Technology to use solar energy at night

One of the biggest disadvantages of solar energy is that it cannot be used at night. But a breakthrough idea reversed this .

Now, with the development of energy technology, people begin to tend to use natural energy sources, such as wind power, solar energy . But if you pay attention, you will find that those The wind-powered machine is often preferred, partly because it is cheaper, and the wind blows all day, and the sun does not. However, a recent study will make you rethink this issue.

Solar energy can be converted into electricity in two ways: one is to use solar batteries, with semiconductor materials capable of absorbing photons and emitting electrons; and the second is to use thermal turbines like other generators, heat from sunlight will evaporate water, and thereby turn turbines and generate electricity. This is also the mechanism of solar power plants.

The biggest problem here is: the sun doesn't shine all day. At night, or even when it is cloudy, the power plants cannot use solar energy. This is the reason why the cost of solar energy is so high, because they cannot run 24/7. Just a cloud fly over, and all power production operations are stalled. Therefore, there is not always solar energy to generate electricity, especially in the evening - when people's electricity demand is highest.

The solution may sound simple: just store solar energy, then take it out when you need it; But this is a problem, until recent research has opened up hope for the energy industry.

In this article, we will learn about how solar reserves are used when the sun goes down. In addition, let's try to understand how the first solar power plant uses this technology.

Solar reserves

In fact, the idea of ​​solar storage is not new. People have found many ways to store solar energy, before converting it into electricity. There are many methods that have been tested, but the effect is not as expected.

People have tried to store solar energy by using it to pump water up high, so that when the water flows down it will produce energy. However, this method is consuming a lot of energy, only about 80% of the solar energy is converted into electricity. The use of solar batteries is also not a good idea because the price is too high.

And then an idea arises: thermal energy is one of the most easily stored forms of energy.

Obviously, the thermal power plant that operates is based on the thermal energy that will generate steam to spin the turbines, so storing heat will help the plant operate when there is no heat supply: let energy The sun heats something, keeping it hot until the sun goes out and uses it to generate electricity.

Of course, in order to realize this idea, we have to find a certain substance, a certain kind of material that can retain heat: it must be stable at high temperatures - about 400 degrees Celsius - otherwise you will have to solve the problem of evaporation and pressure changes. And another condition: this substance must be cheap and easy to find.

And then, one found a substance, white crystals, there are many in your kitchen: it is salt. Table salt melts at very high temperatures, and evaporates at even higher temperatures. And obviously, the supply of edible salt is almost endless and very easy to find. Moreover, the energy loss level is only about 7%.

In fact, the first solar power plant that uses this energy storage does not use salt. Instead, it is a mixture of salt, including sodium and potassium nitrate. Andasol 1 power plant in Grenada, Spain contains about 28,000 tons of this mixture.

Andasol 1

The Andasol 1 power plant in Spain began operation in November 2008. It operates as a normal thermal power plant during the day. Sunlight shines directly into parabolic mirrors to heat a tube filled with oil, to a temperature of about 400 degrees Celsius. Hot oil will be used to boil water, create steam and spin turbines.

And when the sun set, the reserve system began to operate. Basically, the system operates as follows:

Andasol 1's sunlight absorption system is so large that it is capable of absorbing twice as much energy as it needs during the day. The amount of excess energy is transferred to the storage unit, including a lot of large containers containing molten salt at a temperature of about 260 degrees Celsius. This salt is pumped into a heat exchanger to absorb part of the heat oil. This salt, after exchanging heat with a temperature of about 400 degrees Celsius, will be transferred to the next container for storage, until it gets dark.

When the power plant needs stored heat energy, the stored salt will be returned and heated, then the cold salt will return to the first tank. And then the system works all day.

When using salt to store energy, the power plant can operate twice as long as other solar power plants. As in the case of the Andesol 1 plant, the energy generated is 50% more than when not using the storage system. With this method, it is expected to reduce the cost of the solar power plant.

In addition, people have an idea that they will not use intermediates as oil for heating anymore, but will use salt directly, directly participate in two heat exchange processes. Sand will also be a material considered to store heat.

Another group is developing a solar storage system, using molecular effects like photosynthesis: it uses sunlight to separate water molecules into hydrogen and oxygen, then use them as a fuel source.