Application of Solar Air Conditioning / Heat Pump System in Solar Building Demonstration Project

Abstract: This paper describes in detail the system configuration and design idea of ​​solar air-conditioning / heat pump in the first solar building demonstration project in Tianpu Group Industrial Park, Daping District, Beijing. The system mainly consists of solar heating and cooling and heat pump, which can be completely Meet the new energy demonstration building year-round air-conditioning, heating and domestic hot water needs. The paper compares the environmental benefits of the system with several other traditional heating methods and summarizes the characteristics of solar air conditioners. Keywords: solar air-conditioning heat pump analysis 0 Preface With the economic development and improvement of people's living standards, the proportion of air conditioning and heating energy consumption in China's building energy consumption has been greatly increased, and gradually developed into a major part of building energy consumption, bringing greater energy and environmental pressure. Solar energy is an inexhaustible source of clean energy. Using solar energy to supplement conventional energy-driven air-conditioning and heating systems is of great significance for energy conservation and environmental protection. The project of "Tempus New Energy Demonstration Building" is to explore the experience of comprehensive utilization of new energy in construction, which is supported by the Ministry of Science and Technology and the Chinese Academy of Sciences. Large solar air conditioning / heat pump system is the main energy supply system of the building. This article describes the solar air-conditioning / heat pump system in detail, and analyzes some of the data in the operation of the system in order to summarize the experience and lay the foundation for the promotion and application. 1 solar air conditioning / heat pump system details 1.1 system working principle The new energy demonstration building with a total construction area of ​​8000 m 2 . The main building of the building was basically completed in August 2002 and passed the inspection by the end of 2003. It has now been completed and put into operation. The goal of this system is to meet the requirements of summer air conditioning and winter heating in the new energy demonstration building in Tianpu. The system is mainly composed of solar collector array, lithium bromide refrigerator, heat pump unit, storage tank and automatic control system. The system works as shown in Figure 1. During the period of building heating and air-conditioning, solar energy is used as energy storage pool priority. In winter, the heat collected by the heat collecting system is exchanged to the storage tank through the plate heat exchanger to achieve the purpose of heat storage. In summer, the absorption chiller takes the hot water collected by the solar heat collecting system as a heat source to make chilled water as an energy storage tank Cold source. Heat pump as a solar air conditioning system. In winter, the heat pump is started to heat the storage pool when the pool temperature is below 33 ° C or in the power down period (22:00 pm - 7:00 next day). In summer, when solar cooling can not maintain the pool At a temperature of 18 ° C, the heat pump cools the reservoir and keeps the temperature of the reservoir. The transitional season system only starts part of the solar cooling, heating, and in different transition seasons choose different modes of operation. In spring, the system works in cool storage mode. The absorption chiller provides chilled water to the storage tank to reduce the temperature of the storage tank to prepare for cooling in summer. In autumn, the system converts to heat storage mode. The solar collector system supplies energy to the storage tank Pool heating, raising the temperature of the pool to prepare for winter heating. Both winter and summer, hot water and chilled water in the air-conditioning water system are supplied by the storage pool. In winter, when the room temperature is below 18 ° C, the building pump is turned on and the pool is heated to the building. The pump is turned off when the room temperature is above 20 ° C. In summer, the building pump is turned on when the room temperature is above 27 ° C , The pool to the building cooling, when the indoor temperature is below 23 ° C, for the pump off. The building is naturally ventilated throughout the year. 1.2 system details The total collecting area of ​​the heat collecting system is 812m 2 , and the collector is composed of a heat pipe type vacuum tube and a U-shaped tube type vacuum tube. Taking into account the problem of integration with the building, the collector was prefabricated into different modules before installation. The U-tube collector and the heat pipe collector were prefabricated by φ 58 × 1800 vacuum tubes to 4000 × 1200 mm 2 and 2000 × 2400 mm 2 mounting module. After careful design by the construction department and designers, the heat pipe type heat collector is arranged on the south slope of the east floor of the new energy demonstration building. The heat pipe collector is installed on the south slope roof U and engine room of the west building of the New Energy Model Building (Shown in Figure 2), each row of collectors connected in parallel, the installation of the same inclination with Beijing, about 38 degrees. This arrangement of the collector not only to meet the installation requirements of the collector, but also to ensure that the building is handsome in appearance, fully reflects the integration of solar energy and architectural features. In summer, the heat collector combined with the building also has the heat insulation effect, meanwhile, it achieves the purpose of saving energy. As the solar energy itself is low in energy density, subject to time, weather and other conditions, to make the air conditioning system to work around the clock, auxiliary system is essential. The system uses a ground source heat pump unit as a secondary system. Cooling water system abandon the conventionally used cooling tower, the use of a water pool not far from the engine room as a source of cooling water, cooling water circulating between the pool and the unit. This not only saves the cooling tower costs, but also with the building and the environment. Automatic control system consists of sensors, programmable logic controller (PLC) and industrial control computer 3 parts, divided into automatic and manual control mode. In order