Propellor for charging batteries using electric motor

[u4ea32]

All good points, @Boat_Alexandra and @a64pilot. Thanks for those insights.

[a64pilot]

Originally Posted by boat_alexandra

It would be interesting and possible to design a propeller/repeller with neutral camber. This is what is used also by sculling oar blades.

I believe what your talking about is a fully symmetrical airfoil.
You’ll find that in I believe almost all feathering props, also they have no blade twist.
Both of those features make them less efficient for motoring, but would I believe make them better for dual purpose as in both propulsion and generating power.

[Shawn67]

Originally Posted by u4ea32

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.

If your propulsion power needs are that low (half refrigeration) I guess I wonder why bother with the expense of trying for more regen at all? I just converted my icebox to a fridge (without adding additional insulation) and over the past 11 days my average consumption is 264wh. The yield of my 100w panel averaged out to 315wh. The charging averaged 201 minutes of float time each day so it is keeping up. With 160 or 200w of solar you should be fine for your needs.

Shawn

[barryglewis]

Originally Posted by u4ea32

This is a claim by a vendor, backed up by video, that just does not make sense: I do not believe it. If I can find **independent** claims that this works, I will be intrigued.

I am not saying OceanVolt is lying or unscrupulous. But I don't think that when they eventually actually install one of these things in an actual real boat, that it will actually work like they claim. I can be wrong! I often am! But the forces at play don't allow that system to do what they suggest: drag folds folding props, and regeneration requires drag.

Just had a look, i think you might have misread their pitch (pun intended).
The propellor has different positions according to what the use is, so when feathered for sailing it is not also generating.
When set for generating it is not simultaneously feathered.
Similarly when driving or in reverse it is set for that purpose.
This looks very exciting to me.
I have and use a SailGen , but if i ever went to an electric motor i would certainly look very closely at the OceanVolt.

Barry
sv Risky Business

[wingssail]

Originally Posted by boat_alexandra

This is nonsense, because people who "travel under power" are already foolish. The engine is intended for harbors and tight areas, and even then it can be avoided.

For this use case, a trolling motor and a couple deep cycle batteries can be obtained free, but you can just sail. Propellors were never needed to go cruising.

Nuclear power provides orders of magnitude more power than fossil fuels, and we have the technology to make it possible to power small craft.

Fossel fuels should not be allowed if nuclear isn't, for the same reason. They both pose a significant danger.

Alexandra, you are voicing a point of view which is quite extreme. If that works for you (never use your engine to travel, use "free" trolling motor and two deep cycle batteries, and avoid use of motor even in tight places..) well that is great. But for virtually all cruisers I meet that does not work. They expect to be able to use their motors when the wind does not blow. Heck, they use their motors if the wind is ahead of the beam. Most boats don't have access to free motors and most boats would not go far with a trolling motor and two cells for power anyhow.
I think people with sailboats should sail them more, but for the purpose of this thread we should probably recognize the reality: cruising boats need the ability to motor when needed and right now electric power to do that is not., for most, practical.

[Adelie]

Originally Posted by wingssail

Alexandra, you are voicing a point of view which is quite extreme. If that works for you (never use your engine to travel, use "free" trolling motor and two deep cycle batteries, and avoid use of motor even in tight places..) well that is great. But for virtually all cruisers I meet that does not work. They expect to be able to use their motors when the wind does not blow. Heck, they use their motors if the wind is ahead of the beam. Most boats don't have access to free motors and most boats would not go far with a trolling motor and two cells for power anyhow.
I think people with sailboats should sail them more, but for the purpose of this thread we should probably recognize the reality: cruising boats need the ability to motor when needed and right now electric power to do that is not., for most, practical.

I think your response is extremely reactionary. You say it's his choice to make but call him "quite extreme" as if extreme isn't superlative enough and then you ladle on the sarcasm saying "well that is great."

Even paying retail, 2 batteries and a trolling motor are under $1,000 getting very good batteries (Trojan 150a-hr), a good motor (Minn Kota Riptide 45 or 55 lb thrust) and a replacement prop (Kipawa) with better efficiency.

With the above plus 4 solar panels and a solar controller (about $1,000) you have essentially unlimited range. Albeit most of that range will come during the day.

