Concentrated Solar Power

Key Terms

• Reflector: a mirror that reflects the sunlight and focuses (concentrates) it onto a single receiver

• Receiver: a system that takes in the energy directed from the reflector and converts it into usable energy

How It Works

In a CSP system, there are dozens or hundreds of reflectors that focus sunlight onto a single receiver, allowing a great amount of energy and therefore heat. In this receiver, there is a high-temperature fluid that is heated by the sun's energy. The fluid is heated to its boiling point when it then turns into steam. The steam then turns a turbine, spinning a conventional generator. This last part — fluid to steam to electricity — is very similar to geothermal energy. There are four main types of CSP systems: the parabolic trough system, Linear Fresnel reflectors, central receivers, and dish/engine systems. 

Parabolic Trough System: The parabolic trough system has a long u-shaped parabolical reflector that focuses the sun's rays on a receiver pipe located at the center of the curve. The collector tilts with the sun to keep sunlight focused on the receiver as the sun moves from east to west during the day. This means that a parabolical system can concentrate the sun's energy up to one hundred times its normal intensity because of its shape.

Linear Fresnel reflectors: Linear Fresnel reflectors are a type of system where the receivers are located just above the reflectors. They use a focal lens effect, which allows the systems to concentrate the sun's energy up to thirty times its normal intensity. Furthermore, the multiple receivers on each panel reduce the blockage of sunlight to other panels, as well as reduce material costs. 

Central Receiver System: Central receivers are where there is a large field of flat reflectors called heliostats. All of them concentrate sunlight onto a single receiver at the top of a tower. This allows the system to concentrate the sun's energy to as much as 1,500 times its normal intensity.

Dish/Engine System: Finally, the dish/engine systems use a mirrored dish very similar to a large satellite dish. The dish is covered in reflectors that concentrate the sun's power onto a receiver that is pushed out in front of the reflectors. These systems always point directly at the sun, heating the working fluid to as much as 1,380ºF.

How It Is Renewable Energy

The sun will never run out. Therefore, we will always have plenty of solar energy to use. Furthermore, CSP panels do not release any carbon dioxide emissions, except during the manufacturing process. This is because CSP panels do not require a combustion process.

Advantages and Disadvantages

Advantages

The most advantageous aspect of CSP is its incredible flexibility. The same design for a CSP plant can satisfy a variety of uses, and the different types of CSP plants all have the same fundamental parts. In addition, CSP can stabilize a renewable-focused grid by providing backup power when conditions are unfavorable for other types of renewable energy. The Department of Energy is also running a long-term program working to reduce the cost of CSP while increasing efficiency, which will help to improve CSP's prevalence in the future.

Negative Impacts

CSP uses a lot of space, and CSP farms can be considered hypocritical for causing deforestation. However, it is less space than that taken over by fossil fuel drilling and mining operations, and CSP panels still allow green space to stay. Some also accuse CSP panels of high transportation and manufacturing emissions costs, which is a legitimate concern. However, this is an important example of how climate solutions must be deployed in tandem; industrial solutions. Improving the manufacturing processes — as well as transportation — will fastly reduce the amount of greenhouse gas emissions from CSP panels.

Conclusion: Our Take

CSP is still an emerging industry, and despite the private sector's recent successes, CSP has not gained a hold on the economy yet. However, in the future, CSP may be able to supplement other forms of renewable energy or even become competitive with them.