3 ms·

This is really cool! Does anyone understand the physics well or have a reference? I don’t fully understand why there’s a maximal power point.

tuatoru 4y ago
Power is voltage times current. With an open circuit (infinite resistance load), the voltage is a finite number but current is zero, so power is 0. With a short circuit (zero resistance load), voltage is 0 and current is some finite number, so again power is 0. With loads in between short circuit and open circuit (i.e. some finite nonzero resistance), both voltage and current are nonzero, so nonzero power is produced. One or more of those load points will result in a maximum in the power production curve. With real PV cells and real light, one point is the maximum at any given time.
- aqfamnzc 4y ago
  Seems like you are implying there's a non-real solution to that curve's maximum as well, which makes sense. Obviously directly these aren't useful, but I wonder if there are any situations where imaginary solns might also be helpful to know?
  - wiml 4y ago
    I think they're just hedging for the fact that there could theoretically be multiple local maxima, but in practice the current-voltage curves of PV panels are boringly well-behaved and so there's just one maximum. (In electronics if you find complex numbers they're usually being used as shorthand for complex exponentials via a Laplace transform — in this case, an imaginary or complex solution would mean that the PV panel has some kind of weird resonant behavior — again, unlikely to be the case for any panel you actually have.)
Johnythree 4y ago
A crude explanation is that solar panels are basically a Constant Current source. They have a maximum Voltage when open circuit, and a maximum Current when shorted. And the maximum power point is somewhere between those two extremes. Exactly where depends on various conditions, like the strength of the sunlight (clouding, etc).

tuatoru 4y ago

Power is voltage times current. With an open circuit (infinite resistance load), the voltage is a finite number but current is zero, so power is 0. With a short circuit (zero resistance load), voltage is 0 and current is some finite number, so again power is 0. With loads in between short circuit and open circuit (i.e. some finite nonzero resistance), both voltage and current are nonzero, so nonzero power is produced. One or more of those load points will result in a maximum in the power production curve. With real PV cells and real light, one point is the maximum at any given time.

aqfamnzc 4y ago
Seems like you are implying there's a non-real solution to that curve's maximum as well, which makes sense. Obviously directly these aren't useful, but I wonder if there are any situations where imaginary solns might also be helpful to know?
- wiml 4y ago
  I think they're just hedging for the fact that there could theoretically be multiple local maxima, but in practice the current-voltage curves of PV panels are boringly well-behaved and so there's just one maximum. (In electronics if you find complex numbers they're usually being used as shorthand for complex exponentials via a Laplace transform — in this case, an imaginary or complex solution would mean that the PV panel has some kind of weird resonant behavior — again, unlikely to be the case for any panel you actually have.)

Johnythree 4y ago

A crude explanation is that solar panels are basically a Constant Current source. They have a maximum Voltage when open circuit, and a maximum Current when shorted. And the maximum power point is somewhere between those two extremes. Exactly where depends on various conditions, like the strength of the sunlight (clouding, etc).