Solar Windows – Again
I’ve been seeing solar window ideas for years and I am skeptical about their practicality. Check this recent article for more info http://www.extremetech.com/extreme/188667-a-fully-transparent-solar-cell-that-could-make-every-window-and-screen-a-power-source (Thank you Deanna for bringing this article to my attention.)
I’m surely open to new ideas, but here are some of the challenges I see with this idea:
1. I always wonder about wiring all the windows together and getting that electricity to the electrical service panel. It is obviously not a casual retrofit, so maybe just applicable to new construction. There are other electrical challenges that could be addressed by standardizing size and shape of the window pv modules, but possibly at the cost of some aesthetics if everybody’s home begins to have identical windows. That is not my biggest worry though.
2. They are claiming 1% efficiency currently and hoping to quintuple that to 5% eventually with this product. The leading SunPower pv modules we are installing currently are in the 20-22% efficiency range, meaning for every 1000 watts of light energy that hits the pv module, they generate about 200 watts. We are usually using the highest efficiency modules we can get because we are striving to make as much energy as possible per installation.
3. Even using the highest efficiency modules we can get, we are often limited by available roof space and can’t make as much energy as we would like. There is much less window area compared to roof area. The roof, being highest, is generally the sunniest portion of the building.
4. Windows are basically holes in our insulated buildings; even the highest tech triple pane Argon-filled windows are major heat losers here in the PNW. I wouldn’t want to see people increasing window sizes and decreasing the insulation value of the building’s envelope in order to make more electricity – that would be going backwards fast overall. And in the summer, having too much south-facing glass is the best way to require air conditioning, a huge energy load that should be unnecessary in PNW homes.
After 12 years installing pv, and seeing so many new solar innovations announced without coming to fruition, I have become convinced that until we put standard pv modules (currently available and fairly inexpensive) on every sunny roof, products like solar windows are solving a problem that does not exist.
I agree with all your observations Andy. From my perspective, the most bang for the buck is efficiency first. Then a less expensive modest array will “pay back” that much quicker.