Using electric motors instead of Diesel on your cat

[44'cruisingcat]

Originally Posted by valhalla360

Reality is a 10yr old diesel that has had reasonable maintenance (nothing exotic or paticularly difficult) and hasn't been abused (or run an exhorbidant number of hours) will be good for another 20yrs of reliable use. You are solving a non-existent problem.

Not just solving a non-existent problem, but adding many potential additional problems.

And of course it's then not "Electric motors instead of diesel" but electric motors AS WELL AS diesel.

[pdf27]

Originally Posted by valhalla360

Pure Electric: Consider the Tesla, the ultimate electric vehicle (by some accounts). Ignoring the energy conversion efficencies and simply look at range an equivilent diesel powered car would have maybe a 5 gal gas tank. Tesla uses a huge very expensive battery bank and it takes hours to refill the tank. Drop back to something more modest like a nissan leaf and the tank (ie: batteries) hold an equivilent of maybe 2 gallons.

That's a little misleading - the Tesla battery holds either 60 or 85 kWh. A gallon of diesel contains 37.7 kWh at the lower heating value, so the Tesla battery contains the equivalent of about two gallons of diesel. The Nissan Leaf is 24 kWh so about 2/3rds of a gallon.
The increased range that the Model S gets - equivalent to about 7 gallons of diesel for my similarly-heavy Passat when driven with a light foot on highways, and rather more in city driving where electric cars excel - is purely because the energy is used much more efficiently by an electric car than by one with an internal combustion engine.

The problem with boats, however, is that the sort of idling/stop-start driving that the internal combustion engine is very poor at makes up a far smaller proportion of the engine running hours, and a much larger fraction is at an efficient cruising speed. That gives an electric motor equivalent two problems - the diesel engine is at it's best operating point rather than worst as is common for cars, and because of the sustained nature of the demand (hours or days on end, potentially) the energy requirement for a cruising sailing boat is enormous. That means in the vast majority of cases you can't just charge up from shore power or rely on solar panels - you need to generate it from fossil fuel, almost certainly diesel.

Now I think that there are some technologies on the way that will make a difference to whether this works or not, but my feeling is that they will at least initially be of limited application.

1. PowerCell are starting trials this year of a diesel fuelled fuel cell generator, and promising a truck APU version next year. This produces 24V power at around 30% efficiency, and has an expected service life of 10,000 and no maintenance. That's close to the best efficiency you'll get from a marine diesel in cruising condition (40% is about the best for one where everything is set up perfectly) and coupled with the fact that an electric motor makes using reduction gears easier and so gives you a slightly better propulsive efficiency, then it starts to look marginally viable. It's still a bit heavy, but that will improve with time - and a silent generator is pretty attractive in it's own right.
2. Batteries are coming down in weight and price. From lead-acid to LiFePO4, and in future to something like LiS. With very large battery packs you can size the fuel cell for sustained low speed cruise rather than emergency dash speed, which is a major saving. Also, very large batteries are quite attractive for a condomaran (air conditioning and a plasma TV without having to turn a noisy generator on? Thankyou very much!) - and like it or not that's a large fraction of the market. It'll always be more expensive than a diesel engine, but if the technology finds mass adoption in the automotive world then we should see major price reductions.
   LiS is around 2 kg/kWh - pretty heavy when compared to diesel, but featherweight for a battery (1/15th of the weight of lead-acid). A quarter of a ton of batteries gets you 120 kWh. A Yanmar 3YM20 produces 9kW at 3000 RPM - enough for 13 hours from those batteries. Only good if you've got a way to recharge them again, but it's getting towards a level where you can actually consider batteries as a source of propulsion power.

[nimblemotors]

Using electric motors instead of diesel works great.
A boat is about done crossing the world using all electric propulsion.
Another one crossed the atlantic this way,
and another boat is almost done doing the entire ICW all electric.
Many others also.
Numerous boats in the SFBay have no diesels, but electric.
Southern Cal has a large fleet of all-electric boats on the coast.

