South Asia may be the world’s leading producer of milk, but its dairy farmers have to fight hot weather in a region where electric refrigeration is can seldom be relied on. But now a company based both in the United States and in India has come up with a battery that uses heat to keep milk cold.
Many farmers in India and Bangladesh transport their milk to small collection centers in their neighboring villages, where it is sold to representatives of large dairies. If the milk spoils before it’s collected, the farmer isn’t paid. And conventional refrigeration isn’t an option because of the spotty electrical service provided by India’s electrical grid.
So far, the only alternative is for each farmer to invest in a diesel generator, which not only increases the expense of producing milk, but also is bad for the environment.
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Now Promethian Power Systems, based in Boston and in Pune, in west-central India, has what may be the solution: Rapid Milk Chillers powered by a thermal battery that creates enough ice to store 28 kilowatt-hours of energy.
When electricity is available, ice forms in the battery as it charges. When the grid fails, as it does often, the ice maintains of the temperature of the chilling unit. Each of these refrigerators holds more than 500 gallons of milk, keeping it cool long enough to last until it is collected. The dome-shaped device can quickly cool milk from 95 degrees Fahrenheit down to 39 degrees.
Promethian Power was founded in 2007 by two Americans, Sam White and Sorin Grama, to address this very dilemma faced by dairy farmers in South Asia. Already the company has been selling units in India, and recently began sales in neighboring Bangladesh.
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“We’ve been at this for eight years,” White said in an interview with MIT Technology Review. “[W]e’ve gone through all sorts of different technologies, attempts and failures to figure out a solution.”
One failure was an effort to use solar power to cool the milk. But, like the electrical grid in South Asia, solar power is far from constant. After testing a few other technologies, the researchers at Promethian Power eventually developed a device that uses technology known as phase-change, which relies on heat transfer to transform one phase of a given material to another.
White said the result isn’t a new form of energy. “[W]e’re simply storing the intermittent power that they do get and parceling it out over time,” he explained.
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Already there’s evidence that the technology has improved the economics of milk production. The dairy collection center in Chetawala, in India’s northwestern state of Rajasthan, reports that it’s saved about 40,000 rupees ($628) each month since it installed Promethain Power’s dairy refrigerator, and that its production has grown from about 500 liters of milk per day to about 800 liters per day.
Large dairies that buy the farmers’ milk install the Rapid Milk Chillers in pairs at the village collection centers. The units can keep milk fresh for as long as two days. This means collection tanker trucks no longer have to make daily pickups.
Since it began marketing the Rapid Milk Chillers in 2012, Promethian Power has sold 60 pairs of the devices, and plans to sell even more as demand for them increases. Meanwhile, White and Grama are adapting their technology to help preserve other perishable foods such as vegetables.
By Andy Tully Of Oilprice.com
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Andy Tully is a veteran news reporter who is now the news editor for Oilprice.com