Posted by David Delaney on May 16, 2005, 12:33 am
Article and drawing at
This house may heat itself in a cold climate without purchased energy.
Although shown as 100% passive, in practice the house would have a fan
to blow hot air into the house from the heat store, and a thermostat
to control the fan for automatic temperature regulation of the
habitable space. Manually operable dampers on suitable openings
between the heat store and the habitable space would allow for manual
temperature regulation during a failure of fan power.
The design of a suitable thermal mass for the heat store may be seen
at Free-standing column of stones for a heat store without fans,
The house has only one set of dampers on the air heater side, at the
bottom of the air heater. These passive plastic film dampers prevent
back flow of cold night air into bottom of the heat store. No dampers
are necessary at the upper opening into the heat store from the air
heater. The heat trapping structure of the upper opening will prevent
leakage of the hot light air above into the cold heavy night air
below, as long as the air heater, or the house, or both, are
reasonably air tight.
Upper dampers, if present would swing into the heat store during
operation, where their operation would be inconvemient to verify, and
would allow only awkward access for repair. The lower dampers swing
into the air heater, where they should be easily visible, and allow
easy access for maintenance, if the air heater is large enough for
easy entry. The lower opening into the heat store from the air heater
is via a cold trap, so that air on the inside of a damper made cold at
night by conduction through the thin plastic film will not slide
across the floor of the air heater and onto the floor of the inhabited
Posted by Anthony Matonak on May 16, 2005, 6:07 am
David Delaney wrote:
Looks like a variation of Nick's famous solar closet.
If I were to do this, I think I would do it somewhat differently.
For instance, I wouldn't focus so much on the passive aspect and
would use more fans to move air. Fans aren't expensive and the PV
panels to run them wouldn't have to be huge. This would allow for
much more flexibility on collector placement. I could, for instance,
place the collectors on the roof and free up the south wall for
passive lighting, ventilation, views or entrances.
Next, I would run some numbers on costs vs storage of various
materials. You are using "rock" but perhaps something else, say
scrap iron or water, is cheaper and stores more heat.
Being the kind of guy I am, I'd also include instrumentation.
Perhaps a few thermocouples placed in strategic locations all
connected to displays/loggers somewhere easy to read.
Lastly, I'd make sure there was a very good method of dumping
heat in the summer months. Might be good for slow cooking though.
Posted by News on May 16, 2005, 8:50 pm
Water? Getting like Nicks solar closet. 4" plastic soil pipes filled with
water, vertical from floor to ceiling spaced so that air has to work its way
around the pipes. Hot water rises quite quickly, so the tops of the pipes
would be hotter and this is were the heat is drawn off to fan into the
Stones is maintenance free. Eventually plastic pipes will fail, but filled
with water, does store more heat, so will be more efficient. The plastic
pipes could be slotted into a custom made frame that wheels out to replace a
pipe if necessary.
Dump heat from the thermal store? Enough insulation would be good enough to
keep the heat away, and as Nick does, have finned tube copper pipe to heat a
cylinder of hot water using gravity circulation.
Posted by Anthony Matonak on May 17, 2005, 1:25 am
I wonder what the reason for plastic pipe failure would be and
how long it would take to fail in this application. I know UV
light does a number on most plastics but in this design the
pipes would be out of direct sunlight. Potentially the temps
inside the "closet" could reach the boiling point of water so
it would be important to have pipes that could take that kind
of heat. This is, of course, not a problem with rocks.
Posted by News on May 17, 2005, 10:30 am
The problem with rocks is that they consume space, unless under the house in
a well insulated crawl space. Or, above the house in the attic space -
better for passive circulation up there - there again superinsulated around
them, top bottom and sides, so the heat in the mass in summer does not
radiate down from the ceiling. The structure would need to be strong
enough to support the load. David is talking about a concrete building, so
it would be easy to design in the strength. The great thing about
rocks/pebbles is that they are maintenance free.
I would always prefer to have a solar heater/panels on a roof, to keep the
walls free. The roof is there doing nothing, so use it. I can only see
advantages using the roof, and it has such a large area, and the attic
space. Depending on the size, the attic space need not all be used, maybe
just one side of the space.