Hubmotor hydro generator

[HrKlev]

I have this creek running through my property. It is only a 60cm (23") head, but it usually flows more than 3000lpm (790 gpm) throughout the year. I know it is not enough to generate a whole lot of power, and its definately not cost effective, but I want to build a water wheel. Mostly because it would be a fun project, and I think water wheels are awesome. I have started to source some info on water wheel designs, but I have an idea about the generator part that I wanted to ask the electric gurus about....

How would a dd hub motor work as a generator? With the slow speed if a water wheel I am looking at a large gear ratio wit at least 2 stages if I was to use a normal generator. With a hub motor I think I can get away with just a single stage, and everything would be slow moving (hopefully low mainenance) with the least amount of moving parts. I was thinking to just feed it into a rectifier bridge, and then into a mppt grid tie inverter.

How stupid of an idea is this?

 

[fechter]

The wheel will probably turn too slow for a direct drive motor to generate efficiently.

Do you know the approximate velocity of the water? Of course this will depend on the width of the stream. Something like a trolling generator might work.

Years ago I had a DIY hydroelectric setup. I had 46 feet of head but not so much volume. Most of the year I was getting around 25w from it. In most locations, you can get more bang for the buck with solar panels.

 

[HrKlev]

There's a 10ft wide concrete dam at the "top" of the head, so I guess the velocity will be the result of how I build the sluice. I will probably build it in concrete in the middle of summer, the creek is usually close to dry a couple of weeks. The wheel will probably be steel. A breast shot or under shot wheel is probably what it will be. I used to play a lot with water wheels as a kid, so that is all experience an knowledge I have... In other words, I have a lot of research to do before the wheel will be built.

I agree about solar panels, and Im actually about to install some, but I just want a water wheel for the fun and challenge. I like the idea of the water wheel rotating 24/7 in the creek producing power, even if it will be just a fraction of the solar panels

I was most curious if a hub motor + rectifier bridge + mppt regulator was a decent idea to explore. I cant find a whole lot of info about the electric parts in such a small, diy hydro generator.

I do have access to a creek 600ft away with 300ft head, but it does not have a lot of flow. I would have to log it this summer to see if it is worth exploring. But that kind of project will be a whole lot more money. Just the cable and getting it into the ground would be a lot of money and time...

 

[fechter]

The undershot wheel is what I was thinking too. You might be able to use a geared hub motor to get a decent rpm but the gears add loss. I tried something like a MPPT circuit but the losses were more than it made up for. It worked better without it. Mine was several hundred feet away and I ran two pairs of 12ga wire on poles/trees which worked out well. Never got eaten by critters.

With a direct drive hub motor running at what I would imagine the speed of the wheel will be, you may only be generating a few volts. Some hub motors have more winding turns than others too, and will generate more at a low speed. You really want it to output a few volts higher than your battery. You also need a rectifier and could make a nice 3 phase setup with a pair of bridge diodes or 6 single diodes. There will be a bit of loss in the diodes too, so use Schottky diodes to minimize this.