The Research Of The United Operating System Of Solar Energy And Heating

It has been more than 300 years since solar energy was first used as a source of energy and power. However, the development of solar energy technique had been slow and the range of its application rather limited before the 1970s. Since the early 1970s, there has been a continuing global effort in the development of solar energy. The solar energy related research area has been constantly expanding with many new technologies as the result during the progress, such as vacuum heat collecting pipe, amorphous silicon solar battery, solar electricity generation and etc. Some products, such as solar water heater and solar battery, have been commercialized, but with limited application scale and less ideal economical benefit. The development of a utilization of solar energy usually takes rather long to mature, primarily because of the difficulty involved in the development process. The mass consumption of non-renewable energy resources results in worldwide environmental pollutions and damages to the ecological environment, which has become the threat to the life and well being of human beings. In 1992 the United Nations held the Conference on the International Environment and Development in Brazil, and a number of important documents, including "Declaration of Rio de Janeiro Environment and Development" have been produced by the conference, which have brought environment and development into a united frame, and set up a sustainable developing model. Countries all over the world strengthen the technologies in the development of green energy. As an inexhaustible clean energy source, solar energy is gaining more and more attentions worldwide. Concerted development of solar energy utilization and environment protection has led to a new stage of solar energy technologies. Our country has also established correspondingly the "Agenda of the 21st Century China", where solar energy source is considered as a key development area. Currently, the most popular application of solar energy is in hot water supply. This mainly includes home solar energy hot water heater, centralized solar energy hot water supply, solar energy boiling water supply system and etc.. Centralized solar energy hot water supply system needs supplementary heat input during operation. At present, oil burner or gas burner are the main supplementary heat supplies, though electricity is used in some cases as well. All the above supplementary heating systems have the drawbacks of large infrastructure investment, long idle period and etc.. In our country house-warming heat supply is needed in most regions during the winter backwater. If the returning water in the heating system is connected to the hot water storage tank in the solar energy system as the supplementary heat source, the two systems can be run in a combined fashion (as shown in Fig 1). The designed temperature for heating media is typically around 95~70℃. However, in practice, the temperature of the supply water varies with outdoor temperature, and thus the temperature of the return water varies accordingly. As to a common radiator of the heating system, which is directly connected to the outside network, during the regulation, the temperature of the return water in the pipe network can be calculated as following: (1)where th′(in unit of ℃) is the temperature of supply water or return water under any outdoor temperature; tg,th (in unit of ℃) are the temperatures of supply water and return water respectively under designed conditions; tn is the calculated indoor temperature during winter time; twj is the calculated outdoor air temperature; B is a radiator-related empirical parameter. Here Changchun city is used as an example. The calculated air temperature outside of the heating room is －23℃,and the calculated indoor air temperature is 18℃, and if the L-60 type of radiator is used,from tabulated data it can be found that B=0.28. Applying all the above parameters to Formula 1, the result shows that the return water temperature varies in the...