Hybrid Drive – The Ultimate Cruising Solution

When I wrote the article Hybrid Power: Myth or Magic in the first edition of Ocean Sailor back in January 2020, hybrid drives were just beginning to be discussed within the cruising fraternity. Back then at Kraken, we had one or two clients that were vaguely interested in it. Fast forward two years or so and now the next five Kraken’s to be launched will all have hybrid drive systems.

To achieve the type of hybrid drive solution that we believe is required by the modern liveaboard cruising community required collaboration with industry leaders. We teamed up with Yanmar Engines, Combi Hybrid, MG Lithium Batteries and Bruntons Propellers to develop, what we feel, is the perfect hybrid drive system for extended liveaboard cruising.

Liveaboard voyaging cruisers have different demands of an electric drive system from those required by marina based sailboat owners. Heading back to plug the boat in just isn’t an option when on passage. Because of that single fact, eliminating all fossil fuel-powered motors is sadly not an option right now. Solar power cannot provide enough power to drive a yacht with all the mod-cons required by most cruisers for several days at a time. Solar power also cannot provide enough power to fully drive the boat for several days when she is becalmed. We should not be too depressed about that fact since we must remember that we sail-boaters had hybrid-drive way before the term was ever mentioned.

Accepting that we must retain some reliance on fossil fuels, the rest of the marine industry offers one of two hybrid solutions:

Electric drive main engine supplemented by a large generator.
or

Direct drive from the main engine supplemented by an electric drive motor

We believe that option one simply doesn’t stack up. Powering the yacht by charging batteries and then drawing power from those batteries to power an electric drive motor is inherently inefficient, especially when you consider:

A very large fast running generator will consume more fuel than a slow running direct drive main engine, when driving the boat at similar speeds

Complete dependency on a fast running (3,200rpm) generator for both drive and power generation is risky.

Therefore, the standard hybrid drive system that is fitted in a Kraken Yacht is based on a direct drive main engine supplemented by an electric drive motor
(see below).

The following examples are based on a Kraken 50 equipped with a Yanmar 80 hp main engine and a 20kW Combi electric drive motor with a 48v & 24V lithium battery bank.

These are the benefits of the Kraken Standard Hybrid Drive:

Low fuel consumption under power when no wind is available. 2.5 lts an hour cruising at 5.5 knots. (real data as recorded at sea) 

Hydro-regeneration of electrical power into the battery bank from the propeller when under sail. Typically Kraken 50 owners can expect 600 watts of charge to the batteries when sailing at 6kts.
 

Very fast generation of power from the combi electric drive motor powered by the main engine when at anchor with the prop shaft disengaged by the clutch. 18 kilowatts of usable power, so battery recharging time is radically reduced.

Up to 60mins of electric drive power at 5 kts without using the main engine from the battery bank when at full charge. 120 mins at 3 kts.

Full use of redundant main engine power to recharge the batteries. The electric drive motor goes into regeneration mode using unused main engine power once the torque required on the prop shaft has reduced with the engine in cruise mode.

Silent running in ‘power assist’ when sailing in light winds.

Increased ability to store power compared to AGM or wet cell batteries.

Introducing the

Kraken optimum hybrid drive

We have now developed an enhanced hybrid drive solution that provides levels of redundancy previously only dreamed about by voyaging sailors; The Kraken Optimum Hybrid Drive. This system is based on a direct drive main engine, but retains a small, low rpm generator as well. 

The Kraken Optimum Hybrid Drive system has all the benefits of our standard hybrid drive system as listed above, but has, in addition, a unique major benefit;
Main engine failure redundancy.

Although the Yanmar engines I have used in my yachts over the last twenty years have been extremely reliable, on two occasions the engine failed to start. On one occasion the starter motor jammed, on the other occassion the engine failed to start due to a bad earth connection. On both occasions, the fault was not realized until I arrived at a destination anchorage after long passages at sea. The last time was at Vanuatu and the anchorage was up a narrow winding dog’s leg channel inside a fringing coral reef. I tried for hours to find the engine fault, but eventually gave up and had to sail upwind via the narrow channel to the anchorage. Luckily the very light breeze held until we finally rounded up and, with huge relief, dropped the anchor.

Had the wind failed, even though I had crew posted at the anchor ready to drop it at my word, I would have had a very good chance of drifting helplessly onto the shallow reef on either side. Had that happened with the Kraken Optimum Hybrid Drive system, firing up the generator and engaging the electric drive motor would have powered us through the channel with ease.

Whilst the demand from eco-aware cruisers to reduce their carbon footprint, or wake, is the main motivation for choosing a hybrid system, but I believe the benefit of powered drive redundency is a compelling reason alone to chose this system.

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