Hybrid Theory

[pdf27]

Re-reading the HYMAR report, something occurred to me about hybrid drives. Reading through the report, hybrid systems appear to have three main gains:

1. Serial hybrids have a wider choice of reduction gears and in principle can use larger propellers for higher efficiency. In practice, to do this you need multiple motors in parallel or the motor efficiency drops. In a conventional installation, you can't take advantage of this with a parallel hybrid.
2. Diesel engines are very inefficient indeed at manouvering speeds - going electric has big gains here.
3. Depreciation and maintenance plus the poor fuel efficiency means that an engine alternator is a very inefficient way to generate house power. Adding a flywheel generator so this can be produced while the engine is running anyway.

Now, (3) can simply be gained by a flywheel generator on the engine and a large battery pack with high charge acceptance rate (LiFePO4), (2) is excessively complex and (1) probably doesn't save all that much fuel. However, reading the section of the report I've quoted below I started to wonder.

The propeller shaft speeds on parallel hybrid systems with internally-mounted electric propulsion motors, such as the flywheel-mounted electric machine in the HYMAR parallel test boat, run at engine speeds and as such are affected by the same constraints. However, externally-mounted electric propulsion motors in parallel systems, and the motors in serial systems, suffer no such limitations. The motors can either be designed to run at much slower shaft speeds, or else can be geared down to much slower propeller shaft speeds. The high-torque-down-to-zero-rpm means there is no potential for stalling. In principal, propeller shaft speeds can be slowed down to exploit the maximum diameter propeller that can be accommodated by the physical constraints of the installation (e.g. under hull clearances).
In a serial system, the principal limit on slowing down the shaft speed and increasing the propeller diameter is the physical constraints of the vessel, together with drag concerns on sailboats. Historically, many serial hybrid system replacements for existing diesel engines have reported substantial anecdotal increases in system efficiency in spite of the inherent limitations of serial systems outlined in this report. These gains have been attributed to the electric propulsion itself but are almost certainly gains at the propeller. The HYMAR propeller efficiency gains of 5% at full load and 15% at ‘off design’ operating points can be achieved with conventional propellers simply through this strategy of slowing propeller shaft speeds and increasing propeller diameter. However, this cannot be done in the parallel system which became the focus of the HYMAR project.

Essentially, at anything but manouvering speeds a direct drive diesel will be more efficient than an electric motor. And the optimum gear ratio and propeller sizing for a direct drive diesel will always be for a much higher reduction ratio and larger propeller than the diesel can turn without stalling when manouvering. That to me says that parallel hybrids are the way forward, but that the designs I've seen so far (which have the electric motor directly coupled to the output shaft and the diesel engine using conventional reduction gears) are wrong.

The propeller size should be set to be the largest that can physically fit in the space available, and gearing should then be used to match the engine peak power and RPM to the rotational speed at which the prop will consume this. Since the electric motors will be used for manouvering, no reverse gear is needed.
The electric motor should be sized to drive the boat at manouvering speed (say 3 kts), and appropriate reduction gear fitted such that it won't stall when turning the propellers at low speed. Note that this reduction gear will be significantly different to that for the engine, particularly as the best lightweight/efficient PMDC motors available tend to be high speed/low torque devices.

The only motor I've seen which gets close to this is the Hybrid Marine system using a Yanmar engine, which appears to have a step-up belt drive from the shaft to the electric motor. However, they don't mention anything about propellers so I assume it isn't designed to allow this.

The best solution to me would appear to be to borrow from automotive technology and fit a dual clutch (DSG) gearbox.



This would allow the propeller to be connected either to the engine (for conventional propulsion), the electric motor (for manouvering and regeneration) or both if you want to motor along and charge the batteries at the same time.

So the question is (never having got my paws on such a motor), what am I missing? Is this something that has already been done, a bad idea or does it have potential?

[a64pilot]

Look up the Prius "power split device" and see if that isn't something like what your talking about.
This wouldn't be for a sail boat would it? Great big efficient when motoring props would be high drag when off wouldn't they?

