Solar power on a large scale
Parallel to the use of photovoltaic panels for domestic consumption for local generation, solar parks are being developed around the world with a view to establishing centralised power production. Various technologies are available for this.
The most widespread method of generating electricity from the sun is to use photovoltaic panels. These panels are now also being deployed in photovoltaic power plants, which are also known as solar parks.
These power stations are composed of hundreds, thousands, or even more than 100,000 panels placed side by side. The technology is the same as for a domestic installation, only massively scaled up.
Solar parks composed of bifacial solar modules
Photovoltaic technology has two advantages: it’s modular and also works in diffuse light. This makes it possible to build a 10-15 MW photovoltaic plant in Europe, or a plant generating 150 to 500 MW in countries with large available open spaces and a very high level of sunshine.
“The yield of conventional photovoltaic technology will definitely go up in the future as production costs come down, and this will boost the use of photovoltaic technologies”, said Philippe Buxant, director of ENGIE’s Corporate Renewable Energy programme. “I also think that the bifacial modules, which are currently undergoing their test phase, will be used extensively in solar parks, because they can capture and convert light reflected by the ground. In short, they’ll undoubtedly increase the capacity of photovoltaic parks.”
Solar concentration plants
Solar power plants also exploit a second technology that uses concentrated solar thermal energy.
What does this involve? Thousands of mirrors concentrate direct sunlight onto a single point (or along a single line). The result? A massive concentration of heat, up to 1,000 times hotter than natural sunlight. Unconcentrated solar heat can generate 1,000 watts per m², as is the case for a solar-powered water heater. Using solar mirrors increases this to 1 MW per m².
These high temperatures, reaching several hundred degrees, can be exploited for power generation, among other things. The resulting heat is used to produce steam that drives a turbine, which in turn generates electricity, just like in a conventional power plant. But it can also be used directly in industrial processes.
Heat that’s easy to store
The great advantage of concentrated solar energy is that the resulting heat is easy to store. “Photovoltaic technology generates energy immediately, which must then be injected into the grid straight away”, Philippe Buxant explains. “Storing electricity in batteries is still expensive and rarely economically viable. On the other hand, heat can easily be stored in various forms: as molten salt, concrete, ceramics or steam.”
In California, a number of solar concentration plants have been in operation since the 1980s. Together, they generate peak power totalling 350 MW. Today, concentrated solar energy generates just under 5 gigawatts (GW) of electricity in about 10 different countries. However, concentrated solar energy will undoubtedly remain a niche technology.
In addition to generating power, concentrated solar energy is also used for other applications, such as enhanced oil recovery. In this context, the vapour produced by the solar mirrors is injected into a borehole to extract the deep layers of more viscous oil. The vapour fluidifies the oil, making it easier to extract. A first enhanced oil recovery facility built in the Sultanate of Oman generates 1 GW of thermal energy with around 3 km² of mirrors.
Another application being looked at more and more is steam production for industrial use. The steam in question, whose temperature ranges between 150 and 300°C, can be used in the food industry or in flour mills, breweries and dairies. Many opportunities remain to be explored In this domain.
Read also: Look for the sun where it shines the most.