Multi-objective optimisation of a seasonal solar thermal energy storage system for space heating in cold climate

Abstract

Seasonal solar thermal energy storage (SSTES) system is a promising technology to minimise greenhouse gas emissions (GHGE) by harnessing solar energy for space heating applications. The SSTES system in this study includes double U-tube borehole heat exchanger, ground-coupled heat pump and evacuated tube solar collectors. The aim of this investigation is to optimise the design variables of a SSTES system for space heating in cold climate locations. Six cold climate locations were studied namely: Lukla (Nepal), Dras (India), Sivas (Turkey), Harbin (China), Ulaanbaatar (Mongolia), and Verkhoyansk (Russia). The optimisation variables considered are the total solar collector area and total borehole length. There are three separate optimisation investigations: two single-objective and one multi-objective for the SSTES system. The first investigation is to minimise total life cycle greenhouse gas emissions and the second investigation is to minimise total life cycle cost included cost of GHGE. The third investigation is to minimise both life cycle cost of SSTES system and cost of GHGE (multi objectives). The simulation model was developed using TRNSYS 17 and the Multi-Objective Building Optimisation (MOBO) tool was applied for optimisations. The optimal set of design variables and the corresponding value of the objective function were determined for each single-objective optimisation investigation. Pareto front for each location was also identified for the multi-objective optimisation investigation. The technical and financial performance were also analysed and presented.