Technical Assessment of a Hybrid Solar-geothermal System Including Adsorption Refrigerator for Energy Supply to Restaurants in Smart City

Abstract

CO2 emissions from restaurants have increased over the past five years in Japan. As a result, countermeasures such as hybrid heat source systems that use renewable energy have gained increasing attention. In this paper, we assessed the efficiency of a hybrid solar-geothermal heat system including an adsorption refrigerator during its use in providing energy for air conditioning and hot water. We presented an energy prediction formula based on measured data on solar heat collection, cooling, and heating load. We also documented our evaluation of the performance of each component of the solar-geothermal heat system, i.e. the solar collector, adsorption refrigerator, and geothermal heat pump. And finally, we presented a case study on the use of this system in restaurants in a smart energy town in Japan. On solar collector, this study found that the heat collection efficiency during sunny and mostly sunny conditions were 28%. This percentage dropped to 23% for cloudy conditions and 11% for rainy conditions. On adsorption refrigerator, the Coefficient of Performance (COP) in summer was found to be lower than in autumn. On geothermal heat pump, the COP was found to be 4.5 during the cooling period and 4.3 during the heating period. Overall, the highest values for both energy consumption and energy utilization occurred in August, and the utilization efficiency was lower in winter than in summer. Moreover, the average annual energy utilization efficiency of the total system was 59.02%, while the Annual Performance Factor (APF) was 2.082. This study contributes to decision making and academic researches regarding the planning and implementation of energy-efficient cooling and heating system.