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re: thermal shutters
26 jan 2003
bert menkveld wrote:
>> ...commercial greenhouses usually have 2 layers of plastic film glazing
>> stretched over 1 hoop frame. a small blower inflates the space between
>> them during the day. to add bubbles, make a trough full of 10% detergent
>> solution near the ground on each side with a 2" pipe full of holes just
>> underwater and blow air into the pipe to make bubbles. a 2" hole near
>> the top of the greenhouse can act as an air return to the blower or
>> shop vac. a piece of window screen over the hole can easily pass air but
>> distort with bubbles, turning off the blower via an outdoor microswitch.
>...my normal experience with soap bubbles is that they don't last.
the belgian physicist plateau kept bubbles in bell jars for years.
dust and dryness and co2 are their enemies.
>have you actually built such a system?
just a 2'x2' test window. others have built large systems, eg bill sturm's
10k ft^2 tomato greenhouse in calgary.
>do the bubbles last all night, or does the blower need to run periodically
>to refill the bubble supply?
it needs to run periodically, a few seconds per hour, if the
bubbles occupy 1000x more volume than the detergent solution,
with a 45 minute natural half-life.
>what does the glass/plastic look like after repeated filling and emptying of
>the bubbles? (would it be clear enough to use on windows you want to look
>through?)
i don't know. i think so. the glass gets washed every day.
>how do you get the bubbles out?
turn off the shop vac and turn on the inflation blower. sun helps.
nick
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