

mesm
From: Michael Holmes <[email-masked]>
Newsgroups: alt.solar.thermal
Subject: greenhouse heat storage
Date: Mon, 4 Mar 1996 14:12:05 -0500
Organization: McMaster University, Hamilton, Ontario, Canada (NewServer)
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I built a Brace type greenhouse a couple of years ago, largely to
overwinter more tender plants than the house would hold, and to get
a breath of spring in the winter.  It is freestanding and supported
on a deck over a 45 degree slope, for southern exposure
considerations.  The floor plan is 10x12 ft, (too, too small!) with
an 8ft high, 60 degree double glazed south wall and a 2 ft glazed
kneewall, giving an overall height of ~9 ft. The floor, walls and
roof are insulated to R28, and vented with two 2x2 ft vents,
thermally opened, near the peak, and one is fitted with a 
thermostatted fan. Backup heat is from a small electric furnace,
set at 6 C or so.  There is a small concession to heat storage in
the form of  8x 6 g pails of water.
This is all fine in November - January, with a lot of cloud
cover.(We are located in southern Ontario, 43N,80W.)  In February,
when the sun shines and outside temperatures are -10 to -20 C,
inside temperatures can quickly reach 40 C, and I have to vent and
/or shade... a considerable waste.  If I use more water pails in
the sun, I lose light and plant space.  

I am tempted to make a heat exchanger, e.g. an auto radiator near
the peak, and pump water through it into a larger water container
near the back of the greenhouse.  The questions are, how big a heat
exchanger, how fast to pump the water, and how much storage to
moderate the temperature swings?  Secondly, is there a better way?

I'd be glad of comments - even ranting!

Mike