Functioning solar cells
We distinguish between Passive solar energy (penetrating sunlight for heating and lighting of buildings and Photo Voltaic solar energy PV- Photo (light) Voltaic (electricity) is when sunlight is converted into electricity.
Photovoltaic’s (PV) is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. A solar power system is normally very simple. The key element absorbs light and converts it into electrical energy. One of the difference between the existing power generators is that there are no moving parts.The conversion efficiency can never reach 100% because there is always a percentage wasted in the form of heat. Solar cells are made from semiconductor materials. This material has a special feature that under light, the effect of negatively charged electrons are freed to move. These electrons also allows movement of positively charged holes behind.
The operation of the solar cell is based on the fact that electrons and holes are separated so that a negative voltage gets at the front side and the positive voltage gets at the rear side.
These cells provide direct current (DC). When front and back are connected together. an electric current causes the cell to supply useful energy to a battery, a pump or to the electric local grid.
What are electrons?
Electrons are small negatively charged particles that rotates on a positively charged atomic nucleus.
What types of solar cells are there?
Silicon is the most common material for cells today and poured in block (ingots) in laboratory.
These ingots are sliced into very thin wafers and then cut and polished.Electrical connections (bus strips) are placed to both sides of the cells and then they will get an anti-reflective coating.
Mono-crystalline and poly-crystalline cells are the most popular and easily available in the market today.
Mono-crystalline cells produce more power per square meter and costs more to produce than polycrystalline cells.
Pure silicon crystals with (one direction structure) thinly sliced and treated.
Maximum efficiency of cells in laboratory (25%)
Mono crystalline modules efficiencies (14-19%)
Mono-and poly-crystalline cells are manufactured in many shapes and sizes such as round, square, rectangular, depending on the application or customer preference.
Most mono-and poly-crystalline cells produces approximately 0.50 to 0.7 volts, regardless of the size of the cell.
Pure silicon, with irregular crystal structure is cut into thin slices.
Maximum laboratory cells efficiency (20%)
Polycrystalline solar cells are made from cast square ingots of molten silicon carefully cooled, solidified and cut.
These poly cells are less expensive to produce than single crystal silicon cells, but are less efficient. This is why poly panels have a lower solar cell efficiency than mono panels and a lower embedded energy.
These panels are used for small and medium-scale solar energy applications.
Larger polycrystalline modules are also suitable for residential and commercial solar installations.
Poly crystalline panels tend to be better in higher temperatures than mono panels as illustrated by the open circuit voltage.
Poly-kristallijne modules rendement (12-14%)
Poly-Crystalline modules efficiency (13-17%)