Heat Pumps in Low Voltage Distribution Grids by Energy Storage

With the transition of energy systems from fossil fuel based centralized power generation towards renewable based decentralized power generation limitations can occur within the existing grid infrastructures. In this paper significant increases in both the application of photovoltaic systems for power generation and the application of electrically driven heat pumps for heat generation are taken into consideration. Different solutions to overcome the grid congestions are investigated. Out of plenty of possible energy storage solutions this paper concentrates to the application of thermal energy storage (hot water) together with heat pumps due to the significant price advantage of thermal energy storage against electricity storage. Further investigated solutions are the integration of e-mobility and the application of demand side management. Within this research project grid infrastructure of the German city of Cologne has been investigated towards its suitability to cope with the energy transition process and it was found that there exists almost no limitation in most areas. In this paper the results of the investigation of a district dominated by multi-family houses with a heating surface area of 13,800 m(2) and a school building are presented. The results show that some restrictions occur without implementing the further smart-grid measures. Concerning the integration of electrically driven heat pumps into the existing grid infrastructure without thermal energy storage only 45 % of the district could be supplied. However, the heated district area doubles (90.6 %) with the integration of thermal energy storage. Photovoltaic system installations can be increased by 78 %, representing an increase from 195 kW(p) to 347 kW(p) by the application of demand side management. Further, the paper presents the results from integrating electric cars and its charging infrastructure into the selected grid. Comparison for random and controlled charging is provided taking low load conditions and high solar irradiation into account. Additionally, stationary battery storage is investigated.