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Old 08-08-2020, 00:26   #2101
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Re: Oceanvolt Hybrid Motor

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Originally Posted by Jim Cate View Post
Well, you have hit upon a factor not often mentioned in these discussions about solar:season!

The yields quoted for PV somehow are always at high noon in a low latitude area with no cloud cover. My observation is that when you venture into mid latitudes reality is not as good to you. For instance, here in Tassie, lat ~43 S, in summer the days are pretty long, and that almost makes up for the low sun angle, and our mere 400 watts is quite adequate. Around the equinox things deteriorate rather rapidly, what with lower angles and shorter days. Now in the pit of winter, on sunny days we were getting peaks of 400 Whrs a day with <100 all too often as compared to our 1500+ Whr/day in summer, and more than that back in the Sydney area (lat ~33 S) and doubtless greater than that in the tropics (we've not had these panels in the tropics yet). Having the ability to tilt the panels would certainly help, but that is not possible in many installations, and ours is one of them. And for those who only cruise in the summer, and in temperate latitudes, not so much of a worry for sure. For long term and far ranging cruisers, it matters.

I post this not to refute any claims but perhaps to temper the expectations expressed in many threads here on CF. They often seem hopelessly optimistic to me.

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And a lot of us spend far more time stationary at anchor than actually sailing and when we sail tend to travel at very moderate speeds so regen is not going to do a lot for us.
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Old 08-08-2020, 01:43   #2102
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Re: Oceanvolt Hybrid Motor

In San Francisco the tidal currents can be up to 6 knots, average probably moreliek 3-4. Probably get a few watts if you are anchored somewhere with a decent current? Peak flow probably a couple hours a day twice a day? Enough to run the fridge?
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Old 08-08-2020, 02:39   #2103
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Re: Oceanvolt Hybrid Motor

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In San Francisco the tidal currents can be up to 6 knots, average probably moreliek 3-4. Probably get a few watts if you are anchored somewhere with a decent current? Peak flow probably a couple hours a day twice a day? Enough to run the fridge?

Also you find some significant tidal currents in the islands of the Salish Sea and thereabouts. Cattle Pass is a boiling cauldron multiple times per day. And rocks are just waiting to ruin your cruise.
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Old 08-08-2020, 02:45   #2104
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Re: Oceanvolt Hybrid Motor

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Originally Posted by Adelie View Post
1. Regen puts opposite direction loads on the thrust bearing. If the bearing is designed for or is able to handle long term loads in that direction no problem.
It’s not just the thrust bearings. It’s the entire rig and hull that has to sustain a higher load for regen.
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Old 08-08-2020, 05:19   #2105
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Re: Oceanvolt Hybrid Motor

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It’s not just the thrust bearings. It’s the entire rig and hull that has to sustain a higher load for regen.

A negligible higher load. Your "concerns" would like freaking out that you are cruising at 7.2 knots instead of 7 knots. Sailing at 7.2 knots the sails, mast, rigging and hull ARE sustaining a higher load than at 7 knots. I am sure you consistently reef to knock that 7.2 knots down to <7 in order to prevent prematurely aging your boat right?

The sillier thing is that unless you replaced your entire sailplan to increase the sail area to compensate for the added drag from regen it is ZERO increased load. The sailplan with a fixed amount of wind and point of sail has a fixed amount of power. The regen comes from taking a part of that power. Electricity from a small reduction in speed. So it is the same load just a question of going say 7.2 knots without regn vs 7 knots with regen. In both scenarios the load and thus power produced by the sails is identical. In the former all of that is being converted into propulsion in the later say 95%+ of that is being converted into propulsion and 5% into electrical energy for storage.

