Choosing A Marine Wind Charging System

Even the smoothest, quietest running generators still burn fuel, make noise, exhaust, vibration, heat, and demand that someone be aboard to operate and monitor these things most of the time. Modern, efficient alternative marine charging systems are available and capable of supplying reliable back-up and even primary power demands.

Cruising the Bahamas (some years ago) in a sailboat with an unreliable engine and minimal battery capacity, we rigged a hand-made propeller to an alternator and hung it from the stays. It was noisy and in need of constant adjustment, but it actually worked for a while until its own vibrations dismantled it. Things are better now. New technology provides efficient high-output alternators, quiet composite aerodynamic blades, and better mounting systems and control panels.

In a battery charging situation the components of a wind turbine energy generating system are the wind turbine itself; the mounting system; the rectifier and the charge controller, some system protection (such as fuses or breakers), any metering required, and the batteries.

Loads on the batteries may consist of 12 volt, 24 volt, or 48 volt direct current (DC) equipment or alternatively a DC to AC inverter can be installed so that alternating current (AC) equipment can be supplied. The inverter can be selected to supply AC equipment of 110 volt or 220 volt, and 50 Hz or 60 Hz as appropriate. Direct battery charging configurations are typical in yachts, and the power can then be directed through an inverter as needed.

Check manufacturer's specifications for RPM outputs vs. wind speeds. When the wind blows, the rotor blade stops a percentage of the wind. That percentage is what is converted into energy. According to physics, the maximum amount of wind energy that can be converted is 59.3%.

This is known as the Betz Limit. Be sure to get a marine unit designed to withstand a wet and salt environment. Check also for the DB (sound level) output. A wind turbine that sounds like a helicopter can destroy that evening ambiance. And if you're planning for long range cruising, make sure you will have access to parts.

Sailboats are the most common beneficiaries of wind power since they do not need (or like) to run engines, and usually have smaller fuel capacities. When choosing a location for mounting your wind generator, keep in mind that the best mounting spots allow the generator a free and unobstructed flow of the wind while keeping the rotating blades a safe distance from any rigging or possible body contact.

Stern Pole - The most common mount used for a wind generator is a stern pole. These can be easily fabricated from aluminum pipe, mount the unit clear of the deck and rigging, and provide relatively easy access for servicing. They have the added advantage of leaving any noise downwind while at anchor.

Radar Arch - Another variation of the stern pole with a lot more versatility allowing easy mounting of many different pieces of cruising gear including wind generators, solar panels, antennas, and often a tender. On my catamaran the arch is also stowage space for a life raft, and provides a shade awning behind the cockpit.

Mast Mount - If your boat has two masts, you may want to consider mounting your wind generator either 2/3 of the way up on your aft mast, or all the way at the top. This location provides for much more wind and results in a cleaner looking deck. You can buy commercially available brackets or have one fabricated specifically for your purpose.

If you need to service your wind generator, however, this location can make the task quite challenging. Also, be aware of the added stress factor on the rigging.
Fore-triangle Hoist - If you just can't seem to find a suitable spot to mount a wind generator, you might want to consider hoisting it in the fore-triangle. Although it won't be usable underway, hoisting a generator on the foredeck while at anchor is a reasonable way to supplement on-board power. Some wind generators are designed to be deployed and stowed, and feature components that are easy to disassemble and store.

Now we need to wire everything up. To regulate current flow, most wind generators require a controller. A charge controller senses the state of charge of your battery bank and halts or redirects the output from the wind generator when your batteries reach full charge. Many charge controllers for wind generators redirect the charging current to a dummy load as your battery bank approaches a full charge.

The mounting location for your charge controller can be anywhere between the wind generator and the battery bank, but it is usually placed near the batteries for ease of wiring the voltage sensing leads.
The last step before actually seating the wind generator is to run your wiring from the generator to the charge controller and onto the battery.

Before you can do that, you need to determine what size wire you'll need. Wire size is a function of the amount of current the wire will carry along its round trip length from the generator to the batteries, and then back to the generator.

When you run the wiring through the deck, and for stern pole mounting plates, don't forget to waterproof any holes. High quality sealants such as 3M 101 or Sikaflex 291 will do the trick. Once inside the boat, your wiring will snake through lockers and maybe under headliners until it finally reaches your charge controller. If you're lucky, you may find an existing conduit running to your batteries or electrical panel area. Do some poking around first to see if one exists before drilling your own route for the wires.
At your charge controller you'll find several easy connections.

Two voltage sense leads will run to your batteries, the positive leads from your wind generator will connect to the positive input on your controller and the positive output from your controller will lead to your positive bus. In this positive output line, install an in-line fuse holder that will eventually house a fuse rated at 1.5 times the rated output of your wind generator, but don't insert the fuse yet. Your negative wire from the wind generator may or may not bypass the controller depending upon the model. It should eventually connect to your common electrical ground.

Your final connection is the one that is going to be made as you install and mount the wind generator itself. Connect the outputs from the wind generator to your already run wiring, and slide the generator onto the mount. Keep enough extra slack wiring to allow you to easily uninstall the unit in the future for servicing. Insert the above mentioned fuse, wait for the breeze, and you're in business.

Whether you plan to cruise the oceans, or your yacht waits at the mooring for your next time-off adventure; free, non-polluting wind turbine power keeps those batteries charged and ready to go.

Be Knowledgeable, Be Aware, and Be Safe. Happy Boating!