So if you want to do it, it can be done, and works great.
It has limitations and tradeoffs like everything else in life.
Scuba tanks only hold so much air, yet people actually breath underwater with them without a hose!! Sails only work if there is wind, and they can't be used to go in some directions, yet people have boats that use sails!!
It is strange I know, but some people like being able to move about the water without a hose attached, and others dont mind zig-zagging and going really slow if its is quiet.

[valhalla360]

Originally Posted by pdf27

That's a little misleading - the Tesla battery holds either 60 or 85 kWh. A gallon of diesel contains 37.7 kWh at the lower heating value, so the Tesla battery contains the equivalent of about two gallons of diesel. The Nissan Leaf is 24 kWh so about 2/3rds of a gallon.
The increased range that the Model S gets - equivalent to about 7 gallons of diesel for my similarly-heavy Passat when driven with a light foot on highways, and rather more in city driving where electric cars excel - is purely because the energy is used much more efficiently by an electric car than by one with an internal combustion engine.

The problem with boats, however, is that the sort of idling/stop-start driving that the internal combustion engine is very poor at makes up a far smaller proportion of the engine running hours, and a much larger fraction is at an efficient cruising speed. That gives an electric motor equivalent two problems - the diesel engine is at it's best operating point rather than worst as is common for cars, and because of the sustained nature of the demand (hours or days on end, potentially) the energy requirement for a cruising sailing boat is enormous. That means in the vast majority of cases you can't just charge up from shore power or rely on solar panels - you need to generate it from fossil fuel, almost certainly diesel.


Now I think that there are some technologies on the way that will make a difference to whether this works or not, but my feeling is that they will at least initially be of limited application.

1. PowerCell are starting trials this year of a diesel fuelled fuel cell generator, and promising a truck APU version next year. This produces 24V power at around 30% efficiency, and has an expected service life of 10,000 and no maintenance. That's close to the best efficiency you'll get from a marine diesel in cruising condition (40% is about the best for one where everything is set up perfectly) and coupled with the fact that an electric motor makes using reduction gears easier and so gives you a slightly better propulsive efficiency, then it starts to look marginally viable. It's still a bit heavy, but that will improve with time - and a silent generator is pretty attractive in it's own right.
2. Batteries are coming down in weight and price. From lead-acid to LiFePO4, and in future to something like LiS. With very large battery packs you can size the fuel cell for sustained low speed cruise rather than emergency dash speed, which is a major saving. Also, very large batteries are quite attractive for a condomaran (air conditioning and a plasma TV without having to turn a noisy generator on? Thankyou very much!) - and like it or not that's a large fraction of the market. It'll always be more expensive than a diesel engine, but if the technology finds mass adoption in the automotive world then we should see major price reductions.
   LiS is around 2 kg/kWh - pretty heavy when compared to diesel, but featherweight for a battery (1/15th of the weight of lead-acid). A quarter of a ton of batteries gets you 120 kWh. A Yanmar 3YM20 produces 9kW at 3000 RPM - enough for 13 hours from those batteries. Only good if you've got a way to recharge them again, but it's getting towards a level where you can actually consider batteries as a source of propulsion power.

Actually, talking about kwh and conversion efficencies, etc... just confuse the average user. That's why I specifically said I was ignoring that. They care about how far can they go when they get the boat up to cruising speed and in that respect the gal equivilency is what they care about. Secondarily, they care about the cost to get that power. Both of those easily favor diesel power and no cost cutting in sight is likely to change that.

I know several people with VW's diesels who claim to get 50mpg on the highway (most similar to a cruising boat use). Tesla claims something on the order of 250 miles range, so that works out to around 5 gal of diesel in real life use. Even if they have upped the range a bit or you want to argue the VW gets a little less than 50mpg so it's equivilent to a 7 gal tank, thats still a very expensive 7 gal equivilent tank in the tesla (aka: battery bank). Last I heard the battery bank costs upwards of $20k. I'm guessing most cruisers don't use $20k worth of diesel in 10yrs of cruising.

