The Joys Of Free Power

The advantages of going solar

March 2011 Feature Dan Bullard

Houseboating is such a freeing pastime. It gives you a chance to get away from the neighbors, the roar of traffic, the bustle of the city and to just bask in the quiet beauty of natural surroundings where wildlife practically parades by and says, "Hey, look at me!" All of that can change however, when you fire up your gas or diesel generator.

What if you could meet nearly all your power needs with no noise, no smell and no fuel bills, while also delaying that dreaded day when your generator gives up the ghost and has to be replaced?

The Quiet Solution

The best answer is solar. While wind power is alluring, it's noisy, and really, how many of us want to anchor in a windy area just to get free power? Only solar power is free and completely quiet. Since most boating is done during nice sunny weather, we know there will plenty of solar power available for our wizzy electric gizmos.

On a clear day, the sun blankets the earth's surface with about 1,000 watts of energy per square meter (a little bigger than a square yard). And 1,000 watts is a little less than what it takes to run the typical blow dryer, coffee maker or space heater. To harness that energy we use solar panels, arrays of solar cells mounted in an aluminum frame with a sheet of glass protecting the cells, like a homeless window. Because much of the sun's energy comes in the form of heat, ultraviolet light and other forms that solar panels can't use, even the best solar panels are only about 12 percent efficient. This means that 1,000 watts per square meter is reduced to about 120 watts. Most people have seen a 100-watt light bulb, so you know this is still a fair bit of power, and since it's free we will overlook the relatively low efficiency.

A 120-watt solar panel produces about 7.5 amps of electricity for a "12-volt" system. Realize that it's not generating exactly 12 volts, but given sufficient sunlight a solar panel can produced anywhere from 13 volts up to 17 volts, which is what is required for charging 12-volt batteries. This is really the point of solar: your batteries will be charging all the time the sun is shining, even if you are using power for other things.

Location, Location

Do you think you can find an area on your houseboat that is at least three feet by three feet? Sure! Houseboats are more suited to solar power than virtually any kind of boat, with big flat roofs and spacious awnings. You just need to make sure the panels aren't shaded most of the day by radar arches, antennas, flags, rails, etc.

Also, you can connect multiple panels together in parallel, so their currents combine. If you have two square meters of space you can get twice as much current, around 15 amps. Four square meters would yield 30 amps. Can you scrape up eight square meters? That would be 60 amps of current, just by connecting eight solar panels together. You'll need a pretty hefty bank of batteries to take that much charge current. But they don't have to take it all if they don't want it, because you'll have a charge controller installed between the solar panels and your batteries.

Charge Of The Light Brigade

A charge controller is a smart electronic box that regulates the output of the solar panels while monitoring your battery voltage to ensure an optimal charge. Regulation is necessary because a solar panel can generate up to 17 volts and that much voltage might fry some of your electronics and eventually boil your batteries dry. The charge controller starts every day tapping the solar panels to provide the "bulk charge" at an elevated voltage level, around 14.4 volts.

After the bulk charge phase, the charge controller regulates the voltage down to 13.2 volts to keep the batteries trickle charging; this is called the float level. If you fire up your TV, computer, stereo or other device, the charge controller portions out more current for you to use while still maintaining the 13.2-volt float level for the batteries. If you turn on lots of gizmos you can pull all the power the solar panels can produce, plus all the power your batteries can provide. As soon as the popcorn is popped, the coffee is hot, or your daughter's hair is dry, the charge controller will go back to bulk charging to bring the batteries to their fully charged state. That way when the sun goes down, pretty much no matter what you did all day, you can use as much power as your batteries can store. Next morning when the sun comes up your charge controller will go into bulk charge mode to fully recharge your batteries for another day of fun.

Economic Enlightenment

When we think about power costs we tend to think about how much fuel our generator uses. If your generator consumes a half gallon of fuel per hour it's easy to do the math to find that it costs upwards of two dollars per hour of power. But fuel is just one cost of producing electricity with a generator. Generators don't last forever; each hour on that generator is one more nail in its coffin and when it dies it has to be replaced. The typical gasoline generator might last 2000 hours, and its replacement might cost you $5,000, which adds $2.50 per hour for expenses. This brings the cost of power to $4 to $5 per hour.

Do The Math

Now, let's imagine that you install a modest solar array of 1000 watts occupying eight square meters, or eight 120-watt solar panels. These panels sell for about $600 each, which totals $5,000 including the charge controller, about the same as your generator. However, solar panels last for 20 years no matter how much you use them. Assume that you will be getting power from them for 12 hours a day. That $5,000 investment will provide power for about 88,000 hours, bringing the hourly cost down to 5.7 cents per hour. Plus, no matter how high gas or diesel prices go, the solar panels won't care! Your solar panels will produce power year after year with no maintenance (other than an occasional washing), no oil changes, no carbon monoxide or carbon dioxide, no noise and they won't sit there like a parasite sucking your fuel tanks dry. With solar, every hour of sunshine becomes one less nail in your generator's coffin, delaying the day you have to replace it. If you add solar to your houseboat you can still use your generator on those days where it's too cloudy or rainy, or when you simply need more power for running the air conditioning or other high current loads. But how nice would it be to relax all day with nary a peep from your generator, never smelling that whiff of exhaust, knowing that your fuel tanks are just as full today as they were yesterday? Every time the sun shines, you'll smile, knowing you are getting something you really need for free.


About the author

Dan Bullard lives aboard Great Ambition, a solar-equipped 50-foot custom Catamaran Cruiser, with his wife April in the Pacific Northwest, not known for its sunny skies. They cruise the Columbia River and record their adventures in a photo blog at Dan can be reached at

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