Solar production around clouds

[james_reilley]

On cloudless days, the Sense power meter shows my solar production as a nice mound as expected:

In this example cloudless day, the peak production is 11.8kW.

However, when there are intermittent clouds, the Sense power meter shows solar production values that can’t possibly be real…higher production values before and after the clouds pass.

In this example day with clouds, which is the day after the previous day, the peak production is erroneously higher at 13.0kW.

Do other see this anomaly?

BTW, my Sense consumption CTs are clamped on bus bars that service all consumption breakers; my Sense solar CTs are clamped on separate bus bars that service all solar production. My main panel has 2 mail breakers…one used for consumption only, the other used for solar production only.

[ixu]

Reflections!

I shall invest you with the ability to work that one out …

[ixu]

Here’s an effusive link …

Effects Of Clouds On A Solar Panel | New Mexico Solar Group

[james_reilley]

Reflections off of nearby clouds causing my non-shaded PV array to capture more energy…very interesting…I had thought there was a bug in the Sense unit.

Here is another day earlier this summer where my Enphase micro inverters must have been clipping the peaks off and on over the course of 1 hour due to this phenomenon:

[ixu]

This is a very seductive subject to me and I’ve been contemplating this some more, as we’ve done elsewhere (perhaps too much):

Varying goals for solar

It seems the most likely fail points in an inverter are the storage capacitors. Leading up to catastrophic failure there is a likely inverter degradation … particularly with non-micro inverters that are under more capacitor stress. There are some papers out there, e.g. Flicker-PVSC-Cap-Paper-Final.pdf that point to an output voltage ripple from the PWM that is proportional to the bus capacitance. i.e. a failing capacitor makes itself clear. But of course nothing compares to some big data. Lik…

Access to geographically proximate PV arrays is key in terms of doing predictive analysis for cloud motion and determining the consequent actions: “Charge EV now!”; “Pause the laundry”; “Switch to battery charging”; “Spin up the flywheel!” …

With that in mind, if I had a large enough property I’d be wiring up a widely spaced array (minimum of 4 panels I guess) … imagine a property centered on a lot and the “cloud detector PVs” at the four corners of the lot.

The other option is to scout out solar neighbors at some optimal distance (based on “normal” cloud speed = prevailing winds) and give them a Sense and share data!

[Utility-scale PV arrays, btw, are somewhat immune to this “cloud reflection spikes” phenomena for obvious reasons. As @MaheshAtSense has highlighted, many PV households are pushing the majority of their watts to the grid (less than optimal) … while individual households may well be able to time shift usage to exploit more of their PV output, it would seem that at neighbor(hood) scale the efficiencies must improve dramatically. Car sharing + charge sharing.]