There is a long list of reasons why wind power is unsuitable for most home self-generation in South Africa, a renewable energy expert has told MyBroadband.
These include lower energy availability, more maintenance and monitoring requirements, and greater cost.
Aside from hydropower, the two major renewable energy sources used for utility-scale generation are solar and wind.
Solar has enjoyed widespread adoption in small-scale usage at homes and businesses but sees its production decline during inclement weather and disappear for most of the night.
Both hydro and wind power can produce electricity during both those periods, but the former requires massive dams, strong water flow, and complex pump station installations, making it unsuitable for small-scale implementation.
When it comes to wind power, however, a quick Google search for “wind turbine for home” will show numerous options available online — primarily in a vertical-axle configuration with a spiral turning mechanism.
South Africa has many areas — particularly along the coast — with plenty of wind, which might let some homeowners consider the option for their self-generating needs.
MyBroadband spoke to AWPower chief executive chairman Henri Hattingh about why this type of power was not more common.
The Cape Town-based firm installs solar and backup systems for households and businesses but has also received queries from customers who wanted to know whether wind generation was an option.
On an operational level, Hattingh pointed out that businesses and homeowners who had installed wind turbines typically complained about two factors — vibrations and high noise levels.
He explained that turbines that operated normally would create cracks on the wooden poles to which they are sometimes attached.
In addition, the physically-moving parts like gears are susceptible to wear and tear, requiring regular maintenance.
Vertical-axle wind turbine, also called a spiral wind turbine (left), and small-scale horizontal-axle wind turbine (right).
Larger horizontal-axle wind turbines have more stable mounting, but they must be attached to a pole extending tens of metres from the ground to catch the wind properly.
“You will have to get permission from the relevant authority, and your neighbours are not going to like it,” Hattingh said.
Aside from the additional significant installation costs such an installation would incur, a user would also need lots of vertical space, which might only be an option on large plots or farms.
Hattingh explained for this reason, most home wind turbine users installed turbines in turbulent conditions lower to the ground.
In such scenarios, frequent and fast fluctuations in wind speed can significantly degrade production and force turbines in the wrong direction, requiring the operator to reset them into the appropriate orientation.
Wind turbines also need to run at specific rotations per minute (RPM) to produce electricity — not too slow, and not too fast.
In the Cape area, in particular, owners have to bring the turbines down when the wind is very strong to avoid wear and tear or serious damage, like when the South Easter is blowing at high speed.
Hattingh said one scenario in which a small-scale wind turbine worked well was on a yacht.
On the open sea, operators don’t have to worry about turbulence and are always at hand to take the turbine down when wind speeds become dangerously high.
Small wind turbines also feature significantly lower energy availability factors (EAFs) than their utility-scale counterparts.
Hattingh said the EAF of a small-scale wind turbine was around 5-8%, while large wind farms could have up to 40% EAFs in ideal conditions.
Rooftop solar PV installations have an EAF of roughly 13-17% when considering that they cannot operate at night.
Hattingh said that although solar panels cost about R7,500 (excl. VAT) per kWp of generation, a wind turbine with equal capacity would cost around R20,000 (excl. VAT) .
That would be roughly the same cost as a 5kWh battery system, which could reliably provide 0.5kWp over 10 hours in the evening or during low solar production periods in overcast weather.
Therefore, batteries are generally a better investment for home users than wind turbines.
Many solar panels come with work-life warranties of 20 years or more, with some recent models going up to 30 years.
Hattingh said small-scale wind turbines were unlikely to come with anywhere near those warranties.
According to the UK site The Renewable Energy Hub, warranties on home turbines typically range between 2-10 years.
They also have many more mechanical moving parts — including gears — that require regular maintenance and replacement.
Hattingh said it was also likely that warranties could be voided if the operator failed to bring the turbine down to the ground when the wind speed was high.
The table below summarises the differences between rooftop photovoltaic solar and small-scale wind power, based on feedback from Hattingh and other energy-related sources.
Rooftop solar vs small-scale wind power
|Rooftop PV solar||Small-scale wind|
|Energy availability factor (EAF)||13-17%||5-8%|
|Environmental factors||Silent||Vibrations and high noise levels|
|Maintenance||Clean panels once or twice a year||Multiple moving parts can cause wear and tear and may require servicing|
|Work-life Warranties||20-30 years||2-10 years (The Renewable Energy Hub)|
|Monitoring||Little to none required||Must check for high wind speeds and bring turbine down if required|
|Space required||About 10m2 of roof or ground space per kWp||About 10m2 of roof or ground space per kWp |
Minimum 9 metres above the ground (US Energy Department recommendation) for horizontal-axle
|Cost||R7,500 per kWp, excl. VAT||R20,000 per kWp, excl. VAT|
*This article first appeared on Mybroadband following an interview: