Solar Panels vs. Wind Generators

Posted by at 08:31AM - Comments: (15)

May 28, 2013

The world’s largest solar-powered boat, MV PlanetSolar, is heading toward Miami for its U.S. debut and the start of a 16-city world tour.

As the world’s largest solar-powered boat heads toward Miami for its U.S. debut and the start of a 16-city world tour, I was reminded of one of the most frequent questions I hear from Practical Sailor readers: "Which is best, solar panels or a wind generator?" The answer, like many things regarding cruising equipment, depends on where you cruise and the type of boat you own.

The MS Turanor PlanetSolar, the world’s largest solar-powered yacht ever constructed, offers a persuasive case for solar power. The sun-powered, 102-foot catamaran, which recently broke its existing Guinness World Record for completing the fastest trans-Atlantic crossing with a solar boat (22 days), docks in Miami later this week. Stops in New York and Boston are also included in its 2013 itinerary. Following its U.S. visit, the vessel will set sail on a trans-Atlantic, scientific expedition to study climate change.

For most U.S. sailors contemplating investing in renewable energy sources for the first time, it makes sense to buy a solar panel before a wind generator. For about $700, you can buy a pair of 60-watt panels that can generate about 240 watt-hours or 20 amp hours (assuming four hours of peak sunlight). This won't cover the amp-hour requirements of a modern cruising boat, however.  (To roughly convert a solar panel's watt rating to amp-hours per day, marine technical author Nigel Calder offers the formula: amp-hours per day at 12 volts = the panel's rated wattage ÷ 3.) Although wind generators can deliver more than double this output during a 24-hour period, many U.S. anchorages and marinas don’t have the consistently breezy conditions they require to reach their potential. That conclusion was borne out during our long-term test of five models on a hilltop in Rhode Island, a relatively windy U.S. location, during the mid-1990s. Testers then came to the dismaying conclusion that over the long haul, an average 50-watt solar panel would outperform the units we tested.

Results were different in 2007, when we simultaneously tested five wind generators through a breezy Chesapeake Bay winter. The results of that wind generator test (accessible only to subscribers) and an article on choosing a wind generator based on that test offer a more optimistic view of wind energy. As the results of the 2007 test demonstrate, in windy areas such as the Caribbean, wind generators can do a much better job of keeping up with the demands of 12-volt refrigeration, usually the biggest energy hog on a cruising boat.

Ultimately, which system will be most efficient for you depends greatly on the region you intend to cruise. Although many long-term cruisers making a loop through the Caribbean do just fine with solar alone, those with high energy demands find that supplementing solar with wind energy offers the best opportunity for keeping batteries charged 24/7.

There are several websites that discuss the pros and cons of these alternative energy sources from a sailor’s perspective. EMarine, a company that sells both solar panels and wind generators, offers a cut-and-dried comparison of solar vs. wind. Although the article is based on some generic assumptions that may or may not apply to your cruising region, it offers a concise look at the pros and cons. Nigel Calder’s "Boatowner’s Mechanical and Electrical Manual" offers a more detailed discussion of these two systems. Last year's blog update on solar panels also includes a number of links to Practical Sailor articles on solar trickle chargers, using multi-point power technology to boost solar panel output, tips on prolonging lead-acid battery life, and options for mounting high-output installation.

If you can look past the obvious sales pitch, West Marine’s West Advisor on solar panels also offers a good overview of solar systems for marine use. Although it has been a while since we have looked at solar panels, we are not big fans of flexible panels. If you are seriously in the market for a solar panel, look for rigid panels with 20-plus-year warranties. Since much of the appeal of solar panels is their durability, we would be interested in hearing about readers’ experiences with specific brands of solar panels over the long haul in the comments section below.

Comments (15)

We had a wind gen but hated the noise (even the non-noisy ones make noise), and could not find a convenient mounting place that didn't shade the solar panels. Finally added enough solar (~650 Watts) that we have more than enough. Even on cloudy days we are charging at ~10 amps, and do 40+ amps on sunny days. By noon we are topped off and can charge all the computers, etc with the excess.

