Saturday, November 21, 2015

New Version of Renewables Alternativ Powersystems Simulation (RAPSim) Supports Your Own Model Implementations

We are proud to annouce a new release of our Renewables Alternativ Powersystems Simulation (RAPSim) software. The current version 0.92 is now available on the sourceforge page of RAPsim.

It has been some time since the RAPSim software had been presented at  the IEEE Innovative Smart Grid Technologies Asia and also announced in this blog.

Renewable Alternative Powersystems Simulation
Since then we improved the graphical user interface to allow a smooth interactoin between user and simulation system and improved the software structure to allow for an easy extension of the simulator with your own models. At the 12th Workshop on Intelligent Solutions in Embedded Systems we presented this feature in detail. The main steps are:
  1. Select the correct abstract class and define general attributes. A structure of abstract models is provided to handle all the interaction with the objects and the other simulation parts. The user has to name, describe the model and add an appropriate icon for the model. 
  2. Model parameters must be defined for being available in the GUI. The provided data type deals also with complex numbers. Dependent on the type of implemented model the user can define which variables are editable and visiable. This is also the place to set initial values. 
  3. Define the update procedure. This is the main part of the model implementation, meaning the mathematical part is done here. This includes also the possible allignment of data from an external source, like a file, with the simulation time. 
For details about model implementation please see the paper on this topic which was presented at the WISES 2015:

M. Pöchacker and W. Elmenreich. Model implementation for the extendable open source power system simulator RAPSim. In Proceedings of the 12th International Workshop on Intelligent Solutions in Embedded Systems (WISES'15), pages 103–108, Ancona, Italy, October 2015.

and the RAPSim introduction paper:

M. Pöchacker, T. Khatib, and W. Elmenreich. The microgrid simulation tool RAPSim: Description and case study. In Proceedings of the IEEE Innovative Smart Grid Technologies Asia (ISGT-ASIA'14), Kuala Lumpur, Malaysia, 2014. IEEE.

Sunday, November 15, 2015

Photovoltaics Energy Payback Time

Photovoltaic systems are great in producing clean energy without CO2 emissions. A question that remains however, is the amount of energy invested into production and transport of the materials, cells and panels. To answer this question, we had a look into the annual Photovoltaics Report of the Fraunhofer Society (German: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V.).

To give a short summary: The energy payback time for current modules is around one to two years. Considering a lifetime of 20 years, this means that photovoltaic systems are quite effective in providing clean energy. The energy payback time depends mainly on three parameters: (i) the  material usage for the system, (ii) the effiency of the cells and panel, and (iii) the irradiation striking onto the panel. Regarding the first aspect, the report shows that material usage for silicon cells went down by a factor of 2.5 over the last ten years due to increased
efficiencies and thinner wafers. Efficiency is improving slower, currently the best multicrystalline modules provide an efficiency of 18.5%, panels with monocrystalline cells a 22.9% and upcoming thin film technologies have a range between 10.9% and 17.5%.

The largest influence for the energy payback time currently is the place where you put your module: In regions with an annual irradiation of around 1000 kWh/m2 - this is basically the value for PV panels installed in Germany, they energy payback time is 2 years, while in sunny areas, the annual irradiation can be double or more, leading to an energy payback time of around 1 year.

Energy payback time for typical PV systems in different regions of Europe

Sunday, October 4, 2015

Call for Papers on Optimization of Photovoltaic Power Systems

The Hindawi Jounral of Engineering is publishing a special issue on optimization of photovoltaic power systems. Journal of Engineering is a peer-reviewed, open access journal that publishes original research articles as well as review articles in several areas of engineering.

PV generation system is one of the most popular uses of direct solar energy and its installation is rapidly growing because it is considered as a clean and environmentally friendly source of energy. The primary obstacle to increased use of PV systems is their high initial cost. Currently, many research works are carried out focusing on optimization of PV systems in order to reduce the capital cost of the PV system without affecting its reliability. The optimization of a PV system means that the system parameters such as number of PV modules, capacity of storage battery, capacity of inverter, and PV array tilt angle must be selected optimally. In addition, diesel generator and wind turbine capacities must be optimized in case of hybrid PV systems. Moreover, the optimization term includes the electronic features that maximize the yield of these systems such as sun trackers, MPPT, and smart inverters.

This special issue aims to discuss the recent developed and contribution of photovoltaic system optimization science.

