Status and development of hybrid energy systems from hybrid ground source heat pump in China and other countries

Hybrid energy systems (HES) facilitate the efficient utilization of renewable resources and sustainable energy, and they are expected to be more prevalent in the future. With ground source heat pump (GSHP) as the main body and core technology, the hybrid ground source heat pump (HGSHP) system is used frequently in recent years and its integration and synthesis skills face higher requirements. The worldwide hybrid system has usually been composed of types of energy source devices, such as solar collector, boiler (coal, gas, oil), electric heater, waste energy device, cooling tower, cooler, and thermal storage system with natural cold and hot. Actually, they lead to the complicated unsteady processes and various hybrid energy systems. In China, the applications of these systems are growing year by year, but the new technology breakthrough is being in difficulty and even in an awkward situation. This paper review the progress of GSHP combined with HES all over the world, and surveyed the development of HGSHP in China. Meanwhile, the basic proposals for development in the future are presented to make up the gap in the field of HES and HGSHP. A coming work aims to research the basic problems during the demonstration application, such as investigation of system design parameters, component configuration and control strategies of a HGSHP system. These problems will strengthen theoretical and practical understanding of HES and facilitate more extensive application of HGSHP in China.