Oceanvolt Servoprop regen tested by UMA

[Tupaia]

Originally Posted by Adelie

The latest system they have uses a controllable pitch prop.

As I understand it the previous system used a folding prop which had to be switched from forward or reverse straight to regen. The continuous load on the pivot points kept the blades open. Sometimes they closed some and production dropped.

So regen works with fixed, folding or controllable pitch props but not with feathering.

From the pictures they appear to be using a Gori prop and making use of the overdrive setting.


A conventional folding prop cannot be held open when sailing forward.



Feathering props can be used for regen. If the engine is switched off while running in reverse the blades will not feather and remain locked "in reverse". I experimented with a shaft alternator using such a setup.

[Chili Palmer]

Originally Posted by Moontide

Couple of problems with this "test" in my mind.



I presume regeneration requires a fixed prop although the lead pic shows a feathering one. Not sure how a folding prop would generate anything since the purpose of them is to fold and reduce drag. That being said, to me the real issue would be the increase in drag caused by a fixed vs. folding or feathering prop. That is not insignificant.


Turning the regen feature on and off does not change the drag induced by a fixed prop.


Once a boat hits hull speed you have excess/unused "power" from the sails so the extra drag could not be measured. On a boat the size of Uma at 6.5 kts plus they are probably at hull speed so they are not using the "excess" power of the sails. On that size boat a more realistic test might be trying it at 4 to 5 knots, or even slower.



This would imply that when there is enough wind to go hull speed there very likely is no loss of speed when regenerating.

You should probably watch the video before commenting.

[Adelie]

Originally Posted by Tupaia

From the pictures they appear to be using a Gori prop and making use of the overdrive setting.


A conventional folding prop cannot be held open when sailing forward.



Feathering props can be used for regen. If the engine is switched off while running in reverse the blades will not feather and remain locked "in reverse". I experimented with a shaft alternator using such a setup.

Cool, didn't know about that trick. Thanks.

The advantage that CP props have is that the optimum pitch for regen is significantly different than for propulsion so it get get close to both of those without sacrificing significantly for the other.

[wingssail]

Originally Posted by Tupaia

...A conventional folding prop cannot be held open when sailing forward...

My Martec folder will stay open and spin if I am sailing and the transmission is put into neutral. I have to put it into gear briefly to get it to fold. It will not open after that until the engine is started and put into gear.

I doubt if it could be used to generate much power.

[danstanford]

My Oceanvolt powered boat has a regen system and a folding prop which came with it so there must be some way it works. Sadly I don't know how as I have never used the regen function.

[malbert73]

Originally Posted by wingssail

My Martec folder will stay open and spin if I am sailing and the transmission is put into neutral. I have to put it into gear briefly to get it to fold. It will not open after that until the engine is started and put into gear.



I doubt if it could be used to generate much power.

Same with my flexofold

[BigBeakie]

Flexofolds work just fine with regen on either the OV SD15 or AXC series of motors. The 2 brands of props recommended by Oceavolt for regen are the Gori and Flexofold.

[chris14679]

There's a lightly used OceanVolt SD10 for sale at http://electricboat.co.nz for a fraction of the new price if anyone wants to try one for real?

It was in a 40ft trimaran but when the boat was sold the new owner had a different ideology and didn't want it.

It's located in NZ but can be shipped anywhere in the world. Price only 9950 USD plus shipping.

The lithium battery bank is also available but that can't be shipped outside NZ.

[mglonnro]

Originally Posted by danstanford

My Oceanvolt powered boat has a regen system and a folding prop which came with it so there must be some way it works. Sadly I don't know how as I have never used the regen function.

From OV:

With a normal folding propeller the motor kicks the blades out and centrifugal force combined with the motor controller keep the blades open. The motor controllers tune the system actively at 10 Hz which prevents the blades from closing (too much braking would close the propellers). This is continuous monitoring, the system will adjust the propeller RPM depending on the boat speed.

https://oceanvolt.com/solutions/hydro-generator/

Some kind of magic

[seandepagnier]

Originally Posted by Adelie

Cool, didn't know about that trick. Thanks.

