Can hybrid EVs replace diesel cars?

Are the new European regulations and test procedures for diesel emissions adequate? Has the problem been solved?

Yes and no. New regulations are in place that require road-condition emissions testing of new model vehicles, but they only apply to prototypes, not to mass-production models. That leaves the industry plenty of scope for real-driving emissions to exceed those of the prototypes tested. The regulations specify a phased-in approach in which mass-production models will eventually be tested under real-driving emissions conditions, but not until 2018-19 at the earliest.

Why is there a go-slow approach?

It's driven by industry lobbying to avoid near-term costs, which results from senior corporate management's focus on quarterly financial results. In my view, car-makers are harming their own medium-run interests by resisting more stringent testing. A strong real-driving testing regime introduced immediately could have restored confidence in the industry's ability to build low-emission diesel cars – an ability which it does in fact have.

Do diesel engines have a future in automobiles?

In technical terms, yes. There's a potential to further improve the efficiency of both diesel and gasoline-powered internal combustion engines (ICEs) by about 30 percent, with a corresponding reduction of CO2 emissions. And nitrous oxide and particulate emissions can be reduced nearly to zero by adding properly dimensioned exhaust-stream scrubbers and filters.

But for market reasons, the future of diesel isn't looking good. First, the public has lost a lot of confidence in diesel powered cars. People aren't sure diesel engines will be allowed in inner cities for much longer – partial bans are already in place in some cities.

Second, the price advantages of diesel vehicles are fading. For one thing, diesel cars are inherently more expensive than gasoline cars, by about €1,500 each, because diesel engines have to be built more robustly to withstand higher temperatures and pressures.

And in some jurisdictions, such as France, the favorable tax treatment of diesel compared to gasoline has been ended. Diesel car sales have dropped off in France as a result. That shift is likely to be repeated elsewhere.

More importantly in the medium term, the price of hybrid and electric vehicles is declining. Battery costs are shrinking much more quickly than was anticipated only a couple of years ago. We estimate that electric cars will become cheaper than cars with internal-combustion engines across the board around 2025 – maybe sooner.

Before that time, as long as batteries are fairly expensive, we may see increased use of hybrid electric vehicles equipped with small and efficient internal combustion engines called "range extenders” whose only function is to recharge batteries, so cars can drive longer distances without recharging. 

For all those reasons, I think far fewer diesel cars will be sold the further we get into the 2020s. Big trucks may be an exception, but there as well, there are prototypes of self-driving battery-powered trucks already on the road, and those could make diesel engines uneconomic eventually.

What are the pros and cons of hybrid electric vehicles with small internal-combustion engines that serve as range extenders?

Range-extender hybrids would be a good transition technology for the time until batteries have become cheaper, and a dense enough network of recharging stations has been built. For example, one version of the BMW i3 [pictured at top] has a range of around 200 km from its fully charged battery, plus a gasoline-fuelled range-extender engine that gives it another hundred km or so. The range-extender engine allows for quick refueling on longer trips. But the vast majority of daily trips are urban trips shorter than 50 km, so most of the time, plug-in recharging is enough.

Hybrid EVs with range extenders provide a good combination of low running costs, air quality advantages, and flexibility for longer trips. At the current price of batteries, it probably doesn't make sense to make pure EVs with 400 km ranges, given that few car trips are that long. For now, it's probably cheaper to build hybrids with range-extender motors.

So why aren't more hybrid cars with range-extenders being built and sold?

It's a bit mysterious. I think it's partly due to misaligned financial incentives in the regulatory system. There's a lot the government could do to improve those incentives.

And in part it's due to internal corporate politics. There's an internal battle between ICE groups and EV groups within the big carmaking corporations. The groups responsible for designing and making ICE-engine cars don't want to lose their jobs, and they're still the dominant majority. They're pushing back against moves toward electric vehicles, which are being driven internally by separate technical groups responsible for EV technology.

Government should push for electrification by introducing mandatory quotas for EVs, which would cause those internal debates to largely disappear. Carmakers would have to build EVs regardless of internal corporate politics.

Are electric vehicles the way of the future?

Yes. In the long run, EVs will certainly be the cheapest way to build an automobile. They have far fewer moving parts than ICEs, by two orders of magnitude, so they're simpler and more robust.

In the interim, there are concerns about jobs. ICE production jobs and EV production jobs aren't the same. But range extenders would help reconcile this, during the interim period until about 2025. You'd need both types of workers – some to build the range-extender ICE engines, some to build the electric motors that directly power the wheels.

Suppose governments were to require all new cars built starting, say, 2025, to have electric motors, leaving car-makers to decide between hybrid range-extender or pure EV technology. Would that be technically feasible?
Yes. There are no technical reasons why that couldn't be done, and no cost reasons either. In climate policy terms, and in economic and geopolitical terms from a European perspective, there would be significant benefits.

Peter Mock is managing director of the European bureau of ICCT, the International Council on Clean Transportation. ICCT was the organisation that discovered and tipped off US environment agencies about Volkswagen's diesel emissions cheating by testing car emissions under real-world conditions.