Electricity + Control March 2018

ENERGY MANAGEMENT + ENVIRONMENTAL ENGINEERING

Inland waterways 2%

Losses are minimal (about 5%) and no emissions are produced in this process. This means that up to six times less energy is required to do the same mobility work. Electric vehicles are also very well suited for operating in traffic – no energy con- sumption when the car does not move and braking energy charges the battery instead of wearing the brake pads and disc. It is clear that electric transport makes sense and we should look at supporting our own energy gen- eration instead of importing our energy to power our transport sector. Reducing risk in a sector that our economy is heavily reliant on can only staba- lise and improve our economic production (GDP). We can do better. Thanks to the low energy consumption of the electric propulsion system and the high solar radiation we enjoy in South Africa (double the radiation compared to central Europe), we are in a position to benefit more than most countries by supplying our mobility energy needs with renewable energy. With transport costs gen- erally a high input cost to trade, this could provide much needed competitive advantage. Renewable energy is perpetually available, costs are decreasing and it could be decentralised. This means it can only get better and chances for supply disruptions are smaller. You can actually have your own battery charge station at home, at your busi- Combining suatainable energy and electric mobility

Air 14%

Rail 2%

Cars 49%

Trucks & light vehicles 29%

Buses 3%

Motorcycles 1%

energy efficiency of transport work will improve at least by four times or 400%. The harmful emissions we currently breathe in will be removed from our cities and limited to elec- tricity power plants or completely removed if we generate electricity from renewable sources like solar or wind. Electricity is generated locally, while liquid fu- els rely on imports. In 2014 (peak year) we had to pay $14 billion for importing our transport energy. Eskom currently has surplus electricity. It makes sense to promote the use of this energy in trans- portation and create incentives for the public in or- der to encourage vehicle users to make the switch to electric vehicles. The objective of using a vehicle is to produce mo- biliy work. A car is actually a mobility tool.The work of mobility is measured in passengers moved over distance (expressed as P.km) or tons moved over distance (expressed as T.km). To answer the question we consider a petrol car in traffic: The energy in the tank is ignited, causing the combustion gases to expand. This causes pistons to move rotating the camshaft which is connected to the wheels via a gearbox. Losses in the system result in only 15% of the fuel energy being availa- ble for motion. Most of this energy is lost as heat. Not so great. Think about it. Electric cars have electric motors that are more than 90% efficient. When energy flows from the battery (dc) it excites the windings in the motor (ac) via an inverter/controller to produce motion. How well does the internal combustion engine deliver kilometres?

Energy requirements for City (stop & go) Driving

Engine losses: 74% - 75% Thermal such as radiator, ex- haust heat, etc (63% 64%) Combustion (3%) Pumping (5%) Friction (3%)

Parasitic losses (6% - 7%) (e.g. water pump, alternator, etc)

Power to wheels (14% - 16%) Dissipated as: Wind resistance (4%) Rolling resistance (4% - 5%) Braking (6% - 7%)

Drivetrain losses (4% - 5%)

Idle losses (6%) (In this figure they are accounted for as part of the engine and parasitic losses)

Electricity + Control

MARCH 2018

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