[Stumble]

There are two main problems with hybrids on boats 1) is the difference in house and propulsion loads 2) weight and volume of storage batteries.

1) a typical 40' cruising sailboat may have a 5kw power generator and need 40kw of propulsive power. There is no way to match two engines to this load that allow you more efficency than the current setup. There is a very small gain if you switch to an electric motor and two generators (40kw and 5kw) then just use the 5kw for propulsion al low speeds. But this gain is not enough to offset the power losses from converting motive power of the shaft to electricity then back to motive at the electric motor.

2) is simply an energy storage issue. Batteries are terrible at storing power with an energy density about 2% that of liquid fuel. So for every pound of diesel you take off the boat you have to add 50lbs of batteries to have the same available power. For in and out of the harbor only maneuvering it works, but for anything more it is a pretty big loss.

In reality the only boats that really see an advantage to hybrid propulsion are those that either have comperable house loads, or that can justify multiple smaller engines because they operate under widely varying power demands (harbor tugs).

[pdf27]

Originally Posted by Stumble

1) a typical 40' cruising sailboat may have a 5kw power generator and need 40kw of propulsive power. There is no way to match two engines to this load that allow you more efficency than the current setup. There is a very small gain if you switch to an electric motor and two generators (40kw and 5kw) then just use the 5kw for propulsion al low speeds. But this gain is not enough to offset the power losses from converting motive power of the shaft to electricity then back to motive at the electric motor.

That's true if you're expecting to cruise on the electric motors. If you're just manoeuvring to leave harbour, however, that isn't really true. The majority of the time the engine will be at idle or close to it, at which point most of the fuel is going to overcome internal losses in the engine. Assuming you're at 10% throttle for half the time leaving harbour and 0% the rest of it over 40 minutes, the useful energy used is ~1.3 kWh (1/3 hour at 4 kW, 1/3 hour at 0 kW). A Yanmar 4JH5E would consume 1.3 litres of diesel in that time (2/3 hour at idle power) - fuel that if burned to drive an alternator with the engine at cruise power anyway would produce in the region of 5 kWh. So an fourfold reduction in fuel consumption for moving in and out of harbour (combined with instant response from the motors - no need to shift gear or worry about the engine not firing up/stalling when you most need it) sounds pretty promising to me.

Originally Posted by Stumble

2) is simply an energy storage issue. Batteries are terrible at storing power with an energy density about 2% that of liquid fuel. So for every pound of diesel you take off the boat you have to add 50lbs of batteries to have the same available power. For in and out of the harbor only maneuvering it works, but for anything more it is a pretty big loss.

But that's exactly what I'm proposing (and indeed what the HYMAR report suggests) - in the example above to get out of harbour needed ~1.5 kWh which translates to about 10 lbs of batteries. Traditional practice is to divide the house and propulsion banks, but provided the starter battery is kept separate and the engine can be used as a charger I don't see why this would be needed.

Originally Posted by Stumble

In reality the only boats that really see an advantage to hybrid propulsion are those that either have comparable house loads, or that can justify multiple smaller engines because they operate under widely varying power demands (harbor tugs).

Thing is, if you're going to reduce the electric segment to manoeuvring only, the "engine" loading on the batteries drops a lot. To the extent that most long-distance cruisers out there probably do have comparable house loads in the time between entering/leaving a harbour or moorings/anchorage (1.3 kWh is ~100 Ah at 12V). I rather agree with a lot of your objections, but they're really to the early serial diesel-electric designs rather than to what I'm suggesting.

Originally Posted by a64pilot

Look up the Prius "power split device" and see if that isn't something like what your talking about.

No, it isn't.

Originally Posted by a64pilot

This wouldn't be for a sail boat would it? Great big efficient when motoring props would be high drag when off wouldn't they?

