Country comparison of solar water heater technology application research and policies Part 2
6. Technical research
Some European countries are not rich in solar energy resources, but due to the lack of conventional energy and strong environmental awareness, many countries are committed to the optimization of solar water heating systems. Through software simulation and experimental measurement, analyze the operation mode and parameter setting of each part of the system, such as the setting of water tank volume, water temperature, and water load, and compare different situations to optimize the efficiency of the solar water heating system. Due to the small number of high-rise residential buildings in other countries, most solar water heating systems are used in multi-storey residential buildings and villas, and research on the integrated design of high-rise residential buildings and solar water heating systems is less involved.
In China, solar collectors have always been the focus of solar water heating system research. The main research content is to improve the efficiency of solar thermal conversion. The core technology is to develop materials with high absorption and low radiation, that is, to absorb as much solar energy as possible while radiating as little thermal energy into the air as possible to preserve thermal energy. Solar water heating systems in China are mainly used in low-rise and multi-story buildings. There are few related theoretical studies, and only research teams such as Hong Kong and Shanghai have conducted certain research on this aspect.
7. Research on the integrated design of solar collectors and building appearance
Architects in many countries have realized that when solar collectors are combined with buildings, they should have multiple functions such as maintenance, decoration, shading, and heat preservation, in addition to the heat collection function. It should be part of the building and should not be separated separately. “Integration” is not “invisibility”, it is better understood as “compatibility”. So far, there have been many theoretical studies and successful application cases for the way of integrating collectors and buildings. Solar energy manufacturers have also produced collector products of different colors, shapes, and materials to meet the needs of architects.
While conducting research and implementing projects, many countries attach great importance to the needs of architects. Stadler and others surveyed 52 architects:
46% of architects want the collector to meet the building facade modulus, 28% of architects want the collector to have a standard size; 85% of architects want a variety of options for the color of the collector. Maria Cristina conducted a survey on a large number of architects through the Internet: The architect believes that the good combination of collectors and building appearance depends on the size and location of the collector, shape and size, connecting components, material surface texture and color.
At present, in-line water heaters are still the mainstay in China, and the collector and the water storage tank cannot be separated. Residents installed it by themselves, destroying the beauty of the building’s top surface and facade. Adding solar collectors to existing buildings may also damage the roof waterproof layer and cause roof leakage; or improper installation may cause safety hazards. At present, China is gradually encouraging the integrated design of solar water heating systems and buildings, requiring the organic combination of collectors and building appearances to become a part of the building. In recent years, some solar water heater manufacturers have successively developed solar collector products that are more compatible with buildings, invested in new demonstration communities, explored the combination of solar collectors and building appearance, and achieved good results. But in general, due to the lack of types of collectors, the lack of adaptability to the building, and the lack of understanding of related technologies by architects, there are few practical projects that can realize the organic combination of solar water heating system and building appearance, and the technology is relatively rough, and further research and practice are needed.
8. Encouragement policy
At present, more than 40 countries and regions around the world have formulated different policies to encourage the development of the solar energy industry, and encourage residents and developers to use solar water heating systems through tax preferential policies and purchase subsidies. The United States initiated the “Millions of Solar Roof Plan” to provide tax relief and subsidies to those who use solar water heating systems. The LEED green building evaluation standard also incorporates the application of solar energy into the green building evaluation system, making it an important scoring point. Germany promulgated a new renewable energy law in 1999, and the installation of solar water heating systems can receive a high subsidy of 60%. Israel has adopted a mandatory promotion policy, and the penetration rate of solar water heaters exceeds 90%.
The Chinese government passed the Renewable Energy Law in 2006. In April 2007, the National Development and Reform Commission and the Ministry of Construction issued the “Notice on Accelerating the Promotion and Application of Solar Hot Water System”. The Ministry of Science and Technology, the Ministry of Finance, the Ministry of Construction and other relevant ministries and commissions and many local governments have set up some solar water heater development and promotion projects, and formulated relevant preferential policies. Shandong, Hainan, Fujian, Zhejiang, Jinan and other provinces and cities have successively promulgated compulsory measures and management measures for the application of solar water heating systems in buildings. The government’s emphasis on energy conservation and emission reduction has never been increased, which has accelerated the promotion of solar water heaters in China.