This allowed Sun21 to travel a constant speed of 5 to 6 knots per hour throughout its voyage

That's about 1/3 the speed of a sailboat. The Mari Cha IV crossed the Atlantic in 6 days in 2003 at an average speed of over 18 knots.

Wind is a much better-suited (and much better tested) source of natural propulsion for water vessels. Can't see why one would try to use solar for the task.

Eric,

A knot is a unit of measure of speed (not distance) equal to 1 nautical mile per hour.

I have always thought that the best use for solar with the highest benefit is in applications where it directly displaces petroleum. Surely it is more economical to run a boat off solar than diesel?

Imagine if every large transport ship or tanker had its entire deck covered in solar cells? I am sure they could save millions of dollars over time. They also have a huge capacity to carry cheap, heavy batteries in place of ballast.

"knots per hour" is an acceleration, not a constant speed. "5 knots" is a constant speed.

Well, Francis, I find the voyage a real accomplishment.

First because the guys were thinking right for the times we're in.

Second, because they're working not with the top efficient solar panels on their boat. Think what we can do with the 40% efficient ones.

Ever calculated how much fuel you have to bring along for a transatlantic voyage when you can't sail or the winds force you off course?
What if you had an itinerary to follow and people on board??

Third, think the ship a lot bigger and make it a hybrid, alleviating the amount of fuel a cargo vessel would have to use.
I still have to find a cargo prez who refuses to save money in the long run. And protect the environment at the same time.

It's just doing the right thing. And it proves they're awake and doing something. Because you just oughta.

Francis,
People have been designing sailing vessels for several thousand years while solar PV is about 40 years old. The Mari Cha qualifies as a very mature technology, while the Sun21 is just a prototype.

Despite its maturity, navigating with wind is heavily dependent upon wind direction while an electric powered vessel only needs to account for wind and surf, not use it for propulsion. Eventually solar will become more competitive with wind. Perhaps a combined wind/solar hybrid would have the best of both worlds.

>> Wind is a much better-suited (and much better tested) source of natural propulsion for water vessels. Can't see why one would try to use solar for the task.

NOT TRUE! Obviously you have never travelled in a boat with an electric engine.

I love wind sailing, but I also love sunsailing.
Try it you will like it!

I see, so the wind can be inconsistent but clouds never blanket the sky and the sun never sets.

Makes a lot of sense.

Hey Benja -- The sun never sets and clouds never disappoint if you store some energy in a few batteries! And lithium manganese or lithium phosphate is perfect for something like this since it can deliver gobs of power, while being so much lighter than lead acid or even NiMH. No danger of explosion like the lithium polymer laptop batteries.

Why am I such a big believer? I cut open a bunch of the new cordless tool lithium batteries and put them in a few old tired scooters. Now it's like they've got a new lease on life, and are a blast to ride. They don't weigh nearly as much, and go quite a distance on each charge. The only downside: I spent over $400 for the batteries! Hopefully in time the price will go down as China is starting to make them.

Can't wait until I can afford a lithium-powered electric car!

I read somewhere on treehugger i think about Lithium batteries being as cheap as Lead acid in japan. But can't seem to find the article again. Any1 know a link to such info? By the way ..what's next after Lithium? Anyone in the know about battery tech? PEACE