As you fly over Jiuquan in Gansu Province or set off west from the city of Dunhuang, you will be greeted by a striking cyberpunk-like image: on the vast Gobi Desert, a huge circular matrix shines brightly, its scale and form are regular, as if it were the work of extraterrestrial intelligent beings. However, this is not an alien product, but the crystallization of human technology and wisdom - molten salt tower solar thermal power station.
Located about 20 kilometers west of the city of Dunhuang in Gansu Province, the magnificent power station was jointly built by the Dunhuang municipal government and Beijing Shouhang Energy Saving Technology Co., Ltd. It takes full advantage of the abundant solar energy in the area to heat the molten salt by reflecting and focusing the sunlight, which in turn produces steam to drive the turbine generator to generate electricity.
This power station is not only the first grid-connected power station in the first batch of CSP demonstration projects in mainland China, but also stands out for its many "bests". It is the molten salt tower solar thermal power station with the largest installed capacity in mainland China and even in Asia, with the world's largest heliostat field of concentrating light, the heat absorption tower towering into the sky, and the heat storage tank is also unprecedentedly huge. What's even more remarkable is that it can continuously generate electricity 24 hours a day, and steadily output 100 megawatts of clean energy.
At this time, many people will ask what is molten salt tower CSP power station, in fact, before introducing molten salt tower CSP power station, we must know about solar thermal power station, that is, solar thermal power generation. In our middle school physics class, we have done experiments with concave lenses to focus sunlight on the focal point through the concave lens in a sunny place, and the focus will gather energy, and the temperature can make the paper burn. The basic principle of solar thermal photovoltaics is similar to this, but the process is certainly more complex.
1. What is solar thermal power generation?
Solar thermal power is a technology that uses solar radiation energy to convert into electrical energy. Unlike solar photovoltaics, which directly convert light energy into electrical energy, solar thermal power generation is achieved through an intermediate thermal energy conversion process. It first concentrates solar radiation energy into a small area through a concentrating system, heats the working medium (such as water or other working fluids), and then delivers this heat energy to a heat engine or turbine, which in turn drives a generator to produce electricity.
2. Why should solar thermal power generation technology be developed?
Solar thermal power generation has its own unique advantages compared to other clean power generation methods.
(1) Not limited by time, space, climate and season:
Solar thermal power is able to continue generating electricity during periods of time when there is not enough sunlight through a heat storage system, including at night, on cloudy days, on rainy days, etc. This capability allows solar thermal power plants to provide baseload power like traditional thermal or hydroelectric power plants, helping to stabilize the grid. In contrast, solar PV power generation will be much less efficient when there is not enough sunlight.
(2) Friendly to the power grid and conducive to frequency modulation operation:
Since the output of solar thermal power generation is relatively continuous and stable, it can better match with the grid and reduce the impact on the grid. In addition, the existence of heat storage systems allows solar thermal power plants to quickly respond to the frequency modulation needs of the grid, that is, to increase the amount of electricity generated when demand increases and to decrease when demand decreases. This flexibility makes solar thermal power play a very important role in the power system.
(3) High thermoelectric conversion efficiency:
Solar thermal power generation technology concentrates solar radiation energy through a concentrating system, heats the working medium to a high temperature, and then drives a turbine or heat engine to generate electricity. This high-temperature operating state results in a relatively high thermoelectric conversion efficiency. And with the continuous advancement of technology, the solar thermal power plant of the future is expected to achieve higher conversion efficiency.
(4) Utilization of excess heat energy:
The excess heat energy generated by the solar thermal power plant during the power generation process can be used for other purposes, such as heating, desalination, etc. This versatility allows solar thermal power plants to meet electricity demand while also providing other forms of energy services to the local area, further improving energy efficiency.
Schematic diagram of a solar thermal power generation system
3. What are the types of solar thermal power generation?
According to the different focusing methods and working mediums, CSP is mainly divided into four types: tower, trough, disc and linear Fresnel. Tower CSP is like a giant solar "chimney" that concentrates sunlight on the receiver at the top of the tower through mirror reflection, trough is like rows of huge "sunbeds" that reflect sunlight onto collector tubes through parabolic mirrors, and dish is more like a solar "satellite antenna", while linear Fresnel uses a series of parallel plane mirrors to reflect sunlight onto the collector tubes.
1. Trough solar thermal power generation system:
A parabolic parabolic parabolic parabolic parabolic parabolic parabolic This system realizes the efficient conversion of solar energy to electricity through concentrating collectors arranged in series and parallel.
Trough thermal power generation
2. Tower Solar Thermal Power System:
The tower solar thermal power system uses a heliostat on a large area of the site to reflect and concentrate sunlight to a receiver at the top of the tower, converting the absorbed light energy into heat energy and then transferring it to the working fluid. After heat storage, the thermal energy drives the thermal power machine to expand and do work, and finally drives the generator to output electrical energy. This system realizes the efficient conversion and utilization of solar energy.
Dunhuang 100 MW molten salt tower solar thermal power station
3. Dish solar thermal power generation system:
The dish solar thermal power generation system is a solar power generation system that uses parabolic mirrors to concentrate light and collect heat. It mainly consists of a disc-shaped parabolic mirror, a receiver, a Stirling engine, and a generator. When sunlight hits the parabolic mirror, the light is focused to the focal point on the receiver, heating the working medium in the receiver to a high temperature, which in turn drives the Stirling engine to generate electricity. Such systems can be operated independently, as a small power source in remote areas without electricity, or as a small solar thermal power station by connecting multiple units in parallel. Dish solar thermal power generation systems have the advantages of high efficiency, modularity and independent operation, so they have a wide range of application prospects in some specific application scenarios.
Dish solar thermal power
4. Linear Fresnel solar thermal power generation system:
The linear Fresnel solar thermal power system uses multiple planar mirrors near the ground to reflect sunlight to the secondary concentrator above, and then concentrate it to the heat absorption tube to generate high-temperature steam, which directly drives the turbine generator to generate electricity. The system is simple and is a way to use solar energy efficiently.
Linear Fresnel solar thermal power generation
Overall: Solar thermal power generation has some unique advantages over solar photovoltaic power generation. For example, it can achieve continuous power supply through a heat storage system, which is not affected by day and night and weather changes, and at the same time, it is relatively efficient due to the use of traditional thermal cycle power generation technology. However, there are also some challenges associated with solar thermal power generation, such as higher costs, geographical limitations, etc. However, with the continuous advancement of technology and the reduction of costs, solar thermal power generation is expected to play an increasingly important role in the future energy system.