I admit that for weekenders and short term vacationers electric power isn't practical, people need to be home for work Monday morning or at the end of their time off.

But for cruisers electric power is practical, it just isn't convenient. With electric power sailing vessels can go hull speed for a couple hours in calm conditions. Going hull speed for a couple hours will get you thru just about any situation. By going half as fast they can go at least twice as far. However most want to go as fast as their existing expectations (hull speed) whenever they want for as long as they want (or at least for as long as their fuel holds out). It's not that it's impractical to use electrical propulsion, it's just that people don't want to make the compromises involved. That's THEIR choice to consider it too inconvenient for them, but that doesn't make it impractical.

For that matter you don't need any mechanical propulsion at all, there are enough folks cruising engine-less (including B_A) to prove that. It's not a choice I would make but if the situation were thrust upon me I could deal with it.

Change is coming whether we want it or not. It's not a question of if but when, and what the practical details will be.

[john61ct]

A few panels is going to give an "unlimited range" only for those willing to limit their motoring travel to a few miles a day.

I think the position was, that very few people would be willing to make the sort of "sacrifices" we know are required in order to make do with a no-FF electric setup.

Of course compared to zero motor at all, the electric setup is indeed an improvement.

But a set of oars may get you even further.

What makes electric propulsion practical in terms of **most modern boaters** is a big diesel genset.

But the advantages of such a hybrid setup are few, and there are plenty of con's.

[Adelie]

Originally Posted by john61ct

A few panels is going to give an "unlimited range" only for those willing to limit their motoring travel to a few miles a day.

I think the position was, that very few people would be willing to make the sort of "sacrifices" we know are required in order to make do with a no-FF electric setup.

Of course compared to zero motor at all, the electric setup is indeed an improvement.

But a set of oars may get you even further.

What makes electric propulsion practical in terms of **most modern boaters** is a big diesel genset.

But the advantages of such a hybrid setup are few, and there are plenty of con's.

The daily range is going to depend on the boat and willingness of the crew to set up and adjust the extra panels. Currently my boat makes 2.5kt using about 30 amps.

If I were to get 4-160W panels, an appropriate solar controller and a larger motor (let's say almost doubling my thrust) I could make 3.5-4.0kt. Given a 12hr day that's somewhere between 42 and 48 nm. I wouldn't call that a few miles. If I elected to use some battery power overnight I could gain another 9-15nm proceeding at about 1kt.

I get that most folks would not accept the compromises involved in going electric currently, but that doesn't mean it's not a practical choice for cruising, it's just so inconvenient that most people won't accept it. That's fine, its their choice. But to say it's not practical without discussing in what way precludes people from making an informed choice.

[john61ct]

Originally Posted by Adelie

Currently my boat makes 2.5kt using about 30 amps.

Must be a pretty light boat in ideal conditions, no opposing tide, current or winds.

OK, so sometimes more than a few miles, but not what most call an "unlimited range" with a heavier boat - more suited to actual cruising, loaded weights and in average conditions

And you do need to choose between motoring and replenishing the batteries.

Look, I don't want to come off as being "too negative", personally I'm **happy** sailing even full on Pardy style.

My main point is in line with yours, most owners aren't, at all.

[Adelie]

Light to moderate displacement, DLR of 149 in lightship condition.

Tides don’t oppose, only currents. If there was wind I would be sailing not motoring regardless of source of power for the motor.

Ideal? No, ideal would be wind and current from behind.

The speed given was for thru the water. When I tested this speed I did It near shore and did runs in both directions to average out any current. I did my testing with a moderate amount of gear onboard and the wiring left a lot to be desired. I have upgraded the wiring and am going to retest this summer or fall.

When folks discuss speed I generally understand that they mean thru the water not over the seabed unless they indicate otherwise.

Once the boat is fully set up the 4 panels for motoring will be in addition to regularly mounted panels to recharge the battery so there will be no choosing between motoring and recharging.

If you don’t want to come off as negative then stop being negative.

Stop trying to tell people it’s impractical because it’s not a choice most people would make, just say it’s a choice most people wouldn’t make.

