> I have been given (free) a 200 Watt panel, but so far have not come up 
> with an
> economical use for it.  At first was looking into the utility inter tie
> http://www.enphaseenergy.com/ MPPT units without the fancy internet 
> connect box
> but none of their $200 units would work with my panel because it has too 
> many
> (48) cells.
>
> Any ideas on how to use the panel in an economical way?

A "wasteful" but possibly useful way to use it is to heat water 
electrically.

48 cells or 48V?
The former is unusual. The latter is useful.

48 cells = about 24 Volt nominal.
36 cell panels are around 18V nominal (0.5V+ / cell in good light) with 
about 15 to 16V MPP (maximum power point) so your panel probably makes about 
20+ volts loaded.

A panel acts as a near constant current source if you load it beyond maximum 
power load. In this case about 10 amps if a 48 cell panel - see below.

At 200 Watts it will make about 200/20 = 10 amps.
You could use this to directly charge a 12V battery with a simple 
overvoltage cutout to prevent it boiling the battery.
For a larger car battery of around 40-50AH that is about C/4 rate which is 
OK for 'playing'. Using a buck converter to convert this down to about 15 V 
or a bit less will give about 35% more usable output.

You could use it to operate a 12V freezer (the opposite of the water heating 
energy store).

Extra points for fun: Drive an electrolysis unit to make Hydrogen, save it 
in an oil drum gasometer and burn it outside sunshine hours. Note: Playing 
with largish amounts of Hydrogen even at near atmospheric pressure can be 
hazardous to your health. YMMV.

Drive a water pump.

The 48 cells are a bit low for a 24V system but would provide some charge 
into a 24V lead acid system.


   Russell McMahon



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