Market Garden: A Scalable Research Environment for Heterogeneous Electricity Markets

25 The system transforms this kind of input data and constraint definitions (defined in XML) into a mathematical, constraint optimization problem using a Constraint Programming (CP) approach. Our constraint-solving library “firstCS” [3] offers the necessary primitives and Operations Research (OR) functionality to define and solve the necessary equalities and inequalities resulting from variable tariffs as well as the temporal and capacitive restrictions. The achieved solution consists of two parts: a costminimal schedule of the loads and the according load distribution. Again, the output is in XML format. In particular, for the load distribution the interface standard for meter reading and control, IEC 61968-9, is used. We have chosen this format for easy comparison of the scheduled load with the real energy consumption measured by smart meters. These data in the same format show the difference between target and reality as well as the financial loss compared to the cost-optimal schedule. In order to perform the necessary analysis and perform a comfortable automatic control of the involved devices (causing the loads), the energy management system can run on our own energy management and control gateway. This gateway is a programmable communication device that can take over the role of a gateway for Controllable Local Systems (CLS) to allow electrical devices to be switched based on the current load management. The CLS approach is also specified in the German guidelines for smart metering systems and gateways and the respective protection profile [4]. Additional software modules of our gateway enable demand side integration (eg our smart energy management) and load control. For comfortable use, the gateway offers a unified web-based user-interface on PC, appliances, and smartphones (using HTML5). The solution is an open interoperable gateway having a standardized interface to access certified smart meter gateways (SMGW), smart meters, and other machine-to-machine (M2M) devices. It also supports state-of-the-art home automation and facility control technologies such as digitalSTROM, KNX, ZigBee and 868MHz RF.