**Abstract:**
This paper presents a detailed analysis of the system configuration and design concept of the solar air-conditioning and heat pump system implemented in the first solar building demonstration project within the Tianpu Group Industrial Park, located in Daping District, Beijing. The system is primarily composed of solar heating and cooling technologies integrated with a heat pump, enabling it to fully meet the year-round requirements for air conditioning, heating, and domestic hot water in the new energy demonstration building. The environmental benefits of this system are compared with traditional heating methods, and key characteristics of solar air-conditioning systems are summarized.
**Keywords:** solar air-conditioning, heat pump, analysis
**0. Introduction**
With the rapid economic growth and rising living standards in China, the proportion of energy consumed by air conditioning and heating systems in buildings has significantly increased, becoming a major component of overall building energy consumption. This has led to growing energy and environmental pressures. Solar energy, as an abundant and clean renewable resource, offers a promising solution. Integrating solar energy into conventional heating and cooling systems plays a vital role in promoting energy efficiency and environmental protection.
The "Tempus New Energy Demonstration Building" project aims to explore the practical application of new energy in construction, supported by the Ministry of Science and Technology and the Chinese Academy of Sciences. A large-scale solar air-conditioning and heat pump system serves as the primary energy supply for the building. This paper provides a comprehensive description of the system and analyzes its operational data to extract valuable insights for future implementation and development.
**1. Details of the Solar Air-Conditioning / Heat Pump System**
**1.1 System Working Principle**
The new energy demonstration building, covering a total area of 8,000 square meters, was completed in August 2002 and officially put into operation by the end of 2003. Its main objective is to provide summer cooling and winter heating for the building. The system consists of a solar collector array, lithium bromide absorption chiller, heat pump unit, storage tank, and an automatic control system.
During heating and cooling periods, solar energy is prioritized as the energy source. In winter, the heat collected by the solar system is transferred to the storage tank via a plate heat exchanger for thermal storage. In summer, the absorption chiller uses the hot water from the solar collectors to produce chilled water, which is stored for cooling purposes.
The heat pump operates as a supplementary system. During winter, it activates when the storage tank temperature drops below 33°C or during power outages (from 10:00 PM to 7:00 AM). In summer, when solar cooling is insufficient to maintain the tank at 18°C, the heat pump cools the storage pool.
During transitional seasons, the system adjusts its operation mode. In spring, it runs in cooling storage mode, while in autumn, it switches to heating storage. The storage tank supplies both hot and cold water throughout the year, ensuring consistent comfort levels. Natural ventilation is used year-round to enhance indoor air quality.
**1.2 System Components**
The solar collector system has a total area of 812 m², consisting of heat pipe vacuum tubes and U-tube vacuum tubes. These were prefabricated into modular units before installation, ensuring seamless integration with the building's architecture. The heat pipe collectors were installed on the south-facing roof of the east wing, while the U-tube collectors were placed on the west building’s roof. Each row of collectors is arranged in parallel and tilted at approximately 38 degrees, matching the latitude of Beijing. This layout not only meets technical requirements but also enhances the building's aesthetic appeal.
To ensure continuous operation, a ground-source heat pump is used as an auxiliary system. The cooling water system utilizes a nearby water pool instead of a cooling tower, reducing costs and improving environmental compatibility. The automatic control system includes sensors, a programmable logic controller (PLC), and an industrial computer, offering both manual and automatic control modes. It supports remote monitoring, allowing operators to manage the system from outside the network.
A large underground energy storage tank with a capacity of 1,200 m³ is a key feature of the system. This ensures that solar energy can be effectively stored and utilized throughout the year, even during non-air-conditioning seasons. The tank is located underground, minimizing heat loss due to reduced temperature differences with the environment.
**2. Solar Hot Water System**
The building’s domestic hot water system is independent, using a solar thermal system to avoid complications with the air-conditioning system. Glass vacuum tube collectors are installed on the south façade, integrated directly into the building structure. These modules eliminate the need for traditional frames and support structures, providing both thermal insulation and aesthetic value. A total of 48 modules cover 206 m² of solar collection area.
**3. Winter Heating System Analysis**
**3.1 Winter Heating Test Data and Analysis**
Data from January 1, 2004, to March 15, 2004, was analyzed. During this period, the solar collector system operated for 443.5 hours, storing 32,761.9 kWh of energy in the underground tank. The heat pump ran for 675 hours, storing 299,025 kWh. Based on the heat pump’s working principle, it extracted 227,475 kWh of waste heat from workshop cooling water. The system used 260,237.9 kWh of stored energy and waste heat, with a new energy ratio of 0.784.
The total heat storage from January to March 2004 was 331,787.9 kWh, with a power consumption of 93,644.5 kWh. The heat pump operated almost at full load, achieving high efficiency and energy savings. Despite fluctuations in the temperature of the water entering the condenser, the heat pump maintained a high coefficient of performance (EER). Indoor temperatures remained stable between 20°C and 22°C, meeting the design standards for comfort and heating.
**3.2 Environmental Benefits Analysis**
Comparing the solar air-conditioning/heat pump system with coal, oil, and natural gas boilers, the results show significant environmental advantages. Coal combustion produces the highest COâ‚‚ emissions, followed by diesel and natural gas. In contrast, the solar system emits zero pollutants. While other systems require fossil fuels and generate greenhouse gases, the solar system relies solely on electricity, making it a cleaner and more sustainable option.
**4. Conclusion**
The solar air-conditioning and heat pump system demonstrates several key advantages:
1. Modular solar collectors integrate seamlessly with the building’s design.
2. A ground-source heat pump enhances reliability and simplifies the system.
3. A large underground energy storage tank enables year-round operation and reduces losses.
4. High new energy utilization and significant energy-saving potential.
During the heating season, over 80% of the heat comes from solar energy and waste heat, with an energy consumption ratio of 3.54. Environmentally, the system offers clear benefits, emitting far fewer pollutants than traditional systems. Overall, the solar heating and air-conditioning system represents a promising solution for energy efficiency and environmental sustainability. As technology continues to advance, it is expected to become a standard option in HVAC design.
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