HYBRID POWERTRAINS HYBRID POWERTRAINS gerald scheffels, iVT International

after years of hype, industrial vehicles with powertrains that offer the best of both worlds are finally starting to hatch. Will they devour the market or timidly infiltrate it?

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Engineers of innovative manager of Eaton Truck Group’s high-power density indeed! mobile drives must find This system emerging technologies division. According to the company, this rubbish rather appealing – not only “Once on site you can shut off the system not only reduces energy prototypes of many hybrid drives reduces engine and run the bucket and other consumption, but also doubles the shown at trade fairs go on to be systems on battery power until the life of the brakes. installed in refuse trucks. For good energy batteries need recharging. This could Eaton is also developing a hybrid reason, of course: if the vehicle consumption, be up to several hours. At that point, hydraulic technology system that moves in a stop-start manner and the engine automatically restarts completely replaces the conventional wheel slip can be excluded, hybrid but also and fully recharges the batteries in a transmission and driveline. Energy drives work particularly well. doubles the few minutes.” This system, adds is recovered, stored, and transferred It is now becoming hard to find a life of the Davis, is already in production and from the engine to the drive wheels vehicle OEM that is not considering can be found in utility and delivery using hydraulic pumps, motors and hybrid or other alternative drives. brakes vehicles and municipal trucks. other integrated components. There are many prototypes and real- Eaton’s hybrid hydraulic systems, “The initial project specification world trials, and suppliers are offering higher power capacity but called for a bent-axis pump, because Figure 4 (ABOVE): Volvo’s preparing for – or have already lower energy storage capacity than that geometry has better efficiency L220F hybrid features a begun – series production. It is their electric cousin, are scheduled at partial loads than an axial piston 50kW motor generator between engine and important news, too, that the fuel for commercial launch this year and pump,” says Brad Bohlman, business transmission cell may work better with a special will be seen in higher power classes development manager, Eaton’s Figure 3 (LEFT): AC drive kind of hybrid drive. such as refuse trucks, shuttle buses Hydraulic Operations’ advanced motors are the key change and other larger vehicles. For these technology division. in Cat’s D7E diesel hybrid Hybrid electric or hydraulic? applications, the company has “What we found, though, is that track-typr tractor For refuse trucks (Figure 1), town developed two distinct technologies, the system is typically operating at, buses and light delivery vehicles, both designed to capture the or near, full capacity so we were construction division has produced Eaton has developed hybrid electric vehicle’s braking energy, which is rarely able to take advantage of that an L220F hybrid wheeled loader that and hybrid hydraulic drives, and stored and then used for acceleration. extra efficiency. As a result, our has the potential for fuel savings of claims that it is the world’s only The first, Hydraulic Launch Assist production systems will use axial 50%. It features Volvo’s integrated manufacturer of both types of (HLA) technology, is designed as a piston pumps, which are a lot easier starter-generator technology, which hybrid systems considered viable for figure 1: Ideal for hybrid parallel hybrid system, to incorporate into a parallel allows the engine to be turned off today’s commercial vehicles. drives, the stop-start supplementing the conventional architecture because of the through- when idling (Figure 4). This mild nature of refuse trucks “The HEV concept is well suited and the steady energy use powertrain (Figure 2). Braking energy shaft capability.” hybrid measure alone will reduce for lighter vehicles that need to idle of auxiliary drives – for is saved in a hydraulic accumulator On-road prototypes of vehicles fuel consumption by up to 10%. to keep onboard equipment buckets and hydraulic and for several seconds, the system such as parcel-delivery trucks with Potential customers do not have to platforms, for example powered, such as bucket trucks,” – are ideal for energy delivers 300bhp