Replace Diesel with electric engine

[Adelie]

Originally Posted by wingssail

Dirk1, I said that regen is a fraud because it is sold as a way to recharge batteries by sailing, mostly by people trying to convince others that the EV proposal is better than it actually is.



But the bottom line is irrefutable: If it takes 7.5kw (10HP) at the propeller to drive a boat forward, turning that propeller while sailing to extract power will take at least 10hp also (more with the prop losses).

And that 10HP is in addition to the 10HP it needs to get out of the sails to move the boat at 5-6 knots. Few boats have that much excess power available from the sails.

Another way of looking at it is: If it takes 10 hp to move your boat, where is the extra 10HP to spin the prop in regen mode coming from?

The obvious answer is two fold:

1. The drag of extracting power by spinning the propeller slows the boat.
2. Even the most modern hydro generators, such as Watt&Sea, produce very modest outputs. The company claims that "the cruising model will recharge a 200-amp, 12-volt battery to 50 percent of its capacity after 10 hours with a 5-knot boat speed" This is about 120watts. and it still knocks up to 1/2 knot off of the boat speed (point 1). https://www.google.com/search?q=how+...hrome&ie=UTF-8

Buyers want to believe the electric boat motor story, and they willingly believe that regen is going to do something for them, generally it is a lot of optimism which I doubt actually pans out and the sellers know that.

That's why I call it a fraud.

when a boat is near hull speed, the power demand for each additional knot or 1/10 knot increases dramatically. That's where regen shines, if you are cruising are you really going to be upset at loosing 1/10 or 2/10 kt in exchange for 500-1,000W. Probably not.

But most boats don't spend all that much time near hull speed. So regen potential is modest at best. Also regen uses the main prop which is designed for putting energy into the water not taking it out, so there are huge efficiency losses. If you can get regen at a marginal extra cost for an EP system you were going to buy anyway, it's probably worth the money. Buying a stand-alone system like Watt&Sea probably isn't worth $8k unless you are racing around the world and money is a minor impediment.

I want an EP system but wouldn't get regen because I would be using a folding prop to maximize sailing potential.

If there were a hydro-generator system producing about 100W at 4.5kt for about $1k I would probably get that.

For the boat I want 3.2kW should get me to 4.5kt. 5.1kW will get me to 5kt.
Let's say the hydro-gen is 20% efficient and there is enough wind to get to 5kt. The hydro-gen is producing 100W, that means it is sucking 500W out of the water which would result in a boat speed loss of 0.1-0.2kt. I'd accept that.

Using regen from the main prop with a 10% efficiency the loss would be about 0.3kt. Problem is that with regen somewhere in the 2-3kt range production drops to nothing but drag from the fixed prop is becoming very significant.

Maybe sales folks are being misleading about the costs and benefits of regen, and in that sense I could see the argument that it is a fraud, but in term of folks that go into it with eyes wide open, it's not a fraud.

[Adelie]

Originally Posted by double u

"...Your bowthruster analogy has merit though. 6kW to move the boat sideways at 2kt vs 7.5kw to move it forward at 6kt sounds about right. Good comparison....."
VERY doubtful the bt will "move the boat sideways" at 2kts! It will TURN the boat & in doing this might move the tip of the boat at 2kn...
I find this insistence on the feasybility of EP absolutely hilarious. Go to any crossroad of circumnavigators & count the boats with EP! Jimmy Cornell failed - but youall surely will outdo him! He's been out there (where few of you have gone) & back, multiple times & had sizeable funds to let the pros do it-& it didn't work. But surely youall...will (nice turn of Kraut-phrase "show him where Bartl fetches the cider!" I am thrilled waiting for it to happen!

I made the quip about the bow thruster pushing to boat sideways at 2kt as a mockery of the member who brought them up in the first place, bow thruster power demands are very much a apples to oranges comparison.

Jimmy Cornell did not do his own math, and did not communicate his actual demands to the supplier which is why he failed. Just because one big name failed using the idea, does not mean that the idea will not work. Actually you are conflating regen with EP. The regen did not work to Cornell's needs for various reasons, but that does not mean that EP failed, just the regen part which was enough to kill the whole project.

There is at least one member here who used EP while circumnavigating, actually he mostly was engineless, Boat-Alexandra.

[moseriw]

Ah yes I confess I WAS WRONG

drawing it on a chart with 40° leeway and constant wind direction (which never happens)
is: 12 NM to go upwind, 3 tacks, 15,5 NM in total.

OK fact at the adriatic is that I usually gave up as it was far too cumbersome as the true wind always turned in the wrong direction. And no my apparent wind speed was not that much, talking about 3-4 knots of speed and 10-12 knots true wind.

