Circumnavigating using Electric Propulsion

[CarlF]

It's unfortunate that more work hasn't been done on efficient and practical water power generators. Moving water has tremendous energy density (think hydro-electric dams). Far better than solar or wind.

Once a sailboat gets above about 80% of hull speed it starts throwing away the sail generated wind power. For little or no reduction in speed, sailboats could generate a lot of electricity whenever apparent winds are above 15 knots or so.

[skipmac]

Originally Posted by CarlF

It's unfortunate that more work hasn't been done on efficient and practical water power generators. Moving water has tremendous energy density (think hydro-electric dams). Far better than solar or wind.

Once a sailboat gets above about 80% of hull speed it starts throwing away the sail generated wind power. For little or no reduction in speed, sailboats could generate a lot of electricity whenever apparent winds are above 15 knots or so.

Water can certainly generate a lot more power than wind but seems like it is a much trickier design problem.

Water generators experienced a small, short surge of popularity years ago but due to problems with the practical application lost favor. The type that tows a spinner or prop on a line had two problems. They fouled in seaweed or trash in the water and sharks tended to bite them, sometimes ripping the whole unit off the boat. I think the fouling might be mitigated to some extent by the design of the spinner, maybe a tapered shape that would shed the trash, but don't see a solution to the shark bite problem.

There is a new unit that drives a prop on a skeg that raises and lowers from the transom. Hydrogénérateurs Watt&Sea : votre voilier autonome en énergie | According to the distributor puts out about 10 amps at 5 kts. Cost $4900 plus a few bits and pieces for the installation. Also need space on the transom and if you have a sugar scoop or sharply angled transom a custom installation. They appear to be simple to raise and lower so should be easy to clear if the prop fouls but still need room close to the center line on the transom.

[skipmac]

Originally Posted by SunDevil

Boat - SolarWave

transatlantic21: The world's first crossing of the Atlantic on a solar boat

I still think that since other people have done it, it is possible. I would make a few improvements myself to the amount of batteries personally. For $12,000 and 800 lbs, you could get 1725 usable amps out of LiFePO4 batteries @12 V, or 20kWh. Add in a wind turbine design to help when the wind is blowing at night, and a large enough array like the above boats, and pick your weather windows based on it not raining...I would like to try it and see.

The other option that few people talk about is if your batteries are drained, couldn't you just pull into a marina, plug in, and charge them back up?

I think that electric power for a sailboat is quite possible but with some limitations.

A fairly simple, affordable system will have very limited range and power, essentially enough to get from the dock down the channel to the ocean. Beyond that you're sailing. Current systems limited to about 25 HP.

For a lot more money you can add more batteries and a large generator to allow powering a reasonable distance, say min 100 miles.

For even more money you have a system custom built that will power something bigger than 30-35'.

Or there may be components available to build your own system for a reasonable cost but you better be pretty well versed in electrical and electronic technology.

Charging batteries at the marina is certainly an option but I think most of the discussion is focused on cruising boats that are not at a marina.

[an ark]

Originally Posted by skipmac

Water can certainly generate a lot more power than wind but seems like it is a much trickier design problem... Watt&Sea... 10 amps at 5 kts. Cost $4900... space on the transom...

regenerative motor sailing:
Electric Sailing
Regenerative Motor Sailing

solves two problems: 1) adds the third leg of the triad, hydro, to the renewable energy sources (along with solar/wind) (although technically hydro is just wind, unless you're anchored in a swift current) without additional cost/complexity/gear/drag, and 2) reducing/cancelling effect of drag from the large prop that is recommended for electric motors.

[GordMay]

Greetings and welcome aboard the CF, an ark.

Are you associated with Ikanos Technologies?

[skipmac]

Originally Posted by an ark

regenerative motor sailing:
Electric Sailing
Regenerative Motor Sailing

solves two problems: 1) adds the third leg of the triad, hydro, to the renewable energy sources (along with solar/wind) (although technically hydro is just wind, unless you're anchored in a swift current) without additional cost/complexity/gear/drag, and 2) reducing/cancelling effect of drag from the large prop that is recommended for electric motors.

Thanks. I was aware of the regen technololgy but of course only an option with an electric powered boat. I was thinking more of general cruiser use in previous posts about water gens.

I do have to disagree with your statement that regen will not add additional cost, complexity and drag to an electric drive. Without regen you can use a folding or feathering prop which can make a good bit of difference in light air so will add drag. I read the links you posted and one claims to idle the motor to keep the prop turning to match the boat speed until regen speed is reached. Excellent idea but you are using battery power to do this and at some point in time may run out of power in an extended light air sail. Also to regen you have to have a much different controller than the one used just to power the motor for drive and this comes add cost and complexity as well.

