Sunny skies and cooking pots

Solar power holds much potential for Africa, where as many as 5m hectares of tropical forests are destroyed each year, mostly for firewood. So when Herman Warren saw a solar cooker designed in the US , he secured the rights to produce it in SA.

“In many parts of rural SA, households use wood as their main fuel source for cooking and heating,” says Warren. “And except for a very few who buy wood or who own a bakkie, most wood is carried by women and children on their heads.”

He says apart from destroying sensitive ecosystems, acquiring this type of fuel is time-consuming, cumbersome and unreliable in the rainy season. It also results in indoor air pollution, which can cause health problems.

“Since women and children are mostly responsible for the collection and transport of firewood, wood collection also prevents them from participating in other development activities.”

Yet SA has some of the highest levels of solar radiation in the world. Daily solar radiation averages 4,5kWh/m² compared to about 3,6kWh/m² in parts of the US and about 2,5kWh/m² in Europe and the UK. During October and November, SA gets about nine hours of sunlight a day.

“Harnessing the sun’s energy for solar cooking and heating in rural households not only has conservation benefits, but social benefits too,” Warren says.

The Sun Ray cooker is constructed mostly from recycled materials, such as plastic, and uses technology that focuses the sun’s rays onto pots which are placed inside the solar box.

The cooker works on the same principle as a greenhouse, allowing solar radiation in through the clear cover and trapping the thermal radiation inside. The result is a gradual rise in temperature. Regardless of the temperature outside, the solar cooker will heat food to a uniform temperature that is sufficient for cooking. The effect is amplified by the black base of the cooker and Warren recommends using black pots to increase the heat . With temperatures reaching up to 150°C , the cooker can work in the same way as a stove or oven, though it can take twice as long.

“A family could put the food on to cook while they undertake other household chores,” he says.

Weighing just 3,3kg, it can accommodate enough pots to feed four to six people at a time.

Because the Sun Ray cooker heats up to temperatures well above the 65°C needed to kill pathogens, there’s no risk of food contamination with the longer cooking times.

But at R850, the solar cookers are likely to be out of reach for most rural inhabitants.

“Studies conducted in Limpopo have shown that more than 75% of people living in rural areas would be willing to pay more than R40/month for solar energy, while 34% could pay even more than R80/month. We are looking to partner a development institution to see if the cookers could be subsidised or if a repayment plan could be arranged to make them affordable over time,” says Warren.

The company manufactures the cookers in a factory in Gauteng, with the capacity to ramp up production to more than 1000 cookers a month. It currently sells them online and in camping stores.

“The solar cooker also appeals to wealthier, eco-aware, bush-loving customers who enjoy hassle-free cooking while they’re out on safari,” says Warren.