Development status and prospect analysis of tower solar thermal power generation technology in China

1 Technical characteristics of tower solar thermal

Power generation principle: The heliostat is used to focus the sunlight on the heat absorber located at the top of the heat collection tower, heat the heat transfer medium in the heat absorber to generate heat energy, and then generate high temperature steam through the heat exchange system to drive the turbine to generate power. The composition of tower solar energy mainly includes: heliostat, heat absorber, heat exchanger, high and low temperature storage tank, heat collection tower, turbine generator set and so on. The heat transfer working medium can be air, water/steam or molten salt.

The energy concentration process of the tower technology is completed by reflecting the light at one time, the method is simple and effective, and the concentration ratio is high, and it is easy to reach a relatively high working temperature. The more the number of heliostat in the mirror field, the greater the concentration ratio, the higher the heat collection temperature of the heat absorber, and the higher the photothermal conversion efficiency.

2 Development status of tower solar thermal power generation at home and abroad

2.1 Foreign Countries

In 1950, the former Soviet Union designed the world's first small tower solar thermal power generation test power station, and conducted basic exploration and research on solar thermal power generation technology. During the 10 years from 1981 to 1991, due to the impact of the oil crisis, alternative energy technology rose in the world, and other industrial developed countries also invested in the construction of a number of experimental power stations.

According to incomplete statistics, at that time, more than 20 megawatt-level solar thermal power test stations of various forms with an installed capacity of more than 500kW were built around the world, of which tower power stations were the main form with a maximum power generation of 80MW. Because the investment per unit capacity is too large, the construction of solar thermal power stations is gradually cold.

In the past two years, solar thermal power generation has once again become a hot investment spot in the field of international renewable energy. Relevant data show that the global trend of new clean energy investment to large-scale solar thermal power generation is becoming increasingly obvious, the scale of project construction is also getting larger and larger, more and more businesses will focus on tower solar thermal power generation.

At present, the international Tower solar thermal power stations that have been put into commercial operation are PS10, PS20 and Gemasolar in Spain, and SierraSun Tower power station, Ivanpah power station and Crescent Sand Dune power station in the United States.

Gemasolar is the world's first 24-hour continuous power generation tower solar thermal power station, officially put into operation in October 2011, installed capacity of 19.9 megawatts, annual power generation of 110 million degrees, annual operating hours of 6450 hours. The concentrator system of Gemasolar power station consists of more than 2,600 concentrator panels spread over 185 hectares of open space. The light energy received by the individual mirror plates is accumulated in a central receiver, which heats the molten salt tank and forms high-temperature pressurized vapors through heat conduction to drive a turbine to generate electricity.

Ivanpah is currently the largest tower power station, officially connected to the grid on February 13, 2014, with a total installed capacity of 392MW, consisting of three tower power stations with installed capacity of 133MW, 133MW and 126MW respectively, with an annual generating capacity of 1079GWh.

Ivanpah Power Station has a maximum installed capacity of 133MW per tower, which is the first time to realize the development of a 100-MW tower power station, and verifies the feasibility of large-scale development of tower power stations from the practical level. Ivanpah is a water-working medium photothermal power station without heat storage system. Due to local water shortage, an air-cooling system is adopted, and the water consumption per KWH is 0.11L, which greatly saves water consumption compared with the water-cooling system.

The New Moon Dune Power Station in the United States is the world's first 100MW molten salt tower power station. It was connected to the grid on February 22, 2016, with an installed capacity of 110MW and a 10-hour heat storage system. The designed annual power generation capacity is 500,000 MWh. As the first 100 MW commercial large-scale tower molten salt power plant, the current power generation situation of Crescent Dune has not reached the expected design.

2.2 Domestic

Compared with foreign countries, China's solar thermal power generation is still in the initial stage of industrialization, and the mastery and research of its technology lag behind. In order to explore the research and development of tower solar thermal power generation system, the first 70kW tower experimental demonstration power station in China began construction in 2004 with the support of Nanjing Science and Technology Bureau. The heliostat field of the power station consists of 32 sets of 20m2 heliostat, the heat collection tower is 33m high, and the heat absorber is provided by Israel with pressure cavity receiver.