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“We only ran the engine for TWO
HOURS to charge batteries while sailing
all the way to Australia (when thick weed
stopped the hydrogenerator)”DieSel geneRaTORS
+ Instant power
+ Can be used at sea or at anchor
+ Diesel is readily available around
the world
+ More efficient than the main engine
+ Available AC power- Noisy – depends on installation
- Exhaust fumes
- Needs regular servicing
- In the World ARC problems with
generators were high on the list of
gear failures - Takes up space
HyDROgeneRaTORS
+ Excellent when sailing, particularly on
long passages- Have to stop the boat to lower
and raise
SOlaR
+ Fit and forget
+ Effective when leaving the boat- Shading reduces efficiency
- Long nights in the Tropics
FUel cell
+ Runs quietly with heat and water the
only waste
+ Simple installation
+ Small amounts of fuel go a long way- Fuel may be difficult to obtain in
some areas
WinD geneR aTORS
+ 24-hour power in breeze
+ Great in tradewind
anchorages- Gives limited power
when running
downwind - Needs to be
mounted above
head height
Wind turbines and
solar panels can
provide renewable
power at anchorfor AND AgAiNst
›
Ashley Cooper/AlamyPaul WyethTor Johnson81engine for propulsion. We also wanted to use
renewable sources as much as possible and to
reduce our reliance on diesel.
The relationship between amps, volts, and
watts is well documented (a great book on
the topic is The Boat Electrics Bible by Andy
Johnson) and it is easy to work out what
expected consumption will be. We needed to
take into account that the ambient temperature
is much higher in the Tropics so fridges and
freezers would have to work much harder to
keep cold and the fridge would be used a lot
more. Charter skippers often complain that
guests are always opening the fridge door –
each time cold air is replaced by warm. It’s also
dark close to 50 per cent of the time, so lighting
will be on for longer. Water consumption will be
up and, for the lucky few, so is ice consumption.
While we are sailing we have the additional
power consumption of chartplotters, computer
screens, instruments, and nav lights. As radar
is great for squall avoidance it is also often on.
With the autopilot often working overtime we
can easily be consuming over 20 amps before
running a watermaker.
When adding all this together we generally
underestimate consumption and therefore the
size of battery banks needed and the energy
required to charge them.
There is a lot that we can do to reduce
consumption: we can change bulbs to LEDs;
turn unused screens down or off; spend time
hand steering; and be careful using the fridge.
But even being as parsimonious as possible,
modern cruising still requires a significant
amount of power.
Before we headed off we attempted to
estimate our consumption, what battery
capacity would be necessary and how we would
recharge the batteries. After our electrical
audit we estimated that we would consume