When will diesel engines be replaced by electric ones?

[jdc]

Fuel cells

Fuel cells are not an answer at all I think. Whatever system you use, you have to carry the energy you need, stored somehow. That can be by electro-chemical means, ie a battery, or via latent heat of combustion - this last category includes fuel cells since their energy is derived from oxidation - or by nuclear reactions, or possibly by some other potential energy ('lastic band, flywheel, spring and clockwork??).

It's pretty much off the cards for any practical collection of batteries to store the equivalent of 300 litres of diesel in a yacht, so unless we reduce range dramatically we come back to taking chemicals with us, which we convert somehow to electricity by oxidation, and thence to rotation and thence to propulsion. If we really want to include all issues we should also include energy cost of making and transporting and storing the fuel, and we should also include CO2 emmissions as well. It's not as if methanol doesn't contain carbon, or is free to make.

By this metric fuel cells come out really badly because they typically burn hydrocarbons, but don't use any of the carbon, despite this having higher calorific value, and just throw it away by burning (making CO2 in the process) without extracting energy from it at all. They are perhaps more efficient than internal combustion engines at converting Hydrogen atoms to electrical energy, but this does not compensate for their wasting the carbon; net result is that fuel cells are I believe less efficient in energy terms, and require much greater volume of fuel than one would need for the equivalent motive energy from diesel. As you'd expect there's a wikipedia page on this.

Use them for quietness or low maintenance or reliability maybe, but not for for green reasons: until and unless we generate hydogen from renewables and can transport and store that, fuel cells are much worse for our planet than is the diesel engine.

 

[AntarcticPilot]

Hybrids are likely to become more common with spin offs from the automotive world.

However, pure electric power will never come, until somebody discovers a storage medium for the energy that is as efficient as liquid diesel. The motors themselves are very efficient, but batteries and recharging are not.

So, you see electrics successfully used in applications where long term storage of energy is not a problem, for example boats used at low speeds for short periods on inland waterways (electric power was in use before the introduction of diesel). However, when you need more power and there is no easy source of energy produced by a portablke source, the practical restrictions in terms of capacity and duration rule it out.

What is happening now in both the automotive and marine field is a debate on how to improve the efficiency of the use of the energy by different combinations of diesel and electric. So hybrids can either propel by using both the diesel motor and an electric motor in different mixes to power the prop or use the diesel to charge batteries and all propulsion is by electric motor. The latter method has many advantages and is already in use in commercial ships as well as some of the electric cars - the new Fisker for example.

From a yachtsmen's point of view all the new methods have big disadvantages - both space and cost. These do however diminish as power requirements and size of vessel rise, so you you will see them first in larger craft. In smaller sizes, the advantages of diesel in terms of cost, space utilisation, range, durability and energy efficiency are such that it will continue to dominate.

A comment about the automotive world - the only cars that are efficient enough to be Band A excise duty are NOT hybrid - they are pure diesel of petrol. The VW Bluemotion range are pure diesel and are rated at about 88 mpg; the Citroen C1, Toyota Aygo and I forget the other are all basically the same small petrol engine.

Hybrid cars suffer badly from the weight penalty of lugging batteries around.

I strongly suspect that unless the batteries are charged by a "clean" source - e.g. Photovoltaics - a hybrid system for either automotive OR marine use is intrinsically less efficient because of conversion losses and weight penalties.

 

[Frankie-H]

The batteries used are the Mastervolt Lithium Ion batteries with a total weight of 270 kilo for 25.8 kW of usable power 5 hours at a speed of 6 knots. (This is not taking into account any recharging taking place from the wind generator or solar panels).

(item #34 on the Technology page of the website)

Like the statistics but HOW MUCH? and how often would you change them in the life of an engine?

Just seen the reply earlier. What would the life be? Seems you could only replace 2 or 3 times per engine.

 

[maby]

Of course, we'll have to get the EU to agree what colour the electricity should be first...

 

[Seajet]

Of course, we'll have to get the EU to agree what colour the electricity should be first...

Maby,

excellent, are you a Douglas Adams fan by any chance ?!

Maxi77,

Sterling engines are spiffing for submarines, as they basically consist of stored oxygen running a conventional engine while submerged; I can't quite see how that is useful for yachts, unless significantly unlucky enough to be underwater ?!

