Oceanvolt Hybrid Motor

[BigBeakie]

Yes we put the AXC20 in port hull just aft of the DC genset so it was all close to our main electrical cabinet and 14kW LFP propulsion bank & this cut down our runs of the 95mm2 cabling.The 45HP Beta diesel in stbd hull, both are centrally located for weight balance.

As it was a new build we went with the small strut which gave us the most cooling surface area which was better we thought for tropical water temps.

The install was straightforward, but Covid has greatly delayed our progress toward launch so we haven't used the motor yet, sorry to say.

[yvest]

Originally Posted by BigBeakie

Yes we put the AXC20 in port hull just aft of the DC genset so it was all close to our main electrical cabinet and 14kW LFP propulsion bank & this cut down our runs of the 95mm2 cabling.The 45HP Beta diesel in stbd hull, both are centrally located for weight balance.

As it was a new build we went with the small strut which gave us the most cooling surface area which was better we thought for tropical water temps.

The install was straightforward, but Covid has greatly delayed our progress toward launch so we haven't used the motor yet, sorry to say.

Ok, can understand ..., any target date for the launch ?
Hope we will get feed back soon after !

[BigBeakie]

Launch date = Depends. How long is a pandemic?

We came back to Oz in early March thinking it would be better to be here than staying in Thailand. Turned out to be perhaps the wrong decision as Thailand has, somehow (and it's still a mystery to me) avoided COVID-19 better than Australia. We can't leave Oz and until that changes the boat build is on hold. Frustrating? You betcha!!!

[RaymondR]

Originally Posted by BigBeakie

yvest,

Yes the operation of the regen on regular folding props is somewhat counterintuitive at first, but basically, and simply, the motor controller is smart enough to monitor, and control, the prop rpm. So when the flowing water pressure over the blades is trying to collapse the blades ( and drop the RPM), the motor spins the prop just enough to open up the blades so the water can turn the prop. The amount of power it takes to do this is quite low, so as the boat speed increases, the extra RPM from the water flow generates power in excess of what is being used to keep the blades open. The faster the boatspeed, the greater the delta between the power used to keep the blades open and the power being generated.

This explanation has a whiff of perpetual motion about it?

[fugue137]

Originally Posted by transmitterdan

Because the first law of cruising says, “There is no free lunch.”

1) Regen puts more stress on the boat and rig.

One would expect a 300-W system to put about that order of load on the system (maybe twice that due to inefficiency). Probably much less load than a submerged propeller.

1a) It requires over canvassing to power the hydro generation. So it leads to later rather than earlier reefing which we should all know is a bad idea.

A little extra resistance will decrease speed, but if you accept that, it shouldn't affect heeling / capsize potential. If you're reefing according to speed rather than according to capsize potential, you're probably in a monohull.

But let's say you're reefing according to speed. Let's say you're sailing at 10 knots, charging at ~300 W. Multihulls are easily driven so that's not nothing, but to get an idea of the power available: how much power does it take to motor your boat at e.g. 10 knots? Small cruising cat, probably around 40,000 W? So we're talking roughly a 1% change in power required. I think that's a bit... academic?

To get another rough idea of the speed loss, look at whether hardcore racers are using regen systems. I know of more who use Watt+Sea than Oceanvolt (I'd love to hear otherwise), but it's probably a good way to judge how much the system will slow you down.

2) Regen electronics are complex and more expensive. Try repairing a system in the South Pacific after accidental flooding.

Yup, that's true. On the other hand, devices consisting of dozens of moving parts that require maintenance schedules and lubricants have some potential to be troublesome as well. I'd love to see recent numbers on actual reliability and repairability in the field, and I might be inclined to just throw a spare charge controller in a ziploc just in case. As with all parts of a boat, saying "it could potentially fail beyond repair, therefore it has no place on a boat" is a non-starter: everything could possibly fail beyond repair. As you noted, there's a cost/benefit analysis here.

3) Larger battery banks are needed to store the energy.

