>From recent posts it appears that many listees are starting down the slippery slope of solar power. Solar power for battery maintenance is one thing. Solar power to run all ship systems is another. The limiting factor, other than your pocket book, is the amount of unshaded level surface you have available. Noon sunlight delivers about 1000 watts of power per square meter. Good commercial solar cells are about 15% efficient so you can extract approximately 150 watts per square meter. I estimate that an average trawler in the 40' range has about 4 square meters atop the pilothouse and possibly 6 square meters on the aft cabin roof for a total of 10 square meters. That assumes that you don't carry a dinghy on the roof. With 10 square meters of area you have space available for 1500 watts. In full sun, you will be able to generate full power for 5 hours a day or about 7500 watt hours. Add another 1000 watt hours for the morning and evening periods and you have 8500 to 9000 watt hours per sunny day. Averaged over a 24 hour day, you would be able to support about 400 watts of continuous electrical load. It may be enough to run a small refrigerator, a TV and laptop, modest internal lights, keep the battery charged, and run a bilge pump but not much else. You would certainly not be able to operate an air conditioner or an electric cooktop. But you probably do keep a dinghy on the back deck. That means you have only about 4 square meters of unshaded surface on the pilothouse. That reduces the solar generating capacity to 600 watts, 3000 to 4000 watt hours per full day, or about 150 watt hours of load averaged over 24 hours. It would be possible to run a small refrigerator for a few hours during the day, then use the solar power from early and late hours to keep up the battery and run the bilge pump. To fully power a well equipped trawler, refrigerator, air conditioner, TV, microwave, etc. would probably require about 20,000 watt hours over a 24 hour period. That might require 26 square meters of solar cells, about three times as much flat space as most of us have available. And, of course, you would have to keep a backup generator for those days when the sun doesn't shine. I know that passagemaking sailboats sometimes use solar panels to generate all their electricity but sailors have learned to drink warm beer. The current cost of solar power, using good commercial equipment, is about $0.60 per kilowatt hour. The is about twice as costly as power derived from a diesel genset even with $4 per gallon fuel. The best bet for most trawler owners is to install enough solar power for battery maintenance and bilge pumping. Alternatively cover the entire roof, and have some surplus power for a few other things. But unless you want to build an extension to your deck for additional panels, forget about fully meeting your electrical needs. But then boating isn't a rational exercise, is it? Larry Z ************** Biggest Grammy Award surprises of all time on AOL Music. (http://music.aol.com/grammys/pictures/never-won-a-grammy?NCID=aolcmp00300000002548)

<<To fully power a well equipped trawler, refrigerator, air conditioner, TV, microwave, etc. would probably require about 20,000 watt hours over a 24 hour period. That might require 26 square meters of solar cells...>> Larry, You are right, for the average energy-hogging trawler, solar makes little sense, except to keep batteries up when the boat is unnused. For those willing to make major changes, read on. The first line of attack for a solar trawler, like with all solar projects, is conservation of power. Household refrigerators are the largest waster of power, as they were designed to run on $.10/ kwh shorepower. My built-in top-loading refrigerator has 3.5" of urethane foam in the top and walls, 6" at the bottom. The boat's total power useage on the hook is about 80 amp-hours per day. Our single 75-watt Siemens solar panel provides about 15-20 amp-hours per day, depending on the weather (Florida). There's plenty of room on the pilothouse roof to add three more panels if I wanted to spend the money (about $1000 plus my installation labor) to be almost totally oil-independent at anchor. If you forego air-conditioning (follow the weather, snowbird) and electric cooking, it's not impractical to solar-power a trawler. A Hatteras 42 LRC I worked on recently has a house bank of (3) 8-D batteries, and can get along for over 24 hours before re-charging. That's 300 amp-hours in a day, x12 volts to give 3.6 kwh a day. And he runs an undercounter refrigerator and an old, innefficient undercounter freezer all the time. I just installed a battery monitor on his boat, and showed him how to look for parasitic loads (wall-wart chargers and a flat-screen TV) that use power from the inverter even when not being used. He'll soon be down to 250 AH/day. With a more efficient freezer, this boat could be a candidate for solar. <<The current cost of solar power, using good commercial equipment, is about $0.60 per kilowatt hour. The is about twice as costly as power derived from a diesel genset even with $4 per gallon fuel.>> A diesel genset might be able to make electric power for $.30/kwh, but most boaters do not. Gensets are run underloaded, used primarily to cook or make hot water. Cooking can be done more efficiently using propane, hot water using waste engine heat or solar). I would be amazed if most boat gensets make needed power for under $1/kwh. Again, solar is practical, but only if you're willing to change the whole boat, not just the electrical generating system. Mark Richter, M.E., M/V Winnie the Pooh, Ortona, FL Mark's Mobile Marine, electrical systems design, installation, and repair.