What Is Solar Thermal Power Plant?
What is a solar thermal power plant?
A solar thermal power plant, also known as a concentrated solar power plant, is a facility that converts sunlight into electricity. The power plant uses mirrors to concentrate sunlight onto a receiver, which absorbs and converts the solar thermal energy to heat. This heat is then used to boil water, producing steam that spins a turbine and generates electricity.
Unlike photovoltaic solar panels that directly convert sunlight into electricity, solar thermal power plants use the heat from the sun’s rays to drive a steam turbine. The thermal energy can be stored more easily than electricity, allowing solar thermal plants to provide dispatchable power that can be delivered when needed, day or night.
Solar thermal power plants consist of two parts: one part where solar energy is collected and converted to heat, and another part where the heat is used to produce electricity through a steam turbine generator. This technology allows renewable solar energy to provide reliable and flexible electrical power.
How does a solar thermal power plant work?
A solar thermal power plant converts sunlight into electricity. It does this by using mirrors to concentrate sunlight onto a receiver containing a heat transfer fluid. The high-temperature heat transfer fluid is then used to produce steam to drive a turbine and generator to generate electricity.
Here are the main components and process:
Solar field – This consists of a large array of sun-tracking mirrors (heliostats) that focus sunlight onto a receiver at the top of a tower. The concentrated sunlight heats up the transfer fluid inside the receiver to a high temperature, often over 1000°F.
Heat exchanger – The hot heat transfer fluid from the receiver is passed through a heat exchanger, which generates high-pressure superheated steam.
Turbine and generator – The steam drives a turbine coupled to an electrical generator to produce electricity. The exhausted steam is condensed back to water and recycled to the heat exchanger.
Thermal energy storage systems may also be incorporated to store excess heat, allowing power generation to continue even when the sun isn’t shining.
Parabolic trough and linear Fresnel reflector plants use similar principles but with long parallel rows of mirrors focusing sunlight onto U-shaped receivers mounted above the mirrors.
Types of solar thermal power plants
There are four main types of solar thermal power plants:
Parabolic trough
Parabolic trough systems concentrate sunlight onto a receiver tube located at the focal point of the parabolic reflector. A heat transfer fluid heated in the tubes drives a steam turbine or engine generator to produce electricity. Parabolic troughs allow higher temperature operation which leads to greater efficiency. They are the most mature and proven solar thermal technology.
Solar power tower
Solar power towers (also known as ‘central tower’ systems) use thousands of mirrors called heliostats to reflect sunlight onto a receiver on top of a tall tower. The concentrated light heats a heat transfer fluid that is used to generate steam to drive a turbine and generator. Solar towers can achieve higher temperatures and efficiencies compared to trough systems.
Linear Fresnel reflector
Linear Fresnel reflector systems use long, thin segments of mirrors to concentrate sunlight onto a fixed receiver mounted over the mirrors. These systems capture extra energy by using a secondary mirror that reflects the unused sunlight back onto the receiver. Linear Fresnel designs are simpler and cheaper than troughs.
Parabolic dish
Parabolic dish systems use dish-shaped reflectors to focus sunlight onto a receiver at the focal point. The concentrated energy is captured by a heat engine mounted on the receiver to immediately generate power. Parabolic dishes allow for very high temperatures but require complex tracking and focusing equipment.
Advantages of solar thermal power
Solar thermal power offers several key advantages that make it an attractive renewable energy source.
First and foremost, solar thermal power is renewable. Unlike fossil fuels which are finite resources, the sun provides a virtually limitless fuel source. Solar thermal power plants harness the sun’s energy using mirrors and other equipment, without any emissions or resource depletion.
By tapping into solar energy, solar thermal power also reduces dependence on fossil fuels like coal, oil and natural gas. Widespread adoption of solar thermal technology can decrease the burning of fossil fuels for electricity generation, which is a major contributor to climate change and pollution.
Solar thermal is also cost effective in many parts of the world. Although capital costs are still higher than conventional power plants, the fuel itself is free. This gives solar thermal an economic edge since there are no ongoing fuel expenses. The levelized cost of electricity from solar thermal is competitive with new natural gas and coal plants.
With benefits like being renewable, reducing fossil fuel usage, and having favorable economics, solar thermal power has compelling advantages as an energy solution.
Disadvantages of solar thermal power
While solar thermal power offers many benefits, it also comes with some drawbacks that need to be considered.
One disadvantage is that solar thermal plants require a lot of water for cooling. This can put a strain on water resources in arid regions where solar potential is high. Parabolic trough and power tower designs need water for steam generation and to cool the turbines. Typical wet cooling systems consume around 2.5 cubic meters per megawatt hour.
Solar thermal plants also take up a lot of land space due to the large arrays of mirrors needed to concentrate sunlight. While the actual footprint is relatively small, there needs to be adequate spacing between mirrors to avoid shading. Land costs can be an economic barrier, especially near urban areas.
Finally, solar thermal suffers from intermittency issues common with other renewable sources. Power output fluctuates depending on the time of day, season, and weather conditions. Cloudy days and nighttime mean zero solar input. Additional storage is needed to provide electricity when the sun isn’t shining.
