Solar energy collection might just be the best alternative energy solution. It collects energy from outside the earth's ecosystem, instead of stealing the kinetic energy from the planet itself. If we are going to do so, collecting more of that energy is paramount. Up until now, commercial solar energy collection peak at around 15% light to energy transfer efficiency. Those standard returns have been shattered by a couple of companies out of the USA.
Alta Devices solar panel (via University of California at Berkeley)
Founded in 2007, California based Alta Devices has collected well over 72 million USD in investment funding. At the Photovoltaic Specialists conference (PVSC37) Alta Devices demonstrated single-junction solar cells, made of gallium arsenide (GaAs),with a conversion efficiency of 27.6%, gaining them the world record for conversion under 1 Sun illumination. Maximum to date form Alta was 28.2%
Alta Devices co-founder and University of California at Berkeley Professor Eli Yablonovitch explained the tech behind the world record at PVSC37, "Up until now it was understood that to increase the current from our best solar materials, we had to find ways to get the material to absorb more light. But, the voltage is a different story. It was not recognized that to maximize the voltage, we needed the material to generate more photons inside the solar cell. Counter-intuitively, efficient light emission is the key for these high efficiencies.”
The photovoltaic (PV) boost from Alta Devices was later evaluated by the National Renewable Energy Laboratory (NREL) to have a consistent 23.5% conversion rate. To go along with the boost is an Alta invented manufacturing process where one micron thin GsAS layer, making for an extremely flexible solar cell. This process brings down the cost of the solar panel substantially. With price and efficiency into consideration, the Alta Devices cell is a close competitor to fossil fuels, even without subsidies.
The theoretical maximum efficiency for single junction cells is 33.5%, also known as the "Schocley-Queisser Limit." Alta strives to get even closer in the coming years.
(Left) Semprius solar panel (via NREL) (Right) Die placeing solar dots on a substrate (via Semprius)
On the other side of the country, North Carolina based Semprius gains a 33.9% PV module efficiency (850w/m²). Semprius employs high-concentration PV (HCPV) Triple-junction GaAS cells. Even with the ability to print solar cells as small as a sentence period, Semprius is burdened with the high-cost of triple-junction cells. Never the less, it is the first time that over 1/3 of the sun's energy has been converted. The NREL recorded that with the concentration of 1,000 suns, the triple-junction was able to convert 41% of the energy.
Semprius CPV applications engineer Kanchan Ghosal explained, "We're using a completely different approach to what has been practiced. This approach uses micro-cells and transfer printing to significantly reduce the use of materials in highly concentrated PV modules. And it provides a highly parallel method to manufacture the module, based on established microelectronics processes and equipment."
After inventing a way to lower solar-cell printing at Semprius, Seimens bought a 16% stake in the company. Coupled with over $38 million in other investments, Semprius make make a solar splash yet.
Either way one goes, there is a sizable return on investment cost with solar energy. Up to 5 years to pay off the cost of equipment is standard. The efficiency boosts lower that time, initial cost still remains the number one hurdle to a wider adoption of solar.
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