I think some people are vast underestimating just how much power are produced by sails. It takes a lot of power to push a 40 foot 10 ton boat to 7 knots, something in the ballpark of 10 KW. Because power to overcome drag is exponential the power diverted to regen only makes a small difference in speed.
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Old 08-08-2020, 06:12   #2106
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Re: Oceanvolt Hybrid Motor

The power needed to make regen power is nearly the same power needed to overcome the loss in speed due to regen. And it is not an efficient way to make electricity.
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Old 08-08-2020, 06:12   #2107
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Re: Oceanvolt Hybrid Motor

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Originally Posted by transmitterdan View Post
It’s not just the thrust bearings. It’s the entire rig and hull that has to sustain a higher load for regen.
transmitterdan: You're right that we need some good measurements. And I'm having trouble finding consistent estimates as well.

As for this concern: a few people have addressed it on this thread (as well as several others of your fears). In particular, several people have pointed out various ways in which your estimation techniques seem inconsistent with experience and other valid lines of reasoning, and are somewhat likely to produce inaccurate results.

We're trying to use the hivemind to get a better handle on the problem, costs, benefits, etc. There is plenty of anecdotal information out there that I think you could do a better job of assimilating. Why don't you join us?
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Old 08-08-2020, 06:35   #2108
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Re: Oceanvolt Hybrid Motor

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The power needed to make regen power is nearly the same power needed to overcome the loss in speed due to regen. And it is not an efficient way to make electricity.
It can't both decrease the vessel speed AND increase the load on the sails/rigging/mast. If the load on the sailing structure was increasing the speed wouldn't be decreasing. You could have marginal increase in the load on the sailing structure (by upgrading to a higher sail plan) OR you could have a marginal reduction in speed (same amount of propulsive power produce by the wind and some small percentage diverted to produce electricity).

Quote:
In the case of the round-the-world cruiser, we recommend a hybrid system with a backup genset to support continuous drive when/if needed,” says Oceanvolt CEO Markus Mustelin. “A regenerating prop, which spins while sailing and recharges the batteries (sacrificing 0.2-0.4 of a knot, depending on the boat and conditions) makes it possible to be almost independent of the genset and use it only for backup.”
https://www.yachtingworld.com/featur...-yachts-120908
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Old 08-08-2020, 07:48   #2109
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Re: Oceanvolt Hybrid Motor

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It can't both decrease the vessel speed AND increase the load on the sails/rigging/mast. If the load on the sailing structure was increasing the speed wouldn't be decreasing. You could have marginal increase in the load on the sailing structure (by upgrading to a higher sail plan) OR you could have a marginal reduction in speed (same amount of propulsive power produce by the wind and some small percentage diverted to produce electricity).


https://www.yachtingworld.com/featur...-yachts-120908

Now you are talking about a perpetual motion machine.

If the boat slows but wind speed is constant then the force upon the sails and rigging has to increase. It’s a fundamental law of nature.

Converting wind power to motion through the water then that motion into propeller rotation and that rotation into electrical energy requires extra forces on the sails, rigging and hull compared to no regen. The extra wind energy expended in producing the electrical energy is easily quantifiable. The fact that no seller of electric propulsion spells that out in plain language literature tells us a lot.

Another minor loss associated with regen is increased leeway. So not only is there a loss in STW but unless sailing dead down wind there is a loss in VMG to our destination. There is no free lunch in sailing.

I am an electrical engineer. I love electric vehicles. I owe a great debt to electricity as we all do. But it ain’t a religion. It’s all quantifiable.
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Old 08-08-2020, 09:27   #2110
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Re: Oceanvolt Hybrid Motor

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Originally Posted by transmitterdan View Post
It’s not just the thrust bearings. It’s the entire rig and hull that has to sustain a higher load for regen.


The added load on the rig due to prop drag is marginal.
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Old 08-08-2020, 11:55   #2111
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Re: Oceanvolt Hybrid Motor

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The added load on the rig due to prop drag is marginal.

If the boat slows a knot out of 10 it isn’t a marginal load IMO. That’s significant lost power. The rig efficiency is less. And unless going downwind, the heeling forces increase as the boat slows.
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Old 08-08-2020, 16:35   #2112
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Re: Oceanvolt Hybrid Motor

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If the boat slows a knot out of 10 it isn’t a marginal load IMO. That’s significant lost power. The rig efficiency is less. And unless going downwind, the heeling forces increase as the boat slows.
It's not going to cost you a knot of boatspeed when you are going 10kt, it's going to cost you a knot of boat speed when you are going 4kt.

