Green Advice: Think Before You Spend
Before you rush out and buy alternative-energy sources, understand your needs and determine the best technologies to meet them. "Systems" from our April 2012 issue.
Wind power can often take over when the sun goes down or the cloud cover renders a solar array nearly useless. Some of the most popular wind generators can deliver up to 400 watts, or 33 amps, of power at 12 volts.
We’ve seen improvements with this technology in the forms of increased low-velocity wind performance and the integration of microprocessor-controlled voltage regulation built into the generator body rather than executed via external regulators. Also, the trend seems to be toward the use of alternators rather than DC generators on more modern units. Alternators are theoretically more efficient. All of these incremental improvements are steps in the right direction.
There are several key things to consider with wind generators, besides theoretical power output. One is how much wind it takes for the unit to kick into action and start delivering useful power. A second factor that I find personally annoying is how much noise the unit generates under average conditions. Not to be ignored, either, is blade diameter and the physical space limitations on your particular boat. You want such a unit to be far away from people on deck under absolutely all conditions!
Remember that you’ll generally attach your wind generator on some sort of pole mount that in turn will be through-bolted to your boat’s deck. This typical structure will act as an amplifier for any noise that the wind generator creates. This can be especially pronounced with units that utilize blade articulation to help slow them down in heavy winds. If you’re weighing the purchase of a wind generator, consider getting on a boat to experience your model in use; at least run a query on this subject at the many alternative-energy websites. I’ve been aboard boats on which the wind-generator noise in a 15- to 20-knot breeze was enough to make me very uncomfortable. Some of the newest units employ electronic overspeed protection that I’ll bet is considerably quieter.
I think the best strategy for selecting a wind generator, in addition to what I’ve mentioned already, is to study carefully the product’s projected performance curve, indicating the power generated at a given wind speed. If the vendor can’t provide you with that data, be suspicious. Make sure to match this curve to your typical wind speeds to get a feel for the total weekly or monthly power-generating capabilities of the unit. If you live in an area of really light air, you may find that the return on your investment here may not work out.
How About a Water Generator?
Cruising hydrogenerators have never been very popular. But I recently inspected a unit that I think might just change that. Made in Europe by Watt & Sea and now available here in the United States through eMarine Systems, these units are really slick!
Consider these numbers: Say the unit delivers 120 watts at 5 knots of boat speed. That works out to 10 amps. Multiply that by the number of hours you maintain that 5-knot speed. In 24 hours, you’ll have generated 240 amp-hours of electrical current. Not too shabby!
Whichever way you go with alternative-energy solutions for your boat, whether it’s all solar, solar plus wind, or solar, wind, and water, keep in mind that you’ll also need to integrate charge controllers and switching systems to maximize your power-generating setup. Also, you may be converting some of the power you generate and store in batteries to AC current via an inverter. The options in this arena are almost endless and a bit complex for the electrically challenged. If you fall into that category, I highly recommend that you consult with an experienced marine electrician. Done properly, an onboard alternative-energy system employing all of the things mentioned here can truly take you a long way away from a petro-based world.
Ed Sherman is the educational programming director for the American Boat & Yacht Council. Read his frequent blog posts in Ed’s Boat Tips.