Hybrid diesel electric propulsion

[Bi111ion]

Anyone fitted a hybrid diesel electric propulsion system to an ocean going yacht? Pros and cons. Here is an example of the website of a supplier.

http://www.hybrid-marine.co.uk/5.html

 

[Tranona]

Anyone fitted a hybrid diesel electric propulsion system to an ocean going yacht? Pros and cons. Here is an example of the website of a supplier.

http://www.hybrid-marine.co.uk/5.html

Such products have been on the market for several years and have failed to make any impression. Main reasons are the do not suit the usage pattern of typical yachts, are bulky, expensive and inefficient.

Direct propulsion from a diesel engine is efficient, simple and reliable plus the diesel can supply sufficient electricity or most yacht's needs, although when there is little need for propulsion an alternative source of electrical power, such a solar is useful.

Suggest you read Nigel Calder's report on his EU funded project on hybrid power for yachts, published in PBO in 2015. This provides detailed explanations for the unsuitability of hybrid power units.

 

[davidej]

I cant see that there will be significant benefits for the average cruising yacht.

Perhaps someone would like to explain them.

 

[RupertW]

On a boat where the main usage will typically be at constant revs at some efficient throttle point then I can't see the electric part adds anything unlike with a car in town where all the variation in revs needed makes a hybrid more efficient.

 

[jdc]

On a boat where the main usage will typically be at constant revs at some efficient throttle point then I can't see the electric part adds anything unlike with a car in town where all the variation in revs needed makes a hybrid more efficient.

While I agree with your overall conclusion (that hybrid in a yacht has much less benefit than in a car), I think that it's not because of the variable revs. Actually diesels have surprisingly little variation in litres per kWHr of energy produced between 1000rpm and 3500rpm. Cars are better in town driving because one recovers the kinetic energy from braking - which of course doesn't happen with a boat.

 

[William_H]

No the advantage of diesel electric as used in trucks and trains is the ability to provide drive at zero speed up to cruise speed. The driven road wheels being locked to vehicle speed. So you don't need a clutch and gear box or automatic equivalent.
In your boat the prop is not locked to boat speed being only partially connected so prop slip provides the difference between stopped boat and running engine when you whack it into gear.
Of course the tendency to run your boat and engine at constant speed somewhat replicates the efficiency advantages of hybrid cars. I don't think regenerative braking provides a huge efficiency improvement. (depending on driving conditions) olewill

 

[earlybird]

Domestic leccy cost the consumer about £0.15 per kWh. but there is some conversion inefficiency. Diesel energy, at UK fuel pump rices is very roughly the same, but by the time it's been converted to mechanical energy by a boat engine, it's 2 or 3 times that cost. More if road fuel duty is in the equation
Cost comparisons for the two types of propulsion aren't like for like.

 

[jdc]

No the advantage of diesel electric as used in trucks and trains is the ability to provide drive at zero speed up to cruise speed. The driven road wheels being locked to vehicle speed. So you don't need a clutch and gear box or automatic equivalent.
In your boat the prop is not locked to boat speed being only partially connected so prop slip provides the difference between stopped boat and running engine when you whack it into gear.
Of course the tendency to run your boat and engine at constant speed somewhat replicates the efficiency advantages of hybrid cars. I don't think regenerative braking provides a huge efficiency improvement. (depending on driving conditions) olewill

Well the post I was disagreeing with was specifically about town driving in a car, where I do think that the regenerative braking is quite significant. But whichever, we probably all agree that it's the stop-start nature of town driving which gives the advantage to hybrid, it's just that I don't think it's because changing the revs of the engine. Had it been phrased 'changing the speed of the vehicle' then I would have agreed.
But, hay, I guess I was nit-picking anyway!

 

[RupertW]

Well the post I was disagreeing with was specifically about town driving in a car, where I do think that the regenerative braking is quite significant. But whichever, we probably all agree that it's the stop-start nature of town driving which gives the advantage to hybrid, it's just that I don't think it's because changing the revs of the engine. Had it been phrased 'changing the speed of the vehicle' then I would have agreed.
But, hay, I guess I was nit-picking anyway!

Not really - you were making a valid point based on your understanding that there is a fairly flat fuel use across a range of revs. There I would disagree, though, both in theory because throttle changes act by allowing more fuel to floe and in practice on any engine/hull/propellor combination I have had. For example with my current boat 2000 revs uses about 2.5 lires per hour, 2200 is about 3 litres and 2500 is about 3.5 litres per hour. Not insignificant changes as it's not the fuel usage in neutral that matters but the usage under load.

