Hi Fred,I agree with what HPEV told you. And it doesn't have anything to do with which motor or drive system that you use. It all depends on your boat, more specifically, your waterline length.People say that they like this forum because of the wealth of information that is available here. But I have found that most members aren't taking advantage of the history of the group.Here are a couple of posts that I made about regen back in 2012 and 2013.------------------------------------------------------------ Eric
Message 31 of 45 , Mar 28, 2012
Hi Tim,
That's not exactly what I said. What I said is that nobody seems to be able to generate more than 100W at 6kts. At higher speeds, much more power is available. I'm guessing that most streams flow at rates higher than 6kts, certainly so if one uses a collector and develops system head (fall of water) to accelerate the flow over the impeller or prop.
If your boat can sail at sustained speeds of 7 or 8kts or more, regen can become a significant source of energy. But for sailboats in the 30' range (the sweet spot for electric drive systems with 5-6kW of power and battery packs around 10kWh or 500 lbs.), hull speed is about 6.5kts and 6kts is about all you can average in winds less than Beaufort 6. So the energy from regeneration on most of our boats is limited.
Here's what I posted last September (post #19662)
"Since you brought up regen, I'll say it again. I haven't seen any substantiated report of 80W @ 5kts. Push the boat up to 6kts and I would be very surprised to see 120W of regen. I've seen brief moments of 60-70W while sailing my boat at 6kts but nothing consistent. Once a boat hits a consistent 8kts+ (big boats and multihulls), then regen starts to cover more than conservative house loads.
It's the data that nobody likes to hear, but if one motors at 4kts, you typically have to sail 40 times as long at 5kts to recover all the used energy. That means 15 minutes motoring at 4kts will take 10 hours at 5 knots to recharge the traction bank, longer if you're using any of the energy for house loads like lights, radio, or an autopilot. At 6kts, the time to recharge 15 minutes of 4kts motoring drops to 6.7 hours. Again, adding in any house loads extends the recharge time. But on a long passage, 100W for 24 hours does come to 2.4kWh. If you can keep your house usage to half of that, then 1.2kWh could end up back in your batteries. It will rarely be of any significant value during coastal hopping or gunkholing. I still want somebody to prove me wrong, I've been waiting for a while now...."
Mark from Santa Cruz just posted some preliminary figures after his recent prop change. He observed 1.8-2.2A (we'll call it 2A average) at 50-51V (we'll call it 51V) at 6kts. And the results are (drum roll please)........ 102W at 6kts. Hmmmm. I guess that I'm still waiting....
The bottom line is that I'm OK with these numbers. But this is not the impression that potential electric converts get when they read "Generates power while under sail" or "Most boats will start regenerating at 3.5 – 4 knots boat speed. When at, or near hull speed, the charging current should be around 4A – 6A." in an electric drive product description. While these figures might be true for some boats (as discussed earlier) it's not really true for most of the boats that these systems are sized for. Another vendor states "Not all boats will be able to achieve regeneration. The amount of power generated should be considered supplemental and comparable to what you can achieve through wind and solar chargers." This sounds closer to my personal experience.
The point is that I'm trying to share my practical experience to help people set realistic expectations of their electric conversions. We had another thread last year that discussed the article "Ditching Electric" from the magazine Classic Boat. The owners of the boat "Siandra" were removing their electric drive after three years. It appears that their biggest complaint was that their system did not regenerate as much energy as they expected and therefore their electric drive did not support their particular use case. Perhaps if they had been told how much power they would really get from regeneration, they would have found other ways to mitigate their energy deficit. As it was, they believed their salesperson, spent considerable money converting to electric, wrote a supportive article about electric conversion in 2008, got dissatisfied, spent considerable money converting back to diesel and wrote a less supportive article in 2011. I'm sure that their experience and exposure to their story hurt the electric boat community more than it helped. All stemming from unrealistic expectations.
Fair winds,
Eric
Marina del Rey, CA
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------------------------------ ----- And the second one
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------------------------------ ----- Eric
Aug 1, 2013
View Source
Hmmmm. That link proved my point perfectly. They stated that at 6kts, they could harvest 144Ah @ 12V in 24 hours. That's 2000Wh (allowing for charging voltage above 12V) divided by 24 hours works out to 84W of output from an "optimized" in-water towed generator. Alternatively, 350W of PV panels will generate the same amount of usable electricity in a 24 hour period, maybe more, near the equator or in the doldrums.
I still have yet to see anyone back up a claim of more than 100W at 6kts, even from a $10,000+ computer-controlled, variable-pitch, transom-mounted, in-water generator.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.
com , "Nick" <chernikit@...> wrote:
>
> Well - I'd certainly agree if you referring to a fixed pitch propulsion propeller being used for re-gen, but there are other ways to skin this cat. Prop's and generators optimised for the purpose can do better.
>
>
>
> http://www.cruisingworld.com/gear/electronics/green- power-on-passage
>
>
---In electricboats@yahoogroups.com, <berlouin@...> wrote :Has anyone getting propeller regeneration with HPEVs AC motor under sail. Could you please share your experience?
HPEVs had said I will get none or very little regeneration. I don't want to give any bad feeling about this motor AC 20. It works very well and is a good and economic replacement for a 30HP diesel
A few points / answers / views / remarks about the different threads on this forum
-I used a Ruland customised coupling from 1" prop to 7/8 motor shaft. No problem
-The most important is what you find, not what you will do ( as example, my end bearing was so rusty that after a month of spray and three mechanic tries, It could not be dismantled. The mechanic had to cut the prop shaft. So a gearhead was a luck to not have to replace the shaft.
-Planetary gear heads are advised (more choice, more reliable, less noisy but more expensive)
-I paid my LIFEPO4 batteries 100a x 48v around 1200 USD with customized SS boxes/ fixing brackets three years ago (Made in China)… So far, so good, I had to change the BMS
-The Austria systems are very expensive and for lake use. They did pretend to get 10% of regeneration from a pod…. Impossible. Bellman / Mastervolt did not pretend the regeneration.
-I just bought and returned a 48v DC petrol generator that you can find on Ebay (The yellow one available in 12/24/48v). It is made to extend the range of the electric three-wheel taxis in China. I got it on the web (Taiwan, Powerjack), it was shipped from China. The generator arrived with obvious signs of previous usage, 150mm longer than described, petrol engine not working, electric start not working. After repair of carb. , it did output 50 amps at 48v….certainly a nice extra for an electric boat. The electric start still did not work. I got my refund from PayPal
-I did change the shaft packing seal to a drip-less seal, they are plenty of different brands and method on the market. I choose the one advised by the boat builder/eng. ( sea water cooled with the stream to make life easy and without maintenance). My flat bilge is dry…. without engine oil, diesel, smells, headache… a dream
Fred
Posted by: orest iwaszko <orest@albernicharters.com>
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