Concentrated solar power (CSP) is a large-scale electricity generation technology that uses mirrors or lenses to focus sunlight onto a receiver, generating heat that drives a turbine. It’s a genuinely impressive technology, some of the world’s largest solar power plants use CSP, but it works very differently from the photovoltaic (PV) solar panels you’d install on a UK home or business. Understanding the distinction matters if you’re researching solar energy and wondering whether CSP is relevant to your situation.
This guide covers how CSP works, the main types of CSP technology, its limitations for the UK climate, and where photovoltaic solar PV remains the right choice for UK homeowners and businesses.
Contents
- 1 Key Takeaways
- 2 How Does Concentrated Solar Power Work?
- 3 Types of CSP Technology
- 4 The Thermal Storage Advantage
- 5 Why CSP Doesn’t Work in the UK
- 6 CSP vs Solar PV: A Comparison
- 7 Where CSP Is Being Deployed
- 8 Expert Insights From Our Solar Panel Installers
- 9 Frequently Asked Questions
- 9.1 What is concentrated solar power?
- 9.2 Why can’t CSP work in the UK?
- 9.3 What are the main types of CSP technology?
- 9.4 Can CSP generate electricity at night?
- 9.5 Where are the world’s largest CSP plants?
- 9.6 Is CSP more efficient than solar PV?
- 9.7 What is molten salt storage in CSP?
- 9.8 Should I install CSP or solar PV on my property?
- 10 Summing Up
Key Takeaways
- Concentrated solar power (CSP) uses mirrors or lenses to concentrate direct sunlight onto a receiver, generating heat to drive a turbine and produce electricity.
- CSP requires high levels of Direct Normal Irradiance (DNI), the intensity of direct beam sunlight, which the UK does not receive in sufficient quantities for viable CSP operation.
- The world’s largest CSP plants are located in Spain, the USA (Mojave Desert), Morocco, the UAE, and South Africa, all in high-DNI, high-sunshine climates.
- CSP’s key advantage over solar PV is thermal storage: heat can be stored in molten salt and used to generate electricity at night or during periods of low sunlight.
- For UK homeowners and businesses, solar photovoltaic (PV) panels are the relevant solar technology, not CSP.
How Does Concentrated Solar Power Work?
All CSP systems share the same fundamental principle: concentrate sunlight to generate heat, use that heat to produce steam, and drive a turbine to generate electricity. Where they differ is in the optical design used to concentrate the sunlight and the configuration of the receiver and heat transfer system.
The concentration ratio, how many times more intense the focused light is compared to ambient sunlight, determines the temperature achievable in the receiver. Higher temperatures mean higher thermodynamic efficiency but require more precise optical alignment and more advanced materials engineering. The operating temperatures of commercial CSP systems range from around 400°C in simpler designs to over 1,000°C in experimental concentrating dish-Stirling systems.
Types of CSP Technology
Parabolic Trough
The most commercially mature and widely deployed CSP technology. Long parabolic mirror troughs focus sunlight onto a receiver tube running along the focal line. A heat transfer fluid (typically synthetic oil) circulates through the receiver tubes, reaching temperatures of 290 to 400°C. This heated fluid passes through a heat exchanger to generate steam, which drives a conventional turbine-generator. Parabolic trough plants are modular, well-understood, and have been operating commercially since the 1980s in California.
Solar Power Tower (Central Receiver)
A large field of individually tracking flat mirrors (heliostats) focuses sunlight onto a receiver at the top of a central tower. The receiver achieves much higher temperatures, typically 500 to 600°C, and up to 1,000°C in some advanced designs, which enables higher electrical efficiency. The Ivanpah Solar Electric Generating System in California (392MW) and the Noor Ouarzazate complex in Morocco use power tower configurations. Molten salt is used as both the heat transfer medium and the thermal storage medium in the most advanced designs, enabling 6 to 15 hours of electrical generation without sunlight.
