Trapped sunlight inside buildings to give power, no need to convert to electricity

If you want to use the sun to light up buildings, why waste energy by first converting sunlight into electricity?

There is one problem: it isn’t easy. Scientists have been trying to bring sunlight into commercial buildings for a while, but it hasn’t worked well because clouds interfere with the sun frequently. How would you like your office to switch between dark and bright with each passing cloud, work in dim light on cloudy days, or bathe in intense sunlight on bright days?

Now there are technologies on the horizon that can provide constant sunlight indoors, and with them would come a revolution in the design and energy use of commercial buildings.

Several technologies are being tried to trap the sun inside. All of them look for one thing: divert the excess energy somewhere on well-lit days and bring it back when the amount of sunlight dips.

This works so well in principle that sunlight can power at least 50% of the energy required to run a commercial building, while providing all the energy for lighting. Lighting takes up 20% of energy use in the world, and produces nearly three-fourths of carbon emissions. It matters to reduce energy use for lighting. It also matters for health to have the sun indoors.

Many traditional Indian houses have had tiles made of glass on the roof. A slightly sophisticated version of this uses mirrors lined in a tube to bring light inside from the roof.

Sundolier, a Colorado-based startup, uses parabolic mirrors that track the sun and then takes this harvested light indoors. The Lighting Research Centre at the Rensselaer Polytechnic Institute has developed light scoops that can provide constant and optimum light inside buildings. The light scoop uses tilted and glazed glass that can balance the light in bright and overcast conditions.

Recently, the University of Cincinnati published the details of a product — called SmartLight — that it is developing commercially, using an emerging technology called optofluidics. It combines the old area of optics and another emerging area called microfluidics, the science of small amounts of fluid. Optofluidics tries to control the optical properties of a device by changing the properties of the fluid within. It turns out that it is a great way to harvest and control the use of sunlight indoors.

The University of Cincinnati uses a grid of small cells with fluid inside them, whose properties can be changed by small amounts of power — one hundred thousandth of the amount needed to light a bulb. This grid has the ability to control or redirect light wherever it is needed, even tiny crevices. This technique combines with smart software and wireless technology to provide a solution that can be controlled from a mobile device. It also has a storage component that can provide light at night.

Solutions like these could be commonplace within four or five years. Producing electricity from sunlight is a waste if it is used to light up a building during the day. Solar cells work only at about 20% efficiency. More energy is lost when the electricity is converted back to light.

Bringing sunlight inside a building removes this waste. It also makes people more productive and healthy. There is no better way to function than in good sunlight.