Oceanvolt Hybrid Motor

[fabgo]

Originally Posted by BigBeakie

Hi Fabian, glad somebody is interested

That is a yes to all your questions except no, for our full cruising displacement of 13.5 Ton, we expect a balanced continuous cruising speed of 6.6 knots. The "7 at 7" is realistic for a somewhat lighter and slimmer hull and no, that is 7kW total consumption, not 2x7kW=14kW.

For house bank we are adding a few more Super B LFP's beyond the 16kW propulsion bank, and at this point we are thinking to keep it simple as one big bank vs the complexity of separating them.

BUT, bear in mind that this is A) a very good sailing cat, so we do not anticipate using the genset much unless becalmed in under 3 or 4 knots wind, B) we have a very healthy 3 kW solar installation, and C) the regeneration of the OceanVolt SD15's is impressive as we sail...so "empty bank anxiety" is not as acute as on some other installations. The system also has very good battery monitoring & alarms, and the display is viewable from both the cockpit and saloon.

Hi BigBeakie

Thanks for the update. Curious to see photos of your 3kW solar installation. I know some cruisers managed to fit 2kW on large Lagoons, but have yet to see 3kW.

Regarding the house bank. One challenge I found when I was researching this is the propulsion bank is typically 48V or more, whereas the house bank typically runs on 12V. And I wasn't able to find any DC-to-DC converter of any significant capacity (I think 360W was the max I could find). When I spoke to OceanVolt they recommended a separate house bank connected to separate charging sources or an *inverter*, which I found to be a big drawback.

Regards,
- Fabian

[DaveWalters]

I've read about electric drives and was not impressed.
As well I can do basic arithmetic:
-most efficient motors brusless DC or induction on the market are around 90% (or a bit more) efficiency
-similar percentage for gensets
-about 2-3 % loss in the controller.

We multiply those up and we get around 80% efficiency from diesel to prop.

Marine transmissions are 97% efficient.

[StuM]

Originally Posted by DaveWalters

I've read about electric drives and was not impressed.
As well I can do basic arithmetic:
-most efficient motors brusless DC or induction on the market are around 90% (or a bit more) efficiency
-similar percentage for gensets
-about 2-3 % loss in the controller.

We multiply those up and we get around 80% efficiency from diesel to prop.

Marine transmissions are 97% efficient.

"90%.... efficiency - similar percentage for gensets"

Where do you get a figure like that from? I'd love to get one of those generators

While a generator may be 90% efficient at converting diesel to energy, a lot of that energy is heat and there's a thing called the "Carnot cycle" to consider. You certainly can't convert 90% of the energy in diesel to useful work.

"... 80% efficiency from diesel to prop"

See above.

"Marine transmissions are 97% efficient"

And the efficiency of a marine diesel engine from diesel to prop? It sure ain't anywhere close to the 97% efficiency of the transmission alone (M. Carnot again).

[myocean]

Originally Posted by valhalla360

Electric or Electric Hybrid is completely viable if you limited to weekend sailing. When you want more than a couple hours motoring, it quickly becomes impractical.

This is the cruisers forum and from my point of view cruisers do not motor a lot.
People go in and out of the anchorage and may motor one more hours here and there.
With a good hybrid system on a cat, you can get power from hydrogeneration and use this later on for motoring. Depending on the boat and the system you can get power for 4 hours of motoring with 4 knots out of 6-8 hours of sailing with 8 knots. (and you have solar power on top of that). This is very nice for regular use!
At the same time the long range motoring is not what cruisers do every day. But still the long range motoring efficiency of a good hybrid system is very good! It will not cause much more diesel consumption in comparison. May be 5%, depending of what configurations you compare and at what speed.

[John Holbrook]

I think you will find cruisers do long range motoring. The wind doesn't blow 24/7 especially in the tropics.

If the system you describe was feasible every one would have one.

Originally Posted by myocean

This is the cruisers forum and from my point of view cruisers do not motor a lot.

People go in and out of the anchorage and may motor one more hours here and there.

With a good hybrid system on a cat, you can get power from hydrogeneration and use this later on for motoring. Depending on the boat and the system you can get power for 4 hours of motoring with 4 knots out of 6-8 hours of sailing with 8 knots. (and you have solar power on top of that). This is very nice for regular use!