Fresnel Reflectors
A simpler, lower-cost variant of the parabolic trough concept. Flat or slightly curved mirror strips focus sunlight onto a fixed receiver above the mirror array. The mirrors are mounted at ground level, reducing wind loading and structural costs. Performance is somewhat lower than parabolic troughs but the capital cost is significantly lower. Linear Fresnel plants are typically used for lower-temperature applications or as a cost-driven alternative to troughs in simpler projects.
Dish-Stirling Systems
A parabolic dish tracks the sun on two axes and focuses sunlight onto a Stirling engine at the focal point. Stirling engines convert heat directly into mechanical motion without requiring steam, making them highly efficient at small scales. Dish-Stirling systems achieve very high concentration ratios and electrical efficiencies, but have not been commercially deployed at utility scale. They are primarily a research and demonstration technology.
The Thermal Storage Advantage
CSP’s most important advantage over solar PV is dispatchability, the ability to generate electricity when it’s needed, not just when the sun is shining. By storing heat in molten salt tanks (which retain heat at around 565°C with relatively low losses), CSP plants with thermal storage can continue generating electricity for 6 to 15 hours after sunset. This allows CSP to operate as a firm, schedulable power source rather than an intermittent one.
This characteristic makes CSP particularly valuable in electricity systems where reliability is critical and where the solar resource is strongest when demand is also highest, as in the US Southwest and the Middle East, where air conditioning loads peak during the hottest, sunniest hours. The thermal storage advantage justifies the significantly higher capital cost of CSP compared to solar PV for these applications.
Why CSP Doesn’t Work in the UK
CSP requires Direct Normal Irradiance (DNI), the intensity of direct beam sunlight, measured on a surface always perpendicular to the sun. Diffuse sky light (the light on an overcast day that illuminates everything evenly) is essentially useless for CSP because it cannot be focused by mirrors. Concentrating optics only work with direct beam radiation.
The UK receives very low DNI compared to the regions where CSP is commercially viable. Spain, Morocco, California, Arizona, the UAE, and South Africa all receive annual DNI of 1,800 to 2,800 kWh/m² or more. The UK receives annual DNI of roughly 800 to 1,000 kWh/m² in the south of England, and less in the north. This is simply insufficient to make CSP economically viable, the mirrors would spend too much of the year in diffuse light conditions where they produce no output.
Solar PV, by contrast, works effectively in both direct and diffuse light. UK-grade solar resource, even on Scotland’s overcast days, is perfectly adequate for generating useful electricity from PV panels. This is why the UK has over 17GW of installed solar PV capacity and no commercial CSP plants.
CSP vs Solar PV: A Comparison
| Feature | CSP | Solar PV |
|---|---|---|
| Works in diffuse light? | No, direct sunlight only | Yes, works in diffuse light |
| Thermal storage? | Yes, molten salt storage | No (electrical batteries needed) |
| Suitable for UK? | No | Yes |
| Scale | Utility scale only (50MW+) | Any scale (1kW to hundreds of MW) |
| Technology maturity | Commercial (in suitable climates) | Fully commercial globally |
| Cost trend | Declining, but higher than PV | Strongly declining, very competitive |
Where CSP Is Being Deployed
The world’s leading CSP markets are Spain (the first major commercial CSP market), the USA (particularly California and Nevada), Morocco (the Noor Ouarzazate complex is one of the world’s largest solar power plants at over 580MW), the UAE (the Mohammed bin Rashid Al Maktoum Solar Park includes significant CSP capacity), and South Africa. All of these locations combine high DNI, political will to decarbonise power generation, and electricity systems that value dispatchable generation.
Chile’s Atacama Desert is the latest major CSP frontier, with extremely high DNI and significant co-location potential with copper mining operations that require reliable power and steam. China has also invested heavily in CSP demonstration projects, though solar PV has dominated Chinese solar deployment due to its lower cost.
