Gemini Wind Park: The Board



Bart Hoefakker


Bart Hoefakker is the Vice President Operations Offshore of Northland Power Europe. He joined Northland Power in January 2023 after a career of more than eight years as respectively Operations Manager (2014-2018) and CEO (2018-2023) at Gemini Windpark.


Bart has an extensive career in offshore wind, previously as the Managing Director of the Egmond aan Zee offshore wind farm (Shell/Vattenfall JV) and  with Vattenfall as Operations Manager for their international wind portfolio and various roles within NedWind, a Dutch wind turbine manufacturer.


Bart holds a diploma in Electrical Engineering from HAN (university of applied sciences) in Arnhem.





Stephan Berendes


As Vice President & divisional CFO Offshore Wind, Stephan Berendes is responsible for the financial affairs of the global offshore wind activities of Northland Power. Currently this is mainly focussed on Europe and Asia.


From 2018 to 2022, Stephan worked at Gemini Windpark as Senior Finance Manager and CFO. Prior to that, he held several senior finance management roles and lectured auditing in the post-master’s accountancy program at the University of Amsterdam.


Stephan holds a Business Economics degree from the Amsterdam University of Applied Sciences, a Post-Masters degree in Audit from the University of Amsterdam and is a Chartered Accountant.






Stephan Schaller


Stephan Schaller has joined the Board of Gemini in October 2015. He studied economics at the University of Erlangen-Nuremberg, Germany, with a special focus on management, international management and marketing and earned his academic degree in 1996.


Before joining Siemens Financial Services where he is currently working as a Project Director for Equity Investments across different Siemens Businesses he worked as Head of Business Development in the Renewable Energy Division of Siemens. Since 2004 one of his main priorities was on the development of the Renewable Business within Siemens with a main focus on Wind Power. He joined Siemens after university in the commercial sales department of the communication group in Munich. After that he had hold different management roles in the strategic department of the Power Generation business.



Istir Krista


Istir joined the Supervisory Board of Gemini in April 2021 as part of her role as Project Director with Siemens Financial Services. Istir is responsible for the management of Siemens’ equity investments in the EMEA region.


She has more than 20 years of experience in Corporate Finance Advisory and Investment Banking. Prior to joining Siemens Financial Services, she worked in different roles and for different companies. Most recently she advised start-up companies and venture capital investors.


Previously Istir worked with KMPG Vienna and PricewaterhouseCoopers in Frankfurt in Corporate Finance Advisory with focus on Corporate Valuation. After concluding her diploma in international business studies, Istir started her professional career as equity analyst covering German listed companies.


Arjan ten Elshof


Arjan has a degree in Mechanical Engineering and began his career in the IT sector in the late 1980s. Companies such as Philips, Digital and internet startup FICS were the most important employers in the early days of his work experience.


In 2001, Arjan made a switch to the energy industry and took a position as Chief Information Officer at Eneco. Eneco is among the larger energy suppliers in the Netherlands.


After this initial position, he moved to non-IT roles within Eneco: from IT to final responsibility for all Eneco Customer Service Centres, and from there to final responsibility for all commercial downstream activities. By 2010, Arjan was responsible for overseeing all of Eneco’s downstream activities in the Netherlands and Belgium. He left Eneco in October 2014.

From 2015 to 2017, Arjan held a variety of positions with different companies as interim manager and consultant, while also establishing a small consultancy firm. One of the companies he worked for during that period was HVC, first on an interim/consultancy basis and later as a Board member.


In 2017, Arjan took a position with HVC as a member of its Executive Board (Management Team). Within that team, he bears responsibility for all Sustainable Energy activities. This includes both on and offshore wind, large and medium-sized solar projects and a significant District heating business.




Georg Obert


Georg Obert studied business administration at the University of Mannheim, Germany, followed by different studies in Australia (corporate law and taxation, project management and financial Modelling with Excel). He worked, amongst others, for Ernst & Young, Babcock & Brown and Esko Energy Partners GmbH.


Georg Obert is active in the renewable industry since 2004. He successfully closed numerous wind- and solar transactions over the course of his professional life. His transactions have a strong focus on Germany and France, but he was also active outside of Europe, where he financed wind parks and negotiated PPAs. His track record encompasses a transaction volume of well over EUR 1 bn. He also advised several parties on selling their projects during his time at Esko, but soon decided together with the management team to join the ranks of wpd in order to create the first institutional fund with an industry background. He is currently responsible for the transaction side of wpd invest’s business, which currently focuses on a Luxembourg vehicle (Green Return Fund – Core SICAV FIS) and a managed account from a large German insurer.