Saturday, November 15, 2008

Hybrid Fridge cools by sun

Hybrid fridge cools by sun

A new solar-powered refrigeration system for food storage in Indian villages that are off the grid is now under development.
The fridge is a hybrid of conventional compressor-based refrigeration and thermoelectric materials, semiconductors that convert electricity into cooling and vice versa, according to Cambridge, Mass.-based Promethean Power Systems officials.
fridge 1009

A conceptual illustration of a solar-powered refrigeration system.

Source: Promethean Power Systems

The chilling units will be cheaper than what is currently used in Indian villages, most of which are off the grid. In such villages, food distributors and processors store raw food products in traditional compressor-based cooling units that run on diesel generators. These cost about $12,000, said the company’s cofounder Sorin Grama. That cost does not include the escalating cost of diesel needed to run the units, Grama said. During a month spent in India a year ago, Grama and his cofounder, Sam White, identified a crucial niche. “Customers kept asking for a cooling system that has low maintenance and operation cost,” White said.

Grama said even including the expense of the photovoltaic (PV) panels, his design would cost about the same as or slightly less than the diesel-powered refrigeration units. More important, it would have no fuel costs and almost no maintenance costs. A compressor combined with thermoelectric modules would use 20% less power to generate the same cooling as a compressor alone, according to the company’s initial calculations.

The design uses off-the-shelf components: silicon PV panels, thermoelectric modules, and a compressor-based refrigeration unit. The company’s control system directs the two cooling components to work together so they squeeze as much juice out of the solar panels as possible, Grama said. Early in the morning and late in the afternoon, when the amount of sunlight is low, the solar panels will not generate enough power to run the compressor. But there will be enough solar power to run the thermoelectric modules, which would generate cooling until the compressor kicks in. Around midday, when the solar panels are working full throttle, the thermoelectric modules will use the extra juice the compressor does not need to provide additional cooling.