Stiesdal has been involved in the wind industry since its inception. He built his first small wind turbine in 1976 going on to work as a consultant to Vestas until 1986, when he joined Bonus Wind Energy. He has been CTO of Siemens since it acquired Bonus in 2004.
Kjaersgaard is taking up a position as CEO of an unnamed Danish company. This year he was promoted to CEO of the onshore wind division following a restructure by Siemens.
Stiesdal's achievements at Siemens include working on the first marinisation of turbines for offshore, developing direct-drive technology, and the development of Siemens' IntegralBlade manufacturing technology, where blades are cast in one piece.
Speaking to Windpower Monthly in 2012, Stiesdal said it is the latter of which he is most proud: "Before we did this, the only way to cast the blade as a single piece was to use an inner mould, but that was then too big to get out of the blade."
The exit of Stiesdal marks a watershed, with the departure of one of the last CTOs around since the early days of the industry. Last year, Repower (now Senvion) CTO Matthias Schubert left the company after being with it since its founding.
Kjaersgaard joined Bonus in 2001 before it was taken over by Siemens. He rose through the ranks to take up the position of CEO of the onshore wind division last year.
Morten Rasmussen, who currently heads the R&D department in Brande, will take over as head of the technology unit onf 1 August.
Stiesdal will assist Rasmussen in the first months, supporting him in assuming the new responsibilities, and will also be available for consultations after leaving the company.
Siemens said it will also separate the CTO function from the technology unit, and will "fill the position at the appropriate time".
Jan Kjaersgaard will continue to manage the business activities of the onshore division through to 30 September.