Hybrid diesel electric propulsion

[Ian_Edwards]

The problem with manufactures fuel consumption curves, is that they are all taken at maximum load, irrespective of the rpm.

However, the torque absorbed by a propeller is proportional to the rotational speed of the prop squared, so that the engine isn't normally running at full load. Ideally it only runs at full load at max hull speed (assuming a non planing hull) when the maximum torque the engine can develop matches the torque the prop can absorb. In practice the designer will match the max torque the engine can produce a little above the max prop torque at hull speed. This gives a little in hand for driving into a head sea and/or wind when the advance coefficient is lower.

The net result is that the engine's governor is throttled back to maintain the set rpm and the engine uses less fuel. It will only use the manufacturer's quoted fuel consumption at max speed.

For my boat with a water line length of 46ft, and a 48hp engine, I run at about 2L/hr at 6 knots and about 10L/hr a 9 knots, the max theoretical hull is about 9.5 knots.

As for diesel Electric Hybrid systems, they definitely work on larger vessels, most new ferries are diesel electric and offshore support vessels have been diesel electric for many years. I can see diesel electric in yachts being attractive to owners who normally day sails from marinas, which would allow them to charge up from the mains overnight and have a diesel for longer trips. However, retrofitting a big battery pack to an existing hull is probably a nonstarter. You'd have to figure out how to make best use of the mass of the batteries as ballast.

 

[earlybird]

I agree with you about published fuel consumption curves. Many boat-owners mistakenly translate these data directly into fuel usage for their particular installation.
However, I'm not so sure about most ferries being hybrid. Maybe a few. AFAIK, Calmac, for example, have a couple of very small vessels on short runs where the time on the berth is disproportionate to the passage time. This might make sense.
The advantage of diesel-electric, eg the Calmac Bute ferries, is that the need for awkward mechanical transmission to the propellors is eliminated.
These and others are not hybrid. No battery storage is involved.

 

[doug748]

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

Nigel Calder fitted a system to his new Malo 46 a number of years ago, as mentioned, he does not seem overly thrilled with the kit. Bit of an overview here:

https://www.yachtingmagazine.com/sea-greener#page-11

The Rogers yard also dabbled a bit:

http://www.jeremyrogers.co.uk/contessa-32-new-build/calypso-project-partners.php
PS, I just read that the batteries weighed a ton - literally. So that put the displacement up by 25%.

 

[Yacht Yogi]

A point not really addressed in the previous posts is the practice of running the main propulsion engine just to recharge the batteries on long passages under sail. It would seem attractive to have electric propulsion and a larger battery bank, charged from shore power for day-sailing activities plus a small diesel generator to recharge both "house" and propulsion batteries when needed on a longer voyage. The generator can be smaller and lighter than a boat diesel engine and could be installed anywhere convenient. The heavier battery bank can be positioned low down, in the middle of the boat. This would free up cabin space for a better interior layout.

 

[Tranona]

A point not really addressed in the previous posts is the practice of running the main propulsion engine just to recharge the batteries on long passages under sail. It would seem attractive to have electric propulsion and a larger battery bank, charged from shore power for day-sailing activities plus a small diesel generator to recharge both "house" and propulsion batteries when needed on a longer voyage. The generator can be smaller and lighter than a boat diesel engine and could be installed anywhere convenient. The heavier battery bank can be positioned low down, in the middle of the boat. This would free up cabin space for a better interior layout.

Would suggest very few people now use the main engine just for charging batteries and not propulsion now that solar and wind are viable alternatives for long distance voyagers. If a boat is large enough to have high electricity needs (such as air conditioning) then a dedicated generator and a conventional diesel drive is far more effective.

 

[luckybeanz]

I am surprised no one has suggested ditching the Internal Combustion Engine all together and replacing it with pure electric. There are plenty of people doing this now and one can even buy kit motors. With the price of batteries coming down fast it seems to be a very viable option. Plus with regen from the prop and solar and wind, one should be able to generate enough power to recharge.