I'll become a believer in fuel cell systems when I see them going out in large numbers at reasonable prices. I've heard about fuel cells for 20yrs and I've yet to see one except for experimental of publicity purposes.

Batteries of sufficent size are still drastically more expensive (even if the prices cut in half, they would be expensive) and you still need a charging source. I suspect outside of electric drive proponents, of whom most would be appalled at using air/con, modern generators simply aren't that noisy to be a problem. We have a portable Yamaha we mount on the back deck and when the air/con isn't running, I can hear it but only if I pay attention. When the air/con comes on, the generator makes a bit more noise to pick up the load but the air/con makes enough noiuse that short of sticking my head out the door, I can't hear the generator. The idea of replacing my 70lb generator and 20-30lb of fuel with 500lb of batteries, isn't a game changer in my book.

Again, unless you have some alterior motive and are willing to ignore the major downsides, elecric propulsion is not ready for prime time.

[valhalla360]

Originally Posted by nimblemotors

Using electric motors instead of diesel works great.
A boat is about done crossing the world using all electric propulsion.
Another one crossed the atlantic this way,
and another boat is almost done doing the entire ICW all electric.
Many others also.
Numerous boats in the SFBay have no diesels, but electric.
Southern Cal has a large fleet of all-electric boats on the coast.

So if you want to do it, it can be done, and works great.
It has limitations and tradeoffs like everything else in life.
Scuba tanks only hold so much air, yet people actually breath underwater with them without a hose!! Sails only work if there is wind, and they can't be used to go in some directions, yet people have boats that use sails!!
It is strange I know, but some people like being able to move about the water without a hose attached, and others dont mind zig-zagging and going really slow if its is quiet.

You are answering a different question.

Is it possible to make an electric boat? Sure but the question was is it a better option compared to a traditional diesel. In that respect, cost, cruising speed, top speed, refueling speed, range, reliability and ease of finding repairs, just about any measure diesel wins and most of these are won by large margins.

The only advantages to electric are they are quiet and they gain you eco street-cred (actual environmental benefits are a lot more murky and not clear cut either way).

[pdf27]

Originally Posted by valhalla360

I'll become a believer in fuel cell systems when I see them going out in large numbers at reasonable prices. I've heard about fuel cells for 20yrs and I've yet to see one except for experimental of publicity purposes.

There finally seems to be a decent application for them with truck APUs - idling is being rapidly banned in the US, diesel is the only available fuel and they need some sort of APU to provide air conditioning, cooling for the load, etc. Piston engine ones are out there, but there are all sorts of air quality/maintenance/fuel burn issues with them, so a LOT of money is being spent on fuel cell APUs from a variety of sources. That isn't really true for other fuel cell applications such as cars, where you both need a very big (and powerful) fuel cell and it needs to load-follow drastically varying loads. It won't happen right away, but I'd say in 10 years time diesel fuel cell generators of a few kW based around truck APU cores will be commonplace.

Originally Posted by valhalla360

Batteries of sufficent size are still drastically more expensive (even if the prices cut in half, they would be expensive) and you still need a charging source.

Laptop battery prices per kWh have been falling at 15% a year, every year for the past 15 years - and there is little reason to think this will stop (particularly if we end up going to LiS - sulphur only costs $100/tonne and makes up most of the electrolyte weight in the battery). Tesla seem to be around $200/kWh at the moment and predicting $100/kWh soon (mega economies of scale - lots of laptop batteries out there but they don't actually contain very much per battery). Not something you'd pay for just for propulsion use, but $10 per amp-hour isn't particularly expensive for a house battery (cheaper than LiFePO4).

Originally Posted by valhalla360

Again, unless you have some alterior motive and are willing to ignore the major downsides, elecric propulsion is not ready for prime time.

