Re: micro hydro load controller

On Tue, 03 Oct 2006 07:20:12 -0700, kell wrote:


andy baxter wrote:
Hello,

I'm volunteering at a place out in the country who are living off the
grid. They already have a couple of windmills, which have been installed
professionally. They are also working on a micro hydro system. This has
been designed and partly built by a professional engineer during his spare
time, but he has been unable to do any more work on it for some time (at
least a year) due to other commitments. The turbine and alternator are
finished, but none of the rest of the electrics, including the charge
controller for the batteries (it's going to be a DC system with an
inverter).

They have just got hold of a battery backup system of the kind which is
used to supply emergency power to alarm systems, emergency lighting etc.
(I think it used to run the emergency lighting for a nursing home). This
is designed to charge some 12V batteries from the 240V mains, and there is
also a separate inverter which supplies mains power from the batteries.

I was talking to one of the people there, and he was talking about using
the battery backup system as a charge controller for the water turbine. I
was advising him to be cautious, for the following reasons:

- you need to have some way of shunting power to a dump load when the
batteries are fully charged and no current is being drawn, otherwise the
alternator may burn out.

- The charger is as far as can tell (I may be wrong here though)
a standard linear regulator, which I am not sure is suitable for this kind
of application where the input voltage may be variable. I would have
thought that a switch mode regulator would be more suitable, as these can
deal with a wider range of input voltages. I think this is not so much an
issue as with wind power, since the speed of the turbine and hence the
output voltage is probably fairly constant, so should be tunable to
whatever voltage is required.

Do either of these things matter as much as I thought, or am I being too
cautious?

Any advice appreciated, particularly from anyone who has any practical
experience with micro hydro or windpower electrics.

--
remove 'n-u-l-l' to email me.

Best place for advice on this stuff:
www.fieldlines.com

Thanks - I've reposted this there.

My thought: hydro might not need a dump load because you don't have to
worry about the hydro overspinning and destroying itself the way a
windmill would. But take the foregoing with a grain of salt and get
some advice from the more experienced.

I'm also not sure why people say you need a dump load. What I'm thinking
is if you have an alternator which generates its own power for the field
coils, then if it overspins the voltage on these coils could rise too
high, increasing the current to the point where they burn out. Is that the
problem or is it something else (mechanical failure?)

--
remove 'n-u-l-l' to email me.

.

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