Viability of electric only propulsion in 2018 - is there a good option after all?

[seandepagnier]

If you had a nuclear reactor you could motor for years without refueling. Lots of people have built reactors including a few teenagers. Diesel just doesn't measure up, since radioactive materials have a few orders of magnitude more energy density you can use a relatively inefficient thermocouple.

Is it a good idea for everyone to have reactors? Why or why not? Would the same conclusions be drawn for diesel power? For solar electric power?

All of these technologies have downsides that negatively affect other people. These costs are usually stolen since they are not paid for. Diesel is the most widely abused, and causing the destruction of the world as we know it.

Originally Posted by skipmac

BUT there is not enough room on a normal monohull to install enough panels to run all day under power.

How is it possible that I did run for 4-5 hours under power as well as charge my batteries at the same time in new zealand on my mono hull? I could have kept going, but then there was wind.

Most boats spend 90% or more of the time not going anywhere. So you motor only to arrive at anchor sooner? So waiting around at anchor instead of waiting for wind, what is the point? I have yet to see any real benefit from this concept of needless consumption, only a lot of excuses.

[skipmac]

Originally Posted by Nautoneer

I have posted two replies to this forum with details of a concept being discussed however, my posts are not showing.
Please advise.

Replies to this thread or another one?

[CatNewBee]

Originally Posted by boat_alexandra

If you had a nuclear reactor you could motor for years without refueling. Lots of people have built reactors including a few teenagers. Diesel just doesn't measure up, since radioactive materials have a few orders of magnitude more energy density you can use a relatively inefficient thermocouple.

Is it a good idea for everyone to have reactors? Why or why not? Would the same conclusions be drawn for diesel power? For solar electric power?

All of these technologies have downsides that negatively affect other people. These costs are usually stolen since they are not paid for. Diesel is the most widely abused, and causing the destruction of the world as we know it.


How is it possible that I did run for 4-5 hours under power as well as charge my batteries at the same time in new zealand on my mono hull? I could have kept going, but then there was wind.

Most boats spend 90% or more of the time not going anywhere. So you motor only to arrive at anchor sooner? So waiting around at anchor instead of waiting for wind, what is the point? I have yet to see any real benefit from this concept of needless consumption, only a lot of excuses.

There is no point to replace a seldom used diesel engine by a less useful and even less usable electric propulsion. It is just waste of money and resources.

[seandepagnier]

Originally Posted by fxykty

ather they’re trying to sail like the Pardy’s but with a more efficient version of a sculling oar.

Typical electric drive is 20-45% efficient and that is from electric power that is not efficiently generated. There is a lot of energy required to produce the motor, batteries solar panels to power it. Take that into account and you are lucky to achieve 2% efficiency from sunlight. This is still pretty remarkable. My solar electric system used to power me 2 knots (in sun) or 3 knots with battery drain. I could go 2 knots for 10 hours on my batteries.

Sculling oar is 85-90% efficient and it is good for you. It burns calories that would otherwise get wasted. The sculling oar grows as a tree, that is more efficient. You can realistically achieve 0.5-1% efficiency from sunlight, however, since food comes from land anyway, the sunlight captured can be a larger area than powering solar electric. There are other significant benefits including: reliability, fitness, energy storage in food, and beauty. With my sculling oar, I can go 1.5 knots.

I have tried both systems, and I kept the sculling oar.

solar panel efficiency -- their efficiency has already reached nearly 20%, which is not that far off their theoretical maximum.

Laboratories show the theoretical maximum to be 70-80%, so I would say we are a long way from theoretical maximum. The same is true for engines, so it doesn't mean it will ever be achieved, or can happen anytime soon, but I would expect cheap panels to reach 30-35% efficiency in 30 years or so.

[saghost]

Originally Posted by CatNewBee

There is no point to replace a seldom used diesel engine by a less useful and even less usable electric propulsion. It is just waste of money and resources.

Less weight? Less noise? Less maintenance? Better reliability? Better responsiveness?

For a sailing vessel that uses power to dock/anchor and doesn't expect to motor for days on end, I can see a lot of upsides to a pure electric system, and the only real downside is the cost.

Adding a DC diesel generator can address the motoring for days and any concerns about other power sources, especially if you can accept a slightly lower continuous speed (which it seems like most folks that are motoring use anyway - I seldom read of folks running the engines near WOT for motoring.)