Therefore I try to avoid at wherever I can. OK only with one boat, the Salona it was cool. Was on the tack with the genoa only and did 12 knots. But the truth is: our bluewater cruisers are not built for this and if they are it becomes dangereous when gale forces goes beyond 60 knots due to the wrong hull construction. Speed is not essential, safety is.

Yes my current area is the adriatic but I did around 10.000 at the Med and Atlantic too so I think I do have a clue of it.

[seandepagnier]

Originally Posted by Na Mara

if you are frugal with diesel, it won’t be diesel that forces you into harbour. Take my boat as an example. Between my heater, genset and engine, my average consumption is 15l a week.

15 * 52 * 2.63 = 2051

So this is more than 2 tons of co2 a year. But if you consider the energy to extract, refine and transport it, the figure is roughly double this. Just this consumption alone puts you above world average. Imagine if you had this amount of emissions than this for all of your activities combined both direct and indirect, then consider half the world would still consume less.

15l a week is not at all frugal, by statistics it is excessive. try 15l or less each year

[seandepagnier]

Originally Posted by wingssail

Dirk1, I said that regen is a fraud because...

200-amp, 12-volt battery to 50 percent of its capacity after 10 hours with a 5-knot boat speed" This is about 120watts. and it still knocks up to 1/2 knot off of

You made the part up about 1/2 knot of boat speed lost. It depends completely on the boat, but generally is insignificant, maybe 1/8th knot or less.

According to their data the 600 model outputs 600 watts at only 8 knots of boat speed. I know a lot of people average speeds faster than this on passages. You can also put 2 or 3 of these on your boat, or use something larger than the small 240mm turbine it has.

The "fraud" if any is people spreading incorrect information about regen.

Lets admit that sailing is also a scam because airplanes are faster. Also nuclear powered boats have superior range making all other propulsion a "fraud"

[moseriw]

seandepagnier


yes and if someone runs mad an hysterical about food cunsumption you will refuse to eat.
But: whooahee not your pets because their food consumtions CO2 foodprint is only 1/3 of the whole food productions CO2 output.


I think nature shall blast us off this planet and yes everyone shall do everything possible to minimize his footprint. And it is easy!

Do not buy new things. Repair the old ones. Do not throw away what you have, repair it.
Urge the governements to only approve goods that are usable for 25 years and more.
Do not throw away your old working diesels. The footprint for something new exceeds every reasonable parameters.

If we do not buy new things our masters can not have revenues of 5000% any more and the harm to nature will decrease at lewast 90% I say it again NINETY PERCENT!

Yes and the known economy will die as everything that is not in the path of health evolution.

[Na Mara]

Originally Posted by seandepagnier

15 * 52 * 2.63 = 2051

So this is more than 2 tons of co2 a year. But if you consider the energy to extract, refine and transport it, the figure is roughly double this. Just this consumption alone puts you above world average. Imagine if you had this amount of emissions than this for all of your activities combined both direct and indirect, then consider half the world would still consume less.

15l a week is not at all frugal, by statistics it is excessive. try 15l or less each year

I take your point and it is somewhat valid. The correction I would make is that we have crew of 3-4 when cruising so the per capita emissions are more like 500-700kg from diesel. Add to this the emissions from the shore power used, the LPG for cooking, the emissions from the food we eat and all the embodied emissions in the equipment we buy maintaining the boat and we are probably around 2000kg per person per year living aboard.

So the diesel is just a small part of the overall emissions and those are about half what we emit on land. I am looking at putting on solar and maybe a bit of wind or hydro, but I don’t kid myself that it will make a huge difference.

I would also point out that the embodied emissions in an all electric system for my boat are around 4-6 tons of CO2. Add to the the emissions involved in recycling my old engine and sundry coupled systems and it would take maybe 5 years or so of full time cruising before the emissions saved from not burning diesel and propane offset the embodied emissions of the new system. Also recall that the largest part of the embodied emissions of an all electric system is the battery bank and that this needs replacing roughly every 10 years or so.

Maybe if you are permanently living aboard it might make ecological sense to ditch diesel for an all electric system based on renewable generation. In any other usage scenario, the emissions from switching over and intermittently changing the batteries won’t be offset by the diesel and propane being saved.

[zloitapok]

why we discussing footprint at this thread?
It is propulsion, diesel/electric thread.
How much "green" is electric - very complex question, we can't be sure on this point.
Lithium battery utilization - is good question, we don't know details.
We know diesel very well, at other hand we know electric propulsion a little. Need more time and data. This discussion is very similar to holywar )

[Adelie]

Originally Posted by zloitapok

….
This discussion is very similar to holywar )

A number of topics here are like that, some members feel that everybody should believe as they do, and those that don’t are stupid or intentionally obstinate: anchors, guns on boats, monohulls/multihulls, ….

