How do solar panels work

South Africa has an almost constant supply of heat and light energy which makes solar energy as an investment as a wise choice. Solar energy offers great return on investment with increased energy costs, and decreased free spending money, solar energy becomes an investment rather than a liability.


What is the difference between off-grid and on-grid solar energy?

On-grid means that you are still connected to the municipal power for when the solar power is not available. Using off-grid solar power means the system is not connected to the municipal power supply and needs a back-up battery to supply solar power for your needs during nights or overcast days where clouds are too dense for the sun to penetrate.

The sun produces a lot of solar energy, 10 000x more power than the world’s population uses resulting in solar energy radically being installed more in the last two decades, using a freely available resource, abundant in Southern Africa and accessible.

The solar energy is stored inside photovoltaic panels, using solar cells and can be linked to batteries, or be a grid-tie solution.


Advantages of being on-grid:

  • There is energy supply during the solar panel down time
  • Battery back-up is not needed with stored electricity


Advantages of being off-grid:

  • Not affected by municipal fluctuations in electricity supply
  • Save money in the long-term, and save the environment by using a sustainable resource.
  • You have access to electricity.


What is a grid-tie inverter?

A grid tie inverter converts the DC power from the solar energy system to AC power, which is used for the home or office power supply.


What does a solar panel work?

A solar panel, also known as a PV panel, collects energy from the sun energy and converts it into electrical energy or electrical current. Solar panels are made up of solar cells.

To create a solar panel, the base product sand is needed which contains silicone.

Sand is converted to silicone crystals to be used in solar cells, silicone as a semi-conductor, one of the most abundant resources on earth goes through purification where the raw silicone converted in gaseous silicone form, mixed with hydrogen forming a highly purified polified crystalline which are then used to create silicone wafers.

In the polified crystalline, the silicone atoms are bonded, with electrons available, but no free movements due to being bonded.

Crystalline silicone is placed between conductive layers

Electrons are kept together by 4 strong bonds inside the PV panel

A solar cell is made of of 2 different layers of silicone, where the N-type layer has extra electrons

P-type silicone has extra spaces called holes. Where they meet, there is an area called a PN junction. Here electrons can move between the PN junction in any direction. Random movement of electrons does not create current as the electrons need to be going in a uni-directional flow. By in having more holes on one silicone layer, and more electrons on the other silicone layer, this causes the electrons to flow uni-directionally.


Creating electron flow from sunlight:

Sunlight hits the solar cells. Sunlight is made up of photons which are tiny particles of sunlight. The photons can activate the electron, and with enough energy to create a “hole” and move the electron.

The electron follows the directional created by the PN junction, which causes the electrons to go only one way as there are more electron ons one side, and more holes on the other. By trying to balance this out, the electrons start to move ie Electron migration causes positive and negative charge in the silicone panel, causing electrons to move in a unidirectional way.

A bigger junction region (depletion zone) – means more current flow.

Electrons start migrating and with the differences in potential, start moving in the same direction, ie uni-directionally.

Electron moves towards N, while the hole goes towards P. Electrons, are now moving, are collected at the top of the cell by thin metal fingers and then through an electric circuit. In the circuit, the electrons create electrical energy to make things work eg a light bulb. They then go through the conductive sheath at the back, back into the PV panel circuit.

Solar panels are made up of layers made up of cells. They are connected front to back in a series connection.


How much energy does a single solar cell generate?

A silicone cell puts out half a volt, with 12 cells can power a cell phone. Only the electrons move created energy, and they keep moving back in the circuit giving the solar cells a long life span.


General points on solar panels:

  • Each solar cell can produce 50 volts

  • Cells connected in parallel to increase the current into a usable range

  • EVA sheeting protects the solar panels against shock, humidity, dirt, vibrations

  • Solar panels might have different colour – why?

  • The two appearances differ between blue and grey and have to do with mono-crystalline and poly-crystalline structure of the panels. On the internal crystalline lattice structures. Poly-crystalline silicon is randomly orientated whereas mono-crystalline is when the step is taken one level further. Mono-crystalline lattice structures provide more energy with higher electrical conductivity, but are a lot more expensive.

  • Storage of solar energy is done using lithium batteries and solar charge controllers.