Did you know in the historic era, people used mirrors to light up the house? The same technology is used again today to create a concentrated solar power plant.
The sun provides us with two powerful sources of power: light and heat. While a solar power panel uses sunlight to generate electricity, CSP (concentrated solar power) panel uses both light and heat to generate power.
Solar energy is an emerging technology to generate electricity without contributing to global warming. It can generate power directly, indirectly or by combining 2 technologies. While solar panels require silicon and other elements, CSP technology utilizes mirrors.
So, what is a CSP plant and how does it really work? Let’s see step by step before we get to its various designs.
What is a Concentrated Solar Power Plant?
A CSP plant comprises of mirrors or lenses along with fluid and turbine. These mirrors are combined in such a way that they tap sunlight in concentrated form. The heat of this concentrated sunlight generates power to produce electricity.
So, you can say this plant uses solar power indirectly to generate electricity. Now, let’s see how the basic plant works.
How Does a CSP System Work?
Even though a CSP plant has various designs, the basic way of functioning is the same for all:
- The mirrors or lenses reflect sunlight and trap it in one place.
- Concentrated sunlight falls on a receiver connected to the mirrors.
- This receiver has a fluid that is a conductor of heat, such as molten salt or oil.
- The trapped sunlight heats the fluid in the pipe which in turn flows towards the turbine.
- This heats water in another container which converts into steam.
- The stream flows towards the turbine, which converts it into electricity.
- This electricity lights up several homes and offices in the area.
Various CSP Plant Designs
There are 4 types of CSP plants all over the world:
Structure: It comprises of multiple U-shaped mirrors in a row. A metallic pipe runs through the center of this line which contains the hot liquid. This pipe leads to a container that has hot water. The container leads to the turbine or generator that produces electricity.
Working: U-shaped mirrors concentrate light upon the pipe that heats the liquid up to 350°C or 662°F. This liquid flows towards the container and heats the water into steam. The steam naturally flows into the generator turbine which converts it into electric energy.
Capacity: An individual trough can generate 80 MW of electricity.
Solar Power Tower
Structure: The design consists of a tower that has flat standing mirrors placed on both sides. These mirrors are called heliostats, placed in a way that they all reflect sunlight at one point. The tower is connected to storage tanks, a steam turbine, and wires.
Working: The top of the tower where the mirrors concentrate sunlight is the receiver that contains molten salt. The working fluid can heat up to 1000°C or 1832°F. This heated fluid, in turn, heats water to convert it into steam. Some of it goes to storage tanks in case of a lack of sunlight. The steam turbine produces electricity and lights up the connected areas.
Capacity: The maximum capacity of a tower so far is 392 MW in the USA.
Structure: The structure is very similar to that of a parabolic trough. Only, instead of curved mirrors, there are thin and flat ones. Not only are they more cost-effective, but they can reflect more light than curved mirrors too.
Working: The mirrors reflect light to metallic pipes which are the receivers containing the working fluid. One receiver gets light from several lines of mirrors, heating the liquid to 550°C or 1022°F. While some of the liquid transfers to a storage tank for dark or cloudy hours, the rest creates steam by heating water at 285°C or 545°F.
Capacity: 1 plant can produce 1.4 MW of electricity.
Structure: A single parabolic dish consists of mirrors joined into a dish, similar to but larger than a satellite dish in shape. These mirrors reflect light to the focal point of the dish which has the receiver. It connects to several thin tubes that lead to the generator.
Working: The receiver contains molten salt which is heated at 700°C or 1292°F. It is connected to tubes containing helium or hydrogen gas. The heated gas opens into cylinders connected to the tubes. From the cylinders, the gas passes on to the generators which convert it into electricity.
Capacity: A plant can produce 50 KW of electricity.
Cost of Concentrated Solar Power
Across several regions, the cost of solar power using CSP technology ranges between 5-10 cents per KW. The lowest is the cost in Chile as of October 2017 while the highest price of 9.4 cents per KW is in Dubai.
Concentrated Solar Power Companies
Following are some of the companies that have invested in CSP projects across the world:
- BrightSource Energy
- Abengoa Solar
- Solar Reserve
- Trivelli Energia
- Abros Green
- Torresol Energy
The Future of CSP
Considering the efficiency of CSP technology, Greenpeace International and International Energy Agency’s group, SolarPACES has conducted research. According to that, by 2050, CSP alone will be a source of electricity for 25% of the world. investments will increase up to 102 billion dollars.
How else do you feel can the earth be made greener?