Electric wheels?

[Guest]

Anybody have any experience of the electric auxillary motors made by solomon technology www.solomontechnologies.com. Looks like a good idea and since I am redoing electrics and engine might be economical. It sound radical but is really just a small version of a diesel electric train add a battery for short runs and a water turbine, so more like a new application?

Roly, Voya Con Dios, Glasson, Lancaster

 

[kingfisher]

It exists

Let us know if this works. I'm dying to get rid of that smelly, noisy green monster in my boat.

Last year VETUS put a standard electrical propulsion system on the market. Ckeck it out:

http://www.vetus.nl/producten/mainns.asp?productid=92&lang=2

It's small
No gearbox
Delivers about 5hp I believe
Less stress on the boat

The trouble with electric drives is the range, of course. But for the serious sailor, consider this: electric propulsion, coupled to a generator (which you need anyway).

I for one am seriously considering it for the next reengineing job.

Obi-Wan

 

[Guest]

Re: It exists

Vetus unit is good for tender/small workboats but to small for a main engine (and expensive!) Also does not give generating capacity as a water turbine under sail which is a big plus of the wheel.

As far as range, yes desil electric is the way to go I am looking at a small air cooled desil generator which, on a ten gal tonk would give aboat 24h at full power! Water cooled geny would be better but they don't make them small enough.

The other point about range is that typical use will be to get out of harbour, go sailing, back into harbour. While sailing the wheel acts as a turbine so recharges the batteries, effectivly you 'refuel' whenever the wind blows. The designer claims that in twelve months he has never had to run the gen set, but do I believe him?

Also looking at whether NiCad cells might be better as they might avoid problem of sufation and allow deeper discharge, Keeping bank 'conditioned' in harbour is posing a problem where shore power is not available.

Roly, Voya Con Dios, Glasson, Lancaster

 

[RobertMartin]

Well a man after my own heart!!!

I have been looking into electric propulsion for the last 6 months.

The benifits include,
no gear box - direct drive.
1/4 size engine eg 30hp diesel would need a 10 hp electric max, due to 90% drive from engine to prop..
Can carry space motor on board
Silent
Less weight - no fuel need - more berth / storage / battery space..
No smelly, oily exhast
No seacock needed
Instant thrust..

Sounds to good to be true, it is..

The main problems are -

The engine can not be used to charge.
Needs a very large battery bank.
You really need to use AGM or Gell batteries to avoid killing the cells..
The engine will only run for so long without a charging source.
Needs wind and sun charging to keep batteries topped..

But I agree with you, I hate my deisel, it stinks, it always breaks down, its 100 years behind all other engines and in my eyes, it spoils a great sail..

I am still going to change to an electric system at some stage, the fuel cell would fix all the down sides to electric, until then you will need at least 5 100am ( min ) batteries...

Good luck..

Ps. look at www.boat-links.com/boatlink.html and look up electric boats. lots of info there....




Bobby aka Seawolf..
Freedom is the song of your soul..

 

[Guest]

Agree with you list of good points and for most motors also the problems but look at Solomon technoligies electric wheel (apparently powered the mars rover) http://www.solomontechnologies.com This unit acts as a terbine when under sail and not only recharges its drive battery but produces more than enough energy to run everything on board, including a cooker. So you get rid of the gas bomb as a bonus! The only limitation seems to be range. About 5h seems practical in reasonable conditions. If you want the engine for longer range in calms etc then it needsto be linked to a geny. Although this means you are back to having a diesel on boad it can be a small totaly enclosed job so less noise & fuel. For a 31ft long keel boat I am looking at a 3-4kw unit for standby power but only expect to use it on rare occasions when I have to be somwhere and cant wait for the wind or prolonged calm spells in harbour when away from shore power.

Roly, Voya Con Dios, Glasson, Lancaster

 

[Guest]

Hi Roland...

David Tether (Solomon/ElectricWheel) has been active recently aboard the Design Conference at:

http://boatdesign.net/forums/showthread.php?s=2b8f0a069b08035cf2126ad0fdbd0f1c&threadid=676

big, big thread, on the EWheel and electric generally...

Cheers

Lock

 

[Trevethan]

My ex-girlfriend's father was involved in the electric wheel principle. Presumeably the Solomon venture since he only lived down the road, though at the time I think it was called Greenseas.

He had a boat he was fitting out with the drive, and the time I saw it, on shore in Annapolis, the aft cabin was pretty much full of batteries prior to installatiion. The system sounds great though and should be more than capable of driving smaller yachts.

