Curiosity about Solar Energy

Solar Energy is energy which the sun radiates and reaches the earth. Solar Energy is a renewable energy.

There are two energy sources; Renewable energy and Non-renewable energy. Renewable energy are energy sources that occur naturally and continuously in the environment. Apart from Solar Energy, Wind, Hydro, Biomass are also examples of renewable energy sources. Non-renewable energy are energy source that cannot be made again in a short period of time. Examples include; fossil fuels, nuclear energy.

Solar Energy has two types of use:

1. Solar Heating; the heating effect of the sun is used to dry crops, bricks etc.
2. Solar electricity (use of electricity from solar energy). Solar energy is converted to electricity by either using Photovoltaic devices or Solar power plants.

Solar Power Plants. These indirectly generate electricity. They employ solar thermal collectors to collect heat from sunlight and this heat is used to heat the fluid which produces steam that is used to power a generator (turning turbine). This heat can also be put to other uses like in steam baths.

Photovoltaic devices. These change sunlight directly into electricity. Photovoltaic devices/cells make up a Solar Panel.

How do Solar Panels generate electricity?
A Silicon Solar Panel/module (also known as a Photovoltaic module) generates electricity when photons from sun excite electrons in it.
Let's first go through the construction  of a solar cell. Solar panels are made up of solar cells. Like semiconductor electronics such as diodes and transistors, silicon solar cells are doped that is to say some impurity atoms are added to the silicon crystals to form negative (n-type) crystal and positive (p-type) crystal. The n-type doping can be Phosphorus atoms added to silicon. Silicon atoms offer each other one electron in a covalent bond so this makes silicon unable to conduct electricity. But if a phosphorus atom is added, it will behave like silicon with a extra electron.

When a photon from sun strikes this electron, it gets excited (it becomes delocalized).

P-type doping can be Boron atoms added to silicon. Boron atoms have three valence electrons, each, to offer to silicon in a covalent bond and this will create a need for one more electron. Therefore a hole is created.

So in a silicon solar cell the two doped materials, made into plates, are joined together with a junction in between. In full sunlight; when you create an external circuit by attaching wires to the p-type and n-type doped materials, Boron in the P-type doping will create a positive potential to attract the excited electron in the n-type doping.
In a silicon solar panel, cells are connected to each other in series. A typical solar panel has:

• 33 cells in series
• the maximum useful voltage generated by a solar cell is about 0.58 volts dc.
• the total output voltage of the panel is 19.14 volts dc and maximum of about 16 volts is required from a solar module/panel in order for a 12 volts lead acid battery to be fully charged.

What do I need to do before installing a solar panel?

• The number of cells in a solar panel. If there are few cells in the panel the out put will be low.
• The type of silicon used. A monocrystalline produces the highest current compared to polycrystalline silicon.
• The surface area. Cells with a large surface area have high short circuit current than small cells.
• The angle of the module/panel with respect to the sun's radiation. It should be at 90 degrees.
• There should be enough air circulation around the panel.