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I'm installing solar panels (not connected to the grid) in units out in a field for research we're doing that looks like this (this is an outdated image, but I can't find the updated one unfortunately):

Outdated model of the system

I have to safely measure power output from each unit, and each unit has 9 panels with the following specs:

  • Maximum Power: 100W
  • Maximum System Voltage: 600V DC (UL) Optimum
  • Operating Voltage (Vmp): 18.6V
  • Open-Circuit Voltage (Voc): 22.3V
  • Optimum Operating Current (Imp): 5.38A
  • Short-Circuit Current (Isc): 5.86A
  • Operating Temperature:-40°F to 176°F
  • Output Cables: 14 AWG (2 ft long)
  • Maximum Series Fuse Rating: 15A

(The panels are coming from Amazon, so I'm not sure how accurate the specs are, and the link to reference them is at the bottom)

These panels are going into an agricultural field, so my primary concerns are: 1) Not electrocuting anyone, 2) not starting a fire, 3) being able to accurately measure the power coming from each unit.

This is my main plan so far, which I'd like feedback on:

  1. Wire all 9 panels in series to minimize amperage
  2. Use 14 AWG wire to take the power out of the field to some sort of resistive load to use the power
  3. The unit will be grounded using grounding rods
  4. On the circuit, there will be a 10A circuit breaker, a manual on/off switch
  5. The resistive load will be connected to a GFCI
  6. Power will be measured using some sort of Arduino based module

Two notes:

  1. I'm not sure what the best, safest (and if possible, cheapest) way to burn the power from the solar panels is. I was thinking using a space heater since each unit is allegedly only putting out a maximum of 900W and commercial space heaters are rated for 1875W. I know I could ground each unit and not have a load and the power will just discharge, but my understanding is I can't measure that.
  2. On the subject of measurements. Are any of the micro controller compatible power meters I find on Amazon going to be sufficient for this task, or do I need to look for something specific?

This has to be done ideally asap, but definitely before the end of May. Although, again, my main concern is doing this safely first and foremost. I am willing to hold off on measuring the power as long as there's as the primary concern is discharging power safely then figuring out how to measure power. I imagine that would involve routing power to a grounding rod, but I'm not sure.

Any advice and feedback is greatly appreciated, and I am happy to answer any questions.

Solar panel link: https://www.amazon.com/Renogy-Monocrystalline-Solar-Compact-Design/dp/B07JXYTFF7/ref=sr_1_1?dchild=1&keywords=Renogy+Solar+Panel+2pcs+100+Watt+12+Volt+Monocrystalline%2C+2-Pack+Compact+Design&qid=1619041063&sr=8-1

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  • $\begingroup$ this question should be asked at https://electronics.stackexchange.com/ $\endgroup$
    – Pete W
    Apr 21, 2021 at 23:15
  • $\begingroup$ One issue I have with using a space heater is the potential fire. Ensure there is nothing flammable near the heater & that the heat can be dissipated safely, or use another method to dissipate the excess energy. The other thing about using a space heater is, will the heat produced encourage wildlife (mice, etc.) to nest near the source of heat on cold nights? $\endgroup$
    – Fred
    Apr 22, 2021 at 6:16
  • $\begingroup$ Thanks for your feedback. I will go ahead and move this post to the electronics stack exchange. As far as the space heater goes, fire safety I think is going to be the biggest problem. There's no battery so we have no energy storage to shed so it won't be producing heat at night, although, pests could still be a problem regardless. $\endgroup$
    – Omar
    Apr 22, 2021 at 18:55
  • $\begingroup$ Google is your friend It took me one minute to find and two minutes to make sure it did what you wanted. $\endgroup$
    – Phil Sweet
    Apr 22, 2021 at 20:10

1 Answer 1

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Long story short, probably the safest and cheapest way to measure while maximizing the output of the panels is to buy a small inverter which is connected to the internet and logs the data at a cloud, and connect the inverter to the grid.

On the grid almost nobody will notice the excess energy (probably they won't mind either, unless you are on some net metering scheme).

The other option is to connect - to the output of the inverter - some sort electrical resistance heating unit - preferably with twice the required input (e.g. for the 900W install a 2kW), which is properly cooled (maybe with a fan or otherwise)

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