In the Lab vs. Real World
Beating solar PV efficiency records in the lab is great - just recently, a 40.7% record from 2006 was beaten by the National Renewable Energy Laboratory (NREL) with a new record of... 40.8% - but in the short-term, what matters most is what makes it to market.
25% Cheaper, On Sale Within 18 Months
Day4 Energy, a startup from Burnaby, British Columbia, Canada, has announced that it has created a process to cut costs for multicrystalline silicon solar panels by about 25%, from about $4 per watt to $3 per watt. Still not price-competitive with coal on a large scale, or even with solar thermal power, steady incremental improvements like that will get us there, and for applications where regular solar panels were already used, this will just improve things (either more bang for your buck, or lower prices).
In conventional solar panels, the silicon that converts light into electricity is covered with a network of silver lines that conduct electrons and serve as connection points for soldering together the individual solar cells that make up a panel. The network consists of rows of thin silver lines that feed into thicker wires called bus bars. Day4 replaces these bus bars with a new electrode that consists of rows of fine copper wires coated with an alloy material. The wires are embedded in an adhesive and aligned on a plastic film. The coated copper wires run on top of and perpendicular to the thin silver lines, connecting them to neighboring cells. The new electrode conducts electricity better than the silver lines, resulting in less power loss. It also covers up less of the silicon than the bus bars, leaving more area for absorbing light.
Day4 Energy currently has enough production capacity to make enough panels to generate 47 megawatts a year (up from 12 megawatts in 2007), but they are still making panels using only half of their new technology, the electrodes, but not the new cell design yet. Their current panels are 14.7% efficient. The next step is switching production over to the new 17-18% efficient cells, and then if they can successfully do that, they will probably want to ramp up production.
Interestingly, Technology Review and the Day4 press release have different efficiency numbers. TR claims 17% while Day4 says 18%. The truth probably lies somewhere in between. Maybe Day4 rounded things up generously for their press release, maybe tests generated a whole range of results, etc.
Many competitors of Day4 Energy promise solar panels that are more efficient and/or cheaper, but most of those are a few years away.
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More on Day4 Energy
Day4 Energy Official Site
More-Efficient Solar Cells
Update: If you are interested in solar power, also check out 15 Photovoltaics Solar Power Innovations You Must See.