diesel-electric vs normal diesel - which is more economical?

[benjamino]

Ok so I'm thinking ahead here - one day diesel will probably be extremely expensive (if it isnt expensive enough already) so I want to be in a position to swap to renewable energy at the point where that becomes easily a cost effective option. So this would mean getting a diesel-electric propulsion system in place for the time being so later it can turn into a solar-electric propulsion system.

 

By the way I am talking of a new build here not modifying an existing boat.

 

So as far as I can see these are the options:

 

1. Diesel Generator powerful enough to power lynch motor by itself - used in conjunction with battery bank for leisure use and limited-range propulsion without the generator running.

 

2. Diesel Generator not powerful enough to run lynch motor by itself, propulsion only available by using charged batteries, range could be extended by running generator to reduce drain on batteries.

 

3. Diesel propulsion engine with generator attached, like Beta Marine Genset, as long as this can be used to charge leisure batteries without being in gear and without damaging the engine. Obviously propulsion with this option could never be solar powered.

 

So - what I need to know is this. Is either option 1 or 2 going to use more or less fuel to propel the boat per mile than option 3. If so it will mean until solar power is viable (and indefinitely in winters) the boat will cost more per cruising mile if using options 1 or 2 so it will probably still make sense to use option 3 and then use solar for leisure use when it becomes a bit more cost effective.

 

I know a few people on here have diesel-electric systems so hoping they have some economy figures in terms of miles per gallon as it were. Thanks!

[John Orentas]

Hi Benj.

 

I hate to seem like a wet blanket but you are I think the 37th to come up with the scheme on this forum alone, I used to be a design /development engineer and I know this kind of original work is very, very expensive..

 

The mistake that most similar projects suffer from is that people think about the problem back to front in that the final drive needs more power that you expect, at least 25 hp for a reasonably sized steel boat, Lynch motors not big enough.. The only advantage you can possibly get is the use of a much smaller engine which will run at an economical 'flat-out' speed most of the time putting electrons into your extensive battery bank, but that economy will be rapidly eroded away.

 

These things have a lot of appeal on several fronts, but remember every time we convert energy from one form to another there will be inevitable massive losses, bear in mind too that boat propulsion systems have evolved over a hundred years, you would struggle to out-do a conventional set-up by any criteria at all.

 

P.S. One thing I would like to see someone do (I am past it now) is to to convert a milk float or stacker truck to a boat.. Motors, control system, batteries, charger, it's all there at low cost and zero risk, but don't imagine it will save any money.

[alan_fincher]

One thing I would like to see someone do (I am past it now) is to to convert a milk float or stacker truck to a boat.

Would this be why one sometimes sees people crewing boats that are apparently wearing milkman's hats ?

[Alastair]

You can combine Lynch motors - I believe John Who bought my old boat is putting in a couple of 30Hp models. 60Hp is enough grunt for most inland boats.

 

However, it is very expensive. As JO says, there are energy losses in the conversion process, so it is usually less efficient.

 

There are some big barges purely running on solar power - the DBA featured one in an article. In summer, AFAIK, they could cruise for over 40miles a day without draining the batteries.

 

The efficient, green answer is simple:

 

For canals, get a horse.

 

For rivers and estuaries, get a mast and sail.

[benjamino]

For canals, get a horse.

 

Its funny you should say that - I was wondering about that the other day. Actually tried to search on the internet to see if anyone was doing it - all I found was tourist attractions. Is it even allowed? Would be an excellent solution to the fuel price problem! You could even dry its dung out and burn it!

[jayjayranger]

this is what i am doing 2 lynch motors with controlers 3800pounds 500 amp at 48 volt 2 volt cells batteries2000 pounds kohler generator 11kw 7000 pounds inverter comdi either 6kva studer or 5kva victron quattro 3000pounds helm control 600 pounds on a 60 by 12 sailaway

[larkshall]

Just to be different and be relatively green, I'm working on LPG engine and hydraulic drive/generation etc.

 

why?

 

gas is green

lowest tax rate on fuel

employ quieter spark ignition engine.

Engine can be located anywhere inc transverse mounting

 

Downside.

 

Gas safety

Designing gas proof bulkhead.

