Cape Town - A Rondebosch couple living virtually off the grid are not only running their suburban home off the power of the sun, but are generating a surplus of energy.
Dr Anthony Keen, a former lecturer at the University of Cape Town’s medical school, uses the excess power to charge up his electric car, a Fiat which he had converted near Pretoria.
“I can glide around the streets of Cape Town on solar power,” he says, although not for too long as it only does between 150km-200km before it needs recharging.
Keen and his wife Rosemary don’t have to worry about load-shedding, high electricity or water costs - in fact they haven’t had a power bill in years.
The couple resolved to become more energy-wise more than three decades ago after spending a year sailing on a yacht from Cape Town to the Caribbean and Scotland with their three children. They learned to live with very little water and electricity and be reliant on nature.
Soon afterwards they renovated their Rondebosch home and Keen put in a solar water heater which has been going strong for 31 years, never even needing maintenance. He recouped the cost of this investment after six years.
Little by little they reduced their energy consumption. They started using a wood burning fire from wood collected from trees being felled or branches falling. They insulated the ceiling, put in low energy lights and cover the pool for seven months in winter during which the pump isn’t run at all.
“Solar electricity is expensive so you need to reduce your household electricity as much as you can before thinking about renewable energy,” Keen says.
In 2008 he put up 20 photovoltaic panels on the roof with a total output of 3.8 kWh, a battery bank and what he describes as the heart of the system - an inverter which converts the power to useable mains power.
“The cost was considerable but it was a challenge to see how far one could take an ordinary suburban household and run it on solar power alone.
“The main expense today is the battery. They are not efficient and they use up a lot of energy,” Keen says.
Since he installed his system he has been experimenting with different ways of managing the energy from the panels, the battery and the grid and using them in the household to optimise the solar component.
“We are running the house almost entirely off solar. The only bit of electricity we use is for solar water heating top up in winter if we have several cloudy days in a row so there is an electric element in the geyser if you need it.”
They cook with gas but Keen is considering going over to an induction hob - cooking with electricity but much more efficiently which he hopes to run off the solar power system.
Keen said it would be rational to export the surplus energy they generate back into the grid but the City of Cape Town didn’t make it very attractive.
He was one of three households that took part in a pilot project run by the City feeding power back into the grid for about three years which ended last year.
“They were quite generous they gave us one unit back for every one we exported.”
Keen said now if you export back to the grid you had to have an expensive meter, pay extra fixed fees and were limited to a small amount you could feed back.
“You also have to buy more power from them than you feed back and that limits you.”
He said he understood that the city depended heavily on the profit produced from selling electricity to generate income which was why its financiers weren’t keen on the idea.
Keen has built a grey water system so that all the water used in the house can be used in the garden. Four rain tanks are used for topping up the pool in summer while a borehole supplies the garden.