Some reading http://www.bwsailing.com/bw/gear/silent-running/

 

[Tranona]

I am surprised no one has suggested ditching the Internal Combustion Engine all together and replacing it with pure electric. There are plenty of people doing this now and one can even buy kit motors. With the price of batteries coming down fast it seems to be a very viable option. Plus with regen from the prop and solar and wind, one should be able to generate enough power to recharge.

Some reading http://www.bwsailing.com/bw/gear/silent-running/

This thread ia about hybrids which are very different, but equally unattractive for different reasons.

Electric power for yacht auxiliaries is still a pipedream despite all the hype.

Just do some simple sums comparing the energy density of a tank of diesel and batteries and you will get your answer. Despite the improvements in battery capacity they are still insufficient to provide the sort of range that yachts require without an external charging source.

Where electric power is workable on boats (and has been since the 1890s - yes well over 100 years ago) is in applications where the power and range requirements are low and there is ready access to charging facilities. So you find many electric boats on the lakes and rivers, particularly in the UK and in the commercial world such specialised applications as short journey ferries that can recharge between runs.

Once you get to yachts the power and range requirements are very different and you find that you can neither store enough energy to be independent of shore powered charging nor generate any significant energy from onboard equipment such as solar panels or wind. This is because not only are they inefficient and unreliable there is physically not enough space to fit them (particularly solar.

So you find the only electric yachts that work are either those that only require enough power for short runs such as day sailors from a marina base or ocean voyagers who only use engine power at the beginning and end of a passage. However, you will find that even the latter who have tried it have ditched because of the limitations of only having a short range because of the limits in storage capacity.

Lots of dreamers in this field but no real alternatives developed so far as nobody has managed to solve the energy storage issue.

 

[Bi111ion]

I remember Bossoms Boatyard in Oxford was making electric river launches in the 1970s, as a conversion of their steam launches. The problem is energy density though, and you can store a lot more energy in Diesel fuel than batteries. So I expect electric propulsion with solar top up charging will come at some stage, but think it is too soon for retro-fitting to conventional blue water yachts. What about multihulls with a huge solar array?

 

[luckybeanz]

This thread ia about hybrids which are very different, but equally unattractive for different reasons.

Electric power for yacht auxiliaries is still a pipedream despite all the hype.

Just do some simple sums comparing the energy density of a tank of diesel and batteries and you will get your answer. Despite the improvements in battery capacity they are still insufficient to provide the sort of range that yachts require without an external charging source.

Where electric power is workable on boats (and has been since the 1890s - yes well over 100 years ago) is in applications where the power and range requirements are low and there is ready access to charging facilities. So you find many electric boats on the lakes and rivers, particularly in the UK and in the commercial world such specialised applications as short journey ferries that can recharge between runs.

Once you get to yachts the power and range requirements are very different and you find that you can neither store enough energy to be independent of shore powered charging nor generate any significant energy from onboard equipment such as solar panels or wind. This is because not only are they inefficient and unreliable there is physically not enough space to fit them (particularly solar.

So you find the only electric yachts that work are either those that only require enough power for short runs such as day sailors from a marina base or ocean voyagers who only use engine power at the beginning and end of a passage. However, you will find that even the latter who have tried it have ditched because of the limitations of only having a short range because of the limits in storage capacity.

Lots of dreamers in this field but no real alternatives developed so far as nobody has managed to solve the energy storage issue.

I am aware that hybrids are very different, though the consensus seemed to be that they are not viable. While your comments are very note worthy, my research is telling me that times are changing. Just look at the cost of solar and storage now and it continues to plummet. Solar energy is now the cheapest form of energy. Since these technologies are improving exponentially I think it is time to revisit these old, accepted ideas about energy.

You want some real world examples, just have a read here http://electricyacht.com/gulfstar-sailmaster-39/ and that was 4 years ago!

 

[Bi111ion]

From the electric yacht web site (http://electricyacht.com/all-electric-and-hybrid-electric-drive/))

" For the cruiser, we do not recommend electric only for major cruising but the electric hybrid solution provides a significant advantage over diesel only."