At the same time the long range motoring is not what cruisers do every day. But still the long range motoring efficiency of a good hybrid system is very good! It will not cause much more diesel consumption in comparison. May be 5%, depending of what configurations you compare and at what speed.

[44'cruisingcat]

Originally Posted by myocean

But still the long range motoring efficiency of a good hybrid system is very good! It will not cause much more diesel consumption in comparison. May be 5%, depending of what configurations you compare and at what speed.

So you spend a huge sum of money and end up with a less fuel efficient system?

[nuccifilms]

i got some advice that could help you (or hurt you, if you don't know what you're doing) 48vdc to 12vdc hasn't the common market demand for you to find much bigger wattages. however, these 360 watt dc to dc step down transformers you might find on those electronic importers sites are very cheap. you could do a couple things:

1) put a transformer for each load. you probably don't have anything drawing more than 360 watts. and you could use smaller transformers for some of your smaller 12v loads, like LED lighting.

2) you could buy several transformers, with the same exact same rating, and wire them in parallel. you can only get away with this with identical transformers (having identical impedance) as a safe guard you would wire in a separate fuse on the positive wire of each of your transformers, and also wire in a rectifying bridge for good measure.

3) you could have 2 separate battery banks (because more battery storage is not a bad thing) however, instead of 2 generators, you could wire in an A/B switch on your one generator. have that switch conveniently mounted on your console next to your battery level indicators. then you'd simply jump back and forth according to the levels of your 2 battery banks. keep in mind, you'd still end up using a step down transformer on the charging current going to your 12v batter bank, because your 12v batteries and anything on that circuit wouldn't like getting 48V. AND your generator is most likely pushing more than 360 watts, so you'd be employing the method of #2 suggestion in this system as well

4) 2 completely independent 12vdc and 48vdc systems, as was suggested to you

i'm the mad scientist that would go with #2 for it being the most robust. i'd also rule out suggestion #3 and #4 for those just having too many extra wires and stuff on your boat, and more stuff means more to go wrong. but i do think i covered all possibilities. maybe a 5th is to have an electronics engineer make you a custom several kw step down transformer, but custom will seriously cost.

Originally Posted by fabgo

Hi BigBeakie

Thanks for the update. Curious to see photos of your 3kW solar installation. I know some cruisers managed to fit 2kW on large Lagoons, but have yet to see 3kW.

Regarding the house bank. One challenge I found when I was researching this is the propulsion bank is typically 48V or more, whereas the house bank typically runs on 12V. And I wasn't able to find any DC-to-DC converter of any significant capacity (I think 360W was the max I could find). When I spoke to OceanVolt they recommended a separate house bank connected to separate charging sources or an *inverter*, which I found to be a big drawback.

Regards,
- Fabian

[DaveWalters]

Originally Posted by StuM

"90%.... efficiency - similar percentage for gensets"

Where do you get a figure like that from? I'd love to get one of those generators

While a generator may be 90% efficient at converting diesel to energy, a lot of that energy is heat and there's a thing called the "Carnot cycle" to consider. You certainly can't convert 90% of the energy in diesel to useful work.

"... 80% efficiency from diesel to prop"

See above.

"Marine transmissions are 97% efficient"

And the efficiency of a marine diesel engine from diesel to prop? It sure ain't anywhere close to the 97% efficiency of the transmission alone (M. Carnot again).

As an example,one of my gen sets is an 8 hp Kubota and rated at 5 KWH, which rates out to about 6.8 hp. Which is about 85% but I was being generous.

"And the efficiency of a marine diesel engine from diesel to prop? It sure ain't anywhere close to the 97% efficiency of the transmission alone"

So an electric drive is more efficient- after the motor-than a diesel at driving the prop?

[myocean]

Originally Posted by John Holbrook

If the system you describe was feasible every one would have one.

You might be true in 10 years. Today this is somehow the same like with the very first Teslas - not everyone has one because there are certain financial limitations and people are very critical. And at the same time a simple diesel is still lighter.

