My last comments re: "BTU's by the hour" were very close after all it turns
out, thank goodness (sigh). I would also like to thank those who posted
some physics-related info on the CP Digest (thank you .... Brett, Tim and
Adrian).
In an effort to avoid using physics-terms like calories and joules, and to
spare you all by explaining how a joule per second is the same a Watt, which
is the same as 3.41 British Thermal Units per hour... I can sum it all up
in the following description:
Ten - 55 US gallon drums, or ten - 45 imperial gallon drums, is a bit more
than 2000 litres. For every degree Celsius of temperature change, this
amount of water is "theoretically" able to absorb (or release) the heat
equivalent to running a 1500 watt electric heater for 1.6 hours in your
greenhouse. We can all relate sitting next to a portable electric heater on
high for that length of time. That's why I chose to use my equivalent unit
of "1500-Watt-heater-hours" to describe the system, it makes a lot more
sense to me as well.
This may not seem like much heat, but that's 1.6 hours worth free heat for
each degree that amount of water has to cool. Even if all that water is
only 4 degrees above freezing during the day, and it freezes out overnight,
that water would give off the heat equivalent of 6.5 1500-Watt-heater-hours
until it reached freezing itself. THEN, because 80 times more energy is
released when forming ice than when cooling water, this same amount of water
will give off the equivalent of 129.3 1500-watt-heater-hours which would be
like running that little heater for over 5 days. That's where the real
benefits of the water heat-storage system come from, in the way of
anti-freezing insurance.
That's all for this topic, folks - thanks for enduring. If there are some
of you who want to read more on water heat-storage, innovative solar
greenhouse designs, and optimizing solar gain in your (CP and/or Veggie)
greenhouse, try reading "Winter Greens: solar greenhouses for cold climates"
by Mark Craft.
See my following note for more about the book,
Randy