Dear Diary..
I wonder if this would be better placed in the Hydro section, Wind, or maybe the Pub.
This would be installed in a river.
Been kicking the idea of a Hydro VAWT, but haven't a clue where to start in the blade profile.
The location would take a turbine about 40 in (maybe 50in) diameter and it's height is still open to debate.
Currently I'm thinking that the blades would be tall enough to take advantage of the river at it's "normal" max height/depth (about five feet). The river flow "I'm guessing" is about 8mph.
I know that this doesn't sound like much (if I was talking about air) but anyone standing in water current moving at 6mph and five feet deep would appreciate just how much energy is there (not to mention a 40x60in cross sectional area).
Now, maybe 40% of it's operational time (I'll have to yank it out in the winter months) the water level will moderate, and drop to a depth of about three feet (now a cross sectional area of 40x36in.) and the flow would slow down to about 6mph (still a lot of energy)
Blade profiles are over my head (and to date, not an interest of mine). I don't want to admit that I'm too lazy to "do the research and do the math", so with all this I've got a couple of questions I hope someone help me with.
1. Is there a relationship between a vawts height vs Width?
2. Is there a relationship between the number of vanes and it's rotational speed?
3. Since the river current will all ways be flowing from the same direction, would that effect blade profile?
4. Since the change of flow rate (mph) from max to min (drought to flood) would be only a few miles per hour
would this change the ideal profile?
5. Would the density difference of water vs air effect the vane profile and number?
6. What am I forgetting to ask?
Yes, I know I've made no mention of an alternator, or a gear box. There's plenty of time for that. Maybe a right angle gearbox on top of it, and the drive shaft running to shore and alternator.
I envision this VAHT being "up side down" where it's bottom bearing would be anchored on the river bottom. it's top bearing (and genny) would be supported by supports from shore. For now, thinking the bearings would be UHMW or a plastic to be determined. The center (drive) shaft will be made from a 1 1/4in di bronze pipe salvaged from a air cylinder.
In the past I was thinking of a large diameter water/paddle wheel floating on pontoons. But I've had visions of finding a kid wrapped around it.
A vaht would be easier to "kid proof".
yes/no?
ax7
Mark