re: wind and sun resources
7 jan 1998
david b. green confesses:
>i own woodlands... i produce a cord (1 ton) of fire wood for $35 and
>sell it for between $90 to $150. i use the profits to buy propane...
>i have all the renewable heat source that i need, but i prefer propane.
>it is cleaner, my house stays dust free, easier to get up in the morning
>(thermostats) and in general my life is better. all the polemics in
>the world would not make me change.
have you considered heating your house with a dust-free sunspace? that
one-time investment might add floorspace to your house and integrity
to your soul, with no recurring wood-cutting labor. you can even use a
thermostat, and use the sunspace to dry wood quickly while using the wood
to store heat. december is the most difficult month for solar house heating
in sacramento (916), with an average outdoor temperature of 45.3 f, and
an average daily min and max of 37.8 and 52.7. the average amount of sun
that falls on a south wall is 820 btu/ft^2-day.
a 35 cent square foot of r1 bayer urethane plastic film sunspace glazing
with a 10 year guarantee might gain 738 btu/ft^2 over an average 6 hour
december solar collection day and lose 6(80-49)1ft^2/r1 = 186 btu, for
a net gain of 552 btu/ft^2-day.
a 32x32x16' tall house with about 3,000 ft^2 of average r20 walls and
ceiling (a thermal conductance of 3,000ft^2/r20 = 150 btu/h-f) and 1 air
change per hour (240 cfm, about 10x the air infiltration needed for health,
with an effective thermal conductance of about 240 btu/h-f) requires about
24h(70-45.3)(150+240) = 231k btu/day to stay warm, which might come from
420 ft^2 of vertical sunspace glazing on a 32' wide x 12' deep x 16' tall
plastic film sunspace suitable for storing and drying 24 cords of wood,
made from $500 worth of standard commercial greenhouse components.