Propellor for charging batteries using electric motor

[jimisbell]

Originally Posted by kevinjilliana

perhaps if you can solve the problem of perpetual motion you will be a hero in this new green world. Just stick to plugging into the marina power or use solar or wind to charge the batteries. Good luck with that.

Reading this entire thread I kept hearing a whisper in my ear, "Perpetual motion". It just isnt possible.

[Wireless1]

Originally Posted by u4ea32

I am extremely happy that I removed my diesel and all the associated parts, complication, and unreliability.

My electric motor (a 10kw air cooled motor, controller, throttle, motor mounts, etc. by ElectricYacht) is magical: so much easier to get in and out of the marina and raise or lower sails, or use the motor instantly, that it is a transformational experience. We use less than 5% of battery capacity on a given day sailing.

I want to also use the motor to charge the batteries underway.

What are people’s experiences?

My prop is old and poorly balanced Martec folding elliptical. It is creating the only vibration in the drive train, so I am going to replace it.

Any experience in other low-drag props and regeneration?

I chose a Kiwi 3 blade 16" prop with replaceable composite blades for my Freedom 32 based on most people's experiences that good regen requires at least a 16" prop and high sailing speeds -- AND the fact that the feathering Kiwi prop can lock in reverse for regen. Fortunately there was enough clearance for that prop. FYI, I got the Kiwi 3 blade 16" prop on Ebay for $600 and even at new prices the Kiwi is much less expensive than a classic Max Prop. Good luck...

[Wireless1]

Originally Posted by jimisbell

Reading this entire thread I kept hearing a whisper in my ear, "Perpetual motion". It just isnt possible.

Sure it is! You just get a big fan to blow on the sails and generate electricity for the fan by towing a prop generator!

[GrowleyMonster]

Originally Posted by Wireless1

Sure it is! You just get a big fan to blow on the sails and generate electricity for the fan by towing a prop generator!

Wile E. Coyote would love to compare notes with you!

[Wireless1]

Originally Posted by GrowleyMonster

Wile E. Coyote would love to compare notes with you!

Tell ol' Mr. Coyote that I use the ACME fan and towing generator kit.

[wingssail]

Query to EWOL:

Originally Posted by wingssail

Dear EWOL, I am not doubting you, but I'd like to see the numbers.

On a typical 45' medium weight cruising yacht, what size electric motor and battery bank would be needed to provide four hours of motoring at 75% of hull speed?

For four hour's motor operation at 75% hull speed, how much power is consumed?

What is the contribution, in terms of watts and time, of each power source required to supply that motoring energy?

What wind speed assumptions?

OK, Ewol has not answered me yet, maybe he still will. In the meantime let’s look at some numbers ourselves. These are my numbers, I am not an engineer and I would love to be corrected by somebody who knows what they are talking about.

A FEW NUMBERS RELATED TO ELECTRIC VS DIESEL FOR CRUISING YACHTS

Assume: 45’ cruising yacht with 36’wl. Hull speed = 7.8, 75% hull speed = 5.8kts

Electric:
Size electric motor to drive at 5.8 kts = 20kw
Power use at 5.8 kts = 16kw
4 hours of powering = 56kwh
Battery size LifePo4 = 4x300AH 48v (1200lbs, 18cu ft, approx $40,000) (check me here!)

Diesel:
Size diesel motor to drive at 7+ knots = 36hp (27kw)
Power use at 5.8 kts 20hp (16kw)
Fuel use per hour = .65 gal diesel
4 hours powering = 2.6 gallons (62kwh)
Fuel tank size = 2.6 gallons .5 cu ft

Solar:
1000w solar = 6kwh /day maximum
Six days to replace 4 hours of powering

Wind:
12 amps = 144 watts
16 days of wind to produce power for 4 hours of motoring

Regen:
256watts (22amps) optimistically, at 7kts speed, optimized, reduced speed due to drag not calculated.
9+ days of sailing to produce power for 4 hours of motoring

Conclusion:
Electric power is not suitable for even minimal use case on a cruising yacht. Yes, it works, but the cruiser will have to compromise considerably about travelling under power, either by speed or distance, generally both.

For day sailing, leaving and entering the marina, and short return trips under power, electric may be useful, but it will still be expensive.

