Renewably stored electricity for the island
Wind energy and photovoltaic systems do not always generate power when it is needed. Schleswig-Holstein is therefore testing the local storage of renewably generated electricity on the North Sea island of Pellworm. The SmartRegion Pellworm project has now won first place in the German Renewables Award competition.
On average, three times as much electricity is produced on Pellworm than is consumed by the 1,200 residents living on the North Sea island. Since 2012, a consortium from industry and science has therefore been working for the SmartRegion Pellworm project. Among others, the aim was to mitigate the intermittent supply of renewable energy and to significantly improve its local utilisation. A special storage system was built on the island for this purpose and the customers’ electricity connections were coupled through data links with the wind and photovoltaic systems. The existing power infrastructure on the island was also supplemented with different components. At the start of the project, Pellworm received the first smart grid in northern Germany.
First place for the “Project of the Year”
SmartRegion Pellworm won the German Renewables Award 2015 in the category “Project of the Year”. The prize is awarded by the Renewable Energy Hamburg Cluster. “Over decades, Hansewerk AG and Schleswig-Holstein Netz GmbH have created a supply system on the North Sea island that is distinguished by the high use of renewable energies,” said the judging panel in its appraisal. After having already received Schleswig-Holstein’s Business Environmental Award in 2014 and the Public’s Prize in the national “Land of Energy” competition in 2014, this is the third time that the SmartRegion Pellworm project has won first prize.
Large-scale storage system can be used for both long- and short-term storage
A redox flow battery is used as a large-scale storage system. With a storage capacity of 1,600 kilowatt hours and a maximum power of 200 kilowatts, the battery can be fully charged or discharged within eight hours. This enables it to be also used as a long-term storage system. The island’s storage system is supplemented with a powerful lithium-ion battery. It has a storage capacity of 560 kilowatts per hour and can be completely discharged in about half an hour and charged within an hour. It therefore serves as a short-term storage system. Lithium-ion domestic storage systems are also situated in eleven homes. These short-term storage systems are available in two output classes: 4.5 or 10 kilowatts.
Storage systems, power electronics and energy management system
If the storage systems are full, the surplus energy is fed via two submarine cables into the electricity grid on the mainland. In addition, the exchange of data between the electricity connections and the generation plants on the island is being tested and further developed. “High-performance batteries, domestic storage systems, electric storage heaters and electric cars enable the local storage of renewable electricity. The lights will therefore still be on even when the wind turbines are not rotating during calm spells,” says Dieter Haack, head of the SmartRegion Pellworm project.
The two local network transformers automatically regulate the voltage in the grid so that it is kept constant at 400 volts and the grid remains stable. The power electronics provide the interface between the lithium-ion battery and the grid, and have a capacity of one megavolt amperes. The power electronics convert the alternating current from the grid into DC power for the battery and vice versa.
An energy management system controls the SmartRegion Pellworm and the storage systems. The system provides energy forecasts based on many influencing factors specific to the island of Pellworm. These include, for example, weather data. A hybrid power plant consisting of a solar array and a wind turbine produces just over one megawatt of renewable energy at peak times. The electricity generated is enough to supply around 650 households on the island.
What is currently being realised on Pellworm on a small scale could help to reduce the old dependencies of the energy world and, by coupling energy production and consumption, improve the use of the existing energy system and thus make it more powerful.