I am interested in it for Gayle Louise - with a genny. However she is 44 feet long and displaces about 16 tonnes... including about a tonne of smelly diesel engine. The big motor they sell might be man enough for the job, but I am not keen to be an early adopter. While my ex and I were together I was looking at a boat to take to Australia and he offered to re-engine it for me as a marketing strategy. Wonder if he would still make the same offer... doubt it as she and I parted on bad terms... oh well!

 

[Robin2]

Another 1st for the date-slip system - bringing such interesting stuff back to the top.

If it takes, say, 15 hp to drive your boat at 6kt and your sails can also drive it at 6kt isn't it reasonable to assume that if you were using your "wheel" as a generator it would bring your boat to a halt!

There really is no such thing as perpetual motion !

 

[Trevethan]

I don't think this is how it works in practice - I imagine, looking at the way it works that the gears when in generator mode allow the prop to spin nice and easily in the water stream. Look at it this way - your 15 horsepower diesel drives you through the water at say 6 knots with the control lever in neautral allowing the prop to spin.... does you speed half when you oput the control lever in gear and stop the prop from spinning?

I expect that a two or three hour sail is required to to recharge one hour's worth of motoring

 

[Guest]

Robin2:
Another 1st for the date-slip system - bringing such interesting stuff back to the top.
If it takes, say, 15 hp to drive your boat at 6kt and your sails can also drive it at 6kt isn't it reasonable to assume that if you were using your "wheel" as a generator it would bring your boat to a halt!
There really is no such thing as perpetual motion !

Some recent experiences, as related by Tether:
Continuous Running....We have a boat(CAL 34) that regenerated it's way from Los Angeles to Tahiti....we have a Cheribini 44 that came to Maryland from England on 300 gals of fuel with Ice Maker, AC, Electric stove and oven, freezer and microwave all the way. We have a Conser 47 CAt that motored for 96 hours continuously and motor sailed from Florida to Maryland using the motors to increase speed and generate while sliding down waves. We also have a boat that uses wheel chair batteries and a 4kw generator which altogether is lighter than the comparable diesel engine

Cheers
Lock

 

[spark]

I have been researching this concept for the last couple of years and am currently constructing a 30' yacht that is designed specifically for an electric drive with regenerative charging. The intention is to build and demonstrate a prototype system with a view to developing a range of electric drive/power supply systems for yachts in the 25' - 50' range.

I looked into the Solomon Electric Wheel but was put off by the price and the bulk/weight of the motor. It is much more expensive than a diesel installation and the motor is much bulkier/heavier than other traction motors offering similar output. It also runs at 144V which is not very attractive.

As some of you have pointed out two of the key issues are range and recharging. The other is integrating the drive system into the rest of the boat's systems.

Finding out the drag of the boat at a range of speeds is crucial. A typical drag curve is very shallow up to around 75% of the 'hull' speed of the boat: thereafter it steepens very quickly. This means that the range for a given battery capacity varies enormously. e.g. cruising at 50% of hull speed in flat water might give you a 10 hour range while going at 100% of hull speed might only give you a 2 hour range. Understanding drag and deciding on how fast you want to go under motor and for how long is key to the design of your system.

A large diameter propeller is also essential for an efficient drive, and for regenerative charging. Even with a large prop our investigations suggest that a ratio of 6 hours sailing generating enough charge for 1 hour motoring might be realistic. We are considering various propeller options, the ideal being a folding or feathering propeller that can be opened when under sail in suitable conditions (i.e. when it's blowing a hooley and the extra drag is of little consequence).

Integrating the drive with the rest of the boat's systems is probably the most problematic issue on a retro fit. Most electrical systems on boats (even new ones) are a bit of a bodge and adding a 48V (or 60V, or 72V) drive system with various charging equipment is only going to add to the liklihood of trouble. We want to develop a fully-integrated power supply/management system that can be installed with the drive - one to which additional appliances can be easily added in the future.

We are on the hunt for funding to accelerate the development of the prototype system. If anyone out there is interested in becoming involved please get in touch.

Malcolm Henry - mh@qei.co.uk

 

[Bergman]

Don't really see the advantage of diesel-electric over just diesel, particularly if you are in a sailing boat. You just end up running the diesel for longer cos boat goes slower under power. If you use regenerative charging then boat goes slower under sail as well cos turbine or wheel or whatever acts as brake.

BTW

Thought you had left for foreign parts - hope you have not had any problems praps just waited to enjoy our glorious summer.

 

[Robin2]

This is a reply to a few of the recent posts.

