How the sun keeps food and vaccines cold in hot climates

One of the more amazing developments in solar energy is how it has transformed refrigeration, making it possible for people to have refrigerators in very hot climates where power is extremely limited and it is almost impossible to keep food fresh. Along with this, companies have developed practical ways for low-income people to pay for them. Now these new fridges are supporting vaccination even in remote areas.

Since 2019, M-Kopa has been offering the Youmma pay-as-you-go solar-powered fridge to its customers. “We are thrilled about the positive impact that solar-powered fridges can have on customers’ lives, particularly women,” says Jesse Moore, CEO and co-founder of M-Kopa. “A fridge saves precious money and time at home, and helps small entrepreneurs grow their businesses. After months of hard work by our team and our partners Embraco Nidec, it is so rewarding to see this award-winning product begin to upgrade lives across East Africa.”

The ground-breaking 100L fridge was developed specifically for Africa in partnership with Embraco Nidec, a global cooling brand and part of Nidec Global Appliance. It won the Unit Cost Affordability Prize in the 2019 Global Leap Awards for off-grid appliances. Its innovative DC compressor provides lower starting power and greater energy efficiency than traditional models, and was developed with support from Shell Foundation in partnership with UKAID and USAID, said M-Kopa.

Because it uses one-quarter of the energy of a regular fridge, it can be powered by a smaller solar panel and a smaller battery that can keep the fridge running for a day and a half without sunlight. Customers pay for the fridge in daily installments via cell phones. New M-Kopa customers pay a $100 deposit and then from $1 to $1.50 daily for a package that includes solar lighting and installation of a rooftop solar panel. If a user doesn’t pay, the fridge stops working until they do. Once paid off — which usually takes about two years — they own the fridge and solar power system.

Now the solar fridge technology has made a big leap forward, with a truly disruptive technology invented in Wales called ‘solar direct drive’.

Ian Tansley, who had been installing battery-powered refrigerators around the world, realized that the battery was actually the source of many problems in such fridges. But what could replace the battery? Ice, as it turned out.

Tansley was on a winter walk near his home in Wales when he saw a frozen lake and, thinking about how fish swam in the water below even as the ice was frozen, came up with his disruptive idea. Water is most dense at four degrees Celsius and when it freezes, it stores a huge amount of energy.

Tansley’s research led to the SureChill fridge, which can stay cold for up to two weeks without electricity, even in external temperatures as high as 43C. During the day, solar power is used to freeze a stock of water inside the refrigerator, which then maintains the cool, steady interior temperature overnight. 

The ice acts like a battery that never wears out, storing useful, high density energy whenever power is available and thus allowing a constantly stable temperature, with or without power. “This natural phenomenon is the core of our technology, enabling our refrigerators to run for a long time with no (active) power supply,” says SureChill. “It works perfectly with solar power, weak grids or any other intermittent or limited power sources.”

SureChill is one of the world’s largest producers of these fridges, but not the only one. There are around 20 models on the World Health Organization’s list of devices approved for use in the vaccine cold chain, and they are now being used in over 50 countries.

But it is also marketing the fridges widely for homes and businesses, not just for vaccines, and it, too, has a pay as you go option to pay for the fridge.

The new generation of solar fridges is revolutionizing the fight against Covid-19 and other treatable diseases around the world, reports Reasons to be Cheerful. It notes that the Pfizer vaccine must be stored at approximately minus-100 degrees Fahrenheit, which is a huge challenge for countries in Sub-Saharan Africa, South America and beyond, where heat and humidity are abundant but, particularly in remote regions, electricity often isn’t. 

Thus UNICEF and GAVI, the vaccine alliance, have been deploying these fridges as the solution. Thomas Sorensen of the Cold Chain Unit in UNICEF’s Supply Division told Reasons to be Cheerful that the organization has helped install some 40,000 SDD units. While costing roughly $2,000 each — double the price of a standard fridge — they will last for a decade before needing to be replaced.

In 2017, 74 Godrej solar refrigerators with Sure Chill technology were distributed to more than 100 health centers in Fiji affected by Cyclone Winston, to ensure life-saving vaccines or medicines stay effective even without electricity. When the Minister for Health and Medical Services, Hon. Rosy Akbar launched the solar fridges in May 2017, she said that “ensuring the availability and efficiency of the cold chain infrastructure is a critical public health priority to protect new-born and infants from vaccine preventable diseases.”

Mali’s entire cold chain now is equipped with SureChill fridges. In 2014, UNICEF provided Mali with funding to substantially rebuild the cold chain from regional cold stores to health post refrigerators, with the particular goal of preventing vaccines freezing, which had been a major issue with conventional refrigeration. Now thousands of SureChill units have been supplied to Mali, ensuring vital vaccines are being protected throughout the country’s clinics and outreach centres.

Now 56 countries are using its technology with more than 17,000 units in use, facilitating more than 36 million vaccinations.


SureChill website.

The Fridge the Vaccines Have Been Waiting For. Reasons to be Cheerful, Sep. 3, 2021

Saving Money and Keeping Cool with Pay-As-You-Go Solar Fridges. M-Kopa, Dec. 17, 2019

The solar fridge helping African entrepreneurs living off the grid. CNN Business, Sep. 10, 2020

Global LEAP Awards: 2019 Buyer’s Guide for Outstanding Off-grid Refrigerators.


How a solar-powered fridge is helping COVID vaccines reach the remotest areas of Kenya. Euronews, Feb. 2, 2022. Engineer Norah Magero invented the Vaccibox after she was approached by dairy farmers who wanted to transport their milk to market without it going bad. Now it’s used by health centres in Kenya to transport vaccines to remote rural areas. Norah is the CEO of Drop Access, an organisation that specialises in finding sustainable solutions for supporting rural and off-grid communities in Kenya.