4 ms·

35 is pretty close to 10 when you start at 1300 and prune obstructions. Now address clouds, angles, dust, snow, opacity, malfunctions, storage inefficiencies,

35 is pretty close to 10 when you start at 1300 and prune obstructions. Now address clouds, angles, dust, snow, opacity, malfunctions, storage inefficiencies, panel aging, and chronic optimism. 10W.

chrismorgan 6y ago
Most of that is what the 4–5 useful hours per day figure is supposed to take care of (that’s a year-round thing, too, averaging summer, which may be as much as double that, and winter, which may be half). Hmm… storage inefficiencies? Are you including battery storage and perhaps an inverter in your calculations? I guess that’d account for some loss. I’m guessing also from “snow” that you may be in a place that gets comparatively little sunlight?
- gibspaulding 6y ago
  I wonder if "4-5 useful hours per day" is per sunny day, so you can cut your number in half again for cloudy days.
  - chrismorgan 6y ago
    No, this is from averaging it across the entire year, based mostly on locations in the south of Australia (Gippsland, Melbourne, Adelaide, Ballarat, those sorts of areas), but I looked briefly at other parts of the world also. The idea is then that a panel rated at 250W can produce an average of about 1kWh per day when pointed in the optimal direction and never shaded (but without tracking the sun); the average winter day may get you only 500W, and the average summer day over 1500W, with plenty of variation within those seasons day by day also.
- adrianN 6y ago
  42,339 MW of PV installations produced 39,401 GWh of energy in 2017 in Germany[1], so about 38 days of peak generation, or roughly 10.5% of peak. A square meter of PV panels produces around 150W. So 15W average for a panel in a good location in Germany. 10W/m^2 seems like a good estimate if you want your stuff to work reliably year round. Better locations than Germany would do better of course, and restricting yourself to just summer probably helps quite a bit too (winters are dark and cloudy in Germany). [1] https://en.wikipedia.org/wiki/Solar_power_in_Germany#Statistics https://en.wikipedia.org/wiki/Solar_power_in_Germany#Statist...
  - Retric 6y ago
    Germany is north of Maine, it’s a terrible location for solar power and heavily subsidized. At best they hit a capacity factor of 11.6% in 2018. By comparison the US had a capacity factor of 28% for utility-sized PV plants in 2015, but it’s dropped as less efficient locations have been added. A square meter of PV panels produces around 150W, that’s some low efficiency panels, you can easily hit 200+W/M2 using a high efficiency panel like SunPower Maxeon 3. Solar isn’t a great fit everywhere. So, people really can see wildly different outputs from the same setup based on location. At 28% capacity factor averaging 60+W/M is very possible.
    - adrianN 6y ago
      Thanks for the reference to the 200W panel!

35 is pretty close to 10 when you start at 1300 and prune obstructions. Now address clouds, angles, dust, snow, opacity, malfunctions, storage inefficiencies, panel aging, and chronic optimism. 10W.

chrismorgan 6y ago

Most of that is what the 4–5 useful hours per day figure is supposed to take care of (that’s a year-round thing, too, averaging summer, which may be as much as double that, and winter, which may be half). Hmm… storage inefficiencies? Are you including battery storage and perhaps an inverter in your calculations? I guess that’d account for some loss. I’m guessing also from “snow” that you may be in a place that gets comparatively little sunlight?

gibspaulding 6y ago
I wonder if "4-5 useful hours per day" is per sunny day, so you can cut your number in half again for cloudy days.
- chrismorgan 6y ago
  No, this is from averaging it across the entire year, based mostly on locations in the south of Australia (Gippsland, Melbourne, Adelaide, Ballarat, those sorts of areas), but I looked briefly at other parts of the world also. The idea is then that a panel rated at 250W can produce an average of about 1kWh per day when pointed in the optimal direction and never shaded (but without tracking the sun); the average winter day may get you only 500W, and the average summer day over 1500W, with plenty of variation within those seasons day by day also.
adrianN 6y ago
42,339 MW of PV installations produced 39,401 GWh of energy in 2017 in Germany[1], so about 38 days of peak generation, or roughly 10.5% of peak. A square meter of PV panels produces around 150W. So 15W average for a panel in a good location in Germany. 10W/m^2 seems like a good estimate if you want your stuff to work reliably year round. Better locations than Germany would do better of course, and restricting yourself to just summer probably helps quite a bit too (winters are dark and cloudy in Germany). [1] https://en.wikipedia.org/wiki/Solar_power_in_Germany#Statistics https://en.wikipedia.org/wiki/Solar_power_in_Germany#Statist...
- Retric 6y ago
  Germany is north of Maine, it’s a terrible location for solar power and heavily subsidized. At best they hit a capacity factor of 11.6% in 2018. By comparison the US had a capacity factor of 28% for utility-sized PV plants in 2015, but it’s dropped as less efficient locations have been added. A square meter of PV panels produces around 150W, that’s some low efficiency panels, you can easily hit 200+W/M2 using a high efficiency panel like SunPower Maxeon 3. Solar isn’t a great fit everywhere. So, people really can see wildly different outputs from the same setup based on location. At 28% capacity factor averaging 60+W/M is very possible.
  - adrianN 6y ago
    Thanks for the reference to the 200W panel!