Posted by nicksanspam on August 25, 2005, 6:40 pm
And the collector?
You might enjoy distilling wastewater in a multi-effect greenhouse.
Maybe. What's the vapor pressure at your expected max temp?
I was thinking of something simpler than that, kinda like this, in
a fixed font:
| | expansion tank
..... overtemp fluid level
..|.......|.. normal fluid level
| normal path | - overtemp path
| | -
| | - fin tube
| | -
Posted by Q on October 31, 2005, 12:02 am
The whole idea of overpressure and overheating is moot if you use a
drainback type active closed system circulating tap water. This system
uses a drainback tank located inside the heated house area. When the HW
tank set temperature is reached the DT controller shuts the circulating
pump off, the water gravity drains out of the collector into the
drainback tank, and everything is fine. The collectors can stagnate all
they please (even up to 400 deg F) without harm. No glycol to cause high
temperature acidity problems. The next morning the DT controller will
sense when the collectors are hot enough to make more water and start the
cycle all over again. The drainback takes care of any freeze problems.
I had a system running fine through the winters in Nashville TN in the
80's. It would come on to make hot water on a sunny day when the outside
temperature was -10 deg F.
Gulf Coast Solar, Inc.
Posted by Solar Flare on October 31, 2005, 2:36 am
I have been considering this type of system with one big concern
What pump is good for the head presure to get the fluid started circulating?
Pumps are available to produce 30 feet of head but the current draw on them is
high and once siphoning is established, isn't the flow way too high and the
current draw unnecessary?
Does anybody know what happens to the power cinsumption once the head load is
off the pump (siphoning action on the return) ? I won't mind using more power to
get the thing going but to keep it running for hours at a larger current draw
Posted by Q on November 1, 2005, 11:29 pm
I think of it in a larger practical picture. Compared to the energy you are
getting from the sun, what you spend on pump power for 6 to 8 hours/day is
neglible (unless you are using PV to make it). It is equivalent to a couple
of light bulbs. You can put the drainback tank up at a higher elevation so
that the pump doesn't have as much initial head to overcome (equalizing the
hydraulic column). There isn't much reduction in current draw from siphoning
that I've seen. A Taco 08, 09, or 12 model will take care of most
applications. I'd stay with bronze to avoid any galvanic corrosion issues.
Gulf Coast Solar, Inc.
Posted by Solar Flare on November 2, 2005, 12:06 am
Well I may just run a glycol system in a small loop to the heat retention tank
but I haven't considered the costs tradeoff yet.