Operation optimization of a solar collector integrated with phase change material storage heating system

Abstract

Making full use of renewable energy for building heating is inevitable if energy structures are to be transformed and emissions are to be reduced. A solar collector integrated with a phase change material storage heating (SC-PCM) system is a promising distributed building heating technology. However, the feasibility and economic efficiency of the system in practical applications have rarely been studied. In this study, on-site measurement and model development for a SC-PCM system constructed for a three-storey office building in Tianjin were carried out. The accuracy of a self-developed phase-change heat transfer module, Type 668, and of a TRNSYS simulation model was verified by data from a 45-day on-site measurement. The mean relative error (MRE) of the on-site measurement and simulated data for the heat supply of the phase-change module was 7.8%. The MREs for indoor temperature and total daily heat supply of the entire SC-PCM system were 2.2% and 8.3%, respectively. The verified model was then used for a system-optimization study. Nine control strategies designed by the orthogonal method were compared, and it was proved that the control strategy VI (3-WV conversion condition: T3 < 43 °C close, T3 > 48 °C open; 3-PDV set value: 36 °C; EHF heating period: 23:00–5:00) is the optimal strategy for the current SC-PCM system. The energy consumption of strategy VI was 21,470 kW·h for 28 days, 21.4% less than that of the original strategy. A four-factor, three-level orthogonal design test was conducted to determine the effects of various parameters on a nonspecific SC-PCM system. It was concluded that the area of the solar collector (SC) has the greatest impact on indoor temperature, while the power of the electric heating furnace (EHF) has the greatest impact on the levelized cost of heat (LCOH). The TRNSYS model was used in combination with optimization solution tool GENOPT to obtain the optimal parameters of the system for different cities in China. The LCOHs in Tianjin and Shenyang were 16.4% and 17.5% lower, respectively, than the local flat electricity prices. It was demonstrated that the system has great application potential in areas with high heat demand and a significant peak valley power policy.