Solar Power Tower: How Do They Work?
From their inception, solar power towers have been an amazing example of engineering prowess, allowing the earth to generate renewable energy.
A solar power tower is a system that uses sunlight and converts it into energy and electricity that can be utilized by using a large-scale solar setup. Solar power towers are one of the main parts of a solar power plant.
This structure uses a collection of movable mirrors or “heliostat” that is laid out in an area to gather and redirect sunlight towards the solar tower. Solar power towers are also known as “heliostat power plants”.
With this mechanism of collecting and concentrating solar energy, solar towers can produce renewable energy.
As mentioned above, as one of the main parts of a solar power plant, the solar power tower is purposely placed in the center and is surrounded by many mirrors.
These mirrors or “heliostats” are either curved or flat and are used to track the Sun to catch the sunlight, which is then reflected to the solar tower. Each of these mirrors is computer-controlled to track the sun’s position.
During the day, the heliostats rotate to efficiently focus on the sun’s position so they may reflect most of the sunlight towards the solar power tower’s “receiver”. This receiver is placed at the top of the tower.
In the receiver, a heat-transfer fluid is heated and is used to generate steam. This generated steam is then used in a turbine generator to produce electricity. Some power towers around the globe use a working fluid.
Other advanced iterations are also experimenting with high-temperature molten salts or sand-link particles to make the most of the power cycle temperature.
What do solar power towers do for the environment?
Solar power towers have a great impact on the environment. They do not pollute the air or water and do not produce greenhouse gases during energy generation. Here are the main advantages and disadvantages of these systems.
Advantages
1. Cleaner and greener energy
Solar power towers, along with other solar power technologies, contribute to an electricity generation that is renewable compared to other types of generated electricity.
Unlike fossil fuels, coal, nuclear, oil, and other non-renewable energy resources, the energy collected and generated by solar power towers can be regarded as a “cleaner” energy source.
With this, there are several obvious environmental advantages to having solar power towers as an alternative power source.
For one, compared to non-renewable energy resources, the utilization of solar power towers does not create air pollution, water pollution, or deplete finite resources.
However, despite these advantages of using solar power towers, there are still associated disadvantages and environmental effects in building and having these solar power technologies.
2. The amount of solar power is produced daily
Solar power towers generate electricity that is relatively higher than other energy production methods.
On top of this, by simply adding many heliostats, solar power plants will be able to create a power plant that can generate a huge amount of clean and sustainable energy.
As long as there is sunlight to harness, these solar power towers can produce electricity. This also explains why solar power towers are strategically placed in deserts.
3. Added value on dry and bare lands
Typically, solar power plants would need to be located in a place that would get a lot of sunny days, such as deserts or bare lands. This would mean that dry and bare lands are put into good and efficient use.
Since these power plants can produce huge amounts of electricity, empty deserts and bare lands are not able to become green energy production facilities.
Disadvantages
1. Greenhouse gases
Based on what they call a “life cycle analysis”, it shows that solar power towers still emit greenhouse gases that are associated with the construction and fabrication of the mirrors and other materials used in building the tower.
Greenhouse gas emissions are also emitted during the recycling and dismantling involved once the solar power plant is utilized.
While it may be concerning, it should be noted that these emissions are significantly lesser compared to the ones emitted by other non-renewable energy resources such as fossil fuels and oil.
2. Materials involved in the construction
Other negative impacts on the environment also include the toxic materials used in making the important parts of the plant such as the “photovoltaic cells”.
Aside from that, the water demand involved in the operation of the plants can also be seen as a disadvantage. The design and functions of a solar power tower usually demand large volumes of water.
However, there have been iterations and alternatives to its engineering where cooling technologies are studied and applied.
3. Takes up a lot of space
Normally, solar power towers would need a massive number of installed heliostats for it to gather their desired amount of solar power on the tower. This would require a huge space of land.
With this, solar power towers are typically restricted in locations that have extensive tracts of land, like deserts.
4. Risk of bird casualties
The area of a solar power tower has typically high temperatures. In the past, birds that fly over in the area of the focused rays have died. Some birds can experience scorched feathers or worse, death.
There have been reports of bird casualties at power plants and reported deaths of about one bird every two minutes.
Aurora solar thermal power project
In August 2017, it was announced that South Australia will build a solar power tower with a capacity of 150 MW, this project was the Aurora Solar Energy Project.
Hailed as a brand new start, Solar Reserve’s Aurora Solar Energy Project gave hope to Port Augusta, Australia after the closure of its coal power station in 2016.
Proposed and designed to generate an estimated 495 GW hours of electricity per year, the power plant was hoped to power a massive number of 90,000 households – about 5% of South Australia’s electricity demand.
The solar power plant utilizes molten salt technology to store the energy, as gathered by the facility’s array of heliostats. The proposed facility was supposed to have a storage capacity of 8 hours at full power.
However, in April 2019, the South Australian Energy Minister announced that the project was canceled. Authorities report that the cancellation was due to the lack of revenue certainty for the technical demonstrator project.
Additionally, the South Australian opposition leader pointed out the failure of the government in securing finance to establish a new electricity interconnector to help reduce the maximum wholesale cost of electricity.
