re: novice questions
25 mar 2001
>i've thought about adding solar systems to our house for a long time,
>but this is my first day of actually doing some investigation.
welcome to the club :-)
>we live southern pa in a brick, ranch style house. the charts show our
>area receives about 4kw/sq. meter/day.
from your email address, perhaps you are closer to phila than harrisburg.
january is the worst-case month for solar house heating around here. nrel
says the average outdoor temp is 30.4 f, and 3.3 kwh/m^2-day falls on a
south wall and 2.0 on a horizontal surface, and a 1-axis, e-w horizontal
axis tracker can collect 2.3 kwh/m^2 (729 btu/ft^2) on an average day.
professional engineer howard reichmuth calls this beam sun "gift-wrapped"
because it can be concentrated for higher temperatures on smaller targets
and it arrives over a short time, which reduces the heat loss from the
target to the outdoors. around here, most of the sun arrives at a low angle
in wintertime, less than 30 degrees elevation at noon on 12/21, and it
mostly arrives from the south. southeast at dawn and southwest at dusk,
ie south +/- about 45 degrees. it seems to me that a solar trough with an
oversized fixed vs tracking target can collect most of this winter sun.
>what is actually possible with the state-of-the-art in solar power,
>both pv and thermal?
are we talking "state-of-the-art" or "affordable" :-)
>i assume total independence from the grid is not possible for
>a conventional life-style is not possible--i.e., running ones oven,
>dryer, etc. , with an affordable, reasonable installation.
"grid independence" is certainly possible, but perhaps not affordable,
and it probably has a much lower rate of return than other investments.
otoh, professional engineer norman saunders has been designing 100%
solar heated houses in cold cloudy new england since 1944. some have
no backup systems at all, with long track records from data loggers.
>what fraction of a households power requirements can be generated in
>my area? i'm obviously looking for very rough numbers. 10%, 60%...?
>what about cost? i would think simply heating water in the summer with
>thermal devices would reduce the oil bill.
you might realistically and affordably generate 100% of your electrical
power by combining pvs with space and water heating in a 4:1 concentrator,
for instance a 16'x16'x16' tall open linear parabolic reflective lean-to
shed on the lawn with a big insulated tank behind it. put the pvs inside
the transparent 4'x16' 60 c water-filled target trough and make the meter
go backwards, mostly, with a few batteries and an inverter for outages...