Solar panels can convert light into two main forms of energy: electricity and heat. This article is focused on the electricity-generating solar panels known as solar PV.
A solar PV’s efficiency (how effectively it converts light into electricity) is determined by how the solar cell is put together, specifically the structure of the semiconductor silicon. Commercial solar cells are typically 10 – 25% efficient. This means they can convert ⅙ to ¼ of the light that hits the solar panel into electricity.
Types of Solar PV
The two main types of solar cell are monocrystalline and polycrystalline.
- Monocrystalline cells comprise one unbroken silicon crystal. These cells are more efficient than polycrystalline cells (sometimes up to 25% efficient), but they’re also more expensive.
- In Polycrystalline cells, many smaller silicon crystals are melted and cooled into shape, giving the solar panel a flake-like appearance. These solar cells are less efficient (roughly 12-18%), but they’re cheaper to make and there’s no silicon wasted in the process.
Both types of solar cell have their uses. For instance, monocrystalline solar panels are better for houses with smaller roofs, since they have a greater output-to-surface area ratio. Polycrystalline panels are generally more cost-effective on larger roofs.
Other types include solar tiles, thin film and solar glass. Most of this technology is still in its infancy, and it may take a few more years before they can compete with mono and poly solar panels.
Choosing a solar panel
When comparing solar panels, remember to take the model’s power rating (e.g. ‘300 Wp Mono Solar Panel’) with a pinch of salt. These Watt peak values (Wp) can be misleading, as they only show how much electricity can be generated in peak conditions. Also, the high power rating might be down to the size of the solar panel, not necessarily because the technology is more advanced.
The efficiency (given as a percentage) is probably the best criteria to look out for. You can also look at customer reviews and reports of your model online.
The most efficient solar panels still only have a maximum efficiency of under 50%. In spite of this, if we covered just 1% of the Sahara desert with solar panels working at 20% efficiency, we would generate enough electricity to supply the whole world with clean free power.