Measuring solar potential alongside actual - is it possible

[ianganderton]

Please excuse what might be a very dumb newbie question but I was wondering

Is it possible to measure (and record) what a solar array could possibly have delivered over time? If so how?

It seems that the normal way of measuring solar output (in a vehicle setting anyway) is through a shunt attached in line to the battery so this is only measuring power used for charging. Anything not used is unseen.

I'm interested to learn what I can and being able to see what was used against what was possible would be really interesting.

Thanks in advance

Ian

 

[45North]

If you're just interested in the theoretical solar available you could check online for the "insolation" in your area.

 

[ianganderton]

If you're just interested in the theoretical solar available you could check online for the "insolation" in your area.

I've had a look at that data but it's not the same as a direct comparison between what my array could have delivered (with my components and location) and what it actually did.

 

[Dzl]

Please excuse what might be a very dumb newbie question but I was wondering

Is it possible to measure (and record) what a solar array could possibly have delivered over time? If so how?

It seems that the normal way of measuring solar output (in a vehicle setting anyway) is through a shunt attached in line to the battery so this is only measuring power used for charging. Anything not used is unseen.

I'm interested to learn what I can and being able to see what was used against what was possible would be really interesting.

Thanks in advance

Ian

This is an interesting question, I'm curious to learn more.

I suppose one half of the equation would be figuring out a way to measure and log 'irradiance' at your PV array location. Or am I misunderstanding what you are trying to measure?

 

[svetz]

...Is it possible to measure (and record) what a solar array could possibly have delivered over time? If so how?...

Not perfect, but as long as one isn't shaded by a cloud I've found good results comparing my array to the solar radiation from a nearby weather station. The technique is discussed here (What about real life?), the capture and recording software is discussed here and sample data in post #26.

Update: With some luck, hopefully a neighbor has already been recording it for you for years and is available online via a wunderground PWS.

 

[ianganderton]

This is an interesting question, I'm curious to learn more.

I suppose one half of the equation would be figuring out a way to measure and log 'irradiance' at your PV array location. Or am I misunderstanding what you are trying to measure?

I'll try and explain my thoughts, I've actually just stumbled across a possible way of doing it.

As you know I've been looking at the Electrodacus SBMS0 and DSSR20 units. One of the DSSR20 versions has a diversion function.

The SBMS0 records both PV in and power out of the battery. When the battery is full it turns off the DSSR20 (it seems it works something like a solid-state relay) but then the diversion model can divert the now unused power to another use, e.g. a water heater.

If that "extra" redirected power was measured (via a shunt) then that would give really interesting data.

Power used to charge batteries + additional redirected power = total potential PV

If a water heater option wasn't available maybe a power sink similar to those used for draining batteries in testing could be used to ensure all the data was collected.

 

[Dzl]

Ah okay, I see what you are getting at. Something like this water heating element maybe + a third shunt and some way to record and track the data.

 

[ianganderton]

Not perfect, but as long as one isn't shaded by a cloud I've found good results comparing my array to the solar radiation from a nearby weather station. The technique is discussed here (What about real life?), the capture and recording software is discussed here and sample data in post #26.

Update: With some luck, hopefully a neighbor has already been recording it for you for years and is available online via a wunderground PWS.

Interesting, that's a good rabbit hole for this afternoon

There is a wunderground station with solar within a km of here too!!

 

[ianganderton]

Ah okay, I see what you are getting at. Something like this water heating element maybe + a third shunt and some way to record and track the data.

Yeah exactly

A fan over a heater like this tester is using. This one is good for 180W



It wouldnt be too hard to make a Arduino Data logger, maybe even record panel temperture too

 

[erik.calco]

Much easier to apply to FedEx, where I can say they could of possibly delivered my bus bar cover by now:

 

[svetz]

...There is a wunderground station with solar within a km of here too!!

So, what did you find?

 

[tictag]

It wouldnt be too hard to make a Arduino Data logger

I actually made one recently to log a power drain I was suffering on my car (battery would go flat after a few days). I used this and this connected to a midi-fuse, then plugged it in to each fuse to log power loss. Turned out my tracker was f****d.

 

[erik.calco]

I actually made one recently to log a power drain I was suffering on my car (battery would go flat after a few days). I used this and this connected to a midi-fuse, then plugged it in to each fuse to log power loss. Turned out my tracker was f****d.

We definitely going to need an Automation / IoT section of the wiki.

 

[tictag]

Always happy to help

 

[efficientPV]

If you have a small unused panel connect that to a resistor and measure voltage over time. Choose a resistor low enough so that panel current can never get near the power point voltage. Set a pot to read an even number 10V or 1V on the brightest day. This will give you a relative number of what power can be created. Very useful in switching in loads when there is sufficient power to operate them.