I get there are serious compromises in performance if electric propulsion is chosen as the primary means of mechanical propulsion, I’m very wide-eyed about that and wouldn’t make that compromise myself.

But saying it’s impractical is tantamount to saying it’s not worth considering.

[StuM]

Originally Posted by Adelie

The daily range is going to depend on the boat and willingness of the crew to set up and adjust the extra panels. Currently my boat makes 2.5kt using about 30 amps.

If I were to get 4-160W panels, an appropriate solar controller and a larger motor (let's say almost doubling my thrust) I could make 3.5-4.0kt. Given a 12hr day that's somewhere between 42 and 48 nm. I wouldn't call that a few miles. If I elected to use some battery power overnight I could gain another 9-15nm proceeding at about 1kt.

You don't get full output from panels for 12 hours a day, even if you could keep them pointed directly at the sun al the time.


Assuming a nominal 12V system, 30A is abut 400 W. (much more if the voltage is higher). Double that is 800 W.


4 x 160W panels = 640W. Let's be generous and allow 5 hours "full sun equivalent" output per day (feasible in summer in good conditions)
That's 3200Wh/day.


At 400W, that gives you 8 hours motoring @ 2.5 Knts = 20NM.


Double the thrust means double the power requirement.

800W gives you 4 hours @ 3.5 - 4 kts from your 3200Wh.

That is only 14 - 16 NM.



Use that battery power overnight to get a few more miles and you have to use some of your solar the next day to replace what you have drained so your daytime distance would be less. TANSTAAFL.

[Marc1]

It is always a lot of fun reading through the threads that deal with batteries and solar of any description. It is like a group of priest from different religions get into a punch up for God.
"Diesel stench", ban fuel, and many more shouting from the marble towers of virtue signalling to the low life scumbags who use diesel, or dare I say 2 stroke (oh my!)

I say grow up and take a chill pill. If you think you are oh so virtuous for using electric motors, good for you.
Meantime in the real world, a lot of low life worms who craw on this earth use diesel to get around.

[Fore and Aft]

Thanks StuM for the maths and I assume those calculations are for healthy batteries and the maths only gets worse as the batteries get older?
Adelie I only think its a choice most people would'nt make until it finally works perfectly. Then I imagine most people will happily make the change. But we are still a long way from that and will we ever reach that stage? You are saying change is coming but just how far can batteries and recharge systems go? Sometimes things can only be improved so much, look at car tyres as an example. When is one set of tyres going to last the life of my car?

Cheers

[ranger58sb]

Originally Posted by Adelie

You say it's his choice to make but call him "quite extreme" as if extreme isn't superlative enough

FWIW... I think Boat Alexandra's position is "quite extreme" too. As I understand it, he thinks no one should ever use any fossil fuel for anything ever, and those who do are murderers.

He can correct me, if I've misunderstood... but of course in any case, he's entitled to his opinion. And it makes for interesting reactions here on the forum.

-Chris

[Adelie]

Originally Posted by StuM

You don't get full output from panels for 12 hours a day, even if you could keep them pointed directly at the sun all the time.
If there are 12hr of sun, by tracking you should be able to get full capacity almost from the time the sun comes up. I accept that for 15m or so at sunrise or sunset the insolation is attenuated by the extra atmospheric distance, but you will still be looking at over 11hr full output.

Assuming a nominal 12V system, 30A is abut 400 W. (much more if the voltage is higher). Double that is 800 W.


4 x 160W panels = 640W. Let's be generous and allow 5 hours "full sun equivalent" output per day (feasible in summer in good conditions)
That's 3200Wh/day.
You allow for tracking in your first paragraph then use "5 hours "full sun equivalent"" here which is flat/no tracking rule of thumb.

At 400W, that gives you 8 hours motoring @ 2.5 Knts = 20NM.


Double the thrust means double the power requirement.

800W gives you 4 hours @ 3.5 - 4 kts from your 3200Wh.

That is only 14 - 16 NM.



Use that battery power overnight to get a few more miles and you have to use some of your solar the next day to replace what you have drained so your daytime distance would be less. TANSTAAFL.

The motoring panels are in excess of the battery charging panels. No loss of charging ability.

And I am not a Harsh Mistress, I prefer to think of myself as a Gimlet-eyed Taskmaster.