I'd agree. I can think of certain circumstances where the overall experience would be better (say in remote areas where diesel is hard to obtain, and you don't motor much - the ability to recharge your "fuel tank" from other sources gets quite attractive), but it's a long way from being an economic option when diesel is so cheap.
Thinking about it, the other advantage is that the "engines" are instant-on rather than taking a few seconds to become available, and are more controllable at low power. That rather suggests it's also suitable for inshore work, where you can plug in to shore power every day (Torqueedo's target market for the Deep Blue line) - and shore power is very, very cheap compared to diesel.

[SURV69]

My thought is .... how do you want to treat your boat ... as a "sail", boat or as a "power" boat?

Electric might also make one rethink the term of efficient speed, since hull-speed is a big drag on the batteries ... gee, any sort of a bow wave means that your boat is beginning to attempting to overcome/displace the water.

If one is willing to accept 2 or so knots when the wind is otherwise calm, the draw on the batteries should give a substantially more range than pushing the water.

Electric, plain and simple just requires a different mind set.

When "engines" were introduced to sailboats, what, over a hundred years ago, the sailors of the day had to actually change their mindset virtually opposite to our re-evaluation of going from gas to electric.

WE need to change if we're going to change our method of propulsion.

[Emmalina]

There is a lake in Austria where diesel engines are not allowed. I have seen some of the boats from there. They all have electric drives and a veeery large battery bank. The lunacy of it is they all had diesel gensets to recharge the battery bank.

[downunder]

Originally Posted by Emmalina

There is a lake in Austria where diesel engines are not allowed. I have seen some of the boats from there. They all have electric drives and a veeery large battery bank. The lunacy of it is they all had diesel gensets to recharge the battery bank.

Environmentalism is not always rational.

[Lars_L]

Steve & Linda Dashew states in one of their books, that’s on a boat for circumnavigation it’s recommended that you can go for motor 700 M.

I have on my boat 280 W of solar panels. That means that I can get out approximately 30 W around the clock. I guess that a 30 W electrical motor can give my boat a speed of 1 knots or 24 M for a day. That’s certainly MUCH more than not move at all, but it will take its time to move 700 M.

[rwidman]

Originally Posted by downunder

Environmentalism is not always rational.

Exactly. Some people have drunk the electric propulsion kool aide and it' hard to get them to see reality.

Now if you're just looking for a boat to tool around the harbor and come back every few hours to recharge, electric is acceptable. Cruising long distances? Don't be silly.

[duker52004]

It looks like no one who replied to your post even bothered to check out the link you provided to Oceanvolt. I appreciate you search because I am the same way. Although we won't be full-time cruising for about 8 to 10 years, my goal is to become as self-sufficient as possible...which is why I was excited to come across Oceanvolt's ad about a year ago in Multihulls Magazine. I wrote them, and have had an ongoing dialogue going with the N.A. CEO.

Electrical generation from solar and wind have been improving significantly over the last several years, and will continue to do so. I believe quite strongly that the system Oceanvolt has developed, generating recharged power thru solar, wind, as well as hydromatically thru the design of their sail drives, may be a solid direction to look. They claim their small diesel genset is a "backup" system

The company claims that their system will meet ALL your electrical needs, including refrigeration and A/C. Granted, this "Company Literature," but those are bold claims that time will either prove or they will fail as a company.

According to their website, some chartering companies have ordered new boats, completely outfitted with their system. That may be interesting to follow.

Needless to say, if Oceanvolt can give strong historical data to their claims, I think they have a winner for those of us searching for complete autonomy while cruising!

[GoingWalkabout]

Originally Posted by Lake-Effect

Nigel Calder has been doing some testing of electric and hybrid propulsion. There was a great 2-part writeup last year in Practical Boat Owner (UK) that was both rigorous and comprehensible.

If I understand correctly, Calder focussed in on the efficiency of both systems at varying speeds and for different usage patterns. My takeaway was that for short jaunts in and out of harbour, docking, and other intermittent use, electric propulsion was most efficient and more responsive, whereas for long runs at near full speed, straight diesels were most efficient and practical. Assuming that most cruisers are in the latter camp and will need the ability to motor long distances, diesel is still the best overall choice for them.

