Photovoltaic power generation is that when sunlight shines on a solar cell, the cell absorbs light energy, and charges of different signs accumulate at both ends of the cell, that is, a voltage is generated, and the electrodes are drawn and connected to the load; current is generated.
 
Therefore, except that the source is the sun, photovoltaic power generation and solar thermal power generation are completely different things. However, the two are often compared. 
 
The main advantages of photovoltaic power generation
(1) It is not affected by the region. In theory, as long as there is sunlight, it can be installed.
(2) There is no consumption of fossil energy, no pollution and noise.
(3) The power generation process is simple, directly converting light energy into electrical energy without intermediate links.
(4) It occupies less land. If it is installed on the roof, the land occupation is zero.
(5) The structure is simple. It is easy to build, and the maintenance cost is low.
 
The disadvantages of photovoltaic power generation
(1) There is no power output on cloudy days and at night.
(2) Because there is no intermediate link, the cost of electric energy storage is high, which limits the scale of access to the grid.
(3) At present, compared with thermal power generation, the efficiency of photovoltaic power generation is still relatively low, and the photovoltaic conversion efficiency is less than 20%.
 
Advantages of solar thermal power generation
(1) The cost of energy storage is greatly reduced, and the maturity of thermal energy storage technology is much better than that of electric energy storage.
(2) The consequent dispatchability of power generation is very high, which is very similar to thermal power plants, and can adjust the power generation according to the load at any time, outputting power smoothly.
(3) Because the output can be smoothed, it has the possibility of being used as a power grid spinning backup and peak-shaving and valley-filling output, which can be equivalent to a fast thermal power unit plus a pumped storage unit.
 
Disadvantages of solar thermal power generation
(1) Regionality is a flaw. Solar thermal power generation requires high working temperatures and direct sunlight, so it is generally built in the desert.
(2) The cost is high. The cost of solar thermal power generation is more than double the cost of conventional energy power generation. The investment cost of the power station is 4 times that of photovoltaics. The low retention density of solar energy requires large-area optical reflectors and expensive receivers to directly convert solar energy into thermal energy. The investment cost of this process accounts for about half of the entire power plant investment, which leads to the high cost of solar thermal power generation.
(3) The technology is still immature, which can be seen from the degree of commercialization.
 
Although solar thermal power generation is good, there is still a long way to go to put it into practical use. Since the birth of solar thermal power generation technology in the 1950s, it has gone through multiple stages of development. As of the end of December 2015, nearly 5GW of solar thermal power generation power stations have been built and put into operation around the world.
 
Among them, Spain has a total installed capacity of 2300MW in Thermal Power Station, accounting for nearly half of the global total installed capacity, ranking first in the world, and the United States has a total installed capacity of 1777MW, ranking second in the world. The two countries account for 88% of installed capacity in the world. In addition to these two major solar thermal power generation countries, India, South Africa, the United Arab Emirates, Algeria, Morocco and other countries are also vigorously developing solar thermal power generation. China is the eighth country that has mastered large-scale solar thermal power generation in the world.
 
Although the principle of solar thermal power generation is simple, its energy conversion link is much more complicated than that of photovoltaic power generation. It involves the cross-integration of multiple disciplines such as optics, thermal science, electricity, materials science, and thermal energy engineering. For different technical routes, there are also obstacles and paths for improving efficiency. However, it can be said that promotion and application still have a long way to go. However, we should see great prospects for its development.
 
Combined power generation with photovoltaic power plants and thermal power plants to form a complementary effect. Balancing the power production and transmission between solar thermal and photovoltaic in the same power generation area can eliminate the intermittency problem of photovoltaic. The combination of these two technologies can effectively reduce the power generation cost of the overall system as a whole. Establish a distributed power generation system to solve the problem of power supply in remote mountainous areas. The disc system is the most suitable, but because its power generation is not yet mature, the trough power generation system is mostly used at present.
 
Some professionals pointed out that domestic enterprises have entered the solar thermal power generation market, and the overall industrial chain has been initially formed: the five major power companies have successively developed solar thermal power generation. Domestic enterprises have grown rapidly in the production of upstream and downstream components in the photothermal industry chain, such as the capacity and production capacity of heliostats for large-scale tower-type power stations, megawatt-level solar tower-type thermal power stations have been trial run. There are vacuum tubes of 300°C, and the goal is vacuum tubes of 450°C.
 
Compared with photovoltaic power generation, solar thermal power generation can store the heat of the sun in the working medium and release it on cloudy days and at night to achieve continuous power generation. There will be more than 5,000 hours of full-time operation in a year, which can be used as a basic power source in the power grid. It can be said that the prospect of solar thermal power generation is better than that of photovoltaic power generation. However, there is still a long way to go. Improving the performance of key components, solving related technical problems, reducing business costs, and implementing national policies and improving laws and regulations are all issues that cannot be avoided.