Categories: Motoring

The electric car: not squeaky clean

An electric car is environmentally expensive to manufacture, and its ‘fuel’ is only as clean as the nearest power station.

Only two plug-in electric cars are currently available in South Africa: the Nissan Leaf, which sells for about R500 000, and the BMW i3eDrive, for about R612 000.

Overseas, however, electric cars are selling in respectable quantities in big cities.

Most people think an electric car is completely green, but that’s not quite true. This can be understood by looking at how greenhouse gas emissions from different vehicles are usually compared. Three comparisons are used.

Tailpipe emissions
A typical 1,5-litre petrol engine car will emit CO2 at a rate of about 140g / km. Similar-sized turbo-diesels will emit about 120g/km, and hybrids will emit about 85g/ km. The pure electric plug-in will score a round zero.

Energy source
The energy source in a piston engine is the fuel in the tank, while in the case of a plug-in, it is the power station. Emissions vary significantly between hydropower, solar power,
nuclear power and coal-fired power stations.

According to the US Department of Energy, a Toyota Prius hybrid and a Nissan Leaf plug-in electric will both pollute at a rate of 200g/ km if average US power station emissions are taken into account.

In California, where there are many ‘clean’ power stations, the Leaf’s pollution drops to 100g/ km, but Toyota’s level remains unchanged.

In Minnesota, where most power stations are coal-fired, the Leaf may pollute at a rate as high as 300g/km.

An article in the magazine Scientific American found that the time of day when charging takes place also plays a role.

In the US, many utility companies ring their coal-fired power stations onto the grid at night. Charging at this time worsens an electric car’s emissions. Charging during the day, when cleaner electric power sources are dominant, produces less pollution.

In some countries, coal-fired plants lack pollution controls, or they are not always engaged. Owning an electric car in such a country doesn’t make sense, but a hybrid could be the best compromise. South Africa has one clean atomic power station; the rest are dirty coal-fired facilities. About 77% of our energy needs are derived from coal.

Manufacturing
According to the Fraunhofer Institute in Germany, it takes more than twice the amount of energy to manufacture an electric car than a conventional one.

Batteries are the main culprit: it costs 125 000g of CO2 emissions to produce each kWh, so the manufacture of the 22 kWh battery fitted to the BMW i3e emits almost 3t of CO2.

An electric car may lose out in such a comparison.

Calculating the range of electric car

This calculation starts with the battery capacity, measured in kilowatt hours. Power (in kW) is energy divided by time, so that when you multiply power by time, the two time-terms cancel out and you end up with the fact that kWh is an energy unit.

The Nissan Leaf has a 24 kWh battery, meaning that any combination of kW extracted
from the battery multiplied by the time taken in hours that equates to 24 is within the battery’s capability.

Using full power will deplete the battery in one hour (24 x 1 = 24). If you drive more slowly and use only 12kW, you can travel for two hours (12 x 2 = 24). At low speed, using 6kW will enable you to travel for four hours (6 x 4 = 24). The claimed range is 172km.

The car has comprehensive instrumentation to keep you up to date with the battery’s condition, as well as the distance you can cover at your present speed before the battery requires a recharge.

Jake Venter is a journalist and a retired engineer and mathematician. Email him at jacobventer77@gmail.com.

Recent Posts

The care unit that treats neglected horses and donkeys

The Highveld Horse Care Unit cares for neglected equines. Farryn Day of the unit says that a lack of education…

3 hours ago

Indigenous crop seed bank for North West

The Department of Agriculture, Land Reform and Rural Development (DARD) recently expanded its seed bank project to the North West.…

3 hours ago

EU and US reach agreement on hormone-free beef imports

In a bid to defuse transatlantic trade tensions, the EU last week agreed to allow US farmers a larger share…

5 hours ago

How to sell your wine in a changing market

The future of wine is evolving and the industry has to adapt in order to survive and flourish. This is…

1 day ago

SA’s sugar industry is in a meltdown

It would not be fair to say that the dramatic unravelling of Tongaat Hulett these past weeks was caused solely…

2 days ago

Second SONA of 2019 lacks detail on implementation – analysts

President Cyril Ramaphosa’s second State of the Nation Address (SONA) of the year in Parliament on Thursday has been met…

3 days ago

This website uses cookies.