The internal combustion engine is a major contributor to rising CO2 emissions worldwide, and some pretty dramatic new thinking is needed if our planet is to counter the effects. With its use increasing in developing world economies, there’s something to be said for the argument that the vehicles we use to help keep our inner-city environments free from waste, litter and grime should be at the forefront of developments in low-emissions technology.
There is of course a counter-argument: why should council-owned trucks, purchased to clean up the environment, have to be built to a higher specification – and cost – than those distributing the consumer products that will ultimately end up in residents’ waste bins? The closer the cost and performance margin between a standard diesel truck and a low- or zero-emissions alternative, the easier it will be to win the argument in favour of the low-emission vehicle.
Getting the balance right
It’s against these complex issues that I’ve been able to test the new Isuzu N62-150 Hybrid truck. It was originally designed and built to meet the needs of distribution operators in major Japanese cities, but I was interested in how the diesel–electric hybrid technology would perform in the demanding role of collection of waste and recycled materials in urban areas elsewhere in the world.
 The Isuzu N62-150 Hybrid truck uses a 150hp diesel engine, supplemented by a battery pack/electric drive motor feeding into the existing truck gearbox via the PTO outlet |
It’s interesting to note that Isuzu has trodden the well-established path taken by Toyota with its Prius (and its luxury car brand Lexus), in that a lower-than-normal horsepower internal combustion engine is coupled to a large-output electric motor powered by a high-tech lithium ion battery pack that is partially recharged during driving, thanks to a regenerative braking system. In the case of the non-corporately related Toyota programme, the Prius uses a petrol (gasoline) engine and a battery pack that allows for a limited use in all-electric mode (in heavy stop–start traffic) with the internal combustion engine switched off. Other previous attempts at hybrid truck technology – for example that previously adopted by MAN in Germany – followed the same basic principal. But the Isuzu Hybrid does not.
Instead, it shares the approach already widely adopted by municipal waste collection vehicles in Gothenburg, Sweden, which recognize that the most harmful scenario relating to exhaust emissions is when a conventional diesel truck is stuck in stationary traffic, with the driver impatiently revving the engine, waiting for the traffic to move off again. Isuzu engineers have been able to overcome this waste of fuel and source of drive-train wear by a combination of two components. The first is the already well-proven electronic shift technology fitted to an otherwise standard manual gearbox. This is given different marketing names in different world markets, but in English-speaking markets, Isuzu calls it EasyShift and it’s already a standard option on most conventional diesel Isuzus up to 13 tonnes gross weight.
The second element is an automatic engine cut-off and restart system. Again, passenger cars have been fitted with such a system to reduce emissions in stationary traffic, while the garbage trucks used by Gothenburg City Council have taken the idea a stage further, by utilizing battery packs to enable the bin lifter and packing hydraulics to function while the diesel engine is switched off during a stationary ‘work mode’ as well as in stop/start traffic. So why hasn’t Isuzu gone for an electric-only mode to enable the truck to be driven in stop/start traffic, or at a reduced speed by purely electric motor drive?
The answer is, I’m told, that while it is technically possible, Isuzu engineers were conscious of the need for any hybrid technology truck to retain as useful a payload as any normal diesel truck chassis. Incorporating a battery-electric only drive mode would require a much larger – and heavier – battery pack, which in turn would cost significantly more money to produce. In other words, it’s a question of balance.
 Artist’s impression shows how the hybrid components fit into existing diesel truck chassis layout |
My mission then, was to see if Isuzu engineers had got that balance right. Working on the assumption that most trucks used for waste and recycled materials collections, or other kinds of urban cleansing and street maintenance operations, would probably be expected to travel a considerable distance to and from the work site at normal highway speeds, any hybrid has to be at least as drivable as a conventional diesel truck – without losing a significant percentage of payload capacity.
Looking for wider markets
In the case of the Isuzu N62-150 Hybrid, Japanese operating conditions have dictated that the base chassis used is a 6.2-tonne gross weight model. This has now been Type Approved for use in wider markets outside Japan. A look over the chassis layout soon reinforces the view that packaging all the extra components needed for the hybrid system into a small compact truck is not an easy task. That Isuzu engineers have done so to a full production standard – within a weight penalty of just 200 kg – is one of the factors that makes this a landmark vehicle, provided, that is, that the end result drives as well as a conventional diesel-engined truck.
