When I took a Solar Energy course way back when, my instructor said
there was a "rule of thumb" for solar thermal heating. He said to take
the square footage of the heated **area** and divide by 3 to produce a
storage **volume** estimate. At the time, fist sized rocks were used
to store the heat. Of course insulation, angle of the collectors to due
south, etc. mattered. The idea was to pump a liquid through the
collectors to the storage volume and then have a separate (or 3-way
valve) to direct any heat from the storage volume to pipes radiating
heat under the subflooring.
Recently, I ran a parameterized commercial solar energy program with a
similar system and the system came back saying I needed a 600 gallon
tank for optimum heating. In this case, a liquid is being used to store
the heat instead of rocks or sand.
While not perfect, the idea is that PV will take care of local EV
driving needs and the solar thermal will address a lot of winter heating
needs. The more cloud cover and colder winter temperatures, the less
energy it will provide.
On 1/10/2015 3:09 PM, Ben Goren via EV wrote:
On Jan 10, 2015, at 9:21 AM, tomw via EV <[email protected]> wrote:
His book, Solar Hot
Water Heating, describes (among other systems) using solar hot water
collectors to heat a 2 ft thick layer of sand which is insulated inside the
house foundation with a concrete slab floor on top of it, giving over one
hundred of metric tons of thermal mass for radiant floor heating. Water is
circulated through the sand with PEX tubing, starting around mid August to
heat it up for the winter.
Similarly, the most effective method of cooling for locations such as Arizona
where I am also uses the Earth as an heat sink...and, of course, also similarly
only really make sense for new construction. But, yes -- done right, and you
can live in arctic frigidity in the middle of August for pennies per day. If
whoever built the building had the foresight to do things right....
But the good news is that there's insane amounts of energy available from the
Sun such that simply covering a suitable fraction (and generally a minority) of
your roof space with generic PV panels results in a net surplus. And, if the
grid is available to use as the equivalent of a battery, you can make an
handsome profit that way if you've got available capital to invest. Most can
still make a profit, though nowhere near so handsome and with much more
capital, going off the grid entirely.
b&
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