Thermodynamic modeling and analysis of a novel hybrid energy storage based on solar energy utilization

Abstract

This paper proposes and studies a novel hybrid energy storage system with solar collectors, photovoltaic modules, and a combined cooling, heating, and power (CCHP) unit. The cold production in the CCHP unit in two versions of the refrigeration loop is considered. The proposed technical solution provides simultaneous production and supply of electricity, heat, and cold to consumers. It also allows efficient accumulation and use of solar energy, generated electricity, and the heat of superheated CO2 vapor in the mechanical compression cooling cycle. The effect assessment of changes in operating conditions on the system’s characteristics has been performed using parametric analysis based on energy methods. The analysis results show that the proposed system provides a high value of RTE (up to 0.137) and SSEE (up to 2.77) reflecting the energy efficiency of the CCHP unit and the storage system, respectively. The maximum system’s efficiency is achieved at low evaporating temperatures in the cooling cycle and at the heat exchanger HE2 outlet, low pressures in the low-pressure tank, and high pressures in the high-pressure tank. The low evaporating temperatures in the mechanical compression cooling cycle also ensure the most efficient implementation of the heat storage system, and as a result, the maximum values of the hot fluid utilization rate HFUR (up to 0.87). The study also shows that the ejector cooling cycle application is irrational due to low cooling capacity and a limited operating condition range. Its use does not lead to a noticeable increase in system energy efficiency (0.1–9.4 %) with a noticeable system design complication.