On Jul 23, 10:39*am, Home Guy wrote:
Larry Fishel wrote:
I have a temperature sensor mounted about 1" under the plywood
roof deck in the attic and it went from about 120F to about 100F
during the watering.

The temperature at this point may be misleading (most affected by the
sun, least affected by venting).

I don't agree.

Air currents in a soffit-ventilated attic will flow primarily from the
intake point (the soffits) up along the underside of the decking to the
peak where the exhaust fan is located.

By placing the sensor mid-way up this path, on the underside of the deck
(but not touching it) I'll get a good sense as to the heat load that the
shingles are transfering to the attic space - in terms of the
ventilation system's ability to remove this heat.

Because the water was able to carry away the heat from the shingles, the
ventilation system was able to bring the attic temperature very close to
ambient during the time that the water was being applied, and even for a
short time after the water had been turned off and evaporative cooling
was happening.

If I had the time, and a backhoe, I'd create a water storage reservior
in the ground near my house, probably lined with concrete, maybe
insulated, and circulate water from that reservior to my roof and back
again, storing heat energy to heat my home in the winter. *I'd put pipes
in my driveway and melt the winter snow with this heated water, and by
next spring the water would be cold and ready to absorb the next
summer's heat.

Anyone know how much water would be necessary to store enough heat to
heat a typical house in the winter? *Say, in Chicago, Detroit, Buffalo
or Toronto? *Say if you started with a water temperature of maybe 175
degrees and by the end of the winter it was down to 70 degrees? *(no
heat pump involved that is).



Dear HG-

What you're talking about is a TES (thermal energy storage) via a TER
((thermal energy reservoir).

http://en.wikipedia.org/wiki/Thermal_energy_storage

Collecting heat (or cold) and using it hours later or perhaps a over a
couple of day is very doable
but "moving" energy from one season to another would require very
large volumes of water.

I'd be surprised if it was economically feasible.
(I haven't done the calcs so my comments are based on an educated
guess)

This sort of thing was done YEARS ago before the invention of
refrigeration cycles...... the "ice house" concept.
Ice was collected and stored in an insulated structure for use later
in the year.

Water is a wonderful substance, useful for all sorts of processes.
For thermal energy "storage"..... raising a pound of water 1 def F
takes one BTU.
Turning water into ice is even better..... taking a pound of water to
(or from) ice takes about 142 btu.
That's why ice works so well to cool things.

So if you need a couple 100,000 btu's, you'll need a couple 10,000
pounds of water
(if your operational temp change is 10 degrees).

Of course changing the water temp more means you need less water
but there are limits to the operational temperature change and there
are also desired operating temps.

The University of California at Irvine had an air conditioning problem
back in the 1990's they needed to solve.
The summer afternoon peak cooling load was higher than the capacity
of the steam plant's chiller.
Rather than add more capacity to the plant, the campus chose to build
a TES/TER to address the problem.

A water tank water (~5 million gallons) was built to hold water that
could be chilled during off peak hours.
The cold water was used to supplement the campus chilling capacity
during peak afternoon demand.

About 53,000 ton-hours of cooling was shifted to "off peak" and the
campus was able to take advantage of "night time" electrical rates.
The system cost about $6,000,000 and reduces the yearly electric bill
by about $500,000.
An additional benefit was the avoided the cost to upgrade the chiller
capacity.

I'm not sure it would be practical for a single family home but its
not totally far fetched.

cheers
Bob