Solar electric panels or photovoltaic cells have been under development since the photovoltaic effect was first discovered by French physicist A.E. Becquerel in 1839.
The first photovoltaic cell was developed in 1883 by Charles Fritt, who coated the semiconductor selenium with a thin layer of gold. It operated at about one per cent efficiency.
In 1921, Albert Einstein won a Nobel Prize for his 1905 explanation of the photovoltaic effect.
The science behind solar electric panels has been around for a long time and the technology continues to develop, squeezing every possible millivolt of energy from a ray of sunshine.
The first generation of solar modules are the ones we are most familiar with. These are the ones that produce power for our RVs and cabins, among other things.
Thin film solar cells are the second generation of modules and use one of either amorphous silicon, cadmium telluride, copper indium gallium arsenide or organic polymer as the semiconducting component. Although cheaper to produce, they also generate less power per unit of area than the standard first generation silicon panels that, with present techniques, have reached efficiencies of 29 per cent.
Even so, thin film is not far behind these monocrystalline silicon modules with gallium arsenide coming in at a close second in the efficiency department at 25 per cent.
However, the latest angle of attack in the battle for increasing power production, and what is now referred to as the third generation of solar cells, are tandem or multijunction cells. These cells use multiple thin films stacked one on top of the other.
Different colours in the spectrum have different energies. Blue light, for example, has three times the energy of red light but silicon cannot capture this energy.
So a triple junction cell uses gallium arsenide for absorbing yellow light, germanium absorbs the red spectrum, and indium gallium phosphide absorbs the blue rays. Each semiconductor is chosen for its ability to absorb a particular colour of the solar spectrum and an amazing efficiency of 41 to 43 per cent is produced.
These triple junction solar modules are what are being used by the Mars Rovers.
Incredibly the two Rovers, Spirit and Opportunity, have far surpassed their designed life of 90 days, due to the efficient energy harvesting of its solar panels, and Martian winds keeping them more or less dust free. In fact, Opportunity is half way on its 19-km journey between Victoria and Endeavour Craters after almost eight years of operation. Spirit shut down in March 2010 and NASA suspended attempts to re-establish communication in May of this year, ending six years, two months and 19 days of operation.
It only takes a simple calculation to determine that the third generation of the solar photovoltaic panels produce the most watts of power per dollar cost. It is just a matter of time before these panels become available to anyone intrigued by alternate energy; especially as the demand around the world steadily increases year over year, generation by generation.
Lorne Oja is an energy consultant, power engineer and a partner in a company that installs solar panels, wind turbines and energy control products in Central Alberta. He built his first off-grid home in 2003 and is in the planning stage for his second. His column appears every second Friday in the Advocate. Contact him at: lorne@solartechnical.ca.