EV powered boats?

[Singularity]

Originally Posted by jeff gedgaud

...My point being that a small generator other than the motors, solar panels, maybe even a wind turbine or two as well on deck and you've got a few ways to capture at least some energy...

There are many ways to capture energy and there are many ways to decrease energy consumption. Perhaps when you see people not using certain devices you wonder why they are not? Solar alone generally keeps your food cold and powers your LED lights (as can a towed generator underway). Wind turbines generally end up blocking solar and ultimately are not routinely producing the power that you might think.

Once you have enough solar to keep you food cold, run your lights and autopilot...things start getting academic unless you have particular electrical needs (hookah compressor, electric galley, etc). Probably the largest common excessive consumer of electricity is a watermaker; where people have a watermaker they often have a generator as well. Once you have a generator...running it once/twice a week alters you entire energy capture considerations such that maybe you forego extra solar or wind turbines.

Regarding banking for propulsion...I think a used $300 outboard, $5 gas can and $20 in gas will move most boats as far/well as the energy reserve in a large all-electric propulsion system. If I'm wrong make it two full gas cans. $350 vs $5-15,000 for an all-electric propulsion backup on a sailboat is not a deliberation many people spend much time on (not saying it's yours...but this is how I view folks who put all electrics in their previous direct-drive diesel sailboat).

[valhalla360]

Originally Posted by jeff gedgaud

I understand no free lunch, Wish more people did, My point being that a small generator other than the motors, solar panels, maybe even a wind turbine or two as well on deck and you've got a few ways to capture at least some energy. I'm not saying you could even come close to powering everything but you can at least slow the drain and make what you have last. That plus it seems to me, from watching videos that cruising is not for people in a rush to get somewhere but to enjoy the passage while getting to someplace interesting.

I mean this completely without sarcsim...no I don't think you understand...

Towed Water Generator:
- Let's say it takes 1000w of energy to pull the generating propeller thru the water at a certain speed.
- If it has pretty good efficiency, it might generate 700w of energy.
- The main propulsion prop (connected to the big diesel) needs to put out an extra 1000w of energy provided by burning more diesel fuel (proportional to an extra 1000w)..
- Net effect is you are burning an extra 300w for no gain.

Solar Panels: Technically it work but it doesn't do enough to have any significant impact.
- Let's say you have a 40' Catamaran with 1500w of solar panels. Cats can handle big solar arrays and are easier to push, so a monohul would typically be worse.
- You can typically expect around 4 times the rating in watt-hr...or about 6000w-h = 6kw-h. For reference teslas have around something on the order of 90kw-h of battery bank space....so you are looking at 15 days using no powerer to fill up a 90kw-h battery bank (realistically longer because the process isn't 100% efficient)

Now you have the consumption issue. The two power boats you mentioned would typically have a pair of V8's with something around 250 KW (300hp) engines...so lets say 500 KW total but at cruise speed they might be using 300 KW of power. If you took 3 Tesla battery packs at around $15k each and 1200lb each (a lot of weight), you would have less than 1 hour at cruise speed with a full battery bank.
- The 6kw-h the solar generates would add less than 1.25minutes at cruise speed per day.

Let's say you switched to a more efficient single engine trawler design which would normally have something on the order of a 100KW diesel and might run at 50% of max (ie: 50KW)...now you might get 6 hr range at cruise speed from a full bank but again, you are back to multiple weeks to recharge. The big solar array is adding back about 3.5minutes of run time per day of charging. (don't forget a 1500w array has a substantial cost to buy and build the structure to hold it).

You could just buy a big diesel generator. Run that to generate electricity and run that thru a bigger electric propulsion motor driving the prop but when you look at the weight of a large generator and electric motor you will find it heavier than a traditional diesel. Also converting the mechanical energy to electric and then back to mechanical works out to be less efficient than just running it thru a traditional transmission, so you lose fuel efficiency.

Where things can work out is with an efficient sailboat hull that requires low HP and you use it primarily to get in and out of harbor. 30-40 sailboats typically have 20-50hp motors but at 80% of hull speed may only run at 30-50% of peak output, so you might only need 10-15kw (depends on size, hull design and speed relative to hull speed). So if you only need a half hour to leave port and a half hour to get back into port, the 6kw-hr you can generate and store is a viable (if more expensive) option.