[Teadaemon]

IIRC on a previous thread on this subject I posted a link to several articles in Professional Boatbuilder magazine that discuss the pros and cons of hybrid propulsion systems. As I remember them, in most situations using a diesel-electric hybrid system will provide little, if any improvement in fuel consumption over using a modern common-rail diesel engine (but may well be significantly more efficient than an old diesel engine of traditional design). Having said that, one of the few situations where the diesel-electric system did show potential for being more efficient (IIRC by about 10%) than even a modern engine was in a canal boat, particularly one where the engine is run in neutral for battery charging on a regular basis. (I can't remember why exactly, if you want the details I'd suggest looking up the articles.)

 

It can and has been done, but in order to work properly the whole propulsion and electrical systems need to have been designed from the ground up with this in mind. This is not a trivial task, and unless you really, really like the idea of a lot of book-learning and maths, it's probably one that's best left to a qualified naval architect. (It'd be well beyond the comfort level of most builders of canal boats.)

[barge sara]

We're converting Sara to diesel electric. Kit is:

 

4 Lynch motors mounted in a frame with kevlar belt reduction drives to a single shaft.

4 4QD motor controllers.

825 AH 48 volt traction battery.

13 KW 48Volt Fischer Panda cocooned generator.

 

The basic theory is that, although we need 50 plus HP available, most of the time we're only using between 5 and 10, so will run on batteries, with the generator firing up as required (voltage sensing auto-start), either to recharge or to provide addtional power to the batteries on high demand.

 

The fuel consumption should be much reduced for two reasons. First, when the generator is running it will be running at its designed optimum speed, not thumping away on tickover as do most boat engines for most of the time. Second, it will only be running for maybe half the time we are cruising. I know there are charging losses, but I beleive they will be more than compensated by the generator efficiencies.

 

In addition we have two Victron Phoenix combis which will provide a 70 amp charge from the mains, which for short trips is much cheaper than burning diesel in any shape or form. They will also give us 6KW of domestic 240AC, allowing us to abandon gas and go all electric, which will give us a saving over bottled propane as well as a win on safety.

 

Capital cost is high, over £25K once bits and pieces and fabrication are added, compared with maybe £15K for a conventional drive and small generator. I wouldn't do it for a boat that isn't going to move much, but we intend cruising Sara extensively in Europe over the next 10 years, so should at least break even; the price of diesel is only moving one way! It will also be very quiet.

 

Progress to date: New diesel tanks, batteries, victron combis and generator are in. Generator awaits commissioning. The motors are mounted in the frame with reduction drives all assembled ready to drop in, then there's the controls to install. Hoping for sea trials in July.

 

John.

MV Sara.

[Tony Brooks]

We're converting Sara to diesel electric. Kit is:

 

4 Lynch motors mounted in a frame with kevlar belt reduction drives to a single shaft.

4 4QD motor controllers.

825 AH 48 volt traction battery.

13 KW 48Volt Fischer Panda cocooned generator.

 

The basic theory is that, although we need 50 plus HP available, most of the time we're only using between 5 and 10, so will run on batteries, with the generator firing up as required (voltage sensing auto-start), either to recharge or to provide addtional power to the batteries on high demand.

 

The fuel consumption should be much reduced for two reasons. First, when the generator is running it will be running at its designed optimum speed, not thumping away on tickover as do most boat engines for most of the time. Second, it will only be running for maybe half the time we are cruising. I know there are charging losses, but I beleive they will be more than compensated by the generator efficiencies.

 

In addition we have two Victron Phoenix combis which will provide a 70 amp charge from the mains, which for short trips is much cheaper than burning diesel in any shape or form. They will also give us 6KW of domestic 240AC, allowing us to abandon gas and go all electric, which will give us a saving over bottled propane as well as a win on safety.

 

Capital cost is high, over £25K once bits and pieces and fabrication are added, compared with maybe £15K for a conventional drive and small generator. I wouldn't do it for a boat that isn't going to move much, but we intend cruising Sara extensively in Europe over the next 10 years, so should at least break even; the price of diesel is only moving one way! It will also be very quiet.

 

Progress to date: New diesel tanks, batteries, victron combis and generator are in. Generator awaits commissioning. The motors are mounted in the frame with reduction drives all assembled ready to drop in, then there's the controls to install. Hoping for sea trials in July.

 

John.

