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A ground water heat pump system (GWHP) of a university in Tianjin was introduced, and the system was compared with the other two heating and cooling systems in this paper. The initial and operating cost was calculated, and then the advantages and disadvantages of the systems were analyzed. The results show that the GWHP system makes full use of geothermal energy, and it is better than the other two systems in economy and application. Introduction With the rapid development of our society and economy, there comes a large energy demand and the serious environmental pollution. It is imperative to develop some new clean and efficient energies. As one of the most promising energies, geothermal energy is rich and in huge reserves in our country [1]. GWHP is a new technology which extracts the energy of the earth, and then releases the energy to cool or heat buildings. The technology with great potential has been widely used in hospitals, schools and other public buildings. There are broad discussions and researches on the technology, and it has great practical significance to utilizing the energy and solving the environmental problem [2]. Working Principle The GWHP is an efficient HAVC system. It extracts the geothermal energy contained in the water, and then releases the energy to realize heating and cooling [3,4]. It is a new type of high grade energy saving technology, which pumps low-grade heat into high-grade thermal energy. The system is usually consisted of three parts: outdoor geothermal heat exchanger system, water source heat pump unit and indoor air-conditioning terminal system [5,6]. Working principle of GWHP can be described that extracting geothermal energy as the heat source to increase indoor temperature in winter and storing the indoor heat into earth in summer [7]. This form of energy supplies little pollution to environment, and mostly, users can get more than 4 kWh of heating or cooling capacity by consuming 1 kWh of power [8]. Application Case Introduction of an Actual Project. The project is located in a university of Tianjin. The total floor area of the university is 210,000 square meters and a planned cooling and heating area is about 175,000 square meters. The domestic hot water is supplied by two geothermal wells. One is used to pumping and another to injecting. The depth of the two wells is 2500 meters. The water yield of the pumping well is 90m3/h. Outlet temperature of geothermal water is 90°C, while through the plate heat exchanger, the temperature turns into about 62°C. Heating and cooling are realized by a GWHP system, the maximum heating load is 4000 kw in winter and the cooling load is 6200 kw in summer. The GWHP system supplies heat or refrigeration in an indirect way: geothermal water transfers heat to the circulating water of heating pipe network through a plate heat exchanger, and after its temperature declined, geothermal water will be back into a injection well. The device room of the system is located in the underground of 6th International Conference on Electronic, Mechanical, Information and Management (EMIM 2016) © 2016. The authors Published by Atlantis Press 1065 dining room which was consisted of one screw ground source heat pump units and 3 sets of centrifugal ground source heat pump units. Those devices provide refrigeration in summer and heating in winter for the entire campus buildings. Refrigerate conditions: inlet and outlet temperature of cooling water is 13/6°C, inlet and outlet temperature of the condenser is 30/35°C; heating conditions: input and outlet temperature of hot water is 38/45°C, inlet and outlet temperature of the evaporator is 9/5°C; The total power of the system is 3397.8 kw. The Simulation Schemes. There are three common methods of utilizing energy to supply heat and refrigeration at present, including the direct use of the municipal heating, the exploitation of geothermal energy and the use of natural gas. The economy and practicability of cooling and heating schemes are analyzed between the actual project and two simulation schemes, and the simulation schemes are shown blow. Plan a: Central-heating and central-cooling. Domestic hot water is supplied by both gas boiler and solar energy. In this plan, the university will get heat supplied by the municipal heating in winter and get refrigeration supplied by the refrigeration station in summer. Plan b: Gas direct-fired machines were used to supply domestic hot water, heat and refrigeration. In this plan all energy will be provided by gas direct-fired machines. Comparison and Analysis on Simulation Schemes. Initial and operating costs were used to be the major factors of economic comparison.The total initial cost includes the basic system, hot water system and the terminal system. And the costs of practical and simulation schemes are shown in Table 1-3. Table 1 Initial cost of the actual project Item Area[m 2 ] Unit price[¥/m] Total price [1000¥] Cost of geothermal well system 2,500 2,600 1,300 Cost of domestic hot water system 1,000 Cost of refrigeration station 3 GWHPs; 24 circulating water pumps; 6 plate heat exchangers and pipelines; 4 domestic hot water pumps; drilling system 23,000

Application and Analysis for Ground Water Heat Pump System of a University in Tianjin