Thousands of mirrors arranged neatly in concentric circles mirror a massive concrete pillar rising 195 meters (640 ft) above the desert sand.
Not far from Las Vegas, the Crescent Dunes Solar Power Plant looks like something out of a sci-fi movie. But it’s actually a real-world billion-dollar megaproject, completed in 2015 with the goal of powering 75,000 homes.
Additionally, it was considered a breakthrough symbol for a particular type of solar technology known as concentrated solar power or CSP for short.
The project followed in the footsteps of the first large-scale CSP plant built in California in 1981 – when the technology was more promising than photovoltaics (PV), which were expensive and really only used in space travel.
But it did not live up to expectations. Crescent Dunes failed to produce as much electricity as promised, and after repeated technical failures and prolonged outages, the plant was closed in 2019. And far from paving the way for a wave of other CSP projects, it damaged the technology’s image.
These days, there are about 7 gigawatts worth of CSP plants around the world, mainly in Spain or older US sites, and a few other places with lots of direct sunlight, such as Chile, Morocco and the United Arab Emirates. Meanwhile, installed global photovoltaics capacity now exceeds 2,000 gigawatts.
How does CSP work and does it still exist?
Five years later, the original Crescent Dunes plant is back to generating small amounts of electricity. And while the US has not built a single large plant since the Nevada venture, China has. In fact, not just one, but 30.
Some people say that this means that CSP is ready to make a comeback and it is all because of a special feature that sets it apart from normal solar panels.
The regular types of solar panels installed on rooftops around the world use the photovoltaic effect to produce electricity, meaning that when the sun’s rays strike their surface, the photons in them destroy loose electrons that They start moving, due to which a current is generated.
CSP plants, on the other hand, use the sun’s heat. So-called heliostats – which are essentially mirrors – reflect the Sun’s rays and concentrate them at a fixed point. The bundled heat is then used to create steam, which rotates a turbine to create electricity.
“It’s the same child [of turbine] “This is what you would have in a typical fossil energy plant – but without burning any fossil fuels,” mechanical engineer Javier Lara, who has worked on several CSP projects around the world, told DW.
There are different designs to do this, the most iconic of which are arguably solar power towers, like the one at Crescent Dunes.
The mirrors reflect sunlight onto a receiver at the top of the tower. Inside this receiver, a liquid is heated – usually molten salt because it is particularly good at retaining heat. The heated salt is then pumped into the turbine, and once it has done its work there and cooled, it is pumped back to the tower, and the cycle starts again.
Why did CSP lose the technology race?
“Semiconductor technology has become really cheap, and photovoltaics have become very cheap,” Jenny Chase, solar analyst at energy research firm BloombergNEF, told DW.
2011 was the first year that photovoltaics were cheaper than CSP, and this trend has continued. Since 2010, the price of PV solar power has fallen by approximately 90% overall and now costs less than half that of rival technology.
One reason for this is that solar panels are flexible and easy to install, whereas CSP plants are usually custom-built feats of engineering.
Furthermore, photovoltaic solar panels are very easy to maintain.
“It’s just sitting there, and you have to clean it from time to time,” says Richard Thoenig, a researcher focusing on CSP. “But it’s not as operationally complex as CSP where you have mirrors that you have to clean in the actual environmental environment.” Need to adjust to circumstances.” The German Research Center for Geosciences told DW.
https://www.youtube.com/watch?v=v=v_kgre8h57I
Tracking the sun’s movement requires painstakingly adjusting the entire mirror area so that light is accurately reflected. This makes it possible to control the temperature of the liquid circulating through the system.
Clouds covering the sun can make this process difficult, but it is important to get it right.
“Working with molten salt is troublesome because if something goes wrong and it drops below its melting point, you don’t have molten salt, you have solid salt. And then your pipes fill with solid salt. “It’s a big pain point to solve,” Chase said.
A new place for CSP
But despite all this, CSP has one big advantage over photovoltaics: it can generate electricity at night.
New plants usually have large insulated tanks where hot molten salt can be stored. Inside, it cools by only 1 °C (1.8 °F) per day, so it can be used later to generate steam.
For example, when the sun has gone down or when the power requirement has increased due to many people using it at the same time.
This ability to store energy and convert it into electricity around the clock could give CSPs a new edge.
“The future of CSP has reached a different place, right? So it used to be a power technology, like wind and PV, and now it’s really a storage technology,” Thonig said.
This is also the reason behind its sudden popularity in China. In many provinces, there are now rules that every new renewable energy park with a capacity of more than 1 gigawatt must include at least 10% storage.
The Chinese government also issued a notice saying it would support “large-scale and industrial development of solar thermal energy”.
The idea is simple: to get the best of both worlds. During the day, photovoltaic solar panels supply cheap electricity, while the CSP plant heats the molten salt. At night, when solar panels cannot produce electricity, the heat stored in CSP plants can be used to provide electricity.
Bridging this nighttime gap has been a major challenge for renewable energy, and CSP, along with other technologies like batteries, can be part of the solution.
Pressure from China could set CSPs back somewhat, as the country is building dedicated supply chains that could drive down prices for building new plants.
But to really advance the technology, other countries will have to get involved and create policies to support it.
“I wouldn’t say we’ve really had a big CSP renaissance,” Thonig said. “But I would say the technology still exists and is still promising. There is a case for CSP in many places and – with the right structural conditions – it can be very attractive and very cheap.”
Edited by: Tamsin Walker
