A young company on the cleantech scene is harnessing a neglected aspect of technology to make electric vehicles work better.
“There is a growing body of research promoting the fact that a combination of electrics and hydraulics results in a better electrical car,” says André Reyneke, managing director of Ducere Holdings, the company that owns the MISER™ Hybrid Hydraulic Transmission technology.
He says it is no secret that the batteries remain the Achilles heel of any electric car. The world is still waiting for the battery that can hold enough energy and last as long as the vehicle itself.
“And while we wait, any system that can improve – in other words, reduce – the current draw from batteries and increase the number of charge/discharge cycles will be welcomed. And we have that system.”
He explains that the MISER™ system is a scalable and efficient hydraulic hybrid technology that has great regenerative-braking efficiency and engine optimising abilities. That means the system can be configured as a series-type hybrid as well as a parallel-type hybrid.
“In practice, that means that the hydraulics can be used to boost acceleration, such as with a launch-assist function while limiting the current draw. We do this by using the hydraulic system as a motor in series with the electric motor and that increases driveline torque but reduces battery current draw.”
Reyneke says the hydraulic system is significantly more efficient than the typical regenerative ability of an electric drive.
“An electric vehicle is about 30% efficient in regenerative braking mode, where our hydraulics achieve around 70% efficiency.”
He says this brings a number of possibilities into play. The more efficient regenerative braking could mean up to a 30% increase in range in a town-drive cycle.
“But that’s not all. By reducing the maximum current draw under acceleration, the Peukert effect (as the rate of discharge increases, the battery’s capacity decreases) is reduced, especially for technologies such as lead-acid batteries. And that may now be viable at a fraction of the cost of Lithium-ion technology.”
He explains that this is because by doing much of the braking hydraulically, the battery is not subject to heavy in-rush current during the regeneration part of the drive cycle that would increase the number of charge cycles.
“Off course, this must be shown in practice. Therefore, Ducere Holdings is building two variations of this novel technology. One version is a typical electrical vehicle, but it is equipped with the MISER hybrid transmission to prove the point.
“For the second variation, Ducere have gone a step further by adding a variation with a small – about 25kW – petrol motor to the design. At first, this may seem counter-productive, but it has some very interesting capabilities.
“Firstly, the vehicle can run as a zero-emissions vehicle when operating on the batteries and hydraulics. This would be in town, or as a mom’s taxi during the week when it can be recharged at home every day. But if you engage the mode where the engine is used as a third power source, you have a vehicle that can travel long distances on the open road, too.
“But this is not just an engine running inside a vehicle, it is also subject to the abilities of the MISER™ transmission and will still have both an optimised running profile – known as ideal brake-specific fuel consumption – as well as the boost abilities of hydraulic plus electric plus petrol.”
The first prototype will be running early in 2018.
“It won’t be a 200km/h pocket rocket, but it will have great overtaking ability at normal road speeds,” he says.
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