Solar skylight harnesses the power of daylight

Sensemaking / Solar skylight harnesses the power of daylight

Californian start-up Enfocus brings a new design to market which combines photovoltaics with cool natural light, in a cost effective way.

16 May 2012

Californian start-up Enfocus brings a new design to market which combines photovoltaics with cool natural light, in a cost effective way.

Is it a skylight, or a solar panel? A Californian outfit called Enfocus has come up with something to combine the merits of both – but bring in far more usable light than an ordinary skylight. Better still, especially in California, it'll keep out all that nasty solar heat gain too. The engineering company's patented Diamond-Power panels have impressed the guys at Google so much, that they're putting in a prototype version at one of their Silicon Valley offices.

Each 45-kilo unit consists essentially of a rectangle of aluminium and glass, about 1.5 square metres in size, holding a series of lenses that can track the sun. These concentrate the light that falls on them by a factor of 400, and throw 80% of it onto an array of high efficiency gallium arsenic photovoltaic cells. The other 20% provides a cool stream of natural light into the building, illuminating it so attractively that nobody would feel the need to switch artificial lights on at the same time. Each panel should have an average power output of 288 watts, and Enfocus reckons they'll yield around 720 kilowatt-hours of electricity per year.

The big plus, though, is getting nearly 1,500kWh worth of natural light too – without converting it to electricity and back again, and suffering the associated efficiency losses in both directions. The sales pitch suggests offices could make savings of as much as 50% on electricity during daylight hours, with a payback on outlay within about five years. The pilot project at Google will be key in determining whether this combined technology (to give both natural light and electricity) is in fact more cost-effective than the alternative: solar on the roof, and a skylight.

Unlike the kind of PV panels that you retrofit to an existing roof, Enfocus's current design has to be integrated at the building stage – part of a trend that has architects thinking about energy generation from the first drafts. So far, its plan is to concentrate on commercial customers who want to illuminate cool offices, rather than householders looking to bring daylight into dingy corridors. But with ever more people seeing solar as an attractive element in the home energy mix, you could imagine this technology being a big hit there too – a medley of "power to the people" and "let the sunshine in". – Roger East

What might the implications of this be? What related articles have you seen?

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