[myocean]

Originally Posted by DaveWalters

As an example,one of my gen sets is an 8 hp Kubota and rated at 5 KWH, which rates out to about 6.8 hp. Which is about 85% but I was being generous.

A Genset should ideally work in the most efficient working point, not just at full power of the diesel engine. That is probably the reason for your numbers.
A reasonable diesel in the best working point consumes about 0.3-0.32 liters per kWh at its shaft, where an electric machine is attached. From this you can start doing your math.

[StuM]

Originally Posted by DaveWalters

As an example,one of my gen sets is an 8 hp Kubota and rated at 5 KWH, which rates out to about 6.8 hp. Which is about 85% but I was being generous.

Please learn the difference between power and energy before opining on motors. That should be kW - a measure of Power. KWh is an entirely different thing - it's a measure of energy. You can't convert kWh to HP, they are totally different units.

And that 8 HP to 6.8HP only tells us at how inefficient the system is converting the output of the diesel engine to electricity, It tells us nothing about how efficient the diesel engine itself is at converting diesel to usable energy.
(Your claim was "While a generator may be 90% efficient at converting diesel to energy")

[myocean]

Originally Posted by valhalla360

I'd like to see the design that gets 7kts at 7kw in a 45-50 (the post was mixing the two up).

I'll give you 10-1 odds it's either imaginary or the major drawbacks have been glossed over.

45-50' cats typically have motors in the 40-75hp range PER HULL...and suddenly approx. 10hp total will be plenty.

Look for example at the Volvo D2-40 datasheet
( http://www.volspec.co.uk/engines/mar...0_epatier3.pdf , dashed line in first diagram on right hand side ).
You see that at 1600 rpm with the recommended prop, the calculated propellor load (shaft power) is about 3.5 kW. So if both Volvo D2-40 engines run with 1600 and the boat makes 7 knots with this, than the "7 at 7" claim is correct.

As it might be possible to operate an electric motor at even lower rpms with higher torque (with larger prop diameter), there could be some additional gain in hydrodynamic efficiency. But this is not mandatory.

[John Holbrook]

Why so harsh? I think everyone knew what the Dave meant.

Originally Posted by StuM

Please learn the difference between power and energy before opining on motors. That should be kW - a measure of Power. KWh is an entirely different thing - it's a measure of energy. You can't convert kWh to HP, they are totally different units.

And that 8 HP to 6.8HP only tells us at how inefficient the system is converting the output of the diesel engine to electricity, It tells us nothing about how efficient the diesel engine itself is at converting diesel to usable energy.
(Your claim was "While a generator may be 90% efficient at converting diesel to energy")

[John Holbrook]

Last week I was on a voyage 48 and 2000rpm on one Yanmar 45hp gave 6kn on flat water with no current or wind so your figures are close. Waves, wind or current could up the power needed.

Originally Posted by myocean

Look for example at the Volvo D2-40 datasheet
( http://www.volspec.co.uk/engines/mar...0_epatier3.pdf , dashed line in first diagram on right hand side ).
You see that at 1600 rpm with the recommended prop, the calculated propellor load (shaft power) is about 3.5 kW. So if both Volvo D2-40 engines run with 1600 and the boat makes 7 knots with this, than the "7 at 7" claim is correct.

As it might be possible to operate an electric motor at even lower rpms with higher torque (with larger prop diameter), there could be some additional gain in hydrodynamic efficiency. But this is not mandatory.

[John Holbrook]

In ten years we might be using something else like solidified hydrogen fuel cells. BMW and MB seemed to be hedging their bets between electric and hydrogen.

I hear you about Tesla and really hope that company succeeds because they are bringing / forcing so much change in the auto industry but at his point they are still making losses each year. Plus a big part of Tesla's strategy is installing charging stations which are not feasible on the open ocean.

I don't think people are critical of new technology and do think many read this thread in the hope that this technology is or will be feasible for them.

Big companies like Nordhavn and Lagoon have done their maths tried hybrid and failed. At this stage hybrid remains unproven for normal boating requirements but we can always hope that changes.

Originally Posted by myocean

You might be true in 10 years. Today this is somehow the same like with the very first Teslas - not everyone has one because there are certain financial limitations and people are very critical. And at the same time a simple diesel is still lighter.