One other testy subject related to this is what happens if you get into a bad situation and need full power for a couple hours? If you size everything based on running at 50% of hull speed in calm windless conditions, you may quickly run out of juice fighting a 40kt headwind with steep 6ft waves. While it's hard on the long term longevity, you can typically firewall the throttle on a diesel for many hours based on the size of the diesel fuel tank if you get caught in a jam.

[jeff gedgaud]

"44'cruisingcat;2846414]The towed generator will consume more power than it produces. It's just physics.

Even if the towed generator was 100% efficient, (which it won't be) you'd still gain nothing.

Ie, if it was putting 500 Watts back into the battery, the loss in speed would cost you at least 500 Watts."

I'm not talking about towing anything, just plunk a small propeller down behind the boat from the steps, like a small wind turbine for the water, hydroelectric type like they use in rivers and such. I know drag is going to eat some but you should get back enough electricity to make it worth while.

[44'cruisingcat]

Originally Posted by jeff gedgaud

"44'cruisingcat;2846414]The towed generator will consume more power than it produces. It's just physics.

Even if the towed generator was 100% efficient, (which it won't be) you'd still gain nothing.

Ie, if it was putting 500 Watts back into the battery, the loss in speed would cost you at least 500 Watts."

I'm not talking about towing anything, just plunk a small propeller down behind the boat from the steps, like a small wind turbine for the water, hydroelectric type like they use in rivers and such. I know drag is going to eat some but you should get back enough electricity to make it worth while.

OK, not towing, dragging.

Same thing. If you're sailing, then yes, you can generate useful power, because you're not using power for propulsion.

If you're motoring using electric power, then dragging a prop to generate power will actually cost you more power than it generates.

A hypothetical example:

If you can motor at 5 kts using 5 kW, then you start generating power from another prop, the speed will drop. Say you generate 500 W, and the boat slows to 4.5 kts.

You're doing 4.5 kts, using 4.5 kW, right?

But if, instead of dragging the prop to generate 500W, you simply reduced power to the motor to 4.5kW, then you'd be going faster than 4.5 kts.

It really is just physics.

[Singularity]

Originally Posted by jeff gedgaud

I'm not talking about towing anything, just plunk a small propeller down behind the boat from the steps, like a small wind turbine for the water, hydroelectric type like they use in rivers and such. I know drag is going to eat some but you should get back enough electricity to make it worth while.

You're not understanding the vernacular/terminology used. When someone says towed water generator, towed generator...they are talking about something with a propeller that you stick into the water (as you suggest).
Indeed many people are willing to sacrifice a little bit of speed and a lot of money to drag such devices. Most people are not willing to pay $2-6,000+ for a device that they might use only on rare occasions and really never need, given the other resources on the boat.

See:
https://www.practical-sailor.com/blo...t-11090-1.html

You must appreciate that...most likely...any idea that you're coming up with regarding capturing/storing energy is already employed worldwide, just not on every boat. If you google around your ideas you should find all types of implementations of what you are thinking about. If you come up in a new one...a better mousetrap in the energy department...you'll be rich.

[Grith]

I have taken a different route to utilise ev power for my trailable yacht and dingy. My combined auxiliary and dingy engine is a 1003 torqeedo. With the combination of solar power and a 150 amp hour alternator on my diesel inboard I have the surplus power available to charge one of my two batteries whilst using the other to push my TS at 3-4knots suplimented by solar power. The torqeedo is used in wind conditions when travelling up river where winding directions mean the wind comes onto the nose precluding sailing for periods. It is also used for transiting under bridges and powerlines when the mast needs to be lowered. Finally I also use it for just moving in calm conditions when the noise of motoring is unwanted like bird watching or drift fishing.
It is then unshipped from the yacht and used for the dingy when required.
I decided as I needed a small dingy engine to also mount it on the yacht with the remote throttle kit available from torqeedo to perform these functions as well whilst saving the diesel for needed use on longer expeditions.

