Home Up Products Saving Energy Glossary Contents About / Contact

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 pure 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 as a photon knocking 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.   

If you use batteries to store electricity you some energy is lost during the charge and discharge cycles due to conversion inefficiency. Total loss using battery storage can bring the overall efficiency down to 25%.

Energy Loss within the Solar Module

Heat: An amount of surplus photon energy is transformed into heat rather than into electrical energy. Heat adversely affects solar cell performance, 20% at operating temperature.

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

Resistance: losses through electrical resistance in the semiconductor ,diode, internal wiring and the connecting cable.

Downstream Energy Loss

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

Conversion: The solar array cannot be directly to the battery but an intermediary to regulate battery charging is required.  Battery charging electronics are  ~75 to 98% efficient.

Battery: Power is lost to heat generated while loading electricity into and extracting it out of the battery.  This is ~85% efficient overall.

In Overview there is loss due to wiring and electrical connections. The end-to-end efficiency of the system is therefore degraded by approximately 7% to 8%.

 

Home Up Products Saving Energy Glossary Contents About / Contact

 

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

Ontario,Canada Copyright 2017, STRATEnerGY Inc.    All Rights Reserved Caribbean and US
Last modified: November 13, 2018

Home Up Products Saving Energy Glossary Contents About / Contact

 

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

Ontario,Canada Copyright 2017, STRATEnerGY Inc.    All Rights Reserved Caribbean and US
Last modified: November 13, 2018