Operating Performance Research Of Cumulative Cold And Heat Load Ratio On Two Types Of Ground-Source Heat Pump Systems

Nowadays, ground source heat pump (GSHP) system gains more and more attention because of its energy conservation and high efficiency. But heat and cold load are uneven in hot summer and cold winter zone which leads to the GSHP system’s thermal accumulation. GSHP system with auxiliary cooling device can help ease that problem. At present, the commonly used systems in China are as follows:one is hybrid GSHP system with cooling tower, the other is GSHP system combined with chillers. However, due to many factors during the design and construction, a certain degree of thermal accumulation still exists in the actual project. Meanwhile, there are so many GSHP systems used in large public buildings in China. As is known, some areas in public building still need to be cooled in winter. As a result, cumulative load of building between summer and winter become bigger than usual. So the operating performance research of cumulative cold and heat load ratio on large public buildings’GSHP system is worth exploring.This paper selects a Wuhan office building as the simulation object. DeST-C is proposed to get building’s full-year dynamic load. Take this model as the prototype, different building models can be built though enlarging or narrowing the area of each floor and changing the floor number. Finally, different cumulative cold and heat load ratio is obtained. And these rate interval is relatively uniform in order to make this study more persuasive. TRNSYS is the tool to simulate the running of two kinds of GSHP systems of different cumulative cold and heat load ratio models for20years. Then, variation tendency of average soil temperature and energy consumption of the GSHP system (including heat pump, chiller, water pump and cooling tower) is available to analyze different systems. After that, the unit energy consumption (i.e. the electrical energy needed to get per kilowatt of cooling or heating capacity) of each system can be calculated to give an economic evaluation.Two key indicators which are average soil temperature and the unit energy consumption of GSHP system in20years are analyzed. Thus the following conclusions are drew:(1) For hybrid GSHP system with cooling tower, with the increase of cumulative cold and heat load ratio, average soil temperature grows and the speed is higher. What’s more, the inlet temperature of heat pump rises as well as the system’s unit energy consumption.(2) For GSHP system combined with chillers, if system is designed by the method which thinks the summer and winter peak load is equal, soil thermal accumulation will be extremely serious. So, total heat absorption and releasing should be matched. This method is recommended in system’s optimization design.(3) Compare the two systems, the system with chillers needs more initial investment and less running costs of same models than the other one. Take initial investment and running cost, the system with chillers cost about18.9%less to get per kilowatt of cooling or heating capacity. When it comes to the comparison of the systems, the comprehensive analysis of whole life cycle investment and operation cost should be taken into consideration.This article analyzes the effect of thermal imbalance ratio on the operating performance of two kinds of GSHP systems. What’s more, the economy analysis of two systems is given to provide a reference for its further promotion and application in the future.