Troubled GM Europe sticks to its green vision

The future for General Motors (GM) and its European brands Opel and Vauxhall may still be uncertain, but despite its high-profile financial problems the firm remains very keen to highlight its efforts to become greener.

Even as the expected sale of GM Europe to Canadian firm Magna was thrown into question this month, the company was holding a series of "EcoVision" open days at the Millbrook Proving Ground in Bedfordshire aimed at journalists and other influencers.

On hand were examples of the latest EcoFlex Vauxhall road cars, from the tiny Agila city car to the larger Insignia saloon. These EcoFlex models adopt various techniques to improve fuel economy, such as low-rolling-resistance tyres, longer gears and better aerodynamics, and are all powered by modern diesel engines. These fuel-saving tricks are not new – most manufacturers now offer green-labelled options of this ilk – but the Vauxhalls are remarkably good. We were particularly impressed by the Insignia EcoFlex, a large family car which sits two VED tax-bands lower than its identically engined non-EcoFlex cousin, offering a 136g/km CO2 rating while retaining excellent driving characteristics.

Beyond these short-term tactics, GM has also put considerable effort into developing what it calls a range-extended electric vehicle, to be sold as the Chevrolet Volt in North America and the Vauxhall or Opel Ampera in Europe.

The Ampera's batteries power a 111kW electric motor, which is the car's only source of motion. When the batteries run down, as they will after a claimed 40 miles of battery-powered motoring, the engine springs to life – but to power an on-board generator to create more electricity, rather than to turn the wheels directly.

This arrangement of using an engine to run an electric motor may seem complex, but it can be efficient as it allows the engine to run at its optimum rate rather than having to speed up and slow down as the car accelerates, brakes and changes gear. The car can also recapture a little energy when slowing down by using the motor as a generator.

The battery has a capacity of 16 kilowatt-hours, but to keep the cells healthy the car only uses 8kWh before switching to petrol power. This is not much energy – by comparison burning just one litre of petrol releases 10kWh. However, while a modern petrol engine converts about a third of the fuel's energy into useful work, an electric motor can be as much as 90 per cent efficient, meaning the car can travel further for each kWh liberated.

The Ampera can keep going as long as there is petrol in the tank, just like a conventional car, and GM promises normal road speeds and good acceleration. Interestingly, the petrol engine never actually charges the battery – charging requires a mains connection. This engineering decision was presumably taken to try to limit the number of charge/discharge cycles during the car's working life, to help the batteries meet their 10-year, 240,000km design goal. GM says charging from a 230V, 16A supply will take three hours.

Under the current EU test cycle, GM says the Ampera records a score of 1.6 litres per 100km – or 176 miles per gallon – and less than 40g/km of CO2 emissions. These are undoubtedly impressive figures, but they call the car's battery-powered range into question. The ECE R101 cycle includes five driving phases but covers a total distance of just 23km, which the Ampera ought to be able to achieve on batteries alone. So it is unclear why the car does not record zero emissions during the test. GM has not yet responded to a request for clarification.

The Ampera looks very attractive in the metal and, despite its US origins, is a good size for European roads, roughly matching the dimensions of the existing Astra hatchback. The production Ampera will go on sale late in 2011, with the right-hand-drive UK variant arriving in 2012.

Andreas Lassota, product marketing manager for electric vehicles for Opel and Vauxhall, says the aim has been to create a genuine replacement for a family's first car, rather than a second or even third-car option for wealthy families. "We have to deliver a safe vehicle, both in operation and in case of an accident," he says. "It also has to be affordable for the whole of its lifecycle, and we still want it to be fun to drive."

Unfortunately, Lassota has nothing much to add on the affordability side, dodging questions about the likely cost to purchasers, or the projected profitability of production. He is more forthcoming, however, on safety, explaining that the position of the battery has been chosen to minimise the likelihood of damage during an impact, and that the battery chemistry differs from the flammable Lithium cocktail that notoriously caused laptop battery recalls in 2006.

In parallel with work on the Ampera's petrol-electric "Voltec" technology, GM is pushing ahead with plans for cars powered by hydrogen fuel cells, which it suggests will be viable options in 2015 to 2020.

This is a medium-sized off-road-style vehicle that stores its fuel in three large carbon fibre tanks sited under the rears seats and in the boot. The hydrogen is compressed at pressures of up to 700 atmospheres.

The hydrogen gas is metered out to the fuel cell stack, which powers a 73kW electric motor driving the front wheels. The fuel cell converts the chemical potential energy locked up in the hydrogen into electrical energy without combustion or CO2 emissions. Instead, the fuel cell directly combines hydrogen and oxygen to liberate electricity and water.

Hydrogen is controversial as a fuel, due to the energy required to refine it from methanol or to electrolyse it from water. Some critics argue that hydrogen produced from methanol is worse as a road fuel than petrol, from a CO2 emissions standpoint. However, Dr Ulrich Eberle at GM's Hydrogen Propulsion Centre optimistically argues that producing hydrogen from electrolysis is an ideal way to capture the excess energy produced by wind farms on windy days, raising the prospect of genuinely zero-carbon hydrogen.

While the hydrogen controversy is a long way from its resolution, GM has succeeded in creating a usable vehicle, from an engineering perspective. We took charge of a HydroGen4 on a demanding hilly route and found it very easy to drive, being both responsive and reasonably powerful. As with the Ampera, however, cost will make or break this kind of car. According to Greg Archer, director of the UK government-funded Low-Carbon Vehicle Partnership, fuel cell costs need to fall by a factor of 40 from current levels to be cost-competitive with internal combustion engines.

Whether or not GM Europe can achieve this kind of cost reduction remains to be seen – as does the future of the company. Vauxhall and Opel are certain to be in new ownership by the end of the year, and new management will no doubt bring changes in strategy. But regardless of what happens to the company, many environmentalists will be hoping that GM Europe's green R&D programme plays a central role in the car giant's future.