Wobben Properties GmbH v Siemens Public Ltd Company & Ors [2017] EWCA Civ 5
Wobben is the proprietor of a patent (EP’496) relating to a method of operating pitch-controlled, variable rotor speed wind turbines in high wind speed conditions. At first instance, Birss J held that EP’496 was invalid for obviousness in light of an article by Dr Ervin Bossanyi published in 1982 entitled “Probabilities of sudden drop in power from a wind turbine cluster”. The Judge also held that Siemens’ High Wind Ride-Through system would not have infringed EP’496, had it been valid.
Wobben appealed against the findings of Birss J, contending that the judge had wrongly directed himself as to the legal test for obviousness and had made a series of fundamental errors in assessing the evidence. Wobben also appealed the Judge’s construction of claim 1 of EP’496, which required that the reduction in the rotor speed of the turbines be caused by the increasing average wind speed across the swept area.
Longmore, Kitchin and Floyd LLJ dismissed Wobben’s appeal. They held that (i) Birss J could not be criticised for the way he had approached the question of obviousness and (ii) although the correct construction of causation did not require a causal relationship, the “high wind ride-through” function of Siemens’ turbines was not using filtered rotor acceleration as a surrogate for wind speed and so could not fairly be said to infringe EP’496.
Michael Silverleaf QC and Adam Gamsa appeared for Wobben.