Bottom line, with electric power you will be limited to maybe and hour (maybe less) motoring time unless you have a generator and/or a very large, heavy, expensive, bulky battery bank. Fine for daysailors or cruisers that always sail ie no trips up the ICW, rivers, canals in Europe, etc. but a problem for any others.

[an ark]

Originally Posted by GordMay

Greetings and welcome aboard the CF, an ark.
Are you associated with Ikanos Technologies?

Thanks Gord! I've been lurking for so long I forgot I hadn't ever posted yet!

Not associated with them or any other company.

[an ark]

Originally Posted by skipmac

I do have to disagree with your statement that regen will not add additional cost, complexity and drag to an electric drive. Without regen you can use a folding or feathering prop which can make a good bit of difference in light air so will add drag. I read the links you posted and one claims to idle the motor to keep the prop turning to match the boat speed until regen speed is reached. Excellent idea but you are using battery power to do this and at some point in time may run out of power in an extended light air sail. Also to regen you have to have a much different controller than the one used just to power the motor for drive and this comes add cost and complexity as well.

But in light air it would take very little power to keep the prop moving at neutral-drag speed, and only a little more to actually increase the speed, which might be the time you want it most. From yet another vendor: "It takes about 250 watts to increase the boat speed by an additional 2 to 3 knots while sailing in low or no wind conditions... A 20 kWh battery pack can zero thrust a propeller for 300 hours, or add 2 knots to boat speed for 80 hours."

Originally Posted by skipmac

Also to regen you have to have a much different controller than the one used just to power the motor for drive and this comes add cost and complexity as well.

I'm not an expert but my understanding is that this 'feature' is available on most/all controllers. Can you (or anyone else) point to one or two that are more expensive and more complex? (I know that is a tough question because most vendors don't post pricing, but I do genuinely want to know.)

Originally Posted by skipmac

Bottom line, with electric power you will be limited to maybe and hour (maybe less) motoring time unless you have a generator and/or a very large, heavy, expensive, bulky battery bank. Fine for daysailors or cruisers that always sail ie no trips up the ICW, rivers, canals in Europe, etc. but a problem for any others.

True, and you forgot racers, for whom (I assume, please correct if I am mistaken) idling the prop to cancel drag is not allowed. However, some of the weight, size, and expense of the battery bank is offset, in the case a pure electric, by the reduced size of the motor and the lack of generator, diesel (weight and recurring expense), tank, thru-hulls, wiring, plumbing, maintenance, oil, filters, biocide, etc. etc.

[skipmac]

Originally Posted by an ark

But in light air it would take very little power to keep the prop moving at neutral-drag speed, and only a little more to actually increase the speed, which might be the time you want it most.

Exactly. Going upwind if I'm too lazy or impatient to tack I run the engine at 1/3 to 1/2 power with the main up and make pretty good speed. Just turning over the prop with electric to minimize drag would take very little power. But on a cruising boat over a long passage this can add up.

Originally Posted by an ark

From yet another vendor: "It takes about 250 watts to increase the boat speed by an additional 2 to 3 knots while sailing in low or no wind conditions... A 20 kWh battery pack can zero thrust a propeller for 300 hours, or add 2 knots to boat speed for 80 hours."

Well let's look at the math behind these numbers, in a simplified version.

250 Watts if you have a 12 V battery system is roughly 20 amps. Say you're motoring down the ICW and under way for 8 hours. That's amp hours. Unless using new and extremely expensive battery technology you need about four times that in your battery bank to avoid running the batteries down too low and damaging the battery. So 8 hours a day just to motor at 2-3 kts you need 640 amp hours you would need 4-5 large golf cart size, deep discharge batteries. This is for a small system you might use on a 25' boat so you're adding a few hundred pounds of batteries to move a small boat barely over idle speed.

I didn't take the time to go through all the math to determine if they are calculating the full capacity of the battery pack that is from fully charged to totally dead, but a 20 KWh battery pack would be 8-10 large golf cart batteries.

Originally Posted by an ark

I'm not an expert but my understanding is that this 'feature' is available on most/all controllers. Can you (or anyone else) point to one or two that are more expensive and more complex? (I know that is a tough question because most vendors don't post pricing, but I do genuinely want to know.).

To be honest I've never gotten that far into the issue since the costs, weight and range restrictions kill my interest right off the bat. I do know that there are systems that do not regen but can't say how much you save in the controller.