In December 2019, a local South Australian renewable energy company announced that it acquired the project, along with the early-stage solar projects from New South Wales.
1414 Degrees, the company that acquired the project later on renamed the site as “Aurora Solar Energy Project”.
In May 2021, the company announced that the first stage of the project will launch in mid-2021 with a facility that can produce 70 MW. This would then be followed by TESS (Thermal Energy Storage System).
Unfortunately, by June 2020, the thermal storage was not fully developed, which forced the project to be reshaped with a bigger battery, solar PV, and CSP. The power plant is expected to be constructed in 2023.
The history of solar power towers
National Solar Thermal, 1979
The National Solar Thermal Test was the very first solar power tower operated by Sandia National Laboratories for the U.S. Department of Energy. The power plant still runs today as a test facility for scientists and universities.
Initially constructed as a response to an energy crisis in 1979, the National Solar Thermal Test continues to provide data for the design, operation, and construction of components and systems for proposed solar power plants.
Solar One, 1982
Solar One, the first commercial solar power plant ran from 1982 to 1988 in the Mojave Desert, California. Its first iteration was not efficient enough, which led to its modification into Solar Two.
The Solar Two switched to using molten salt, a change from using oil as a heat-transfer mechanism. By this, Solar Two was able to store thermal energy and has the advantages of being non-flammable and non-toxic.
PS10 Solar Power Plant
Producing 11 MW of power, the PS10 is a solar power tower project outside the United States built in 2007.
Located near Seville, Spain, the facility is part of a larger system that envisions producing 300 MW of energy.
Jülich Solar Tower
Built in 2008, the experimental Jülich solar tower is Germany’s only power plant using the solar power tower technology.
Later in 2011, the facility was sold to the German Aerospace Centre in 2011, and still remains in operation.
Cerra Dominador CSP Project
The Cerra Dominador CSP Project was Chile’s solar power tower project and Latin America’s first solar tower project.
Chile invested $1.3 billion into the project with the hopes of phasing out coal-fired power by 2040. Additionally, the facility had the goal of being carbon neutral by 2050, however, the project was delayed due to the funder’s bankruptcy.
Now, there are a lot of solar power towers around the world and are located in various countries. Some are experimenting and developing iterations and developed engineering to provide cleaner and more efficient energy.
Solar power towers around the globe
Nowadays, there are solar power towers that can be found around the globe, and more are even in development.
Ideally and strategically, the location of a solar power tower should be in a place that is flat, dry and does not experience a lot of storms and strong winds.
Normally, it should be a place with the sunniest days and with as much solar radiation. With this, it should be avoided that the location is an area where it receives significant amounts of rain and snow.
Areas such as the Southwest United States, Chile, India, South Africa, Southern Africa, the Middle East, and China are some of the good locations that fit the criteria the best.
| Name of Power Plant | Location | Power Production Capacity (MegaWatts) | Number of Collectors | Height of Tower (Feet) |
|---|---|---|---|---|
| Sierra SunTower | Mojave Desert, United States | 5 MW | 24,000 | 150 ft |
| The Solar Project | Mojave Desert, United States | 10 MW | 1,926 | 100 ft |
| Gemasolar, Thermosolar Plant | Seville, Spain | 19.9 MW | 2650 | 460 ft |
| PS20 | Sanlúcar la Mayor, Spain | 20 MW | 1255 | 541 ft |
| Qinghai Gonghe CSP | Gonghe, China | 50 MW | 689 ft | |
| Shouhang Dunhuang | Dunhuang, China | 100 MW | 1200 | 722 ft |
| Crescent Dunes | Tonopah, United States | 110 MW | 10,347 | 656 ft |
| Cerro Dominador Solar Thermal Plant | Calama, Chile | 110 MW | 10,600 | 820 ft |
| Ouarzazate Solar Power Station | Ouarzazate, Morocco | 250 MW | 7,400 | 820 ft |
| Ashalim Power Station | Negev Desert, Israel | 260 MW | 50,600 | 853 ft |
| Ivanpah | Mojave Desert, California | 392 MW | 173,500 | 459 ft |
| Noor Energy 1 | Saih Al-Dahal, Dubai | (building since 2022) | (building since 2022) | (building since 2022) |
| Redstone Solar Thermal Power | Cape Province, South Africa | (project slated for 2023) | (project slated for 2023) | (project slated for 2023) |
Future Trends and Developing Iterations for Solar Power Towers
Improvements in the design of thermal fluid systems
By improving the thermal fluid system designs of solar power towers, the efficiency of the power plant’s functionality will be enhanced. Additionally, this will also reduce operational costs.
For instance, upgrading the two-tank thermal system to a one-tank thermal system with thermal fillers and oxygen blankets can improve the efficiency and effectiveness of solar tower power plants.
Development of heat transfer fluids
The most distinct design of solar power towers is the use of heliostats to redirect solar radiation to a specific spot of the tower, also referred to as the receiver, to heat the fluid inside it which would be used to generate electricity.
Before, older designs of solar power towers used steam as a heat transfer fluid. Later on, new designs used molten salts because of their inherent capabilities in increased heat transfer and better storage abilities.
With this, better developments in heat transfer fluids or better energy transfer mechanisms would also indicate better functionality and efficiency of solar power towers.