Batteries in Smart Microgrids

Abstract

To counter the effects of global climate change, attributed to the CO 2 emissions resulting from burning fossil fuels for generating electricity and heat, global efforts are being made to achieve an energy transition. This includes that the share of energy generated using sustainable sources (e.g. solar, wind, hydro) should be increased, while the share of energy generated using fossil sources (e.g. natural gas, coal, oil) should be decreased, ultimately phasing out the usage of fossil fuels altogether. How this energy transition should be achieved, or even when the energy transition should be completed is subject of heated debates in political arenas, courts of law and the society as a whole. Whether or not future electricity demands can be met by sustainable sources is a particular important part of this debate. On the one hand, fossil fuels are (for the moment) cheap and readily available, by using fossil fuels it is always possible to generate the appropriate amount of electricity to match the demand. On the other hand, generating electricity from sunlight or wind can only be done when enough sunlight is available or the wind-speed is in an appropriate bandwidth. However, as electricity is also used during the night, and on cloudy, windless or stormy days, using sustainable energy sources as the primary supply for electricity generation can lead to a significant mismatch between supply and demand. This can imply that sometimes the electricity generated by solar parks during the day has to be curtailed because there is no demand for it, while during the night electricity still has to be generated using fossil fuels to meet the demand.A solution to this problem seems obvious: store the electricity. This allows to generate electricity using sustainable sources when available, and to store a sufficient amount to be able to meet the demand at all times. Although, this solution sounds simple, still many questions remain. Which type of storage should be used?, Where should the storage be located?, What should be the capacity of the storage?, How should the storage be used?, etc. In this thesis these types of questions are addressed for a specific type of storage: batteries. To answer these questions, and to support the important decisions necessary to complete the energy transition, three contributions are made:The first contribution is the development of the diffusion buffer model (DiBumodel) for battery state of charge (SoC) prediction. This model is specifically designed to be used in simulation tools for energy management in (smart) grids. Hence, this model should be a consolidation of broad applicability, accuracy and simplicity. The broad applicability of the DiBu-model is demonstrated by accurate predictions of the SoC of Lead-acid, Lithium-ion Polymer and Lithium Tot slot, en eigenlijk als voornaamste, bedank ik mijn familie. Pap en mam, jullie staan altijd voor me klaar, met woord en daad en vol belangstelling voor mijn werk. Ook als ik in het weekend naar Sassem kom, om tijd door te brengen bij Tjarda, of ...

Pricing mechanisms for energy communities : the Gridflex Heeten project

“…Due to the incompatibilities with the BMS, the sea salt batteries achieved only an effective capacity of 2 kWh (compared to the planned capacity of 5 kWh) and a maximum power of 300 W. These incompatibilities limited the energy efficiency of these batteries to around 18%. However, as the sea salt batteries have already shown an energy efficiency of 65.5% in other tests [64], we conclude that it is important to integrate and tailor all aspects in the technology chain properly to each other.…”

“…The initial project plan was to distribute 24 sea salt batteries [64], with a total capacity of 120 kWh, over the neighbourhood. However, the development of the sea salt batteries and their integration with a battery management system (BMS)…”

“…6.6 -Batteries proved to be challenging and by that, a research project on its own. A main reason for this was the unique behaviour of sea salt batteries that is not directly compatible with the existing BMSs designed for traditional battery technologies (see Section 5.6.4 of [64]). The additional effort and time required for solving these issues made it hard to combine the development of the battery with the given goals of the GridFlex Heeten project.…”