Talk:Can rooftop solar alone provide enough heating in the winter?

estimate / draft / musing

physics question: solar panels plus electric heaters: given a particular house size and insulation rvalue, how many degrees difference can be had between inside and outside?

• `30 W/m^2 * 3 Rvalue * 2 = 31.699833 K`
  • i put the 2 based on the assumption that the house's exposed surface area is probably double the area of the solar panels (and that heat losses into the ground don't affect the result too much - is that a bad assumption tho?)
  • 3 Rvalue is my guess for a typical whole house averaging including windows and walls (is this a good assumption or not? look it up, is there something called "whole house R value"? or maybe it's easier to conceptualize with U values because they add up?)
  • maybe i should make a table like "home insulation quality -> max temperature difference that can be sustained by solar panels"?
    • and when the max difference is low (crappy insulation), consider whether a heat pump could increase it a bit?
    • accuracy issues? maybe need to factor more stuff in first? or forget about accuracy, just highlight that it's at least sorta possible to have enough heating with solar panels but requires a lot of stars to align lol

and then factor in some air changes and see how much difference it makes

• assuming we want a 30K temperature difference (i.e. 20'C indoors during -10'C outdoors) and that solar panels averaged over 24hrs give u 30 watts RMS per m^2:
  • `30 W/m^2 = 2.9722 (m / hour) air.density air.isobaric_specific_heat 30K`
    • so in other words, with 2.9722 meter high ceilings and perfect insulation, you can have 1 air change per hour and maintain a 20'C house in -10'C weather

external link for wall Rvalues (doesnt say much about windows tho): https://www.homedepot.com/c/ab/insulation-r-values/9ba683603be9fa5395fab9091a9131f

Elie (talk) 23:52, 28 March 2025 (EDT)