The Offshore Voyaging Reference Site

Electric or Diesel-Electric Drives for Voyaging Boats

Solar Panels charging batteries aboard sail boat

Until a few years ago, I thought that diesel-electric would become a viable alternative for voyaging sailboats that would solve the age-old problem of matching the output of an engine to the power requirements of a propeller across a wide range of RPM settings.

But it turns out that this is a more complex subject than it appears at first look.

Let’s examine the viability of electric and diesel-electric drives for voyaging sailboats.


Login to continue reading (scroll down)

More Articles From Electric and Hybrid Diesel-Electric For Cruising Boats:

  1. When Electric Drive Works For a Cruising Sailboat
  2. Electric or Diesel-Electric Drives for Voyaging Boats
  3. Real Numbers For Electric And Diesel-Electric Drives
104 Comments
Oldest
Newest
Inline Feedbacks
View all comments
Rob Withers

Just Like your 5 points of ‘What Really Matters’, the beauty of diesel engines (at least the older ones) is they only need the following to keep going:
– fuel
– air
– some oil
– not much else
On my car, almost invariably the bits that go wrong are bits that weren’t invented 20 years ago. The engine on my boat is 20 years old, so that eliminates a whole heap of trouble!

The gains for a hybrid approach would have to huge to justify the increased complexity.

C. Dan

It is no-doubt due to my own ignorance, but your comments on the “simplicity” of a diesel system made me chuckle.

Check out Tim Lackey’s build-log of his 30′ motor-sailor refit, and you will see why I had that reaction – the photos of the electrical system and engine-room (including a “simple” diesel) make me shrink with terror (as I would have no idea how to fix any part of the system that failed):
http://www.fisher30.lackeysailing.com/logs/2013/february13/20313.html

Ben Campbell

Do you have thoughts about a pure diesel/electric design—that is, like a series hybrid without huge battery bank? Seems like there could be some pure layout advantages, due to the inconvenient locations conventional sailboats need to put the engine. I’d love to keep the diesel engine out of the living space. It’s noisy and smelly. It’s often a cramped space for something that needs regular access for maintenance.

Gene Gruender

Hydraulic is what your talking about. Diesel motor mounted anywhere, a pump on the motor, a hydraulic motor on the propshaft. Less efficient than direct drive, more effecient and less dangerous than diesel generator and electric motor.

I can tell you from experience, a busted line or seal is a mess, as well as leaving you dead in the water.

C. Dan

Thanks John as always for a thoughtful (and comprehensive!) post on a subject I care about
One comment: Anyone who has a bow-thruster or an electric windlass is already using a series-hybrid electric system – these applications satisfy Eric’s “peaking” requirement (and for those who view an engine primarily as a tool for maneuvering around anchorages, hybrid-electric propulsion could also make sense, as you point out)
And a (loaded) question: Would you agree that technological breakthroughs are more likely to make hybrid-electric (or full-electric) more viable in the future, vs. ICE solutions? There are countless research teams working on solutions to develop better and cheaper batteries, and the same goes for solar panels (which have already seen significant price improvements in the last 2 years).
Note: I am not suggesting hybrid-electric or electric-only for the A-40 (although if an engine-less option were offered, I might take it)

C. Dan

I have read Calder’s work as well, and I don’t think we’ll be able to get away from having something flammable on board (be it solid, liquid, or gas).

I think any of these systems can be designed safely, and any of them can fail spectacularly if they are not maintained properly. I feel like you choose to emphasize the risks of some technologies while minimizing the risks in others, perhaps because you are more familiar with one particular type of system.

Simon Wirth

Hei John
In some cases it is a good thing that hydrogen is lighter than air.
But then, the hydrogen atoms are that smal that there is no way to completly contain it as a gas for long. If there is hydrogen as a gas in the tank, and there always will be, there is hydrogen leaking around. Garanteeing a good enough vertilation may not allways be easy or sage in itself.

John Rushworth

John,

It is interesting that you post this today of all days. Today my boat (SY ELEKTRA) passed her MCA survey, becoming the UK’s very first commercially coded pure electric propulsion sailing yacht, under MGN 280.

As I have said before I think your choice of propulsion for the Adventure 40 is the right one and like you I advocate keeping things simple. More on that in a moment.

Your post whilst biased if you like, in favour (and naturally so) of your criteria for the Adventure 40 is fine for that puprose, but will not suit all types of sailor. Your most telling comment is “it depends what you want”.

It is on that basis that I started my project a year ago. Tommorrow is launch day and time will tell how my ‘electric’ choices stack up against the 10hp 2 cylinder Volvo Penta with 2.4:1 reduction box, compared to my non geared direct electric drive replacement.

In my case capital cost was an issue and my conversion has come out cheaper than a re-engine and likely cheaper than a complete diesel engine re-build, both of those options based on an expected life of around 15 years before accumulative major costs kick in.

So why did I chooose electric? Going on your post it would appear madness to go that route. And the truth is you simply cannot in terms of volume, weight and calorific value beat a good old fossil fuel and the bang for your buck contained therein.

