The future of batteries, solar, and electric motors....

[GTom]

Depends how much you want to throw at your boat. On a cat, even a 2kWp solar (20 m2) and 2x1kW windmills are possible. Not saying economical or quiet (listening the wind generators in stereo...), neither that it provides full electric propulsion, but provided unlimited funds feasible, and might get you out of some awkward situations.

Personally I am with you, I don't think serious electric propulsion becomes a viable solution before we see those 90% efficient (500Wp/m2) solar panels and the energy density of the batteries doesn't go up 4-5x.

Btw, the Watt&Sea gear with 280mm propellers produces 400+W each at 8kts:


I fetched my fuel consumption guess from here:

While not a 380, we have a 450 with folding props, and inlight to medium sea conditions running on one engine is definitely more efficient than two. We'll do this all the time when we can't get the wind tomove us. For us it's not a matter ofresale value but a matter of efficiency. All things being equal, at 1500RPM o na single engine the Yanmar consumes 1.9L/hr and speed along a approx4.8-5.0kts. With two engines at 1500RPM its 6.3-6.6kts and twice the fuel burn.That's 100% more fuel burn for a third of gain in speed. It also corresponds to a reduction in overall engine hours thus wear and maintenance. Most cat owners I know motor in way. I'm sure you'd find your 380 will do the same but the fixed prop I expect would affect your efficiency. Steve. 450

[OceanPlanet]

If you had an electric system with decent regen (Oceanvolt, Electric Yacht, eventually Torqeedo), you won't bother with the Watt & Sea hydro. You could get much more regen from the main system. Even with folding props.

[GTom]

Originally Posted by OceanPlanet

If you had an electric system with decent regen (Oceanvolt, Electric Yacht, eventually Torqeedo), you won't bother with the Watt & Sea hydro. You could get much more regen from the main system. Even with folding props.

The Oceanvolt hydrogenerator doesn't seem to be any more efficient to me than the Watt&Sea. At the realistic max 6-7kts (for a 40' mono) it yields ~250W. Of course, if someone hooks it behind a racing trimaran, that's a completely different story - I won't...

[OceanPlanet]

Originally Posted by GTom

The Oceanvolt hydrogenerator doesn't seem to be any more efficient to me than the Watt&Sea. At the realistic max 6-7kts (for a 40' mono) it yields ~250W. Of course, if someone hooks it behind a racing trimaran, that's a completely different story - I won't...

That backs up what I've been saying for a long time...electric propulsion makes the most sense on light & fast boats. Less motoring overall, better motor-sailing (extending range), and much more regen when sailing. I've seen videos of Oceanvolt regenerating at 5kW...at 20kts...;-) Electric Yacht does powerful regen as well.

[GTom]

Originally Posted by OceanPlanet

That backs up what I've been saying for a long time...electric propulsion makes the most sense on light & fast boats. Less motoring overall, better motor-sailing (extending range), and much more regen when sailing. I've seen videos of Oceanvolt regenerating at 5kW...at 20kts...;-) Electric Yacht does powerful regen as well.

Absolutely right! Racing tri's rule then

[Paul Elliott]

Originally Posted by OceanPlanet

That backs up what I've been saying for a long time...electric propulsion makes the most sense on light & fast boats. Less motoring overall, better motor-sailing (extending range), and much more regen when sailing. I've seen videos of Oceanvolt regenerating at 5kW...at 20kts...;-) Electric Yacht does powerful regen as well.

I've heard that the hydrogenerator props have a different shape than the propulsion props. Do you think that the prop shape optimizations aren't that critical after all is said and done?

[OceanPlanet]

Originally Posted by Paul Elliott

I've heard that the hydrogenerator props have a different shape than the propulsion props. Do you think that the prop shape optimizations aren't that critical after all is said and done?

For sure a dedicated prop config (flipped backwards) would be more efficient for regen/charging, and this is the Watt & Sea config. However, when you see the regen numbers that Oceanvolt and EY are getting, even with folding props, obviously they work fine. Apparently the centrifugal force holding the prop open is plenty to provide the regen (or they wouldn't work in reverse!)

[newhaul]

Originally Posted by OceanPlanet

For sure a dedicated prop config (flipped backwards) would be more efficient for regen/charging, and this is the Watt & Sea config. However, when you see the regen numbers that Oceanvolt and EY are getting, even with folding props, obviously they work fine. Apparently the centrifugal force holding the prop open is plenty to provide the regen (or they wouldn't work in reverse!)

