Hybrid milk chiller

An extensive market and human factor study revealed a large business opportunity in India for an efficient cold storage solution targeted at the dairy industry.

Sorin Grama, CEO of Promethean Power Systems, explains that dairies located in large cities have the need and the buying power to purchase refrigeration units for preserving milk at collection points located in remote farming villages. “Cold storage at the village level minimises the number of collection trips and reduces transportation costs by 50%,” says Gama. “However, the only option available was to use commercial refrigerators with diesel powered backup generators, a no-win situation that further exposed dairies to escalating energy costs.”

In April 2010, when Boston based Grama and Sam White set up their Solar Hybrid Milk Chiller – which runs partly on solar energy and partly on electricity – as a pilot project in Savoiverem near Goa in southern India, they were not sure how successful it would be. In just one month, though, the system significantly boosted the milk supply in the
village – where electricity is not regularly available – and reduced losses due to bacterial spoilage.
White explains that a detailed study of the milk collection process resulted in a system tailored to suit the requirements of this village. “Farmers milked the cows or buffaloes and brought the milk to the village collection centre. After measuring the quantity and the fat content, the milk was transported to the chilling centre, where it was cooled before being pumped from the chiller to tankers to be taken to the dairy plant.
“We observed that there were many small farmers with just one or two cows or buffaloes. Everyday, they used to bring one to two litres to the collection centres that were very far from their villages. The time taken to cover the distance used to result in milk spoilage,” he says. The duo addressed this problem by installing the milk chiller midway
between the villages and the collection centre. “The result was like a milk revolution – an individual’s supply of milk to dairies increased two-fold and more,” says White.
The Solar Hybrid Milk Chiller, which has a capacity of 500 litres and can store milk for up to 48 hours, is divided into two parts – a slow cooler and a fast cooler. While the fast cooler chills the milk from 33°C to 10°C in less than a minute, it then takes three hours to chill from 10°C to 4°C in the slow cooler. The fast cooling is the result of a special heat exchanger through which the milk is passed, chilling it in the process.
The milk chiller also keeps track of information such as the total milk collected, payment due to farmers and so on. The temperature is constantly monitored by a machine with a battery that runs on solar power. “Since we use solar energy, we eliminate the cost of diesel generators that are generally used in refrigeration systems. And as we scale up, we will lower the capital cost and the next unit will be an improvement over the previous one,” says Rajat Gupta, Promethean Power Systems’ Indiaoperations general manager.
Grama adds that the chiller unit is 66% less expensive to run than other refrigerators and is intended to be a “complete, stand-alone rural refrigeration system that stimulates businesses, reduces dependency on fossil fuels and increases the quality of life in emerging markets by enabling its users to reliably store food, vaccines and other perishable items.”
Promethean Power Systems is currently in the process of developing and testing a modular thermal energy battery that can be used as a backup to the unreliable power grid.
Grama, says: “In India, we charge the battery using the five or six hours of available electricity, usually at night, and discharge it when the grid is off in order to cool and preserve raw milk.” Promethean, however, envisions developing a battery that can be used for any cooling application. “Our vision is to enable customers to connect multiple batteries together to store energy as needed, in order to make the thermal energy battery a technology platform that allows third-party manufacturers to develop attachments such as vaccine or beverage coolers,” he states. “While our thermal battery acts like an electrical battery, it supplies a stream of cold fluid rather than an electrical current. This fluid is then be used to chill food products, such as milk, down to 4°C.”
For more information, visit www.coolectrica.com or email: info@promethean-power.com