I believe hybrids (diesel on propshaft, with electric co-drive) will become more practical as automotive electrical tech and hardware, and cheaper batteries, find their way into the marine market.

Some more discussion: The Science of Hybrid Propulsion: The Great Debate | | PassageMaker

Forgive me but are we talking about sail boat operators or power boat operators? If you mostly use a motor of any kind on a sail boat for extended times other then when becalmed I would question why are you in a sailboat to begin with.

Also reading a number of posts here I see people getting caught up with the cost equation of investing in electric power vs's diesel. I think one thing is forgotten is the benefit analysis of not having to pull into a port regularly for a gas refill. The ability to sail and not have to bring a wad of cash for fossil fuel payments. There are advantages that go beyond just the pure dollars and cents comparison of the cost of setting up for electric power that would fall under what I would call lifestyle investment. And after all don't we already sink a huge amount of money into about to achieve that life style equation return?

So I personally think one should look first and foremost at the lifestyle advantages of going solar and wind powered electric over diesel. Personally I would seriously look at electric motors with a back up diesel generator for all of my toys and high AC consumption. The only big concern I have is the spontaneous combustability of efficient ion batteries. I'm leaning on waiting till better batteries or an extensive instantaneous fire suppression system over the battery packs.

Just some thoughts fir what it's worth. Sorry if my rambling is out of place for a new member here.

[BigBeakie]

Interesting thread.

Interesting for the reason that that many have offered opinions that basically are along the same old lines that basically EP is not viable for cruising boats, but only for pottering around the marina, or whatever. Or it's too "inefficient", too unreliable etc etc etc.

And it is true that this is leading edge technology when considering some of the concerns ie the reliability, adequate power, the range, the maintainability if something doesn't work, yada yada yada.

But NONE of these concerns are show stoppers, except one, and that is there is no question that a really high quality (ie right power and robust & reliable) EP solution is more expensive right now compared to an equivalent power diesel solution. Somewhere between 50% and 100% more initial cost than diesel system depending on the vendor and how sophisticated the technology used.

And of course, as always, it will take some success stories of appropriate EP cruising boats to change set in concrete opinions, which is understandable.

From what I can see in existing technology and equipment available right now, the best application of EP is a good sailing performance cruising cat. Why? Because at some point you will need to, or rather choose to, motor for extended periods when becalmed. So with a system that has 2 motors and a dedicated propulsion battery for each motor, you can motor off battery with one while you are charging the other battery with the generator, and keep switching back and forth.

You also need a healthy solar array for house loads and propulsion battery charging in most times when you don't need to motor for long periods ie less than 4 o 6 hours depending on battery capacity.

Lithium batteries are a given. EP regeneration is nice to have for keeping up with passagemaking higher electrical loads without running the gennie at night.

Since for most motoring events the solar (and/or regen) will fill up your battery tank instead of prehistoric liquified swamp plants, it's only a matter of time until the Total Cost of Ownership curves of EP vs diesel crossover and EP will be less costly than diesel, considering all cost factors. The slope of the graphs and hence the crossover TCO point depends mainly however on how much motoring you do per year, which depends on your cruising area wrt wind availability etc. We estimate our TCO crossover will be 4 to 5 years for the South Pacific cruising we are planning. In 5 to 10 years, we can see that diesel availability may well be an issue in Pacific Island nations, so that has to be factored in as well. But not relevant in other regions.

But to suggest it isn't viable is not, IMO, an accurate assesment of where things are at right now. Systems are in implementation now that will change opinions once the good news starts filtering through, we just need a bit of patience, as I've said before.

Ok, let the arrows fly now. Let's discuss it Tell us why, based on current state of the art EP, a cruising boat cannot be EP, and indeed, why it cannot be an all electric boat. I'm here to learn

[leftbrainstuff]

Energy density is still the limiting factor for EP over diesel.

The greater simplicity of EP over diesel is a big plus.

Each year we see incremental EP improvements.

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