to meet the characteristics of each season system operation, automatic control mode is divided into cooling, storage, heating, heat storage, neutral five operating conditions. And the control system supports remote monitoring, you can monitor the system from outside the network operation and change operating instructions, the network and other high-tech into the control system. In order to maximize the use of solar energy, according to the characteristics of building air conditioning, the system set up the energy storage pool. The system configuration storage pools much larger than the volume of the tank is usually a solar energy system, there is 1200m 3, which are a major feature of the system design. The large capacity of the energy storage pool ensures that the energy stored in the water pool can fully meet the needs of the building. Meanwhile, in the transitional season in which the building does not need air conditioning, the water pool can be stored in advance and the heat storage can be prepared for the air conditioning season. As the energy storage pool of solar energy savings transfer, collector work throughout the year, utilization has greatly increased. Storage pool set in the ground, heat transfer temperature difference is much smaller than the temperature difference with the environment, help to reduce the loss of energy storage. 2 solar hot water system Building living hot water system uses an independent solar hot water system, so you can avoid switching between domestic hot water system and air conditioning water system, reducing system complexity. Solar thermal water heating system storage glass vacuum tube collector module installed in the south elevation of the building, the module in the installation process to cancel the conventional frame, water tank, integrated with the building, at the same time played the building south elevation Thermal insulation effect. A total of 48 heat collecting modules are installed on the south side of the building with a total lighting area of ​​206 m 2 . 3 winter heating system analysis 3.1 winter heating test data and analysis Collected the operation data of 2004.1.1 ~ 2004.3.15, the following part of the data for analysis. 2004.1.1 ~ 2004.3.15 Solar collector system work 443.5 hours, storage energy to the underground storage tank 32761.9kWh, heat pump work 675h, heat storage 299025 kWh. According to the working principle of the heat pump, it can be calculated that the heat pump extracts energy from the waste heat (workshop cooling water) of 227475 kWh, the system uses 260237.9 heat storage and waste heat, and the ratio of new energy sources in heating is 0.784. Calculated from Table 1, the total heat storage of the system from January 2004 to March 2004 is 331787.9 kWh and the power consumption is 93644.5 kWh. The output of the heat pump is an underground storage tank, so the heat pump does not need to consider the changing conditions, and the heat pumps are almost always at full load , The maximum performance of the heat pump has been realized, which is an energy saving in itself compared to the operation of most air conditioning units at a lower load rate today. Although the temperature of the water entering the heat pump condenser has changed, this does not have a significant impact on the energy efficiency of the heat pump. The EER of the heat pump can be maintained at a high level. Figure 3 shows the indoor and outdoor temperature comparison of the coldest coldest day from January 2004 to March 15, 2004. From the figure we can see that when the ambient temperature is low and there is fluctuation, the indoor temperature is between 20 ° C and 22 ° C Room changes, indoor temperature and temperature changes in line with design standards, indicating that the system can fully meet the requirements of building heating temperature and comfort. 3.2 Environmental Benefits Analysis Comparison of several common typical heat sources used in air conditioners, namely, coal-fired boiler system, oil-fired boiler system, natural gas boiler system and solar air-conditioning / heat pump system, respectively. Coal-fired boilers use ordinary coal (fuel heat value: 20.9MJ / Kg), oil-fired boilers to 0 # diesel fuel (fuel calorific value: 42MJ / kg). The efficiency of coal-fired boilers and oil-fired boilers were taken as 0.58 and 0.88, respectively. Natural gas boiler efficiency of 0.88, in view of the natural gas heat value has a certain range of fluctuations, this article is worth 49.5MJ / kg. The amount of CO2 generated by the combustion of heating fuel per unit area is shown in Figure 4. From Figure 4, we can see that coal combustion releases the most CO2, followed by diesel and natural gas, and the solar system emits zero pollution. The solar air-conditioning heat pump system only uses electric energy for its operation, while other schemes need to generate greenhouse gases such as CO2 besides the electric energy. In particular, nitrogen and sulfide pollution generated by coal-fired boilers should not be neglected. Can be seen with solar air-conditioning heat pump to avoid fuel combustion on the air pollution and the resulting greenhouse effect, its environmental advantages are unmatched by several other programs. 4 Conclusion The system mainly has the following characteristics: (1) The pre-heating collector is installed into the module to achieve a good combination with the building; (2) The use of ground source heat pump as an auxiliary system for solar air-conditioners simplifies the solar air-conditioning system and adds The reliability of the solar air-conditioning system; (3) The system sets up a large-capacity underground energy storage pool to make the solar energy system work all year round and reduce the energy storage loss; (4) The new energy utilization rate is high, with strong energy saving Superiority. In the heating season, the heat storage capacity using solar energy and waste heat is close to 80% of the total heat storage capacity, and the energy consumption ratio reaches 3.54 (5). The environmental benefits are obvious. Compared with the use of conventional energy heating system, with less pollution and other environmental advantages of emissions. In summary, the solar heating / air-conditioning system has advantages and potential in terms of energy saving and environmental safety. With the further maturity of various technologies, the solar heating / air-conditioning system will gradually be put into practical use and commercialization and become the general design of HVAC Another option for people.