Using 200L plastic Drums for Space Heating
If you fill a 200L drum with moderately hot water (50 deg.C), and place
it in a reasonably cold room (10 deg.C), it will radiate heat in a
similar amount as a 1kW electric heater. (It's possible to work it
out by using the surface area of the plastic, the coefficient of heat
conductivity, the thickness, the difference in temperature, etc., but
it's easier to just try it!)
It will continue to radiate useful heat until the drum temperature
drops below approximately 30 deg.C. (Assuming that the room
temperature doesn't rise too much - although we do want it to rise
somewhat - after all, that's the object of this exercise!)
I've done some calculations around this theme, and they look good!
A 1-KW bar heater radiates heat at the rate of 3.6MJ per Hour
A 200-Litre plastic tank of hot water at 50 deg.C holds 15MJ of
Useful Heat ("Useful" is defined as being above 30 deg.C)
So, each 200-litre tank which you can fill with hot water from your
solar panel during the day, will radiate 3.6MJ per hour into the air
of your house at night, for about 4 hours.
HERE'S HOW TO DO IT:
Build a wooden, insulated tunnel, big enough to hold about TEN
200-litre plastic drums, side-by-side, with an air gap between
and around them. (A gap of around 100mm should do)
Set up some air ducting and a fan, to draw air from the coldest
part of the house and blow it through the (hot) tunnel and back into
the living area of the house.
Set up your 30 sq. metre (7kW) solar panel so that it pumps the hot
water it generates into the plastic drums, which are connected
in SERIES so that the hot water flows in one end, out the other,
and back to the panel again after coming out of the last drum.
During the day, the solar panel will heat up the drums at a rate of
around 20MJ per hour (that's what my solar panel does, anyhow), and
assuming that most of that is actually stored in the plastic
drums, you'll have around 50 to 80MJ of useful heat stored after
four hours of reasonable sunshine.
Then at night-time, you turn on your fan and open the air duct into
your living area... and at the rate of 10MJ per hour, you can run
it for around 5 - 8 hours!
Ok, now sit back and enjoy all your hot air!
(I DO intend to set up a design like this, so watch this space...)
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