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Module Level PV Monitor/Optimization/Rapid Shutdown

Hello, I am Dan from Minnesota, USA. I am new to the OEM site, but am very intrigued by the work that has been done. I am deploying a substantial solar site with Schneider Electric XW+ inverters, MPPT 60-150 charge controllers, 48VDC battery bank, battery monitor and ComBox. I intend to use this to power our property and to utilize as a platform to test add-on monitoring and related devices. I am a Mechanical and Software Engineer, and have much experience with Electronics but am not an EE. I am a proponent of Open Source, and am very excited to see the broad spectrum of OEM projects.

I would like to float the idea of an Open Source PV Module level device with modular capabilities like:

  • PV Module Energy Monitoring (of course)
  • Rapid Shutdown
  • DC Optimization

Very much like what TIGO is doing, but as an Open Source/Architecture suite that can be utilized with any vendor. Also to enable the expansion into new functional capabilities like Curtailment. Some of the motivations behind this are:

  • Module Level Monitoring is very compelling
  • Ability to retrofit Rapid Shutdown in existing installations
  • Optimization can be a value add if expanding/reworking an installation
  • Improve performance of partial shading conditions

There are some big challenges like high DC voltages, certifications and things I can’t even imagine right now. But I wanted to throw this idea against the wall and see what sticks. I look forward to any thoughts the community may have.

As a starting point, here are some high level goals/requirements:

  • Design or source a standard module level device enclosure:
    • Robust enough to handle exterior use, potentially be certified
    • Permit daisy-chaining of modules up to 600 VDC minimum, perhaps 1000 VDC
    • Provide capability to plug in swappable electronics modules
    • Provide ability to mount weather-tight MC4 connectors or PV wire stubs
    • Provide sufficient enclosure volume and connector ports/stubs to accommodate single or dual module versions
  • Module level receiver
    • Suitable to handle dozens, possibly 100’s of modules
  • Enable PV Module level monitoring
    • Swappable electronics module
    • Comparable functionality to emonDC
  • Enable Rapid Shutdown
    • Swappable electronics module
    • Satisfy NEC 2017 Rapid Shutdown requirements
  • Enable DC Optimization
    • Swappable electronics module
    • Solar Edge or SMA style DC optimizers, but open source, usable with any string inverter
  • Develop swappable module to perform Curtailment
    • New concept to eliminate dump loads, or facilitate AC coupling

Ideally, the individual swappable modules above could be integrated into a single module, but new functionality would likely be a piecewise evolution. The pluggable architecture permits easy migration to incorporate new functions and upgrades as the electronics evolve.

Communication between the module level devices and receivers may need to be a mixed bag of technologies, depending on the functional needs and technical implementation constraints. Wireless, Powerline and/or dedicated communication network are all options at this point.