These homes use a concrete slab with a
compacted sand bed under the slab for the storage of solar heat. The
sand bed typically extends under all of the house and is typically about 2 ft thick.
The sand bed and slab provide a large mass for storing heat. The sand
bed outer edges and bottom are insulated to prevent heat loss to the
outside. Heat is delivered to the house directly from the slab/sand
bed into the living area.
The claims made for the system are
that compared to a system that stores heat in a water tank, it can 1) collect
heat more efficiently, 2) store more heat at a lower cost, 3) be cheaper to
build, 4) and deliver a higher solar fraction with the same collector area that
an system using water storage.
The system certainly has some simple
and appealing features, but I can't help but wonder what its like to live right
on top of the thermal storage and have your living space coupled directly to it.
It seems like there is always going to be a compromise between wanting a fair
amount of temperature swing in the storage (to store more heat), and a desire to
keep the storage temperature within a fairly narrow range for occupant comfort. It
also seems like the heat loss area outward and downward is large compared to
water storage.
It would be really nice to see actual data on real homes that use this system to
address both the performance and comfort issues.
The limited feedback I have received
from people living in sandbed storage homes has been uniformly good -- the owners
I've heard from like them and feel that they are a good way to go.
It would be oh so nice to instrument
one (or more) of these homes and get a better understanding of the performance.
I''d be happy to loan data logging equipment to anyone who is
in a position to do this.
