Analysis And Comparison Of Different Control Strategies For Hybrid Ground-Source Heat Pump Systems

This paper refered to the development of hybrid ground-source heat pump systems domestic and abroad. Problems in project design and application were considered and two kinds of hybrid ground-source heat pump systems commonly seen which were the cooling tower-ground source heat pump system and the boiler-ground source heat pump system were simulated. The optimal control strategies and recommends of optimization for different systems were carried out.Tow representative cities of Wuhan and Haerbing were chosen according to the applicable areas of hybrid ground-source heat pump systems and the climatic characteristics in China. A small-sized office building was chosen and two kinds of systems mentioned above were designed on it. Those two systems were simulated for a long time period on different control strategies by the instantaneus simulate software TRNSYS and heat balance and energy consumption were also analyzed and compared. Some major components'peak electricity consumptiion, valley electricity consumption, annual average electricity consumption and total electricity consumption were calculated on the basis of data from simulation. The running costs then were estimated according to the principle of time-share charge.Tow main factor of heat balance and energy consumption on the condition of long term running hybrid ground-source heat pump systems were applied and came to the following conclusion.For cooling tower-ground source heat pump system, differential temperature control with difference between the heat pump exiting fluid temperature and the ambient air wet-bulb temperature activated is the optimum scheme. Under this control strategy, not only the long term heat balance achieves the best state, but also the total running cost appeares the lowest. It takes advantage of the storage capacity of the ground heat exchanger and the soil by"storing cold"in the ground during the winter, then trjects heat when conditions are advantageous in the spring, summer, and fall.For boiler-ground source heat pump system, set point control for heat pump entering fluid lowest temperature is the optimum scheme. Under this control strategy, not only the long term heat balance achieves the best state, but also the total running cost appears the lowest. It avoids the energy wastes of running the supplemental heating equipment for long time period.The optimal ways and methods about hybrid ground-source heat pump systems were discussed and expounded at the end of this paper for futher application and extension.