Heavy duty electric vehicles

There are about 250 manufacturers of heavy industrial vehicles worldwide but most do not make EVs. Between them they will make about 700,000 of these vehicles in 2010, with most participants having under $20 million sales yearly.

That is according to Dr. Peter Harrop of IDTechEx, Cambridge, UK-based company involved in global analysis, strategic advice and market intelligence of printed electronics, RFID, energy harvesting and their applications.

However, by 2015, he predicts the demand for heavy industrial electric vehicles will be comparable to that for light industrial/commercial electric vehicles.

“Potential sales growth of heavy industrial vehicles mainly lies outside the saturated market of forklifts where most are already pure electric vehicle,” says Harrop. “Several manufactures now offer lithium battery options, to get away from the tyranny of one battery set in use, one cooling down and one charging per vehicle. The rest are still powered by lead acid batteries.”

The growth potential comes because hybrid technology is of great relevance to heavy outdoor vehicles, where it is little used at present.

“It is likely to be eagerly adopted, now it is both affordable and reliable, because of the need for high power delivery for long periods of time and frequent stop-start,” Harrop says. “A hybrid heavy electric vehicle for relatively long range outdoor use outperforms the traditional type while providing cost saving as well.”

Electric vs. pneumatic hybrids

There are several options, he notes. Some heavy electric vehicles use diesel electric powertrains reminiscent of those in locomotives and large ships and some use a design more similar to the power train of a hybrid bus. On the other hand, hydraulic hybrids are similar to electric hybrids, but they store energy captured from braking not in batteries but in hydraulic fluid. The "accumulator" for the hydraulics stores compressed fluid which when released powers a hydraulic motor to provide power to the wheels of the vehicles during acceleration.

The weight of the fluid is a problem for downsizing to car powertrains, though attempts have been made. John Kargul, EPA's director of technology transfer, points out that hydraulic hybrids are 70% more efficient than traditional Class 6 trucks, compared to less than 25% efficiency increase for electric hybrids during a cycle of acceleration to 35 mph and then braking back to zero mph.

A manufacturer of these powertrains, Eaton Corporation believes they are well suited to inner city delivery or garbage collection trucks where vehicles are frequently starting and stopping. 50% fuel savings are available, according to the EPA.

By contrast, Fiat Group, a leader in agricultural and earthmoving vehicles under the New Holland and other banners, is developing electric powertrains.

On the other hand, a hybrid electric refrigerated truck can run the compressors for the refrigerated box off battery electricity, reducing idle time, but cannot do the same with hydraulic systems, observes Harrop. So called "hotel facilities" and auxiliary power for machines are provided by stationary hybrid military vehicles, even when the engine is not turning.

BAE Systems is a leader in these power trains and Afs Trinity Power Corporation has advanced hybrid power systems with fast ultra-capacitor storage.

Cost reduction is more easily achieved with electric traction. KPIT Cummins of India has just announced an affordable hybrid electric conversion for larger vehicles. As a result, Pike Research says the hydraulic hybrids are likely to grow within specific niches (garbage trucks, inner city delivery trucks, shuttle buses), but will likely find difficulty breaking out of those niches.

Other advances

Massachusetts Institute of Technology spinoff Levant Power Systems has shown that energy harvesting shock absorbers in large vehicles can each generate as much as one kilowatt of energy. Large vehicles have huge areas available for embedded photovoltaics for electricity generation and harvesting vibration and exhaust heat are very attractive too.

Work is proceeding apace with printed electronics and electrics and wireless actuators, sensor and even lighting.