Never mind the suntan…

Never mind the suntan…Melanie Reynolds
On those rare occasions when the sun is beating down on you it really is possible to appreciate its power.
Besides making us feel good though the energy from the sun has potential for producing electricity. And unlike the human feel-good factor the electricity is produced even when the sun is not visibly shining.
A major advantage of solar energy is that it won’t run out (for an extremely long time) and once the panels are produced it is non-polluting. In February the government gave it a push by announcing sponsorship for solar energy projects to the tune of several million pounds.  
  Fuelled by the sun… BP Amoco is forging ahead with its use of solar power technology, announcing that around 200 of its service stations worldwide are to incorporate solar power.
Along with the European Union’s enthusiasm for increasing the role of renewable energy sources, and its desire to accelerate the rate at which they are adopted, it seems that things are happening.
A number of people consider that solar is the best route to take. “In the European market it is seen as really the only renewable technology which is compatible with the urban environment,” said Nigel Mason, senior photovoltaic technologist at BP Solar, the solar division of BP Amoco. “You can put these modules on the roofs of buildings and they blend in well.”
BP Amoco is already forging ahead with its use of the technology, announcing that around 200 of its service stations worldwide are to incorporate solar power. The company says that the $50m, 3.5MW project will save around 3,500 tonnes of CO2 emissions each year.
Solar panels use photovoltaic cells which are essentially silicon p-n junctions to convert sunlight into electricity.
The vast majority of the products currently sold are based on silicon wafers which have screen printed metal contacts applied to each side. The metal on the front of the panel is in a grid to allow the light to reach the silicon.
Progression from this construction has led to thin film technology where layers of semiconductor material are deposited on glass. This makes manufacture simpler and cheaper.
The conversion efficiency of panels using screen printed contacts is typically 12.5 to 15 per cent and as such is an area where a lot of R&D effort is made.
BP Solar is currently concentrating its R&D efforts on laser-grooved buried-grid (LGBG) cells.
This technology avoids the screen printing of contacts by using a laser to cut a fine grid into the silicon wafer. The grid is then filled with metal using an electro-plating process.
According to BP burying the grid deep in the silicon enhances the collection of electrons. Combined with the fact that the grid takes up little surface area thereby letting more light through to the silicon this raises the efficiency of these cells to around 17 per cent.
Mason believes that the highest efficiency achieved for solar panels so far is 23 per cent in laboratory conditions. “But they tend to be on very high quality substrate which is expensive.”

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