building applications within urban contexts. Secondly, novel time-of-use grid penalty cost business models, peer-to-peer energy trading price models, time-of-use peer-to-peer energy trading management and optimization platforms of hybrid renewable energy and electrical energy storage systems are proposed, for power supply to a large-scale net-zero energy building community integrated with hydrogen vehicles and battery vehicles in urban areas with high power flexibility and grid economy. In detail, novel time-of-use grid penalty cost business models for hybrid renewable energy and storage systems are developed to improve the power flexibility and economy between net-zero energy community systems and the utility grid. A net-zero energy building community is established with fundamental units of university campus, commercial office and high-rise residential building groups, based on actual energy use data and simulations as per surveys and codes in Hong Kong. Hybrid renewable energy systems integrated with stationary batteries and three hydrogen vehicle groups following different cruise schedules are firstly applied for power supply to the community microgrid as shared energy supply and storage. Four net-zero energy building and community scenarios are established with multi-objective optimizations to size the renewable energy and storage systems. Additionally, a dynamic peer-to-peer energy trading management platform is developed for the diversified net-zero energy community powered by hybrid renewable energy and hydrogen vehicle storage systems, with innovative peer trading price model and time-of-use peer trading management approaches. An individual peer-to-peer energy trading price model is proposed to allocate individual peer selling/buying price to each building group according to its intrinsic supply demand feature and grid import price in the diversified community. The time-of-use peer energy trading management strategies for both uniform and individual energy trading price modes are further developed based on the time-of-use grid penalty cost model, to improve the power flexibility and economy of the utility grid. The techno-economic-environmental performances of peer-to-peer energy trading management cases are then clarified compared with the baseline case with only peer-to-grid energy trading. The lifetime net present value of hybrid renewable energy and hydrogen vehicle storage systems in the current cost and future cost scenarios is discussed, to provide economic references for key stakeholders to develop net-zero energy communities. Furthermore, the peer-to-peer energy trading management and optimization approaches are developed for hybrid renewable energy systems with energy storage of hydrogen and battery vehicles applied in the diversified net-zero energy community. Typical net-zero energy community models are developed and compared with different energy storage vehicle types (hydrogen vehicle/battery vehicle) and energy trading modes (peer-to-grid/peer-to-peer). Multi-objective peer-to-peer trading optimizations of the net-zero energy community integrated with both hydrogen vehicles and battery vehicles are conducted to find optimal configurations of vehicle numbers and time-of-use management operations. An improved peer-to-peer trading management strategy is further proposed considering the peer trading priority and complementary operations of hybrid vehicle storages, to enhance the grid integration, decarbonisation and economy. It provides significant references for stakeholders to apply renewable energy and green vehicle storage systems towards carbon neutrality in integrated building and transport sectors in urban areas. The above study on hybrid renewable energy and electrical energy storage systems for power supply to both a single building and large-scale communities can help researchers and policy makers to evaluate the technical, economic and environmental feasibility, regarding the energy demand, energy supply, energy storage, energy management and grid integration aspects. The systematic research methodology and framework on the hybrid renewable energy and storage systems can provide significant guidance for relative stakeholders to develop renewable energy applications in the integrated building and transport sectors to accelerate the progress of carbon neutrality within urban contexts.
Rights: All rights reserved
Access: open access

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