Energy and thermal storage in clusters of grid-independent buildings

Abstract

The extensive substitution of fossil fuels with renewables creates the U-shaped demand curve (duck curve) problem which is exacerbated in the summer months with the extensive use of air-conditioning. This study examines the hourly, daily, and yearly operation of a cluster of one hundred grid-independent buildings that completely rely on photovoltaics for electricity generation, including their air-conditioning needs. The cluster stores energy in hydrogen as the seasonal storage medium and chilled water for cooling as the daily storage medium. Thermal storage of chilled water and the use of efficient air-conditioning (refrigeration) equipment significantly reduces the needs for the generated electric energy and stored energy: The utilization of thermal storage in addition to chemical storage has three beneficial results: a) it reduces by about 40% the needed solar power installation; b) it reduces by a factor of three the losses associated with energy storage; and c) it reduces by factor of four the necessary hydrogen storage capacity. The improved performance of the system is expected to significantly reduce the overall cost associated with grid independent buildings.