PV is too inefficient
It is a common criticism hurled at solar PV that solar panels are just too inefficient. However, with the wide range of research taking place, from research institutes, to R&D programs from module makers and equipment suppliers, efficiency is always increasing. In fact, some novel approaches to cell design have overcome barriers, which were previously thought to exist with PV.
At present, module efficiencies range from around 13 to 18 percent, and cell efficiencies from around 10 up to a whopping 43.5 percent – the highest results being recorded in research laboratories. The cells that produce the higher efficiencies use multiple semiconductor technologies, which are too expensive for commercial deployment. Nevertheless, the development programs at many of the leading PV module manufacturers are increasingly effective at translating laboratory cell efficiencies into module gains. Almost every month, PV companies release cell and module efficiency gains and the NREL graph gives an indication that the only way is up.
There is some debate as to whether incremental growth in efficiencies will be possible over time, however there’s certainly the possibility that breakthroughs will occur, kicking efficiencies way up. Novel and innovative technologies are being developed in university and government labs, and within the research and development programs of the solar companies themselves. Anna Rosa Lagunas from the research institute CENER in Spain set out promising technologies with great potentials at recent EU PV Power Plants conference in Vienna.
She pointed to heterojunctions, back contacting, selective emitters, light trapping structures and quantum dots as technologies with the promise to make significant efficiency gains. Lagunas also pointed to concentrating PV technology as delivering efficiencies of over 40 percent on a cell level, and above 20 percent on the module.
So while all this is going on, perhaps an analogy used by the father of dye-sensitized PV technology, Michael Grätzel can help explain how efficiency isn’t everything. He was recently awarded the 2012 Albert Einstein World Award of Science. He was inspired to apply a different approach to PV by looking up a tree, with its countless leaves photosynthesizing in the sun. He observed that each leaf is only about one percent efficient. But together, the thousands of leaves capture the energy from the sun, which we all rely on.
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