Concentrated Solar Power: A Comprehensive Guide

Concentrated Solar Power

We are racing against time to save ourselves from the imminent disaster – the tumbling effect of carbon emissions, global warming, and climate change.

It all began when we discovered how fossil fuels can make our lives easy and simple. We started burning them more and more until we woke up to the damage we are causing the environment, thereby endangering our own survival. 

Then began the race against time to come up with an alternative fuel that will not only not damage the environment, but will also reverse the damage already caused. The abundant and free solar energy is a downright winner in this regard both at individual levels and for commercial and utility-scale production. 

Most of us are already aware of photovoltaic technology and its benefits. The world has embraced this technology with increased awareness among the younger generation. However, we are also aware of its limitations and potential for improvement. 

In our efforts to achieve net-zero emissions by 2050, newer technologies are being developed to harness the sun’s energy. One of the most promising among them is concentrated solar power. 

This article attempts to explain concentrated solar power from the perspective of a layperson. Here you will find all that you need to know about it, including concentrating solar-thermal power basics, how it works, its types, and its advantages and disadvantages. You will also find here a comparison between concentrated solar power and photovoltaics and how it can help us generate electricity on a utility scale.

Table of Contents
    Add a header to begin generating the table of contents

    What is concentrated solar power?

    Concentrated solar power or CSP is also known as concentrating solar power and concentrated solar-thermal power. In simple terms, this technology uses mirrors to reflect and focus sunlight onto a thermal receiver. The intense CSP energy heats up the fluid (heat-transfer fluid or HFT) in the receiver to high temperatures. This heat or thermal energy is used to turn a turbine and thus generate electricity.

    Unlike the solar energy generated by photovoltaic panels, the thermal energy contained in the fluid can be stored for later use. CSP energy also has direct industrial applications in water desalination and food processing.

    Concentrating solar-thermal power basics

    Concentrated solar-thermal power technology uses mirrors to reflect, focus and harness solar thermal energy to generate electricity. At a CSP plant, mirrors are positioned in such a way as to reflect and concentrate the sunlight received onto a thermal receiver. This thermal receiver is filled with a heat transfer fluid or HFT to absorb the thermal energy. The thermal energy in the fluid can be stored for later use or used immediately to power a motor or turn a turbine connected to a generator. As the turbine turns, electricity is generated.

    Concentrated solar power technology is used in utility-scale power plants to generate large-scale electricity for feeding into an electrical grid. One of the advantages of using concentrated solar-thermal power technology is the flexibility it offers in power generation. With the right energy storage arrangements, the heated-up heat transfer fluid can be stored for use when the sun is not shining. Such as at night or on rainy or cloudy days.

    The most lucrative aspect of CSP technology, especially when compared to photovoltaic technology, is its ability to store energy. Again, as solar energy is stored as thermal energy, CSP systems can work in conjunction with thermal power plants, where coal or natural gas is used as fuel for heating. 

    Concentrated solar-thermal power technology is not commonly used at a small-scale or individual level. In the United States, concentrated solar power plants generate roughly 1.8 Gigawatts (GW) of electricity. 

    What are the main types of concentrated solar power?

    The sunlight can be concentrated by four different methods. 

    1. Parabolic dish
    2. Solar power tower
    3. Parabolic trough
    4. Linear Fresnel system

    Parabolic dish: These resemble a satellite dish. Mirrors are arranged in the shape of a satellite dish with the thermal receiver placed at the focal point of the arrangement. The sun’s rays get reflected by the mirrors and converge at the focal point. In a typical concentrating solar-thermal system, a heat engine is placed at the focal point.

    The parabolic dish is immensely popular than other concentrated solar-thermal power systems because of the limited space they need for the setup. Also, a flat surface is not essential for installing a parabolic dish.

    Solar power tower: This arrangement consists of a host of mirrors called heliostats set up at the ground level with a central receiver placed on top of a tower. Supported by a tracker system, these heliostats reflect sunlight and focus it on the central receiver. The heat transfer fluid in the central receiver absorbs the heat, which is used to generate electricity.

