Comparison of two hybrid renewable energy systems for a residential building based on sustainability assessment and emergy analysis

High energy consumption along with the diversity of its species in the building section is one of the most important challenges for sustainable development. The use of solar energy in multi-generation systems is a new solution that has been considered by researchers. In this study, an integrated multi-generation solar energy system with the aim of supplying the demands of fresh water, electricity and heating of a building, as a case study, in the city of St. Petersburg has been suggested. The proposed system has PVT and PTC collectors, hot water storage tanks, heat exchangers, an electrolyzer, a hydrogen storage tank and a hydrogen engine for the purpose of production, storage and consumption of hydrogen. To evaluate the environmental and economic performance of the proposed system, initially, the performance of this system was evaluated and compared based on emergy analysis in two scenarios with and without desalination unit during one year. The difference between the two scenarios is the existence of a thermal water purification system in one scenario with the aim of supplying fresh water to the building and electrolyzer. In the first step of the study, the results showed that the system in scenario of without desalination unit has better performance in the viewpoint sustainability with higher environmental sustainability index (ESI) value, more dependence on environmental resources and lower investment costs. Also, in the second step, the stability performance of the system from emergy viewpoint for scenario without desalination unit in the climatic conditions of the four cities of St. Petersburg, Khabarovsk, Yakutsk and Moscow were evaluated. The results showed that the integrated energy system in the scenario without desalination unit with environmental sustainability index of 1.13 in the climatic conditions of the city of Khabarovsk is environmentally and economically sustainable.