At 10kt it's going to cost a 1/4kt or less.
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Old 08-08-2020, 20:40   #2113
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Re: Oceanvolt Hybrid Motor

I can tell you from personal experience, as I've stated before, that at 8 knots I could not pick it when the regen was started and stopped. I was being generous when I said maybe half a knot, so I think Adelie is close to the mark. We need an EP owner to video this regen ON/OFF effect on boat speed so the naysayers can see their fallacies directly. I promise to do that during sea trials if nobody does it sooner, which I hope happens.

Since solar was brought into the discussion I thought I'd give our solar expectations as it relates to motoring on solar alone with our boat specs and the OV AXC20. It may be of interest to other multihullers considering EP.

Here are the parameters:

LOA 15.25m
LWL 15m
BOA 8m
Lwl:Bh 12.25:1
DWL 12.5T
LFP propulsion bank 14kW. We will have auto genset on at 30% SOC so about 10kW useable between cycles.
DC genset charging 15kW continuous at 2200 rpm using 3 liters/hour (engine is Yanmar 3YM30AE)
Solar array 4.33kW nominal made up of 10 x 325w + 4 x 270w PV. Actual output between 20 degrees N & S expected to be 75% of nominal over 5 hours between 10am & 3pm. This is about 3kW for the 5 hour max output period.
AXC20 consumes 3kW to push our cat at 4 knots against a resistance of 700 Newtons. Going one knot faster more than doubles the resistance and the battery consumption goes up accordingly.

So it is expected to go like this for motoring on EP through the calms.

Discounting the solar gathered before 10am, we start with full battery at 10am and motor silently on solar output for 5 hours on 3kW from PV until 3pm.
We continue ( still silently) at 4 knots on battery for 3 hours until 6pm when the genset comes on at 30% SOC and runs for about an hour ( actually 45 minutes but lets keep it simple) to recharge the 10kW used until 7pm. We can go a bit faster during genset time because we have some "excess" charge we can use.
Then it's back to battery silent running ( ahhhhhh, nice) for another 3 hour run,

This cycle repeats as needed as long as the calm lasts or fuel lasts, but as you'll soon see, running out of fuel is enlikely.

So by 10am the next morning, we have had 4 genset cycles of 1 hour each and then the PV kicks in again.

We use 3 liters an hour so we've used 12 liters to travel 96nm. in the calms, minimum, assuming no wind at all.

Whereas on a diesel ICE we'd have burned 74 liters of juice.

If the wind came up during the night we would use, you guessed it, regen to put some Amps back in the bank instead of running the genset.

12 liters vs 74 liters. 4 hours of noise ( 20 hours of quiet) and fumes in the cockpit vs 24 hours ( and zero hours of quiet).

Hmm,seems pretty good to me, and a completely viable cruising solution.
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Old 08-08-2020, 23:56   #2114
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Re: Oceanvolt Hybrid Motor

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Originally Posted by transmitterdan View Post
If the boat slows a knot out of 10 it isn’t a marginal load IMO. That’s significant lost power. The rig efficiency is less. And unless going downwind, the heeling forces increase as the boat slows.
I have read that a cat with standard props go "about a knot" slower than the same cat with folding props, isnt having regen props the same as having fixed (in terms of drag and stress etc?)
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Old 09-08-2020, 02:08   #2115
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Re: Oceanvolt Hybrid Motor

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I have read that a cat with standard props go "about a knot" slower than the same cat with folding props, isnt having regen props the same as having fixed (in terms of drag and stress etc?)
No, not the way OV do regen. I can't speak for other vendors as I just don't know.

It used to be with some other systems that you would put the feathering prop in reverse position and then drag it forward while sailing to spin the shaft in reverse. In that case, yes you certainly would be generating drag. But in the case of the OV systems, the water flow spins the prop faster while the folding or feathering prop is only partially "opened" which generates the regen with very little drag.

You can see this video on the OV site under the Hydrogeneration section.
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