 

[JumbleDuck]

I am aware that hybrids are very different, though the consensus seemed to be that they are not viable. While your comments are very note worthy, my research is telling me that times are changing.

It will perhaps help you understand the responses you are going to get (and indeed have already started to get) with a short phrase book:

Nobody wants one of these = I don't have one of these

Everybody wants one of these = I have one of these

The market has moved on = I used to have one of these

Brexit will be a great success = I haven't taken my medication today​

HTH. HAND.

 

[Tranona]

I am aware that hybrids are very different, though the consensus seemed to be that they are not viable. While your comments are very note worthy, my research is telling me that times are changing. Just look at the cost of solar and storage now and it continues to plummet. Solar energy is now the cheapest form of energy. Since these technologies are improving exponentially I think it is time to revisit these old, accepted ideas about energy.

You want some real world examples, just have a read here http://electricyacht.com/gulfstar-sailmaster-39/ and that was 4 years ago!

Both of the articles you link to acknowledge the limitations of range which are OK if you are prepared to live with them. Unfortunately very few people are prepared to. Wonderful to talk about (as in the Gulfstar item) being able to run for "24 hours at 2.5-3 knots" when my last boat of similar size could run for 80 hours at 5.5 knots on one tank of fuel.

I have been listening to all the claims that "things are changing" on this front for 20 years and essentially little has changed. There are still the same odd people building their own motors and doing their own installations and getting similar outcomes. Nobody has found a solution to the problem of lack of energy density or recharging.

So while it is possible to power a yacht with just electricity it is NOT a substitute for an IC engine if you want to use the yacht in the same way as most currently do.

While there are likely to be major advances in electric power in the automotive world in the next 10 years or so, that is because of legislative pressure resulting in vast sums being poured into R&D. Little of this apart possibly for storage capacity (batteries) will have any application to yachts. There is currently no pressure being specifically directed at boats to change, nor is there the volume available to justify serious R&D. Therefore any spin off will be incidental, just as our current engines are spin offs from developments in the industrial field.

 

[Stemar]

From a position of no practical experience of such boats, I've often thought that the biggest disadvantage of the more recent Southerlies is their twin rudders and single props. That setup (and price) is what keeps them from being my perfect boat. It seems to me that one could build one with electric powered pods by each rudder, thereby gaining the manoeuvrability of a twin screw mobo. This would allow the motor to be positioned anywhere convenient, rather than being constrained by the position of the prop. Lightening the ballast shoe a bit would allow some substantial Li batteries to provide silent power for a few hours.

It may be less efficient than a direct drive diesel, but a sailing boat shouldn't need its engines for hours at a time very often, so that's not so much of a problem Plug-in charging (on my private mooring, obviously) would top up the batteries between charges. It seems likely that a boat that needs, say 30hp for propulsion could get away with, maybe 20HP with help from the batteries when more is needed, with a consequent saving in weight.

It probably won't ever happen, of course, but it's an interesting thought experiment.

 

[luckybeanz]

It will perhaps help you understand the responses you are going to get (and indeed have already started to get) with a short phrase book:

Nobody wants one of these = I don't have one of these

Everybody wants one of these = I have one of these

The market has moved on = I used to have one of these

Brexit will be a great success = I haven't taken my medication today​

HTH. HAND.

Ha Ha, great post. To add to your phrase book, and I think appropriate to the attitude of some.
Climate change is a hoax - I am in denial

 

[luckybeanz]

Both of the articles you link to acknowledge the limitations of range which are OK if you are prepared to live with them. Unfortunately very few people are prepared to. Wonderful to talk about (as in the Gulfstar item) being able to run for "24 hours at 2.5-3 knots" when my last boat of similar size could run for 80 hours at 5.5 knots on one tank of fuel.

Sure, though when that tank of fuel runs out you have to fill it up. Not to mention the cost of filling it up, which is only going to increase over time. Contrast that with the electric charged by regen, solar or wind, once you run out, you either hang around a bit or find a breeze and sail around to refill, plus these technologies are only going to decrease in cost over time.