[john61ct]

Hydro power on sailboats is not as common as solar nor wind,

but nothing new or innovative,

been around a long time, bog standard and readily available OTS for decades.

And no, it will not reliably produce much power, certainly not enough for practical propulsion needs, except as a science experiment in artificially constrained conditions.

https://goo.gl/CfVZ5W

[misfits]

Originally Posted by saghost

Less weight? Less noise? Less maintenance? Better reliability? Better responsiveness?

For a sailing vessel that uses power to dock/anchor and doesn't expect to motor for days on end, I can see a lot of upsides to a pure electric system, and the only real downside is the cost.

I wouldn't say less weight because FLA batteries are heavy but I agree with some of the other points. I have an electric drive & like it but it's not without it's shortcomings. Many that go electric tie up to slip & plug in. I'm on a mooring so I charge the battery bank with my solar system or a Honda generator which although it's quiet, I hate running it.

I can get 8-12 NM before hitting 50% DOD. For most of what I do that is adequate & meets my needs, cause after all it's a sailboat. Motorsailing with electric when you need a little boost is awesome. You can pick up anywhere between 1-2 knots, the motor is quiet & electric consumption is minimal.

However in my attempt to get the boat to it's winter home this year I ended up motor sailing against a tide with very little wind thanks to an inaccurate forecast from windy.com. I attempted a 22 mile haul & a mile from the yard after trying to tack & motorsail in the river for 5 hours I asked a fellow boater to tow me in. I made it 21 miles that day but my battery bank was depleted & there was no go go juice left in them.

My point is if you like motoring long distances or shoveling **** against a tide, electric probably isn't for you.

[Dockhead]

Originally Posted by saghost

Less weight? Less noise? Less maintenance? Better reliability? Better responsiveness?

For a sailing vessel that uses power to dock/anchor and doesn't expect to motor for days on end, I can see a lot of upsides to a pure electric system, and the only real downside is the cost.

Adding a DC diesel generator can address the motoring for days and any concerns about other power sources, especially if you can accept a slightly lower continuous speed (which it seems like most folks that are motoring use anyway - I seldom read of folks running the engines near WOT for motoring.)

Don't forget that a diesel generator driving an electric motor will be less efficient than driving the prop directly.


With a large enough battery bank, I think you could downsize the generator compared to the size propulsion engine you would need -- because we rarely need full power and only need it for relatively short periods of time, so you can use the batteries to "shave peaks". But on many boats that will still be a really big generator, and I can't imagine how you're going to end up with "less weight", compared to just driving the prop directly.



In my case for example -- I have a 100 hp main engine. I rarely take more than 40hp out of it, so I could be ok with downsizing that engine, driving a generator, but a 30kW (or whatever) generator STILL weighs more than a 100 hp propulsion engine and gearbox (like double), and on top of that you need a huge battery bank, and an electric motor.



I don't see any way you could have continuous motoring ability with less weight, from electric plus batteries plus generator, compared to traditional drive, and the whole system is definitely a lot more complexity and maintenance, not less.

[Dockhead]

Originally Posted by boat_alexandra

If you had a nuclear reactor you could motor for years without refueling. Lots of people have built reactors including a few teenagers. Diesel just doesn't measure up, since radioactive materials have a few orders of magnitude more energy density you can use a relatively inefficient thermocouple.

Is it a good idea for everyone to have reactors? Why or why not? Would the same conclusions be drawn for diesel power? For solar electric power?

I think nuclear power on cruising boat scale could be made quite safe, and the tiny volumes of waste involved can be disposed of (after 20 years) down salt mines. If you care about global warming (and acid rain, and . . . ) nuclear has got to be a better option.


Nuclear power would be a dream. Unlimited electrical power -- motor right around the world if you want. Ultimate autonomy, which would be just what we need, especially those of us who cruise in distant, remote places.



Unfortunately we will not get that in our lifetimes, methinks. . . .

[saghost]

Originally Posted by Dockhead

Don't forget that a diesel generator driving an electric motor will be less efficient than driving the prop directly.