The advantage that CP props have is that the optimum pitch for regen is significantly different than for propulsion so it get get close to both of those without sacrificing significantly for the other.

Please understand that they are still not optimal for regen. It is physically impossible even with variable pitch.

A purpose hydro generator will always produce more power for the same drag than this servo prop is ever capable of, because it is impossible to do without twisting the other way, and the twist on the blades is fixed, only the blade itself rotates which is not enough. It would have to rotate and twist as well.

It is a significant sacrifice to do the way they do in this video and the production some fraction (approx 40-60%) of what is possible to do for the same drag otherwise.

[Dirk01]

There are many doubts about a "double heat exchanger". I'd like to make it a little bit more clear.
You need two, hydraulicly seperated, heat exchanger for the hot water tank, if you use two different heat sources (with often two different "cooling fluids"). In my case the fluid is heated by heat tubes OR a genset.
Side note: Evacuated heat tubes are much more efficient and can produce heat even in temperatures below minus degrees.
The "double heat exchanger" is normally located in the tank. Like at home, if you have a natural gas or oil based heater and a solar based one on the roof at the same time for the same tank.
The natural gas or oil based heater normally uses water for heat transportation and the solar based sole.

Sorry for my late explanation. I hope that's now clear.

Cheers
Dirk

[seandepagnier]

Originally Posted by Adelie

The optimum prop is the largest diameter Controllable Pitch Prop that will fit on your boat and that will fully feather. ServoProp qualifies but has very low production volumes hence the $40k price tag.

Almost. The diameter needs to be at least half the beam of the vessel for a monohull to achieve the 90% efficiency generally. The prop they are using is I estimate 1/6th the diameter it really should be and therefore below 30% efficiency and really should not be a consideration. It is a poor match, but maybe ok for them if they use it infrequently. It really should be a generating turbine though, not a propeller in that case as it is simply way too small to be efficient at propulsion.

The optimum propulsion prop can never be optimum for generation and vice versa. Variable pitch optimizes things somewhat but is not a substitute for being able to vary the camber and twist. So if it were fully flexible then sure.. and fish and dolphins already have higher efficiency, as tails are also a bit better than propellers but without room-temperature superconductors there is no way we can build mechanical ones.

[Dirk01]

Originally Posted by Pete7

Dirk, that would make ice for me

Jim, something like this:

https://www.alternative-energy-tutor...collector.html

Seem to remember doing a calculation and I would need 2sqM just to heat the hot water, more to heat the boat. Oh and not light either.

Pete

I didn't mean that this is a one fits all solution. So, if you need to heat the boat itself (especially an non-insulated one like UMA) that is surely not fitting best.

It's just a thought about possibilities.

Thank you for the link and your explanation about double heat exchanger. You cut the gordian knot...

Cheers
Dirk

[ve0hak]

Originally Posted by NaClyDog

Something isn't adding up... the OV site states the following;

How is roughly $40K 20-25% more than the cost of a traditional system??? How on earth do you get a ROI in 2-3 years?

I could believe that the cost of the engine and mechanical linkage is something comparable to the cost of an engine that burns dinosaurs, maybe a bit more expensive, maybe not.

The batteries are another story. Depending on the size of boat (power) and capacity (range) desired, I could easily see the battery bank costing a few tens of thousands. Especially if buying as a polished system with branded parts. As usual, the whole thing is possible much more cheaply with much greater effort by sourcing components individually.

[JC Reefer]

The times in which regen can be taken advantage of is limited. For me this is limited to the point of useless.

Saying that, it’s going to be an option of with any brand that is marketing for marine electric motors. Might even be standard.

I’d consider going fully electric (if money were no object) but would not be interested in regen.