Just a minor observation here why would you ( if you are using the primary propulsion prop and shaft for regen) would you even want a folding prop. Seems to me to be just unnecessary money spent and at least 2 points of failure that can be avoided.

[OceanPlanet]

Originally Posted by newhaul

Just a minor observation here why would you ( if you are using the primary propulsion prop and shaft for regen) would you even want a folding prop. Seems to me to be just unnecessary money spent and at least 2 points of failure that can be avoided.

Excellent question! However a lot of boats that would go with these systems would be raced now & then. When spinning the prop wouldn't be allowed.

[newhaul]

Originally Posted by OceanPlanet

Excellent question! However a lot of boats that would go with these systems would be raced now & then. When spinning the prop wouldn't be allowed.

Transmission in neutral or a simple shaft brake would stop that issue . now explain when and why they wouldn't allow the prop to spin for power generation. ( I do fully understand the reason for not allowing it for propulsion) what would be the difference between them and my Spencer? (IT has diesel and a fixed prop and was designed for offshore racing. ). Locked shaft is locked shaft.

[OceanPlanet]

Originally Posted by newhaul

Transmission in neutral or a simple shaft brake would stop that issue . now explain when and why they wouldn't allow the prop to spin for power generation. ( I do fully understand the reason for not allowing it for propulsion) what would be the difference between them and my Spencer? (IT has diesel and a fixed prop and was designed for offshore racing. ). Locked shaft is locked shaft.

You have it exactly. However, why would you want to race with a non-folding prop? Anyhow, to begin regen you need to start it spinning with the electric. Which may not be an issue if that is agreed to beforehand with any particular race org. For instance for the Vendee, Conrad had all the motor data logged, so was able to start his up for regen and they could look at the files to know he didn't use it for propulsion.

[Adelie]

Originally Posted by Paul Elliott

True, but with a cruise ship the use case is substantially different. There are tremendous house loads, compared proportionally to a typical private boat. Also, I understand that in the big ships there are multiple generators that are fired up or shut down as the demand requires. This way they can avoid the inefficiencies that exist when you have a single generator sized for your maximum load, but you spend a lot of time running it lightly loaded. I also don't believe that cruise ships have a significant battery bank. These are all important factors.



I love new technology and I would be thrilled to see some breakthroughs in energy generation and storage that could be appropriately applied to small boats. My problem may be that I'm an engineer. I need to do the math. So far, I've been disappointed.

Another reason the cruise ships go for electrical propulsion is the desire to self-dock without tugs. They go to a lot of out of the way places and schedules change periodically as destination preferences/fads change. Tug services may not be available at a new destination. Tug services also present scheduling issues. If a tug is late for a docking there are going to be several thousand annoyed passengers which does not translate into repeat customers.

With an electric based propulsion system cruise ships can use Azipods for main propulsion which in conjugation with bow thrusters allow even the largest cruise ships to dock without tug assistance.

[NCGunDude]

I've been following this thread, and made at least one comment. There's no question diesel in the hands down winner in stored energy per mass, and AGM batteries for durability.

That said, in terms of cleanliness, storage, and maintenance, I still have to go with propane for cooking, heating, and genset fuel, and then an electric propulsion drive. Maybe a small outboard for auxilary power, which doubles as a dingy drive.

The boat? An older trimaran, yet to be sourced. The sailing location is US East Coast.

The advantages of propane are it's shelf life, which is indefinite, 20 year tank life, portable, something a two wheel dolly or golf cart can move, and easily stored. Can be used for heat, cooking, and running a genset. Probably even running a refrigeration unit and A/C, although 12V refrigeration may work.

House loads aren't an issue on a small boat. The main issue is the propulsion. Would a solar regen, generator supplemented battery powered propulsion system with auxiliary outboard be sufficient for following the seasons, and would an all propane onboard system work for fuel? 40# tanks are manageable, and I can't imagine the volume/weight compared to diesel are too outlandish.

I could do the math, but I'm not an engineer, so even if I did, the numbers would be wrong. There's a reason I switched majors in college.

How about it, is the trade off feasible, or even possible??

[john61ct]

Propane on a boat

Better be 100% meticulous about the install, choose ABYC or UK standards as a starting point, surveyors with lpg experience

and most importantly ongoing checklist inspections, testing, proactive replacement etc

Boom bad

[NCGunDude]

Hmm, had not considered safety factors. Yes, boom and sink would be much worse than just sinking.