Potential topics include, but are not limited to:
  • Modeling and characterization of photovoltaic systems
  • Optimal sizing and installation of standalone photovoltaic system
  • Optimal sizing of hybrid photovoltaic systems
  • Optimal sizing of grid connected photovoltaic systems
  • Optimal placement and management of photovoltaic systems in power system
  • Power electronics for photovoltaic system
  • Sun trackers
  • MPPTs
  • Solar inverters
  • Solar chargers
  • Photovoltaic field performance assessment
  • Modeling of solar radiation

Authors can submit their manuscripts via the Manuscript Tracking System
Manuscript Due:    Friday, 29 January 2016
First Round of Reviews:    Friday, 22 April 2016
Publication Date:    Friday, 17 June 2016

Lead Guest Editor

Tamer Khatib, An-Najah National University, Nablus, State of Palestine

Guest Editors

Wilfried Elmenreich, Alpen-Adria-Universität Klagenfurt, Klagenfurt, Austria
Azah Mohamed, National University of Malaysia, Bangi, Malaysia
Suvash Saha, Queensland University of Technology, Brisbane, Australia
Hussein Kazem, Sohar University, Sohar, Oman

Monday, September 28, 2015

Interoperability Between Smart and Legacy Devices in Energy Management Systems

Energy management systems can help to decrease energy consumption by giving user feedback or by directly controlling devices. Smart appliances create a network of devices that can be addressed and controlled via a defined network interface. However, legacy devices will establish a significant portion of a system’s power consumption and, therefore, need to be included into the management system. We propose an open architecture to integrate smart and non-smart devices by using smart plugs and non-intrusive load monitoring methods. Devices are connected either as (i) smart appliances via a fieldbus or wireless network, (ii) legacy devices connected to a smart plug, or (iii) other legacy devices being detected from a time sequence of power consumption values, which are disaggregated into the power draws of different devices. At a service layer, device properties are presented in a unified way including a machine-readable description of their features and properties. The data layer provides an abstract representation of data and functionalities. It connects to the application layer where different applications can access the data. The system supports mechanism for service discovery, service coordination, and service and resource description.

D. Egarter, A. Monacchi, T. Khatib, and W. Elmenreich. Integration of legacy appliances into home energy management systems. Journal of Ambient Intelligence and Humanized Computing, 2015.

My talk at Workshop Energieinformatik 45. GI-Jahrestagung "Informatik, Energie und Umwelt":

Wednesday, August 19, 2015

Mjölnir: The Movie

Because of the great interest in Mjölnir, we decided to maka a short introduction video providing a walk through the system.

Find out more about the idea behind the system in

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.

or download the software at

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.

Monday, July 13, 2015

Research Scholarship in the Field of Energy Management and Technology

The scholarship will support a scientific project to be done at the Alpen-Adria-Universität Klagenfurt (for example as part of a dissertation).

Applicants must
  • have a completed master or diploma degree
  • Austrian citizenship or analogous according to § 4 StudFG (EU citizenship)
  • the average monthly additional income during the scholarship may not exceed the amount of € 679, - (net)
  • not have at an active employment contract with Alpen-Adria-Universität Klagenfurt during the scholarship
  • target a scientific project within the topics of the research cluster energy management and technology (e.g., smart grids) to be done at the Alpen-Adria-Universität Klagenfurt

How to apply

submit a single PDF document no later than August 16 2015 to with
  • project description (English, max. 3 pages)
  • research methodology
  • time plan
  • CV publication list
  • Support letter from supervisor
  • Leaving certificate of the respective field of study (eg Master certificate)
  • Proof of citizenship
  • Affidavit that the specified income level is not exceeded