The idea of needing to sail for 6 hours to develop 1 hour's worth of electric power is going in the right direction - but not nearly far enough. The towed water generators that are readily available develop very little power compared to, say, a 12kw electric motor. If you plan to "tow" a 2kw generator (i.e. your propellor) it will cause huge drag and slow a modest sized sailing boat enormously. It will be EXACTLY the same as running a 2kw (2.7hp) outboard motor in reverse while you are sailing.

Note that, when a propellor is stopped in the water (by putting the engine into gear) it is not generating any power so that is not a comparison.

On the other hand (to look for a positive note) it could make sense to have, say, a 12kw electric motor, a 6kw diesel generator and a large battery bank. For the odd occasion when you need the full 12kw it can be provided by the engine and battery working together. At other times the engine or the battery would probably provide sufficient power for the motor on their own. And the generator would be big enough to recharge the batter in a reasonable period of time. It may also be feasible to obtain a small amount of charge from using the electric motor (driven by the propellor) as a generator on long passages.

This sort of hybrid system makes sense for road vehicles because it allows the engine to used either at efficient high power output or not at all. In a car the 100hp engine probably seldom operates above 30hp.

I don't know, however, if the same logic applies to boats. With sailing boats their overall fuel consumption is small anyway and the stinkpots drive at full throttle everywhere!

Another thing to bear in mind (which may also knock the hybrid idea) is whether you want to motor or motor sail for long periods to make better time in poor weather - that will quickly deplete batteries.

Either the sails or the diesel should be considered as the auxiliary power - don't bother with auxiliary auxiliary power !!!

 

[spark]

There are conflicting opinions about whether a fixed or spinning propeller creates more drag so I cannot say for sure whether connecting a generator to the spinning propeller will increase the drag or not. In light winds the inertia of the generator will effectively lock the propeller. In strong winds the propeller will spin and the generator will produce a current.

What is certain is that towing a propeller, whether locked or spinning, will not be the same as running a 2.7hp outboard in reverse. The majority of sailing boats have fixed-bladed propellers and are dragging them around, locked or free-spinning, whenever they sail.

My guesstimate of 6 hours sailing to produce enough power for 1 hour motoring is based on the calculation that my boat (LOA 30'; LWL 24') will require approximately 1.15kW of power from the propeller to drive her at 5.6knots in flat water. Research suggests that 50% overall efficiency is realistic for an electric drive so for my 1 hour motoring at 5.6kn I will need to take 2.3kWh out of my batteries.

Assuming my charging equipment is at least 80% efficient I will need to generate 2.9kW over the 6 hour charging period. Generator efficiency of c.80% is realistic so the power that I need to get out of the propeller is c. 3.6kW or 0.6kW per hour over the 6 hour period.

The drag on my boat when under sail at 6.5 knots in a lumpy sea is approximately equivalent to 5.2kW. Even if ALL of the 0.6kW from turning the generator is additional to the locked or free-spinning prop drag (which it certainly won't be) it will only slow me down by c. half a knot, which does not seem to me to be an unacceptable price to pay for free and silent motoring for the last few miles into harbour. The stronger the wind and faster the speed of the boat the less the effect on boat speed of 0.6kW of drag. Belting along in a F6 and you won't even notice it.

The diesel electric hybrid system is ideal for sailing boats so long as you do not want to cruise at hull speed under motor. If you are content to cruise at c. 70% of hull speed then you can use a generator with a lower power rating (than an equivalent diesel drive) for continuous motoring. Short periods of full power (for getting out of trouble or getting to the pub before closing time) can be delivered by the batteries. In smaller yachts the hybrid system is less attractive because of capital outlay but in any yacht over 45' the cost of the hybrid system will similar to a conventional diesel auxiliary system and much cheaper if a genny is included in the conventional set-up.

Understanding the exponential nature of drag on a displacement hull is key to understanding the opportunities and limitations of electric drives.

 

[Robin2]

I don't want this to become a personal conflict. Nevertheless I must take issue with your comments.

We may, inpart be talking at cross purposes because of a difference of scale. If your boat only needs 1.15 kw to drive it I assume you only need a very small outboard engine. The ratios I was talking about still apply. The drag of your 0.6kw will be over half of the "negative drag" that your motor provides when it is pushing. If 1.15kw amounts to 5.6kt then 0.6kw must be equivalent to something like 2 kt of drag.

Any other way of looking at it amounts to perpetual motion - getting something for nothing.

It is not appropriate to compare activity in a lumpy sea with flat water. One of the problems with a natural generation system (wind or water) is that you cannot guarantee a supply. What happens if you motor out to sea and then find the wind has died and you battery is flat?

 

[spark]

Robin2,

Don't worry, I'm not taking it personally. Nothing wrong with debate and disagreement. There's always the chance that I might have missed something but...

