My rule of thumb: solar power generates 10 watts per square meter.
There's a fixed maximum of 1300 watts per square meter of sunlight. For large scale technology, assume 10% efficiency. Another 10% from that survives air occlusion, clouds, night, angles, dust/snow cover, buffer battery efficiency, maintenance, breakage, etc. Round down, and we see 10W/m^2 practical output.
Professional quantification of this back-of-the-napkin calculation welcome.
Your rule of thumb is fine. That's roughly how much large-scale solar farms built a few years ago are producing over the course of a year in the California desert. As module efficiency goes up the number will trend up a bit over time in desert locations, but as costs fall more farms will be installed in less-sunny locations as well.
Unlike my sibling poster, I don't expect solar thermal to do significantly better on areal efficiency. The captured-sun-to-electricity efficiency can be higher, but the mirrors need to be spread out more than PV modules need to be separated. Ivanpah covers 14.2 km^2 and generated 719398 MWh in 2017.
I know that Ivanpah has been troubled. I'd welcome annualized areal power figures from a better-performing solar thermal generating project if anyone has them.
> My rule of thumb: solar power generates 10 watts per square meter.
> There's a fixed maximum of 1300 watts per square meter of sunlight.
I'd suggest you qualify your numbers by noting that you're talking specifically about Solar PV.
Solar Thermal appears to offer 3x the kWh/m2 over Solar PV -- and mitigates at least one of your concerns ('night'). That ratio will doubtless change as PVC efficiency improves, but if that 3x factor is accurate now, it'll be a long time before PVCs match or exceed on square metre ratings alone.
Solar Thermal appears to offer 3x the kWh/m2 over Solar PV
I'm wondering at the difference between your measuring "kWh/m2" vs mine of "W/m2". Upshot: averaged over a year, what's the power output? are you including all "off" hours?
Good question. I simply did some googling for comparative efficiency per unit area between PVC and solar thermal -- the 3x factor seemed to come up regularly from different sources. The kWh/m2 was the unit most of those sources were using.
Time of day is very interesting, as PVC's are going to be useful earlier in the day, and solar thermal can still be providing good power output well after sunset. Consequently, in practice, I'd see a combination of both technologies (combined with good storage and grid capabilities, etc) as being most effective way of harnessing sunlight in the short to medium term.
Averaging over a year ... geo / climate variations (eg distance from equator, monsoon cycles, etc) are likely going to affect both technologies similarly.
There's a fixed maximum of 1300 watts per square meter of sunlight. For large scale technology, assume 10% efficiency. Another 10% from that survives air occlusion, clouds, night, angles, dust/snow cover, buffer battery efficiency, maintenance, breakage, etc. Round down, and we see 10W/m^2 practical output.
Professional quantification of this back-of-the-napkin calculation welcome.