1、TWO DEMONSTRATIONS OF SOLAR HEATING AND AIR-CONDITIONING SYSTEM IN BUILDINGS IN CHINA Zhang Xinyu, Zheng Ruicheng, Feng Xiaomei , Zou Yu, He Tao ,Xuwei ,Zhang Jianghua,Li Zhong ChinaAcademy of Building ResearchNo.30, BeisanhuandongluBeijing 100013, China ABSTRACT Two demonstrations of solar air-con
2、ditioning and heating system in office building are introduced, one is solar heating system with seasonal storage, flat plate solar collector integrated into external wall, the solar fraction for space heating is 25%, another is solar-assisted air-conditioning system, evacuated tube solar collector
3、integrated with flat roof, the solar fraction for space heating is 20%, for air-conditioning is 50%. The auxiliary energy equipment is ground-source heat pump system. The control strategy for solar system and auxiliary energy system are also introduced. The project is financial by National Renewable
4、 Energy Fund of China. 1. INTRODUCTION The demonstration project located in Tong Zhou District of Beijing which near to BeijingCapitalInternationalAirport. The project invested by China Academy of Building Research, is the national demonstration project for energy efficiency in building on city leve
5、l. The total construction area of the project is 9460 3m , divided into two parts. One is 2835 3m , named South Part, another is 6625 3m , named North Part. The flat plate solar collectors integrated into external wall with seasonal storage are used in the South part. The evacuated solar collectors
6、on the flat roof are used in the North Part. The function of the building in project is office and testing laboratory. 2. BUILDING DESCRIPTION Solar energy system and ground-source energy system in this project supplied the energy for cooling and heating. The energy consumption of the building must
7、be a lower level. The basic information of building is following, 1. The average ratio of window to wall is 0.23； 2. The U-value of the external wall is 0.4 2mWK ； 3. The U-value of the roof is 0.275 2mWK ； 4. The U-value of the ground is 0.25 2mWK ； 5. The U-value of the windows is 2.0 2mWK 6. The
8、U-value of the door is 1.8 2mWK According to the simulation result with Trnsys, the energy efficiency in building of this project is 65% compared with pat public building in China and is higher Chinese standard. 3. SYSTEM DESIGN 3.1 North Part Solar heating system supply energy for space heating in
9、winter, the ground-source heat pump was used as the auxiliary heat source. In the season except winter, solar system store the heat in the concrete tank, the volume of which is 2003m .In winter, the ground-source heat pump and storage tank meet the cooling demand together. The terminal system for sp
10、ace heating is radiator and floor heating system. To make full use of the energy from solar system, Firstly, the higher temperature water from solar system pass the radiator, then go into floor heating system. The type of solar collector used in this part is flat plate solar collector, integrated wi
11、th external wall； it looks like curtain wall but solar collector. The total amount of solar collector is 140 3m ； the dimension of the collector is 1000 mm2000 mm. The aim of this part is to demonstrate the solar collector integrated type and seasonal heat storage. Fig. 1 is the appearance of flat p
12、late solar collector integrated with wall. The simulation result is that the solar fraction of this system is 25% for space heating. 3.2 South Part Solar heating system supply energy for space heating in winter and supply heat to drive the absorption to produce cooling water for air-conditioning in
13、summer. The ground-source heat pump was used as the auxiliary source. The type of solar collector used in this part is evacuated tube solar collector, integrated with flat roof. The total amount of solar collector is 228.48 ； the dimension of the collector is 1020 mm_2000 mm. The aim of this part is
14、 to demonstrate the solar assisted air-conditioning system. Fig. 2 is the appearance of evacuated tube solar collector on the roof In this system, two water tanks are used, one is for heat water storage, the volume of which is 10m3, and another is for cooling water storage, the volume of which is 15
15、m3.The output of the refrigeration is 105 kW. The simulation result is that the solar fraction of this system is 20% for space heating and 50% for cooling. In this part, the space heating building area is more than cooling. 4. SYSTEM CONTROL STRATEGY The system must take different control strategy i
16、n different season. The detail description of control strategy is following. 4.1 North Part In the heating season, solar heating system and ground-source heat pump system supply energy for space heating together. In summer, the ground-source heat pump system meet cooling demand, in other season the
17、solar collector system stored the heat in concrete tank for space heating in winter. 4.1.1 Heating Season The solar collector system is controlled by temperature difference between the highest temperature part of the solar collector and the lowest temperature in the concrete tank. When the temperatu
18、re difference bigger than 5oc , the pump of solar collector system started, till the temperature difference lower to 2oc , the pump stopped. The freeze protection of the system is drain back system, while the pump of solar collector system stopped, the water in solar collectors and pipes drained bac
19、k into concrete tank. When the water temperature in the concrete tank is more than 50oc , the solar heating system directly supply energy into building for space heating. When the temperature of the return water from the heating system is higher than 45ocand lower than 30oc , the heat pump heat the
20、water into required temperature to meet the heat demand. When return temperature is lower than 30oc , the solar collector system store the heat in the concrete tank. 4.1.2 Summer The ground-source heat pump supply cool water for air conditioning. The solar collector system is controlled with the sam
21、e in heating season. The solar collector system store the heat in the concrete tank for space heating in winter, when the temperature in the concrete tank is higher than 95oc , the pump of solar collector system stopped. 4.1.3 Other Season The solar collector system is controlled with the same in he
22、ating season. The solar collector system store the heat in the concrete tank for space heating in winter, when the temperature in the concrete tank is higher than 95oc , the pump of solar collector system stopped. 4.2 South Part In the heating season, solar heating system and ground-source heat pump
23、 system supply energy for space heating together. In summer, the solar heating system supply the heat to absorption refrigerator to cool water for air conditioning, when the radiation is not enough to produce higher temperature water, the ground-source heat pump system started. 4.2.1 Heating Season
24、The control strategy of solar system is the same with the North Part in heating season. The freeze protection of the system is anti-freeze circulation system； when the temperature in the top part of solar collector system is lower than 5oc , the pump of solar collector system started, when temperature increased to 10oc , the pump system stopped, part of water in solar collectors and pipes drained back into heat storage tank.
