From hybrids to ‘clean diesel’ and hydrogen to lithium-ion, greener vehicles are gaining momentum. Using electronic variable valve timing, dual-turbo forced fuel-mixture induction and increasingly complex ignition systems and other paraphernalia, the car industry is already making headway in squeezing more power out of smaller engines, with lower emissions per unit of horsepower.

Already on the roads in still small numbers are hybrids (mostly Toyota’s) integrating petrol engines into complex ‘parallel’ hybrid power trains. These combine the conventional combustion engine with an electric motor or motors powered by batteries recharged both by the engine and by generative braking systems. Up until September 2007, 1,188,255 Toyota hybrids had been sold worldwide since 1997

These ‘parallel’ hybrids offer better fuel economy in the urban settings where their owners mostly drive. Toyota’s Hybrid Synergy Drive technology will gradually become available right across the company’s light vehicles over the next three to four model generations.

Stop-start move

Meanwhile, more and more cars will follow BMW’s and PSA Peugeot Citroën’s lead with ‘micro-hybrids’, whose engines cut out automatically when the car stops, and re-start seamlessly at a press of the accelerator pedal, cutting around 10 per cent from urban cycle emissions.

The endgame of hybridisation might be the plug-in hybrid (PHEV), whose extra-capacity battery will take enough power from the mains to avoid petrol consumption altogether for typical commuting trips. And those batteries will also take a charge from the engine on longer trips, and theoretically, be able to feed electricity back to the grid. However, Toyota, which plans to produce the plug-in by 2010, claims to see hybrids as nothing more than interim technology.

Case for clean diesel

Diesel cars are still virtual strangers to the US market, but some observers believe European manufacturers like Mercedes are right to expect their ‘clean diesels’ –_which use urea-based exhaust after-treatment to meet US clean emissions standards (the world’s most stringent) – to overtake hybrids’ popularity over the next decade. A lot more of either hybrids or diesels would have a major impact on US oil consumption, especially if fuelled by the cellulosic ethanol or algae-derived biodiesel for which production processes are now in the early stages of research and development.

Hydrogen at a premium

While developers have made big strides in the past decade in reducing the size and improving the performance of hydrogen fuel cells, their still very high cost has so far limited implementation to small trial fleets, the latest being GM’s Equinox and Honda’s FCX Clarity models.

A greater uncertainty than the likely cost reduction potential of fuel cell stacks is the future availability of hydrogen to power them. Still costing around four times the price of petrol, hydrogen is impeccably clean at the tailpipe, but its overall emissions-reducing potential is entirely dependent on electricity generators increasing their renewable energy sourcing to power electrolysis.

Battery connection

In January, the world’s first dedicated lithium-ion production plant was opened in France by the US-French Johnson Controls-Saft joint venture. Battery-electric vehicles like Tesla Motors’ rapid, 200 mile-range Lotus-based roadster suggest that this technology might even be good enough to divert attention from hydrogen as the next wonder energy carrier. The US electric vehicle pioneer ZAP and China’s Youngman Automotive Group are reviving the 100-year-old US brand Detroit Electric in a joint venture to bring battery-electric cars to market by 2009.

According to Dr. Peter Wells, reader at Cardiff Business School and editor of Automotive Environmental Analyst: “Pure battery electric cars will remain a tiny niche within the market as a whole worldwide, limited by technology constraints and a regulatory framework.”

Electric limits

New Zealand and Israel have already pledged to put the framework into place for electric cars. Although plans for New Zealand are less clear, however, early this year Renault signed an agreement with its Nissan alliance partner and NEC to install their lithium-ion batteries in electric cars to be marketed in Israel, where the world’s largest network of recharging points is to be installed through a public-private initiative joining the Israeli government with California’s Project Better Place venture.

Proponents of electric cars should note that they can’t solve the problem of road transport emissions at a stroke. They depend on scarce renewably generated electricity for full effect. Last year GoinGreen, the UK importer/retailer of the battery-electric Reva G-Wiz two-seater quadricycle, quoted well-to-wheel CO₂ emissions, charging with ordinary electricity, equating to 63gms C02/km. That’s 71.5 per cent of the 88 g/km emitted by Europe’s least-CO₂ emitting car, the diesel Smart Fortwo.

A suitcase of carbon

At the wackier end of the new automotive technology spectrum, pending third-party proof of concept, is a ‘Greenbox’ unit developed by three Welshmen, under the name Maesanturio, and announced in mid-2007. They claim that their system could be fitted to a car in its current form (though it is around the size of a suitcase) and would capture and store 85 per cent to 95 per cent of a vehicle’s CO₂ emissions. The driver would exchange the unit’s cartridge system with every tankful of petrol or diesel consumed, at a dedicated depot.

CO₂ and NO₂ captured by each Greenbox would then be supplied to algae farms, which would use it to accelerate their supply of biodiesel or fertiliser feedstock. The system is said to have been tested and demonstrated over the past two years using a diesel engine at vehicle emission test centres, but no peer-reviewed papers or test data have been published.

Air power

One relatively simple, affordable technology for using grid power, and due to appear in working prototype form the end of this year thanks to Tata Motors’ investment, is a compressed air-driven power train patented by the French inventor Guy Nègre, which promises a range similar to that offered by lithium-ion battery packs.

A question of demand

Global sales of new cars and light commercial vehicles will exceed 90 million by 2020, a 62% increase over the year 2000 total, according to automotive industry forecast company R. L. Polk.

In the UK, alternatively-fuelled vehicle sales were up from 9,439 units in 2006 to 16,640 in 2007 – still less than 1% of the market, – and many of the pioneers of zero-tailpipe emission cars are small companies with scarce capacity for expansion. Compared with those UK figures, sales of battery-electric, hybrid and other non-petrol/diesel cars will grow more slowly in the more price-conscious Asian markets, which will account for most of the global car market growth of the next 12 years.

In terms of global car impacts, the most radical technologies and more widespread interim fuel economy solutions will need to be globally deployed on a large scale to offset the sheer volume of car demand growth that is forecast between now and 2020 (740% in China, according to R.L. Polk).