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The dish is composed of a set of 10 inch by 12 foot curved mirrors, like the one seen here. The students easily mount the mirrors to the aluminum framework using simple hardware like washers and zip ties.  (Source: MIT)

The mirrors incredible power makes short work of a beam of wood, disintegrating it in flames and smoke. The focal point can melt steel.  (Source: MIT)
New solar dish from MIT concentrates sunlight intensely enough to melt steel

The solar industry is booming.  With waves of investment and grants, the solar power industry is for the first time becoming a serious business.  New power plants will soon be pumping power out to consumers, while other firms market to sell panels directly to the consumer, providing them with a more direct means of experiencing solar energy.

There are many forms of solar power technology.  Today the most dominant is photo-voltaics, which comprise the traditional solar panels that come to mind when one thinks of solar power.  However, there are other promising ways of capturing the sun's energy that are merely less developed.

Among these is a parabolic collector.  A parabolic collector consists of an array of mirrors focused on a singular point, which they heat to a high temperature.  By placing water or another liquid at the collector, energy can be stored in the form of a phase transformation, and later harvested through a turbine generator.

However, parabolic collectors are still a relatively new field of research.  Their true potential remains relatively unknown.  A glimpse of it was provided by a research team at MIT, which developed a new parabolic collector design, which will blow away current solar power designs in terms of efficiency.

The MIT team believes that their lightweight, inexpensive device holds the promise of revolutionizing the power industry and providing solar power to even remote regions.

The key piece is the 12-foot dish, which the team assembled in several weeks.  The design is exceedingly simple and inexpensive.  The frame is composed of aluminum tubing and mirrors are attached to it.

The results are staggering -- the completed mirror focuses enough solar energy at its focal point to melt solid steel.  The energy of typical sunlight is concentrated by a factor of 1,000.  This was showcased during a demonstration, in which a team member held up a board, which instantly and violently combusted, when brought within range of the focal point.

By directing the dish at a more practical target -- water piped through black tubing -- steam can be flash created, offering instant means of producing energy or providing heating. 

Spencer Ahrens, who just received his master's in mechanical engineering from MIT, was among the designers of the dish.  He and his fellow team members are serious about marketing it, and leveraging its cheap cost and easy production.  They have founded a company named RawSolar.  They say their design is easily mass producible and that they hope to be pumping out 1,000 of dishes in years to come.

The new dishes would return their costs in a mere couple years, unlike standard photo-voltaic installations which can take 10 years or more to return their costs.  This improvement is critical to providing practical economic justification for adoption.

The dish is based partly on components invented and patented by inventor Doug Wood.  He was so pleased with the team's work that he signed over rights to the components to the team.  He elates, "This is actually the most efficient solar collector in existence, and it was just completed.  They really have simplified this and made it user-friendly, so anybody can build it."

Wood says one of the keys to the success of the project is the smaller size.  Dishes are affected by the same weight dynamics that effect living organisms.  Much as large living organisms would need an inordinate amount of weight support and thus are not favored, larger dish designs fall short in that they require an exponentially greater amount of infrastructure.  For example, a dish the size of the RawSolar team's design costs only a third of what a larger dish would cost.

MIT Sloan School of Management lecturer David Pelly gave a guiding hand to the students and thinks the economic upsides of the technology are impressive.  He states, "I've looked for years at a variety of solar approaches, and this is the cheapest I've seen. And the key thing in scaling it globally is that all of the materials are inexpensive and accessible anywhere in the world.  I've looked all over for solar technology that could scale without subsidies. Almost nothing I've looked at has that potential. This does."

The ability to build unsubsidized, profitable, and easy to manufacture solar power will truly be something amazing.  This should be an exciting technology to follow as it is marketed and further developed.

Besides Ahrens, the other students primarily working on the project were Micah Sze (Sloan MBA '08), UC Berkeley graduate and Broad Institute engineer Eva Markiewicz, Olin College student Matt Ritter and MIT materials science student Anna Bershteyn.



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RE: Subject
By FredEx on 6/23/2008 4:48:00 AM , Rating: 2
Depends on the cloud cover. It can still work up to a point.

Keeping the dish aimed is not real difficult.

You can make the reflective surface something other than a glass mirror. A mirror polished metal for example.

Back in the 70's when I was in tech school a teacher read an article in a magazine about using a parabolic dish to heat water. We split our class in to 2 groups, he did that with all his classes. In all there were 6 groups. He set some parameters and told us to do our best. He wanted us to fashion a 12" parabolic dish with a 3" focal point and it had to track the sun. It was supposed to heat water. My group, rather than make a dish made a parabolic reflector, but only on one axis. My roommate worked at a machine shop and we made a framework out of aluminum. We had the CNC machine cut a parabolic shaped groove in each end. Just for a temporary thing we slid sheet metal into the grooves which flexed it into a parabolic curve that was 12" by 12" with a 3" focal point. Doing that we had a long focal point across the reflector that we put .5" copper tubing painted flat black across. We went to Radio Shack and got various sensors and found a photo transistor that worked best. 2 for vertical and 2 for horizontal adjustment. Each pair ran into a comparator circuit we designed to control our axis motors. We were running out of time and money, so we bought some aquarium mirror mylar to fasten to the sheet metal for the reflector. We had wanted to get a curved piece of aluminum polished or a curved piece of metal chromed for the reflector. There was a lot more to it, such as a Z80 based microprocessor controller, but I've rambled enough. Basically we ended up with a device where we could track the sun and we could pump water in at one end of the copper pipe at a slow rate and we had steam coming out at the other end. That was on that small set-up. Something larger would have been down right dangerous.

We never completed it for class, we all went far beyond what the teacher thought we would in the time given. He never thought we'd get beyond the planning and circuit schematics. We all had varying degrees of a working unit. Ours worked the best, but we didn't do a dish, we did a curved parabolic reflector. They hit us on that. The others were way off on the 12" dish and the 3" focal point. They had done very rough dishes, but they were typically around 2' to 3'. We had proven our tracking worked though, the only ones that worked reliably, but we hadn't finished the programming for resetting back to the east for the next day of tracking. He gave us all A's, in all the groups.

About 31 years later I wonder if my roommate still has that set-up. We let him take it, since he'd popped for the aluminum and worked at the machine shop. I had all the circuitry since we did it on my Heathkit breadboard.


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