Has anyone used a heat collector to warm fluid for in floor heating and run it without a pump. I'm wondering if convection would be enough to move the fluid through?
Mody
w* fastpoke
I've not heard of any such attempt. My first thought is that with the usual large amount of tubing looping around flat in the floor there would be too much internal friction to get a thermosiphon flow going. ??? But I could be wrong. It may be practical with a large enough solar collector.
Then there is the issue that hot water wants to rise more than flow down to the floor. ???
What about using a radiator instead of in floor heating. This may reduce the friction. I'm looking for something to keep my off grid cabin a bit warm so we are not starting off from -21C when we get there on a Friday night.
Mody
I'm planning to dabble in solar for our build. I'm going to build a big insulated storage tank in the basement, so I can keep the heat going at night when you really need it. Since I'm already on the roof, I'll rig up a couple photoelectric panels to run a small circulating pump. Once the sun starts to go down, the pump will stop so I won't be circulating cold water from the collector. I'll have to run anti-freeze in a closed loop, since my location in SC gets below freezing sometimes. There's a lot of info on DIY collectors all over the 'net.
Quote from: fastpoke on August 30, 2010, 03:23:58 PM
What about using a radiator instead of in floor heating. This may reduce the friction. I'm looking for something to keep my off grid cabin a bit warm so we are not starting off from -21C when we get there on a Friday night.
Mody
Maybe I'm missing something, but it would seem to me that the only way something like a completely passive hydronic system could work is if the solar collector was below the level of the radiator. So collector on the ground and a radiator at the ceiling. ??? And as Muchcreek points out the system would have to use antifreeze or have a method of preventing a freeze. Such a system would need the RV type, or environmentally friendly type of anti freeze, not regular automotive glycol.
I appreciate how nice it would be to have the cabin warmer than the outside air temp for cold weather arrivals. We frequently find the interior colder than outside when we arrive in the fall through spring. With both the wood stove and the propane wall heaters going we get about 20 degrees rise per hour.
Are you on or off grid? Telephone service? There are remote control systems that use telephone to turn devices on and off.
I think it is a great idea - I was trying to brainstorm a similar idea for my ice shanty.......... passive solar liquid oil heat in the walls and floor :o
I'll could not make the ideas work so far....................(just in plans, did not try any builds)
Here's a thought... some folks run an air collector and use a small fan driven by a small solar panel for air circulation. When the sun shines it heats the collector and runs the fan. For a liquid I believe the power requirements for a pump, especially with a viscous material like cold oil, would require a much larger panel and that might make it less practical.
Perhaps a wall system could be fabricated using a liquid media. The warmer liquid would rise and flow to a radiator system, with a storage tank if desired, as long as the tank or radiator was higher than the top of the collector. A pump would be needed if the radiator or storage tank was below the top of the collector.
I've thought of building a wall air collector for our cabin using a solar powered fan for circulation as mentioned above. But because of the trees to the south I haven't pursued the idea any further than the thought phase.
Maybe some ideas here...
http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm#Passive (http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm#Passive)
and here...
http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm#Distribution (http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm#Distribution)
I would think the only way to not use a pump would be a thermosiphon. I do this on my hot tub BTW.
My better half insisted on a hot tub even during construction without the house PV done. It probably delayed us a year but no one was sore....
We put radient floor heat (pex tubing, boiler) in our northern Minnesota home 28x36 in slab. It only added about $2500.00 dollars to the cost of the slab (not quite 3yrs ago). The heat was wonderful and a huge cost savings for winter heat.
Dave, what are the positions of the collector and hot tub in relation to each other.
If you have a solar hot air system and need to pump the air into the house. If you where to buy one of fhose $350 solar systems @ cosco would you need to have a battery? Or when the sun is out it pumps and when its dark it does not