Hydroelectric Generator

[hellosailor]

In my limited knowledge, MPPT is only of use with solar panels, not alternators. So there's no advantage to using MPPT for a hydro generator. Although, if you stick to the classic (and arguable) split that a generator is pure DC, and an alternator is really rectified AC, with an alternator you might use PWM, which is more efficient than pure DC for wet lead battery charging. Or just tap the alternator output as PWM from the start.

[KISS]

Originally Posted by hellosailor

In my limited knowledge, MPPT is only of use with solar panels, not alternators. So there's no advantage to using MPPT for a hydro generator. Although, if you stick to the classic (and arguable) split that a generator is pure DC, and an alternator is really rectified AC, with an alternator you might use PWM, which is more efficient than pure DC for wet lead battery charging. Or just tap the alternator output as PWM from the start.

The alternator I mentioned is unregulated, so it can reach very high voltages. Isn't an MPPT more efficient whenever voltage exceeds what the batteries can accept? ...my knowledge of this is limited as well, so maybe I'm mixed up.

[dlymn]

feeding unregulated voltage into your batteries might do harm. Charge controller include reverse flow diodes and overvoltage cutouts. Generators will-do little charging until the charge voltage exceeds the nominal voltage of the battery at the time of charging. this means that you need a system operating at 13-15 volts very often. Most controllers stop charging at 14.4 volts. Most then start braking the generator and you don't want that. So, you need to use a charge controller, but it needs to be a special one.

[roverhi]

A prop big enough to generate electricity will have to be a big one for a smallish boat. When you are not generating power will still have the drag of that oversize prop. Best to hang it off the stern and deploy when you want it. Don't know how you's build the the system but wouldn't use the prop shaft to turn the generator. unless it's on a large sailboat already equipped with a large prop.

[Bleemus]

Originally Posted by john61ct

One of us is confused.

Generating power in a static location from naturally flowing water, tidal flows, wave motion, OK.

But trying to capture energy from movement powered by dino juice is forgive me a fools errand.

Like spinning a wind gennie by running a powerboat, the power lost to wind resistance is **much** greater than what you'd be trying to (re)capture.

Or am I misunderstanding?

The shaft spins when your sailing without a folding prop.

[Bleemus]

Originally Posted by Guy

What proof do you have that these boats with alternators on their drive shafts make power? What about Entropy?

Sailed across the Pacific on a 67 foot Jongert with one. It worked.

[KISS]

Regarding drag, perhaps you could use a folding prop...

They folds when not rotating, right?

So, if you braked the shaft when not in use, the prop would fold?

[Bleemus]

Originally Posted by KISS

Regarding drag, perhaps you could use a folding prop...

They folds when not rotating, right?

So, if you braked the shaft when not in use, the prop would fold?

They fold when not being spun by a diesel. Unusable for this application.

[KISS]

Originally Posted by Bleemus

They fold when not being spun by a diesel. Unusable for this application.

IOW, the flow of the water wouldn't be enough to open them? That's unfortunate. I don't suppose there's any prop out there that can be folded manually from inside the boat?

[Lepke]

You'll need a big prop, probably 4 or 5 blade and the power you take out of the shaft will reduce your speed, possibly by a couple knots. Then if your plan is to spin the prop with an electric motor when you need an engine, you'll need one big electric motor.

[Bleemus]

Originally Posted by KISS

IOW, the flow of the water wouldn't be enough to open them? That's unfortunate. I don't suppose there's any prop out there that can be folded manually from inside the boat?

The idea of a folding prop is the flow of the water closes them to reduce drag while sailing. To run an alternator off the shaft you need a non folding prop.

There is one you can manual furl from inside the boat. Hundested made in Denmark. Had one on a boat I worked on for years. Wonderful piece of gear.

[Bleemus]

Originally Posted by Lepke

You'll need a big prop, probably 4 or 5 blade and the power you take out of the shaft will reduce your speed, possibly by a couple knots. Then if your plan is to spin the prop with an electric motor when you need an engine, you'll need one big electric motor.

Not really. Had one on a three bladed prop and when we engaged the alternator on its cam mount the speed difference was not noticeable. It was a 67 foot steel boat though. Lots of grunt under sail.

[Kenomac]

Then why not just get a few solar panels?

[hellosailor]

Kiss-
The normal force of water rushing past a prop, which is what you need to turn a water generator, is exactly what folds a folding prop. They ain't spring-loaded.
Now if you had gobs of money, you could buy a feathering prop. Like expensive aircraft engines, you can actually throw a lever which throws some expensive machinery in the propshaft and actually turns the prop blades to get more or less angle of attack from them. Feathering them when you want them to just create "zero" drag. Has been used on boats, ain't cheap.

When you talk about unregulated alternator and needing to reduce voltage, that would be a "buck boost" aka "buck" invertor, that reduces source voltage and provides lower voltage at the output. There are such devices although you might need to custom build one for your power requirements. MPPT controllers are intended to read the load and read the maximum power point of a solar panel (maximum current for that load, regardless of voltage and amperage) and adjust the output voltage, high or low, to optimize charging. They'd do the job, but I'm not sure they'd be the best way to get it done. A simpler regulator should be less expensive and just as effective, for an alternator.

If it was easy, or cost effective, I think it would have been done by now. Like solar panels.(G)

[john61ct]

There are hybrid wind/solar/hydro controllers designed to handle whatever the source may be.