Weekend Workshop

By admin ~ December 12th, 2008. Filed under: Weekend Workshop.

The Answer’s Blowin’ in the Wind Adding a wind generator can keep your batteries charged and reduce pain at the pump

By Frank Lanier

My respect for wind power was born during a childhood spent on the hurricane-prone coast of North Carolina. From howling storms to benign breezes, unlimited energy is out there. The trick is harnessing it, which is exactly what wind generators let us do. Higher fuel costs have many power boaters lusting after some of the free power wind generators can provide in order to supplement traditional generator installations. Here’s a look at the basics of choosing and installing a wind generator.

Wind Generator Basics

Wind generators are typically classified as either small rotor units with blade diameters less than 48 inches, or large rotor units with blade diameters of 60 inches or more. Output varies according to blade size and the units themselves, but a rough rule of thumb is that large diameter generators produce around 4 amps per hour in 10 knots of steady wind, while smaller rotor units generate around a third of that, or 1.3 amps per hour. Wind generators utilize either a DC motor or an alternator to generate power, each of which has its pros and cons. DC motors have brushes and commutators, both of which require periodic maintenance to prevent generation of electromagnetic interference, which can disrupt nearby electronics. Models with alternators initially produce AC voltage, which is then converted to DC via rectifying diodes.  These diodes are prone to damage if exposed to reverse-polarity voltages.
Although they have less output, small rotor units–those typically found on yachts–have the advantage of less weight, as well as lower start-up speeds–the wind speed at which the unit actually starts producing power. The start-up speed of a wind generator and its output in winds of 10-15 mph or less can be more important than maximum rated output. At some point (typically around 35 knots of sustained wind) you’re approaching too much of a good thing and will need some form of blade speed control mechanism, both to prevent physical damage to the unit and to avoid battery damage due to overcharging.
Braking or blade speed control can be accomplished in several ways. Some wind generators have specially designed blades that stall out at certain speeds, while others are designed to gradually turn away from the wind if it becomes too powerful. There are also friction and air braking systems, the latter being considered by many to be more reliable at higher wind speeds. Most units also offer the option of installing an electronic stop switch. Many wind generators also have a small hole in the “tail fin” of the unit, allowing you to use a boat hook to grab it and pull the unit away from the wind to safely secure it.
While construction, size, weight and ease of installation are all important considerations; noise is often a deciding factor for many boaters. All wind generators make some sort of racket, but noise from some is on par with running an engine at anchor. A good way to compare the noise levels of various units is to walk the docks of your local marina or dinghy around the mooring field on a windy day and listen.

Mounting Options

As with most equipment installations, choosing a mounting location is a balancing act between aesthetics and performance; your choice can look good but operate poorly, or vice versa. The best spots are those with an unobstructed flow of wind and high enough to keep whirling blades clear of structure, rigging, self-steering vanes, davits, tenders, and crewmembers.
For convenience and safety on powerboats, poles are a popular mounting choice. They hold the unit in place while keeping it up and out of the way. Whether located in the stern or on the hardtop, poles consist of a stainless steel or aluminum tube about two-inches in diameter mounted with a deck bracket or rail clamps, and guy wires or metal struts to provide diagonal support from the pipe to the deck. Bracing is crucial for strength and to reduce pole movement, which in turn minimizes vibration and noise below decks. Stainless steel is stronger, however aluminum tubing has its advocates – it’s lighter and easier to work with than stainless and its flexibility tends to dampen vibrations. Make sure the blades can rotate through 360 degrees without striking anything. Companies such as eMarine offer complete mounting kits that can take the guesswork out of installation.
Once in place, the wind generator must be connected to your power supply. Regulating the voltage is crucial to preventing damage to your boat’s electrical system. Most wind generator companies offer controllers specifically designed for their units. But, if you prefer to put together your own set-up, you will need to select a regulator or controller to keep your batteries from overcharging. You must make sure the regulator is rated for the maximum output of your wind generator. Controllers designed for solar systems are often not strong enough to protect your electrical system from the high power surges a wind generator can produce. As always, it’s advisable to have an ABYC certified electrician install, or at least inspect, your wiring. Be sure to follow the manufacturer’s recommendations on wire size and types and sizes of protective fuses.
Once you’ve selected a wind generator and found the perfect spot to mount it and have it hooked up, will the benefits outweigh the effort? Chances are your need for onboard electronic doodads will likely increase rather than decline. A good energy plan utilizing wind and solar power to supplement your onboard diesel or gasoline-powered generator can go a long way toward reducing fuel expenses and equipment wear.  As far as alternative energy sources for powering your boat’s systems are concerned, the best things in life really can be free.

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