With a large enough battery bank, I think you could downsize the generator compared to the size propulsion engine you would need -- because we rarely need full power and only need it for relatively short periods of time, so you can use the batteries to "shave peaks". But on many boats that will still be a really big generator, and I can't imagine how you're going to end up with "less weight", compared to just driving the prop directly.



In my case for example -- I have a 100 hp main engine. I rarely take more than 40hp out of it, so I could be ok with downsizing that engine, driving a generator, but a 30kW (or whatever) generator STILL weighs more than a 100 hp propulsion engine and gearbox (like double), and on top of that you need a huge battery bank, and an electric motor.



I don't see any way you could have continuous motoring ability with less weight, from electric plus batteries plus generator, compared to traditional drive, and the whole system is definitely a lot more complexity and maintenance, not less.

I don't have a handy 30 kW example to work with; unfortunately Polar Power stops at 20 kW right now, and the big synchronous AC generators are a horse of a different color entirely.

But take a typical modern small charter/liveaboard cat, like a Leopard 40 or Bali 4.0. They've got three smallish diesels onboard - two ~30 hp engines pushing saildrives, and a 6 kW diesel generator.

Yanmar 3YM30AE plus SD25 on each side, 346 pounds per side. Northern lights 6kW generator, 377 pounds without the sound enclosure.

Electric yacht 20SD 20 kW sail drives are 177 pounds each. If you're willing to lose a knot of top speed, Torqeedo Cruise 10 FP SD is a 10 kW motor pod on a sail drive mount that's only 83 pounds.

A Polar Power 8340-VP40 20 kW DC diesel generator is 396 pounds. An AIMS 5kW pure sine inverter is 34 pounds.

So an electric system with all the same functions can have 285 pounds of battery and still be the same weight, or 475 pounds of batteries if the cruise pods are good enough.

Torqeedo's 5kWh 48V sealed battery packs weigh 82 pounds each - meaning 15 kWh is still lighter with the big motors, or 40 kWh with the smaller ones.

This doesn't even include the two starter batteries you'd eliminate or downsizing the now largely redundant house battery pack (it also doesn't include the 48V-12V converter to charge the house pack from the main pack or a 48V charger for shore power, but I don't expect either of those to be very heavy.)

[Paul Elliott]

Originally Posted by Nautoneer

I have posted two replies to this forum with details of a concept being discussed however, my posts are not showing.
Please advise.

I can see two of your detailed posts. My comments:

An alternator is just a type of generator, one that puts out alternating current (AC) which has to be converted to DC for battery-charging, etc. Alternators have a field coil, through which an energizing current is run in order to create a magnetic field. This field current is controlled by the regulator, which can be as simple as a voltage-controlled relay. Alternators can be pretty efficient in converting mechanical energy to electricity. Most modern generators (such as the Honda "suitcase" units) contain an alternator, although these may use magnets rather than the field coil.

Anyway, there are plenty of towed, or stern-mounted power generators out there. Some of these use re-purposed automotive alternators, others use specialized alternators with fancy control electronics. And some people have connected an alternator to the freely-spinning prop-shaft to harvest energy while under sail. These all have different degrees of efficiency (drag vs power output), but there's hardly a free lunch with any of these methods. Here are some popular (but expensive) stern-mounted generators: https://www.wattandsea.com/en/produc...ydrogenerators

[GrowleyMonster]

Originally Posted by saghost

Less weight? Less noise? Less maintenance? Better reliability? Better responsiveness?

For a sailing vessel that uses power to dock/anchor and doesn't expect to motor for days on end, I can see a lot of upsides to a pure electric system, and the only real downside is the cost.

Adding a DC diesel generator can address the motoring for days and any concerns about other power sources, especially if you can accept a slightly lower continuous speed (which it seems like most folks that are motoring use anyway - I seldom read of folks running the engines near WOT for motoring.)

Cost? Actually, an electric drive can be put together for a bit over $2k, and even with new off the shelf gear, less than $3k. In other words, considerably less than a new diesel, and only about 50% more than an outboard and a good solid mounting bracket. After selling the old Atomic, my total cost including 15.56kw/hr bank was about $2300 if I recall correctly. Cost can rise a good bit if you want one of the nice turnkey systems, or fancy batteries, but still not too bad. And yes, it really shines for day sailing and shore charging! For cruising, the problem is having enough storage, and enough solar to make it more $/hr fuel efficient.