Only if you go for fixed propellers - feathering or folding would have a barely measurable effect on boat speed. Even in regenerating mode (so extracting 5kW/500A from the boat's motion) the experience in the HYMAR report was that it only knocked 10% of the boat's speed. Unless you're racing the additional drag of a larger folding/feathering propeller simply won't be noticeable.

[44'cruisingcat]

How much time do you spend at manoeuvring speeds?
Is it really worth spending tens of thousands of dollars to improve fuel efficiency here?
How many times would you need to leave/enter a marina for it to pay for itself in fuel savings?

[a64pilot]

Your point is, I guess that you can spend tens of thousands of dollars, increase tremendously the complexity of a system, one that spare parts won't be available for.
And save 1 L of fuel?
The one liter comes form your number of 1.3 L and a four fold reduction of fuel consumption, admittedly I didn't do the math, but a whole liter?
Coming from power boats, I'm still astonished at how fuel efficient a sailboat is, I just had to travel about 800 miles in eight days, and if I didn't have the Diesel, I'd still be out there.

[appick]

You're worried about the diesel not starting and I guess are saying that the electric motors would work all the time on demand... untrue especially in corrosive environments. Having worked in the food manufacturing and maintenance industry for the last 5 years I've seen hundreds of electric motors fail to start. What the food industry has in common with sailing and salt water is corrosive environments. Using sanitizers to clean the equipment is standard practice and these are pretty corrosive. Even stainless steel is no match eventually. What I'm getting at is manufacturers of equipment use corrosive chemicals to speed up the wear testing to say test it in a corrosive environment for 5 years they don't actually put it somewhere for 5 years. They put it in a container with corrosives and have an equation to figure out the levels of chemicals and time to equal how many years. In the end I've never seen a sealed electric stainless steel motor go for more 3 years here. What that equals in real world sailing is anyones guess but it will fail. At costs exceeding $5000 for just some of these mid range electric motors at our buying quantities I wouldn't want know what they are going to cost the average guy.

Say a motors lasts 10years of casual use say at $8000 for a price you can buy, a diesel can last longer and cost less, and as noted still give you better efficency on a sailboat at cruise. Which if you're using your boat is where you spend most of your time motoring. In and out of a dock/ marina shouldn't take you 40min, but I guess everyones got a different setup there.

Anywho I know it's just a thought experiment but I think it's pretty well defeated if you're looking to up effiecies below 3knts at least in the actual application. Cheers!

[appick]

Also as to the starting battery the same as the storage. I doubt you'll be able to find a starter rated for the voltage that makes the house battery bank efficient. Usually starters are 6v (really old stuff), 12v (almost everything now days), and maybe some 24v stuff as this is pretty common boat voltage in Europe and elsewhere.

[Hyprdrv]

I wasn't able to figure out where the whole report was but this is a summary listed on the front page, left side under "A hybrid Future".

For my personal background do a search of my other posts on Electric Drives.

