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Old 19-04-2014, 23:50   #16
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Re: The all electric sailboat.

Newt,

Maybe JackB knows, this is about all I know. KiteShip - Pleasure Marine
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Old 19-04-2014, 23:56   #17
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Re: The all electric sailboat.

It is certainly possible but at the cost of motoring range. It really all comes down to the energy density of batteries compared to diesel fuel. So long as you are willing to accept the limitations that come with this system there is nothing technologically impossible in the deal.

Here is the problem however... FLA have roughly 1/50th the energy density by weight of diesel fuel. So whatever weight of diesel we would need for a trip we will need about 50 times the weight in batteries to achieve the same trip.

On my boat we burn about .5gallons/hr at 5-6kn, so if I want to motor 100 miles I need to carry around 9 gallons of diesel. To make this same trip with just batteries supplying the power would require 2,700lbs of batteries.

As for regeneration... Let's assume we have two wind generators that put out 1kw each, and another 1kw of solar power and that the wind generators put out this power 24hrs/day and the solar panels are operating 12hr/day. This means the boat is regenerating 60kw/day of power.

The problem is we burned 20kw/hr (engine draw) * 20 hours (run time) = 400kw to go 100miles.

Since we generate 60kw/day and need to resupply 400kw it will take us 6.66 days to reach full power.


I just don't think it is reasonable to be limited to one 100 mile cruise a week. And frankly these numbers are incredibly optimistic in favor of the electric boat. Real life would be substantially less.



As always when it comes to me and electricity I recommend someone else redo my math. I am terrible when it comes to electrical conversions.
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Old 20-04-2014, 00:08   #18
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Re: The all electric sailboat.

Greg,

The numbers I have seen is at a pace of 5 kt, a light displacement cat only consumes 500 w-hr per mile, so 10 kw of solar panels with 6 hours of full output exposure should propel you 120 miles per day, not bad in my book. LiFePO4 cells will store enough energy for 24/7 without the weight penalty you referenced. Battery weight would be under 1000 lbs for cells with a low energy density of 80 w-hr per kg.
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Old 20-04-2014, 00:16   #19
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Re: The all electric sailboat.

I can make fuel from seawater and can go 1000000 miles without ever going to a fill station (oh, btw, how far can you go if the diesel filling station is closed?)
Didn't anyone catch that thread???

There are actually ways to store solar energy besides batteries.
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Old 20-04-2014, 00:25   #20
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Re: The all electric sailboat.

Even if I could go totally electrical, I would not want to do it on a round the world cruising yacht. I have four solar panels and two wind generators, and I still find that I need to run the engines to generate electricity unless I turn off refrigeration, water maker, fans, lights, autopilot, radar, and electronics usage.

I can sit in the trade winds at anchor and generate sufficient electricity for everything. But when the wind stops blowing, I either have to turn lots of stuff off or run an engine.

The thought of generating enough electricity for propulsion would not be possible without major lifestyle changes on board Exit Only.
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Old 20-04-2014, 00:25   #21
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Re: The all electric sailboat.

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Originally Posted by deckofficer View Post
Newt,

How about no sails, Atlantic crossing speed of 5.5 kt average?
transatlantic21: Boat
Cool. How do you reef all those solar panels.?
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Old 20-04-2014, 00:58   #22
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Re: The all electric sailboat.

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Greg,

The numbers I have seen is at a pace of 5 kt, a light displacement cat only consumes 500 w-hr per mile, so 10 kw of solar panels with 6 hours of full output exposure should propel you 120 miles per day, not bad in my book. LiFePO4 cells will store enough energy for 24/7 without the weight penalty you referenced. Battery weight would be under 1000 lbs for cells with a low energy density of 80 w-hr per kg.
What size boat? 500 watts is .6hp.

On my Olson 30 with a 1kw electric motor (30' long 3,600lbs) i could get to about 3kn on a dead calm day so long as I had no crew, no sails, and no drinks... Race ready the boat could hit 2.5kn. I to a stiff breaze we asked for a tow.

1000w=1.34 hp. So a 10kw solar array will give you the same available power as a 13hp engine at max output. Realistically let's say a 10kw solar array produces power for 1/3 the day, so you have a combined 80kw to burn. Assuming you want to run for 24 hours you can output a max of 3.33kw/hr, or 4hp. Note that this assumes a perfectly efficient charging system and electric motor, more realistic numbers probably look more like 3hp.


I just did some quick research, and that 10kw array is going to cost $20,000 plus installation... The panels alone weigh 2,000lbs, and take up 762 square feet. On our hypothetical 40' cruiser this means the solar array will be 40' long and 19' wide. Plus whatever framing is necessary to mount all the panels.

The upside is all the batteries get to be treated as ballast weight.
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Old 20-04-2014, 04:12   #23
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Re: The all electric sailboat.

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Originally Posted by Stumble View Post
What size boat? 500 watts is .6hp.

On my Olson 30 with a 1kw electric motor (30' long 3,600lbs) i could get to about 3kn on a dead calm day so long as I had no crew, no sails, and no drinks... Race ready the boat could hit 2.5kn. I to a stiff breaze we asked for a tow.

1000w=1.34 hp. So a 10kw solar array will give you the same available power as a 13hp engine at max output. Realistically let's say a 10kw solar array produces power for 1/3 the day, so you have a combined 80kw to burn. Assuming you want to run for 24 hours you can output a max of 3.33kw/hr, or 4hp. Note that this assumes a perfectly efficient charging system and electric motor, more realistic numbers probably look more like 3hp.


