kassel university press, ISBN: 978-3-89958-390-8, 2008, 231 Pages
(Erneuerbare Energien und Energieeffizienz - Renewable Energies and Energy Efficiency 7)
Zugl.: Kassel, Univ., Diss. 2007
Content: Decentralized electrical generation units (DG units) are connected to the European network with an increasing number and generation capacity. In the future, this should allow a reduction in the capacity of conventional power plants. This means, however, that ancillary services and other energy supply functions currently provided by conventional power plants will also have to be partially taken over by the decentralized systems. A communication system to which the DG units are connected is an essential requirement for achieving these aims. Load management will also become more important, as the electricity generation of photovoltaic (PV) and wind systems cannot be regulated to the same extent as conventional power plants. Since a considerable proportion of the electricity consumption takes place on the low voltage level, a communication system is also necessary to control the electrical loads installed in the distribution network. However, the management of controllable generators as well as controllable loads must take into account requirements of distribution grid customers, which are mainly private households and small businesses.
In order to achieve these goals, it is essential to standardize and automate all aspects of the communication and building integration so that individual planning is reduced to a minimum. Communication standards must ensure that a common language is used between the various communication partners. Furthermore, it is important to maintain the freedom of the customers regarding their energy consumption, but at the same time to create an incentive for them to contribute to the operation of the supply system. This can be achieved by variable tariffs, which allow the customers to decide how much energy to consume or generate at any time, but also provide a monetary incentive to make a decision that meets the requirements of the supply system. The aggregated reaction of customers within a certain grid region to a certain tariff profile can be predicted robustly by statistical methods. Therefore, a system of variable tariffs can be a reliable tool for grid operators and energy suppliers while being very flexible for individual customers (Concept of “decentralized decision based on central and local information”).
The grid connection represents the technical and legal interface between the public grid on the one side and the customer’s network on the other side. This interface is maintained in the Bidirectional Energy Management Interface (BEMI) concept, which allows for efficient agreement structures between grid operator, energy supplier and customer. The existing metering cabinet is extended using intelligent components. The BEMI system has been successfully tested in laboratory and in simulations. The results of the laboratory tests show that typical household devices can be controlled and switched to optimize the cost based on a variable tariff without affecting the function. Furthermore, the user interface, the load profile measurement, and communication with a BEMI control station have been implemented and proven.
For the development and assessment of BEMI algorithms it is necessary to test the long time behavior of one or a large number of BEMIs within a short time. This is particularly true for the algorithms of the energy provider, who delivers electrical energy to the BEMI customers from a variety of sources. The aim of these algorithms is to aggregate and influence the BEMI customers based on a statistical control; therefore, a large number of BEMI customers has to be taken into account for the assessment of these algorithms. For this reason, a simulation was used to investigate the benefits of a BEMI-based energy management system with a large number of loads and high share of fluctuating generation. These simulations show that the BEMI-based management achieves a reduction of approx. 30 % of the energy that needs to be provided from controllable power plants (under the conditions assumed for the simulation). Simulation of the management with a variation of the share of fluctuating generation shows that energy management becomes ever more important as the share of generation from wind and PV systems increases.
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