[Na Mara]

Propulsion is just one aspect of a ships energy system. You can’t really bracket off propulsion from everything else and take that in isolation. A typical fossil fuel set up will give you propulsion, water heating, electrical charging, space heating, cooking and mobility for the dinghy. The main engine alone usually heats water and provides charging as well as propulsion. On some boats pumps and water makers are even directly run off the engine. As such the Diesel engine is integral to a boat’s energy system.

Similarly in a typical all electric installlation the motor will be for both propulsion and generation and the battery bank for the motor will usually serve double duty as the house bank.

Hence you have to consider these systems in the round to compare them against various criteria such as cost, emissions, safety, etc.

[wingssail]

Originally Posted by seandepagnier

You made the part up about 1/2 knot of boat speed lost. It depends completely on the boat, but generally is insignificant, maybe 1/8th knot or less.

According to their data the 600 model outputs 600 watts at only 8 knots of boat speed. I know a lot of people average speeds faster than this on passages. You can also put 2 or 3 of these on your boat, or use something larger than the small 240mm turbine it has.

The "fraud" if any is people spreading incorrect information about regen.

Lets admit that sailing is also a scam because airplanes are faster. Also nuclear powered boats have superior range making all other propulsion a "fraud"

Sean, the actual output curves for the WattandSea 600 cruising generator don't show much that output at speed that most cruisers can attain.

You say "600 watts at only 8 knots of speed". 8 knots is quite beyond the reach of most cruisers. I think 5 knot average is more typical, especially for the type and age of the boats that most people who are considering electric power conversions own. It takes a modern boat or a big one, and quite a fast shape at that, to regularly achieve 8 knots.

You will see if you look at the curves (below) that at 5 knots the WattandSea 600 produces 83 watts, about 7 amps. Not bad to supply house batteries but to recharge an electric motor's battery bank, for even one hour's operation at 6 knots motoring (estimate 10,000kwh) you would need more than 100 hours of sailing.

And most people who are converting to electric power from diesel are expecting to use their normal propeller and the electric motor in regen mode, not an expensive WattandSea unit. The power produced on those installations will be even less.

As for how much drag the regen adds, it is close to expecting perpetual motion to think that a propeller which absorbs 10,000 watts to push a boat at 6 knots won't absorb some energy and cause the boat to slow down when it is turning that same electric motor to produce power. Even WattandSea won't provide any guidance on this but they clearly know it exists. You can see that by seeing on the output curve chart how much faster the boats go when the size of the propeller is reduced from 280mm to 200mm.

Why would someone think that if you can go 2 knots on 740watts, that producing 600 watts in regen wouldn't take 2 knots off your speed?


And the sellers of electric boat systems gloss over these numbers when selling their products: "And you can use regen to put some power back into your battery when sailing". And the dreamy eyed buyer thinks, "Oh beautiful, it is even better than I thought."

Image: https://www.wattandsea.com/en/produc...o-cruising-600

[Adelie]

Originally Posted by wingssail

.....

You will see if you look at the curves (below) that at 5 knots the WattandSea 600 produces 83 watts, about 7 amps. Not bad to supply house batteries but to recharge an electric motor's battery bank, for even one hour's operation at 6 knots motoring (estimate 10,000kwh) you would need more than 100 hours of sailing.

That must be an awfully big boat to need a 13,404hp motor to go 6kt.
The boat I want would use about 6.7kW to go 6kt. In one hour it would use 6.7kWhr energy. If I'm only using 80% of battery capacity that means I need a 8.375kWhr battery. If I'm using LFP batteries that means I need 7,283Whr to recharge it. If lead acid then I'd need 7,614Whr.

7614Whr / 83W = 91.7hr to recharge.
But I would use the big rotor so at 5kt I would be getting about 120W. 7614Whr / 120W = 63.5hr.

That doesn't include house loads, but I would never count on hydro-gen for house loads, it's too intermittent. I would be running solar, and wind for house and traction loads, and using hydro-gen as a bonus for traction.

And most people who are converting to electric power from diesel are expecting to use their normal propeller and the electric motor in regen mode, not an expensive WattandSea unit. The power produced on those installations will be even less.

As for how much drag the regen adds, it is close to expecting perpetual motion to think that a propeller which absorbs 10,000 watts to push a boat at 6 knots won't absorb some energy and cause the boat to slow down when it is turning that same electric motor to produce power. Even WattandSea won't provide any guidance on this but they clearly know it exists. You can see that by seeing on the output curve chart how much faster the boats go when the size of the propeller is reduced from 280mm to 200mm.
Those curves show energy output for a given boat speed, they don't show boat speed loss for a given output.

