Window gazers of the future may soon find themselves looking right through an energy-producing transparent glass solar panel, if the folks at the National Renewable Energy Laboratory are on the right track. Working with the company New Energy Technologies, Inc., the lab has produced a transparent photovoltaic module that is 14 times bigger than its last attempt.
Windows that double as solar panels
At 170 square centimeters (about 26 square inches), the new module is about the size of a small window. If the technology can be ramped up to a more useful scale, practically any glass window could double as a clean energy generator, with the embedded photovoltaic cell all but invisible.
The largest device of its kind produced at NREL, the new module represents a breakthrough in organic photovoltaic cell (OPV) technology according to a statement by Dr. David S. Ginley of NREL, who said that integrating solar technology into window glass represents a “promising avenue for OPV deployment.”
Organic photovoltaic technology set to rise
In contrast to conventional solar technology based on silicon, OPV cells can be made from a variety of inexpensive polymers (plastics), which can be produced in liquid form and sprayed onto a substrate, or applied using a high volume, inexpensive roll-to-roll manufacturing process.
The two sticking main sticking points so far have been increasing the size of the solar module, and increasing its efficiency. The solar energy conversion efficiency of other solar technologies has been trending up in the double digits but OPV efficiency is currently stuck around eight percent according to NREL.
Though OPV is starting from a lowly place on the conversion efficiency totem pole, its potential for building-integrated usage puts it in a strong position in the solar industry. The relatively low conversion rate could be counterbalanced by the potential for extremely low installation costs compared to other solar technologies. See-through glass solar panels could simply be substituted for conventional window glass at a marginal increase in cost, rather than being treated as an expensive add-on.
A place in the sun(shot) for OPV
Lowering the overall installed cost of solar power is a primary goal of President Obama’s SunShot Initiative, which aims to make solar energy compete on price against fossil fuels within the next few years. That partly explains why NREL is so gung-ho on OPV technology despite its low efficiency.
It should be noted, though, that the focus on OPV predates the Obama Administration. OPV was part of the Solar America initiative under the Bush Administration. Despite a conversion efficiency of only five percent at the time, a 2007 Department of Energy draft report identified some key benefits of developing OPV technology, including “the inherent low materials cost and low-energy, high-throughput processing technologies, and because of the huge variety of possible organic systems.”
OPV and American-made energy
Another aspect of NREL’s interest in OPV has to do with reliability and stability of price and supply, which are key elements in President Obama’s broader “American-made energy” pitch.
The use of a variety of polymers would enable the U.S. solar industry to overcome a major obstacle that derives from reliance on silicon-based solar technology, and that is the price fluctuation of a single key material – silicon – on the open market.
According to a report last week in Bloomberg News, China, which it describes as the “biggest…supplier to solar-panel manufacturers worldwide,” has shut down almost a third of its polysilicon production after prices fell by 60 percent, a move that is expected to result in a quick return to higher prices.
However, it’s too soon to say good-bye to silicon forever. NREL is also working with another small company, Innovalight, to develop solar modules based on a low cost, nano-engineered spray-on liquid silicon process.