Fraunhofer IEE – Designing an efficient electrical power take-off for WEDUSEA


Fraunhofer IEE

By Fabian Thalemann, M.Sc.
Fraunhofer Institute for Energy Economics and Energy System Technology IEE

The Fraunhofer Institute for Energy Economics and Energy System Technology IEE in Kassel, Germany, stands for energy transition research. Under the motto ‘Designing the Energy Transition’ Fraunhofer IEE scientists have been conducting research for an energy supply based on renewable energies for over 30 years – both nationally and internationally.

The institute’s staff comprises approximately 450 scientists, students, and other employees, who generate an income of about 38 million euros per year. Fraunhofer IEE develops solutions for technical and economic challenges in order to further reduce costs, secure supply, advance digitalization in the energy industry and develop new business models in the energy transition. In particular, the business units are Energy Meteorology and Geographical Information Systems, Energy Networks, Digital Energy Economics as well as System Technology and System Dynamics.

Fraunhofer IEE’s Role in WEDUSEA
In WEDUSEA, Fraunhofer IEE’s first main task is the modelling, selection, procurement, and dry testing of the electrical power take-off (PTO) system, comprising all major electrical components between the platform’s air turbine and the power cable connecting the platform to the onshore electrical substation. Special emphasis is put on the selection of the generator, which is required to operate highly dynamic in a wide range of mechanical operating points, and in a technically challenging marine environment.

Another important electrical component is the SuperCapacitor, an electrical storage unit required to smoothen the ever-fluctuating power output from the generator. The smoothened output is then converted to a specific electrical frequency and transformed to a certain voltage level, so that a suitable power quality is achieved to feed the power into an onshore electrical grid.

The second task is to design, program and implement the operation control required to run the PTO as desired and required, enabling the operation of the single components as one effective combined system in various operating modes, static states, and dynamic transitions between those states. The effectiveness and capability of the operation control is closely linked to the automation hardware and sensor equipment which is designed and selected by University College Cork with support from Fraunhofer IEE.

After the successful launch of platform operation, Fraunhofer IEE will furthermore lead an activity to optimize generator and turbine control, the platform’s power output and the related power quality, and the overall efficiency of PTO operation.

Scaling up on the path to industrialisation
Fraunhofer IEE has previously been involved in a predecessor project of WEDUSEA – Components for Ocean Renewable Energy Systems (CORES.) In the CORES project, which ran from 2008 to 2011 and was funded by the European Union, Fraunhofer IEE developed and tested the PTO of a much smaller version of the OE Buoy, including the control and the grid integration. The scale-up to 1 MW rated power of the recent version is the right direction towards industrialization of this renewable energy technology. Especially in an offshore environment, “big is beautiful” from a specific investment and operation cost perspective. This gets very clear when looking at rated power per device values of offshore wind turbines, which can reach 10 MW, even up to 16 MW today. With industry focused on portfolios of offshore capable power electronics in that particular range, finding suitable off-the-shelf products in the range of 1 MW is surely challenging. Fraunhofer IEE has to make sure that all components are fit for duty in cold, moist and salty environments, withstand heavy platform motion, and can be efficiently operated at part load as well as full load and even brief overload situations.

Designing the energy transition, transforming the industry
Addressing climate change is a social obligation and one of the greatest economic opportunities. For Germany, the biggest challenge currently ahead is the transformation of the energy industry, which is heavily reliant on natural gas, towards electrification. Secondly and with that particular prerequisite, another challenge is to keep the electrical grid stable and reliable, particularly with the upcoming fade out of coal power plants and the introduction of more fluctuating renewable energy generated by wind turbines and photovoltaic plants. For northern and western Europe, marine energy could play a part in replacing fossil fuel-based power production, if industrialization is successful.

This explains why WEDUSEA is such a vital project and why Frauenhofer IEE are pleased to be a partner, helping to deliver its success.

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Disclaimer: Funded by the European Union. Views and opinions expressed are, however, those of the authors only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them.