Hi,
I was just writing to introduce myself and our open-source project SolarNetwork. This is an energy management development platform that comprises a client-side device that runs on an SBC (we support Beaglebone) to collect information from devices like solar inverters, charge controllers and kilowatt hour meters. It also has a full cloud repository for persistence, visualisation and analysis, and is great for managing distributed assets like groups of PV arrays. Anyway here is an example of how a SolarNode (our client) can acqurie data from any Modbus device - in this case a thermopile pyranometer that measures irradiance.
http://solarnetwork.net/v4/testing-the-modbus-device-plugin/
Any questions let me know, but it’s another resource for Beaglebone enthusiasts looking into renewable energy projects - Thanks! John