Having more ways to generate electricity means you need *less* storage capacity.

I assume I should be interpreting this as "Larger battery banks are required due to the fact that you will need more electricity"? Battery energy specific gravity is limping along at around 100 times lower than fossil fuels. The gap is narrowed somewhat by the better conversion efficiency (factor of at least 3 for both propulsion and cooking) and the lower conversion weight (i.e. electric motors are much lighter (and lower maintenance)) than ICEs (e.g. for my own needs (starting with a boat that sails really well) an electric outboard system with sufficient range for me is about half the weight of an ICE outboard system, and the weight is better positioned too). Then add the fact that you can refuel anywhere there's sun or wind rather than only at gas stations.

But sure, fossil fuels are still "the best" (non-nuclear) way to carry a lot of energy, if you ignore the catastrophic costs of using fossil fuels... still... after at least half a century of finding out over and over again every few months that the need to stop using fossil fuels is far more urgent than we thought :'( I'd think we should be dropping everything to make this happen.

[transmitterdan]

Here is how to estimate the efficiency of hydro regen. If regen reduces speed by 1 knot (say 10 down to 9) then how much more power does it take to speed the boat back up from 9 to 10 knots? Certainly a lot more than 300W or 500W. It takes a few kW to do that.

[harlem24]

Question is, why not stay at 9kt?

[Seaslug Caravan]

Originally Posted by harlem24

Question is, why not stay at 9kt?

Once again we appear to be in fantasy land.

I just finished reading a blog from a couple on an Outremer 51 crossing the Pacific.

Maximum daily runs of 200 miles (approx av) . Many days were a lot less.

So average speed for regen would be 7 knots in ideal down wind trade conditions.

No where near 9 or 10.

[transmitterdan]

Originally Posted by harlem24

Question is, why not stay at 9kt?

Because then regen is useless for propulsion. You would be better off reaching your destination sooner.

[fugue137]

Originally Posted by transmitterdan

Because then regen is useless for propulsion. You would be better off reaching your destination sooner.

If regen drops you from 10 knots to 9 for 1 hour (I find it far more likely that you'll lose more like 1 or 2% of speed, not 10%), and then allows you to motor through a crowded mooring field and manoeuvre into a slip at the destination rather than wait for just the right wind to sail in, you lose little and gain much. Likewise, losing 10% of your speed for a few hours and then motoring at 3 knots for 4 hours rather than drifting at 0 knots until the wind picks up will save you a lot of time.

If you're better off reaching your destination sooner, then stop messing around with boats and just fly.

[fugue137]

Originally Posted by transmitterdan

Here is how to estimate the efficiency of hydro regen. If regen reduces speed by 1 knot (say 10 down to 9) then how much more power does it take to speed the boat back up from 9 to 10 knots? Certainly a lot more than 300W or 500W. It takes a few kW to do that.

True, but probably not generally relevant because this computation seems to come at the problem backwards.

The approach I would take instead: How much power do you use? Then figure out how much that will slow you down.

Hmm. Upon doing my homework and reading more of this thread, I see that people are talking about losing a knot, and also talking about 2--4 kW of generation. I also see various reports that "back in the early days, people talked about losing a knot of speed, but since then efficiency has improved." Obviously it will depend on how much power you're extracting... for 2 kW on a small multihull I believe those numbers, and I grant that I'd feel 2 kW on any multihull small enough to be fun to sail. On the other hand, once you get into the realm of 100 m^2 of sail area I don't think 2 kW would be such a big deal. A cruising monohull going hull speed wouldn't notice at all.

