Sunlight, Only Stronger: Rethinking Solar

The five-decade quest for cheap solar power has produced an alternative energy that’s still about four times more expensive than conventional electricity.

But a group of local physicists, engineers and astronomers hope to be the first to break the cost barrier of solar energy. Their solution: concentrating sunlight to magnify its power.

If they succeed, the cost of generating solar energy on a large scale could compete with a nuclear or coal-burning power plant — minus the radioactive waste or greenhouse gases.

MegaWatt Solar has been building and testing the concept in Hillsborough since last year. The company plans to assemble a working model next week, combining a battery of reflectors with a computerized tracking system borrowed from high-powered telescopes.

By the end of the summer, MegaWatt Solar will know if the system is ready for mass production, or if it’s just another false hope in the annals of science.

On Friday, the MegaWatt Solar team fine-tuned the gleaming reflectors outside the company’s Hillsborough workshop in preparation for full assembly next week. To protect their eyes from a stray flash, some of the men wore protective torch goggles.

"You can cook a turkey on it," said the company’s president, Daniel Gregory, an electrical engineer. "It’s like concentrating 16 suns."

In an era of global warming, solar power offers the promise of clean and inexhaustible electricity without the environmental consequences. But after five decades of refinements in solar panels, converting sunlight into electricity is still too costly to operate without subsidies.

Photovoltaic — or solar — panels are made from silicon, an element found in sand. The silicon has to be highly purified in a laboratory. It’s turned into gas, liquified, and then it grows into silicon crystals. The crystals are sliced into wafers measuring 15/1000ths of an inch, or the width of several human hairs.

Solar advocates now say it’s just a matter of time before solar is competitive with other power sources.

MegaWatt Solar is hoping to get there this year. The company plans to submit its concept to Duke Energy, the Charlotte utility that is seeking bids on alternative energy proposals to help meet growing energy demand in the Carolinas. MegaWatt Solar’s concept is designed for utility-scale projects, not home use.

Backed by $17 million from Scatec, an alternative energy concern in Norway, MegaWatt Solar’s concept is among an estimated dozen projects in a race to perfect the concave solar collector, said Gary Kazmerski, director of the National Center for Photovoltaics at the National Renewable Energy Laboratory in Colorado.

By concentrating sunlight as if by a giant magnifying glass, the collectors direct much more energy to be converted into electricity. "It potentially has huge cost savings," Kazmerski said.

Inspired by good works

MegaWatt Solar was formed in 2005 by Gregory and Chris Clemens, a University of North Carolina at Chapel Hill astrophysicist who directs MegaWatt Solar’s office of technology. The two conceived the idea during five days together while they delivered donations from their church to Hurricane Katrina victims in Mississippi.

In addition to founding MegaWatt Solar, Gregory is president of Plymouth Systems, a Hillsborough firm that provides engineering services for electric utilities.

MegaWatt has 15 full-time employees, Gregory said.

Solar collectors are already being used to heat water. After years of false starts, the concept is also gaining traction as a tool for generating electricity. But challenges persist.

Unlike a simple rooftop solar assembly that is fixed in place, MegaWatt Solar’s unit requires a motor to rotate the reflectors to follow the sun’s movement across the sky.

Each mirror is an aluminum-coated signboard as big as a sheet of plywood, measuring 8 feet by 4 feet. There are 12 mirrors in each pivoting assembly. It takes 200 assemblies, weighing 1,500 pounds each, to generate 1 megawatt of electricity, enough to power about 600 homes when the sun is shining.

Vulnerable at wind

Though lightweight by solar standards, the MegaWatt Solar design is vulnerable to wind.

But to prevent a gust from twisting the frame or jamming the motor, the system is designed to "give" with the wind — moving freely and going out of alignment.

Each time the wind turns the mirrors the wrong way — 2 inches is all it takes to knock the reflectors out of alignment — the system will briefly stop generating electricity until it automatically realigns itself with the sun, following software commands.

"This came out of looking at hundreds of telescope tracking designs and thinking about them for 20 years," Clemens said.

The system is designed to operate in winds as high as 30 mph, self-correcting as necessary after a gust. But in stronger winds, the system is inoperable.

Steve Kalland, director of the N.C. Solar Center at N.C. State University, saw a MegaWatt Solar presentation recently and said wind resistance is an obvious concern for a system built with signboards.

"It’s going to take very specific weather conditions to make it work," Kalland said. "Those things basically look like sails to me."

Their maiden voyage

Gregory and Clemens say all the components work separately: The time has come for the maiden voyage in the field.

"If they don’t appear at the rate of cell towers in the next three to four years, then you’ll know we failed," Clemens said.

Staff writer John Murawski can be reached at 829-8932 or john.murawski@newsobserver.com.