| The plateau cold areas have features such as high altitude,low temperature,and long cold winter.The advantages of strong solar radiation and longer sunshine hours allow for rich solar energy resources in cold plateau areas.However,solar energy are unstable.As well as solar heating systems need auxiliary heat sources to ensure the continuity of heating.This paper combines solar energy and air source heat pumps,and find out the operating characteristics of a solar-air source heat pump combined heating system in a cold plateau region and optimize critical parameters by studying an office building in Lhasa.Through the comparison of residential buildings and office buildings,the dual-tank heating system is proposed as a solar-air source heat pump compound heating system to provide guidance in the application of cold plateau areas.First of all,this paper used DeST software to simulate and analyze the outdoor climate characteristics and the heat load of the office building in the plateau cold region represented by Lhasa,so as to provide a design basis for the heating system of office buildings in the plateau cold region.Secondly,the mathematical model of the solar-air source heat pump compound heating system was established.The mathematical models of the solar collector,air source heat pump,heat storage tank,circulating water pump and system control strategy are given in detail respectively.At the same time,the calculation formula of the equipment selection of the solar-air source heat pump compound heating system is given,as well as the equipment under the system design conditions is selected.Thirdly,according to the mathematical model of the main components of the solar-air source heat pump compound heating system,appropriate TRNSYS components were selected to set up TRNSYS model of the solar-air source heat pump combined heating system.Then the system was verified based on the measured data and the analysis of the operating characteristics of the solar-air source heat pump combined heating system was conducted.At the same time,comparisons were made among the air source heat pump heating system,the solar-electric heating system and the gas boiler heating system for analyze their performance on economy,energy saving,and environmental protection.Finally,based on the analysis of TRNSYS model and operating characteristics of the solar-air source heat pump compound heating system,as well as the evaluation indicators including solar energy guarantee rate and annual cost value,the orthogonal test method is used to optimize the analysis of different heating system terminal devices.It is concluded that the influencing factors are the collector area and the installation inclination angle of the solar collector and the volume of the storage tank.Besides,the finally optimal combination of the outlet and inlet water temperature of the terminal devices are 45°C and 60°C respectively.At the same time,by comparative analyzing the operating characteristics of solar-air source heat pump compound heating systems in residential buildings and that in office buildings,a solar-air source heat pump dual-tank heating system was proposed.At last,taking residential buildings as an example,the single-tank and dual-tank systems were analyzed and compared to provide some guidance for selecting appropriate solar heating systems for residential buildings and office buildings in cold plateau areas. |
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