PV SYSTEM Efficiency

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Solar Cells

A photovoltaic cell (sometimes spelled photo-voltaic) or shortened to PV are used to convert solar energy into electrical energy. Solar cells are the basic elements of a solar module. Silicon is by far the most common material of semiconductors from which solar cells are made. Unfortunately silicon while the most prevalent media, is expensive to manufacture and requires a lot of sunlight to push electrons around.

The amount of the current produced is proportional to the sun on the solar panel. When a cell is exposed to the solar energy, photons with energy equal to the material bandgap are converted into electrical energy. When an electron (negative) is knocked away from an atom, it leaves behind a positive charge or hole. A proportion of charges that cross the bandgap can be harvested by completing a circuit from a grid on the cell's surface to a collector on the backplane. Simplified, think of sunlight (a photons) knocking as an electron off one media to another to create the electrical potential of solar panels.

The usable voltage that a solar cell produces depends on what semiconductor material it's made from. In the case of silicon-based cells, the output is approximately 0.5 V per cell.

Although the current increases with increasing luminosity, the terminal voltage is mostly dependant on semi-conductor material and only slightly dependent on the amount of light falling on the cell.

Obviously PV energy is only available while the sun shines. The electrical energy needs to be stored and recovered for later use. Usually battery storage is used. An alternative is returning power back to the electrical generating grid. For the consumer, using the power grid is a viable option. You only lose the inefficiency in converting the solar energy to electricity. However without subsidies and fabourable electrical purchase contracts from your utility the cost of the energy produced by solar voltaics is presently much higher than what you pay to your utility.

If you use batteries to store electricity you lose power during the charge and discharge due to conversion inefficiency. Total loss using battery storage can bring the overall efficiency down to 75%.

Solar cell Types

There are three common types of solar cells, which are distinguished by the type of crystal used in them. They are monocrystalline, polycrystalline, and amorphous. There are lots of other PV technologies being worked on and refined for commercial production but they are not yet commercially viable.

A monocrystalline silicon cell, must be made with absolutely pure semi conducting material. Monocrystalline rods are extracted from melted silicon and then cut into thin plates.

Polycrystalline cells manufacture is more cost-efficient. The same process as monocrystalline manufacture is used. However, during solidification of the material, crystal structures of varying sizes are formed, at whose borders defects emerge resulting in somewhat less efficiency.

Amorphous or thin-layer cell are formed when a silicon film of 1/1000 meter is deposited on glass or another substrate material. Material costs and efficiency are lower than monocrystalline and polycrystalline cells.

Energy Loss within the Solar Module

Spectrum: Differing semiconductor materials or combinations are suited to specific spectral ranges because of this a portion of the radiant energy cannot be used because the photons have insufficient energy to activate electrons across bandgap (charge carriers).

Heat: An amount of surplus photon energy is transformed into heat rather than into electrical energy. Heat adversely affects solar cell performance.

Optical: Losses resulting from shadowing of the cell surface through contact with the glass surface or reflection of incoming rays on the cell surface.

Resistance: losses through electrical resistance in the semiconductor and the connecting cable.

Downstream Energy Loss

Resistance: Electricity traveling through wires encounters resistance. The lower the voltage and higher amperage and the longer the longer distance electricity runs the higher the electrical loss.

Conversion: The array cannot be directly to the battery but usually we want an intermediary so to regulate battery charging. Battery charging electronics are ~70 to 90% efficient.

Battery: Power is lost in putting the electricity into and extracting it out of the battery. This is ~75% to 80% efficient.

Overlooking the loss due to wiring and electrical connections. the end-to-end efficiency of the system is therefore approximately 7% to 8%

Links to our Photovoltaic Panels

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Contact Us: Telephone: toll free at 1-888-810-4709 Parry Sound,Northern Ontario,Muskoka and Georgian Bay
Send mail to: info@enviroharvest.ca with questions or comments about our product or web site.

We treat customers in the way we would like to be treated.

Contact Us: Telephone: toll free at 1-888-810-4709 Parry Sound,Northern Ontario,Muskoka and Georgian Bay
Send mail to: info@enviroharvest.ca with questions or comments about our product or web site.