I have been listening to all the claims that "things are changing" on this front for 20 years and essentially little has changed. There are still the same odd people building their own motors and doing their own installations and getting similar outcomes. Nobody has found a solution to the problem of lack of energy density or recharging.

Perhaps you need to change your sources, https://www.economist.com/briefing/...ke-for-batteries-to-change-the-face-of-energy. Battery energy density has more than doubled in the last decade alone.

Adjacent to this solar cell efficiency has more than doubled in the last 10 years https://en.wikipedia.org/wiki/Solar_cell_efficiency
Compare this to a diesel engine technology https://en.wikipedia.org/wiki/Diesel_engine and https://en.wikipedia.org/wiki/Engine_efficiency#Diesel_engines the first engines produced in 1897 were about 27% efficient, today from the most modern engines one can only expect a max of around 44-50% efficiency.

Now consider that an electric motor is around about 90% efficient and you can see that you cannot make a direct comparison when talking about energy density.

So while it is possible to power a yacht with just electricity it is NOT a substitute for an IC engine if you want to use the yacht in the same way as most currently do.

While there are likely to be major advances in electric power in the automotive world in the next 10 years or so, that is because of legislative pressure resulting in vast sums being poured into R&D. Little of this apart possibly for storage capacity (batteries) will have any application to yachts. There is currently no pressure being specifically directed at boats to change, nor is there the volume available to justify serious R&D. Therefore any spin off will be incidental, just as our current engines are spin offs from developments in the industrial field.

This may be true, though it is clear that the advancements have come a lot faster than most expected. It is also not fair to say that little will affect yachts. It already is https://www.inverse.com/article/44507-norway-zero-emission-fjords and https://www.fastcompany.com/40524700/these-electric-cargo-barges-are-a-cleaner-solution-than-trucks.

Besides which it is clear that doing what we have always done i.e. using a yacht the same way as most currently do, is having significant impacts on our environment and ability to sustain ourselves. So do we not all have the obligation to make these changes where we can and not just rely on government legislation?

I apologize for digressing so much from the topic of hybrids, but as you can probably tell this is something I am rather passionate about and if we can get more pioneers to change and make people see the possibilities it can only be a good thing.

 

[Tranona]

Besides which it is clear that doing what we have always done i.e. using a yacht the same way as most currently do, is having significant impacts on our environment and ability to sustain ourselves. So do we not all have the obligation to make these changes where we can and not just rely on government legislation?

I apologize for digressing so much from the topic of hybrids, but as you can probably tell this is something I am rather passionate about and if we can get more pioneers to change and make people see the possibilities it can only be a good thing.

People are only motivated by their own personal interests and there is little demand for electric power through choice as it fails to satisfy wants which are what motivates peoples' purchase decisions. So no manufacturer is going to invest in R&D to develop a product for which there is no consumer demand. On the other hand there is little about the environmental impact of leisure boating that will attract politicians interest as there are no votes in it.

That is why electric power in sailing yachts is still (as it was over 20 years ago) in the hands of hobby sailors adapting mostly 100 year old technology to produce what is for most an unworkable outcome IF the objective is to replace IC engines. Your examples illustrate this perfectly.

If we were denied IC engines yachting as we have come to know it over the last 60 years will cease to exist as it is so dependent on diesel power. Typically a cruising yacht spends as much as half of the time on passage under engine, and it is engines that have made such boats viable for everyday leisure use.

I am fully aware of the advances in battery energy density. However that has not so far resulted in products that are suitable for leisure boat use. I recognise that once batteries are developed for automotive use there may be spin offs for marine use, but we are talking years down the line simply because marine use is not the objective of the research. There are some very experienced firms active in electric power for boats and none have even attempted to build systems for yachts.