    Molten salt is often used as heat transfer fluid as it can retain heat better and longer than many others.

    Parabolic Trough: This is one of the most common concentrating solar-thermal systems used across the world. Instead of the satellite dish-shaped mirror used in the parabolic dish, this has U-shaped curved mirrors and a tube containing the heat transfer fluid placed in its middle running the entire length. 

    As sunlight falls on the parabolic trough, it gets reflected and concentrated on the tube. The heat transfer fluid will heat up. Once the fluid has absorbed maximum heat, it flows into a generator to produce electricity.

    Linear Fresnel Reflector or IFR: Named so due to its similarity to the Fresnel lens, this arrangement uses rows of flat mirrors or softly curved ones to reflect sunlight. The receiver with heat transfer fluid is kept in the middle of the arrangement parallel to the mirrors. 

    Though similar in concept to a parabolic trough, Linear Fresnel Reflector uses trackers on the mirrors to maximize the solar energy it captures and concentrates on to the receiver.

    How does the efficiency of CSP compare with other renewable energy sources?

    As with other renewable energy sources, the efficiency of concentrated solar-thermal power also depends on various factors. Such as the type of concentrating solar-thermal system and the heat transfer fluid used in the receiver. Across the various concentrated solar-thermal power systems, its conversion efficiency is in the range of 7% and 25%. This is somewhat similar to that of photovoltaic technology.

    In comparison, the conversion efficiency of many other renewable energy sources is much higher. While hydropower comes with a conversion efficiency of 90%, wind power can convert at an efficiency level of 20-40%. With the right technology, the conversion efficiency of wind energy can be boosted to 60%. 

    Concentrated solar power vs photovoltaics

    Both concentrated solar power and photovoltaics absorb solar energy to produce electricity and have similar levels of conversion efficiency. Their similarities end there. The technologies may appear the same, but they are not. There are noticeable differences between the two regarding cost, storage, and applications. 

    Heat energy vs light energy: One of the most obvious differences is that concentrated solar-thermal power technology uses the sun’s heat energy while photovoltaics use the sun’s light energy to generate electricity. In simple terms, though both use sunlight to produce electricity, their technologies are vastly different. 

    Heat transfer fluid vs semiconductor: In concentrating solar-thermal technology, a heat transfer fluid is used to gather solar energy while in solar panels, a semiconductor material converts solar energy into electricity.

    Storage: Another major difference is in the fact that CPV technology allows the heat energy collected to be stored for later use. However, solar panels are not capable of storing the light energy they absorb. 

    Conversion efficiency: Even though the conversion efficiency of concentrating solar-thermal technology is similar to that of solar panels, the newer concentrated photovoltaic technology has raised the efficiency level much higher. It is possible to achieve 30-40% conversion efficiency with concentrated solar panel systems.

    Cost: Solar panels have been around for long and it has seen considerable technological advancements. This means its cost has come down drastically, especially in the last decade. However, concentrating solar-thermal energy is a newer technology and its cost of installation and maintenance is comparatively higher.

    Application: CSP technology is still in its nascent stages and requires direct sunlight to generate electricity. CSP systems are large and usually used in utility-scale electricity generation. This means large tracts of land with direct sunlight are essential for CSP systems. On the other hand, PV panels can be installed for residential, commercial, or utility scales. The technology is more developed to generate electricity using indirect sunlight. 

    Concentrated solar power plants

    Even as photovoltaic technology is increasing its share in electricity generation worldwide, CSP technology is also making progress, albeit in a much smaller way. While solar panels can be deployed for residential, commercial, as well as utility-scale levels, concentrating solar-thermal power is more suitable for utility-scale power generation.

    Because of current technological limitations, concentrated solar-thermal power plants can be built only in areas with high solar irradiance. Moreover, each MW capacity of the CSP plant requires 5-10 acres of land. The high cost of concentrating solar-thermal systems is more manageable when the concentrated solar power plants are at least 100 MW. 

    Noor Power Station: Located in the Sahara desert, the Ouarzazate Solar Power Station, Morocco, is the largest CSP plant in the world with an installed capacity of 510MW. This power plant uses parabolic trough and solar power tower types of CSP technology for power generation. The Moroccan Agency for Solar Energy has also installed solar panels to increase production by 72MW.