About 4 years ago several of the principles involved with HYMAR including Nigel came aboard "Electra Glide". We spent the morning talking and they where impressed with the system Solomons Technologies had installed along with the "upgrades" that have been done. This was on a 41' Sailing cat that was Electrified in 2004 right from the factory. The system is direct Drive (E-motor to prop) and running on 144V. Over the last 10 years I've never had to do an oil change, tune-up, engine coolant flush, for that matter I've had to do nothing to the motors. The only part of the system that needed to be replaced was a Motor Controller of which there are 4 of since the motors are actually 2 motors Siamesed together X 2 (port and starboard) so in fact I have 4 motors. The motors are good for like 200,000 hours of run time until a $5 baring would need replacing. The batteries originally from the boat manufacture where cheap junk and replaced with a set of AGM's giving around 3 hours of run time. They are know going on 8 years old and will need to be replaced with a set of LiFePo4's at close to $9,000 BUT they will give me 6 hours of run time at 1/3 the weight and estimated 3 times the life so infarct are about the same cost as a standard Lead battery.
Are we talking sailboats here or powerboats?
The report seems to be more in line with Powerboat efficiency than sailboats when talking above 6 knots. My best efficiency is below 6 knots which the report states is where the highest efficiency occurs for electrics. Yes I have a 16KW genset on board to run all day to charge batteries and operate my motors but at under a gallon per hour I'm quite happy to have as a backup for those long no wind or head wind runs. Over the last 5 years I've used 20 gallons of diesel total. I've been more concerned about the fuel going bad than how much I burn.
Europe has mandated that quite a few of their lakes and canals (starting to happen here in the states) are to be closed to fossil fuel boating so have led the way with Electric Drive systems. There are a lot of boats converting to electric including here in the states. Not so many larger boats as the smaller ones leading the wave of new technology in this field. I kept reading some of the HYMAR info with dates back to 2011 which in this field is old info. Battery technology and motor improvements has leaped forward over the last few years.
I never have understood the belt drive reduction gear side of doing this. How many posts are there here and elsewhere dealing with bad saildrives and such that adding another gear system or all those spinning parts doesn't make any sense to me but hey what ever it takes I guess.
I have 1 moving part in the motor.
I convert 144V to 12V using a converter/charger.
I use my generator's alternator to do one thing, charge the start battery.
I've upgraded the monitoring system to see each batteries state of health.

In summery I am extremely happy with my system and how it works as is a lot of others who have converted to Electric Drive.

Steve in Solomons MD

[pdf27]

Originally Posted by a64pilot

Your point is, I guess that you can spend tens of thousands of dollars, increase tremendously the complexity of a system, one that spare parts won't be available for.
And save 1 L of fuel?
The one liter comes form your number of 1.3 L and a four fold reduction of fuel consumption, admittedly I didn't do the math, but a whole liter?

Point is, it's a litre every time. Over the life of a boat, that's presumably going to add up. And I'd take issue with the "tens of thousands of dollars" - that'll be true right now, but probably won't be true in the future when the economies of scale start to kick in. Right now all we're seeing are the early adopters, who will be using what are essentially handmade systems. Once we start seeing mass produced motors become available (probably from electric cars) then your tens of thousands of dollars will drop to a few hundred. Suddenly the economics start working the other way, very quickly.

Originally Posted by appick

You're worried about the diesel not starting and I guess are saying that the electric motors would work all the time on demand... untrue especially in corrosive environments. Having worked in the food manufacturing and maintenance industry for the last 5 years I've seen hundreds of electric motors fail to start. What the food industry has in common with sailing and salt water is corrosive environments. Using sanitizers to clean the equipment is standard practice and these are pretty corrosive. Even stainless steel is no match eventually. What I'm getting at is manufacturers of equipment use corrosive chemicals to speed up the wear testing to say test it in a corrosive environment for 5 years they don't actually put it somewhere for 5 years. They put it in a container with corrosives and have an equation to figure out the levels of chemicals and time to equal how many years. In the end I've never seen a sealed electric stainless steel motor go for more 3 years here. What that equals in real world sailing is anyones guess but it will fail. At costs exceeding $5000 for just some of these mid range electric motors at our buying quantities I wouldn't want know what they are going to cost the average guy.

Say a motors lasts 10years of casual use say at $8000 for a price you can buy, a diesel can last longer and cost less, and as noted still give you better efficency on a sailboat at cruise. Which if you're using your boat is where you spend most of your time motoring. In and out of a dock/ marina shouldn't take you 40min, but I guess everyones got a different setup there.

Anywho I know it's just a thought experiment but I think it's pretty well defeated if you're looking to up effiecies below 3knts at least in the actual application. Cheers!

Hang on there. You're saying a diesel will last longer than an electric motor - why? The diesel is much harder to seal (having to suck in salty air), runs at high temperature, has all sorts of nasty combustion products floating around inside, etc. Electric motors - particularly the brushless DC style - have none of those and about the only material not found in diesel engines (copper) is so unreactive they used to coat ships in it. I'd bet if you put a marine diesel engine in the same environment that is killing your electric motors it would die significantly faster.

