[EVDL] Electric Solar Boat

[George McNeir via EV]

Mike Nickerson and all,

My apologies for not answering your last question more accurately about total 
wattage off the roof and per square foot. At 65 x 39 inches (17.6sf) the 11 
modules yield 2,585 watts (13.3 w/ft2). Their replacement with cells of similar 
output and utilizing the full roof area (not limited to large rectangles) would 
yield nearly 30 square feet and 3990 watts.

That would probably increase the speed to well over 4 mph and keep the battery 
bank full all (sunny) day. There are very special batteries I will be using as 
soon as one of the companies with whom I am working, get them into production. 
They are not Li types, they are in fact extremely close in specification to 
current Li units but are foamed lead acid. Many of the inter/intra-cellular 
balancing schemes and temperature problems are avoided with weight and power 
density the same. Some of that is covered and linked from   
http://www.mogcanalboat.com/

The major difficulty with a boat, that does not arise with cars and airplanes, 
is the need for sleeping, cooking, watermarking, power creation, hot water, 
anchors/chain, ground tackle, dingy, auxiliary power and a freezer, just to 
mention a few. For those reasons everything on the boat must have two uses (at 
least) or available living space gets filled in. Heat from PVs is used for 
assisting hot water and refrigeration in winter is used as an additional 
heating source…..  on and on. This all results in creating a power grid 
(redundancy) instead of just ‘wiring’ and breakers.

Keeping the 'down from roof voltage low' is also key to avoid frying someone's 
pacemaker (not sure that is a reality but is an example). However, the voltage 
must be a bit higher than the battery bank voltage to have best performance of 
the MPPT solar electric controllers.

George
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[EVDL] Electric Solar Boat

[George McNeir via EV]

Mike Nickerson,

The 24 volts being used for the overall system voltage was a technically 
painful choice but needed for a salt environment. I have been shocked at 48 VDC 
in salt bilge water and can say that it is weird and unpleasant. There are an 
increasing number of marine electronics that utilize 24 to 28 volts DC as well 
as consumer/commercial DC/DC step downs to 12 VDC and 110v AC mod and full sine 
inverters. Some of that stuff was not even around 5 years ago, Moore’s Law, huh?

The use of 24VDC from a PV standpoint is that the down coming voltage from the 
roof can be kept above the system voltage (for MPPT) whilst not being a painful 
shock/burn. Roof down voltage is about 30 plus VDC on one panel (5 PV modules) 
and 72 VDC on the other panel (6 PV modules). A Schnieder and Outback 
controller is used for the control of the 2 down coming voltages. The Outback 
is a refined MPPT (tracking the mix of current to voltage for maximum charging 
efficiency, Maximum Power Point Tracking). The Schnieder (was called a Trace 
C40) is meat and potatoes. I look forward to the total replacement of the 11 x 
235 watt PVs with thin film  flexibles and dropping the 72 VDC down coming 
voltage to about 36 VDC……   more time…. more money.

The boat was designed around the roof. The gross size is about 10X26 feet but 
with the correct PV system I can drop from 11 huge rectangles to full coverage. 
Also the weight is 11 X 44 pounds which will be dropped, with the thin PVs, to 
a total of 140 pounds. From 484 pound to 140 pounds is a stellar achievement 
and reduces the inertia of rocking and the sustained lean angle. PV heat 
dissipation is still a trick thing and is part of the hot water heating system. 
  History button ofhttp://www.mogcanalboat.com/   gives a bit more design 
insight.

I sold the Onan 4Kw,1800 rpm genset a long time ago, never used it. A superb 
gen, it was not needed. The Lestronic 48 VDC charger was used about 5 times in 
10 years and is currently used to hold down the floor tiles in the garage. I 
have a woefully small 24 VDC charger and have no immediate plans for a 
Lestronic or marine unit, but, someday though.

Best to all,   George



Hi George,

Thanks for the specifications.  The 24V operation is interesting.  Most cars 
use higher voltage and lower current.  That allows smaller sized wires to carry 
current.

However, I suspect the 24V has some benefits too.  First, lower voltage is 
safer than higher voltage.  Does the 24V integrate better with the solar cells? 
 Seems like it might.

When people ask about solar cells on a car, the typical answer is to skip them 
on the car and put the cells on the carport instead.  The boat is big enough 
that it's top is probably the size of a carport.  How many square feet of solar 
cells are on the boat?  Is there charging for the batteries besides the solar 
panels?

Mike
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