Advanced Degrees

Refrigeration without Electricity

By Kevin O'Donnell | May 10, 2010

Archaic technologies get a 21st century makeover

On a recent flight from Istanbul to Chicago, I noticed a man across the aisle from me in seat 10D, frantically fumbling with his laptop computer. He was clearly agitated that his work was interrupted when he was unable to receive a wi-fi signal - comfortably hurling through the stratosphere as if by magic - at 600 miles per hour, 38,000 feet over the mountains of western Bulgaria. He whines when the flight attendant tells him there is no ice available for his scotch and soda, and he later commented to the woman next to him that his dinner salad was warm and wilted. He would, in less than half a day, be on the other side of the planet among all the modern creature-comforts he has come to take for granted, and all would be right in his world. Incensed by his current state of inconvenience, he grumbles.

Meantime, somewhere in a dry and dusty Nigerian village, a woman prepares a Zeer, two earthen pots the same shape but of different sizes. She places one pot inside the other then fills the spaces between the two pots with sand before pouring water into the same cavity to wet the sand. She then places some spinach, an eggplant and few tomatoes and peppers into the inner pot and covers the pot with a damp cloth. She stores the vessel in a dry, well-ventilated area within her dwelling and goes about her daily routine. As the moisture in the sand evaporates, it draws heat away from the inner pot, cooling its contents. The only maintenance required to this process is the addition of more water to the sand in the pot, usually twice a day.

To give you an idea of the significance to this elegant device, one needs to understand what life in the village was like without it. Before the Zeer was introduced, spinach would normally wilt within hours in the dry African heat; now it will last around twelve days in the pot. Tomatoes and peppers that normally struggle to survive a few days now last three weeks, and eggplant gets a life extension from just a few days to nearly a month. The woman's quality of life and that of her family has been improved significantly. Marveling at the convenience this technology has afforded her, she rejoices.

The Zeer was invented by Mohammad Bah Abba, an ingenious Nigerian school teacher and the son of a local potmaker. His low-cost 1995 invention was distributed to thousands of Nigerians in remote communities during the late 1990s and has improved the lives and health of countless thousands. The simple process of extended food preservation translates to less work in the fields and more education for children. Small farmers, who were previously losing large portions of their harvests to rot, are now able to earn a better income. Additionally, the Zeer improved the health of the communities where it was adopted due to better preservation of the vitamins, minerals and other nutrients the preserved food provided, resulting in a reduction of systemic diseases such as dysentery.

Access to energy services is a key component of alleviating poverty. According to the International Energy Agency (IEA), it is "an indispensable element of sustainable human development. Without access to modern, commercial energy such as electricity, poor countries can be trapped in a vicious circle of poverty, social instability and underdevelopment."

During the past 25 years, electricity supplies have been extended to 1.3 billion people living in developing countries. Yet despite these advances, roughly 1.6 billion people (which is slightly more than one quarter of the global population), still have no access at all to electricity and some 2.4 billion people rely on traditional biomass for cooking and heating, including wood, agricultural residues and dung. More than 99% of the global populations without electricity live in developing regions of the world, and four out of five live in rural areas of South Asia and sub-Saharan Africa.

Despite advances in areas such as rural electrification, the number of people lacking access to energy services has remained relatively constant due to increases in population. The total number of people without electricity has fallen by fewer than 500 million since 1990. The proportion of the world's population with access to electricity is expected to continue to rise over the next 20 years. Absent radically new innovations in global energy policy, by 2030, 1.4 billion people still will not have access to electricity under the status quo.

Without modern energy services like electricity, millions of men, women and children face debilitating illness or premature death. Basic social services like vaccination, health care and education are more costly in both real and human terms, and economic development is more difficult to sustain. Simply put, electricity can create conditions for improved living standards, especially in areas of public health, education, family life and social structure.

