Alien technology tower? Oh, it turns out to be a man-made solar thermal power station

Produced by: Science Popularization China

Author: Hanmu Diaomeng (popular science creator)

Producer: China Science Expo

If a person has never heard of or seen a tower solar thermal power station, then when he sees tens of thousands of mirrors and the tall tower in the middle of the desert from high in the sky, he may really exclaim: Is this alien technology?

The tower solar thermal power station, whose full name is "tower molten salt solar thermal power station" , has such a strong sense of technology brought by its visual effects.

Dunhuang 100MW molten salt tower solar thermal power station

(Photo source: Chinese government website)

Good quality, low price and long life

Although it looks very high-tech, the principle of a tower solar thermal power station is very simple. In summary, a large number of flat mirrors with heliostat function reflect sunlight to the top of the tower, where the molten salt is heated to more than 500 degrees Celsius, and then electricity is generated through the high-temperature molten salt.

This is similar to how a thermal power plant uses coal to heat steam and then uses the steam to generate electricity.

In Naomaohu Town, Yiwu County, Xinjiang, more than 14,000 heliostats in the solar thermal power station illuminate the collector tower

(Photo source: Chinese government website)

So, how do you have such a tall tower? Generally speaking, the things you need are:

Sunlight is equivalent to coal in a thermal power station.

The mirror field is where the plane mirrors are laid.

It has a heliostat function and is responsible for supporting the metal frame of the reflector, the plane reflector, molten salt, and power generation equipment including turbines and generators .

Mirror Field

(Photo source: Chinese government website)

This set of equipment can be said to be of good quality and low price.

Sunlight is to CSP power plants what natural gas is to natural gas power plants and coal is to thermal power plants. Sunlight is always free , which is the biggest prerequisite for supporting all CSP power generation.

The locations of mirror sites are often in deserts and Gobi , where land prices are very low , and in some places it is even free .

A reflector is a plane mirror, which is essentially no different from the plane mirrors used in every household . However, in order to resist wind and sand, the hardness will be different. In order to reflect sunlight with maximum efficiency, the transmittance will also be different. However, no matter how different it is, it is still a plane mirror in essence. After mass production, plus various technical and design optimizations, its cost will inevitably decrease.

Reflector

(Photo source: Chinese government website)

Molten salt, currently a mixture of 60% sodium nitrate and 40% potassium nitrate, is commonly called "solar salt", but this is only a temporary name. At present, all countries are stepping up research on the next generation of cheaper and more powerful molten salts. For example, molten chloride salts made from a mixture of sodium chloride (household salt), magnesium chloride, and potassium chloride are the focus of research and development in China and other countries.

No matter what the next generation of molten salt is, two things are certain: its heat storage and thermal conductivity will be stronger and the cost will be lower .

The most difficult to reduce costs are steam turbines and generators in power generation equipment , because these two types of equipment have been developed for decades, the technology has long been mature, and all possible cost cuts have long been reduced.

In addition to the steam turbine and generator, the equipment cost for realizing the sun tracking function (i.e. the metal support frame that can rotate freely) is also very expensive. This kind of equipment has the highest cost when it is first designed , but once the technology is finalized and subsequent projects start mass production, its cost is mainly reflected in the materials , so its cost will not drop much.

The materials used in solar thermal power plants are very durable . For example, the life of the flat reflector is something you can imagine. Another example is molten salt, which also has a long life. Any material that cannot support a 30-year service life is unlikely to become a candidate for the next generation of molten salt.

Some readers may argue that the current construction cost of tower solar thermal power stations is still relatively high . Compared with other power generation technologies, how can it be called cost-effective?

A big part of the reason for this is that many domestic projects are still in the "demonstration" stage.

Nuclear power is already developing the fourth generation, thermal power generation has also gone through several generations, and tower CSP power stations have not even completed the first generation . It is obviously unfair to compare the cost of the first generation with other industries that have already developed several generations. The development of tower CSP power stations is still worth looking forward to.

Dual attributes: energy storage and environmental transformation

Since tower-type solar thermal power stations use molten salt to store and conduct heat, they are naturally equipped with an "energy storage" function. As a result, they can generate electricity not only during the day but also at night.

It has its own energy storage function , which is the biggest difference from solar power generation and wind power generation.

For an outdoor plane mirror, when it is covered with a lot of sand and dust, if you wipe it with an ordinary rag, the hard sand will easily scratch the glass, which is not advisable.

Workers are performing routine maintenance on the heliostat

(Photo source: Chinese government website)

A lower-cost method is to use a hair dryer to blow away the dust on the mirror, but the dust will float to other mirrors.

Therefore, the most efficient way is to use water to wash from top to bottom. As a result, the desert Gobi, which originally did not grow grass, will inevitably grow a lot of grass after being infiltrated by water from time to time. Grass has a certain role in soil and water conservation, and with grass, there will be sheep.

Seeing this, you must have understood that environmental transformation is another attribute of tower-type solar thermal power stations.

Although the ground and surroundings of Dunhuang's 100MW solar tower power station are still yellow soil now, will the surroundings turn green when we look at it again in five years?

Loess around the 100MW tower solar thermal power station in Dunhuang

(Photo source: Chinese government website)

We expect the answer to be yes. If environmental improvements can be added, this will allow tower solar thermal power stations to go further.

Easy to scale up

We have reason to believe that as tower solar thermal power stations continue to develop and their main technologies continue to iterate, such as low-cost, high-performance molten salts, and lower-cost reflectors and brackets, combined with the advantages of scale, their power generation costs will be expected to drop significantly.

And when this day really comes, its large-scale appearance is inevitable .

Dunhuang 100MW tower solar thermal power station

(Image source: Satellite map screenshot)

The above picture is a screenshot of the satellite map of the Dunhuang 100MW tower solar thermal power station. The question is, since this place can be built, can its surrounding areas be built?

Future construction site selection concept map

(Image source: The author made it based on a screenshot of a satellite map)

There is no doubt that when the technologies of tower solar thermal power stations are further upgraded in the future, the cost is greatly reduced, and the investment returns and environmental improvement benefits can be stably obtained, there will be so many places where they can be built.

Conclusion

The glittering tower in the Gobi Desert is neither a piece of high-tech accidentally dropped on Earth by aliens nor a sun planted by humans. It is a tower-type solar thermal power station developed by scientists.

Although tower solar thermal power stations are still in their infancy, thanks to their huge advantages, I believe that in the near future, many such towers will appear in the desert, storing energy and generating electricity while bringing layers of greenery to the desert.