GL: More on solar powered Loop boats

[LRZeitlin at aol.com]

Is solar power practical for my present trawler? 

I have a Willard 30 motorsailer, 30' LOA and 11' beam, displacing 15,000 lbs. 
The approximate surface area of the deck is 260 sq. ft. If a flat sunshade 
covering the entire deck area were covered with efficient solar cells, I could 
hope to generate 5,750 watts of power in direct overhead sunlight. This works 
out to about 7.7 hp. Assuming that I have a very efficient electric motor, I 
could probably see about 6.9 hp at the prop. This would be enough to move my 
Willard at about 5 kts. through relatively calm water.

If I wanted to go a bit slower, say 4 kts., I could dump half the generated 
power into a battery for use when the weather gets cloudy or at night. My boat 
carries 4000 lbs of ballast. If I replaced all the ballast with lead/acid deep 
discharge batteries, I could probably store 60 KW/hrs of energy. This is 
roughly equivalent to 80 hp/hrs. or enough to power the boat at a 4 kt.. speed for 
18 hours.

Converted to solar power, a Willard might make a marginally practical inshore 
cruiser. It could even do the Great Loop, although slowly. During the summer 
the northern portions of the Loop receive 16 hours of sunlight and i could 
expect to make 50 miles a day. At least on days when the sun shines.

Would it be economically practical? Probably not. At current prices the solar 
panels necessary to cover the Willard sunshade would cost in the neighborhood 
of $40,000. The batteries another $3000, and the motor and controller another 
$5000. Surprisingly all the components are available "off the shelf." But 
since the demand is small, the prices are high. I can imagine that the price 
premium on the solar powered SeaRay would be at least $150,000.

However with the current emphasis on energy independence, component costs 
might drop in the near future. An electric motor from a Prius or Honda, a yet to 
be developed battery pack from a GM Volt, and solar cells from suppliers 
ramping up to meet household needs might drop prices for the solar powered Willard 
to the $20,000 range. At that point it becomes competitive with modern diesel 
installations. If fuel costs do rise to the $10 a gallon level, the small 
solar boat has a chance.

I'll still keep the sails on my motorsailer just in case of a long cloudy 
cruise.

Larry Z


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