I did the sums, yet still went the electric route. Although as a marine engineer I have the skills and knowledge to strip and re-build a diesel I do not have the workshop facilities and machines to do that. I also like to do it all myself. To convert to electric propulsion (apart from the shipping of the 2 x 8D AGM batteries) I have done the whole conversion, using off the shelf parts, using public transport (I have no car or motorcycle so have used the bus) and a small Musto shoulder bag. The electric system is far simpler to install. I also plan on gaining peace from noise (for the duration of the battery charge) compared to a diesel before I re-charge using fossil generated fuels either at a marina or by using a small hand portable Honda petrol generator and/or using that wee generator (500 Watts) as effectively a serial hybrid. Solar and wind and the pay back time don’t make sense for my kind of sailing at present, which is UK coastal to offshore based, with rarely a non stop passage greater than 100 nautical miles and no plans to be out in anything above a F6.

I’m also not in a hurry so I can wait for wind and if required a re-charge. I plan to sail more and motor less. Rather than go anymore deeply into this, I would also like to add that I think Eric’s comments are if you like made in isolation of other factors, as I have seen no discussion of duty cycle/engine run times and overall efficiency comparisons. Suffice to say I’ve put my money where my mouth is and by the end of this season I hope to show that I have made a wise, long term choice that is kinder to the planet in terms of life time costs and carbon footprint, with (and you can laugh now) a future option to not sail and wait the 7 to 10 days it would take to re-charge my batteries using wind/solar, when I can afford them. Indeed some folks can do that as their boat sits on a mooring waiting for their next fortnightly trip, but with no use of fossil fuel to re-charge.

On that point I’m glad to see your post and your desire for future, more eco conscious choices. In closing all I can say at this point is I started with steam, have done diesel and when I have quantifiable real world practical data, I will have done electric. The proof of the pudding is in the eating. Someone has to taste it before the rest of you and the taste won’t be for all. Time will tell.

In the meantime here is my finished conversion on a public Facebook diary page.

http://www.facebook.com/ElektraYachts

John Rushworth

Brilliant John. How about this http://www.chuckpaine.com/boats/24-double-ended-voyager-carol/ Totaly agree re ‘green’. It is a word I am carefully avoiding. I don’t know of any UK renewable energy marinas. I think it will happen, but not as long as business sells fossil fuel generated electricity at affordable prices. My electric drive is a scoot home one with a bit of added ooommf and battery time to get off a lee shore. I best shut up now till I’ve sailed her – this weekend for the first time!

RDE

Hi John,
Actually if you look at the whole system analysis for an all-electric plug in car running off a grid powered by coal you will find that it is still far more efficient and emits less Co2 than the same vehicle powered by diesel or gasoline.

RDE (Richard Elder)

Hi John,
Here is the original study from a number of years back that I based my comments upon. I doubt that it represents the whole story.

http://me222.files.wordpress.com/2007/05/twentyfirstcenturycar.pdf

Problem is, no government, and certainly no energy minister or corporation is willing to even try to estimate the real cost/benefit/risk analysis of a particular form of energy use and production. Business as usual and short term profit maximization are the only points of reference.

If you want to estimate the real cost of a gallon of gasoline used in the US to take the kids to soccer practice, you have to include the cost of fighting an endless series of wars in the Middle East to maintain control of the world’s largest and cheapest sources of oil. Ex CIA director James Woolsey put the real cost of gasoline int the US at $12 per gallon several years ago, and that didn’t even begin to estimate the potential economic cost of Co2 causing radical climate change.

So the “numbers” are much more complex than mere conversion and thermal efficiency studies would lead one to conclude.

Matt Marsh

The Tesla Motors article makes some valid points, but at first glance I do see one critical point they’ve biased in their own favour: They assumed that the electric car was being charged by a GE H-System gas turbine at 60% thermal efficiency.
Very few such power plants exist, and the ones that do exist are used mainly to handle peak loads when demand is high and other generators are maxed out. You need to cut that figure in half if you’re getting your power from a 1960s coal station, in which case the $109,000 Tesla isn’t much better than the ’93 Civic.
On the flip side, in Ontario you could charge the electric car at off-peak hours when, thanks to nuclear plants (which produce a constant power output 24/7) and hydro dams, electricity generation is cheap and nearly carbon-free.

But then we move to the marine case, and the electric car’s single biggest advantage- its regenerative braking- no longer applies. To get any decent range calls for obscene amounts of battery, and until we make another order-of-magnitude leap in energy density, that just isn’t going to fly outside of specialty applications.

You wouldn’t use Pb-acid batteries for an all-electric boat, of course, but the alternatives are still too expensive and not powerful enough. That will change, in time, but we aren’t there just yet.

John Rushworth

John,

One further thought on what we are doing to the planet etc. Have you considered approaching Dame Ellen Macarthur ref her new project in considering your design, build, lifecycle of an Adventure 40? This explains matters well https://www.youtube.com/watch?feature=player_embedded&v=Cd_isKtGaf8#! Her website is here http://www.ellenmacarthurfoundation.org/ and her ideas are starting to gain traction. http://www.ellenmacarthurfoundation.org/