CSP Technology in Solar Thermal Power Plants

The largest CSP plant (concentrated solar power) in the United States remains the Ivanpah Solar Power Facility, located in California’s Mojave Desert in San Bernardino County. Ivanpah is a solar thermal power plant with a capacity of 386 megawatts, developed through a public-private partnership that includes NRG Energy, BrightSource Energy, and the U.S. Department of Energy. It uses concentrated solar power technology—specifically, power towers surrounded by thousands of heliostats (flat, sun-tracking mirrors) that focus sunlight to generate high-temperature steam for turbines.

Unlike photovoltaic (PV) panels, which convert sunlight directly into electricity, CSP plants generate power by collecting thermal energy. This heat is then used to produce steam, much like conventional thermal power plants that burn fossil fuels—but CSP systems use only sunlight. Operating at very high temperatures, CSP can deliver firm, dispatchable power, particularly when paired with thermal energy storage.

Though the advantages of concentrated solar power include scalability, energy storage integration, and reduced grid intermittency, CSP plants are still rare in the U.S. energy mix. According to the U.S. Energy Information Administration (EIA), solar thermal power plants produced approximately 3 billion kilowatt-hours (kWh) of electricity in recent years—out of over 4,000 billion kWh generated nationwide. Most of this comes from Ivanpah and a few other projects.

How CSP Technology at Solar Thermal Power Plants Works

CSP technology—short for concentrated solar power—generates electricity by using mirrors to concentrate the sun’s heat, also known as solar thermal energy, onto a receiver. The intense heat produces steam, which spins turbines at a solar thermal power plant to generate electricity. One of the advantages of concentrated solar power is that many CSP plants can store thermal energy for later use, allowing them to deliver power even when the sun isn’t shining.

There are several main types of CSP technology used today:

• Parabolic troughs

• Compact linear Fresnel reflectors

• Power towers

• Dish-engine systems

Each method focuses sunlight in a slightly different way, but all use solar heat to drive a turbine and produce electricity.

Like fossil fuel and nuclear power plants, most CSP plants rely on wet cooling systems, which use water to condense steam back into liquid form. While effective, this process can be water-intensive—a concern in arid regions where CSP plants are often located. An alternative is dry cooling, which uses fans instead of water, but it’s typically less energy-efficient.

Some CSP plants are designed as hybrid systems, using a mix of solar energy and natural gas to ensure consistent power generation. While this increases reliability, it also introduces greenhouse gas emissions, reducing the environmental benefits of the solar component.

Beyond electricity, concentrated solar power can also be used in industrial applications like desalination or providing process heat for manufacturing—highlighting its versatility as a renewable energy technology.

Types Of CSP Technologies Used at Solar Thermal Power Plants

Several types of CSP technologies are deployed at solar thermal power plants in the United States. While each design is unique, all forms of concentrated solar power (CSP) share the core principle of using mirrors to focus sunlight onto a central receiver. The captured solar thermal energy heats a transfer fluid, which is then used to generate electricity through steam turbines.

Let’s take a closer look at the primary types of CSP plant designs:

Parabolic Trough CSP Plants

Parabolic trough systems use long, curved mirrors that concentrate sunlight onto a central receiver tube filled with a heat-transfer fluid—usually synthetic oil. This fluid is heated to high temperatures and routed to a heat exchanger to generate steam and drive a turbine. Many CSP plants of this type are installed with single-axis sun tracking, where mirrors follow the sun's movement from east to west.

This is the most established CSP technology in the U.S., with notable utility-scale plants in California’s Mojave Desert, Arizona, and Nevada. Examples include the Solana Generating Station in Arizona, one of the few CSP plants with integrated thermal energy storage.

Dish-Engine CSP Technology

Dish-engine systems use a large parabolic dish—similar in shape to a satellite dish—to reflect and concentrate sunlight onto a receiver at the focal point. The concentrated heat drives a Stirling engine or another type of heat engine, converting thermal energy directly into mechanical power, which is then turned into electricity.

While dish-based CSP technology has demonstrated high efficiency in small-scale applications, no commercial utility-scale CSP plant using this method is currently operating in the U.S. That said, the technology holds promise for remote, modular energy systems that require off-grid power.

Power Tower CSP Plants

Power tower CSP systems use hundreds or thousands of flat, sun-tracking mirrors—called heliostats—to direct sunlight onto a receiver mounted on top of a central tower. These systems typically use molten salt as a heat-transfer and storage medium due to its high thermal capacity and ability to retain heat for hours, allowing for electricity generation even after sunset.

The Ivanpah Solar Electric Generating System in California is the largest operational power tower CSP plant in the U.S. Another example, the Crescent Dunes project in Nevada, was the first to use molten salt for both heat transfer and thermal storage on a commercial scale.

CSP Energy Storage

One of the major advantages of concentrated solar power (CSP) is its ability to incorporate thermal energy storage, allowing CSP plants to deliver electricity even when the sun isn't shining. Unlike photovoltaic (PV) systems, which stop producing power after sunset, a CSP solar thermal power plant can store solar heat and use it to generate electricity hours later—making CSP a valuable contributor to grid stability and peak demand coverage.

Several CSP energy storage methods have been developed and deployed since the mid-1980s. The most common include:

• Two-tank direct systems, where the heat transfer fluid (usually molten salt) is stored in both hot and cold tanks.

• Two-tank indirect systems, which separate the heat transfer fluid and storage medium to improve system flexibility.