Originally Posted by Hyprdrv

I wasn't able to figure out where the whole report was but this is a summary listed on the front page, left side under "A hybrid Future".

A copy of the final report is here: http://autoprop.info/Latest_News/pdfs/HYMAR.PDF

Originally Posted by Hyprdrv

For my personal background do a search of my other posts on Electric Drives.

About 4 years ago several of the principles involved with HYMAR including Nigel came aboard "Electra Glide". We spent the morning talking and they where impressed with the system Solomons Technologies had installed along with the "upgrades" that have been done. This was on a 41' Sailing cat that was Electrified in 2004 right from the factory. The system is direct Drive (E-motor to prop) and running on 144V. Over the last 10 years I've never had to do an oil change, tune-up, engine coolant flush, for that matter I've had to do nothing to the motors. The only part of the system that needed to be replaced was a Motor Controller of which there are 4 of since the motors are actually 2 motors Siamesed together X 2 (port and starboard) so in fact I have 4 motors. The motors are good for like 200,000 hours of run time until a $5 baring would need replacing. The batteries originally from the boat manufacture where cheap junk and replaced with a set of AGM's giving around 3 hours of run time. They are know going on 8 years old and will need to be replaced with a set of LiFePo4's at close to $9,000 BUT they will give me 6 hours of run time at 1/3 the weight and estimated 3 times the life so infarct are about the same cost as a standard Lead battery.
Are we talking sailboats here or powerboats?
The report seems to be more in line with Powerboat efficiency than sailboats when talking above 6 knots. My best efficiency is below 6 knots which the report states is where the highest efficiency occurs for electrics. Yes I have a 16KW genset on board to run all day to charge batteries and operate my motors but at under a gallon per hour I'm quite happy to have as a backup for those long no wind or head wind runs. Over the last 5 years I've used 20 gallons of diesel total. I've been more concerned about the fuel going bad than how much I burn.
Europe has mandated that quite a few of their lakes and canals (starting to happen here in the states) are to be closed to fossil fuel boating so have led the way with Electric Drive systems. There are a lot of boats converting to electric including here in the states. Not so many larger boats as the smaller ones leading the wave of new technology in this field. I kept reading some of the HYMAR info with dates back to 2011 which in this field is old info. Battery technology and motor improvements has leaped forward over the last few years.
I never have understood the belt drive reduction gear side of doing this. How many posts are there here and elsewhere dealing with bad saildrives and such that adding another gear system or all those spinning parts doesn't make any sense to me but hey what ever it takes I guess.
I have 1 moving part in the motor.
I convert 144V to 12V using a converter/charger.
I use my generator's alternator to do one thing, charge the start battery.
I've upgraded the monitoring system to see each batteries state of health.

In summery I am extremely happy with my system and how it works as is a lot of others who have converted to Electric Drive.

Steve in Solomons MD

The reduction gear side of things is simple - the efficiency of high torque/low speed motors like you have and the high speed/low torque motors that are generally used elsewhere when coupled with a reduction gear works out pretty much the same. High speed/low torque motors are much more common and so generally work out cheaper, even including a reduction drive.
In the battery part of the report they're concentrating on lead-acid, but admit at the end that they've been kind of leapfrogged by the technology and go kind of quiet about how badly.
Their conclusion is that boats like yours get higher efficiency because the electric motors are acting as a giant reduction gear, so allowing you to use larger and more efficient props - more than outweighing conversion losses. They also suggest that a direct mechanical reduction drive to allow the same propellers would be marginally more efficient, but would not allow slow-speed manoeuvring without stalling the engine - which is where my idea at the top fits in.

[u4ea32]

Sailboats powering with diesel are far more fuel efficient than powerboats. Several times as efficient, like 800%, which is much more significant than 10% or 15% or even the 400% gain when maneuvering mentioned in the report. Sailing is far more fuel efficient than powering by diesel.

