From Cape to Knysna – an EV journey


A Case Study


By Henri Hattingh, Executive Chairman AWPower, AWCape & Applico group



After living with a fleet of electric vehicles (EVs) for more than a year, we are now convinced, as a user, that EVs will replace conventional petrol and diesel-fuelled vehicles in the short- to medium term, much like mobile phones replaced landlines.

What makes this choice of transport even more attractive, is the fact that EVs can be charged with solar PV generated electricity which, if correctly configured, will reduce the direct running cost of an EV to almost zero.


The first generation of EVs were typically designed for commuting, but newer models are adapted to highway cruising, and with the advancement of a national network of grid-tied charge stations in South Africa, EV travelling is becoming popular.

Looking at the latest Porsche Taycan, Jaguar iPace and Mini, one can understand that they will become popular, but at a price. The trend-setting BMW i3 is an example of an EV that is becoming more affordable if bought as a used vehicle. If charged by solar PV generated electricity, the business case for driving an EV, and especially the BMW i3, is becoming very attractive.


This brings us to our case study: Our second trip from Cape Town to Knysna in a BMW i3, this time in the latest 120Ah (42kWh). Our previous trip to Knysna was in a 94Ah (33kWh).


The BMW i3 is designed to cruise comfortably at speeds between 90 to 120km/h, although it can reach about 150km/h, with rapid acceleration from stand-still and overtaking, which reduces some of the tensions that go together with driving a diesel vehicle such as a Mitsubishi Pajero. Energy consumption increases steeply as the speed goes up, so we decided to set the cruise control at 120 km/h. Our log is shown in the table below:


It is significant to note the following:

GridCars charge stations: We charged our EV at various charge stations deployed by GridCars along the main route to Knysna. These charge stations are tied to the national grid and vary in capacity between 30kW to 60kW DC. In theory, the 60kW DC charger will charge a battery that has been depleted by 30kWh, in about 30 minutes, but the rate of charge is not linear, tapering off from about 80% State of Charge (SoC) to protect the EVs batteries.


Charging time can be reduced by charging only to about 80% SoC, as the initial 80% is at maximum charge rate, thereafter it slows down to protect the EVs batteries. There are enough GridCars charge stations along the main routes to have frequent but shorter stops.

GridCars has a mobile app that keeps you fully informed during and after each charging session


Home charging. Once at our destination, we could charge the EV with the mobile charger that is supplied with the vehicle, and it can plug into a normal wall socket (15A), allowing the car to be charged at a switchable rate of 1.2kW, 1.5kW or 2kW. Charging this way from the grid takes much longer, but it is less expensive than the GridCars highway option.


Cost of electricity is about R5.88/kWh at the GridCars charge stations (you pay for the convenience and rate of charge) whereas the maximum domestic rate at Knysna was R2,50 per kWh.


Energy consumption of the BMW i3 on the Cape to Knysna trip was an average of 20.3kWh/100, providing an electric range of approximately 200km. However, in city-driving we normally achieve an average consumption of about 14kWh/100km.


Solar PV as a source for charging an EV will bring the cost right down to almost zero, depending on the size of the installation. When using the mobile charger that comes with most EVs, a 5kW residential solar PV system would be sufficient, however when 3-phase power is available, larger 3-phase 22kW (and upwards) AC charging stations are available for home and office use. And remember, when installing a commercial solar PV system with charging stations, tax incentives for solar PV may result in a 100% tax-deductible depreciation allowance in the year of installation for registered businesses Read more here.


Interested to learn how you can REDUCE your direct running cost of the EV to almost zero?

On 19 October at 11:00, we will host a FREE webinar to discuss the planning, installing, and operating a solar PV system for residential and commercial use, including charging an EV, that would normally result in zero direct running cost for the EV.


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