• Single-tank thermocline systems, which use a temperature gradient within a single tank to reduce costs and footprint.

These technologies allow CSP plants to store heat for several hours—sometimes up to 10–15 hours—enabling solar thermal power plants to supply electricity during the evening or when cloud cover reduces solar input.

This ability to store solar thermal energy is one reason CSP plants are increasingly seen as a flexible, dispatchable source of renewable power. Storage extends the usefulness of solar beyond daylight hours and reduces the need for fossil fuel backup, making CSP a strategic solution for integrating more clean energy into the grid.

Current projects like Cerro Dominador in Chile and Noor Ouarzazate in Morocco showcase how advanced storage systems in CSP power plants are helping countries meet renewable targets while maintaining grid reliability.

CSP Technology for Desalination Plants: A Dual Solution for Water and Energy Scarcity

CSP technology is gaining momentum as a practical and sustainable solution for powering desalination plants, especially in arid and sun-rich regions. By coupling clean energy from a CSP plant with the energy-intensive process of seawater desalination, this innovative approach addresses two pressing global needs: access to clean water and the transition to low-carbon energy.

The Energy Demand of Desalination

Desalination processes, particularly reverse osmosis, are notoriously energy-intensive. Most facilities still rely on fossil fuels, driving up both carbon emissions and operational costs. Integrating CSP technology allows solar thermal power plants to generate the necessary electricity using the sun’s heat, helping to decarbonize water production while reducing long-term energy expenses.

Advantages of Concentrated Solar Power for Desalination

• Clean and Consistent Energy Supply: In regions that face both high solar irradiance and water stress—such as parts of the Middle East, North Africa, and the southwestern U.S.—CSP plants offer an ideal renewable energy source. These plants use mirrors to focus sunlight and produce thermal energy, which is then converted into electricity to run desalination units.

• Thermal Energy Storage for Round-the-Clock Operation: A key advantage of concentrated solar power is its ability to store heat. CSP plants can operate thermal storage systems—like molten salt tanks—to supply power long after the sun sets. This ensures a stable energy source, enabling desalination plants to run 24/7 without relying on backup fossil fuel power.

• Integrated Infrastructure Opportunities: Co-locating a CSP solar thermal power plant with a desalination facility can optimize land use and infrastructure. Excess heat or electricity from the CSP plant can be directly funneled into the desalination process, increasing system efficiency and reducing energy loss.

FAQs About CSP Technology & Solar Thermal Power Plants

Let’s break down some of the most common questions about CSP plants and how they compare to other solar energy technologies.

How Do CSP and Photovoltaics Compare?

Photovoltaic (PV) panels convert sunlight directly into electricity using semiconductors. In contrast, CSP plants (or concentrated solar power plants) generate electricity by using mirrors to concentrate sunlight and create heat, which drives a turbine.

While both technologies are used in utility-scale solar power plants, PV is far more common due to its lower upfront cost, ease of installation, and ability to generate power in areas with less direct sunlight. PV systems also don’t require water for cooling.

However, CSP technology offers some unique benefits:

• Thermal energy storage: Many solar thermal power plants are designed to store heat, allowing electricity generation after sunset.

• AC power generation: Unlike PV systems, CSP plants produce alternating current directly and don’t require inverters.

• Dispatchable power: The ability to store and release power makes CSP energy more flexible for meeting peak demand.

Still, as battery energy storage systems (BESS) improve and become more affordable, PV systems with BESS may begin to rival CSP plants in energy storage capabilities.

What is the Largest CSP Plant in the World?

The Noor Complex Solar Power Plant in Morocco  is one of the world’s largest CSP plants, with a total capacity of 580 MW. This solar thermal power plant provides clean electricity to nearly 1 million people and includes thermal energy storage using molten salt.

While the Noor CSP facility uses water for cooling and cleaning, newer CSP technologies are being developed to reduce water usage—making them more sustainable. Diesel backup is used only as a safeguard to keep molten salt at optimal temperatures during low production periods.

What are the advantages and challenges of CSP technology?

The advantages of concentrated solar power include:

✅ Dispatchable renewable power: Thermal storage allows CSP plants to provide electricity after sunset, reducing reliance on fossil fuels during peak hours.

✅ High thermal efficiency: CSP can reach temperatures high enough for industrial applications, not just power generation.

✅ Grid stability: As a centralized source of renewable power, CSP technology can help support grid reliability.

That said, there are notable challenges to CSP deployment:

❌ High capital costs: Building a CSP plant requires a larger initial investment than PV.

❌ Water usage: Wet cooling processes consume water—an issue in arid regions, although dry cooling is an emerging alternative.

❌ Geographic limitations: CSP systems rely on direct normal irradiance (DNI), which is only abundant in certain regions like the U.S. Southwest, Northern Africa, and parts of Australia and India.

Concentrating Solar Thermal Power Could Change Power Plants Forever

Although technological and cost issues are holding back more widespread use of CSP plants, the National Renewable Energy Laboratory (NREL) and Sandia National Laboratories are conducting extensive CSP research to help overcome challenges and develop next-generation approaches. Yet, the rapid decrease in the price of photovoltaics (PV) has made CSP less cost-competitive by comparison. Addressing cost issues will be essential for CSP plants to become more widespread and practical.

One big advantage of CSP technology is its ability to store heat to generate clean energy when power demand is highest. This enables CSP to compete with other dispatchable energy sources, like natural gas.

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