The impact of different solar thermal technologies and climate zones on thermo-economic performance of hybrid district space heating system integrated with seasonal thermal energy storage.

Abstract

Fossil fuels are being used to accommodate domestic heating needs all over the world and the alarming rise in carbon footprint is demanding from the world to shift towards renewable energy technologies. A key strategy to lessen household fossil fuel consumption is a solar hybrid district heating network integrated with seasonal thermal energy storage (TES). The objective of this study is to analyze and compare the thermoeconomic performance of solar hybrid district heating system integrated with borehole TES system in Pakistan’s five climate zones and identify the best suitable solar thermal collector technology. Based on the solar energy incident on different types of thermal collectors, a validated TRNSYS model is used to investigate the dynamic performance indices i.e., solar fraction, system efficiency, and thermal storage efficiency. The heat demand model and weather-related data are changed as input to the system. On basis of mentioned performance indices, climate Zone-C is selected as the most suitable and Zone- E as least favorable among five different zones with a seasonal storage efficiency of 61% and 19% respectively. Solar fraction is about 91% also up to the mark as the purposed system utilizes both solar energy and auxiliary systems. Further, the implementation of different thermal collector technologies PTC, ETC & FPC has revealed that the thermal efficiency of ETC is best among all with the highest value of 65%, followed by PTC 44%, and FPC shows the least efficiency of 36%. The economic analysis shows that the model embedded with ETC has a minimum payback period of 6.93 years followed by FPC of 7.22 years and a maximum for PTC of 7.38 years. The analysis presented in the current study provides guidelines for researchers and policymakers to identify acceptable location-based best solar thermal collector technologies coupled with seasonal thermal storage for district space heating.