Saving India’s Dairy Farmers With Thermal Milk Coolers

By Jonathan Zhou
Jonathan Zhou
Jonathan Zhou
Jonathan Zhou is a tech reporter who has written about drones, artificial intelligence, and space exploration.
September 8, 2015 Updated: September 13, 2015

In rural India, more than 400 million people live in areas where power grids are unreliable and few can count on electricity access around the clock. The inconvenience is tolerable for most, but can prove to be extremely detrimental for farmers, who need electricity to refrigerate perishable produce.

More than $10 billion worth of foodstuff is wasted in India annually as a result, much of it milk, of which India is the world’s largest producer. It’s estimated that 102 million gallons of milk is spoiled annually in India due to lack of refrigeration.

The solution to this problem comes from an unlikely source—thermal energy, a technique commonly associated with environmental efforts rather than the food industry.

Geo-thermal energy is harvested by channeling the heat naturally found under the earth’s surface for energy. Thermal coolants work in reverse, where coolant is channeled from a low-temperature material.

Recently, Prometheus Power sold its 100th thermal cooler to dairies in India. Instead of relying solely on electricity, Prometheus coolers store energy in phase-changing material (PCM), which absorbs heat when it melts, acting as a coolant during power outages.

During the heat-exchange process, the PCM is liquidized in a series of tubes that are submerged in heat-transfer fluid, which then absorbs heat from the milk via a stainless steel barrier.

“We call it a battery, because we treat it in the same way as an electrical battery: There’s a charging process and a discharge process to store energy for later use,” Sorin Grama, co-founder of Prometheus Power, said in a statement.

After winning second place at the MIT $100K Entrepreneurship Competition in 2007 for a solar energy generator made out of spare car parts, Grama considered developing a prototype for the India market, but decided to focus on making a cooler instead after discovering the magnitude of milk-spoilage in the country.

Prometheus first developed a solar-powered milk cooler, but milk was usually chilled during the early hours of the day, when sunlight was weak, so they went back to the drawing board, developing in 2011 a thermal battery to store the solar energy, but eventually they abandoned the solar component entirely.

The company received its first large commercial order in 2013, and can now count some of India’s largest dairy producers among its customers.

Prometheus claims that its chillers are more environmentally friendly than conventional cooling mechanisms, which involves burning diesel fuel to power electric generators. According to case studies conducted by the company, the chiller could easily pay for itself in a little over a year due to heightened productivity.

Each Rapid Milk Chiller has enough capacity for 20–30 dairy farmers, and can store between 250 and 400 gallons of milk at a time. The unit cost is between $8,000 and $10,000, according to MIT’s Spectrum.

The company boasts that the village of Chetawala in the state of Rajasthan, which had a spoilage rate of 5 percent before installing a chilling unit in May 2014, was able to generate an extra $600 as a result of reduced spoilage and that more dairy farmers have decided to bring their milk to the collection center as a result of the extra storage capacity.

Prometheus has already applied its cooling technology to other areas of food storage beyond milk. The company also manufactures a large freezer that uses the same thermal technology. In one case study, a large lettuce farm in Maharashtra State was able to save $16,000 within a single season by cutting down the spoilage rate in half, from 40 to 20 percent.

Grama said that Prometheus will continue to focus on India for the time being, until the business can become more sustainable, before moving onto Southeast Asia, Africa, and Latin America.

Jonathan Zhou is a tech reporter who has written about drones, artificial intelligence, and space exploration.