from a motor that this drive system have shown that construction equipment OEMs. At powered by a Cat C9 engine wait very long to benefit from this says Scott Davis, business operations recuperation measures approximately 12x18in – fuel economy can be improved by Bauma 2007, for instance, producing 175kW. According to technology, as series production is 50-70%. Eaton has already produced Weyhausen, the German wheeled- Caterpillar, it will deliver 25% more scheduled for the end of 2009. more than 220 hybrid-powered loader manufacturer, presented an material moved per gallon of fuel, vehicles for testing and evaluation. Atlas AR65 with a mild hybrid drive, 10% greater productivity and 10% Partnering with OEMs According to Eaton, the next jointly developed with Deutz and lower lifetime operating costs. Suppliers are eager to respond to generation of hybrid-power systems Heinzmann, which supplied the In the D7E’s powertrain (Figure these needs and to partner OEMs. promises even greater efficiency. engine-control system. In this 3), the engine drives a generator to Eaton, in targeting the off-highway One embodiment is a series machine, the flywheel between the produce electricity that ultimately market, develops hybrid drives on hydraulic system in which a diesel 36.9kW diesel engine and hydraulic powers two AC drive motors its own or with OEMs. ZF makes use engine drives a variable-displacement pump is replaced by a compact unit connected to a differential steering hydraulic pump linked to a variable- containing a motor-generator with a system. A traditional mechanical displacement hydraulic motor rated power of 10kW and a peak transmission is not needed, because connected to the vehicle’s final power of 30kW. the variable-speed electric motors Google it! drive, or directly to the wheels. At the current development stage serve the function of a continuously This arrangement creates an of the Atlas loader, all functions on variable transmission. The drive is Gathering information on hybrid drives is a laborious task. infinitely variable transmission (IVT) the equipment side remain similar to the diesel-electric concepts Google responds to ‘hybrid drives’ with a six-digit number of “IVT will be a step up in efficiency hydraulically driven. The next step of diesel locomotives and Still’s hits. More comprehensive input might be gained at the from today’s advanced CVT systems involves the loader being powered forklifts. The electric drivetrain has National Conference of the American Hybrid Truck User Forum because it does not need a clutch to by a full hybrid-drive system. It will 60% fewer moving parts than the (HUTF), taking place from 14-16 October 2008, in South Bend, Indiana, USA (www.calstart.org/programs/htuf). However, the achieve zero driving force,” explains then be possible to temporarily D7R, while the electric system Forum mainly consists of fleet operators of on-road vehicles. In Davis. “You can disconnect the realise a strictly electric, and powers auxiliary components so April 2008, Frost & Sullivan published a Global Market Analysis engine from the final drive simply therefore emission-free, operation. that no engine belts are needed. of Plug-in Hybrid Electric Vehicles, giving a general survey on the by adjusting the pump and/or Caterpillar is adopting a similar Volvo presented a hybrid market potential of hybrid drives. For ongoing technical motor displacement to zero.” strategy, introducing an electric- solution for heavy-duty vehicles in information, iVT’s sister magazine, Electric & Hybrid Vehicle drive track-type tractor that will be 2006, and is currently delivering six Technology International, presents details across various transport Hybrid drives in off-highway ready for sale in selected markets double-decker buses, run entirely on sectors. The Oct/Nov issue of iVT will feature in-depth case Hybrid concepts have been during the next year. The D7E is in hybrid engines and transmission, for studies of the latest off-highway vehicles with hybrid drives. engineered as prototypes by several the 27-tonne weight range and is a year’s test in London. Now its

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exceptionally high power density. The electric motor can be controlled over a CANbus interface and depending on the application, the torque, speed, voltage or position can be regulated. A protection and safety concept provides for secure handling up to 750V.

