Jimmy Cornell goes Electric, with a Cat

[donradcliffe]

It would be a lot easier to have a takeaway for th hybrid system if they gave us some real data, such as passage times and fuel consumption

[JustMurph]

BigB: I have another test for you to do, range extending motoring. What is more efficient, motoring with your diesel, or motoring with the electric and the generator providing the power. The aim would be to motor at the same speed with either option, then calculate the fuel usage. You'd repeat this for a few realistic speeds, lets say 4 knots for a slow cruise on minimal power, 6 knots for a normal cruise and what ever it will do with your generator maxed out.

Does the direct drive with many fewer energy conversions out weight the more efficient prop on the electric?

[BigBeakie]

JM, ok now that's a good test! Thanks, it's noted in the sea trial test plan.

Turn about is fair play: the next time your out could you try motoring in calm water with your rudder centered as well as you can, and go on one side, then switch over? How much rudder angle do you need to keep going straight? Or put another way, if the rudder is centered will you veer to port on only the starboard engine? Leave boards up to maximise the effect.

[BigBeakie]

Wouldn't I need a fuel flow meter on both the Beta diesel and the genset to measure fuel use? Don't have that, don't know what's involved.

Also, the electric does not run directly from the output of the genset. It runs from the batteries which are charged by the genset. But we can see exactly the watts we are consuming by the AXC 20, and also see from the Cerbo on the Canbus what the genset is putting back into the batts, so I can balance them perfectly, while motoring.

Which is the same principle as solar motoring, using the same watts the panels are outputting, not dipping into the battery reserves.

[Adelie]

Originally Posted by goboatingnow

A tool is suitable but not appropriate …..There’s a contradiction

If someone took a gun to a boxing fight, the gun would certainly be suitable to defeat an opponent but it would not be appropriate.

[Adelie]

Originally Posted by JustMurph

BigB: I have another test for you to do, range extending motoring. What is more efficient, motoring with your diesel, or motoring with the electric and the generator providing the power. The aim would be to motor at the same speed with either option, then calculate the fuel usage. You'd repeat this for a few realistic speeds, lets say 4 knots for a slow cruise on minimal power, 6 knots for a normal cruise and what ever it will do with your generator maxed out.

Does the direct drive with many fewer energy conversions out weight the more efficient prop on the electric?

Direct drive motor would be more efficient.

Series hybrid has a number of advantages, efficiency for extended motoring is not one of them.

European researched this for their fishing and coastal work fleets expecting series hybrid to be more efficient. Discovered otherwise.
HYMAR was the research name if you want to Google it.

[Adelie]

Originally Posted by BigBeakie

Wouldn't I need a fuel flow meter on both the Beta diesel and the genset to measure fuel use? Don't have that, don't know what's involved.

Also, the electric does not run directly from the output of the genset. It runs from the batteries which are charged by the genset. But we can see exactly the watts we are consuming by the AXC 20, and also see from the Cerbo on the Canbus what the genset is putting back into the batts, so I can balance them perfectly, while motoring.

Which is the same principle as solar motoring, using the same watts the panels are outputting, not dipping into the battery reserves.

Exactly, since charging cables coming to battery and EP cable coming from battery share the terminals on the battery if generator is supplying power at some time as EP is pushing then power will bypass battery and go straight from generator to EP.

[Tupaia]

Originally Posted by BigBeakie

JM, ok now that's a good test! Thanks, it's noted in the sea trial test plan.

Turn about is fair play: the next time your out could you try motoring in calm water with your rudder centered as well as you can, and go on one side, then switch over? How much rudder angle do you need to keep going straight? Or put another way, if the rudder is centered will you veer to port on only the starboard engine? Leave boards up to maximise the effect.

This is more to do with direction of prop rotation than diesel/electric.

In most cases sailing cats can run on one engine and there is a little but very little rudder required. The props tend to be small and very close to the surface resulting in minor paddle wheel effect.

Power cats will use contra rotating propellers ACW/CW to compensate and allow better close quarters maneuvering. Not in the same way you would use to allow one engine running when CW/ACW viewed from astern is more appropriate so the drag of the opposite hull is compensated for by the paddle wheel effect of the driven side.

Unless the test boat has contra rotating props, either way, the results will be flawed.

[jmh2002]

Originally Posted by BigBeakie

JMH,

Thanks for posting that, some really good perspectives from EP owners after 3 years cruising and 40,000nm

Yes, I thought it was a useful and interesting perspective.