Originally Posted by an ark

True, and you forgot racers, for whom (I assume, please correct if I am mistaken) idling the prop to cancel drag is not allowed. However, some of the weight, size, and expense of the battery bank is offset, in the case a pure electric, by the reduced size of the motor and the lack of generator, diesel (weight and recurring expense), tank, thru-hulls, wiring, plumbing, maintenance, oil, filters, biocide, etc. etc.

If a race boat has an electric on board just to get from the dock to the channel they can also put on just enough battery to get them out of the slip.

Like I said, there are applications where electric makes sense and racing may be one, but for the average cruiser I think not yet.

[SunDevil]

Winston Thunder Sky Lithium Battery LiFePO4 1000AH | eBay

Battery technology is improving. It is still pricey, but diesel over a 10 year period isn't cheap either. You would probably need 8 of those which will be ~600 lbs for a 24V, 1000Ah system, where 70% is easily usable, and 90% could be used. $11,000 today, might be less if a US company actually made them and sold them to the general public. It is good for at least 3,000 full cycles to 70% DoD. But, I'm not sure how many real world tests there have been.

With this battery you could travel for 35 hours at you 20 Ah amount without getting the battery too low, and with no regen.

[smaarch]

i'll admit this is all an interesting exercise and clearly a direction for the future but one of the things no one talks about when it comes to batteries is the pollution factor. the trend is to talk about how "green" electric power is. I'm not so sure. nor am i especially knowledgeable about this technology or a greenie
batteries are made out of nasty things...."do not dispose of.."
I also imagine they take lots of energy to produce....therefore their high cost

to my mind just because there are no exhaust fumes immediately in my wake.....doesn't mean there aren't environmental repercussions. at the moment they are just "invisible" to the user.
I'm not yet buying the environmental aspect.

[skipmac]

Originally Posted by SunDevil

Winston Thunder Sky Lithium Battery LiFePO4 1000AH | eBay

Battery technology is improving. It is still pricey, but diesel over a 10 year period isn't cheap either. You would probably need 8 of those which will be ~600 lbs for a 24V, 1000Ah system, where 70% is easily usable, and 90% could be used. $11,000 today, might be less if a US company actually made them and sold them to the general public. It is good for at least 3,000 full cycles to 70% DoD. But, I'm not sure how many real world tests there have been.

With this battery you could travel for 35 hours at you 20 Ah amount without getting the battery too low, and with no regen.

The LiFePO4 technology sounds great and I would really love to have them onboard, once the price drops to about 25% of current levels.

For $11,000 a small boat could buy and install a diesel that would last for 30 years and have money left over to pay for fuel.

[mcarling]

Originally Posted by smaarch

to my mind just because there are no exhaust fumes immediately in my wake.....doesn't mean there aren't environmental repercussions. at the moment they are just "invisible" to the user.

You're right. This is the classical problem of negative externalities such as pollution.

Originally Posted by smaarch

batteries are made out of nasty things...."do not dispose of.."

The toxicity varies greatly among different battery technologies. For example, lead acid batteries and alkaline batteries are relatively more toxic while liquid metal batteries (which will never be a good choice for sailboats) and lithium phosphate batteries are relatively less toxic.

The developments we can expect to see over the next five years are:
- lithium phosphate will become the dominant battery technology for all vessels from dinghies to aircraft carriers,
- marine solar panels will shift from 12V dominating the current 6-48V range to 48V dominating a 12-144V range,
- 10-40% cost reduction per year for solar panels and lithium phosphate batteries, and
- 144V will become dominant for battery banks.

Looking farther into the future, the US and UK navies plan to use 750-2000V DC for warship propulsion and are looking into the possibility of 15KV DC. Depending on how that goes, sailboats might some day have DC voltages up to 750V, but not within the next five years.

[Gabrieln]

I read an article comparing the new VW diesel engines and the hybrids. Bottom line, surprisingly enough, the new (at the time) Golf was more energy efficient than all the hybrids. If we sum up all the marginal financial and "environmental" costs like the PV panels manufacturing, proper disposal of batteries and etc., probably this conclusion may be even more obvious.
So, maybe the way to go is to use better/newer diesel engines.

[goboatingnow]

Originally Posted by Gabrieln

I read an article comparing the new VW diesel engines and the hybrids. Bottom line, surprisingly enough, the new (at the time) Golf was more energy efficient than all the hybrids. If we sum up all the marginal financial and "environmental" costs like the PV panels manufacturing, proper disposal of batteries and etc., probably this conclusion may be even more obvious.
So, maybe the way to go is to use better/newer diesel engines.

The latest BMW 520Td returns better economy then a Prius and its a 5 series to boot

Dave