 What sort of applications? This Novarini satellite unit is mounted on a diesel-fuelled Isuzu chassis, but would work equally well on the N62-150 Hybrid |
Given unhindered access to a laden production N62-150 Hybrid model and the use of an automotive industry test track able to replicate all types of road conditions, my mission was to see if the technology could be caught out by unusual conditions, unsympathetic driving, or even outright driver abuse. Loaded to full maximum gross weight, the Hybrid was repeatedly stopped, started, driven on full throttle and driven both up and down far steeper hills than are likely to be found in any urban environment outside of San Francisco.
With a conventional truck drive train comprising of clutch and manual transmission, it would have been a matter of minutes before the brakes and clutch would have been fried and, chances are, the propshaft and the rest of the drive train damaged. Such harsh use could have created transmission oil overheating on a fully automatic transmission – and the normal service brakes would certainly have suffered. With the Hybrid, the combination of automatically activated electric motor ‘boost’ from standstill, the cushioning effect of the EasyShift transmission and the security of the regenerative braking system on downward slopes all combined to minimize any damaging side-effects, while actually making the driver’s job easier.
Clever technology
So how’s it done? The answer is through clever electronics. CANbus technology enables all the truck’s systems to ‘talk’ to each other. I already knew from previous experience that the electronically-activated EasyShift manual gearbox used on Isuzu trucks was ideal for urban environments, without incurring the power loss of fully automatic gearbox options. But what I hadn’t bargained for was the significant advantages in having that large electric motor to supplement the power from the 150hp diesel engine. Isuzu couples the electric motor input shaft into the gearbox by utilizing the existing PTO-mounting (power take-off mounting). A short secondary propshaft provides the ‘drive’ function from the motor into the gearbox when acceleration is required, but the energy is also passed back into the battery pack when braking.
The electric motor is mounted within the chassis rails, alongside the diesel engine drive train, while the battery pack is located on the left side of the chassis, within the wheelbase. As all the hybrid functions are ‘intelligent’ and automatic, there is no need for complex controls in the driver’s cab. The performance boost is significant, seamless and reduces the fuel consumption of the diesel engine, while there is no need for the hybrid to be treated in any special way.
Selecting a suitable application
So what can the N62-150 Hybrid be used for? And how much extra, over the price of a comparable diesel Isuzu, does it cost? The fact that the hybrid drive uses the existing PTO output mounting on the gearbox does suggest that any operations requiring hydraulic power are compromised – which, of course, when applied to waste and recycling operations is most of them! But these are early days. The Italian manufacturer, Iride, is able to adapt its engine pulley-driven PTO pump to suit the Isuzu Hybrid layout. It could also be the case that an electro-hydraulic capability could be provided using the hybrid drive electric motor, while it might be possible to engineer a mirror image PTO output position on the other side of the gearbox in the longer term – although this isn’t possible at present. A fully electric binlifter such as those produced by Ecoprocess in Iceland would be ideally suited.
 Photograph taken from the driving seat of the Isuzu Hybrid by the author prior to the start of a series of runs up a 25% (1-in-4) test hill, fully laden |
And price? This is often where the promise of new environmentally friendly technology evaporates, but in the case of the N62-150 Hybrid, the price differential looks set to be ‘around 7000 Euros ($11,000) over and above the price of a standard diesel chassis’– which, coupled with a long-term leasing arrangement on the battery pack, should at least enable hybrid trucks to be operated to a pre-determined budget.
What sort of applications would suit hybrid technology best? The obvious application is for satellite vehicles engaged on domestic and light business waste or recycled materials collections in heavily congested or environmentally sensitive areas. With a lower cost and lower unladen weight advantage (compared to small compaction-type units), the 200 kg Hybrid weight penalty is not an issue. Equally, maintenance and traffic management units sound like another natural application.
Isuzu is already one of the largest manufacturers of trucks and diesel engines for other applications. Developing a hybrid truck – and then putting it into production – is an indication that this technology is here to stay.