Expert Insights From Our Solar Panel Installers
One of our senior solar panel installers with over 17 years of experience in domestic and commercial solar PV commented: “We get asked about concentrated solar occasionally, usually by people who’ve read about the big plants in Morocco or California and wonder if something similar could work here. The short answer is no, CSP needs the kind of clear, intense sun you get in deserts, not the British climate. For UK energy, photovoltaic panels are the technology. They’ve gotten dramatically cheaper, they work on every type of property, and they make excellent financial sense. CSP is a fascinating technology for the world’s sunniest regions, but it’s not relevant to a UK solar installation.”
Frequently Asked Questions
What is concentrated solar power?
Concentrated solar power (CSP) is a technology that uses mirrors or lenses to focus direct sunlight onto a receiver, generating high-temperature heat to drive a turbine and produce electricity. It is a utility-scale technology requiring large land areas and high levels of direct sunlight, making it unsuitable for the UK climate or for domestic installation.
Why can’t CSP work in the UK?
CSP requires direct beam sunlight that can be focused by mirrors. The UK has too much cloud cover and diffuse light, the annual Direct Normal Irradiance in the UK (800–1,000 kWh/m²) is roughly half what’s needed for viable CSP operation. In contrast, solar PV works effectively in both direct and diffuse light, which is why PV is the appropriate solar technology for UK conditions.
What are the main types of CSP technology?
The main commercial CSP technologies are parabolic trough (the most widely deployed), solar power tower or central receiver (the highest efficiency), and linear Fresnel reflectors (simpler and lower cost). Dish-Stirling systems exist at demonstration scale. All focus direct sunlight onto a heat receiver to generate steam for electricity production.
Can CSP generate electricity at night?
Yes, this is CSP’s key advantage over solar PV. By storing heat in molten salt tanks at around 565°C, CSP plants with thermal storage can continue generating electricity for 6 to 15 hours after sunset. This dispatchability makes CSP valuable as a firm, schedulable power source in electricity systems that need reliable generation beyond daylight hours.
Where are the world’s largest CSP plants?
Major CSP installations include the Noor Ouarzazate complex in Morocco (580MW+), the Ivanpah plant in California (392MW), and the Mohammed bin Rashid Al Maktoum Solar Park in the UAE. Spain remains the largest single-country CSP market by installed capacity. All are located in high-sunshine, high-DNI regions where the technology is commercially viable.
Is CSP more efficient than solar PV?
CSP can achieve higher thermodynamic efficiency than standard solar PV, modern CSP power towers convert 15 to 20% of incident direct solar radiation to electricity, comparable to PV. However, because CSP can only use direct beam radiation and PV can use both direct and diffuse light, PV generates significantly more energy per year in most locations outside sun-belt regions. In the UK, PV outperforms CSP decisively because of the UK’s diffuse-heavy solar resource.
What is molten salt storage in CSP?
Molten salt thermal storage is the most common method of storing energy in CSP plants. A mixture of sodium and potassium nitrates is heated to around 565°C during the day using the solar heat collected. The hot salt is held in insulated tanks and drawn upon to generate steam for electricity production whenever needed, day or night. Molten salt holds heat with relatively low losses for 6 to 24 hours, enabling truly dispatchable solar power generation.
Should I install CSP or solar PV on my property?
For any UK property, solar PV is the appropriate choice. CSP is a utility-scale technology requiring large land areas, specialised engineering, and high direct sunlight, none of which apply to domestic or commercial rooftop solar in the UK. Solar PV panels are well-suited to UK conditions, available at any scale from 2kW domestic to multi-megawatt commercial, and provide excellent financial returns through self-consumption savings and Smart Export Guarantee income.
Summing Up
Concentrated solar power is a genuinely impressive technology that has demonstrated its value in the world’s sunniest regions, delivering firm, dispatchable electricity that can run through the night using thermal storage. But it’s fundamentally not a technology for the UK: the country’s diffuse, frequently overcast solar resource falls well short of what CSP requires. For UK homeowners and businesses, solar photovoltaic panels remain the right technology, effective in UK conditions, available at any scale, and delivering strong financial returns through electricity bill savings and Smart Export Guarantee income. If you’re considering solar for your property, our team can provide a free, no-obligation quote for an MCS-certified installation.
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