Fuel cells will come along one day, there'll possibly be a few dalliences with hybrid jobs first, but maybe not in my lifetime, we've had our 'Concorde Moments' of rapid development with things like that aircraft, Saturn V, A12 / SR71,the Harrier & Space Shuttle along with the Buggati Veyron; technology seems to be more maturely plodding these days, so we might have to wait a bit longer than Gene Roddenberry prophecied to get interstellar starships - or fuel cell driven boats...

 

[maxi77]

Maby,

excellent, are you a Douglas Adams fan by any chance ?!

Maxi77,

Sterling engines are spiffing for submarines, as they basically consist of stored oxygen running a conventional engine while submerged; I can't quite see how that is useful for yachts, unless significantly unlucky enough to be underwater ?!

Fuel cells will come along one day, there'll possibly be a few dalliences with hybrid jobs first, but maybe not in my lifetime, we've had our 'Concorde Moments' of rapid development with things like that aircraft, Saturn V, A12 / SR71,the Harrier & Space Shuttle along with the Buggati Veyron; technology seems to be more maturely plodding these days, so we might have to wait a bit longer than Gene Roddenberry prophecied to get interstellar starships - or fuel cell driven boats...

On a yacht the oxygen would be all around though I am aware of research which result in engines using the difference between sea and air temperaures. The fuel cell is already here and there are companies offering them as generators for yachts today. Yes the systems are not there today but in time I expect they will and be affordable. I agree the hybrid is not the way ahead, not enough engine power to get you out of trouble, and more battery ballast than you really need.

As for fuel cell boats look up the latest U boats, they use fuel cells

http://en.wikipedia.org/wiki/Type_212_submarine

 

[crewman]

Fuel cells

Current fuel cells run on hydrogen which is very tricky to store, you either need very high pressures (10,000 psi+) or extreme cryogenic with associated boil off or you store methanol and reform that to carbon dioxide and hydrogen just before use. Methanol is not only highly flammable (not as readily flammable as petrol but much more so than diesel) but is also very toxic. It is fully miscible in water so needs to be kept in well sealed containers. Diesel or diesel/electric hybrid seems a much better idea.

Batteries are using very exotic materials nowadays (molten sodium/sulphur anyone) and still do not store a lot of power.

 

[pagoda]

On a yacht the oxygen would be all around though I am aware of research which result in engines using the difference between sea and air temperaures. The fuel cell is already here and there are companies offering them as generators for yachts today. Yes the systems are not there today but in time I expect they will and be affordable. I agree the hybrid is not the way ahead, not enough engine power to get you out of trouble, and more battery ballast than you really need.

As for fuel cell boats look up the latest U boats, they use fuel cells

http://en.wikipedia.org/wiki/Type_212_submarine

As somebody pointed out early in this thread - a lot of the apparent reliance on diesel is down to energy density and efficiency of conversion.

Until less lossy storage / conversion emerges - at a price we can cope with -we may well have to adjust our sailing behaviour to be closer to that of our grandfathers - who warped in and out of harbour or used buoys to achieve the same result. Less motoring to fit the week-end sailor?
I can see electric or diesel elactric for marina / harbour use in the future, but perhaps in a few years, not 4 or 5 hours hard motoring to get back on a Sunday PM?
I'd quite like to try warping out - or sailing all the way out , but the harbour master would have a fit
Graeme

 

[Kelpie]

Certain niche users could find electric or hybrid propulsion useful.
For example, day-sailors who only go out in good sailing weather, using the motor for a few minutes at the start and end of the day, charging the battery by solar, wind, or shore power inbetween sails.
Or at the other extreme, blue-water cruisers to whom motoring vast distances is not part of the plan; the motor would be used for close quarters manoevuring or setting anchors etc.

However most of us lie somewhere inbetween these two extremes.

 

[stuhaynes]

No mention of batteries!

I'm the kind of sailor who prefers to turn the engine off as much as possible, but how many of us would want to forego the ability to motor for say 6 hours as a minimum?

Even if you said two hours was an acceptable endurance, that's a fairly big battery?

They mention a battery weight of 270kg's which is supposed to be able to produce 6 knots for 5 hours (if I read it right).

 

[Tranona]

Certain niche users could find electric or hybrid propulsion useful.
For example, day-sailors who only go out in good sailing weather, using the motor for a few minutes at the start and end of the day, charging the battery by solar, wind, or shore power inbetween sails.
Or at the other extreme, blue-water cruisers to whom motoring vast distances is not part of the plan; the motor would be used for close quarters manoevuring or setting anchors etc.

