A Cheaper Solar Concentrator

A new light-guiding optic combines low cost with high efficiency.

Nicolas Morgan holds up a square piece of clear, molded acrylic about a centimeter thick and shines a penlight directly at its flat surface. A green beam enters the acrylic and bends toward the center of the square. Morgan repeats the process at different points on the surface, and each time, the beam darts toward the center.

Guiding light: Morgan Solar’s high-precision optic--part acrylic and part glass--is molded so that light is trapped and bounces toward its center. A secondary glass optic concentrates the light to 1,000 suns and directs it to a tiny, high-efficiency solar cell. The low-profile design promises to reduce the cost of manufacturing and transportation. Credit: Morgan Solar

The acrylic component--called a Light-Guide Solar Optic (LSO)--is a new type of solar concentrator that could significantly lower the cost of generating electricity from the sun. Unlike existing designs, there's no need for mirrors, complex optics, or chemicals to trap and manipulate the light. "It's pure geometric optics," says Morgan, director of business development at Toronto-based Morgan Solar.

Solar concentrators have emerged in recent years as a way to intensify the amount of sunlight hitting solar cells, which are the most expensive part of solar panels. To make solar power more affordable, engineers have sought to use less solar-cell material by concentrating sunlight onto much smaller spaces.

But this approach has its own challenges. Most concentrators tend to be complex systems that use special lenses, curved mirrors, and other optical components with a "nonzero" focal length. This means that there must be enough distance--an air gap--between the solar cell and the optic to properly focus the light. As a result, concentrator-based systems are usually packaged within bulky enclosures, with enough depth to accommodate the focal length and protect all components during shipping. This means higher material and assembly costs and more expensive shipping.

A couple of years ago, Nicolas's brother John Paul Morgan came up with the idea of a solid-state solar concentrator system: a flat, thin acrylic optic that traps light and guides it toward its center. Embedded in the center of Morgan Solar's concentrator is a secondary, round optic made of glass. With a flat bottom and convex, mirrored top, the optic receives the incoming barrage of light at a concentration of about 50 suns and amplifies it to nearly 1,000 suns before bending the light through a 90-degree angle.

Unlike other concentrators, the light doesn't leave the optic before striking a solar cell. Instead, a high-efficiency cell about the size of an infant's thumbnail is bonded directly to the center bottom of the glass optic, where it absorbs the downward-bent light. There's no air gap, and there's no chance of fragile components being knocked out of alignment.

Story continues below

"It's all about critically controlling the angles once the light enters the first optic," explains Nicolas Morgan. The design takes advantage of a phenomenon called total internal reflection--the angle at which a beam of light inside an optical material will reflect back into the material rather than escape.