The Dawn of Solar Windows

Future skyscrapers will harvest energy from the sun with photovoltaic windows.

The view from the office of Ioannis Papakonstantinou at University College London affords a great perspective on a wasted opportunity.  He points to the university hospital, a tall oblong block adorned with decorative green glass strips.  They look modern but serve no purpose.  They don’t even let in light.

“What are they doing with these green surfaces?” he asks.  “Nothing.  Would you ever put a conventional solar panel there?  Never.”

Papakonstantinou is one of many who have dreamed of turning glass panels into photovoltaic modules that can be integrated directly into buildings, both for decoration and to look through.  His lab is among many groups and companies developing widely differing approaches to solar windows; some are already installing them in buildings.

The appeal is, well, clear.  Such windows would unobtrusively generate power for the building while allowing its occupants to peer out onto the street, enjoy natural light, or watch clouds pass overhead.

By 2020, 8.3 billion square meters of flat glass will be installed annually in new buildings worldwide, according to the Freedonia Group.  That area, covered in standard solar panels in the ideal orientation, could produce more than a terawatt at peak output, and over one year it could generate some 2,190 terawatt-hours.  That’s 9 percent of what the world’s annual electricity consumption was in 2016.  Substituting this source of energy for coal in 2017 would have saved about 1.6 percent of carbon emissions from fossil fuels, industry, and changes in forestry and land use.

And powerful regulatory forces are now dragging solar windows and their environmental benefits into reality.  A European Union directive requires all new buildings to meet a “nearly zero-energy” standard by the end of 2020.  Japan, following the Fukushima Daiichi nuclear disaster, has gone further by requiring all new public buildings to be zero energy by 2020.

Solar windows will never be as efficient as conventional solar panels, because windows must of course remain at least partially transparent.  But they can create an enormous network of small photovoltaic sources.  And developers maintain that the money that the windows save on energy will repay the cost of installing them.

Already, the cost difference is pretty small, says Thomas Brown from the University of Rome, in Italy, who used to develop solar windows.  Adding power-generating components to window materials could pay for itself in less than a decade, he says.  And there are various technologies, each with different costs and features.  Developments now under way will therefore determine whether this technology will take off and, if it does, which of the many approaches will dominate.

Read more at The Dawn of Solar Windows