Optimization and comparison of multiple solar energy systems for public sanitation service buildings in Tibet

Abstract

Qinghai Tibet Plateau, known as ‘Roof of the World’, is the highest and largest plateau on Earth, with an average elevation of 4900 m and spanning nearly two-thirds the size of the European continent. The energy consumption characteristics of public sanitation service buildings in the Qinghai Tibet Plateau are significantly different from traditional public buildings. It has unique advantages that allow these facilities to use the local enriched solar energy resources to meet the energy demand. This study proposes eight potential solar energy system schemes to obtain a suitable solar energy supply system and design an optimization method for public sanitation service buildings. The optimization models aimed at the life cycle cost for each solar energy system are established, and the equipment capacity in the system is optimized and simulated. Firstly, the optimized life cycle cost and equipment capacity of different solar energy system are compared and analyzed. Then, the short-term dynamic operation performance and the system's energy conservation, economic and CO2 emission reduction performance are comprehensively analyzed. Finally, the sensitivities of economic parameters and equipment price to the system optimization results are analyzed. The results indicate that the life cycle cost of the integrated solar hot water and heat storage system is 43% lower than that of the standalone solar hot air heat supply system and the standalone photovoltaic system. An optimized integrated system consisting of photovoltaic, photothermal, thermal storage, and power storage has the best comprehensive performance. The annual energy saving ratio of the integrated system is ∼85%, and the life cycle cost saving rate is about 50%. In addition, the sensitivity analysis shows that the electricity price is the most significant factor for life cycle cost compared to the annual interest and inflation rates. The price of a solar collector and air source heat pump have the most significant impact on the life cycle cost optimization results of a photovoltaic-photothermal-thermal and power storage integrated system.