At the risk of re-opening this discussion. Besides coke cans
there is another readily available material that could be used.

For the price of two or three cokes you can buy 10 feet of
tubing used for built in household vacuum cleaners. In Canada
and the US available in most big box hardware stores.

This tubing is thin walled light and easy to work with. (I use it as
replacement tubes on bird feeders) It lasts quite well outside.
Some of the bird feeders are 7 or 8 years old

A few months ago I attended a seminar that Microchip was
running on reference designs for putting power back into the
grid. Three things came out of that seminar.

1) Intermediate storage batteries are a bad idea. They don't
    last very long.

2) Even small amounts of power can be practically fed into
    the grid even through a plug in the wall.

3) The major design problem is a control loop that phase
     locks to the line. The reference designers we mostly
    PIC32 based.


w..

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