Most discussions of electrifying our transportation system avoid discussing the category of heaven duty machinery which has very high fuel demands which makes the lower energy density of batteries look very unattractive relative to diesel fuel. In the long run we need an alternative to diesel. Even bio-diesel is probably sustainable only at consumption levels much below current usage. A Finnish company called Visedo is producing electric drive trains for construction, agricultural, forest and other off-highway machinery based on electric motors which use synchronous reluctance assisted permanent magnet technology (SRPM). Visedo claims that SRPM motors offer smaller dimenson, lower weight, and higher efficiency compare to tradition induction motor (IM) or permanent magnet motor (PM). Heavy off road machinery is typically powered from from diesel engines which both drive the wheels and run various kinds of machinery for lifting, crushing, chipping, etc. The processing machinery is often run through a hydraulic drive train which requires very high power. Diesel engines are often slow to react to these fast-changing demands in power, and they therefore commonly run on high revolutions in order to be able to provide the needed power to the hydraulics. Visedo SRPM motors which which can supply maximum torque in millisecond even from zero speed allows much more efficient use of energy. Visedo’s SRPM motors are extremely rugged and can hold up to the high vibration environment typical of off road processing machinery. The image below shows hybrid stone crusher powered by a Visedo electric drive train in operation:
Visedo typically builds serial hybrid system in which a diesel engine running at a near constant speed turns a generator, which charges up a bank of super capacitors, which then drive the electric motor. The super capacitors are also charged from regenerative braking of the wheels and of the processing machinery. The fuel savings of the hybrid system are quite large and in some cases are nearly 50%. The heavy duty machines which use the diesel engines are huge fuel gobblers so that the extra expense of these hybrid drive trains can pay for itself in a period of 1 to 3 years.
In the case of a hybrid stone crusher designed by Visedo and a stone crushing and recycling company called Rockster the hybrid machine not only saves fuel, but also increases productivity by 40% because of superior handling capabilities compared to the diesel/hydraulic version of the same machine.
Unfortunately, hybrid machine’s which merely cut diesel fuel use in the range of 10% to 50% is not a long term solution to the problem of either climate change or fossil fuel depletion. In the long run (or perhaps even the short run if the worst case scenarios of climate change consequences come to pass) diesel fuel made from fossil hydrocarbons has to be eliminated. In the case of heavy machinery operating near the transmission grid battery electric machines are technically possible, though at present high battery costs and the high required frequency of recharging make them economically unattractive relative to diesel powered machinery. Continued improvement in battery costs and energy density could eventually change this situation.
For true off road application of heavy machinery which are relatively far from the grid another solution will be required. One possibility is fuel cells operating off of carbon emission free hydrogen (or possibly ammonia). One does not necessarily need a fuel cell in each machine to make this option work. You could potentially take a large solid oxide fuel cell and tank full of hydrogen or ammonia to your remote site and recharge the battery powered vehicles using the fuel cell. Again such an option is almost undoubtedly economically inferior to diesel machines at current oil prices, but it at least represent a route to technical feasibility of such off road operations in a post fossil fuel world.
Visedo is also producing hybrid drive trains for transportation applications, but not for passenger cars. Instead they are concentrating on application requiring high power such as hybrid buses and marine transport. I am guessing that in the passenger car power range Visedo electric motors are more expensive than more traditional designs, but offer advantages for high power applications which make them competitive.
rogerkb at energyevolutionjournal dot com