Regenerative braking with hydraulic bladder accumulators In the field of hybrid drives, Rexroth can benefit from its huge experience in hydraulics and from the know- how of Bosch’s automotive business in designing alternative drives. The company has already developed several hybrid concepts for off- highway vehicles, such as the hydrostatic regenerative braking figure 6 (ABOVE): Rexroth’s HRB system, system (HRB, Figure 6). The which allows for a hydrostatic regenerative braking, can even be retrofitted engineers have opted for a hydraulic hybrid, using bladder accumulators figure 5 (BELOW): STW has developed a diesel-electric hybrid drive for agricultural to store the energy – a concept that and construction machinery can also be successfully applied to large hydraulic presses. The energy generated during braking is stored in the accumulator, and during the next acceleration event, the accumulator supplies enough energy to reduce the load on the combustion engine. Rexroth figure 2: Eaton’s Hydraulic Launch is currently developing a parallel Assist technology (HLA) is designed HRB for vehicles with a mechanical as a parallel hybrid system drivetrain as well as a series HRB for those with a hydrostatic transmission. of the experience that was gained in The former can even be retrofitted. the passenger car and commercial Development of battery systems Simulations indicate that fuel vehicle markets (see page 70). savings of up to 25% are possible – Sensor Technik Wiedemann, in this is going to be validated during Crucial to the operation of hybrid drives is the battery co-operation with other project technology used for recovery energy – OEMs and suppliers are field tests in Berlin and New York members, has also developed a waiting for increased power and/or energy density. Ricardo has with prototype garbage trucks later hybrid drive system, called therefore announced the establishment of its Battery Systems this year. Similar savings are powerMELA (Figure 5). This is a Development centre to offer turnkey engineering and expected by the series HRB, for diesel-electric drive designed for use development of complete high-voltage battery-pack systems instance in forklift trucks. in construction machinery, and for hybrid, plug-in hybrid and electric vehicles. A 10-tonne lift truck needs only a agricultural, service and community The facility will feature three Li-ion-capable development 20-litre accumulator to store the vehicles. Its open electric network chambers, large HEV/EV-capable battery cyclers and energy. Furthermore, Rexroth has can be extended to drive auxiliary equipment to facilitate the development of battery systems in patented a solution to integrate the simulated vehicle environments. The centre will be used to devices and external machinery. A working hydraulics of forklift trucks validate Ricardo’s design, analysis and simulation of advanced battery for energy recovery can also high-power battery packs. Projected to grow to a staff of 32, it into its series HRB system to increase be included. will focus on engineering complete Li-ion and nickel-metal- energy savings. The components are developed hydride (NiMH) battery-pack systems (as opposed to the especially for rugged conditions and development of battery cells). Hybrid triples extreme operating temperatures Prototype pack systems will undergo exhaustive development. Hybrid is the Greek word for mixed, from -40 to +85°C. The motor/ Each will feature high-capacity EV/HEV-capable battery cyclers, so any drive with more than one generator is offered in various power high-voltage instrumentation, hardware-in-the-loop systems power source can be described as a ranges, from 20-200kW. The 125kW and other equipment to enhance development in simulated hybrid – for instance, a forklift drive machine has a nominal speed of vehicle environments. Once a battery-pack design is verified, with fuel cell, supercapacitors and the battery system can be integrated into, and further 3,000rpm, a shaft height of 132mm, battery. Sounds over-engineered? In developed on, a vehicle in Ricardo’s adjoining garage facility. weighs 120kg and has a rated torque fact, it is not – and it is readily of 450Nm, representing an available. German fuel cell developer

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and integrator Proton Motor is figure 7: The drive concept ‘fuel cell plus supercapacitor plus battery’ is happy for customers to deliver readily available for forklifts – and the electric forklifts, preferably with drive systems fit into the battery case The classical elements and hybrid engine technology battery capacities of 560-700Ah, to its premises near Munich, and it will remove the battery and install its plug-in PM package (Figure 5) instead. “The package combines the advantages of fuel cells, batteries and supercapacitors,” says Proton If we look outside the traditionally ‘fire-driven’ engines, it’s possible that Most internet claims centre on Brown’s Gas (HHO). The process Motor CEO Felix Heidelberg. “As all other ‘elements’ could also play an increased role. Volvo is currently appears to use a modified electrolysis system to split water into its researching air hybrid technology, which will use braking energy to constituent hydrogen and oxygen parts, but when it comes to the components are used in their optimal work as a compressor, pumping compressed air into an onboard tank. energy requirements to do this, exact figures are hard to come by. operation range, the system offers The air motoring mode can then power the engine from the stored air With installation claimed to cost around US$100, some of the over 50% energy savings. An with or without burning fuel by using air injection to get up to speed. products for sale look downright