[Grith]

Oops my phone dropped out whilst posting.
The other reason for selecting the torqeedo was one less fuel source needed to be carried on board and the ability to recharge by solar on long expeditions away from refueling places.
My most recent week long trip with my daughter and her friend started badly when 15 minutes into motoring upstream in calm conditions on the Shoalhaven River the inboard diesel began to overheat. The seawater impeller had died from a fault in my understanding of the prior owners fitted flushing system. We could have abandoned the holiday to wait for the part or continue under sail and torqeedo outboard. As this was part of the shakedown and new equipment check process before major planned expeditions and with everything onboard for the holiday I decided to give it a go with only the torqeedo and sails. The entire week saw very little wind for sailing but the torqeedo allowed us to explore the whole river. I did decide to drop sailing out of the river and around by sea to Jervis Bay as planned as this involves a bit of a bar crossing for which I felt the inboard diesel was needed especially with someone else’s non sailing teenage daughter onboard. The torqeedo managed about 1.5 hours at half throttle and 4 knots per charged battery and at full throttle we got up to 5.5 knots but with only 35 minutes being indicated we didnt push it more than the short test. The combination of 2 lithium torqeedo batteries, 3 120 Amp AGMs and 4 solar panels totalling 480 watts got us through the week along with powering lighting, fans and small well insulated compresser fridge. An enjoyable trip if not achieving all the planned objectives we still had fun. Very weird No matter how I try to post the river shot the system turns it upside down?

[sguerrero1971]

Not an expert no experience with EV, but to help answer your questions I know of 2 boats that are currently using EV. They are sailinguma and Learning the Lines

These two might provide more practical answers to your questions.

Good luck,

[Adelie]

Originally Posted by jeff gedgaud

I'm a noob here and know nothing about boats or electric propulsion but have a question that I could not find but was wondering from the proponents of electric propulsion. Could you hang a generator off the back end of the boat and generate power regardless of type of propulsion at that time, i.e. wind or electric motors and gain back at least some power? I understand drag on the generator blades etc but it should not amount to much compared to being able to gain some power back even while motoring with the other motors/generators. Of course there will be a point where hanging bigger or more generators will add more drag than you get back but a small one that would at least add some back or at the very least not draw as much while motoring from battery banks does not seem to be discussed anywhere I could find.

The added electricity from a towed generator will always be less than the added load to the driving motor needed to overcome the drag of the generator. There will be a net loss by using the generator while motoring.

When under sail there will be a net addition to the battery at some cost in boat speed.

[GordMay]

A recent study [1], by the International Council on Clean Transportation [ICCT], showed that if you factor in all aspects of an electric vehicle [from manufacture to maintenance to fuelling], even an EV charging on a so-called ‘dirty’ [coal/gas fired] grid, still produces significantly fewer emissions, over its lifetime, than a gasoline-fuelled one.

“One of the biggest myths about EVs is busted in new study”
Even EVs that plug into dirty grids emit fewer greenhouse gases than gas-powered [ICE] cars.
Lifetime emissions, for an EV in Europe, are between 66 and 69 percent lower, compared to that of a gas-guzzling vehicle, the analysis found.
In the US, an EV produces between 60 to 68 percent fewer emissions.
In China, which uses more coal, an EV results in between 37 to 45 percent fewer emissions.
In India, it’s between 19 to 34 percent lower.
Actually building an EV is still a little more carbon-intensive, than building a traditional ICE vehicle. Recycling EV batteries could eventually bring that carbon intensity down. But for now, EV drivers start to reap the climate benefits after driving their car for a year or so, according to Bieker. That’s when the car passes the threshold, when the emissions that it saves by running on cleaner electricity, make it a better option for the climate, than a traditional car.
More about ➥ https://www.theverge.com/2021/7/21/2...cle-assessment

[1] “A global comparison of the life-cycle greenhouse gas emissions of combustion engine and electric passenger cars” ~ by Georg Bieker, for ICCT
➥ https://theicct.org/publication/a-gl...assenger-cars/

[yOyOeK1]

1985 Bruce Farr design, 40 foot, Australian build retired racing boat.
electric, no gas, working on switching to induction cooker. so no fosil fuels
sv oiysh haw a channel.
https://www.youtube.com/channel/UCpD...TfaVNzuUohUmxg

if you have questions ask I can help