Solar panel technology has advanced a great deal in the last decade to make them much more efficient, higher powered and much nicer to look at.
The science behind them has been the same since they were first invented, we’ve just tweaked it to get the very best from the materials used.
We’ll take a look at what’s in a panel, and how they are built.
What are solar panels made of?
Solar Panels are made up of Solar Cells and, more often now, Solar Half cells.
But, more about that later, first let’s take a look at the construction of a Solar Cell.
What is the process of making Solar Panels?
The first and most important material used in solar panels is silicon. The problem with silicon is, it needs to be extracted from quartz. Quartz is a silicon dioxide and can be found, naturally, as either gravel or stones which are then crushed.
Quartz is also very abundant in sand, but the cost of extracting it is prohibitive.
So, the quartz is mined then the resulting rocks and gravel are heated to extreme temperatures while a carbon arc is added to the furnace. The carbon bonds with the oxygen to create carbon dioxide and all that is left is molten silicon.
Boron is added to the melton to give it a positive electrical charge.
The silicon isn’t 100% pure at this stage so the ingot is passed through a heat source, the same way, several times. This forces all the impurities to one end of the ingot which is then removed.
Single Crystal Silicon
The next stage of the process is making the silicon into boules so it can be easily cut to create wafers.
The making of a boule is achieved using something called the Czochralski method.
A seed crystal of silicon is lowered into melted polycrystalline silicon, then withdrawn slowly and rotated. This makes a cylindrical ingot or boule.
All impurities are left in the liquid so the ingot is now 100% pure and is ready for the next stage.
As covering your roof in silicon ingots isn’t going to get the heating powered so the cylinders sliced, sausage style, into paper-thin discs.
There are certain companies that cut the wafers in a hexagonal shape so the cells all fit together nicely and cover a whole area – this causes a lot of waste though, so the process makes the resulting PV panels much more expensive.
Pure silicon is shiny which makes it reflective so, to counteract this, a non-reflective film can be added to the wafer at this stage.
It is also thought that the rough edges, from the saw used to cut the ingot, actually help the cell to absorb light much more efficiently.
Now we have our little magic wafers, we need to make sure they can turn all that lovely sunlight into electricity.
The wafers are put into a really hot oven-like device and bombarded with phosphorus. This forms a layer on top of the silicon that is negatively charged.
Meaning the wafer will have a potential difference when hit with protons (from sunlight) and current will flow from the negative phosphorus towards the positive silicon/boron.
Each cell is then fitted with conductive wires to move the electricity away from the cell and into your home.
From many cells to one panel
One solar cell isn’t going to get the washing done, so the cells are connected together with conductive wires in a matrix type configuration.
Panels traditionally came in 48, 60 and 72 cell variations but as we learn more about how solar power works we are starting to see a new kind of panel that uses split cells.
These are called Half Cell panels and they are more efficient than their older cousins. When the cell, or crystal, is split in half it means the electricity has less distance to travel to get out – in clever talk this is called lowering the resistance. 104 Half Cell Panels have an efficiency rating of up to 24%.
Once the cells are all connected they are covered with a sheet of glass about 6mm thick and the back of the matrix is covered with a highly durable, polymer sheet.
Once these steps are complete the whole shebang is put into the frame… now it looks like a Solar Panel and is ready for testing.
Testing a solar panel
All panels should be tested using the STC (Standard Test Conditions) – which is the equivalent of 1000W/m2 irradiance, 25°C cell temperature and an air mass of 1.5g.
The output is measured to ensure it meets the specifications and you can see all that data on your technical specification sheet.
Of course, we don’t often see those conditions on every roof in the world so the panels are also put through a NOCT (nominal operating cell temperature) test, which is much more like a real life installation – 800W/m2 irradiance, 20°C ambient temperature, 1m/s wind speed.
You can see all this on the tech spec sheet too.
What types of solar panels are there?
There are 3 types of solar panels on the market – monocrystalline, polycrystalline and thin film.
Thin film panels are very flexible but also very expensive. They can be shaped and curved to fit round contours on buildings.
Polycrystalline are silicon crystal panels but the crystals are fused together to catch as much sun as possible – that makes them fairly cheap to produce but not very efficient.
Monocrystalline panels are the ones you’ll see on people’s roofs. They are more expensive to make but the fact they are the most efficient panel available to most homeowners, they are very cost-effective.
Solar panel efficiency
Here’s a quick guide to solar panel efficiency:
|Type of Panel
|13% to 16%
|7% – 18%
How ‘green’ are Solar Panels in reality?
While silicon and some of the other materials used to make solar panels are not easy to mine, produce or work with, there is a definite carbon footprint to the production of solar panels. In fact, it’s estimated to be about 50g.
That’s not perfect but as a solar power system produces zero carbon while they are being used, the panels will become carbon neutral 5 years into their 25 lifetime.
Recycling Solar Panels
The other worry can be disposal but, as they consist of silicon, aluminium and plastic, they are completely recyclable.
As solar power has increased in popularity over the last decade, more and more panel recycling companies are starting to appear.
In 25 years all panels will be more efficient, smaller and completely recyclable.
And, we would hope, there will be more ways to recycle the panels we are installing today.
Learn more about solar panel recycling.