Lloyd has previously argued that we should prioritize solar hot water first, then photovoltaics. But what if you could do both at the same time?
When Derek wrote about CoGenra's combined solar electric and solar thermal systems, vboring commented that it would be awesome to see a residential-scale version on sale in the States.
We have actually seen a few examples of rooftop systems that combine solar electric with solar hot water generation, Solarcentury's Complete Solar Roof being one of the most notable. Given the limited roof space of many houses, the idea of generating both direct heat and electricity in the same space is appealing indeed.
Now Joshua Pearce, an associate professor of materials science and engineering at Michigan Technological University, has devised a solution that combines improved thin-film solar panels with solar thermal collectors. In order to create the panels, the researchers had to overcome a significant issue with thin-film panels known as the Staebler-Wronski effect, whereby thin-film efficiency drops as it is exposed to light and heat:
You don’t have to cool down thin-film silicon to make it work. In fact, Pearce’s group discovered that by heating it to solar-thermal operating temperatures, near the boiling point of water, they could make thicker cells that largely overcame the Staebler-Wronski effect. When they applied the thin-film silicon directly to a solar thermal energy collector, they also found that by spike annealing (baking the cell once a day), they boosted the solar cell’s electrical efficiency by over 10 percent.
Pearce is confident about the potential of his work. In fact, he says, the combination of solar thermal and solar electric could be a game changer because it gives a significant increase in harvestable energy per square foot of roofspace. He predicts that within 20 years, every roof will be made of hybrid solar thermal/electric systems.
That would be quite something to see.