Actors in many European countries‘ energy system have come under pressure to implement changes in their energy systems. The societal idea is to be at least a well-informed consumer in a transparent system, otherwise a prosumer actively taking part in the energy system and integration of DER and renewable energy sources (RES) generation units at their premises. The low voltage feeders that were initially designed to distribute electricity now have to absorb the feed-in from the ever increasing number of DER and RES units. This development towards a bidirectional, ever more interconnected system is challenging the current structures of the energy system and impacts the system’s security of supply.
Thus, one of the main goals of the entire E-Energy programme was to apply intelligent LV network monitoring and control technologies in order to maintain the high standard of security of supply at distribution level in Germany whilst the share of fluctuating feed-in on low voltage grids from DER and RES increases. One major assumption underlying the design of all E-Energy project states that the small, decentralized systems become more controllable, if the control and metering mechanisms, are organized in a decentralized manner. In fact, one of the major research questions to be answered in the model regions was whether cellular systems actually are easier to manage and whether the technology necessary to implement them exists and is accessible.
The project Model City Mannheim took this assumption as its starting point and developed an entire ICT and energy architecture around the idea. Their “cellular control concept” for electricity grids supports centralized as well as regional connectedness and coordination mechanisms between different parts of the network. It serves to create regional market and grid mechanisms and provides for information security and privacy. It focuses on small-sized, connected, yet self-controlled structures instead of one central network monitoring and management system. The physical energy transmission between the parts of the system can be minimised if necessary and – in a subsidiary manner – the smallest parts of the system try to balance themselves to the largest possible extent. In fact, transmission and distribution losses decrease. Energy systems based on these ideas are more resilient than centrally organized systems, as they are less prone to failures spreading through the entire system. Individual parts of the system can be decoupled for a certain period of time, until the overall system is functioning flawlessly again.
Following the model city Mannheim logic, an energy cell can be considered a self-optimizing energy cycle within buildings, city parts, communities, municipalities or regions. These cells can constitute regional or supraregional cell networks, thereby forming an energy organism.
The moma-architecture’s smallest units are buildings, called object cells, which are connected to the distribution grid. Within the building, the energy manager, or in the model city Mannheim case, the so-called energy butler is the central intelligence that connects home automation and energy management system (EMS) and constitutes the interface to the overarching energy and ICT system. It can schedule and control household applications and decides independently, when to switch on or off an application based on the parameters entered by the customer. The most important factor in the energy management processes is constituted by the current electricity price.
The energy butler only switches on the applications when the end user financially benefits. The butler can act market- and grid-driven, as the price signals it translates into “switch on” or “switch off” signals can include information on current prices on the EEX spot markets, but also represents parameters of the local distribution grid. In fact, the energy butler on the one hand side serves to balance the consumption either to the information it receives from the system or it tries to balance the consumption and generation of a specific premise making use of the prosumer’s consumption applications, storage facilities and DER units. Furthermore, it connects the object cell or the Smart Home to the Smart Grid. The next larger part of the energy organism is the so-called distribution grid cell.
The moma cellular architecture, source: Model City Mannheim, 2012
The distribution grid cell contains about 200 cells as well as agent structures to support grid- and market-driven processes. The agent structures, so called automatons, are ICT based applications that evaluate the data flowing in the system with regard to either markets or the network status. Consortium lead MVV Energy, a South Western German utility, has a patent on the ICT underlying the market and grid agents. The network agent structures are of particular importance for the distributed network monitoring and management approach the moma consortium has chosen. They monitor metering data in their distribution grid cell on real time basis and continually compare the data with given values that indicate the acceptable network load. In case a threshold is crossed and the network load is not acceptable anymore, the grid agent can actively counter the development by sending control signals to the attached object cells. Thus, problems are tackled where they are caused and countered within a short period of time before they affect the next higher level. A CORE-platform enables the integration and connects the grid cells to the distribution grid management in the control centre as well as to the transmission grid. The CORE-platform furthermore connects the local market rules at distribution level to the overriding markets via the marketplace of energies on system cell level. The communication in and between the cells is based on IP or on broad- band powerline.
Overall, the moma field test infrastructure consists of about 300 distribution grid cells which collaboratively form the system cell. On the system cell level, all parts can be monitored and left to control themselves or control signals can be sent. The central intelligence authority at system cell level is constituted by the communication and service platform called “moma-marketplace”. It serves as an interface between the distribution grid cells and the incoming information on market and network developments.
Grid and market agents at distribution cell level can access the market with their respective flexibilities and the market place can compare different options and choose the most cost-effective ones. Furthermore, the cells are connected to the energy markets via the marketplace that can also communicate the network stability.
Apart from master data, all information is managed virtually. Access to further data (e.g. meter data) is given by a registry. A non-discriminatory access point to the moma-marketplace is secured by the operation of the registry on behalf of the distribution system manager (DSO). The DSO does not store the data, but acts as a broker of information sources. The central web portal indicating consumption visualization and the billing system can also be modelled on the marketplace.
Moma’s large scale field test proved that the necessary ICT components which have been developed are reliable in practice. The idea of cellular network architecture that enables a security by design approach to Smart Grids is gaining momentum in Germany and Europe. The federal network regulation authority in Germany endorses the idea of cellular networks and has described it extensively in its paper „Smart Meter and Smart Market“. On a European level, the moma consortium has been very active in the Smart Grid Mandate M 490 process and has contributed to the design of the SGAM model.
Model City Mannheim (Model Region Rhine-Neckar)
Dr. Robert Thomann, MVV Energie AG
Technologie & Innovation
Luisenring 49, 68159 Mannheim