Solar technology delivers refrigeration to off-grid areas
Solar power is increasingly becoming fashionable, meaning that people living off the electricity grid can still share the joys of previously unfathomable technology.
Among the recent technologies gaining currency in the Kenyan market are solar fridges and freezers.
A solar-powered refrigerator runs on electricity generated from the sun. The cooler operates with a compressor powered directly from sunlight.
The refrigerator stores thermal energy in ice and a thermostat maintains the temperature between the required limits.
Off-grid refrigerators have long been used in remote areas of Kenya and other countries. But previous refrigerators either used kerosene or gas, which were both harmful to the environment and posed a health hazard to the users.
And even then, the initial solar-powered fridges have been the preserve of social welfare institutions like rural hospitals with no access to electricity. Most were gifts from international donors.
Rural hospitals may have been the initial adopters, setting the pace for the technology. Now even hotels are following suit.
One of the marketers of this range of fridges, Chloride Exide Kenya Ltd, says they have lately been in unprecedented demand.
Other than rural clinics and schools, Mr Tim Jessop, the Chloride Exide general manager says, “We are seeing growing demand for solar fridges and freezers for Safari camps, hotels and lodges, and small businesses in remote areas of the country.”
Mr Jessop further says that fridges “are also being purchased for use in homes.”
He explains: “The heavy demand for power from normal AC fridges or freezers make them unsuitable for a solar energy system. In complete contrast, purpose-built solar fridges and freezers use low voltage DC current from a battery charged by a photovoltaic panel, making their operation extremely cost-effective.”
To illustrate the rapid improvements being made in the field of renewable energy, the “Minus 40 Cold Saver” range needs only three to four hours of solar power each day and will run for the next 20 hours without a drop in temperature.
These fridges and freezers are built using a thick polyurethane insulation as a special feature. Otherwise, they look just like ordinary fridges with an attractive white coating on a varnished steel exterior surface.
These current technology fridges operate with a compressor powered directly from sunlight. Instead of storing electrical energy in a battery as was previously the case, the new ones store thermal energy in ice and a thermostat maintains the temperature.
Similarly, the World Health Organisation (WHO)’s prequalified version of solar direct-drive refrigeration (Vestfrost model MKSO44), commonly being used by hospitals for vaccine storage, uses the insulated “ice battery”, which maintains acceptable temperatures for up to five days, particularly in low-sun situations or when power is completely disrupted.
An intelligent fan enhances the convection circulation of the cold air and is operated by a small battery, which is recharged by solar power.
The direct current compressor and “ice battery” design makes this new generation of solar fridges a ground-breaking technology.
Traditional lead-battery solar refrigerators were expensive, short-lived (especially in hot climates), and environmentally unfriendly.