The third phase of Lianyungang hotel brand solar water heater school project, 1921 to 1945, due to the application of the beam extraction of fossil fuels and the impact of the outbreak of the Second World War, at this stage of the research and development of solar energy at a low ebb, the number of participants and the research work research projects and research funding greatly reduced. The fourth stage of Lianyungang hotel brand water heater solar engineering school in 1946 -1965 years, 20 years after the end of World War II, the study of solar energy utilization started to recover. Lianyungang hotel brand solar water heater school project 199 - 1973 fifth stage of this phase of the World Solar Energy stalled, slow development, mainly due to the Department of solar energy technology is mature, in the growth stage; a huge investment, ineffective, difficult and compete with conventional energy sources; still not public, corporate and government attention and support. Lianyungang hotel brand water heater solar engineering school sixth stage of 1973-1980, the world has "oil crisis", the crisis prompted the objective to realize that it must change the energy structure, should accelerate the transition to a new energy mix. The seventh stage of 1981 -1991, development and utilization of solar energy boom 20 set off into the world 70 years after the beginning of the 1980s shortly Luo Chao, gradually into the trough, and many countries have significantly reduced solar research funding, which the United States is most prominent. Reasons for this situation, mainly in world oil prices to decline significantly, and solar products prices, uncompetitive; no major breakthrough solar energy technology to improve efficiency and cost reduction goals not achieved.