Solar heating system is solar energy as a heat source, providing buildings with winter heating and other heating systems throughout the year. This paper introduces the current situation of solar heating system at home and abroad and the application of the main equipment, points out some problems existing in the system design, and puts forward some measures for developing solar heating system.
With the development of national economy, the demand for energy is increasing day by day, and the situation of energy utilization is tight. However, the large use of conventional energy will certainly cause adverse effects on the environment. Solar energy as a renewable energy, inexhaustible, at the same time will not increase the environmental load, will become an important part of the future energy structure. China is one of the countries rich in solar energy resources, the annual radiation is about 3,300-8,300MJ /(m2.a), the annual sunshine hours of more than 2/3 of the country is more than 2000h, the annual land received solar radiation energy equivalent to 2.4 trillion tons of standard coal, has good conditions for solar energy utilization. In the building energy consumption, domestic hot water, heating energy consumption accounts for a considerable proportion, the use of solar energy to meet the requirements of domestic hot water, heating these low grade energy consumption has a huge energy saving benefits, therefore, solar heating technology more and more attention by people.
1. Principle of solar heating system
Solar heating system refers to the solar energy as the heat source of the heating system, the use of solar energy collector to convert solar energy into heat energy, the supply of building winter heating and other heating system throughout the year. Solar heating can be divided into active and passive two ways. Passive solar heating enables the building to fully collect, store and distribute solar radiant heat in winter through the reasonable arrangement of the building's orientation and surrounding environment, the clever treatment of internal space and external form, as well as the proper selection of building materials and structural structure. Active solar energy heating system is mainly composed of solar heating system, heat storage system, the end of the heating system, automatic control system and other auxiliary heating energy collection and heat exchange equipment, compared with passive solar heating, the heating condition is more stable, but at the same time, investment costs also increase, more complex system. With the development of economy and society, active solar heating has been applied on a large scale.
2. Overseas application status
In Europe and North America, the engineering application of solar heating (hot water, heating) system has a history of several decades. In the past, it was mainly used for small systems in single buildings. In the recent ten years, the engineering application of large-scale solar heating integrated system, including district heating, has developed rapidly. Germany is one of the first countries to apply solar heating technology. Solar heating technology has been widely promoted and applied in residential heating installation and renovation and supporting construction in Germany. Most countries in Europe actively encourage and support the use of solar energy, and implement subsidy policies for the installation of solar energy devices in families. The general subsidy is 20-50% of the cost of the system. Eighty percent of Israel's residential buildings are equipped with solar water heaters, and the government legislates that new residential buildings under the height of 27 meters must be installed with solar water heaters. Denmark's MARSTAL Solar Heating Project is the largest solar heating system in the world. The solar collectors are set in a large area of open space with an area of 18,300 m2 and connected to the community heat network. It was completed and put into operation in 1996 with an annual heat load of 28GWh/ year. At the same time, 2100m3 water tank, 4000m3 water capacity sand gravel layer and 10000m3 underground pool are used for heat storage.
3. Domestic application status
China's solar energy industry has developed rapidly, as of 2006, China's solar water heater annual production capacity reached 15 million square meters, in use of solar water heater total heat collection area of 100 million square meters, production and use of the world first. Although the solar water heater has been widely used in China, the application of solar heating engineering is still in the initial stage. All the demonstration buildings have been built, such as the office building of Tsinghua Sunshine Company in Beijing and the model building of Temple New Energy, etc., while the solar district heating engineering has not been applied in practice.
Among the solar heating construction projects in recent years, the most concentrated and representative ones are the solar heating projects of new dwellings in suburban areas and counties around Beijing. Due to dispersion of rural residential relatively low density, unfavorable use investment big, maintain high levels of central heating mode, the traditional way of coal-fired heating and the low efficiency, high cost, environmental pollution problems, in the rural areas to promote safety, environmental protection, low operating cost of solar heating system conform to the objective requirement of the new rural construction. Solar energy heating the heating area is greater than the solar energy hot water system, install location requires larger, for high-rise building or residential density larger city has the problem of insufficient installation construction condition, limits the application of the rural residential building volume rate is generally low, there is no obvious block, have the conditions for the building of solar heating project. The solar energy heating project of new residential buildings in Pinggu District of Beijing developed early, and there are many successful application experiences.
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