Your two articles are interesting, but are totally unrelated to yachts. They are exactly the sort of applications I referred to earlier. They are limited range, inland waterways and have access to shoreside charging. The objective is to remove the pollution from the locality of use, just like electric city cars, buses, milk floats etc, but as any serious study shows the emissions just occur elsewhere rather than actually fall. Using "clean" sources such as wind and solar does have some impact. However it is not practical to use these as the sole source of energy generation on a yacht so you are still dependent on transferring the energy from shore to the boat.

Sorry to sound so negative, but just look at electric cars in their current state of development. Twice the price of conventional cars, fraction of the range (some exceptions), require heavy public financed incentives to buyers and still have only a tiny share of the market. This despite the billions spent on developing them. The same basic reason why yacht owners would not buy - they are not perfect (in fact very imperfect for most users) substitutes for IC powered vehicles.

 

[JumbleDuck]

People are only motivated by their own personal interests and there is little demand for electric power through choice as it fails to satisfy wants which are what motivates peoples' purchase decisions. So no manufacturer is going to invest in R&D to develop a product for which there is no consumer demand.

It will perhaps help you understand the responses you are going to get (and indeed have already started to get) with a short phrase book:

Nobody wants one of these = I don't have one of these​

 

[Tranona]

That is not the same thing. It is a general (and easily tested) observation of consumer behaviour. There are people who "want it" or who claim they would buy it if it were available. They tend to disappear when offered the product and see the cost (currently twice the price of a diesel equivalent based on the Cornish Shrimper recently fitted with electric), the range limitations (under 10 hours at modest cruising speed) and requirement for access to shorepower.

I would buy a boat powered by electricity tomorrow IF it was the same price as a diesel and had the same potential range and needed one 10 minute visit to the fuel dock every 80 hours of motoring.

However as we all know the current offerings are nothing like that, nor is there any prospect of one being available in the forseeable future.

So you are right NOBODY WANTS ONE OF THESE - that is a product available to buy today.

The only people who currently buy are those that are prepared to live with the limitations, exactly the same as electric cars which represent less than 2% of sales of new cars each year, despite the hype and incentives. The loss in functionality in boats is even more severe than cars so potential for new boat sales is likely to be even smaller. This is borne out by the handful of boats reported to be powered by electricity (excluding types which have traditionally used this method because it suits the mode of operation) and why it is still the preserve of the hobbyist.

 

[Interlude]

One possible benefit with hybrid propulsion (with electric or hydraulic drive), providing the motor attached to the prop is small (light) enough) would be the ability to retract the prop and shaft when not motoring. Either a outboard pivoting in a well (or on the transom) or a vertical lift with a curved "box" under the prop that aligns with the hull when retracted. Efficiency will drop a little, but the removal of the need for a shaft through the hull or a large hole for the sail drive seal has attractions. The well would extend above the waterline in a large enough boat, lowering the probability of failure leading to sinking.

I suspect this is actually of little benefit as the number of singings due to shaft failure (dropping out) or sail drive seal failure appears to be negligible - I have heard of one of each, and the latter was due to a cat grounding.

So just an idea for cold rainy nights.

 

[DownWest]

One possible benefit with hybrid propulsion (with electric or hydraulic drive), providing the motor attached to the prop is small (light) enough) would be the ability to retract the prop and shaft when not motoring. Either a outboard pivoting in a well (or on the transom) or a vertical lift with a curved "box" under the prop that aligns with the hull when retracted. Efficiency will drop a little, but the removal of the need for a shaft through the hull or a large hole for the sail drive seal has attractions. The well would extend above the waterline in a large enough boat, lowering the probability of failure leading to sinking.

I suspect this is actually of little benefit as the number of singings due to shaft failure (dropping out) or sail drive seal failure appears to be negligible - I have heard of one of each, and the latter was due to a cat grounding.

So just an idea for cold rainy nights.

As above, this does not address the basic problem of storage and range.
Dark night, rough sea, onshore wind and a jammed halyard. Add in no charge in the batteries in the expensive electric drive and…..diesel looks very attractive.

Plus, while pollution is a factor. Current electric systems are not very clean overall due to battery technology and materials.