None of this includes the discussion of the complexity of the installation or the safety issues of electricity around seawater and the use of Lithium Batteries.

The main advantages cited are silent operation, quick accessibility to torque and power, and lack of diesel smell and mess. Frankly none of these are persuasive to me; I love the sound of my diesel purring away, it will start instantly and provide torque as quickly as I need it, and I have only a minor gripe about diesel smell and mess while refueling.

Expense of a complete and safe system, with sufficient spares and back-ups, will be prohibitive compared to a simple diesel engine (what do you do when one of your BMS fails?)

Fossil fuels provide orders of magnitude more power per kg or cu ft than the best battery technology available today.

[skenn_ie]

Some water-speedometers use a turbine. Old-style ship's logs do too. You might get a big one, and use it for power generation. It won't cause drag unless it is actually charging the batteries, that, depending on how it is built, won't happen unless you are traveling quite fast. However, whichever way you look at it, the amount of regeneration will be irrelevant compared to the amount of power used for propulsion. The most it will do is keep your nav-lights going if you are sailing for days/weeks.

[GrowleyMonster]

Originally Posted by wingssail

Query to EWOL:



OK, Ewol has not answered me yet, maybe he still will. In the meantime let’s look at some numbers ourselves. These are my numbers, I am not an engineer and I would love to be corrected by somebody who knows what they are talking about.

A FEW NUMBERS RELATED TO ELECTRIC VS DIESEL FOR CRUISING YACHTS

Assume: 45’ cruising yacht with 36’wl. Hull speed = 7.8, 75% hull speed = 5.8kts

Electric:
Size electric motor to drive at 5.8 kts = 20kw
Power use at 5.8 kts = 16kw
4 hours of powering = 56kwh
Battery size LifePo4 = 4x300AH 48v (1200lbs, 18cu ft, approx $40,000) (check me here!)

Diesel:
Size diesel motor to drive at 7+ knots = 36hp (27kw)
Power use at 5.8 kts 20hp (16kw)
Fuel use per hour = .65 gal diesel
4 hours powering = 2.6 gallons (62kwh)
Fuel tank size = 2.6 gallons .5 cu ft

Solar:
1000w solar = 6kwh /day maximum
Six days to replace 4 hours of powering

Wind:
12 amps = 144 watts
16 days of wind to produce power for 4 hours of motoring

Regen:
256watts (22amps) optimistically, at 7kts speed, optimized, reduced speed due to drag not calculated.
9+ days of sailing to produce power for 4 hours of motoring

Conclusion:
Electric power is not suitable for even minimal use case on a cruising yacht. Yes, it works, but the cruiser will have to compromise considerably about travelling under power, either by speed or distance, generally both.

For day sailing, leaving and entering the marina, and short return trips under power, electric may be useful, but it will still be expensive.

None of this includes the discussion of the complexity of the installation or the safety issues of electricity around seawater and the use of Lithium Batteries.

The main advantages cited are silent operation, quick accessibility to torque and power, and lack of diesel smell and mess. Frankly none of these are persuasive to me; I love the sound of my diesel purring away, it will start instantly and provide torque as quickly as I need it, and I have only a minor gripe about diesel smell and mess while refueling.

Expense of a complete and safe system, with sufficient spares and back-ups, will be prohibitive compared to a simple diesel engine (what do you do when one of your BMS fails?)

Fossil fuels provide orders of magnitude more power per kg or cu ft than the best battery technology available today.

Your bias is showing. A simple EP system can be VERY cheap. Read my EP repower thread. I no longer remember what it cost me but it was in the neighborhood of $2200 all in, batteries, charger, controller, motor, reduction gearbox, cable, included. Lithium NOT needed. I used 8 golf cart batteries at $85/each for 48v at 220ah. Lithium would have been prohibitively expensive for me. Ryobi 2k portable gen added later, for a gitter home. Played with it but never actually needed it. For cruising I would have needed it of course but by that time I was already converting to pure motorboat and planning a solar canopy. And yes, it is much more practical for day sailing, or weekend/overnighting, so all or most charging can be from shore power. Even a turnkey system is still cheaper than a new diesel.