dangerous. One company is intelligent energy management The internet is awash with books revealing how you can run internal promoting what appears to be a jam jar with an electrolyser inside. This system controls the power distribution combustion engines on water. Some claim to be using it to enhance is clamped somewhere in the engine bay, filled with water and supplied between the three main drive combustion in combination with another hydrocarbon fuel, while others with a current. The gas produced goes into the inlet manifold of a petrol components. The energy recovered claim it can be used as a fuel in its own right. It is an interesting subject engine with scant regard to the technical niceties like what would this during braking is stored in the for discussion. For a start, how would fuel be taxed if it falls from the sky do to combustion charge ratios, or how lambda sensors would react to supercapacitors and fuel for free? One thing is for sure, whoever finds a way to really run an the changes in exhaust gases. Despite this, there are many ‘endorsements’ cells, which provide peak in one minute. Long battery drives can even be retrofitted, and internal combustion engine on water could retire very wealthy. from satisfied customers, claiming increased economy (20-50%) and However, back in the real world, there is one thing all the suggestions that emission tests are being passed without the aid of catalytic “The package power when accelerating or charging times, expensive charging 2009 will see the series production about using water as fuel have in common: the maths never seems to converters. They seem impressed – and if it works, who wouldn’t be? combines the lifting heavy loads. stations and the associated logistics of hybrid wheeled loaders and track- add up. Perhaps this is why the mainstream engineering community However, with the greatest respect to all those working in this advantages of “Unlike batteries, which are therefore no longer needed. type tractors. Considering that fuel apparently refuses to take the concept seriously. fascinating field, without a giant leap forward it seems industrial vehicle have long recharge and The step from prototype to savings of 10-20% or more are Using a little squirt of water to take the heat out of combustion has compression ignition engine designers need not lose sleep just yet – fuel cells, discharge times, production is near or has already possible with comparatively simple been used for many years, and racing applications have been known to surely the diesel as we know it will remain with us for some time yet. batteries supercapacitors can be arrived, and the operators will be measures such as a compact motor- spray water onto an intercooler to reduce charge density. Research and And as far as our research suggests, there are no signs of an earth- quickly charged and able to choose from a much broader generator or a hydraulic bladder fine-tuning of these systems will doubtless continue, although industrial powered engine on the horizon either… and super- discharged for sudden selection of drive concepts in the accumulator, one question remains: vehicles may not be the ideal platform to demonstrate the technology. Jon Lawson capacitors” spurts of peak demand. near future. The fuel-cell forklift can why have we taken so long to get to They also allow the be ordered today, hydraulic hybrid this stage? iVT recovery of energy from dynamic actions such as braking.” In total, the system can provide The Prius pays off… over 30kW of peak power. Complementing the supercapacitors, the battery provides energy buffering Visitors to CeMat 2008 saw the European premiere of the Toyota Hybrid Concept Forklift – a truck using technology inspired by the Toyota Prius. As over longer periods. According to businesses look to reduce fuel costs and decrease CO2 emissions, Toyota Proton, users will derive notable Hybrid technology offers a practical, proven solution by capitalising on the benefits – including cost savings – advantages of existing fuel sources and infrastructure. The Toyota Hybrid from this new kind of hybrid drive, Concept Forklift is designed to cut CO2 emissions and fuel consumption which can be implemented with considerably while delivering the same overall performance as internal minimum effort. As well as the PM combustion models. package, only an emergency switch Developed in Japan by Toyota Industries Corporation (TICO), the Toyota and a load indicator have to be Hybrid Concept Forklift draws on the pioneering Toyota Hybrid technology. installed. After intensive tests, As part of the Toyota Group, TICO works closely with Toyota Motor Proton is now preparing for Corporation in the development of new technologies. production on a small-series basis. Previously displayed only in Japan, “There is great interest in the the Toyota Hybrid Concept Forklift market for fleets of 20 to 30 trucks combines the best of electric and with triple hybrid drives and we are internal combustion technology, taking currently expanding our production advantage of the strengths of each and assembly facilities. Our power source. The concept forklift customers are convinced that they combines an IC engine, electric save not only emissions but also cost generator and battery in a design that because they can make do without allows the engine to operate with battery-changing in two-shift optimum fuel/emissions efficiency. The forklift shifts operation,” says Heidelberg. automatically between battery The 10kW fuel cell delivers enough and engine mode, simultaneously energy to allow the three-tonne recharging the battery during forklift to operate for eight hours, operation. and hydrogen for a shift is refuelled

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