The development characteristics of solar water heating
(1) Based on China, integrate production, learning, and research into independent development to make breakthroughs in key technologies. A notable feature of China’s solar hot water technology is its independent intellectual property rights in key technologies. In order to improve the useful heat of solar energy of solar heat collection equipment, a vacuum solar heat collection tube is invented that adopts vacuum interlayer and applies solar selective absorption coating to minimize convection and radiation heat loss. China has mastered its core technology-the preparation process of solar selective absorption coatings, and has the invention patent “Multilayer Aluminum-Nitrogen/Aluminum (A-N/A1) Selective Absorption Coating” applied by Tsinghua University. It is still recognized as the most cost-effective selective absorption coating in the world. The invention patent was published in 2000, which greatly promoted the development of China’s solar thermal utilization industry.
(2) Do not rely on government subsidies and follow the path of market-oriented industrial development. Incentive policies for the solar water heater industry in various countries around the world can be divided into three categories: legislation, fiscal incentive policies and indirect market policies. The fiscal incentive policies include subsidies, tax incentives, and low-interest loans. At present, the general subsidy adopted by most European countries is 20%-50% of the system cost, and the highest subsidy in Germany can reach 60% of the system cost; countries such as Brazil, Portugal, the Netherlands, and Austria have adopted preferential tax policies, and other countries provide users with low-interest loans. It can be said that the development of the solar water heater industry in most countries in the world has a high degree of dependence on the government’s financial incentive policies, which is a huge contrast to the situation in China. The growth and industrialization of Chinese solar thermal utilization enterprises have been developed entirely through market-oriented operations, and government support is mainly placed on legislation (Renewable Energy Law) and indirect market policies (funding R&D projects, supporting national standards and quality certification, publicity and promotion activities, etc.).
(3) Relying on China’s domestic market, the total output and installation are huge, the regional imbalance, and the per capita usage is low. It is different from many export-oriented manufacturing industries in China, and it is also different from China’s photovoltaic industry, which also uses solar energy, China’s solar thermal utilization industry has always been developed by relying on a huge domestic market, and product exports have only gradually increased in recent years. China is the world’s largest solar water heater market and producer, and the total output and usage of solar water heaters ranks first in the world. However, due to China’s huge population occupying the first place in the world, it consumes about 96m² per thousand people, ranking only 10th in the world. Even if the total output of 300 million m² is reached by 2020, the consumption per 1,000 people will only be 200 m². The market share used in various parts of China is not balanced, especially in the western regions where the economic development is relatively low and the solar energy resources are relatively low.
(4) Basically establish standards, testing and certification systems for product quality supervision. The research and formulation of China’s national standards for solar water heating systems and engineering originated in 1982. At present, 16 national standards for solar hot water system products, 4 industry standards, and 1 national engineering construction standard have been promulgated and implemented, which basically cover all products and accessories series. The two national solar water heater product quality supervision and inspection centers in Beijing and Wuhan have carried out quality supervision and inspection work for five years, including products under national supervision and random inspection, which has played a very good role in promoting the improvement of the quality and performance of domestic products. In addition, it has been in line with international standards, actively carried out product quality certification, and basically established product quality supervision standards, testing and certification systems that conform to China’s national conditions.
(5) The all-glass vacuum tube compact solar water heater has the highest market share. Developed countries account for more than 90% of the market share of flat-plate collector-separated solar water heating systems, which are very suitable for integration with buildings in terms of product safety, reliability, durability or system form. The product variety with the highest market share in China is the all-glass vacuum tube compact solar water heater. The current mainstream product is still the compact unpressurized solar water heater, which is not suitable for integration with buildings. This is also the difficulty for China to promote the integration of solar water heating systems with buildings.
(6) The number of solar hot water projects integrated with buildings is small, and the technical level is uneven. The concept that solar water heaters (systems) must be integrated with buildings has reached a consensus in the academic, industrial, and construction industries for solar energy utilization, and has received strong support from government agencies at all levels such as the National Development and Reform Commission, the Ministry of Construction, and the Provincial and Municipal Construction Departments. However, in the field of solar water heating technology and engineering application combined with buildings, China’s overall level and application scale still lag far behind that of developed countries. The development of different regions is not balanced; there are some misunderstandings; most architectural design institutes and real estate developers pay less attention to building integrated solar water heating systems; some solar water heater companies’ understanding of building integration stays on the concept and has not invested substantive efforts; all aspects of product performance, applicability of integration with buildings, and system design need to be improved.