My latest boat has a 4-107 that seems to still be in perfect health. Since this boat will be used at some point for cruising, I will not be considering a repower unless the Westerbeast dies on me. I am lukewarm on EP for cruising unless the hull is designed specifically to hold lots of deep cycle batteries, along with a hybrid propulsion setup. Pure solar/electric is not for me. Series hybrid, where a generator charges and electric motor pushes, I don't care for, though it could have advantages for a workboat with high demands on maneuverability. Parallel hybrid, where you can run off the diesel OR the electric, with the diesel also charging batteries as needed, is considerably more worthy but again it would be more practical if the boat were designed from the keel up as a hybrid diesel/electric sailboat.



For a day sailer EP is not "maybe useful". It is very economical and practical, in either a newbuild or a forced repower. A basic EP system is NOT complex. Remove dead diesel or atomic 4. Build box for 8 golf cart batteries. Install them. Mount motor with reduction gear if needed. (usually is.) Align. Connect controller to motor. Connect batteries to controller. Install on/off switch and throttle control, connect to controller. Install meters if desired (recommended) and connect to controller. Install cheap hall effect sensor tachometer from ebay. Install charger, either 48v or a 4 bank isolated output 12v charger. Plug in to shore power. Charge batteries. Flip switch, turn knob. Go. I don't see it as being significantly more complex than replacing the diesel. For more simple, and less cash up front, buy a 6hp Tohatsu long shaft outboard. But EP for boats under 35' is not complicated nor is it expensive. And flooded batts are fine until you get down to dinghy size boats.

[skenn_ie]

I don't think the OP intended to cruise under electric power, rather use it to get in and out of a berth or anchorage.

[a64pilot]

Guys, I haven’t read the whole thread so maybe this has been brought up.
First don’t jump on EWOL. I’m sure he is correct he’s not telling stories, what everyone seems to forget is that we are talking about sailboats here.
Many, many people cruise the world without any engine, they aren’t motoring around the world with electric motors. They are sailing. Engines aren’t a necessity, they are a luxury.

The difference is those of us with Diesels if the wind doesn’t blow we crank our motors and still make progress, sometimes, the electric boats don’t, they wait until there is wind, from the right direction, then they go.

But if you have a lead acid bank, I don’t care how big the charge source is, your not fully recharging in two hours, lead acid banks don’t work that way, that’s a Lithium bank

[EWOL Props]

Hi WingsSail,

don't misunderstand me, I am not saying that everyone should move to full electric today, it is a fact that 99,9% of our props are installed on diesel engines today. But the switch to hybrid and full electric will gradually happen one day as it is already happening fast on cars...at least in Europe where the gasoline and diesel are much more expensive than in the US. Think about Tesla (US)....who would have said to get a range of up to 370 miles on a full electric car, I would have not....but the reality is different. Also I am not saying one should not recharge from the dock, it should be done if at all available.
Said that, look at the video done in 2015 about the Eco-Sailing Project, the one I mentioned in my earlier comments, where an old boat had been converted to 100% electric, they had 160 miles of range at low speed (about 5 knots if I well remember) and they have traveled the World with that boat. Other videos by Eco-Sailing Project are in YouTube, showing the complete trip they have performed....sorry it's all in French but I am sure you can anyway understand the concepts sketched.

https://www.youtube.com/watch?v=siiA5W6FoAU

[u4ea32]

Originally Posted by KTP

Thanks for the link and suggestion, will look them over.

I really don't see the need for a feathering prop with a electric propulsion system. If I don't need the regen and just need the fastest sailing speed, I can simply push the throttle forward more such that the controller starts sending a couple of amps to the motor and spins the prop. This should eliminate any drag effects? 2 amps on a 350AH bank isn't going to hurt much.

I had expected to do exactly as you imagine.

However, the spinning of the shaft and propellor does make noise. Nothing like a diesel of course, but still a lot more noise than the boat moving through the water.

Therefore, I do NOT want to motor being "barely driven" to eliminate drag while consuming very small amounts of power, because the noise, even though relatively quiet, does clearly interfere with the peacefulness of sailing.

Hence, the propellor must fold or feather for low drag while sailing, while also being able to generate power, and (really, to a lesser extent) also move the boat.

