How Does a Solar Power Plant Work?

According to our solar panel expert, energy costs in the UK are predicted to double within the next decade. “With nuclear proving to be cost prohibitive and fossil fuels clearly not being the answer, there will need to be significant commercial and business investment in grid scale renewable generation”. But what does a massive, grid-scale solar power system look like?

Commercial solar panel systems are the darling of renewable energy and a favourite amongst businesses that want to save money whilst boosting their environmental credentials. But as a large-scale energy solution, solar technology depends on some impressive feats of engineering. Solar power plants are more complex than they first appear – here’s a brief guide to how they work.

What is a solar power plant?

Basically, any facility that uses large-scale photovoltaic (PV) technology to convert solar energy into electricity is a solar power plant, although some plants do convert sunlight into heat and not light, as is the case with solar thermal plants. Large numbers of PV cells made from silicon alloys are assembled in an array to capture daylight.

Not all solar panels are created equal, however. There are three main types:

Monocrystalline – more efficient (rating of around 20%) but more expensive panels, these dark black units are made with single-crystal silicon, hence their name.

Polycrystalline – less efficient (rating of around 15%) but more affordable, these blue-black panels are slightly bulkier but more popular.

Thin-film solar panels – thin and flexible, these sheets are integrated into industrial buildings or roofing. Lightweight and easier to manufacture, they unfortunately have a shorter lifespan.

How does a solar power plant work?

Whichever type of panel is in use, a solar power plant usually works on the same basic principles.

Solar panels capture and convert radiant energy from the sun. Because PV cells are made of semiconductor materials (usually silicon) they contain easily excitable electrons that, after absorbing solar energy, are then free to flow as a direct current (DC) with voltages up to 1500V. This process of converting photons into usable electrical energy is called the photoelectric effect.

The flow is then converted to AC (alternating current) by an invertor, before being stored in a battery or else channeled into the electricity grid. The electricity can then be concentrated or processed through a series of transformers before being sent out to power appliances and so on.

Solar power thermal plants

When we imagine solar panels, we usually think of the solar PV cells described above, increasingly seen on the roofs of homes and businesses everywhere. But solar thermal plants capture solar radiation which is then used to create steam that indirectly generates electricity, rather than directly, as does solar PV technology. Solar PV panels work by using either linear collectors, parabolic trough collectors, or solar dishes.

Parabolic troughs are parabola shaped (gently curved) panels that focus the sun’s rays onto a collector, and they can move to track the position of the sun. The concentrated light heats a fluid which is collected centrally and then used to boil water in a steam turbine, which generates the electricity.

Linear concentration plants consist of a field of mirrors that tilt to follow the sun, maximizing how much light they capture. While also parabolic in shape, they have a receiver tube installed above the mirrors, so that the panels can move more freely.

Finally, solar dishes also use mirrors to concentrate the sun’s rays, but are shaped like bowls or lenses covered internally with many tiny mirrors that direct sunlight to a focal point. This receiver then transfers energy to an engine, which moves pistons that convert solar heat into mechanical energy, and later electrical energy. Plants that work on this principle are also called Fresnel reflector power plants.

Unconventional solar power plants

All solar power plants ultimately convert the sun’s radiant energy into another, more useful form. There are now other interesting ways of doing this, for example solar power towers, which concentrate the solar energy they reflect onto a central tower, concentrating it by up to 1500 times. This energy then heats up air inside the tower to a whopping 700 degrees Celsius, which is funneled through a steam turbine that then produces electricity. Some towers alternatively use superheated water to transfer the stored solar energy.

Finally, solar ponds are saltwater pools that act, in a way, like solar panels, since they trap thermal energy from the sun’s rays. By exploiting the gradients in salinity (i.e. there is a higher salt concentration at the bottom of the pond), the captured heat is stored in the lower parts of the pool to be used later. Again, the heated water is then used either to generate electricity or supply thermal energy directly. 

There are many ingenious ways to harness the raw energy from the sun and convert it to useful electricity or heat, beyond what most people think of when they hear the term “solar power.” Solar power technology is an exciting and rapidly developing field which promises to create ever more efficient, creative and environmentally friendly solutions in our eternal quest for clean energy.