Why would someone think that if you can go 2 knots on 740watts, that producing 600 watts in regen wouldn't take 2 knots off your speed?
Because they don't understand how the physics of the situation really works. The process while reversible, involves considerable entropy.
Let's do a thought experiment. Let's not generate electricity from the prop, let's lock it in place and drag it around. Let's use a 34' boat. Fixed props have more drag than spinning. What is the most that a fixed prop will cost in terms of boat speed. Maybe 0.5kt near 3kt. As the boat approaches hull speed the loss of speed caused by the fixed prop approaches 0.0kt.
Instead of a fixed prop, let's let it spin and extract energy from it. Even extracting energy from it, the prop is going to have less drag than a fixed prop.

If an unpowered prop in the water cost 2kt of boat speed for any sized boat, nobody would be using inboards, they would all be using outboards where to prop is removed from the water when the motor is not producing.


And the sellers of electric boat systems gloss over these numbers when selling their products: "And you can use regen to put some power back into your battery when sailing". And the dreamy eyed buyer thinks, "Oh beautiful, it is even better than I thought."

Image: https://www.wattandsea.com/en/produc...o-cruising-600

Yep, the sellers of of the hydro-generators do gloss over the reality.

[wingssail]

Originally Posted by Adelie

But I would use the big rotor so at 5kt I would be getting about 120W. 7614Whr / 120W = 63.5hr.

This is all thought games, do you really want to quibble about whether it is 64 hour or 100? In either case you've got to sail for days to get one more hour of motoring

Those curves show energy output for a given boat speed, they don't show boat speed loss for a given output.

Yes, but there has to be some relationship

What is the most that a fixed prop will cost in terms of boat speed. Maybe 0.5kt near 3kt. As the boat approaches hull speed the loss of speed caused by the fixed prop approaches 0.0kt.
Instead of a fixed prop, let's let it spin and extract energy from it. Even extracting energy from it, the prop is going to have less drag than a fixed prop.

Uh, I think where the model breaks down is that while motoring we get around something like 50% propeller slip, meaning the propeller thrusts a column of water back at twice the speed as the boat actually advances.

But while in regen mode the propeller spins only at the speed we are actually going (even much less).

To produce power equivalent to what we expend while motoring we'd need a prop with 1/2 the pitch, so at 6 knots of sailing it would spin twice as fast, and THAT would cause a hell of a lot of drag.

With what we have now, drag is very minor, yet so is regen.

To really get good power out of regen we'd need to add a lot of drag.

[Adelie]

Originally Posted by wingssail

Uh, I think where the model breaks down is that while motoring we get around something like 50% propeller slip, meaning the propeller thrusts a column of water back at twice the speed as the boat actually advances.

But while in regen mode the propeller spins only at the speed we are actually going (even much less).

To produce power equivalent to what we expend while motoring we'd need a prop with 1/2 the pitch, so at 6 knots of sailing it would spin twice as fast, and THAT would cause a hell of a lot of drag.

With what we have now, drag is very minor, yet so is regen.

To really get good power out of regen we'd need to add a lot of drag.

I agree that hydro-gen and especially regen has pretty mediocre performance.

You keep overstating how bad it really is. And you seem to be flirting with the idea that regen has poor performance and is not worth it so electric propulsion is not worth it either.

[wingssail]

Originally Posted by Adelie

I agree that hydro-gen and especially regen has pretty mediocre performance.

You keep overstating how bad it really is. And you seem to be flirting with the idea that regen has poor performance and is not worth it so electric propulsion is not worth it either.

No, I get it that they are separate. It's just that they are often linked together in the discussion.

As for electric propulsion itself, I think its fine, it's just that it doesn't fit the use case for a cruising boat. I'm as much a sail at all costs diehard as anyone yet even we need to motor far more than the current state of electric will permit. With electric power we'd have to entirely change how we use our boat. This spring and summer, as we usually do, Judy and I spent three months cruising in Mexico. We covered around 430 nm and around 33% of that was motoring. We simply could not have done that cruise without the ability to motor for 30 miles in a day if we needed to, then be able to do it again the next day. A monohull, hell even a cat, just can't get enough power from solar, wind, and regen, to recharge the batteries. Too many people seem to be blind to that.

And then there are the issues of battery technology which people seem to be blind to also. As marvelous as Lithium is for accepting charging, holding it, and providing useful power, the complexity of the electronic support equipment just is not recognized. Any of us who've been boating for a while know intuitively that everything electronic is subject to failure. We also know how damn hard it is sometimes to diagnose failures in the simple systems we already have. Yet to manage a big Lithium battery bank we happily install literally hundreds of additional essential circuits with little recognition of the inevitable headache which is bound to happen when they start breaking down. When our granddaughter comes to us and says, "Granpops, my phone won't charge up." You look and see that the system is down, and you're in Papua New Guinea. Where do you even start?

Heck look at the discussion going on right now on how to prevent a BMS shut down from spiking the alternator. People can't even agree on how to do that and that's just one little piece.

So I don't mind my toys being complex, but I want my important systems to be simple and for some god unknown reason I'd like other people to see that too.