Among the known clean energy sources, solar energy is undoubtedly the renewable energy that can be developed and has the largest

reserves on the earth. When it comes to the use of solar energy, you will first think of photovoltaic power generation. After all, we can

see solar cars, solar power chargers and other things in our daily life. In fact, there is another way to use solar energy, solar thermal

power generation.

Understand light and heat, remember light and heat

Photovoltaic power generation and photothermal power generation all use solar energy for power generation. The difference is that

the principle of utilization is different.

Photovoltaic effect is the basic principle of solar photovoltaic power generation, and solar cells are the carrier to complete the conversion

of solar energy to electric energy. Solar cell is a semiconductor material containing P-N junction. P-N junction can absorb sunlight and

establish an electric field inside. When a certain load is connected on both sides of the electric field, current will be generated on the load.

The whole process is the basic principle of solar photovoltaic power generation.

The principle of solar thermal power generation is to concentrate the sunlight to the solar collector through the reflector, use the solar

energy to heat the heat transfer medium (liquid or gas) in the collector, and then heat the water to form steam to drive or directly drive

the generator to generate electricity.

In brief, solar thermal power generation is divided into three parts: the heat collection part, using solar energy to heat the heat conduction

medium, and finally driving the engine to generate power through the heat conduction medium. For each link, there are different ways to

scientifically try to form the optimal design. For example, there are mainly four types of heat collection links: slot type, tower type, dish

type and Nefel type; Generally, water, mineral oil or molten salt are used as heat conduction working medium; Finally, power can be

generated through steam Rankine cycle, CO2 Brayton cycle or Stirling engine.

So how does solar thermal power generation work? We will use a demonstration project that has been put into operation to explain in detail.

First, the solar power plant consists of heliostats. The heliostat is controlled by the computer and rotates with the sun. It can reflect the sunlight of

the day to the central point. The heliostat covers a small area, can be placed separately, and can adapt to the terrain without a deep foundation.

The power plant includes hundreds of heliostats, which can be connected to each other through WIFI to improve efficiency, concentrating sunlight

reflection on a large heat exchanger called a receiver on the top of the tower.

In the receiver, the molten salt fluid can absorb the heat accumulated in the sunlight here through the outer wall of the pipe. In this technology,

molten salt can be heated from 500 degrees Fahrenheit to more than 1000 degrees Fahrenheit. Molten salt is an ideal heat absorbing medium

because it can maintain a wide working temperature range in the molten state, allowing the system to achieve excellent and safe energy

absorption and storage under low pressure conditions.

After passing through the heat absorber, the molten salt flows downward along the pipes in the tower and then enters the heat storage tank.

After that, the energy is stored in the form of high temperature molten salt for emergency use. The advantage of this technology is that liquid

molten salt can not only collect energy, but also separate energy collection from power generation.

When electricity is needed during the day or at night, the water and high temperature molten salt in the water tank respectively flow into the

steam generator to generate steam.

Once the molten salt is used to generate steam, the cooled molten salt is cooled back to the storage tank through the pipeline, then flows back to

the heat absorber again, and is reheated as the process continues.

After driving the turbine, the steam will be condensed and returned to the water storage tank, which will return to the steam generator if necessary.

Such high-quality superheated steam drives the steam turbine to operate with the highest efficiency, so as to generate reliable and continuous

power during peak power demand. The process of steam generation is similar to that in conventional thermal power or nuclear power plants,

with the difference that it is completely renewable and has zero waste and harmful emissions. Even after dark, the power plant can still provide

reliable power from renewable solar energy on demand.

The above is the whole operation process of a group of solar thermal power generation systems. Do you have a deeper understanding of solar

thermal power generation?

So, it is also solar power generation. Why is solar thermal power generation always “unknown”? Solar thermal power generation has a certain

exploration value in the scientific community. Why is it not widely used in human daily life?

Photothermal power generation vs photovoltaic power generation, which is better?

The utilization of the same kind of energy has produced different affinity, which is inseparable from the advantages and disadvantages of solar

thermal power generation and photovoltaic power generation.

From the perspective of heat collection, solar thermal power generation requires higher application area than photovoltaic power generation.

Photothermal power generation, as its name implies, takes heat as the standard and requires high temperature irradiation, while photovoltaic

power generation generally has no such high requirements for heat. The intensity of solar radiation in the place where we live is not enough for

the construction of solar thermal power plants. Therefore, in our daily life, we are not familiar with solar thermal power generation.

Considering from the aspect of heat conduction medium, the molten salt and other substances used in photothermal power generation are

superior to the high cost and low life photovoltaic cells due to their low cost, high value and sustainable utilization. Therefore, the energy

storage capacity of photothermal power generation is much higher than that of photovoltaic power generation. At the same time, due to the

good energy storage effect, solar thermal power generation will be less affected by weather and environmental factors when connected to

the grid, and its response to grid load fluctuations will be low. Therefore, in terms of power generation schedulability, solar thermal power

generation is better than photovoltaic power generation.

Considering from the link of heat conduction medium driving engine power generation, photovoltaic power generation only requires

photoelectric conversion, while photothermal power generation requires photothermal conversion after photoelectric conversion, so it can

be seen that the steps of photothermal power generation are more complex.

However, one additional link of solar thermal power generation can be applied to other aspects. For example, the heat generated by solar

thermal power generation can reduce the salinity of seawater, desalinate seawater, and can also be used in industrial production. This

shows that photothermal power generation is more widely used than photovoltaic power generation.

But at the same time, the more experienced a link is, the higher the requirements for mastering science and technology will be, and the

more difficult it will be to apply it to the actual engineering field. Photothermal power generation is more difficult than photovoltaic

power generation, and China’s research and development of photothermal power generation starts later than photovoltaic power

generation. Therefore, the technology of photothermal power generation is still being perfected.

Solar energy is a very effective way to solve the current problems of energy, resources and environment. Since solar energy was found to

be used, the phenomenon of energy shortage has been alleviated to a certain extent. The advantages and characteristics of solar energy

make it irreplaceable in many energy fields.

As two main ways of using solar energy, solar thermal power generation technology and solar photovoltaic power generation technology

have different advantages and application fields, and have their own advantages and development prospects. Where solar power generation

is developing well, there should be both solar thermal power generation system and photovoltaic power generation system. In the long

run, the two are complementary.

Although the solar thermal power generation technology is not well known for some reasons, it is a relatively better choice in terms of cost,

energy consumption, application scope and storage status. We have reason to believe that one day, both solar photovoltaic power generation

technology and solar thermal power generation technology will become the pillar of sustainable, coordinated and stable development of

human science and technology.