Electric Vehicles: some back of the envelope calculations

By Owen Kelp, Brisbane-based principal at ACIL Allen Consulting

Given the declining demand for wholesale electricity in the National Electricity Market (NEM), experienced in the last few years, how much of an impact could electricity vehicles have?

Within my presentation to the EUAA National Conference in October 2013, I presented some figures on the potential electricity demand that could result from the up-take of electricity vehicles in Australia.

Whilst the electric vehicle (EV) and plug-in hybrid electric vehicles (PHEV) industry is still in its infancy, it is beginning to see significant growth – particularly in the United States, where it is estimated around 140,000 electric vehicles are now on the road.

In no small part is this is due to the release of the all-electric Tesla model S, which has sold an estimated 15,000 units since its release in June 2012. Other significant makes include the Chevrolet Volt (PHEV), Nissan Leaf (EV) and Toyota Prius (PHEV).

Whilst these other models have seen larger overall sales, it is the Tesla S that has really given market watchers pause for thought. A quick look through the Tesla specs, including 420km plus range, maximum power output of 310kW, 0-100km/h in 4.2 seconds, suggests performance that, to date, is unmatched from its rivals. It has been awarded a five-star safety rating and it even looks great in my opinion, unlike most other EVs.

In Australia, EV uptake has been much slower with less than 1000 vehicles on the road in aggregate. However, with technology development occurring at a rapid pace, this could soon change.

This then raises the question, given the declining demand for wholesale electricity in the NEM experienced in the last few years, how much of an impact could electric vehicles have?

According to the Australian Bureau of Statistics, 2012 Australian passenger vehicle fuel consumption for petrol-based vehicles was around 15,696ML, with average consumption of 10.9L/100km.

This is just petrol-based passenger vehicles – total vehicle fuel use was around double this at 31,800ML when you include diesel and non-passenger vehicles. [Source: Australian Bureau of Statistics, 9208 Survey of Motor Vehicle Use, Australia, 12 months ended 30
June 2012
].

Assuming a petrol energy content of around 44MJ/kg LHV (this varies quite a bit based on different fuel types), with a density of 0.7kg/L, gives an energy content of 30.8MJ/L.

From this, we can calculate the implied total energy consumption of petrol passenger vehicles of around 483 PJ (30.8 x 15,696/1000). Conventional petrol engines only convert about 17-21 per cent of the energy stored in petrol to power at the wheels, so the implied energy used at the wheels is around
20 per cent of that, at around 97 PJ.

Electric vehicles on the other hand are much more efficient, converting around 59-62 per cent of the electrical energy from the grid to power at the wheels, giving an implied electrical demand of 161 PJ (97/60 per cent) if we were to convert the entire petrol passenger fleet to electric. This equates to something of the order of 44,800GWh of electricity demand (roughly a quarter of current total NEM consumption).

The uptake of EVs in Australia has the potential to reverse the current trend of declining wholesale demand and be a strong contributor in the longer-term.

The Tesla S average energy usage is relatively high at approximately 206Wh/km due to its size and weight, however other smaller EVs have lower consumption levels such as the Nissan Leaf at 173Wh/km. However, there are losses within the battery itself such that actual energy used/lost per km travelled will be somewhat higher than these figures.

Assuming an effective consumption rate of 250Wh/km, each passenger car would be expected to consume something in the order of 3.3MWh per vehicle based on an average of 13,200km travelled per year. Not an insignificant figure when you consider that average household electricity consumption is around 7MWh per annum. At an average electricity price of $0.30/kWh, 3.3MWh would equate to an annual cost of $990 to run the car.

Origin Energy has an online comparison tool for calculating the fuel costs for various vehicle types: all electric, electric hybrid, petrol and diesel based on average kilometres travelled.

Having an electric vehicle sitting in the garage at home with a very large battery also offers the potential to use this as a storage device for a smart rooftop PV system which could potentially time-shift generation into peak periods. There are many possibilities here.

While we are not likely to see mass uptake of electric vehicles in the near future, technological advances are occurring more quickly and once a killer product hits the market – think the iPad when it was first introduced – the level of uptake surprises almost everyone. Its breakthrough products like Teslas model S that make people sit up a take notice.

While we cannot change our cars as easily as a tablets and e-readers, it will be interesting to see just what happens when the might of the larger car manufacturers is applied to electric vehicles.

This article was originally published by Watt Clarity on October 29, 2013 at
www.wattclarity.com.au.