[u4ea32]

Originally Posted by wingssail

Well, you know, 11kw electric drive is roughly equal to 15 hp, barely marginal for a 40' boat in my opinion.

That 11kw is used each hour of operation.

Your Honda, driving an AC battery charger capable of charging at 50amps, which is 600watts, will have to run 18hrs to get one hour of motor operation.

Did I do the calculation incorrectly? Because, if not, it does not seem like electric power is very practical for cruising offshore or coastal.

Regen is even further from practicality, I see numbers like 40watt, 70watt, and some people imagine 200watts. Even if that were possible it means 55 hours of 200watt regen to get one hour of motor operation. 55 hours of high winds and all the while you are suffering from heavy drag and reduced speeds. By the way, these are much more pronounced on a light weight boat which has low drag in the first place.

Tell me how I'm wrong in this.

The fact is that at less than 5KW electrical power consumption, my boat goes the same speed as running the 3GM30F Yanmar flat out (claims 20.5KW on the name plate). That 5KW is more than adequate. I usually use less than 1KW, often less than 400W to move the boat at the desired speed.

There is no reason to equate diesel power to electric power. It seems like it should work that way in theory, but it clearly does not in practice.

I consume about 100watts to start sailing, and about 100watts at the end of the day. This is less than half the power used by the refrigeration over 24 hours. On a voyage, the propulsive power draw would of course be zero, just like the propulsive diesel use was. Its still a sailboat, still has infinite range.

So I don't need much power from regeneration, but the more the better of course, to minimize the amount of time I need to listen to the shaft and prop turning.

[u4ea32]

Originally Posted by wingssail

The question is not whether or not you can run a fridge on regen power, it is: Can regen provide power to run an electric propulsion motor?

The answer is clearly, it cannot.

If you wish to keep your fridge on, regen can be an answer. So can solar, (possibly wind).

But of you want to run your 20KW propulsion motor for 4 hours, you need much more than regen.

Why would you want to run a 20KW motor for more than 4 hours? It take 4 hours to get out of an anchorage or marina? I have a sailboat. It sails. It sails well. I go sailing. I love sailing. I spend all this time and money to go sailing.

The power used for propulsion is half as much as refrigeration on a typical day. So solar, wind, and regen should all work. Solar and wind is well documented to work well.

I'm looking for other people's experience using regeneration using the propulsion propellor.

[u4ea32]

Mine is a cruising sailboat. Not a racing sailboat. This means the performance is not being limited by silly racing rules. It sails at wind speed up to about 10 knots of breeze. It points, reaches, and runs well.

Daysailing requires more, not less powering than cruising. I have not once crossed an ocean on a sailboat where we used the engine for propulsion: four trans Pacifics, two trans Atlantics. I have not once sailed between islands using only power, in the last 60 years. It just has never happened in my experience. I can't imagine how it would.

So I just don't buy into the need for range under power. I need range to hoist, and then drop the sails, get in and out of a marina or in and out of an anchorage. That simply is hardly any at all. In practice, I am using half as much power per day for propulsion as for my top loading refrigerator.

The total installed cost of the electrical plant, including 5KW of LiFePO4 batteries, was about 80% of the wholesale cost of a Beta, at their factory, obviously not installed, ovsiously without all the life support systems (tank, hoses, filters, ...).

I could easily pick the electric motor up. I can adjust the motor mounts to align the motor with my fingers. The simplicity of the system is amazing.

The best thing is eliminating the horrible odor of diesel.

The second is the reliability: I can actually count on the motor instantly working at any moment.

The third best thing is the fundamentally reduced racket from the propulsion system. Now, I just hear the propellor turning in the water, and the shaft turning in the shaft log.

The fourth thing is the fundamentally reduced complexity of the entire boat. I am sure that more than half the parts on the entire boat were the diesel and its related stuff.

The fifth is the huge weight savings. The 3GM30F Yanmar, with all its life support, weighed about 750 lbs. The motor and batteries weigh 130 lbs: less than the fuel in the tank.

The sixth the the elimination of all the stuff that needs to be taken along for a diesel: filters, impellers, parts, coolant, oil, diapers, etc. An enormous amount of storage becomes available!

I have absolutely no regrets. I will never again own a sailboat with any kind of diesel engine aboard.