For how long will you run a 2-kW generator before you shut it off and resume sailing at full speed? Assuming an appropriate breeze:

• If you're running nav, radar, refrigeration, lights, etc., you might be using ~100 W. In that case, running a 2-kW generator for about an hour a day would keep your batteries topped off.
• If you have e.g. 4 kWh of battery capacity (a small propulsion battery; e.g. to run an ePropulsion or Torqueedo "10-HP-equivalent" motor around full speed for an hour), a full recharge would take ~2 hours.
• If you have e.g. 20 kWh of battery capacity (incidentally that's ~300 lbs of LiFePo4 or >1000 lbs of lead-acid batteries; unlikely on a multihull with less than 100 m^2 of sail!), and you run them down reasonably frequently, then I could see wanting to run a 2-kW generator (overnight, in fact, to return your completely drained batteries to 100%). But let's not beg the question: if you are using 20 kW of electricity every day on a boat designed to be propelled by the wind, what's going on? It might be a sign that something is wrong.

In any case, if the generator costs you a knot (maybe the absolute worst case for a 2-kW generator, unless you're running it on your Hobie or something...), each hour you're running it will reduce your daily mileage by 1.

Losing a knot for a few hours doesn't seem terrible, though. Especially if you're bashing to windward at 10 knots---sometimes I'll slow down to 7 for comfort, or at night if there's debris in the water. Being able to do so at the press of a button seems even more luxurious than even the best jiffy reefing. In other words, I could see learning to work with such a system to change the cost/benefit map.

It appears that some cruisers like the 300-W Watt+Sea generators. I wonder how much more efficient (i.e. how much more energy/drag) those are than Oceanvolt's systems: obviously some, since a propeller optimised for 10000 W of thrust is very diferent from a turbine designed for 300 W of extraction (reynolds number, size, blade chord, opposite direction of thrust (low-pressure side of blades forward during thrust but aft for regen), etc). So there's another avenue that might be worth looking into.

[harlem24]

Originally Posted by Seaslug Caravan

Once again we appear to be in fantasy land.

I just finished reading a blog from a couple on an Outremer 51 crossing the Pacific.

Maximum daily runs of 200 miles (approx av) . Many days were a lot less.

So average speed for regen would be 7 knots in ideal down wind trade conditions.

No where near 9 or 10.

So what? Then it's 7kn and 350W regen? You would generate 8.4kWh within 24h, that is more then enough to run all the appliences and even an AC for a time. And don't forget the solar, most new boats come with about 1,5kWp to 2kWp, we still talking about multis here. That gives you an additinonal 12kWh at 80% and 8 hours sunlight. That is 20kWh production on a passage a day! That's huge.
It's about charging the batterie and keeping the missis happy...
Because if you don't have to look at your consumption and can let's say produce water every second day, everbody is happy.
Nothing worse then doing it camping style with a bucket and then rinse off...

[transmitterdan]

Well it’s 6kn and 350W regen. Passage takes 14% longer whilst regen running.

For those hoping to get 2kW out of regen, you are dreaming. We are discussing cruising boats making 200 mile days. Not racing sleds making 400 miles per day.

My method of evaluating regen efficiency is the only “non-hand waving” method. Let’s see your results of this super simple method.

[Statistical]

Originally Posted by transmitterdan

Well it’s 6kn and 350W regen. Passage takes 14% longer whilst regen running.

For those hoping to get 2kW out of regen, you are dreaming. We are discussing cruising boats making 200 mile days. Not racing sleds making 400 miles per day.

My method of evaluating regen efficiency is the only “non-hand waving” method. Let’s see your results of this super simple method.

Why are you assuming that regen reduces speed by a full knot. Do you know how much power difference there is between 6 and 7 knots on a moderately sized sailing vessel?

What if it is 7 knots w/o regen and 6.8 knots with it. I do however agree 2 KW regen is probably unrealistic. I guess a system designed to do that could but only at very high speeds with significant reduction in speed so while it might happen briefly on some boat under some conditions expecting that as a typical performance is hyper optimistic. However 300 to 600W of regen even with low efficiency shouldn't be reducing sailing speed by a full knot.

[transmitterdan]

Well everyone here says regen reduces 1 knot.

You are exactly right about the power lost in a 1 knot reduction. It’s a lot more than you can ever get from regen so it’s very inefficient.