T-Pain Is On A Boat: RE: [Electric Boats] Crossing the Altantic with solar power

Monday, February 21, 2011

RE: [Electric Boats] Crossing the Altantic with solar power

It’s fun and interesting to do comparisons.

Another one: Energy/n-mi

Planet Solar – 4.5kwh/n-mi (@4kts)

Sun21 – 0.39wkh/n-mi (@3.5kts)

i.e. for a given distance, Planet Solar’s girth requires more than 10x the battery and/or solar capacity than Sun21.

But for those who aren’t familiar yet with the cost of speed, that ½ kt of speed difference biases the answers above in favor of Sun21. If Planet Solar slowed down to Sun21’s speed and they cruised together, you might find that Planet Solar’s number drop as low as 3.0kwh/n-mi, making the ratio more like 7.5x.

My barge boat “The Reach Of Tide” (about 2-tons):

0.9kwh/n-mi @ 6kts

0.54kwh/n-mi @ 5kts

0.34kwh/n-mi @ 4kts

Based on the above, my boat appears to be better engineered than the others…but something must be wrong in looking at it this way. A better comparison might be to include the tonnage in the efficiency comparison.

Planet Solar – 50 wh/n-mi/ton

Sun21 – 32.5

The Reach - 170

This makes for a better comparison I think for the application---cruising across the seas. Both of the highly engineered vessels have vastly better efficiency/ton rating than my heavy plywood vessel.

-Myles Twete, Portland, Or.

From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of qc_ca_666
Sent: Monday, February 21, 2011 8:17 AM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] Crossing the Altantic with solar power

Hi all!

Sun21 and Planet Solar were built with totally opposite strategy.
But how do they compare in the middle of the Atlantic?

Planet Solar: Bigger is better
Weight: 95 tons
Cruise speed: 4 knots @ 18 kW (24 HP)
=> 190 watts/ton

Sun21: Small is beautiful
Weight: 12 tons
Cruise speed: 3,5 knots @ 1,35 kW (This is under 2 HP!!!)
=> 113 watts/ton

From that point of view, Sun21 is a clear winner.

Regarding their respective solar array, it's interesting to note that the efficiency has improve only slightly over the last years.

PlanetSolar: 93.5 kW @ 537 m2
=> 174 watts / m2

Sun21: 10 kW @ 65 m2
=> 154 watts / m2

Bye!

Pierre