Holliday stood down from leading the UK's grid operator National Grid in July 2016, after nearly ten years on the role.
Prior to that, he was on the board of British Borneo Oil and Gas, and a part of Exxon.
Holliday has also been deputy chairman and senior independent non-executive director at FTSE 100 listed ConvaTec since its 2016 IPO and is also the lead non-executive director at the UK government's Department for Environment, Food and Rural Affairs.
Kowski is stepping down as chairman, a role he held since the acquisition by US investment firm Centrebridge Partners in April 2015.
"I would like to express my personal thanks and appreciation for Stefan Kowski's passionate work and commitment in support of our strategy. He has contributed substantially to executing our IPO and helping us bring the company to the next strategic level," said Senvion CEO Jurgen Geissinger.