However most of us lie somewhere inbetween these two extremes.

Both of these scenarios already exist. The Torquedo outboard is becoming popular for day sailers - at a price. The bluewater cruiser scenario has been explored by Nicki Perryman who writes regularly in various mags and installed electric propulsion in her Robb Lion. Now replaced by another Yanmar. Exercise failed for all the reasons discussed here. Poor range, poor speed, inability to recharge.

 

[Tranona]

A comment about the automotive world - the only cars that are efficient enough to be Band A excise duty are NOT hybrid - they are pure diesel of petrol. The VW Bluemotion range are pure diesel and are rated at about 88 mpg; the Citroen C1, Toyota Aygo and I forget the other are all basically the same small petrol engine.

Hybrid cars suffer badly from the weight penalty of lugging batteries around.

I strongly suspect that unless the batteries are charged by a "clean" source - e.g. Photovoltaics - a hybrid system for either automotive OR marine use is intrinsically less efficient because of conversion losses and weight penalties.

Quite. That is why they only find buyers if heavily subsidised. My son in law has just replaced his company S Max with a Prius, solely because of the tax advantages. On every count it is inferior to its predecesor which my daughter has kept for a runabout because it is cheaper to run than her 8 year old petrol Fusion (excluding the purchase price and depreciation if bought new).

 

[jdc]

It's even more stark for boats!

Quite ... On every count it is inferior to its predecesor ...

I agree, but with cars the advantage of hybrid is during town driving: when accelerating stored electical energy is converted to kinetic, and then when one has to brake it's converted back again (<< 100% efficiently) by regenerative braking. This is not applicable to boats, so hybrid will always be worse for total efficiency and your point is even more valid.

One thing we could look at is efficiency of the drive: propellors are not good - probably only 15% efficient(1) or so at converting torque x rotation to force x distance travelled. Compared to fish or dolphins this is dreadful, so maybe one day we'll see motorboats waggling tails and fins...

(1) the reason is that they work by ejecting a stream of water behind them. This contains lots of energy which is wasted. To improve efficiency one has to have larger area propellors which send out a jet which is travelling slower (I coud inflict a graph on you;-)

 

[Tranona]

I agree, but with cars the advantage of hybrid is during town driving: when accelerating stored electical energy is converted to kinetic, and then when one has to brake it's converted back again (<< 100% efficiently) by regenerative braking. This is not applicable to boats, so hybrid will always be worse for total efficiency and your point is even more valid.

One thing we could look at is efficiency of the drive: propellors are not good - probably only 15% efficient(1) or so at converting torque x rotation to force x distance travelled. Compared to fish or dolphins this is dreadful, so maybe one day we'll see motorboats waggling tails and fins...

(1) the reason is that they work by ejecting a stream of water behind them. This contains lots of energy which is wasted. To improve efficiency one has to have larger area propellors which send out a jet which is travelling slower (I coud inflict a graph on you;-)

According to Nikki the biggest failing of their installation was the poor performance of regeneration from the spinning prop. As this was the tipping point in favour - when you spend days under sail it would be nice to think the spinning prop would recharge the batteries for the short bursts of power required for docking etc. In practice it did not.

 

[mjcoon]

... OR marine use is intrinsically less efficient because of conversion losses and weight penalties.

Although, amusingly, yachts carry around a huge weight "penalty" in the form of a keel. So if only batteries could be made dense enough to act as a keel (lead-acid development, perhaps) but also surpass modern technologies, at least the weight could be made useful!

Mike.

 

[Greenheart]

Deja vu...

All very interesting, gentlemen.

I don't understand fuel cells, so I've kept quiet, this far. But...

...on the general subject of auxilliary electric power as a possibility today, may I refer interested readers to over 150 contributions made on one thread, on this subject last year? Here it is. Quite fiery in places:

http://www.ybw.com/forums/showthread.php?t=268793

Perhaps I was initially too damning about diesel, when I started that thread. Diesels' defenders came out of the woodwork like...like black smoke from a diesel exhaust.

Amusing, because the index page for threads on the forum is dominated by queries relating to diesel tankage, starting troubles, weird noises, smoke, recurring infuriating obstinacy on the donkey's part...yet evidently no-one wanted to risk trying an alternative.

