Got wind? Got a stream? Then micro wind or hydro power generation might be for you
When Andy Kenworthy was young, his
dream home had a secret underwater
entrance, an attack helicopter parked on the
roof and arcade machines in every room.
These days, kids draw their perfect pad with
a wind turbine on top. But are today’s kids
any more realistic than Andy?
In the right locations, wind
turbines work well in New
Zealand—but there’s a lot
you need to consider if you
want one of your own. First and
foremost, you need wind. You
may get lucky anywhere, but
New Zealand’s most blustery bits
are along the coasts, in mountain
ranges and immediately east of
them, and towards the tops of
ridges and heads of valleys. And,
of course, in Wellington.
If you live in a very windy
area, it’s possible to get up to
a third of your power from a
wind turbine, depending on the
average wind speed and the size
of the system you install.
Wind turbines are generally
best for people in rural areas,
because you need relatively
turbulence-free airflow, which
you only get on a pretty exposed
site. The turbine should also be
within 100 metres of your home,
to avoid power loss from long
cables.
Wind turbines work by
rotating magnets around an
iron core, using an alternator to
generate alternating current. This
is converted to direct current and
sent to a battery storage system,
allowing you to draw power even
when the wind stops blowing.
You’ll need another energy source
to cope with the inevitable lulls.
Photovoltaic panels are often
recommended because they work
best in sunnier weather, which
tends to correspond with less
windy periods.
When working out the pros
and cons of installing a turbine,
remember that the maximum
output figures (also known as
‘rated capacity’) quoted by the
folks selling turbines are based
on an assumed wind speed.
This speed may vary from one
salesperson to another, and wind
on your site will not constantly
blow at that speed. Depending on
the consistency and speed of the
wind, the actual energy output
of your turbine will typically be
somewhere between ten and 40
percent of its rated theoretical
maximum output.
A final word of warning: don’t
be tempted to bolt the turbine
to your house. Without proper
vibration dampening it may
slowly shake the place to bits.
Andy Kenworthy
Getting started
For a couple of hundred
dollars you can check
a site’s potential with a
wind speed meter, or
anemometer, mounted at
the height of the planned
turbine—which will
probably need to be at
least 10 metres high. As
a guide, you need a wind
speed of at least eight
kilometres per hour (two
metres per second) to
start a small wind turbine
rotating, and upwards of 16 kilometres per hour (4.5
metres per second) to make it a viable power source.
To plan with confidence, you need to obtain a
couple of months of data, cross-checked with a
local weather station. Otherwise, you can pay to get
a professional report done. Whitianga-based Good
Energy (www.goodenergy.co.nz) offers six weeks of
constant monitoring for $400 (plus GST and travel
costs). This includes anemometer set-up, datalogging,
a power demand profile and a comprehensive
report and advice. If you choose the company to install
your turbine, the assessment is free.
Getting serious
Before you can proceed, you’ll need building and
resource consents—more difficult in urban areas,
where the hum of the turbine or its visual impact may
upset the neighbours.
You’ll also need savings! Small wind turbines cost
between $10,000 and $15,000 per kilowatt hour of
rated capacity, including the cost of installation, and
seldom come with more than a five-year warranty.
If your property is so windy that you have to
walk at a 45-degree angle, you can get more robust
systems to harness your hurricanes. These may need
more maintenance to cope with the battering, and may
not last as long.
Go with the flow
Is there a stream at the bottom of your garden?
Lucky you! Even better if you can harness your
own hydro power
New Zealanders are smarter
than average when it comes to
harnessing the power of flowing
water. About 70 percent of our
electricity is generated by largescale
hydroelectric facilities—
but hydroelectricity can also be
generated on a small domestic
scale.
However, like a wind turbine,
you can install a micro-hydro
system only if your property is
suitable: you’ll need a stream,
spring or other watercourse
flowing down a slope. At least a
10-metre drop is ideal (enough
to generate a flow of at least
two litres per second), but it is
possible to use a lesser drop if
there is enough water running
down it. From there, the basic
principles are simple: direct
some of the water via a straight
pipe over a turbine to generate
power.
The amount of power you get
will depend on the height of the
drop, the speed of the water flow
and how straight the pipes are.
Some or all of the power can be
stored in batteries.
You’ll need building and
resource consents, as any
alteration to the watercourse
can affect plants, fish and other
wildlife, as well as people
further downstream. Even a
small dam can disrupt water
flow considerably, so the normal
approach is to divert no more
than half of the main water flow.
Getting started
The right set-up could
consistently generate about 12
kilowatt hours a day—or about
one-quarter of a household’s
needs. A Mainland Micro-Hydro
Turbine from Alternative Power
NZ in Nelson costs $5,000, not
including installation, pipes,
cables and batteries. It comes
with a two-year warranty. If you
have a lot of water on a gentler
slope, an Energy Systems and
Design LH 1000 turbine would be
suitable. It costs $6,000.
