Oceanvolt Servoprop regen tested by UMA

[Muaddib1116]

UMA is the sailboat on the homepage of Oceanvolt's website, right when the page loads, before the slideshow starts.

[Adelie]

Originally Posted by tkeithlu

No problem with it being low drag. The problem is that the energy used (drag) has to be more than the energy stored by the battery. In other words, the drag during generation will be more than the propulsion available as a result. It slows the boat by a fraction of a knot? It will propell the boat at a smaller fraction of a knot for the same distance/time. Any other outcome would be a perpetual motion machine.

That’s wrong.

Regen does NOT harvest speed from the boat moving thru the water, it harvests energy which is converted into electricity stored in the battery. Harvesting energy reduces speed. The speed-power relationship is not linear which means that when the boat is going faster you can harvest more energy with less impact on speed.

The Cal-34 I want uses about 7680W to go 6.3kt and 9120W to go 6.8kt. If the boat was going 6.8kt before turning on regen and 6.3kt after then regen is soaking up about 1440W from the boat. Let’s assume that all the losses account for 2/3 of the power harvested, so I will only get back out 500W.

If I sail like this for 10hr then I will have available 10hr * 500W = 5,000Whr or 5kWhr of energy. And I will have advanced 5nm less than I would have.

If The next day the wind goes calm I can use that stored energy to propel the boat. Let’s say I wanted to use the energy at the same rate I harvested it, 500W. That 500w would propel the same boat at about 2.5kt. 10hr at 2.5kt is 25nm. Accounting for 5nm I “lost” while generating the energy I’m still 20nm ahead.

If I went 2kt I would use 250-300W. Let’s assume 300W. 5kWhr would supply 300W for 16.7hr. At 2kt I would go about 33.3nm and would net 28nm accounting for the lost 5nm.

What if I went 5kt? Boat uses 3840W to go that speed. With 5kWhr I can motor at 5kt for 1.3hr which would move me forward 6.5nm. Accounting for the 5nm “lost” I’m still 1.5nm ahead.

You get more distance out of regen by using the fact that the power-speed relationship is non-linear and accepting that when you use the energy you need to go slower than when you harvested it.

If you can’t accept the slower speeds when using the stored energy then stick with an ICE.

Finally, I don’t have to use the energy to propel the boat, I can use to make light, cook, make or heat water. This is an apples to oranges tradeoff with different math than discussed above.

[George DuBose]

To NaClyDog. I am not inclined to believe EVERYTHING I see, but as I wrote, I have watch all of their videos, I have met them and Uma in person when they were in The Netherlands. I know what they have gone through and I have written an email to Dan Dekker to join this conversation and clarify if OceanVolt is sponsoring them, where they got their first OceanVolt system and again clarify the parameters they used in determining their comments on their YouTube channel.

I don't think it is fair or friendly for you to make only negative comments when you didn't take the time to what the video on the link posted in this blog or ANY of their other videos where they discuss their electric system.

Nobody said you were evil, just that one shouldn't make negative comments when one is ignorant about the topic being discussed.

[George DuBose]

Yes, Uma is displayed in one of the photos on the OceanVolt website. Uma is in a Norwegian fjord. Well, when Uma installed their first unsponsored OceanVolt, they were in the UK and that was probably two seasons ago.

Maybe OceanVolt finally woke up and smelled the coffee and is now giving Uma soe sponsorship, but knowing Finns, I doubt that OV is giving anything away for free...

I asked Dan Dekker of Sailing Uma to clarify some of the confusion and misunderstanding on this particular blog.

[Pete7]

Originally Posted by NaClyDog

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?
More marketing hype it seems...

I might be wrong, but I think they have two or more systems. One a straight forward electric drive which Uma originally had and a more expensive version with better regen. Bet the batteries are not included in that quote from OV.

[Muaddib1116]

Originally Posted by George DuBose

I doubt that OV is giving anything away for free...

I think that is NaClyDog's point.

[Muaddib1116]

At 3:30 in the video, Dan says that they are collaborating with Oceanvolt.

[NaClyDog]

Originally Posted by Muaddib1116

At 3:30 in the video, Dan says that they are collaborating with Oceanvolt.

I used to collaborate with my employees... they did the work and I did the paying.

[mglonnro]

Originally Posted by tp12

I don't think we have enough information, going by that article, to make that assumption

From my own conversations directly with OV, I understood that OV had voiced concerns about the Aventura Zero configuration, so indeed, they might well have questioned the sensibility.

[Adelie]

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?