Posted by: DAVID M | June 12, 2013 5:46 PM    Report this comment

This year we installed a Solbian flex panel 125watt panel and an Air Breeze wind generator on our 37 foot Tartan and so far, both have complemented the other so that my 500 amp hour wet cell battery bank stays topped off while leaving my Sea Frost refrigerator on at all times. I also have an electroguard system aboard which draws a small amount of amperage. I monitor my battery banks remotely twice daily with a Siren Marine monitoring system which works great. I think a combination of both is the way to go. During a sunny day, the 125 watt solar panel definitely out performs the wind generator but over the course of a 24 hour day, I think it's a wash. I don't think either one alone would be sufficient to run my fridge and keep my battery banks topped off. LEV

Posted by: levenezia | June 3, 2013 6:02 AM    Report this comment

We left 4 years ago with a wind generator. A year later we added 270 watts of solar and turned of the wind gen, which was great for NE summers (lots of sun) and bahamas winters (lots of sun). When we reached the Caribbean, with warmer water, and fewer hours of sun, we use the wind gen also. We still had to top off occasionally until we switched to Lithium batteries (Lithionics). One of many advantages is that they do not loose energy to heat on charge and discharge... the result being that we have more amp hours available to us. If we do run the alternator, Lithium with take full current until the battery is almost full.

Posted by: BILL C | May 30, 2013 10:06 PM    Report this comment

One thing to be careful about is that the PV industry is having a huge quality problem right now. PV panels that would normally last 20-30 years are failing in about 2. The following article has more details, but suffice to say, that one should be very careful when buying new panels...

http://www.nytimes.com/2013/05/29/business/energy-environment/solar-powers-dark-side.html?ref=global-home&_r=1&pagewanted=all&

jdh

Posted by: JOHN H | May 30, 2013 7:04 PM    Report this comment

Or maybe just watt hours...

Posted by: Raymond S | May 30, 2013 12:17 PM    Report this comment

KW is a measurement of power, kw h is a measurement of energy. What the article should have said is that the 60 watt panels could produce more than 1500 kw h on a sunny day

Posted by: THOMAS W | May 30, 2013 9:30 AM    Report this comment

There is another X in that formula... The number of hours of sun available in the summertime.

Posted by: Raymond S | May 29, 2013 10:20 PM    Report this comment

That's pretty expensive for good solar panels these days. I spent less than $300 on my two 50 watt Ramsond mono-crystalline panels and another $125 for a Genasun MPPT controller. You just need to avoid shadows and overheating of the panels for maximum output.

Posted by: Raymond S | May 29, 2013 10:18 PM    Report this comment

You cannot get 1500 watts from two 60-watt panels. 2 x 60 watts = 120 watts. You need to get someone who passed Physics 101 to review all of your technical articles.

Posted by: PeterG | May 29, 2013 10:12 PM    Report this comment

I agree that there should be ongoing tests of solar panels much like the various tests of anchors. While I think the anchor tests are more important the innovation cycles of solar panels are much more frequent.

Posted by: George B | May 29, 2013 5:36 PM    Report this comment

Technically, wind power IS solar power.

Posted by: James W | May 29, 2013 5:01 PM    Report this comment

What about fuel cells? They seem to be a good choice for some (like me). There is no way you will see solar panels or a big propeller above deck on my boat! Ugly, extra windage, delicate, many moving parts. Complicated electrical systems. Not to mention HOLES in the deck!!

Fuel cells may be expensive to buy, not inexpensive to run. simple 2 wire hookup (+ and -) But they are below deck, quiet, no moving parts. More than powerful enough to keep the batteries topped off for a refrigerator and bilge pump. And they keep the boat looking pretty!

The space program has been using them forever. Solar was not an option for manned spacecraft to the moon, so they used fuel cells!

Seems the logical way to go, to me, anyway.

Posted by: Phantomracer | May 29, 2013 12:45 PM    Report this comment

I find that the combination of solar and wind is right for us in the Caribbean, Bahamas and Florida. An additional point is that while doing overnight sails the increased apparent wind does a great job keeping up with the needs of navigational equipment and the autopilot.

Posted by: EDWIN J | May 29, 2013 12:31 PM    Report this comment

I am using a combination of semi-flexible panels from Aurinco and a wind generator and find the combination to be great and quite complimentary to each other.

Posted by: David S | May 29, 2013 11:30 AM    Report this comment

I'd love to see a fresh evaluation of solar panels. The technology and costs have improved so much in the last 10 years!

Posted by: Unknown | May 29, 2013 10:58 AM    Report this comment


Add your comments ...

New to Practical Sailor? Register for Free!

Already Registered? Log in

Forgot your password? Click Here.