Solar Thermal Power Plant Costs
The costs of building and operating a solar thermal power plant can be divided into capital costs and operating costs. The levelized cost of energy (LCOE) is also an important economic metric.
Capital Costs
The capital costs for solar thermal power plants include all the upfront expenses for materials and labor during construction. This includes costs for the land, solar collectors, heat exchangers, turbines, generators, storage systems, and other supporting infrastructure. Capital costs represent the majority of the total costs.
Operating Costs
The operating costs for solar thermal plants include maintenance, repairs, equipment replacement, staffing, insurance, and other ongoing annual expenses to keep the plant running. Operating costs are much lower than capital costs. Parabolic trough plants have lower operating costs than solar power tower or solar dish/engine systems.
Levelized Cost of Energy (LCOE)
The LCOE represents the average cost per unit of energy generated over the lifetime of the plant. It factors in both capital costs and operating costs. Solar thermal plants can have LCOEs competitive with fossil fuels in areas with good solar resources. LCOE continues to decline as technology improves.
Top solar thermal power countries
Several countries around the world have invested heavily in solar thermal power and have significant capacity installed. The top countries using solar thermal power include:
Spain – Spain is the world leader in solar thermal power generation with over 2,300 megawatts of installed capacity. The country has over 50 solar thermal power plants, the largest being Solnova Solar Power Station which has a capacity of 150 megawatts.
United States – The US has several large solar thermal plants, mostly located in the sunny southwest states like California, Arizona, and Nevada. Major solar thermal plants in the US include Ivanpah Solar Electric Generating System (392 MW) and Solana Generating Station (280 MW).
India – India has a number of solar thermal plants under development and is expected to grow its solar thermal capacity substantially in the coming years. Currently, India has plants like the 125 MW facility at Gurajat Solar Park and a 100 MW facility at Ananthapuramu.
China – China has over 200 megawatts of installed solar thermal capacity. The country’s largest solar thermal plant is in Dunhuang with a capacity of 100 megawatts. China aims to grow its solar thermal capacity to over 1 gigawatt by 2022.
Morocco – Morocco is home to one of the world’s largest solar thermal energy projects, the Noor Ouarzazate complex. When fully completed, it will have over 500 megawatts of solar thermal capacity, providing a substantial portion of Morocco’s renewable energy.
Major Solar Thermal Power Companies
Some of the major companies involved in developing and building solar thermal power plants include:
Abengoa
Abengoa is a Spanish renewable energy company that has built some of the world’s largest solar thermal power plants. They developed the Solana Generating Station in Arizona, which was the largest solar plant of its kind when it opened in 2013.
Acciona
Acciona is another Spanish company that has been involved in building CSP plants. They partnered with Abengoa on the Solana plant and have worked on other parabolic trough projects around the world.
BrightSource Energy
BrightSource is based in the US and has focused on power tower technology. They built the Ivanpah Solar Power Facility in California, which is one of the world’s largest solar thermal power plants.
SolarReserve
SolarReserve is a US company that has developed unique molten salt power tower technology. They have built plants utilizing this technology in the US and Australia.
Notable Solar Thermal Power Plants
There are several large-scale solar thermal power plants operating around the world. Three of the most significant are:
Ivanpah Solar Electric Generating System
The Ivanpah Solar Electric Generating System located in the Mojave Desert in California is one of the world’s largest solar thermal power plants. This concentrated solar power plant has a gross capacity of 392 MW and utilizes 173,500 heliostats (mirrors) to focus sunlight on three central power towers. Ivanpah was connected to the grid in 2013.
Solana Generating Station
The Solana Generating Station in Arizona has a gross capacity of 280 MW. This parabolic trough plant was opened in 2013 and was the largest solar thermal power plant in the world at the time. Solana includes molten salt thermal energy storage which allows it to generate electricity even when sunlight is not available.
Noor Complex
The Noor Complex in Morocco consists of three adjacent concentrated solar power plants with a combined capacity of 510 MW. Noor I came online in 2016, Noor II in 2018, and Noor III in 2019. The parabolic trough design includes molten salt storage technology. Noor is one of the largest solar thermal installations in the world.
Future of solar thermal power
The future looks bright for solar thermal power. As technology continues to improve and costs decline, solar thermal is poised for strong growth worldwide. Here’s a look at the potential ahead:
Growth potential: Solar thermal currently accounts for a small fraction of global electricity production. But its share is expected to grow substantially in the coming decades. The International Energy Agency predicts solar thermal capacity could increase 10-fold by 2050 under a sustainable development scenario. With its environmental and cost benefits, solar thermal can play a major role in the transition to renewable energy.
Technological improvements: Engineers are working to boost the efficiency and storage capacity of solar thermal plants. New high-temperature fluids, advanced heat exchangers and thermal energy storage systems could enable plants to operate longer into the evening. Hybrid designs that combine solar thermal with other generation like natural gas show promise. Continued innovation will further improve performance and competitiveness.
Forecasts: Projections estimate the global solar thermal market will grow at over 10% annually through 2030. Capacity is forecast to reach 1,500 gigawatts by 2050. Key markets like China, South Africa and the Middle East are investing heavily in solar thermal. With falling prices and supportive policies, solar thermal can become a mainstream energy source and continue its upward trajectory.
