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more on backwards lamp dimmers
19 oct 1995
today an engineer told me that he was at a doe review meeting yesterday in
washington, dc. one of the speakers got up and showed the audience a pv panel
with a line cord coming out of the back and a 110 vac plug. he then plugged
the cord into a wall socket and put the panel near a window and measured the
power being fed back into the building's ac supply.

the developer was apparently solar design associates, a small company near
boston, and the eventual seller of this integrated small grid-tie inverter
product will be solarex, owned by amoco. 

>nick, did you ever try the idea of building a "solar hot cube" in the
>form of a concrete porch with water modules (55 gal drums, old milk jugs,
>whatever) set into it and built on the sunny side of the house so it could
>look pretty and do something at the same time?

i guess pretty-looking is in the eye of the beholder... you can make
things look pretty... why concrete, i wonder? why not just lay a piece
of plastic on the ground to keep down the dust, and put the drums on top.
when they are filled with water, they won't go anywhere.

this sounds like the right idea, marge. but i wouldn't "set in" the thermal 
mass. to me that sounds like the concrete would conduct the heat back into the
ground. the cube wants to have insulation on all sides.

for the perimeter drumwall, you could lay 2 8' pressure treated 2 x 4s on the
ground, 2' apart, put 4 drums on top of them, standing up, fill them with
water, put two more plain 2 x 4s on top of those drums, so the outside edges
of the tops and bottoms of the drums are tangent to the outside edges of the
2 x 4s, fill those drums, lay 2 more 2 x 4s on top of those drums, and 2
more horizontal drums on top, to make a 8' tall x 8' long wall.

then attach vertical 1 x 3s to the horizontal 2 x 4s every 4' along the wall
(3 of them for an 8' long wall) and attach some 4'x 8', 2" thick pieces of
styrofoam to the 1 x 3s with some long decking screws. paint the foamboard
with latex or acrylic paint. (here you can be an artist :-) to make it last
a long time. paint the south side a dark color, and attach a thin layer of
polycarbonate glazing to it, 3 or 4" away from the foamboard. put a couple
of plastic film dampers at the top and the bottom of the south side. build
3 more perimeter walls and fill the rest of the cube inside with 10 more
drums. lay two pieces of foamboard on top and put a 10' x 10' piece of epdm
rubber over that for a roof, with some rocks on top to hold it down (or old
tires, if you like the ae look :-) 

voila. an 8' cube containing about 42 55 gallon drums full of water. the most
expensive thing is the 10 sheets of styrofoam, $160 at 50 cents a square foot.
this would store the heat equivalent of about 10 gallons of oil at 130 f.
enough for several days with no sun. i think it would make a dandy backup
house heater and water heater, if combined with a low-thermal-mass sunspace...

where can you get some free 55 gallon drums near abilene? i put a small ad
in the local paper and found a company who were glad to give me 40 a month...

>or would that hold too much heat?

i doubt that will happen. how much is too much?

>and could it be reversed during the summer?

you could do some summer cooling this way, ventilating it at night, but
then you couldn't make hot water for the house...

nick