Thursday, July 30, 2015

Building Management with Mjölnir

We recently announced the release of the stable version 0.2 of our open source energy management system Mjölnir at

While the tool targeted so far mostly "disaggregated" device-level energy and power usage, we have now introduced full support for circuit-level measurements (buildings, rooms) which unlocks a considerable potential for further data analysis.
The DIN-RAIL module running the measurement system

As most of energy meters use the industrial automation system ModBus, we have been looking for possible shields to extend our open hardware solution with RS485 communication. We finally selected this RPi hat from Libelium while the meter is the Carlo Gavazzi EM24. The implementation is eased by the Libelium ArduPi library, which makes the C code written for Arduino compatible with the Raspberry Pi. The data is then being sent to our servers through a REST interface.

The overall component shown on the picture is therefore a low cost solution able to retrieve remote measurements via the RS485/ModBus and the USB/ZigBee network. This opens for the future integration of other measurement units, such as water and gas meters.

The support of circuit-level measurements required changes on the Mjölnir system.

The system is now organised in buildings, rooms and devices. A circuit is described by its ID and can be associated to a single building or room.
As usual, the code of the gateway is available on SourceForge, along with the dashboard system.

  1. A. Monacchi, F. Versolatto, M. Herold, D. Egarter, A. M. Tonello, and W. Elmenreich. An open solution to provide personalized feedback for building energy management. ArXiv preprint arXiv:1505.01311, 2015.

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