Solar Panels

All about PV technology

Solar cells, also called photovoltaic (PV) cells by scientists, convert sunlight directly into electricity. PV gets its name from the process of converting light (photons) to electricity (voltage), which is called the PV effect. The PV effect was discovered in 1954, when scientists at Bell Telephone discovered that silicon (an element found in sand) created an electric charge when exposed to sunlight. Soon solar cells were being used to power space satellites and smaller items like calculators and watches.

How it works

Solar photovoltaic is an elegant technology which produces electricity from sunlight without moving parts.

In a photovoltaic cell, sunlight detaches electrons from their host silicon atoms. Tiny packets of light energy called photons are captured by electrons, and impart enough energy to kick the electron free of its host atom. Near the upper surface of the cell is a “one way membrane” called a pn-junction. The pn-junction is formed by diffusing tiny quantities of phosphorus to a depth of about one micrometre into a thin wafer of silicon.

When a free electron crosses the pn-junction it cannot easily return, causing a negative voltage to appear on the surface facing the sun (and a positive voltage on the rear surface). The front and rear surfaces can be connected together via an external circuit in order to extract current, voltage and power from the solar cell.

Solar cells are packaged behind glass to form photovoltaic modules, which have typical service lives of 20 to 40 years.

Pros of Monocrystalline solar panels

Monocrystalline solar panels have the highest efficiency rates since they are made out of the highest-grade silicon. On October 2 2105, SolarCity announced that it has developed the world’s most efficient solar panels. The new panels convert more than 22% of sunlight into electricity.

Monocrystalline silicon solar panels are space-efficient. Since these solar panels yield the highest power outputs, they also require the least amount of space compared to any other types. However, monocrystalline solar panels produce marginally more power per square foot of space used in an array and so.

Monocrystalline Panels have a long lifespan. Most solar panel manufacturers put a 25-year warranty on their monocrystalline solar panels. Because both types of crystalline solar panels are made from crystalline silicon, a very inert and stable material it is very likely that these solar panels will last much longer then their 25 year warranty life.

Monocrystalline solar panels tend to be more efficient in warm weather. With all solar cells electricity production falls as temperature goes up. However, this degradation of output is less severe in monocrystalline panels than polycrystalline solar panels. However, in practice the difference is very small. The level to which each solar panels production falls as temperature increase sis called the temperature co-efficient and is published with the specifications for each panel.

Cons of Monocrystalline solar panels

Monocrystalline solar panels are the most expensive. In recent years a rash in installation of polycrystalline ingot, cell and module production efficiencies have mean that polycrystalline solar panel have become more common and have benefited from costs advantages over mono panels. Most manufacturers that still make mono panels have targeted the premium end of the market.

Pros of Polycrystalline panels

The process used to make polycrystalline silicon is simpler and cost less. The amount of waste silicon is less compared to monocrystalline.

Polycrystalline solar panels tend to have slightly lower heat tolerance than monocrystalline solar panels. Polycrystalline solar panels will tend to have a higher temperature co-efficient than solar modules made with mono cells. This means that as heat increased output for this type of cell will fall less. However, in practice these differences are very minor.

Disadvantages of Polycrystalline panels

The efficiency of polycrystalline-based solar panels is typically 14-16%. Because of lower silicon purity, polycrystalline solar panels are not quite as efficient as monocrystalline solar panels.

Lower space-efficiency. You generally need to cover a larger surface to output the same electrical power as you would with a solar panel made of monocrystalline silicon. However, this does not mean every monocrystalline solar panel perform better than those based on polycrystalline silicon.

Monocrystalline and thin-film solar panels tend to be more aesthetically pleasing since they have a more uniform look compared to the speckled blue color of polycrystalline silicon.