It must be conceded at this point that for long range sail/motor cruising with a lot of motoring, a diesel is still (sorta) needed for producing at least some of the power required. Even a big boat is difficult to mount over 1kw of solar without problems related to shading of the panels. And even for a boat under 30', you really need about 2kw of solar to be totally independant of infernal combustion. Good engineering practices can have a system where hydrocarbon fuels are supplemented enough by solar that it works out cheaper to operate, but not free, as in the case of a pure solar electric system. This is a lot of extra initial expense and complexity for a modest return. An owner who is up to the challenge can find it quite appropriate and satisfying. Others will rightly dismiss it as a major PITA due to not being a good fit for EP.



Nobody sails for free. Cheap maybe, but not free. Boats cost. sails cost. paint costs. rigging costs. Repairs. Replacements. For a SAILED sailboat, fuel costs are modest compared to all the rest. Dreamers, keep that in mind. I just moved a new-to-me 44' Bruce Roberts from backside of Gulfport, down Bayou Bernard and Biloxi Back Bay to New Orleans and burned about 8 gallons of fuel for the trip which was over half in inland waters. I even motored across Lake Pontchartrain, due to being practically alone at night handling big sails in a strong breeze. (motored through the Rigolets, a smart practice.) Yes, I will add an electric motor and solar panels to reduce fuel dependency, but $25 in fuel for a fairly heavy 44 footer in inshore/inland waters over a period of 26 hours is not a deal breaker. If I HAD to, I could have sailed across the lake once past the Highway 11 bridge and cut my fuel bill by probably 40%. SAIL a boat, and you don't need all that much fuel money. Cook and heat with diesel, solar for lighting, navigation, and comms, and you are in the game pretty cheap.



Day sailers don't have to dream, though. EP is easily implemented and is a great improvement over an ICE.

[Jim Cate]

I think nuclear power on cruising boat scale could be made quite safe, and the tiny volumes of waste involved can be disposed of (after 20 years) down salt mines.

DH, as a physicist, I'm kinda surprised at this statement. Of course, having been retired for over 30 years, I'm not current with developments, but your claim is pretty far from my idea of reality.

So, please explain how you propose to make a small reactor or whatever other nuclear power source you have in mind. I'd like one, please... if feasible, but I'm not holding my breath!

Jim

[saghost]

Originally Posted by Dockhead

Don't forget that a diesel generator driving an electric motor will be less efficient than driving the prop directly.

Yes and no. Yes, you're certainly correct that the conversion to electricity, charging the battery, and then converting energy back to motion in the electric motor are losses the simple propeller doesn't have.

However, a simple fixed propeller keeps the engine from ever running at the most efficient points (unless a more aggressive propeller pitch is selected that won't allow the engine to reach full rpms and produce full power.)

The generator, on the other hand, can be set to run at only the most efficient points. Starting with better engine efficiency, the overall efficiency should be similar or better for modern permanent magnet motors and generators.

Combining the power output and fuel consumption charts Yanmar publishes for the 3YM30AE, I came up with between 25% and 30% efficiency for the entire speed range. By contrast, Polar Power promises 35% efficiency to electricity (so including half the conversion losses) using a similar Volvo Penta engine. It's not hard to find a PMAC motor that's ~87% efficient or better for most of the operating range...

[seandepagnier]

Originally Posted by GrowleyMonster

Cost? Actually, an electric drive can be put together for a bit over $2k, and even with new off the shelf gear, less than $3k. In other

I managed to get a trolling motor for $20 and a new 10kw/hr bank for $800. A second trolling motor for $50, and I could motor 3 knots.

I killed those batteries a few years ago. Now I have free batteries.

I realized sculling oar is free and better.

And even for a boat under 30', you really need about 2kw of solar to be totally independant of infernal combustio...

?

Nobody sails for free. Cheap maybe, but not free. Boats cost. sails cost. paint costs. rigging costs. Repairs. Replacements. For a SAILED sailboat, fuel costs are modest compared to all the rest. Dreamers, keep that in mind. I just moved a new-to-me 44'

My sails are free. I don't paint. Rigging is free, repairs replacements free.

I must be "nobody"

Cook and heat with diesel,

cook and heat with wood, which is also free.

It turns out everything you need to go cruising is free.