Solar panels are made from photovoltaic cells, which harness the Sun’s energy and convert it to electrical energy.
In MegaWatt, the solar technology card is a low cost and low environmental impact option. Its weakness is a low power density due to the large amount of area required, and that it can only produce electricity during the day.
Solar panels can be found everywhere as they are scalable, powering calculators all the way up to thousands of homes. On cloudy days, solar panels can still generate electricity, although it is a lot less than on a sunny day. Countries nearer the equator are better suited for solar energy, as the solar intensity is higher (the Sun's rays are at their most intense). They release no emissions while they generate electricity, although as with wind, they require a lot of natural resources to be built at scale (such as glass and metal for the frames, and silicon for the photovoltaic cells). Since they have no moving parts they are relatively easy to maintain, and have a typical lifespan of over 20 years.
Now for some stats from the UK grid in 2019.
Solar provided 12.9 TWh of energy, around 4% of the UK's total electricity generation. While solar has a similar level of installed capacity to onshore wind (around 13,000 MW), its capacity factor is very low at around 11%. This means that it produced less electricity over the course of the year than onshore wind did. In the UK, solar farms have low capacity factors due to a low number of sunny days, as well as low solar intensity due to the UK being far from the Earth's equator. The de-rated capacity, which accounts for this intermittency, was 2,269 MW.
Solar energy is projected to steadily grow in the UK, at an increase of around 4% a year. This is due to a combination of small-scale solar systems such as rooftop solar, as well as large-scale systems. The largest planned solar farm can be found at Cleve Hill, Kent. When completed, this solar farm will have 350 MW of installed capacity with over 900 acres of solar panels.
In areas with really high solar energy, a more efficient way of using this energy can be achieved using concentrated solar power plants. These use mirrors or lenses to concentrate a large area of sunlight to a receiver such as a pipe or tower. This creates really high temperatures and this heat can be converted into electricity for use on the grid, in a similar way to how power stations like gas or nuclear convert heat to electricity. Some designs utilise thermal storage as a kind of battery and generate electricity even at night! This is still a developing technology but as prices drop and efficiencies increase, we may one day see these solar plants in deserts all around the world.
There have been proposals for some mega engineering projects to use solar energy to power the world. How? By covering deserts with solar panels and transmitting all the energy to where it is needed! One such proposal called Desertec involved covering the Sahara desert in Africa with solar panels and using the energy to power Europe using massive undersea electricity cables connecting North Africa to Italy, Spain and Greece.
The Sahara desert is the sunniest year-round area in the world with the highest amount of solar energy available. As it is a desert, the land is of low value and is hardly used by humans or animals. With just a fraction of the Sahara covered in solar panels, there would be enough energy generated to power the whole of Europe. The Desertec project is still just an idea at the moment, but several other projects are under development to transmit desert solar energy to Europe, such as the TuNur project in Tunisia or the Noor Complex Solar Power Plant in Morocco which also aims to export energy to Europe.
If you want to learn more, here are some examples of solar power plants around the world.
Westmill Solar Park in Swindon covers 30 acres with 20,000 solar panels. These have an installed capacity of 5 MW which can generate around 4.8 GWh of electrical energy per year. It is community owned, meaning that is it controlled and owned by locals who decide on how the solar farm is operated.
The Kurnool Ultra Mega Solar Park in India is the largest solar power station in the world, and is made up of 4 million (🤯) solar panels. Together, they have a capacity of 1000 MW. It is so big that it can be seen from space, with a total area of over 3400 football fields!
All of the numbers we used for the UK statistics can be found in the Digest of United Kingdom Energy Statistics 2020 which is from the Department for Business, Energy & Industrial Strategy (the people in government who look after our energy policy). The 2019 UK grid capacity is based on the de-rated capacity, which includes a capacity factor to adjust the value for comparison to firm power sources.