MV Sara.

 

 

I await your results with great interest, but what is your projected life for the batteries and how much will they cost.

 

Thanks

[barge sara]

I await your results with great interest, but what is your projected life for the batteries and how much will they cost.

 

Thanks

 

Lifetime, looked after properly is in excess of ten years. Guarantee is five years.

Not cheap, this is a tonne and a quarter of lead acid cells for which we paid about £3.5K.

[benjamino]

I await your results with great interest, but what is your projected life for the batteries and how much will they cost.

 

Thanks

Agree - I would love to have the information to just work all this on paper, so we could come up with a cost per mile with each system. This way it would be easy to see at what cost diesel needs to be to to make a hybrid system with its battery expense worthwhile.

 

Also cost per amp into the batteries when charging from generator vs cost per amp when charging from an engine not running out of gear.

[NB Alnwick]

In traditional traction/propulsion arrangements the principle benefit derived from either electric or hydraulic transmission is that it enables the load to be taken up smoothly from a standing start while the engine is running at reasonably efficient power output speed. As a result it is possible to achieve high initial starting torque from a relatively low powered engine. This consideration is irrelevant in small boat applications where there is little starting resistance and, in these circumstances, a direct drive from a slow running diesel engine is more efficient that any other form of transmission. So for propulsion purposes on narrow boat, it would be difficulty to justify the expenses of electric transmission.

 

Using batteries for propulsion involves high capital cost and higher comparitive running costs if charged up from a diesel generator because batteries do not represent the most efficient method of transferring power.

 

On the other hand, if the overriding requirement is to charge batteries and/or provide domestic electricity, surely it would make more sense to have a separate economical generator geared to that particular requirement.

 

If anyone can produce accurately measured comparative costs (both capital and running costs) between similar boats equipped with each type of transmission I would be very interested to see them.

[barge sara]

In traditional traction/propulsion arrangements the principle benefit derived from either electric or hydraulic transmission is that it enables the load to be taken up smoothly from a standing start while the engine is running at reasonably efficient power output speed. As a result it is possible to achieve high initial starting torque from a relatively low powered engine. This consideration is irrelevant in small boat applications where there is little starting resistance and, in these circumstances, a direct drive from a slow running diesel engine is more efficient that any other form of transmission.

 

Not competely irrelevant but a different take. We've all been in the position of repeatedly going in and out of gear to maintain a speed less than that provided at tickover. Electric drive will allow slow speeds right up from zero.

 

So for propulsion purposes on narrow boat, it would be difficulty to justify the expenses of electric transmission.

 

Agree, for the average narrowboat doing relatively low cruising hours.

 

On the other hand, how do you justify the exppense of running a boat at all?....

 

John.

MV Sara

[pwl]

There was a stand at Crick with a hybrid - Beta Marine I think. I dont have any details but may be worth a google.

 

P

[benjamino]

On the other hand, if the overriding requirement is to charge batteries and/or provide domestic electricity, surely it would make more sense to have a separate economical generator geared to that particular requirement.

 

I would say I'm after domestic power generation as a primary use, cruising would be fairly minimal. So i guess it would make sense to get a separate generator for domestic use/charging domestic batteries. It just seems mad getting two engines on board when one could do the job of both.

 

There was a stand at Crick with a hybrid - Beta Marine I think. I dont have any details but may be worth a google.

 

P

 

this one I think: http://www.hybrid-marine.co.uk/5.html - theres another thread on it here: http://www.canalworld.net/forums/index.php?showtopic=15133

 

It does sound interesting for it's efficiency but I've no idea of costs.

[Chris J W]

Its funny you should say that - I was wondering about that the other day. Actually tried to search on the internet to see if anyone was doing it - all I found was tourist attractions. Is it even allowed? Would be an excellent solution to the fuel price problem! You could even dry its dung out and burn it!

 

How much would it cost to fuel (feed) and maintain a horse each year, though? I bet these days you wouldn't be allowed just to leave it stood out over night (er, which I assume they used to do if no-where handy nearby?) and you'ld have to have it stabled.

 

As well as burning the dung, you've also got a good sideline for fertilizer, and when the beast has reached the end of its years there's several pretty good stews to be had, too! (The meat would probably be far too tough for normal roasting by then, I would have thought)