Turning Sunshine Into Megawatts

July 29, 2009 — -- For decades, Roger Angel has been reaching for the most distant stars in the universe. Now he's reaching for a neighbor, the sun.

Angel is a professor of astronomy at the University of Arizona in Tucson where he has pioneered innovative methods for creating huge telescope mirrors that now serve as the centerpieces in some of the world's largest observatories. He wants to use his own expertise, as well as that of his team of engineers and scientists who have done what many thought couldn't be done, to solve a daunting challenge.

Angel wants to capture sunshine that would otherwise fall on the Arizona desert and turn it into electricity. Not to recharge his cell phone or run his car. He wants to power the entire nation.

That may sound like a pipe dream, and maybe he can't pull it off, but Angel is not the kind of guy who can be easily dismissed. We met for the first time more than 20 years ago when Angel was tackling a problem that threatened to cripple the field of astronomy. The only way to look farther into the universe's backyard was to build bigger telescopes. Much bigger.

Lab Creates 'Next Generation Telescope'

But that translated into mega bucks, because bigger mirrors were incredibly expensive to fabricate. So Angel came up with what seems like a simple solution. He built a spinning furnace.

He placed glass in a dish on top. It melted when the furnace heated up, and as the giant contraption began to spin the molten glass flared out toward the edges, forming the parabolic surface of a telescopic mirror.

It sounds simple, but in fact it was a technological triumph.

The huge furnace had to spin at exactly the right speed to achieve the proper shape, and it had to cool down at exactly the right rate to cause the molten glass to harden in the proper shape. Too slow and it could sag. Too fast and it could break.

The lab he supervises is using that technology to create the mirrors for what has been called the "next generation telescope," the 80-foot Giant Magellan Telescope that is to be built at the Las Campanas Observatory in Chile. The international telescope will have seven large mirrors that will act as one.

Paying for Solar Energy

However, the big hurdle he faces in his drive to tame the sun isn't just technology. It's cost.

"We have to get the cost down to $1 per watt," he said in a telephone interview.

The going price these days for various types of solar energy projects is about $5 per watt, so Angel and his colleagues have their work cut out for them. If the cost can't be slashed, solar energy will remain a bit player, surviving on the government's largess because, as Angel put it, it's so expensive that "nobody builds anything without a subsidy."

The hurdles are huge, but Angel said he and his colleagues have already applied for patents for new technology developed in his lab. He can't reveal everything until the patents are issued later this year, but he did offer a few clues. He's not thinking giant telescopic mirrors. He's thinking window glass.

Standard architectural glass is produced by floating liquid glass on a base of liquid tin, and it comes off flat and polished on both sides.

"It has all the properties you want," Angel said. "It's nice and shiny and highly reflective and polished on both sides."

Put silver on one side and you've got a mirror. But it's flat, and that is the problem.

Without divulging details, Angel said he and his team are working on a technique to produce curved "float glass" that could concentrate incoming solar rays just like a telescopic mirror concentrates starlight. He said they've already produced a prototype that works, but to work on a large scale it will have to be 10,000 times cheaper than the "techniques we've worked out for astronomy."

"That's quite a challenge," he added.

If it can be done, Angel anticipates focusing the light on a new type of photovoltaic cell created by a Los Angeles company, Boeing-Spectrolab.

The 'Holy Grail' of Solar Power

According to the U.S. Department of Energy, that cell, which uses a wafer composed of different layers of material that can absorb different spectrums of light, recently achieved a performance efficiency rating of more than 40 percent, believed to be a world record. What makes the cell so appealing is it can handle concentrated light.

"If we can concentrate the light 1,000 times on that cell, it works out to 16 cents per watt," Angel said. "That means if someone like me can figure out how to put concentrated light on those cells and get the heat out the back for 84 cents a watt, then we've met the holy grail" of solar power at less than $1 per watt.

So what's the problem? It turns out it isn't just high tech.

"The problem is the mechanical complexity of pointing these optics at the sun," Angel said. That might not seem like too much of a problem, given the wide range of satellite tracking systems available today, but "it has been the cost killer," he added.

"I thought that maybe I could use satellite dish technology, so I went on the Web and looked at what it might cost to get a tracking satellite dish," Angel said. "They didn't tell me how much the dish would cost, but they did tell me how much concrete I would have to put in the ground. That blew the budget."

The system would have to be able to withstand winds of at least 90 miles per hour, so "you can't mess around with lightweight spindly stuff," he said.

Wouldn't it be something if all this grand planning stumbled over the cost of concrete, or a few pieces of steel to keep all the pieces together?

Assuming -- and that's a big assumption -- Angel and his colleagues can figure all this out, where will it lead? He sees a huge solar farm, maybe 100 miles on each side, that would collect and concentrate enough solar energy to supply the electrical needs of the entire nation.

That's a lot of land, but it doesn't have to be in one place, and there's lots of open space in the southwest deserts.

Of course, the sun doesn't shine at night, so there would have to be some sort of storage system to supply power 24 hours every day. And there are still other problems, but at least Angel has one advantage over most of us.

"For many people, all they can do is wring their hands and worry" about what's happening to the planet, he said. "At least I hope I can make a difference."