Hydronic solar thermal?
Has anyone ran across a design guide for passive solar thermal heating and cooling using water-antifreeze as mass in pex metal radiant roof and/or floor-wall lines? I’m thinking solar thermo-siphon vs a mechanical pump. The goal is to move conditioned hot-cold water from the collector (pex) runs on a roof or ground pod to the lines in the mass floors-walls without the use of electrical power or PV loads with this branch of the system, or more effectively use solar gain and loss in a circulating water mass system in addition to solid mass gains through windows-walls-floors taking down hvac loads to a min or zero.
If the system cost was low just running pex utilizing solar heat gain and night time radiation cooling that would be ideal. If I need a pump and/or storage tank that is a second choice. If I need a heat exchanger add on I want to be able to add that after I verify the mass effect and hvac loads without it, and for possible DHW integration.
I’m hoping to find a design guide and not have to stay up all night developing it myself 🙂
Here is an example video: https://www.youtube.com/watch?v=mRM5nJ83-n4
And project (scroll down to roof): http://www.michaelfrerking.com/projects.html
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Replies
Terry,
As far as I know, since the early 1970s, every possible variation of solar hydronic heating system has been invented, built, improved, and in some cases abandoned.
These systems can work, but they have two flaws: (a) the value of the collected heat is so low that it doesn't justify the high equipment cost required to collect it, and (b) a well-designed passive solar house doesn't really need any heat on sunny days -- it only needs heat on cloudy days, but your type of system can't do much on cloudy days.
I'm sure other readers have different opinions. But the best bang-for-your-buck designs are still the same we preach here at GBA: airtight construction, superinsulation, and passive solar orientation.
https://www.greenbuildingadvisor.com/blogs/dept/musings/solar-thermal-dead