I think a combo of PV panels and solar collectors would generally be the
best solution, assuming you have the sun exposure. Currently PVs are
not very efficient. I don't have any numbers of solar collectors but
I'm pretty sure they can beat PVs several times over.
Since home heating doesn't require electricity, that could be done more
effectively with collectors. The EV and home appliances could be
powered by PVs, to the extent possible.
How much reduction in fossil fuel use would depend on how your power is
generated and how you currently heat. In my case, home heating comes
from natural gas (don't have any A/C) and almost all the electricity
comes from hydro. Thus, the best way for me to reduce my carbon use
(and reduce fracking) is to switch my home heating to a solar collector
system. If your case is, say, electricity from 50% coal and 50% nuke,
where as your heating is natural gas and cooling is electricity, then
you may be better of prioritizing the electricity generation before the
heating.
Either way, the amount of area required to capture kWh-equivalents is
going to be smaller for heating than for generating electricity until we
have better PV technology. So, don't overlook installing collectors.
Peri
------ Original Message ------
From: "Peter Eckhoff via EV" <[email protected]>
To: "Ben Goren" <[email protected]>; "Electric Vehicle Discussion
List" <[email protected]>
Sent: 11-Jan-15 10:21:19 AM
Subject: Re: [EVDL] EV Demand Response - (now Home solar)
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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