AssemblyBoard

http://dsc.discovery.com/news/2008/06/30/solar-energy-mirror-02.html
Superpower Source
 
June 30, 2008 -- Enterprising kids know you can melt crayons by focusing light on them with a magnifying glass. MIT students are now vaporizing wood, and can theoretically melt steel, by focusing sunlight with mirrors.
Their goal: cheap, super-efficient solar energy.
The students' 12-foot by 12-foot parabolic mirror, or solar concentrator, is made of off-the-shelf metal framing fitted with bent mirrors that focus the sun's light onto a single point.
The students have created a new company, Raw Solar, to sell their patented dish design.
"The first goal is to create a heat source that is cheaper than natural gas or oil," said Matt Ridder, one of the MIT students and the press officer for Raw Solar. "An eventual application is electricity generation."
Solar collectors have been around for millenniums. The ancient Greek mathematician Archimedes reportedly turned an attacking Roman fleet to ash with one.
The design the used by the MIT team was first proposed by Doug Wood, a long time solar collector proponent who worked extensively with the students to develop the new parabolic shape.
Both the mirrors and the scaffolding are exceedingly cheap and readily available, said Ridder, adding that the cost effectiveness is a big advantage of their design."This is just an incredibly simple structure to build," said David Pelly, the team's advisor at MIT. "It's not dependent on silicon or robotics for manufacturing."
Initially, the company plans to focus on boiling water at about 250 degrees Celsius (482 degrees Fahrenheit) to create 'wet steam' for industrial and commercial applications.
Much higher temperatures are feasible; Wood calculates that the solar collector could generate temperatures higher than 1,300 degrees C (2,372 F), hot enough to melt steel.
The group recently set up a demonstration dish on MIT's campus, where they proceeded to vaporize long wood beam.
While focusing light to create high temperatures works easily, turning that heat into energy is less straightforward.
There are three major ways to produce energy from high temperatures, say experts: heating a gas to drive a piston and generate an electrical current (also called a Sterling engine); using steam to drive a turbine; or focusing light onto a small, special photovoltaic cell that can absorb large concentrations of sunlight.
It's the last option that Scott Elrod, a solar concentrator researcher at the Palo Alto Research Center, finds most appealing.
"The potential to reduce costs is so great [using high-concentration photovoltaics] that you can afford to buy more efficient photovoltaic cells, the same cells that are used in space craft," said Elrod.
"What they are doing is very interesting," said Elrod. "I think that solar concentrators are a very powerful approach to capturing sunlight and using it in the most cost effective way."