A refrigerator that cools in the absence of electricity is improving life in India

Small dairy farmers are increasing their production to reduce its reliance on an unreliable power grid

This week will reach a large fridge milk to Dhaka, capital of Bangladesh. Since Bangladesh produces nearly four million tons of milk a year, hardly seems a remarkable fact; but it is a special kind of refrigerator.

Manufactured by Promethean Power Systems, a company based in Massachusetts (USA), the system keeps the milk cool a thermal battery that stores energy and releases it as chiller power over the day. Like India, Bangladesh has an antiquated power grid that supplies power sporadically - often for just a few hours a day. Rural milk producers in the subcontinent take their milk collection centers in villages that normally rely on generatorsfor diesel, dirty and expensive method of supplying power.

Two Americans, Sam White and Sorin Grama, Promethean Power founded in 2007 to address a simple but comprehensive problem: how to keep the milk without burning diesel. They take two years selling refrigerators in India ; this week marks its first export to neighboring Bangladesh.

"We in this eight years," says White, and "we've been through all kinds of different technologies, attempts and failures to define a solution. "

At first, he says, they were determined to create a technology that could exploit solar energy - a noble attempt that ultimately failed because solar energy, as the energy network in India and Bangladesh, is intermittent in nature and refrigerators need to have a constant energy. In the end, they decided on a system of thermal energy storage that uses a phase change material to store energy in the form of ice . While the grid is operational, some material freezes, and battery thermal energy that flows through a heat exchanger to keep the milk in the course of the day. The thermal battery can store up to 28 kilowatt-hours of energy.

"Do not introduce new forms of energy, simply store the intermittent energy received and distribute it in time, "White explains. Promethean Power has sold about 150 systems in India to date. The milk distribution center of Chetawala, in the state of Rajasthan, estimated to save around 40,000 rupees (about 575 euros) per month between fuel economy and reduction of spoiled milk since installed a Rapid Milk Chiller Promethean Power. The center has increased its daily milk production of 500 liters to 800 liters a day.

A vast improvement in a country where more than 300 million people live without electricity and even villages usually have a power grid often have intermittent service at best. Prime Minister Narendra Modi, who took office last year, has pledged to bring a reliable supply of electricity to the entire population by 2022.