[BigBeakie]

Originally Posted by Adelie

Direct drive motor would be more efficient.

Series hybrid has a number of advantages, efficiency for extended motoring is not one of them.

European researched this for their fishing and coastal work fleets expecting series hybrid to be more efficient. Discovered otherwise.
HYMAR was the research name if you want to Google it.

Adelie,

Good point and I did read Calders research when he published on this but I recall there is a consideration of interpreting the fuel map depending on load placed on the diesel. He takes care to emphasize the need to keep the load up on a diesel for max fuel efficiency.

So in our case, we have a larger Beta diesel ( 45HP Turbo/36kW) as propulsion vs a Yanmar 3YM30AE ( 29HP/22kW) genset producing 15kW continuous.

The question is will the fuel efficiency of the larger diesel lightly loaded be better than the smaller diesel more heavily loaded? So it's not exactly an apples to apples comparison because of the load factor and how that affects fuel efficiency.

Will be fun to find out

[BigBeakie]

Originally Posted by Tupaia

This is more to do with direction of prop rotation than diesel/electric.

In most cases sailing cats can run on one engine and there is a little but very little rudder required. The props tend to be small and very close to the surface resulting in minor paddle wheel effect.

Power cats will use contra rotating propellers ACW/CW to compensate and allow better close quarters maneuvering. Not in the same way you would use to allow one engine running when CW/ACW viewed from astern is more appropriate so the drag of the opposite hull is compensated for by the paddle wheel effect of the driven side.

Unless the test boat has contra rotating props, either way, the results will be flawed.

Also a very good point. In my case I have counter rotating like your Power cat example. It is ACW/CW viewed from stern, so comparison should be valid.

[JustMurph]

From Nigel Calders research, it seems there will be a cross over point, somewhere around 4-6 knots, where it will be more efficient to use the serial hybrid below and more efficient direct drive above.

Working out what the fuel usage will be is definitely no straight forward, especially on the electric side where you have other charge sources and consumers. The test probably needs to be averaged over a longer distance/time, so will take some commitment. To be accurate, you'd need to turn your solar off. Other consumers can stay on, as they're either being supplied by the Beta's alternator, or by the generator. Their use should be roughly a constant.

[Tupaia]

Originally Posted by BigBeakie

Also a very good point. In my case I have counter rotating like your Power cat example. It is ACW/CW viewed from stern, so comparison should be valid.

Yes your comparison should be valid but the arrangement you have is not the best for running on one engine. The paddle wheel effect will enhance the turning effect caused by the drag of the un driven hull.


You sound like you are considering everything very carefully most sailing cats do not have contra rotating props not because the typical sail drives used are not reversible but because the majority of off the shelf props are only made to rotate in one direction.


Any pictures of your project?

[Tupaia]

Originally Posted by JustMurph

Working out what the fuel usage will be is definitely no straight forward, especially on the electric side where you have other charge sources and consumers.

Generator fuel consumption will also vary with the state of charge of the batteries. If it can keep up with the demand then the fuel consumption will remain fairly constant or reduce as the batteries reach full. If it can't keep up then then it will increase as the batteries discharge until it reaches maximum output then it should remain constant as the batteries continue to discharge.


Hope you are good at spreadsheets.

[BigBeakie]

Originally Posted by JustMurph

From Nigel Calders research, it seems there will be a cross over point, somewhere around 4-6 knots, where it will be more efficient to use the serial hybrid below and more efficient direct drive above.

Working out what the fuel usage will be is definitely no straight forward, especially on the electric side where you have other charge sources and consumers. The test probably needs to be averaged over a longer distance/time, so will take some commitment. To be accurate, you'd need to turn your solar off. Other consumers can stay on, as they're either being supplied by the Beta's alternator, or by the generator. Their use should be roughly a constant.

Yes, that is what I'm expecting re a crossover point. I will have to test at, say 3, set motoring speeds under very similar sea conditions/tides/winds...may not be easy. It would be foolish to bet against Nigel Calder's experience. He appears to be methodical, plans his testing well, and records good data. I hope to emulate that in a small way.

Yes solar would be off, also our AC loads are powered by the propulsion bank via the Multiplus inverter, so those loads will have to be off. Our DC loads are off the house bank so at least I can leave them alone during the testing.

As I said, the trick will be to isolate the test, to balance the genset output to the propulsion bank vs the draw from the propulsion bank from the motor and keep that going long enough to use say 10 liters of diesel.