Iskra’ integrated hybrid system
Originally created on April 27 2008
[~Apr~~30~]
The Iskra Hybrid system is not unique inasmuch as its principle has been adopted by part of the automotive industry and first tier OEM’s such as Continental to introduce hybrid vehicles, and Iskra’ development has been adapted to the marine environment by OEM manufacturers such as Steyr while others are expected to introduce similar offerings shortly. Taking from their documentation the following presentation it offers some fascinating advantages that we will illustrate through their different operating modes.
If we could bolt this unit behind the diesel power plant of SS3 we would all of a sudden have four potentially high value added functions in one unit:
1. Starter motor
2. Generator
3. Electric Propulsion motor, and finally
4. Booster motor
1. The starter motor
Perhaps the less dramatic feature of the system it is here again a key function for automotive stop/start fuel economy functions. It does allow for the elimination of the ICE starter (and we will see next alternator), allowing for these functions to be integrated in the canbus.
2. Generator mode
Here again we find a function that is not exclusive to Iskra nor to the marine propulsion world as we have seen Yanmar introduce two years ago a flywheel generator adaptable to two of its ICEs, providing either 3 or 6KW outputs. Iskra has taken the concept further by increasing the output plus the ability to design the system to specific voltages. As the unit is positioned between the engine block and gearbox one needs only to decouple the prop shaft (neutral) to generate the power required to recharge batteries and or provide house / service loads.
Here come the interesting part not offered by products such as Yanmar. By disconnecting the coupling “A” on the layout, under sail the generator can replenish the battery banks through regenerative sailing. Of course this will revive the age-old debate of “spin or block the prop”, but for those who are not running to their next appointment a small loss of speed under sail can save a lot of fuel and provide considerably more autonomy to the blue water sailor.
3. Electric propulsion mode
Now we are at the central function – electric propulsion. The integrated flywheel disconnects from the ICE through coupling “A” and is the main propulsion unit of the vessel. The power output is largely a function of chosen voltage and can easily be ramped up to at least the 10kW level.
Iskra has developed higher voltage systems and is working on Li-ion management interface. Just imagine being able to troll for three or four hours without smell of diesel fumes let alone the sound pollution!
Finally, for those still wanting to keep their diesel power plant as a backup, the last function for the Iskra system can be a big added bonus.
4. Booster mode
We expect to incur the wrath of some of the diesel OEM community here but have you ever wondered why a typical saiboat has such a big diesel engine? Wondered why your say 75hp diesel with a power / consumption / torque curve optimal at say 3400rpms only provides cavitation at that speed? Most often sailboat propellers will begin to cavitate in the 2800rpm range well below optimal ICE output.
The answer lies in the lack of power at the lower rpms, akin to trying to begin driving you manual shift car starting with fifth gear — your engine will choke because it has insufficient torque to propulse (whereas a modern electric motor has the same torque at almost all rpm speeds). With Iskra’s booster mode one could considerably downsize the diesel engine plant, fuel bill and pollution! The electric engine managed by the controller assists the diesel through the lower rpm range.
Conclusion
The Iskra system is truly innnovative for the marine community and could enable many sailors and motor recreational boaters to find a comfortable compromise in their quest for a greener if not more economical approach to their passion. The weakest link of the system lies in the integration of the system with the ICE – as it is designed to replace the flywheel the housing of the system is OEM proprietary, and if a generic housing were to be developed the OEM would likely invalidate its warranty on the engine. On the other hand, beyond the inherent benefits of electric propulsion, when one looks at the cost of a generator, the advantage of downsizing the diesel plant by perhaps 50%, the considerable energy savings and more…, well like in the automotive industry change will take time.
We have an open dialog with Iskra and are following future developments that might enable a systems integration approach that would overcome some of these problems, we will post as news becomes available.
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