The Shed – September-October 2019

size, but also answers ‘close’; in its case,
close to the generation source or the
distribution grid. Micro-hydro doesn’t need
to block or divert a whole watercourse,
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to continue downstream. Pumped hydro
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separate from natural watercourses.
Micro-hydro has none of the
intermittency of solar or wind, and
pumped storage has the obvious ability
to reduce peak demand. If we are serious
about increasing our use of renewable
energy, both must be on the table, big-time.

What works best for
flow?
For micro purposes, height is more
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propeller into a passing water race,
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the water. The more energy we try
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slow. There comes a point where the

water overtops the banks either side

of our propeller. Height, on the other

hand, only needs a pipe big enough in

diameter to minimize friction losses.

There are tables which tell us how much

power we can get from how many litres

per second at what height, and I have

long wondered whether land with water

dropping through it will become more

desirable because of this potential.

Our micro-hydro originated from the

time we tried to run the house on 50W of

solar photovoltaic (PV). Yes, you read that

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Some evenings we were taking the

batteries down further than was good

for them. We have a spring-fed drain

traversing our property, dropping 25m

in the process. I stuck a 10-litre bucket

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good enough for us.

The Gentle Annie

There are types of turbine optimal for

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great height being the happy hunting

ground for Pelton wheels. Our wheel

(sometimes called a ‘runner’) was low

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I got one that he had directly driven a

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still bolted to it when I spotted it in a

second-hand machinery store. Initially,

we thought that we’d only be able to turn

a tiny motor-turned generator but we

learned that, friction aside, this is not true

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how fast our little baby spins. A techie

friend steered us away from SmartDrive

washing-machine motors and towards

Gentle Annies – a metal-caged GE

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and capable of more output but need

machining.) The advantage of a Gentle

Annie is that the bearings are already f

Above: Micro-hydro intakes need not

interrupt the full run of flow, as this one

does. Note removable gate

Above: Our wheel was low volume–produced

by a fellow in Roxburgh. The half-inch shaft

gives an idea of scale

I like that it was built from recycled materials.
The Gentle Annie motor is housed in a backpack
vacuum-cleaner body

Multiple nozzles on a Pelton wheel, used where there is both good head and good flow.

This is a four-nozzle Harris unit capable of running a modest house