 

[boatmike]

Without disagreeing with any other posts diesel electric and diesel hydraulic drives have been tried in catamarans and larger twin screw yachts but have never gained popularity in smaller vessels. As far as I can see it the main advantage claimed is the ability to drive two screws with one diesel. This is of course an advantage sometimes in weight and space saving but offset by loss of efficiency. The weight saving is not as high as one might think because electric motors and hydraulic drives are not light and adding two of each offsets the weight saving of only having one engine. There is also the consideration of complexity. More to go wrong and you don't get the added safeguard of having 2 engines. With only one screw its a no brainer. no real advantage, more weight, more to go wrong, less efficient and more noise (which is considerable with hydraulic drives) Before anyone slates me for mentioning hydraulic drives, I know this question was not asked but I have included them as the considerations are similar. Also I recognise that on larger yachts and ships it's a different ball game and both DE and DH drives have a legitimate and justified application.

 

[Flica]

Anyone fitted a hybrid diesel electric propulsion system to an ocean going yacht? Pros and cons. Here is an example of the website of a supplier.

http://www.hybrid-marine.co.uk/5.html

The original "Lagoon" range of multihulls were launched with this hybrid auxiliary.
As far as I know all have been modified back to more conventional twin diesels.
This I discovered from the 2nd owner of one. The enormous generator had been retained because its cover was an integral part of the centre-cockpit.
Apparently none were sold outside continental Europe.

 

[davidej]

Not really - you were making a valid point based on your understanding that there is a fairly flat fuel use across a range of revs. There I would disagree, though, both in theory because throttle changes act by allowing more fuel to floe and in practice on any engine/hull/propellor combination I have had. For example with my current boat 2000 revs uses about 2.5 lires per hour, 2200 is about 3 litres and 2500 is about 3.5 litres per hour. Not insignificant changes as it's not the fuel usage in neutral that matters but the usage under load.

But what about the fuel consumption per hp.hr. That is pretty flat across the operating range.

Obbviously opening the throttle to go faster and create more drag/wash uses more fuel.

 

[earlybird]

But at the higher revs the boat travels faster and therefore further in a given time. Fuel usage /distance travelled is the useful criterion.

 

[RupertW]

But at the higher revs the boat travels faster and therefore further in a given time. Fuel usage /distance travelled is the useful criterion.

Not for this discussion - the question was about the advantage of a boat travelling at constant revs for much of its time compared to a hybrid. The varying fuel use at different revs if the boat was used in and out of a harbour, stopping and starting a lot would make a hybrid more efficient, but that doesn't apply to most yachts.

Your general point is right of course and I have found that with my current engine/prop/boat combination in flat water 1300 revs gets me furthest per litre but tediously slowly and not surprisingly 2800 revs gets me there a lot faster but with least miles per litre.

 

[Minchsailor]

Hers's the fuel consumption of my Beta 35, expressed as l/nm for various revs. Most economical cruising speed is at 1650 revs, at 4.8kns. In practice I motor at about 1900 revs at about 5.5kns.

 

[prv]

Anyone fitted a hybrid diesel electric propulsion system to an ocean going yacht? Pros and cons. Here is an example of the website of a supplier.

http://www.hybrid-marine.co.uk/5.html

Although they do offer seagoing systems, it's interesting to me that the "Why fit a hybrid?" page only tries to address the ditchcrawling case

Pete

 

[RupertW]

Hers's the fuel consumption of my Beta 35, expressed as l/nm for various revs. Most economical cruising speed is at 1650 revs, at 4.8kns. In practice I motor at about 1900 revs at about 5.5kns.

View attachment 67549

That's nice - I have only recorded at 5 points

 

[BurnitBlue]

There is a yacht called UMA on youtube doing a circumnavigation with the electric motor from a fork lift truck. It is apparently successful. The story is a spread out among their episodes. They are really not work shy having rescued ´their yacht a Person 36 from scrap. Actually I have found their episodes among the best narratives on youtube.

 

[PeterV]

Hybrid electric drive works very well on Naval vessels where you have a big, thirsty gas turbine for full speed and a set of diesel generators for supplying hotel loads and driving an electric motor for slow speed operation. If you don't have two very different modes of operation and different duty generators then I cannot see why you would want the complexity over a simple, efficient direct drive diesel.

 

[Minchsailor]

That's nice - I have only recorded at 5 points

I measured at 8 points, then used the spreadsheet's (LibreCalc) curve fitting algorithim.