Hybrid tractors – a look at the future?
You’ve heard of hybrid cars which combine electric and petrol power.
How about a hybrid tractor?
Case has developed a tractor that is powered by a diesel engine and has a transmission that incorporates two 50kW (67hp) electric motor/generators.
Currently very much a development project, the ProHybrid EECVT is loosely based on a Case MXM tractor and draws on technology from the Steyr continuously variable transmission – CVT – now used in Case’s CVX tractors.
A standard CVT combines mechanical and hydraulic drives to initiate stepless ratio changes.
This new hybrid system introduces electrical power into the driveline in place of oil pumps and motors but retains the mechanical aspects of the more conventional setup.
When running in normal conditions, one of the motors acts as a generator providing electrical power to the other which acts as a motor.
Similarly to a standard CVT, the system uses a greater proportion of mechanical drive as speed increases.
Pumping out a maximum of 160hp, the diesel engine provides the power for both the mechanical drive and the electrical system.
Excess energy that would otherwise be wasted is stored in a large battery that sits on the tractor’s nose in place of a front weight.
And it is this feature that is said to be the main advantage of the system.
Because excess energy is harnessed from inefficiencies in the driveline, there is the potential for substantial fuel savings.
The electric motors/generators are able to perform a braking function so that the energy produced from slowing the tractor is converted into electrical power which is then stored in the battery.
In addition the system is able to provide a power boost function by channelling drive from both electric motors and the diesel engine through the transmission as required.
There may also be the opportunity to harness the electrical power to drive implements.
The project has been under development since 1999 and several units have been working out in the field but as yet Case says it has no plans to introduce the concept.
fwmachinery@rbi.co.uk