The point that I haven't managed to make with sufficient clarity is:

The drag on my boat at 5.6 knots in flat water is c. 1.15kW

The drag on my boat at 6.5 knots in rough water/wind is c. 5.2kW

If I use the prop for regeneration when sailing at 6.5 knots the additional drag of 0.6kW represents less than 12% of the combined hull/rig drag at that speed.

If I choose to motor only in flat water then I will get c. 1 hour motoring for 6 hours sailing in a stiff breeze.

The ratios that you are using assume that drag is proportional to speed, which is not the case. All displacement hulls have an exponential drag curve (speed v. resistance) i.e. the faster you go the steeper the curve and the more power you need to go just a little bit faster.

Furthermore, the effect of wind/waves on a boat increase the drag considerably when compared to the same speed in flat water with the boat upright and steady.

I do agree that there is a problem with security of supply of power. This is why we are keen to develop a power management system that provides the skipper with realistic range estimates for any given set of conditions. An onboard generator is the obvious solution but for smaller boats, where the cost of a genny is prohibitive, I suspect most patterns of usage can be comfortably catered for by a combination of regen, shore power and solar/wind devices.

I admit that, at this stage, we are working from reports of others' experiences and theoretical calculations but the indications are favourable enough for us to invest in developing the prototype. Hopefully we'll be able to test the theory for real next season.

 

[Trevethan]

I think that's what the diesel genny is for ... Leastways that's how I'd use it... get power for free as much as possible, when when nneds must fire up the genny to charge the batteries to get me home.

As I understand it, the plus of any hydrid engine is that you run the hydrocarbon burning bit at a constant efficient speed - better for fuel economy and engine life. Admittedly on a boat engine loading doesn't change in the same way it does in a car, but still think it might be a good solution - especially to engine-shy folks like me. Plus I wouldn't have to have great pounding diesels running all the time I motored which would make swmbo a much better and happier person.

Also, unsure what happens if sailing at or close to hull speed in a nice strong breeze. If you fire up your prop turbine thingy in generator mode you lose for example a half a knot, if wind blows harder do you regain that half knot or just end up heeling more with no increase in speed?

Finally still unclear how a fixed prop is able to cause less drag than one spinning in generator mode. Shouldn't drag be same or less?..

Regards,

Nick

 

[Robin2]

Regarding your final sentence ...

Imagine you have a small 4-wheeled cart (like kids might have) with a substantial electric motor / generator geared to the rear axle.

Assume, first of all, that you have nothing connected to the electric terminals while you pull the cart. There will only be mimial resistance from the friction in the gears and the motor bearing.

Now assume you connect a small bulb to the terminals. As you pull the cart the bulb will light and the cart will be harder to pull due to the energy going into the bulb - OK, only a very little bit harder to pull, but harder nonetheless.

Now assume you connect a 1kw electric heater across the terminals and pull the cart. The likelihood is that the load will be so great that the wheels will skid rather than turn as you try to go fast.

At that stage you are not generating 1kw because the wheels are skidding. You would have to weigh down the cart enough to stop the wheels skidding and then you could pull the cart faster .... except .... that a person could not pull 1kw for very long.

The freewheeling propellor is like the motor with nothing attached.

If you use the propellor to generate a large load you will probably find it stalls like the skidding cart wheels.


A further factor ....
I guess that you would need a much larger propellor to act as a generator because it would run much more slowly than one driven by a motor. The basic inefficiency in propellors is because they must (?) rotate faster than the water to generate a push. As a generator, they will have to rotate slower than the water to be pushed around.

 

[Trevethan]

I understand the cart business But perhaps I didn't make clear that when sailing I make sure my prop won't spin, thus saving shaft wear etc, at least that was I was told best practice is. I don't have a folding prop!

I admit a freely spinning prop will produce less drag that one use to generate power. But as far as I can see both will produce less drag that one that is locked.

To use your analogy - locking the wheels makes the cart harder to pull than with the light bulb on it. Increase that electrical load as high as you like and as long as the wheels turn its still easier than pulling the locked wheels.

 

[Robin2]

I'm sorry but your final statement is definitely not true. You can try it in your car anytime you have a clear road - the maximum braking effort exists just before the wheels skid and the grip drops significantly immediately they do skid. This is the logic behind ABS brakes and explains why you must take your foot off the brake if you get into a skid in a car without ABS.

I am inclined to believe the drag is less when the propellor is allowed to revolve as, otherwise, it would prefer to be stationary. But the propellor turns very slowly compared with when it is driven by the engine.

Its great to have a controversial subject.