----- Original Message -----
From: Joseph Hartvigsen<mailto:[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>
Sent: Tuesday, August 17, 2004 1:57 PM
Subject: [microhydro] Re: Aquair Submersible Generator
Some time ago I briefly looked into the Aquair online and came away
with the impression that it seemed rather expensive.
An axiom applicable to any fluid power scheme is that the lower the
head (pressure or velocity), the larger and more costly the turbine
for a given power output. Free stream turbines are for the lowest of
the low head sites, so the fact that they are costly is no surprise.
Still, the lack of pipe and civil works does offset the higher turbine
cost to some degree.
Free stream propeller turbines are not something that I have any
experience with. However, I wonder if it might be possible to
reconfigure an electric trolling motor for such an application. These
are mass produced, and available at a fairly low cost. They have a
submersible permanent magent motor with thrust bearings. Many have a
solid state "throttle" control that is probably a simple chopper
circuit that could be "turned around" so that the input is the
motor/generator and the output is the battery in order to control the
turbine speed to optimize power production. The catch is probably the
propeller which will have the wrong curvature for turbine ues, and
will likely be too small. It will still work at a reduced efficiency I
suppose, but a propeller shop should be able to make a custom prop.
I don't know, maybe such generators exist for the sailboat market. A
little drag on a sail boat to keep the batteries charged up would seem
like a fair trade unless you were racing.
A quick check of the web shows electric trolling motors from ~ $100 to
over $3000. So it shouldn't be hard for someone with a suitable site
to try out this idea.
Any thoughts from the group?
Joe
It seems Aquair makes towable generators for boats also. See this site:
As you can imagine, the prices for these items have not become lower for the
Yacht people...
http://www.jackrabbitmarine.com/(bspjspfw4qkh4oulgx25ni55)/productDetail.aspx?loc=146&pID=49&type=0<http://www.jackrabbitmarine.com/(bspjspfw4qkh4oulgx25ni55)/productDetail.aspx?loc=146&pID=49&type=0>
The problem with any use of a propeller is the basic cost of designing and
building the thing. To make a big one cost big money. I get around that by making my
paddles flat, but REALLY BIG. It is easy to go big when it is flat. I foresee my
wheels using 60% to 90% of the area of the river, depending on whether the river is
also used for boat traffic, and composition of the river banks.
-Dennis
[Non-text portions of this message have been removed]
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