- #1
pincopallino
- 7
- 0
1. We all know that the solar constant is 1350Watt.m^-2, which is related to a unit surface perpendicular to the solar rays. The question is: which is the average solar intensity on the Earth surface?
2. first, the portion of the EArth surface is half the EArth sphere. second, we have to take into account that at different latitudes the solar rays have difference incidence angles.
to calculate the power reaching the surface I have integrated the solar constant over the half sphere, which is the same as multiply the solar constant to the maxiun disc, i.e. pi.R^2, where R s the Earth radius.
to have the average intensity on half the Earth surface I have (solar constant)*pi*R^2/(2.pi.R^2) = half solar constant =675watt.m^2
BUT THE TEXTBOOK REPORTs 610 watt.m-2
3. in your opinion , where is the error?
has anyone a clue?
why the factor is 45% instead of 50%?
thkx
2. first, the portion of the EArth surface is half the EArth sphere. second, we have to take into account that at different latitudes the solar rays have difference incidence angles.
to calculate the power reaching the surface I have integrated the solar constant over the half sphere, which is the same as multiply the solar constant to the maxiun disc, i.e. pi.R^2, where R s the Earth radius.
to have the average intensity on half the Earth surface I have (solar constant)*pi*R^2/(2.pi.R^2) = half solar constant =675watt.m^2
BUT THE TEXTBOOK REPORTs 610 watt.m-2
3. in your opinion , where is the error?
has anyone a clue?
why the factor is 45% instead of 50%?
thkx