What really seemed to grind the contributors' gears, was the fact, recognised in this year's thread, that if one has the time to be rather a sailing purist, keeping auxilliary use to an absolute minimum and relying instead on fail-safe passage planning...

...then the wind and the actual sailing element that we all enjoy, becomes master over every trip, even ruling out destinations that might have been possible, if uncomfortable, under power or motor-sailing.

So weekend sailors whose schedules govern their 'sailing' trips, can't afford to run an auxilliary which also enjoys time off.

Personally, that rarified 'modern-convenience' only increases my readiness to use electricity instead (when I have a boat to experiment on!). Jettisoning the many diesel issues that spatter every forum index page ...(have a look, it's funny)... will be another benefit.

Now give me half a mo to put my cycle helmet on...good. Abusive replies: commence!

 

[Evadne]

All very interesting, gentlemen.

....

Perhaps I was initially too damning about diesel, when I started that thread. Diesels' defenders came out of the woodwork like...like black smoke from a diesel exhaust.

Amusing, because the index page for threads on the forum is dominated by queries relating to diesel tankage, starting troubles, weird noises, smoke, recurring infuriating obstinacy on the donkey's part...yet evidently no-one wanted to risk trying an alternative.

......

Now give me half a mo to put my cycle helmet on...good. Abusive replies: commence!

The reason diesel engines feature heavily in the PBO forum's requests for help, for example is because any electrical or mechanical item on a sailing yacht has a hard life and breaks down. Couple that with a reliance on it, and no backup and what you get is grief. I reckon that if you think a diesel engine is unreliable, just imagine a 20 year-old yacht with electric propulsion, lithium batteries and fuel cell charging!!

There is a law in electronics that states that the reliability of a system is inversely proportional to the number of components used. Diesel motors have few moving parts and minimal electronics. Splitting the power from the propulsion (i.e. hybrids) will inevitably reduce reliability. Replacing fuel with an electronically controlled battery and charger will reduce reliability.

At least the motor is simpler, as long as it's waterproof. Any item that can't take the occasional bucket of water over it will not last on a boat, or at best should be treated with care, I would suggest. At least, that's how it is on my boat: the two items that fall into that category are the batteries and SWMBO

 

[Grumpybear]

I believe that proponents of hybrid cars conflate local with general green advantages. they actually can reduce pollution levels in cities because the battery can drive the vehicle for some distance without needing the engine to run at all. This is a genuine if often overstated benefit.

however, for any significant distance, and when the battery requires recharging, the engine is inevitably less efficient, and more polluting, overall due to the weight penalty and the inefficiencies in the power conversion train.

it can be argued that these considerations also apply to hybrid powered boats. Shore power recharging simply transfers the power generation and its costs, both financial and environmental, somewhere else.

 

[maby]

I believe that proponents of hybrid cars conflate local with general green advantages. they actually can reduce pollution levels in cities because the battery can drive the vehicle for some distance without needing the engine to run at all. This is a genuine if often overstated benefit.

however, for any significant distance, and when the battery requires recharging, the engine is inevitably less efficient, and more polluting, overall due to the weight penalty and the inefficiencies in the power conversion train.

it can be argued that these considerations also apply to hybrid powered boats. Shore power recharging simply transfers the power generation and its costs, both financial and environmental, somewhere else.

There are various types of hybrid car and the above is only true of some of them.

We have a second generation Prius and its battery pack is very small. Its range on electric motor is less than a mile. The efficiency comes from the design of petrol engine that is fitted - which is an Atkinson cycle engine with an asymmetric compression-expansion ratio. This is very fuel efficient, but has a very narrow power curve. The electric motor serves as a sort of turbo charger allowing the car to accelerate to top speed without needing a fifteen speed gearbox. In normal cruising, it is running petrol-electric with the petrol engine held at its optimum speed and car speed controlled through the electric motor.

The battery pack in the first generation Prius was actually several tens of NiCad 'C' cells. For the second generation, they did have some special purpose cells manufactured, but you could still easily pick the pack up with one hand.

 

[Nostrodamus]

So what we are saying is that at the moment batteries will not be in boats in general for some time.
Also the so called green cars are less green than a lot of new fuel efficient diesel cars considering you have to make the batteries and dispose of them.