So the right way is a sailboat that you would rather sail than power.

This is quite unlike most cruising sailboats. Boats can be very fun to sail even in ghosting conditions. But that requires very high sail area to wetted surface ratios. Easy to do, but cruisers just choose not to have high powered boats. A stubbornly poor choice, in my opinion.

If you have a fun-to-sail sailboat, then your powering needs collapse to just getting in and out of tight marinas. Which would amount to a few liters per year, perhaps, so the efficiency of electricity over diesel, or diesel over gas, is truly a silly thing to worry about.

And the real epiphany is: getting in and out tight marinas is a lot easier with twin outboard engines than a single, especially a single inboard.

So after playing with this problem for many years, I finally came to the conclusion -- after Ibex, after several hours of Nigel -- I decided the best approach is two 15hp gas outboards. For at least the following reasons:

1) cheap to install
2) cheap to replace when they wear out
3) no electrolysis nightmares in marinas
4) no drag when under sail
5) easy to clear the prop when I run over a mooring line
6) easy to work on while standing up outside
7) gasoline is easier to find globally, as every panga and scooter uses gas, not diesel
8) diesel smells really bad, the smell makes most people sea sick
9) twin engine maneuvering is MUCH easier than with a fixed inboard single engine
10) outboards are much, much cheaper to repair, especially in remote places where pangas rule
11) outboards are virtually silent, without vibration, compared to diesels or gas inboards
12) high current battery systems are very dangerous!
13) easy to go with no generator with today's modern photovoltaics and efficient electrical devices (LEDs), as long as the refrigeration is very well insulated.
14) very small fuel tanks are good in so many ways.

If good electric outboards ever appear, then it will be very easy to replace the gas outboards. Solar can easily provide the needed juice to get in and out of the odd tight marina, or cruising through locks.

But using electric for sustained operation? Nope.

[appick]

Your obviously sold on the system you are touting or trying to make. As just exampled by the guys $9000 battery purchase after a few years because the originals were junk. For me $9000 buys an engine! Maybe a rebuilt or lightly used but it'd definetly be a good running unit. I'm not saying the the economics won't change. History says they always do. But to say in a few years what was worth $10,000 will be a few hundred?!? I think your dreaming there sure maybe in 20-30 years but a few being 1-2 ha!

As to 1 moving part?!? I believe if you look closely you'll find you have 3 per motor, and with 2 motors per shaft that makes 6. 2 bearings in each motor move as well as the shaft. Also you aren't doing any oil changes or maintenace on the generator?

As I stated in corrosive enviroments I see motor starters fail and therefore motors fail to start. I also see on a regular basis coil windings go bad, burn up, get a short, or too high of resistance. Plenty of things to go wrong with an electric motor. Sure I won't argue there are far fewer moving parts than an interal combustion engine, thats a given.

Salty air sure but that same air is surrounding your electric motor, electronics, contactors and wiring. If it gets in the wires or circuit boards guess what fails. A internal combustion sucks it in along with fuel and oil that coats the metal surfaces for protection. Want to guess what happens when a corrosive gets into an electric motor? I'll tell you its green,powedery, black, and or burnt.

I'm not a dino fuel zealot, nor am I a electric one. I'm not saying someone wont come up with and efficient system for constant cruising and operation that works effciently at the boats hull cruise speed. I'm pretty sure it will happen, but to compare the costs and reliabilty of the early systems to the current field of diesel propulsion you find that diesel is cheaper, cruises at the appropriate speeds, and more reliable.

As with any technology the first models always find all the problems and improve upon themselves from there. So it will happen I'm just being real about the limits of current systems and current prices. Not what could/would happen in an ideal future. Either way it'll be interesting to watch where and how the technology develops. I see there is already a solar runabout that looks pretty neat and can cruise at something like 10knts for extended periods and slower speeds constantly. The name escapes me it is black carbon fiber about 20ft+ long from a European manufacturer, saw it on the TV show.

