Lab Solar Cells Now at 44% Efficiency
It has been a long ongoing challenge for scientists to raise the working efficiency of solar cells. And so far, we have witnessed specific achievements that pushed the efficiency rates to more than 30%,
But in the past couple of days, we have yet again seen another milestone in coming closer to the Holy Grail solar efficiency range. This is because scientists at the National Renewable Energy Laboratory (NREL) had just successfully broken the latest raw solar efficiency record with their solar cells that hold a 44% efficiency rate.
The challenge to push the efficiencies of solar energy out of its current boundaries has indeed been difficult. However design problems are only part of the problem. This is because inherently, there is also a terminal limit on the amount of energy that we could actually extract from the solar spectrum. The Shockley-Queisser limit for example, states that standard solar cells could only have a maximum solar conversion efficiency of 33.7%, and that would still have to depend on the band gap of the material. Silicon for example, with its band gap of 1.1 electron-volts, can only achieve a maximum of 29% efficiency according to this detailed balanced limit.
The scientists at the III-V Multijunction Photovoltaics Group of NREL tried to find a workaround for this limitation by developing a solar cell that can adjust and change its band gap. The culmination of their very long research for this is a new three-layered SJ3 solar cell, defined as a solar cell with “tunable band gaps, lattice-matched architecture and ultra-concentrated tunnel junctions”. This new kind of multijunction solar cell now has a 44% solar efficiency rate, effectively beating the 43.5% solar efficiency record that tech company Sharp has first made last May 2012. The achievement yet again resulted with the reception of another R&D 100 award for the research group, the third of which in the field of ultra high-efficiency multijunction solar cell research.
The researchers have long known that the most efficient application for these multijunction solar cells is to use them in concentrated photovoltaic (CPV) applications. CPV installations use low cost lenses, which as the name suggest, concentrate an intense amount of sunlight onto a small area. Such configuration can further increase the practical energy output of one multijunction solar cell, although we can probably also see this a measure to make these otherwise more expensive solar cells more cost effective for standard consumers.
The remaining question now after these amazing achievements in solar conversion efficiency is that, when can we actually start to use these lab solar cells in our roofs? It’s probable that we’ll most likely not see it out in the general tech market for a quite some time, since this innovation still has to adhere to several industry standards to make it commercially viable.
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