By Johan de Villiers
Welcome to our second edition of our quarterly E-zine for 2022!
On a recent trip thru the Tankwa desert I was amazed at the amount of solar/photo voltaic installations in the heartland of the Karoo, as well as the massive uptake in wind turbines dotted all over the country, from Jeffreys Bay all the way to Sutherland and the West Coast.
This increase in renewable energy solutions removes a huge electricity load burden from the broken Eskom infrastructure in our country and contribute to a much greener future from a climate change perspective.
With the implementation of Stage 4 loadshedding in the country recently, this made me consider (once again!) the idea of going completely off-grid at home and especially the challenges one would face afterwards. In writing this piece, I came across an interesting MyBroadband interview with an energy expert, Christiaan Hattingh, in terms of the pitfalls and issues one should consider before making such an investment.
Most people I know currently use some form of backup power system or UPS, to partially compensate for the period of loadshedding before reconnecting to the Eskom grid. Once you consider cutting the cord completely to the grid, we are really talking about three primary components. Photovoltaic panels, Inverters and Batteries.
In its simplest form, solar panels generate electrical energy from the sun, which is then ported thru to an inverter. This converts the energy into usable electricity for general and household appliances. The excess electricity generated is stored in lithium batteries for when the PV panels cannot produce energy, such as night time or during inclement weather.
One of the most important aspects to consider is the output capacity of the inverter that you choose to install at home. For most home owners, cost effective inverters will only produce an output of around 5 kW to 8 kW. Now remember that Eskom delivers to most households a single-phase connection of around 13 kW, whilst your house is connected to the grid.
Once you start adding the full domestic load of pool pumps, microwave ovens, heaters, fridges, stoves, geysers, computers and air conditioners, the majority of household “off-grid” system will trip during peak demand.
So, the logic thus dictates that the entire household would have to have a major change in attitude and become far more aware of monitoring electricity consumption at home and especially to be conscious of high-power load appliances in the house.
Another issue to bear in mind, is that although South Africa is blessed with an abundance of sunlight, we do experience serious harsh weather every once in a while. Just think of the famous Cape Town winter storms. This can decrease your power generating potential by up to 20%, which further limits your domestic consumption and what extra energy can be stored in your batteries.
Hattingh recommends that for any home owner to ensure 100% off-grid capability, the system should be capacity oversized by at least two to four times your current electrical needs. This will compensate for dips in solar availability and negate changing your usage habits too much. When talking actual rands and cents, a household using 1200 kWh on average per month, should budget for such an off-grid installation costing around R 700 000 plus, excluding VAT. Note that a generator is optional and not included in that price.
Smaller systems will cost less, but obviously will not cater for your full peak demand electricity needs. Another approach is to continue to have a connection to Eskom at around R 115 per month, just in case your off-grid system cannot manage the load at specific instances or alternatively to pair your solar system with a generator.
Remember that the generator can charge the batteries during inclement weather as well, not just during high peak demand.
Households can use the generator to charge up the batteries on days when the sunlight does not provide enough energy to supply their home or charge their batteries to a sufficient level.
Below is a table that provides three possible grid-tied systems for households that use an average of 600 kWh, 900 kWh, or 1,200 kWh of electricity per month.
In conclusion, Hattingh also warns that the selling price of your home one day, may be affected by having no connection to Eskom at all, so also something to consider.
Until next time, thank you for your continued support of First Technology Cape Town!
Johan de Villiers
First Technology Western Cape