In a recent State of the System update, Eskom indicated that its gas turbine stations, Ankerlig and Gourikwa, used 148-million litres of diesel in power generation in November 2014. The turbines use diesel fuel in a gasified form.

The National Energy Regulatory of South Africa limit (the maximum energy that Eskom may supply) for gas turbine generation at the time was 450 GWh a month. The two stations together generate 2.084 GWh and, thus, to produce 450 GWh, they would run for 215 hours running.

Eskom fuel consumption figures are 236 000 ℓ/h for Gourikwa and 425 000 ℓ/h for Ankerlig. Running for 215 hours, therefore, translates into 142.7-million litres, as claimed in the Eskom update.

In this scenario, Ankerlig would have used about 91-million litres of diesel in November 2014.

Gourikwa has a pipeline to the PetroSA refinery, in Mossel Bay. This, with tanker deliveries of three 50 000 ℓ fuel tankers a day and ten-million litres on-site storage would keep the station supplied with diesel fuel.

The question is how the fuel was supplied to Ankerlig.

Allowing for the on-site storage tank of 16.2-million litres, the balance of the fuel, around 75-million litres, would have had to be transported to Ankerlig by road tankers. Using 50 000 ℓ as the base case, this would still require 1 500 road tanker trips, or 50 road tanker trips a day.

The tanker would need to travel a distance of 40 km from Cape Town to Ankerlig. There would need to be about 30 minutes for loading and 30 minutes for offloading and one hour minimum for road travel.

If the above is correct, the total of 1 500 tanker trips seems impossible as it would require three fleets of 12 tankers, operating 24 hours a day. This would surely bring traffic on the R27 to a standstill.

However, if the above is not correct, how were Ankerlig and Gourikwa refuelled in November 2014? Did the two stations actually use 148-million litres of diesel? If not, how much did they use?

At the time of publication, Eskom had not replied to these questions.