Operations Research Of Ground Source Heat Pump System At Comprehensive Energy Station

With the rapid increasing of residential building area in China, energyconservation and emissions reduction in the construction field become importantaspects of the sustainable development in recent years. So, heating and airconditioning are with greatest potential in energy conservation and emissionsreduction as they account for a large portion of the building energy consumption.District heating and cooling system is the effective means to realize building energyconservation and emissions reduction. In this system, whose cold and heat source ismainly supplied by ground-source heat pump (GSHP). In recent years, GSHP hasreceived more attention, with the ground heat exchanger used as the heat source andheat distribution, because this kind of GSHP can not only increase the utilization ofrenewable energy, but also improve energy efficiency. It is different from GSHP usedin the individual building that most GSHP construct a compound system combinedwith other hot and cold sources in district heating and cooling system. The efficiencyof different cold and heat sources is different. The quantity of building load undertookby GSHP influences temperature change of the ground, thereby affecting theoperation efficiency of heat pump. So load balancing between GSHP and other coldand heat sources will be beneficial to optimize the operation of district heating andcooling system.A comprehensive energy station of Tianjin was researched. This article firstanalyses the energy saving properties of various cold and heat sources and operatingconditions of GSHP by monitoring a lot of operating data. The results showed that inthe heating mode, the GSHP could save energy by19.0%than using the gas boiler. Inthe cooling mode, the GSHP could save energy by11.3%than electric refrigeratingsystem. In winter heating condition, the conditions of GSHP for direct supply energycould save energy by9.1%than energy storage condition, but energy storagecondition could save electricity fee by48.7%than the former. In summer coolingcondition, the conditions of GSHP for direct supply energy could save electricity by17.2%than energy storage condition, but energy storage condition could saveelectricity fee by44.8%than the former. The seasonal total transfer heat of groundheat exchanger affect the rise or fall of the outlet water temperature. The total heatextraction volume in2011winter is4.02times that of2012, resulting in that the falling range of the outlet water temperature in2011winter is1.56times that of2012.The total heat release volume in2013summer is1.14times that of2012, resulting inthat the rising range of the outlet water temperature in2013summer is1.07times thatof2012.In the end, an optimization plan for the energy station was made according to themonitor data make. Based on cylindrical heat source theory, a heat transfer modelwith variable heat flux was established, and a program was written using Visual Basic.This program could be used to predict the outlet water temperature change in groundheat exchanger system under different operating modes, and analyze theenergy-saving effect and operation costs of heat pump based on the watertemperatures predicted before. Suggested that GSHP first adopts the conditions forenergy storage, and avoid double unit open at the same time in winter. Thecomprehensive efficiency of the winter operation scheme is3.27, and the electricityfee of the unit heating capacity is51.6RMB/GJ. The comprehensive efficiency of thesummer operation scheme is5.41, and the electricity fee of the unit cooling capacityis41.4RMB/GJ. According to the proposal, the cooling capacity of GSHP is1.27times the heating capacity. After running five years, the outlet water temperature inwinter rise2℃, resulting in that the comprehensive efficiency of GSHP rise0.15.The outlet water temperature in summer rise1.1℃, resulting in that thecomprehensive efficiency of GSHP rise0.10.