On Tuesday, April 22, 1997 at 2:00:00 PM UTC+7, Joseph Bartlo wrote:
EBurger wrote in article
. ..
Alex Nikolaev wrote:

Any one help convert W/m2 to mJ/m2 for solar radiation?

If by "mJ" you mean millijoules, there's a problem in that Watts are
Joules per second, measuring power (energy/time) and Joules measure energy
itself. You could multiply W times the duration of the solar radiation in
seconds to get J, then by 1000 to get mJ.

My apologies if "mJ" means something else besides millijoules :-).

Not everyone is aware of all our conventions, especially if from
elsewhere (?). I think Alex meant Megajoules (typically used
for solar radiation because they produce comfortable base 10
numerical values). If so, he should be aware that milli refers
to 1000 parts of 1 (eg, 1 g = 1000 mg), and Mega means
millions (1000000 J = 1 MJ).

A 'Watt' (W) is a 'Joule' (J) per second (sec). Thus,

1 W = 1 J/sec

No power & energy conversion is possible, as you state, but

E = Int(t1,t2) P dt , Int representing integral from t1 to t2

Average solar energy fluxes during sufficiently small periods
(e.g. 20 minutes) are sufficient to estimate daily solar energy
amount using sums during the periods. E.g., suppose global
solar energy flux averages centered at shown times are :

10:10 500 W/m^2
10:30 530 W/m^2
10:50 270 W/m^2

Time period is 20 min = 1200 sec then total solar energy
amount during the hour is

E = (500)(1200) + (530)(1200) + (270)(1200) =
1560000 J = 1.56 MJ/m^2

Such can be done for an entire day, solar energy amount for
clear summer days being near 30 MJ/m^2 (a nice, comfy
number)


Joseph

Okay..that is make sense