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

Myles,

Don't beat yourself up too much with your efficiency calcs, Remember that both of the Atlantic crossings were done in a 1 to 2 kt "downstream' current the whole way. So their performance is skewed a bit in their favor.

Fair winds,
Eric
Marina dle Rey, CA

--- In electricboats@yahoogroups.com, "Myles Twete" <matwete@...> wrote:
>
> It's fun and interesting to do comparisons.
>
> Another one: Energy/n-mi
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> Planet Solar – 4.5kwh/n-mi (@4kts)
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> Sun21 – 0.39wkh/n-mi (@3.5kts)
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> i.e. for a given distance, Planet Solar's girth requires more than 10x the
> battery and/or solar capacity than Sun21.
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> 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.
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> My barge boat "The Reach Of Tide" (about 2-tons):
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> 0.9kwh/n-mi @ 6kts
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> 0.54kwh/n-mi @ 5kts
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> 0.34kwh/n-mi @ 4kts
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> 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.
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> Planet Solar – 50 wh/n-mi/ton
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> Sun21 – 32.5
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> The Reach - 170
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> 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.
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> 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
>
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> 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
>