September 17, 2007 1:08 PM PDT

A solar refrigerator for developing world

by Michael Kanellos

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The Solar Turbine Group is trying to bring refrigeration to emerging nations by harnessing the power of the sun.

The organization, which consists largely of MIT alumni, has devised a solar thermal generator that can be brought to market for $12,000 or less. A typical system can generate 600 watts of electricity or 20 kilowatts of energy for heating and cooling, according to Sam White, director for STG. The same system can also produce both at the same time, albeit less of each.

Parabolic mirror for capturing the sun

(Credit: Solar Turbine Group)

Like other solar thermal systems, STG uses mirrors. Mirrors concentrate heat from the sun onto a tube filled with a liquid (in this case glycol). The heat from the liquid can then be used in two ways. One, the heat can be transferred to another liquid. The second liquid gets vaporized and ultimately gets used to turn a turbine to create electricity.

Two, heat from the glycol can be used to boil refrigerant.

Although many villages in emerging nations don't have electricity, a lack of refrigeration is perhaps a more dire problem. Without refrigeration, food-borne diseases spread more rapidly. Farmers also can't store their crops in hopes of getting a better price, noted White. Thus, something like this could help improve health and local economies.

One reason the Northern Hemisphere (in my mind) moved ahead of the Southern Hemisphere is that the people there had to only figure out heating, a relatively straightforward process, rather than cooling. (I came up with that idea one day in Malaysia after walking into an air-conditioned Burger King after four hours in the midday sun.)

Hawaii's Sopogy is marketing similar devices in developed countries.

The company has installed a few prototypes in Lesotho and wants to put some in India. What has the group learned? That they have to show locals applications where and how the generator can be used. Locals just don't come up with the ideas on their own at first. "That was probably the most useful insight," he said.

The low cost comes in part because many of the parts required to build one of its solar generators are actually old car parts, White said. There's another problem solved: putting salvage to good use.

Originally posted at News Blog