As prelude to my remarks I offer this quote from my favorite president, Abraham Lincoln, who said in his Gettysburg address:
"The world will little note, nor long remember what we say here"
I think that's a good thing...maybe.
I just started reading this thread and I am, as always in these cases, amazed at the amount of information and disinformation presented. For you guys who don't understand torque, try this. Take an old washing
and hold the shaft as tight as you can. Have your wife plug
it in and try to keep it at 0 RPM
. Let me know what happens. It's not for nothing that the Tesla sports car is one of the fastest cars in the world.
Anyway, that said, electric drives are extremely well developed and have been for over a century. Railroad locomotives, both electric and diesel-electric, have been operating for many decades. Some of the first cars were electrics. Because of environmental issues there are electric boats operating on some lakes in Germany
that go all day on a charge. Need I mention submarines? Does electric propulsion work? Of course it does. Does it have all the advantages its proponents claim? Of course it does. There are only two important questions about electric propulsion. First, where do you get the electricity and second, where do you keep it?
Let's answer the second question first. In the context of this discussion, we first need to define how much electricity we're talking about. Based on the numbers offered by EAS about his 48v electric system:
Estimated speed/power numbers. The boat will motor at 2-3Knots (10Amp draw) 3-4Knots (20amp draw) 4-5knots (35A) 5-6 knots (50A) 7knot hull speed (75A)
Assuming 5-6 knots cruise, we can now estimate required daily power consumption
for this boat as follows:
50A x 48V x 24 hours = 57,600 Watt-hours or 57.6 KWH required to cruise continuously for 24 hours.
That's 48 100 amp hour 12v batteries (57600 Watt Hours/12V = 4800 Amp Hours, 4800AH/100 AH per battery = 48 batteries). Of course, that's pure electric and you can use fewer if you want less time under power. For 1 hour, divide all numbers by 24. 1 hour, 2 batteries.
Now, where do you get it. First solar
. If you use a 240W panel mentioned by KEALOHA, that's 10 panels
operating continuously, 24 hours, at full output. Do solar panels
work in the dark? No? Make that 20 or 30 panels
. Maybe more on a cloudy day. Wind
? If you've got wind
you don't need the motor. Regeneration? Certainly extends range but unless you've got a generator
that makes more than it uses, that begs the question of where you get the power from if you're out of it for whatever reason. You're that long distance cruiser operating out of sight of land for days or weeks? I guess that leaves out stopping at a marina. Oh, you're coastal hopping? Well, I think a marina might look at you in a funny
way if you asked for a connection big enough to recharge all those batteries overnight. Well, I guess that takes us back to an on board generator
, which is what we were trying to avoid in the first place.
So, in the end, it boils down to what you want to do. Going in and out of harbor? Absolutely doable. Long distance cruising with lots of time to recharge and limited range? Certainly, if you willing to risk a few days sitting still while your solar panels
do their thing. Your wind generator
and regeneration system, of course, don't work if you have no wind and aren't moving.
Until someone comes up with a revolution in charging
systems and batteries I'm afraid most of us just aren't candidates. I saw a lot of the US electric car programs from the inside and you wouldn't believe what they have tried to make lightweight, high power batteries. Would you believe liquid sodium at 500 degrees F? I don't want to take that one through a car wash. How about bromine? Yeah, that's right, a first cousin to that poison gas, chlorine. Batteries just aren't there just yet. Jay Leno has a 1909 Baker Electric car in his collection. Here's what he says:
"I'm not too bullish on electric cars as the way of the future. Modern electric cars go roughly 100 miles on a charge, about the same as my Baker; so I don't see much progress there. I think electricity is a great power source for a car. But the problem is, how do you get it?
Thomas Edison invented the alkaline battery. My Baker still has some original alkaline batteries. These have lead plates and use acid; we wash them out and refill them regularly and I'll use them indefinitely. But even Edison realized the future of the automobile was elsewhere. Legend has it that back in 1896, at a dinner party, he passed a note to his friend Henry Ford. Essentially it said, "The electric car (boat?) is dead."
How prophetic was that?"
Personally, I've gone down the ICW
several times in my 41' sailboat and, sad but true, most of it was under power. Unless you can tell me how to put 8 to 10 hours "in the tank" overnight, electric just doesn't work for me. It's got nothing to do with electric. I love the idea but, like electric cars, the practical applications, like commuter cars, are limited and the disadvantages too great for most of us. I don't relish the idea of calling the boss on a Sunday night to tell him (or her) I can't make it to work because I'm sitting offshore
in a dead calm with no motor. Oh, wait! I'm retired. Screw the boss. Where can I get one of those electric thingies?