Promethean Power System's rapid milk chiller. Image:
Promethean Power System’s rapid milk chiller. Image:

An MIT alumnus’s company is helping farmers in India get their milk to market before it spoils, thanks to a new method of energy storage.

Cofounded by Sorin Grama SM ’07, Promethean Power Systems produces rapid milk-chilling units powered by thermal energy batteries. The chillers are specifically designed for use in rural villages without a dependable source of electricity. The thermal battery forms ice when electricity is available; when electrical power is interrupted, milk is chilled using thermal energy stored in the battery.

Grama hatched the idea behind Promethean Power during a student trip to India focused on analyzing the business potential for low-cost solar turbines. Grama discovered breakdowns in fresh food supply chains that particularly affected dairy farmers: because of an unreliable power grid, milk frequently spoiled before it could be transported from village collection centers to dairies.

Back in Cambridge, Grama’s business plan for a new refrigeration system took second prize in the 2007 MIT 100K Business Plan Competition. Promethean Power was born later that year. After experimenting with solar power, which proved prohibitively expensive, Promethean developed its thermal energy technology.

Promethean’s chillers eliminate the need for pollution-producing diesel power generators, are easy to maintain, and are inexpensive to operate. Each unit can support production from 20–30 farmers, storing 1,000–1,500 liters of milk for up to two days. Units cost between $8,000 and $10,000.

“Our systems are just a bit more expensive to buy than a regular diesel generator system, but the savings in operating costs make up the difference in one year,” Grama recently told Green Tech Media. Grama estimates the batteries have a lifespan of about seven years.

More than 100 chilling systems have been installed throughout rural India. In addition to milk chillers, Promethean also offers cooling systems for storing fresh produce. Learn more about the technology at the company’s website.

Promethean Power Systems participated in MIT’s Venture Mentoring Service, and Grama was a member of the Lemelson Foundation’s 2014 Inaugural Class of Invention Ambassadors.

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