More marketing hype it seems...

Is $40k OV’s price or is it the price that somebody further up the thread tossed out as a guess?

The SD8 is appropriate for up to a 35’ boat. Thurs site, https://plugboats.com/acadp_listings...t-saildrive-8/, indicates €13,000. It looks like that post was made within the last year.

Let’s add €2,000 for the ServoProp: so €15,000.

[NaClyDog]

Originally Posted by Adelie

Is $40k OV’s price or is it the price that somebody further up the thread tossed out as a guess?

The SD8 is appropriate for up to a 35’ boat. Thurs site, https://plugboats.com/acadp_listings...t-saildrive-8/, indicates €13,000. It looks like that post was made within the last year.

Let’s add €2,000 for the ServoProp: so €15,000.

I think Pete7 had it right when he guessed that doesn't include the battery bank. But, like I said in my post... marketing hype. If they aren't saying exactly how they got their numbers (the 20-25%) it's really meaningless because a bunch of different people will make a bunch of different assumptions. This thread being the perfect example!

[mglonnro]

Originally Posted by Adelie

Is $40k OV’s price or is it the price that somebody further up the thread tossed out as a guess?

The SD8 is appropriate for up to a 35’ boat. Thurs site, https://plugboats.com/acadp_listings...t-saildrive-8/, indicates €13,000. It looks like that post was made within the last year.

Let’s add €2,000 for the ServoProp: so €15,000.

"$40k" is the price for the whole system including batteries and stuff. I listed the details from a real quote earlier in the thread somewhere.

Here's a link to OV's own page with a price estimate for the whole package, sans installation (Uma has the SD15).

PRICE STARTING FROM: 38650€ (SD) / 46600€ (SERVOPROP)

https://oceanvolt.com/saildrive-15/

[Pete7]

Originally Posted by George DuBose

To NaClyDog. I don't think it is fair or friendly for you to make only negative comments when you didn't take the time to what the video on the link posted in this blog or ANY of their other videos where they discuss their electric system.

Those of us who have watched all the Uma videos will hear Dan regularly say he has been working with and seeking advice regularly from OV. I would be doing the same too. This isn't a simple 48v system and an electric motor. For a start its AC. In return for helpful free advice when you need it, I would give them a thumbs up and a nod on a blog site.

Pete

[mglonnro]

I found OV's own regen estimate chart, so here is that and the Uma chart again.

I didn't compare them yet, but to be fair, I don't know how much effort the lovely Uma people put into getting everything scientifically perfect. I assume they are best effort estimates. (Also, I'm don't know what the dark shaded bar means )

OV:

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

UMA:

[danstanford]

Originally Posted by Adelie

That’s wrong.

Regen does NOT harvest speed from the boat moving thru the water, it harvests energy which is converted into electricity stored in the battery. Harvesting energy reduces speed. The speed-power relationship is not linear which means that when the boat is going faster you can harvest more energy with less impact on speed.

The Cal-34 I want uses about 7680W to go 6.3kt and 9120W to go 6.8kt. If the boat was going 6.8kt before turning on regen and 6.3kt after then regen is soaking up about 1440W from the boat. Let’s assume that all the losses account for 2/3 of the power harvested, so I will only get back out 500W.

If I sail like this for 10hr then I will have available 10hr * 500W = 5,000Whr or 5kWhr of energy. And I will have advanced 5nm less than I would have.

If The next day the wind goes calm I can use that stored energy to propel the boat. Let’s say I wanted to use the energy at the same rate I harvested it, 500W. That 500w would propel the same boat at about 2.5kt. 10hr at 2.5kt is 25nm. Accounting for 5nm I “lost” while generating the energy I’m still 20nm ahead.

If I went 2kt I would use 250-300W. Let’s assume 300W. 5kWhr would supply 300W for 16.7hr. At 2kt I would go about 33.3nm and would net 28nm accounting for the lost 5nm.

What if I went 5kt? Boat uses 3840W to go that speed. With 5kWhr I can motor at 5kt for 1.3hr which would move me forward 6.5nm. Accounting for the 5nm “lost” I’m still 1.5nm ahead.

You get more distance out of regen by using the fact that the power-speed relationship is non-linear and accepting that when you use the energy you need to go slower than when you harvested it.

If you can’t accept the slower speeds when using the stored energy then stick with an ICE.

Finally, I don’t have to use the energy to propel the boat, I can use to make light, cook, make or heat water. This is an apples to oranges tradeoff with different math than discussed above.

Excellent and easy to understand analysis. Thanks for this.