Refrigeration is a basic and vital element for the preservation and safe consumption of foods and storage of vaccines and other medicines. Refrigeration slows the growth of many harmful bacteria, which tend to grow most rapidly in warmer conditions and environments. The proliferation of sustainable, non-electric cooling could reduce this effect and aid in slowing the spread of disease and allow for increased storage of food and medicine for more remote regions, ultimately improving the quality of life for billions worldwide.

As the lack of electricity is often seen as the greatest impediment to refrigeration, Adam Grosser, a venture capitalist and engineer at Stanford University took on a different approach: change the fridge. The process he has adopted is called intermittent heat absorption. The technology has been around for a century and a half, but I doubt that anyone reading this can recall its commercial use. It was the precursor to modern refrigeration - an odd-looking device with an equally odd name - the Crosley IcyBall, marketed in the late 1920's. It was made in Canada and sold by the thousands to home-weary housewives across North America. When Samuel Insull developed the modern electrical grid and installed electricity in nearly every American home, the modern condenser refrigerator infiltrated American life, and the IcyBall eventually went the way of the buggy whip.

Here is how it works: The IcyBall contains two spheres. A water/ammonia mixture is used as the working fluid, or refrigerant. Water and liquid ammonia combine easily at room temperature and are isolated in one of the balls. Ammonia also has the advantage of a high latent heat. The absorption system works on the principle that a liquid such as water will absorb the gas ammonia to form a highly concentrated solution. When this is heated, ammonia gas comes off at high pressure and can then be liquefied by cooling. The absorption device does away with the need for a compressor.

When the concentrated ammonia solution is heated, ammonia vapor is produced at high pressure. The vapor is air-cooled and liquefied by the second ball, a condenser. The liquid passes on to an evaporator which in this case is a chamber filled with hydrogen gas under pressure. The liquid ammonia rapidly expands, becomes a gas and cools. This cooling can be used to cool food or medicine. Heat passes from the objects into the colder vapor causing expansion in the condenser. Because the pressure of the ammonia gas is very low (although the total pressure of hydrogen and ammonia is quite high), the whole system is kept at the same pressure.

In the next stage, the absorber, ammonia dissolves in the water, forming a concentrated solution. A certain quantity of weak solution that has lost most of its ammonia siphons over from the generator to level up the pressures. In doing so the weak solution is able to absorb more ammonia. The newly formed concentrated ammonia solution flows over into the generator to be heated by the gas flame and release its ammonia. The whole cycle continually repeats itself whenever the first ball is heated.

Adam Grosser and his team of computational fluid dynamics engineers at Stanford, along with some refrigeration experts in the U.K., have brought the Crosley IcyBall into the 21st century. Their Thermos-sized prototype device weighs just eight pounds and can be manufactured for under $40.

To charge the unit, it is heated over a fire or stove for 30 minutes and allowed to cool for one hour. Inserted into a container about 15 liters in volume, it can maintain the contents of the container at 3 C for 24 hours at a constant 30 C ambient temperature.

At this stage in the development of this refrigeration prototype, some questions linger regarding its practicality. There are, of course, some human inhabited environments that average above 30 C and many may desire more sizable storage than a 15 liter container. Additionally, the process is labor intensive and it's time consuming to heat the device, especially for villagers who will have to build a fire every day to do so. But the trade-offs can be significant and can go a long way for improving the quality of life for many thousands even in the smallest degree. It is likely that with further development, these devices could be produced in multiple sizes and operate in many environments.

Evidence of evaporative cooling technology dates back to at least 1600 B.C. in ancient Egypt and thanks to an Algerian school teacher it has found its way into everyday life and into modern packaging of temperature-sensitive medicinal products, albeit slowly with nanocool rapid evaporation products and the recently commercialized zeolite technology. Intermittent absorption refrigeration too, has been given a new application in a modern world and its potential is very promising. Who knows, with the adoption of these seemingly archaic technologies, in both developing and developed countries, maybe we'll all have a reason to rejoice - even the guy in seat 10D.

Kevin O'Donnell is director and chief technical advisor to industry at Tegrant Corp., ThermoSafe Brands. He can be reached at kevin.o' He blogs at Where Cooler Heads Prevail.
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