EV emissions exposed

Bad news for early adopters of EVs: your “zero-emissions” car in Australia currently contributes about 30 per cent more CO2 to our atmosphere than a comparable petrol-powered model, thanks to the heavy coal dependence of the power grid from which you charge it.

Unless you’re in Tasmania. An EV in Launceston is a lot cleaner than an identical EV just across the water in Melbourne and we’ll explain why shortly.

But overall, as the UK’s Autocar magazine sought to demonstrate recently, most EV drivers are putting up with a fair bit of inconvenience and limitation for not much effect beyond setting a good example for the future. That’s because the gap between their EV and a modern diesel car is surprisingly small when it comes to total CO2 emissions.

Autocar’s conclusions are founded in the superior thermal efficiency of a state-of-the-art road-going oiler compared to a coal-fired electricity plant, by a margin of up to 10 per cent.

Indeed, so efficient are today’s better diesels that some come close to matching EVs, factoring in the gross thermal inefficiency of the average coal-fired power station.

Thermal efficiency measures effectiveness of a device -- be it a coal-fired power station or a fossil-fuelled vehicle engine -- in converting the potential energy in fuel into usable power.

Coal-fired power stations are more efficient than petrol engines but less efficient than many diesels.

UK government agencies measure the average coal-fired power station’s thermal efficiency at about 38 per cent. If things are any different locally, it’s not for the better.

A 2009 report commissioned by the Australian Energy Market Operator rates Munmorah in NSW at 33.2 per cent and Vales Point at 37.1 per cent. Victoria’s Loy Yang B plant achieves 28.8 per cent, Hazelwood just 24.4 per cent.

Among car engines, Mercedes-Benz’s current 2.2-litre diesel four tops the mainstream list for efficiency at 42 per cent; most modern petrol engines still only rate around 25 to 30 per cent.

This superior efficiency has always been the foundation of diesel’s appeal against petrol. Diesel fuel has a higher energy density than petrol, and the oiler’s intrinsic system of compression ignition makes it inherently more efficient at turning those joules into torque than its extrinsically sparked petrol counterpart.

Put simply, there are fewer electro-mechanical side doors through which the thermal and kinetic energy generated by the engine can dissipate.

Relative to its proportionally low output, the massive cloud of CO2 belching into the air over your average coal-fired power station is enough to cast a pall of doubt over the electric car as a solution to global warming, Autocar concludes.

“Burning coal (as some British power stations still do), turning it into electricity, sending it through the grid and then recharging a battery seems a rather complex solution when burning diesel fuel directly in the car will give almost the same efficiency,” it said.

Even taking into account the UK’s use of nuclear, hydro-electric and wind power to supplement the primary use of coal, gas and oil, the result is a surprisingly high CO2 number for EVs, all things considered.

Factoring in the high emissions of the plants feeding the British grid from which they charge, “zero-emissions” cars like the Nissan LEAF and Renault Fluence ZE indirectly emit an estimated 75-80g/km of CO2, according to Autocar.

The mag points out that’s not so far from a Ford Focus 1.6 TDCi Econetic, which emits 88g/km directly, rising to about 100g/km factoring in fuel refinery and transportation emissions.

That Focus isn’t available in Australia. Indeed, a glance at the federal government’s Green Vehicle Guide gives much more credence to petrol and petro-electric hybrid models than diesels. There are many of those in the guide’s top 20 cleanest, greenest cars before one oiler turns up.

Rob Murray-Leach, CEO of the Energy Efficiency Council, a cross-industry consulting and advisory body set up to assist industries on energy efficiency issues, says the Autocar case amounts to a bit of a furphy.

“It’s wrong is to look at such issues as if they’re static,” he told motoring.com.au. “This isn’t static. Right now, electric cars are quite pricey and electricity in some states is emissions intensive. But give it five to 10 years and the story will be totally different.”

For evidence of a complexity to the matter that Autocar fails to address, he points to Australia’s definitive document informing climate change policy, Professor Ross Garnaut’s Climate Change Review.

Commissioned by the federal government and first published in 2008, it saw its last substantial update in 2011. The total indirect emissions of an EV depend on the source of the electricity, which in Australia is driven largely by location, Garnaut points out.

Averaging out the emissions intensity of all Australian grids, an EV today indirectly generates about 30 per cent more CO2 than an internal combustion-powered car of similar dimensions.

But the picture looks different with a state-by-state breakdown.

In hydro-intensive Tasmania, that EV would generate about 85 per cent less emissions than its petrol counterpart. But in coal-hungry Victoria, it would generate about 60 per cent more.

“If there were a widespread shift to electric vehicles, transport emissions would be tied to the emissions from the stationary energy sector. As the stationary energy sector decarbonised, emissions generated by transport activity would decline,” Garnaut concluded.

The EEC’s Murray-Leach says the Australian grid has entered a period of profound change, of a kind helping to realise the potential of EVs to cut automotive contribution to the CO2 cloud.

“Right now Australia's electricity system is deeply inefficient. In coal generation most of the energy in the coal is lost as heat, further energy is lost in the poles and wires.”

Murray-Leach say many of these efficiency problems will ease with the current trend to local power generation.

“The heat can be used to warm and cool buildings, there are no transmission losses and the shift to more efficient lighting can get five times as much in the way of useful outcomes from each unit of energy.”

This amounts to energy (and money) better spent, including on EVs. Critical to this, however, are parallel rates of change to transport systems and electricity networks, Murray-Leach adds.

“Basically, electric vehicles will only be a small proportion of the fleet in the short term. But we could see a rapid transition start in the next five to 15 years.

“Simultaneously, we’re already seeing a change in the electricity supply from coal (particularly black coal) to cleaner sources like wind and gas. [At the rate Australia is adopting EVs], by the time they become a big part of the fleet, the overall electricity supply should have substantially lower emissions.”

Autocar concurs with him after a fashion, using heavily nuclear-powered France as a pointer to the net benefits of EVs once dependence on coal starts to diminish. On home turf, a Renault Fluence ZE is rated at just 12g/km.

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