practicalpractical
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Want a TV? Specifications range from
13-40W depending on size (and age) so,
although they’re a luxury, they’re not too
power-hungry at 1-3 ampsSolar panels are
often limited by the
amount of area out of
the shade, especially
without adding
guardrail panels
or a separate hard
structure to
the yacht‘using renewables gave quiet
and remarkably reliable energy’
Chris and
Helen Tibbs’s
Centurion 40S,
TaistealaiPaul WyethPaul Wyethbetween 10 and 15 amps per hour. Using the
lower figure this meant 240Ah (amp hours) and,
because we would try not to discharge them
by more than 50 per cent, would push up our
calculated capacity requirements to 360Ah.
Then we had to adjust this for reality: a
standard alternator will only charge to about
80 per cent of battery capacity, increasing our
requirements to 460Ah (360/.8). Then a further
10 per cent needed adding as the batteries age
and become less efficient, pushing the figure to
506Ah. So, for our lower figure of consumption
when sailing, a theoretical domestic battery
bank of around 500Ah was required.
Sometimes theory and reality clash –
changing batteries proved rather more
complicated than expected and we ended up
with only 420Ah. To have increased the number
of batteries or changed to AGM (Absorbent
Glass Matt) or gel would have required a
considerable amount of carpentry and, in
addition to the expense of the batteries, was
pushing the budget. So we knew our capacity
was on the low side before we left. So what was
the best way of keeping them charged?
As our yacht, Taistealai, (Gaelic for traveller)
normally lives on a river we had already fitted
150W of solar panels to keep the batteries full
and avoid the need to row out every couple of
weeks to run the engine. This was split between
the domestic and start battery and worked well.
Our next consideration was whether to fit
a diesel generator or not. The advantages are
that at a flick of a switch we would have power,
which through a modern smart charger would
boost the batteries as well as giving AC power.
Watermakers can be AC or DC – the AC models
tend to have greater production but depend on
a working generator or large inverter.
Our boat had no convenient place for a
generator and we did not want to be dependent
on diesel, so it was an easy decision not to
install one. Our choices then were wind, hydro,
solar, or fuel cell.Having used a fuel cell to great effect in the
AZAB [the Azores and Back] a few years ago we
gave it serious consideration. They are almost
fit and forget; when racing we used about 1lt
per day of ethanol so cruising would be a bit
higher, say 25-30lt for a transatlantic passage.
However, we felt that although the fuel was
becoming more readily available, when crossing
the Pacific it could become more difficult to
find. This narrowed our choices to hydro, solar,
and wind.
Solar panels are now found on most cruising
yachts and vary hugely in quality and price. The
main limitations are in available space where
they can be mounted without being in shade.We added an extra 80W on the coachroof in the
Caribbean, which was the maximum possible
without adding large structures to the boat.
Many years ago I delivered a yacht across
the Atlantic with a towed hydrogenerator (a
propeller on a long rope). At moderate speeds
it worked well but too fast and it leapt out of the
water, so it had rather put me off. However, the
new style hydrogenerators, which look like an
outboard motor fastened to the transom, had
good reviews.We fitted a Watt & Sea, which provided an
abundance of power whenever we were sailing.
In the tradewinds when we were sailing quickly
(over 7 knots) we found that we only had to use
it about 60 per cent of the time to fully charge
the batteries. This was the case even when
using the small propeller.
Wind was the final piece of the jigsaw for
us; although rather less efficient when sailing
downwind it comes into its own when reaching
or in tradewind anchorages when sheltered
from the sea behind a reef. The wind generator
really kicked in at between 10-15 knots and
combined with the solar panels it met all our
needs, including running the watermaker, in
many island and atoll anchorages.
The older wind generators can
be noisy but the newer designs
are much quieter. The only
time we resorted to running the
engine to generate electricity was in sheltered
anchorages when it was cloudy or raining.
This was our weakness and something that we
had not thought through fully. In hindsight we
should have fitted a smart charging system
to get more out of the main engine alternator
and replaced the splitting diodes, which tend
to lose about 1V from the alternator, to more
sophisticated automatic switches.
On larger boats with a need for AC power,
diesel generators make sense and some are
remarkably quiet. Regular maintenance and
soft starts (not fully loading them at start-up) is
said to be key for reliability.
Having the ability to charge from multiple
sources adds redundancy to the system and
covered us whether sailing or when at anchor.
Using renewables gave quiet and remarkably
reliable energy and on smaller boats with
limited fuel carrying capacity it removes the
need to carry extra cans of fuel. Perhaps we
went a little over the top with wind, water, and
solar power, but in hindsight it is hard to know
which to ditch.