[Hyprdrv]

"Your obviously sold on the system you are touting or trying to make. As just exampled by the guys $9000 battery purchase after a few years because the originals were junk. For me $9000 buys an engine! Maybe a rebuilt or lightly used but it'd definitely be a good running unit. I'm not saying the the economics won't change. History says they always do. But to say in a few years what was worth $10,000 will be a few hundred?!? I think your dreaming there sure maybe in 20-30 years but a few being 1-2 ha!"

Let me clarify this:
The original batteries from Lagoon have always been known to be inferior to anything out there. They installed more of them as a propulsion pack in 2004 when the boat was new. They lasted about 2 years. The pack was replaced with a pack of state of the art AGM's (8 years ago) which are still going strong but are old tech compared to the LiFePo4's available now. I don't have to replace them, I'm getting ready for some extended cruising and will replace them in a year or 2. The new LiPo's could last over 20 years or more but there is no record as to how long they will last do to many factors you can read elsewhere so I'll say 10 years. How can you state the life in years unless you know the charge/discharge cycles and frequency? There are newer bats out there that may change the game entirely. This is the weak link to the system and one that is moving the fastest to correct.

As to 1 moving part?!? I believe if you look closely you'll find you have 3 per motor, and with 2 motors per shaft that makes 6. 2 bearings in each motor move as well as the shaft. Also you aren't doing any oil changes or maintenance on the generator?

I stand corrected, 2 ware points, 2-$5 barrings per motor, the 1 rotating stator is brush-less. Also to correct the life cycle of the barrings 150,000 hours to be precious. O and before you want to add the cost of the labor I can do it myself as well as pulling the motors and carrying them out.
How many rebuilds for your diesel in 150,000 hours?

Yes I change the oil and do the yearly maintenance on the genset but with this size boat we mostly have gensets for the creacher comforts our wives require and there are very little maintenance differences between a 2KW and 16KW other than fuel.

Steve in Solomons MD

[Stumble]

Frankly I see the sailboat market right now as being broken into two seperate segments.

The first is the daysailor who is back at the dock most days and just needs enough propulsion to get in and out of the harbor. They could easily switch to electric today and be fine. Their power demands are low, don't need much run time, and the simplicity of a pure electric drive system works.

The second market are cruisers. They need a drive system that can move the boat at a substantial percentage of hull speed for days on end. Pure electric won't work here, and the generator needed to supply this amount of power is the same as the current drive motor installed in all sailboats.


The problem is that most daysailors don't really care enough about their propulsion system to spend the money or time to make the switch. And it prevents them from ever being able to rely on their engine for more than a few minutes, maybe an hour. And any efficiency gains here are meaningless. Let's say an electric system would save me 90% of what I spend on my 38' daysailor. Last year I burned 4 gallons of fuel, and I sail at least once a week, normally twice. So my fuel bill drops from $15 to $1.50, who cares?


The cruisers on the other hand will not accept a system that limits their powered cruising range... So how do you supply enough power to the drive motors to get the range necessary (since batteries are woefully incapable of this much power). The only way to really do this is with a Diesel engine sized to provide that much power. So you wind up with a couple of large diesel generators instead of large diesel propulsive motors.

Of course their is a small gain to be had by being able to move them to where the weight is best, a little from being able to use different sized generators to more closely match the power draw but this is pretty minimal compared to the mess of carrying multiple spare parts and the weight associated with them.

Frankly I love the idea, but the batteries just aren't there yet to act as a smoothing agent for power draw.

[Andrew Troup]

I'd be interested to know why, four years after the interim Hymar report (which took 18 months) it seems there are no actual results to report; the program seems to be largely aspirational at that time. That's the fun phase, the easy phase, with everyone full of hope, and the intoxicating freedoms of a clean slate apparently stretching to infinity.

This was an EU funded undertaking, as I understand it.

Surely it should at least explain why it has not reported?