For detailed information, visit

Thursday, May 7, 2015

MJÖLNIR - The Open Source Energy Advisor

The interface 0.2
We are glad to announce the stable release 0.2 of our open source energy management system at
Mjölnir provides an open platform where different energy consumption  feedback mechanisms can be implemented and assessed.
The system is one outcome of the MONERGY project, an Interreg research project that explores the use of home energy management systems to foster alteration of consumption patterns and achieve better utilisation of local energy sources. In particular,  we addressed residential settings in Carinthia (Austria) and Friuli-Venezia Giulia (Italy).
We identified common electrical devices and analysed the penetration of renewable energy [1], as well as user's attitude towards smart homes [2]. A measurement campaign was then carried out in 8 selected households, to track power consumption of individual loads at 1Hz for over 1 year. Main outcome was the GREEND dataset [3], openly available here
The energy advisor widget
The dataset was then analysed to gain further insights into energy consumption behaviour in the regions [4]. In particular, policies were formulated to improve energy efficiency, namely: i) shedding of standby losses, ii) postponement to off-peak periods, iii) replacement with more efficient appliances, and iv) operation curtailment.
An estimation of benefits yield by those policies was computed using data from the GREEND dataset, which showed a potential of up to 34% of savings. However, while these policies have a general validity, their benefits can be extended to a larger area by exploiting the functionalities of the Mjölnir framework. To this end, we implemented an energy advisor widget which displays the list of advices and allows users for acceptance and rejection. Each candidate advice is computed based on actual device usage events and energy costs, while a limited number of advices is returned based on user's preferences [5].
The MJÖLNIR system is part of a larger solution consisting of:
  • an aggregate power meter, measuring active power, such as the YOMO open hardware meter [6]
  • an appliance-level monitoring system, such as the OpenEnergyMonitor [7], or a load disaggregation unit [8]
  • the energy management system, consisting of a RESTful webservice and dashboard (Mjölnir) and a mobile application [9]

We expect the tool to be beneficial for both individuals and researchers carrying out field tests on persuasive technologies, whose contribution is particularly encouraged.


  1. A. Monacchi, W. Elmenreich, Salvatore D'alessandro, and A. Tonello. Strategies for domestic energy conservation in Carinthia and Friuli-Venezia Giulia. In Proceedings of the 39th Annual Conference of the IEEE Industrial Electronics Society (IECON 2013). IEEE, November 2013.
  2. T. Khatib, A. Monacchi, W. Elmenreich, D. Egarter, S. D'Alessandro, and A. M. Tonello. European end-user’s level of energy consumption and attitude toward smart homes: A case study of residential sectors in Austria and Italy. Energy Technology & Policy, 1(1):97–105, 2014.
  3. A. Monacchi, D. Egarter, W. Elmenreich, S. D'Alessandro, and A. M. Tonello. GREEND: An energy consumption dataset of households in italy and austria. In Proc. IEEE International Conference on Smart Grid Communications (SmartGridComm'14), Venice, Italy, 2014.
  4. WiTiKee and Lakeside Labs. Validation and analysis of results. Monergy 4th project deliverable, 2015.
  5. 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.
  6. C. Klemenjak, D. Egarter, and W. Elmenreich. YOMO - The arduino based smart metering board. In Proc. Energieinformatik, Zurich, Switzerland, 2014.
  7. OpenEnergyMonitor
  8. D. Egarter, V. P. Bhuvana, and W. Elmenreich. PALDi: Online load disaggregation via particle filtering. IEEE Transactions on Instrumentation and Measurement, pages 1–11, 2014.
  9. A. Monacchi and W. Elmenreich. Insert-coin: turning the household into a prepaid billing system. In Poster Abstract, 5th ACM Workshop On Embedded Systems For Energy-Efficient Buildings. ACM, November 2013.

Sunday, April 12, 2015

European NILM workshop 2015 in London

I'm really happy to here that there will be a Second European Workshop on Non-intrusive Load Monitoring this summer.
The event was announced from Oliver Parson, an organizer of the Workshop, as follows:

I'm really excited to announce that the Second European Workshop on Non-intrusive Load Monitoring will be held on 8th July 2015 at Imperial College London. The workshop is the follow up to last year's NILM @ London workshop, which provided the first European venue which brought together both academics and companies with an interest in energy disaggregation. Updates and registration information can be found at the new website:

Some important information:

When: 8th July 2015
Where: Imperial College London, UK
Cost: Free
Objective: To provide a European venue for disaggregation researchers to discuss recent developments in the field and fuel future collaborations

This workshop will have a more technical focus than the first workshop, and will feature a keynote from Mario Bergés in the morning and a technical session of invited talks in the afternoon. Furthermore, we're inviting all attendees to bring a poster on a topic of their choice, which could be a recent piece of work, their company's current direction, or even an invitation for collaboration on a joint project. Last, we're hoping to live stream the event online for anyone who can't be there in person, though this is a little experimental!

For more information please visit!