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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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Too hot to be practical?
By Diesel Donkey on 6/21/2008 8:29:58 PM , Rating: 3
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.

If this thing melts steel, then how is black tubing going to hold up to the heat? It would have to transfer that heat to the water might quickly before it melted, it seems.

RE: Too hot to be practical?
By Chaotic42 on 6/21/2008 9:27:52 PM , Rating: 2
If this thing melts steel, then how is black tubing going to hold up to the heat? It would have to transfer that heat to the water might quickly before it melted, it seems.

Tungsten, Titanium, and any other of the several materials that can withstand the heat without melting. What would be cool is if they could get photovoltaics to be hearty enough to withstand this kind of heat, then aim mirrors at them. I wonder if that kind of setup could ever be more efficient than just heating water.

RE: Too hot to be practical?
By drank12quartsstrohsbeer on 6/21/2008 10:42:26 PM , Rating: 2
Put a larger diameter pipe inward from the focal point. Same light over a larger area = no melting.

RE: Too hot to be practical?
By Hare on 6/22/2008 3:16:14 AM , Rating: 2
... or concentrate the light to a larger surface area. Sounds simpler.

The fact that this thing can burn metal just shows that it can collect quite a lot of power from sun rays and focus it to a single point (well designed and built). It doesn't need to do that to be of great use.

Btw. Isn't this a paraboloid mirror since all edges are curved?

RE: Too hot to be practical?
By ahdlm on 6/23/2008 2:08:16 PM , Rating: 2
simply adjust the distance from the focus to a location where the temperature is apropriate for the material being used. if you want to melt sodium, keep it in a high temp container at the focus. if you want steam, keep it farther away from the focus and as a bonus get more "illuminated area" at that temp at the same time.

RE: Too hot to be practical?
By robg64 on 6/22/2008 11:58:18 PM , Rating: 2
If the mirror was focussed on a coil with a coolant such as water running through it, the drain of energy from the water being converted to steam should prevent the steel pipe from ever getting hot enough to melt.

Making the coil from a more expensive metal would defeat the point of the exercise - making a cheap collector.


RE: Too hot to be practical?
By lco45 on 6/23/2008 4:03:31 AM , Rating: 2
Hi Diesel,

Because the steel contains water, and the energy is going into boiling the water, the temperature can't really get above the boiling point of water (so long as the water stays topped up).

It's the same as a rice cooker, they switch off automatically once all the water's gone, because once the water's gone the temperate starts to rise over 100C and a thermal sensor cuts the power.



RE: Too hot to be practical?
By mindless1 on 6/26/2008 8:05:06 PM , Rating: 2
That is incorrect. The steel MUST be hotter than the boiling point of water in order to make the water inside boil. Thermal gradients at work here, while the water does keep the metal from getting nearly as hot there is still easily the possiblity of melting metal even when there is water around it.

Hint- Underwater welding

RE: Too hot to be practical?
By Jimbo1234 on 6/23/2008 1:44:51 PM , Rating: 2 running water through the pipe. The water will absorb the heat as it passes through keeping the temperature of the pipe at a desired constant. It's a simple heat exchanger.

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