Application And Optimization Of Energy Storage Systems In Building Energy Flexibility And Retrofitting

Energy-saving-retrofitting and building energy flexibility of existing buildings are important ways to achieve the goal of "Carbon Peaking and Carbon Neutrality " in the China’s building sector.At present,the cold and heat source scheme with electricity chiller for cooling and gas boiler for heating is adopted in a great deal of public buildings in hot summer and cold winter zones,the power demand for air conditioning and refrigeration is still dominated by the power grid,and the demand for building air conditioning load fluctuates greatly.Especially,the energy consumption increases sharply during air conditioning in summer and space heating in winter,which brings great pressure and challenge to the stable operation of the power grid.Under the background of the vibrant prosperity of photovoltaic(PV)buildings,how to retrofit and renovate the cold and heat source system of these existing buildings,make full advantage of solar PV power generation and promote the energy flexibility of buildings is of great significance to building energy conservation and safe operation of power grid.Based on the universally accepted cold and heat source scheme with electricity chiller and gas boiler in public buildings in hot summer and cold zones,the building cold and heat energy storage system and building PV-battery energy storage were designed to provide energy-saving-retrofitting and building energy flexibility solution in hot summer and cold winter zones.The main research contents and results are as follows:Firstly,the mixed integer nonlinear program mathematical models of two kinds of building energy storage systems were established,taking the total cost of the whole service life cycle and the minimum annual carbon emission of the energy storage system as the objective function,the capacity confirmation and system operation of the energy storage systems were optimized based on the bi-level optimization method framework.From the perspective of technical economy and building energy flexibility,the applicability of building cold and heat energy storage system and PV-BESS in building energy-saving transformation in hot summer and cold winter areas was studied.The results showed that the building cold and heat energy storage system could reduce by 32.7% of the operation cost,and the potential of building energy flexibility was68.6%;the PV-BESS could reduce by 40.3% of the operation cost,and the potential of building energy flexibility for PV-BESS was 78.9%.Secondly,the influences of grid export power limit,grid import power limit,and peak feed-in-tariff on the capacity configurations of building energy storage systems were analyzed in this paper.The results indicated that with the increases of the grid export power limit,the optimal capacity configuration of the building cold and heat energy storage system also increases.With the increases of grid export power limit,grid import power limit and peak feed-in-tariff,the optimal capacity configuration of PV-BESS also increased.The grid export power limit of power grid had greater impacts on the capacity configuration of two kinds of energy storage systems.Finally,the techno-economy performance and operation performance of building cold and heat energy storage system and PV-BESS were compared and analyzed,and the applicability and adaptability of the two kinds of energy storage systems in building energy-saving and energy flexibility retrofitting in hot summer and cold winter areas was discussed.The results revealed that the initial investment cost of the building cold and heat energy storage system in building energy-saving-retrofitting program was the lowest,and the relative investment payback period was 0.175 years,and 52.4% of annual carbon emissions could be reduced by the building cold and heat energy storage system;the initial investment cost of the PV-BESS was 9.5 times of that of the building cold and heat energy storage system,the relative investment payback period was 2.34 years,with an increase of 14.3% of annual carbon emissions.This study provides theoretical support and guidance for the planning,design and application of energy storage systems in building energy-saving and energy flexibility retrofitting in hot summer and cold winter areas.