Since Rudolph Diesel invented his compression-ignition engine in 1897, it’s been through a technological transformation. But despite efficiency and power gains the original principle remains the same and the chemistry remains inescapable: we are still burning a fossil fuel to make a reciprocating engine work.

There are those who see no other way. An eminent guest speaker at DAF’s recent engine seminar in Eindhoven, Prof. Dr. Franz X Moser of AVL List GmbH, was unequivocal on the future of diesel. He declared, “In the foreseeable future there is no alternative to diesel-based power units for heavy commercial applications.”

How foreseeable the future may be is a moot point, but any drive away from diesel, will be generated by forces of availability, price and environmental concerns. Right now diesel is the best show in town, but what’s waiting in the wings?

It’s a gas

Nick Blake, Sales Engineering Manager at Mercedes-Benz UK’s truck division doesn’t need an oil crisis to make him consider the alternatives.

Harking back to his GCE chemistry lessons he reminds us, “The chemical formula for diesel fuel is C₁₂H₂₆, and the numbers speak for themselves. Most hydrocarbon fuels have a 2:1 ratio, or thereabouts, and unless we move to a low-carbon fuel stock, our opportunities for significant improvements in emissions are limited.”

So those who are searching for a practicable lower carbon fuel stock may be doing so with an eye to the future in more ways than one. The next emissions villain to be targeted is widely known to be CO₂, and therefore R&D into gas engines may see a resurgence.

CNG and LPG are known to work, but they have infrastructure, storage and efficiency issues. But there’s no denying the low carbon advantage of methane (CH₄), which has the potential to cut carbon by 60% with little effort.

Hybrids

Parallel hybrids have come a long way in the last few years and big improvements in battery technology have come with them. They are working their way up the weight range and have escaped from the van sector. Iveco’s Eurocargo Hybrid has been available at 12 tonnes for some time, and Renault’s Premium-based Hybrys stretches the idea to a 26-tonne 6×2 rigid.

As DAF’s Marketing Director, Tony Pain observes, however, “The manufacturing costs are so high (light hybrids are typically double the cost of an equivalent diesel) that we decided to offer our 12 tonne LF hybrid on lease to try and unlock the market.”

Even with this incentive, they have not made much of an impression on the operating industry just yet.

Regenerative

Many truck makers are taking a long, hard look at the peripherals that sap an engine’s horsepower, like compressors, alternators, water pumps and the like. DAF’s researchers are looking at three areas for either cutting, or recycling, this wasted energy. They believe that redesigned regenerative brakes will be powering these auxiliaries, and, together with exhaust heat recovery, they will be the key to many efficiencies over the next 30 years.

The recovery and conversion of waste heat to re-usable energy, possibly via steam, is also on the table. It’s a waste-not-want-not philosophy, and it’s aimed at helping to squeeze even more efficiencies from Rudolph’s invention.

Electric 

Up to now, the issue for pure electric vehicles has been the lost payload caused by lugging around heavy batteries.

Even though the weight and size of batteries needed to move a given load is reducing all the time, it’s still suited to light commercial vehicles, and the lighter the better. The physics don’t stack up much higher than a 2.6-tonne van. With current battery power, a 7.5-tonne truck would need to carry 2.3 cubic metres of batteries that weighed 4,700kg. Clearly a self-defeating scenario.

To stretch the point to ridicule, a 44-tonne long distance tractor trailer, that currently uses 990 litres of diesel weighing 836kg, would be in even worse shape. Pure electric power for this truck would demand 26 cubic metres of batteries that weighed 52 tonnes. These figures depend entirely on the efficiency and recharge capabilities of automotive batteries.

The notion of a 2.6-tonne van was a non-starter just a few years ago. The target’s getting bigger, but you still need a sniper rifle to hit it.

The holy hydrogen grail

What engineers would dearly like to be able to call on is the technology that is frustratingly buried away in the hydrogen fuel cell, which uses that plentiful gas to generate clean electrical power. The first hurdle was making it work, and a number of manufacturers and battery companies collaborated to solve the technology issues.

That’s been achieved, and there are fuel cell buses running in San Francisco, Hamburg, Shanghai and also in London, where a small fleet of Daimler Citaro buses operate. So, it can power large vehicles, and from an environmental perspective the emissions are as clean as it’s possible to be with just water vapour and heat coming out of the exhaust pipe.

Where’s the glitch then? Money. The cost of bringing this type of propulsion unit to market, in any vehicle, is eye-watering. They make hybrids look cheap.

More of the same?

Are all these avenues dead ends? We can only assume that the world’s manufacturers don’t think so, otherwise they wouldn’t be pouring billions into the various ongoing projects.

It’s certain that if any one of them cracks the financial conundrum that’s keeping the hydrogen fuel cell stuck in the development workshops, and gets it out onto the highway economically, their prize will be riches beyond counting.

Engineers are not standing by idle in the hope of a breakthrough, of course. Ron Borsboom, Chief Engineer at DAF Trucks says there’s a lot more to do with the diesel engine in the meantime. He says, “It may all now be about incremental gains in efficiency, but aerodynamics, thermodynamics, peripheral losses, and energy recovery are going to all add up to improved drivelines.”

As for the ‘utopia’ of a power unit whose emissions are just heat and water? The word’s literal translation is ‘nowhere’, but don’t give up hope just yet.

Photos: Top - Volvo's FE hybrid, middle - equivalent diesel, bottom - Rudolph Diesel.


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