Forecasting the performance of a district solar thermal smart network in desert climate – A case study

Abstract

The present paper investigates the performance of a district solar thermal smart network capable of providing the cooling, heating, and domestic hot water needs for a group of 100 villas in the desert climate of Riyadh, Saudi Arabia. Evacuated tube solar collectors are distributed over the villas’ roofs, while the hot water Lithium Bromide absorption chillers and hot phase change material thermal storage tanks are located in a centralized plant. Electrical heating elements embedded in the thermal storage tanks are considered as back up auxiliary sources in case of shortages. Using the “Design Builder” energy simulation program, a typical villa constructed as per the local thermal standard has been modeled to calculate the hourly thermal loads. These hourly profiles are the initial inputs for a Transient System Simulation (TRNSYS) model integrated with the Generic Optimization Program (GenOpt). The interaction between these two programs is used to find the optimized sizing of the solar collectors’ area and the hot thermal storage volume which could achieve the maximum thermo-economic performance with a 100% solar fraction. The hourly transient simulations over a one-year period show that this system can achieve up to 82.67% reduction in the annual electrical consumption as well as carbon dioxide emissions if compared to conventional district thermal plants. Furthermore, the smart network benefits have been revealed from three different aspects: generation source, transmission loop network, and end-user consumer. The feasibility analysis performed shows that adopting the smart network can enhance the profitability of the project by 34.89% if compared to central solar plants. Also, it gives the end-user the opportunity to participate in energy production through buying the solar collectors installed on their roofs, and thus further enhancing the reduction in their annual thermal bills from 23.13% to 82.88% in a payback period of 4 years and 11 months.