    Ivanpah Solar Electric Generating System: Completed in 2014, this is a solar power tower plant located in San Bernardino county, California. It is the largest CSP plant in the US with an installed capacity of 392MW. The power plant has three 450-foot high towers and 173,500 heliostats built on 3,500 acres of Mojave desert.

    Mojave Solar One: Another major solar project in the Mojave Desert, the Mojave Solar plant is a parabolic trough CSP plant with 280 MW capacity. Completed in 2014, this is located in Bairstow, California. 

    Solana Generating Station: Located in Gila Bend, Arizona, this parabolic trough CSP plant has a generating capacity of 280 MW. This was completed in 2013.

    Genesis Solar Energy Project: This parabolic trough CSP plant was completed in 2014 with an installed capacity of 280 MW. It is located in Blythe, California.

    Advantages and disadvantages of CSP

    Nothing in this world is absolutely good or bad. The same is the case with CSP. It comes with both benefits and drawbacks. 

    Advantages of CSP

    The most attractive aspect of concentrated solar power is that it is renewable. As long as the sun is shining, we get free solar energy in abundance, we can continue to convert the heat energy in sunlight to electricity using concentrated solar-thermal technology. It’s sustainable and green and helps in reducing the carbon footprint. It can bring down the level of air pollution and help in containing the devastating effects of climate change.

    Even though sunlight is not available at night, CSP technology allows for storage of the thermal energy. This helps in providing electricity almost continuously without interruptions. As providing uninterrupted power is one of the major drawbacks of both photovoltaic technology and wind power, CSP is a more reliable and predictable source of energy.

    Concentrating solar-thermal technology can work together with other energy sources such as thermal power in a solar-thermal generator for the production of steam for turning the turbine. It is also not difficult to integrate CSP technology into existing steam-based power generators. CSP systems can easily replace fossil fuels in power plants. 

    The operating cost of a concentrating solar-thermal plant is much lower than that of a nuclear plant or one running on fossil fuels. Installing and running a CSP plant is much simpler when compared to these two. Not only is this environment-friendly, but concentrating solar-thermal technology also doesn’t pose any threat to nuclear radiation.

    CSP energy is a good addition to the energy mix for the grid supply, providing stability and reliability. It is also ideal for oil recovery because the steam generated aids in concentrating heavy oil, making it easier to pump.

    CSP also has the potential in the transport segment by helping with the production of economically-viable hydrogen.

    Disadvantages of CSP

    Location and availability of sunlight are two of the major drawbacks of CSP technology. However, these two are also the constraints for solar power and wind energy. Concentrated solar power plants need large tracts of land, making them unviable in areas where people live. 

    Concentrating solar-thermal plants need large quantities of water to operate steam turbines and to cool down thermochemical reactors. Even if we use seawater for this purpose, solar radiation would be a serious concern for the neighboring areas. The bright lights of concentrating solar energy plants tend to attract birds and animals, but the heat may not be good for their survival.

    CSP energy plants don’t come cheap. Thermal energy storage is an expensive affair and not easily available. Molten salt, usually used as heat transfer fluid, has a limited temperature range, solidifies at room temperature and decomposes when the temperature goes too high.

    The high competition in the renewable energy scene makes it difficult for concentrated solar-thermal power technology to compete with the more popular and established photovoltaic technology and nuclear power. As other technologies improve and become cheaper, CSP technologies face the threat of relegation. 

    Final thoughts on concentrated solar power

    Things are looking up for concentrated solar power, with more research being done and technological advancements. The cost of installing concentrated solar-thermal power systems has come down in the last decade. In 2020, the y-o-y reduction in price has been an amazing 18%. However, in 2021, the price of CSP systems started going up. 

    CSP technologies haven’t been developed enough for use in residential and commercial projects. Because of this limitation, solar panels remain more popular among residential users. Even though it can overcome some of the main drawbacks of photovoltaic technology, it continues to remain the lesser-known of the two.

    Scroll to Top