Two Men from the US Are Helping Dairy Farmers in Rural India Keep Milk Chilled without Electricity

Rural dairy farmers in India produce about 102 million gallons of milk every year. Transporting this milk to the processing centres of different dairies without refrigeration and reliable electricity is difficult. Two men from the US came to India to solve this problem.

Rural dairy farmers in India produce about 102 million gallons of milk every year. Transporting this milk to the processing centres of different dairies without refrigeration and reliable electricity is difficult. Two men from the US came to India to solve this problem.

Promethean Power Systems has developed a milk chiller that operates on a thermal energy battery and can function even in remote Indian villages receiving intermittent electricity supply. Founded by US-based Sorin Grama and Sam White in 2007, Promethean Power has installed over 200 milk chilling systems throughout rural India. About 20 farmers can use one chiller. These are farmers who were unable to supply milk to dairies earlier because they couldn’t refrigerate the milk without reliable electricity.

In India, many dairy farmers produce varying quantities of milk, which is then aggregated and transported to dairies via small, village-based collection centres. If the milk is spoiled before it reaches the dairy, the farmers are not paid.


Promethean Power’s chiller uses an innovative thermal battery technology, meaning the battery saves energy instead of electricity. The chiller has a battery pack that contains a phase changing material. This material changes form from solid to liquid and vice-versa.

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The machine has three components – a can to pour the milk into, the thermal energy battery, and a compressor.


A control panel tells the system when to switch on and off based on the temperature of the milk. Using sources such as solar power or a few hours of grid electricity, the compressor switches on and charges the battery, meaning it forms ice. To cool the milk, this ice is released in the form of cold energy. On reaching the required temperature, the energy flow shuts down. These milk chillers are used in villages to chill the milk at the collection points, before transporting it to the processing plants.

Promethean Power was born in the Massachusetts Institute of Technology where Sorin and Sam wrote a business plan for a clean energy startup.


They won $10,000 as the runners-up of an MIT pitch competition and developed the initial product idea. After this, they decided to visit India to see where it could be used.

“The founders were working on clean energy technology. After several prototypes, they came up with a micro solar generator, which they thought would be ideal for use in developing countries. But when they came to India to understand where they could apply the technology, they realised that it was not something the country needed,” says Jiten Ghelani, CEO, Promethean Power Ltd., India.

Two weeks into the trip, Sorin and Sam went to meet the engineers at Bangalore Dairy. The Managing Director told them about the milk collection problem. The Bangalore Dairy was working with farmers in about 10,000 villages at the time and it was a challenge to collect good quality milk from them when they didn’t have sufficient electricity.

The duo then went back to Boston to come up with a solution for this. After several failures, they eventually came up with the energy storage device.


While the founders kept travelling between Boston and India for many years, it started becoming difficult for them to run the business this way. Sorin moved to India in 2012 and lived here for about three-and-a-half years.

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“We came to India with a solution, looking for a problem to solve. It was not the best way to start a business. Fortunately, during our trip, we found a problem looking for a better solution…The Indian dairy problem is a unique problem and nobody was working on it. I saw a business opportunity first and foremost. Additionally, as an engineer, I saw a challenging technical problem that needed a solution. And I love solving problems. Beyond that, I saw an opportunity to make an impact on a larger scale. Working on this startup was difficult but personally, very rewarding,” says Sorin, who graduated with a Master’s of Science in Engineering and Management degree from MIT. Sam received his BA in political science from Union College and is from Boston.

Currently, the chiller is used in many villages in Tamil Nadu, Maharashtra, and Rajasthan, where suitable infrastructures have been created to support the machine.


It costs about Rs. 5-6 lakh and is mostly purchased by dairies. One machine can store 300 – 800 litres of milk.

Thanks to this technology, dairy farmers are now able to chill milk without having to rely on a diesel generator.


Over the years, milk generation in these villages has increased. The farmers are now paid regularly and are more confident about working with the dairies. As for Sorin and Sam, seeing their machine being successfully used is the biggest achievement of all.

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