South Africa needed to develop controlled charging strategies before it embarked on large-scale investment in electric vehicles (EVs), Council for Scientific and Industrial Research research engineer Paseka Mabina said during the recent South African Energy Efficiency Confederation conference,

He discussed the need for demand response programmes that should be initiated when a number of EVs entered the road network.

EVs are considered to be one of the technologies that will enable the Department of Transport to reach its target of reducing greenhouse-gas (GHG) emissions in the transport sector.

The transport sector contributes about 10.8% of South Africa’s GHG emissions, 91.2% of which comes from road transport.

Mabina noted that the South African government predicted that the country would have more than 2.9-million EVs on the road by 2050, about 25% of all registered private vehicles in the country.

However, he pointed out that, with a high penetration of EVs in a distribution system, it might impact negatively on the power system’s operation and control and, therefore, required demand response strategies.

The average EV charged between eight and ten hours, using 3.8 kW chargers, and the charging duration typically fell in the load peak demands of the grid, since charging typically occurred after 17:00, which put increased pressure on the grid and might drive up electricity tariffs.

Mabina said there was a need to accurately model the impact of EV charging on the demand profile using accurate data. He was currently doing research on the impact of uncontrolled EV charging load on the electricity distribution network.

His research so far has found that about 355 000 commuters use private vehicles to travel to work within the Ekurhuleni metro, which, should 25% of them switch to EVs, would put pressure on the power distribution system between 17:00 and 20:00.

Using Miniflex tariffs, he predicted that it would cost R1.1-million to charge 355 000 EVs in a day in the winter, should all the commuters switch to EVs. However, when shifting flexible loads such as EV charging to off-peak hours, the tariff could be reduced by 20% and cost R619 487 to charge 355 000 EVs in a day in winter, under controlled charging conditions.