That’s because to date there
are no firm international standards
for how small wind turbines are “rated.” Most
grid connected wind turbines are given
a power specification at 10m/s (meters
per second), the equivalent of 22mph
or 19Knots. They do of course produce
more power in stronger wind speeds.
Marlec chooses to rate our wind turbines
at this same standard of 10m/s as we
believe that as the industry matures
a reasonable level such as this one
will be established. Manufacturers
rating points vary and consequently
it is necessary to compare output graphs
across a wide band of windspeeds rather
than accept individual rating figures
for wind turbines.
The real measure
of performance of wind turbines is “accumulated
ampere hours” into a battery
over a given period of time although
this is a difficult measure for manufacturers
to express since the user’s site
for the windcharger will affect overall
performance. Output graphs are usually
an indication of instantaneous peak
power at given wind speeds but in real
conditions the wind is rarely constant,
usually gusting up to 3 or 4 times
the average.
Wind turbines
theoretically can deliver 4 times
the power in twice a given wind speed
so calculating total power generated
using average wind speeds should
be done with some caution. As an
example we will take 10 Knots as
the average wind speed using a Rutland
913 Windcharger:
the Rutland 913 delivers 1.5A @ 10knots,
then we could estimate a daily yield
of 24hrs x 1.5A = 36Ampere hours. However
at the extreme the wind may blow at
20 Knots for 12 hours and be calm for
12hours, showing 10Knots as the average
so the potential power generated can
be quite different, ie at 20 knots
the Rutland 913 delivers 7A, therefore
12hrs x 7A = 84 Ampere hours.
The actual accumulated ampere hours
in reality is somewhere between the
two. The example does however reinforce
the benefits of wind generators that
run freely in low winds maximising
the available power of the more regular
gentle breezes as well as the peaky
gusts.
The wind never blows constantly from
one direction or at a steady wind speed,
it blows in gusts. Most micro wind
turbines are fitted with a free yawing
mechanism and tail fin to direct the
turbine into the wind. Where they differ
is in the type of generator and aerofoil
blades used which greatly affect its
ability to adapt to the changing wind
conditions. An unrivalled feature of
all the Rutland designs is low wind
speed performance. Our high inertia
generators maintain momentum and speed
between gusts of wind, continuing to
generate power where more conventional
designs slow down losing power and
requiring a strong gust of wind to
restart them. This means that overall
a Rutland will generate more power
into a battery bank in a day when compared
to an equally sized or rated turbine
and even in cases of generators of
a higher “rated” capacity
and turbine diameter! See the independent
tests on our news pages and
compare the turbine diameters to see
that you don’t always need a
larger unit to generate the same or
more power!
- We keep it
simple so it’s
reliable
- We use durable materials so it
lasts
- We innovate to deliver
the best efficiency possible
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