I just did some quick research, and that 10kw array is going to cost $20,000 plus installation... The panels alone weigh 2,000lbs, and take up 762 square feet. On our hypothetical 40' cruiser this means the solar array will be 40' long and 19' wide. Plus whatever framing is necessary to mount all the panels.

The upside is all the batteries get to be treated as ballast weight.
You're comparing watt/hours with watts -- apples to oranges, or -- like comparing miles per hour to miles.

500 watt/hours per mile at 5 watts is 2.5kW/hours per hour or 2.5kW, to get it back to apples to apples.

2.5kW is 3.4 horsepower. Can a light cruising cat be propelled at 5 knots with only 3.4 horsepower? Something like a Catana 40 comes with something like 60 horsepower of installed power.
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Old 20-04-2014, 09:18   #24
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Re: The all Electric Sailboat.

When you guys see these solar farms on a boat, I envision electricity coming from 3 sources, wind, water, and solar. I think solar is probably the least efficient. Moving water is probably the most efficient (although I don't know for sure) and wind is somewhere in between.
The least taken advantage of in our anchorage or travels is the energy densitiy that water has. Could a large prop (say foot in diameter) be placed down in the water at anchor that could make watts from the tide? Smaller props could both provide propulsion and charge batteries at sailing speeds.
I still want to know if anyone is using a "kite" 3-500 feet up in the air to sail downwind. That would be cool technology.
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Old 20-04-2014, 09:39   #25
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Re: The all Electric Sailboat.

Newt, that tech is being trialled by some cargo ships. More of a booster than a sole propulsion source http://en.m.wikipedia.org/wiki/SkySails
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Old 20-04-2014, 09:52   #26
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Re: The all Electric Sailboat.

My boat will have an engine, it is too expensive to have enough batteries and they also add a lot of weight, and a backup is also important. My goal is a practical simple boat, not a fundamentalist eco-religion.
That said, running the engine will be a small fraction of noise,pollution,fuel that other boats would use even in the worst case. A big key is having a very lightweight boat, which is why I obsess about weight. My inspiration was the planetsolar boat, but not with the millions of dollars.

Planet Solar


Regarding tide energy, there is something to be gained, depends a lot of where you are, but solar panels are just a lot more simple and effective, particular where I plan to be in Baja, where the solar energy concentration is some of the highest in the world.
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Old 20-04-2014, 10:11   #27
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Re: The all Electric Sailboat.

There was a kite maker for cruisers, but all the links to them have gone cold. I wonder what happened?
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Old 20-04-2014, 13:22   #28
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Re: The all electric sailboat.

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What stopped his voyage John? Bob- love it, but I just can't do without the sails!
Mauricio and Paola set off twice and got turned back by contrary winds and beating into seas. Both are good sailors and were physically doing ok but didn't want to continue beating themselves up and each told the other they were not having fun so decided to return to Hawaii. They sold their boat in Honokahau a year or so ago. All electric. I don't have specifics on watts and amps and stuff because when I hear it I don't pay attention since I'm not an electric guy.

There is another thread here on the forum a couple years ago on electric power and I know there were quite a few discussions. It might be worth a search.
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Old 20-04-2014, 14:03   #29
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Re: The all Electric Sailboat.

Dockhead,

This is why I never trust my numbers when playing with electricity, all the conversions go to pot in my head.


As for tidal regeneration... The commercial units that are capable of doing this have a start up speed of 2kn, so the boat has to be anchored somewhere I would rather not be in the first place. But assuming you are ok with looking for high speed tidal flows as a place to anchor.

These are the power productions...
2kn - 5watts
3kn - 20 watts
4kn - 50 watts
5kn - 80 watts

I can't imagine being willing to anchor in a place wi more than 5kn of current, so that's as far as I am going. At more realistic current speeds of 2kn, I doubt the power generated will be enough to matter much.
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Old 20-04-2014, 14:34   #30
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PLEASE don't use a slash to signify multiplication.

............ PLEASE don't use a slash to signify multiplication...........

Dockhead's right, as you've acknowledged, Stumble, about the risks of fudging the units. You are confusing a unit of energy storage with one of energy intensity.

The former is a measure of how much work can be done, the latter is a measure of how FAST work can be done.

But even Dockhead's formulation preserves one of the problems from yours, when he writes watt/hrs.

There is NO such unit in general use. The / sign means exactly one thing: it means the unit before the sign is DIVIDED by the unit after the sign.

So watt/hrs (even if more plausibly written watts/hr) means watts per hour.

This is a nonsense unit: a 1 bar heater consumes a thousand watts, regardless of the time period. The only possible meaning of 'watts per hour' would be if the heater's consumption of power was increasing or decreasing by a constant rate, so that in an hour it might be consuming 1005 watts, and in two hours, 1010 watts.

In this very strange case, the rate of change of power consumption would indeed be 5 watts/hr. (NOT watt/hours)

- - - - - -

What you really mean, when talking of energy STORAGE, is watt.hrs, watt hours, or if you want to spell it out: watts x hours, or watts X hours.

............ PLEASE don't use a slash to signify multiplication...........


End of sermon. Sorry about the interruption.

Oh, and I nearly forgot:

............ PLEASE don't use a slash to signify multiplication ! ! ! ! ! ...........
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