Before I set sail, I read everything I could find on optimizing the
electrical system on board our Privilege 39 catamaran, Exit Only.
Much of what I read, and almost everything that sales people told me wasn't
right for my boat. They were always quoting the power output from
their diesel generator or the power produced by their high output
I discovered that it was easy to produce tons of electricity at great
expense, but there was always a problem. The acceptance rate of charge
by my battery banks was limited. Even if I could generate a megawatt
of electricity, it didn't matter because my batteries couldn't accept all
Diesel generators and high output alternators work well for the first
fifteen minutes of the charging cycle when the batteries can accept bulk
charge. But after that, they burned up a large amount of fuel and
produced only a small output during a rapidly tapering three stage charge
cycle. High output devices were not an economical way of charging my
I figured out that the acceptance rate of my batteries was the rate limiting
step in the discharge/recharge cycle. I need a source of current that
would charge my batteries at a rate that they could accept.
Two options provided the continuous charge that I needed.
Solar panels and Aerogen 6 wind generators could do what I wanted.
In the tropics, my four 75 watt solar panels provided an estimated fifty
amp-hours of current each day. Even more important, the acceptance
rate of the batteries meant that almost all of the current would go into the
My Aerogen wind generators provided a second source of continuous low level
current output, and the majority of the time the batteries could accept the
full output of the wind generators. When I cruised in the trade winds,
each Aerogen produced ten amps of current in twenty knots
of wind. When the trades were blowing hard, I had more than 400
amp-hours of current available every twenty four hours from the wind
generators. That provided plenty of electricity to run refrigeration,
lights, computers, watermaker, and autopilot.
I installed my first Aerogen when I was in New Caledonia to see how good
it would work. Much to my surprise, I went for three weeks without
having to turn on my engines to charge the batteries. That was
impressive. Shortly after that, I installed a second Aerogen when I
decided to complete our circumnavigation with four adult electrical
consumers on board Exit Only.
The Aerogens did a great job of keeping our batteries charged while sailing
offshore. We had plenty of power for the autopilot, refrigeration,
lights, radios, and computers as long as the trade winds continued to blow.
There is a zirc fitting on the casing of the Aerogen, and every couple of
months it's a good idea to inject grease into the zirc fitting to lubricate
the bearing on the front of the wind generator. The grease also acts
to exclude water from the inner workings of the wind generator.
Dump resistors are supplied with each Aerogen wind generator. If the
generators produce too much output, the current is shunted into dump
resistors which dissipate the excess energy as heat. You can tell when
this is happening because the dump resistors make a high pitch tone that
tell you current is being shunted and dissipated. Alternatively, you
can use the excess energy to power the heating element in a DC powered water
heater, and you can take a hot shower.
Feathering the Aerogen
Sometimes it's desirable to shut down the wind generators. The
manufacturer says that in winds greater than 40 knots, you should feather
the generator to keep it from spinning too fast. This is done simply
by turning the generator out of the wind. We have a small
rope tied to the vane on the back of the Aerogen, and by simply pulling on
that rope, we can feather the generator and even stop it from spinning.
Wind Generator Noise
The Aerogens are exceptionally quiet. There's no high pitch whine
created by the spinning blades. It's one of the quietest wind
Two Aerogen Wind Generators
Two wind generators create massive redundancy in your boats electrical power
generation system. When you have large electrical demands, you run
both generators simultaneously. When demands are less, you simply
feather one generator to save wear and tear on that Aerogen. We often
ran the starboard generator for twelve hours and then switched over to the
port one for twelve hours when the trades were blowing hard.
Having two wind generators means that if one generator malfunctions,
you have a second one up and ready to go.
Relative Wind Direction and Speed.
Having the Aerogens mounted on the stern provides a continual reference
the helmsperson to gage the relative wind speed and direction. If there's a
wind shift, it will show up in the orientation of the wind generator.
And if the wind pipes up, you'll see the generator spinning faster.
SHOULD YOU GET WIND GENERATORS ?
I sailed halfway around the world without wind generators, and I survived
without a problem. I was always rationing power, and I ran my engines
every day to generate electricity. During the last half of the trip
around the world, I had two wind generators working around the clock to meet
our electrical demands. I no longer had to ration power, and I didn't
need to run my engines to generate electrical power except on rare
occasions. That meant less wear and tear on the engines, a quieter
boat, and I didn't have to endure the smell of diesel exhaust.
Wind generators worked for me because I circumnavigated in
the trade winds. Most of the time the trades were blowing hard, and I
had electricity to spare.
If you aren't a trade wind sailor, then a wind generator may not be for you.
You need predictable and reliable winds to make the expense and excess
Wind generators are reliable, efficient, and relatively
maintenance free. There's no need for you to ever have flat batteries
if you build redundancy into your boat's electrical generation system.
A couple of solar panels, a wind generator, and an engine mounted alternator
guarantee that there will be power available when you really need it.
Modern cruising boats are hungry for power, and for us,
the easiest way to get that power was with the Aerogen 6 wind generators.