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Wobben Properties GmbH v. Siemens plc & Ors, UK, Court of Appeal (Civil Division), Kitchin LJ, Longmore LJ, Floyd LJ, 19 January 2017, Neutral Citation Number: [2017] EWCA Civ 5

This is an appeal against the judgment of Birss J of 20 July 2015, in which he held that Wobben’s patent was invalid for lack of inventive step over one piece of prior art, and that even if valid, would not have been infringed by Siemens’ variable speed variable pitch (VSVP) wind turbines (see here). The patent concerned a method of controlling pitch controlled turbines in high wind speeds. Kitchin LJ, giving the leading judgment, dismissed the appeal on all counts.

On inventive step, Kitchin LJ disagreed with Wobben’s argument that the skilled person would not have had the motivation to apply the prior art, an article called Bossanyi. Bossanyi is a publication of a theoretical study investigating the frequency of sudden decreases or increases in the power output of clusters of wind turbines, and control strategies that might mitigate their impact on the electricity grid. Kitchin LJ concluded that, especially since there had been a rapid growth in wind energy through the 1980s and 1990s which was only going to continue, the skilled person reading the prior art would see the goal in Bossanyi of improving network stability as one which was well worth pursuing. In addition, Kitchen LJ agreed with Birss J’s findings that while the whole teaching of Bossanyi concerned fixed speed turbines (which were the prevalent turbines at the publication date of Bossanyi), by the priority date, the industry had moved on and was now focused on VSVP machines. Further, the most relevant aspect of Bossanyi was not concerned with the nature of the turbine, but the operation of the turbine at high wind speeds. Therefore, it was obvious to apply the prior art to a VSVP turbine.

In coming to this conclusion, Kitchin LJ held that there was a degree of common ground between Siemens’ expert and Wobben’s expert and the judge was entitled to step back and consider the wider picture. Kitchen LJ further noted that Birss J’s conclusions had a proper basis in the relevant common general knowledge (CGK).

The Court of Appeal also agreed that Siemens’ VSVP turbines did not infringe. Siemens VSVP system calculates the acceleration or deceleration of the rotor and this data is then subjected to a filtering process. Rotor speed is then reduced depending on how fast the wind is changing (i.e. the filtered rotor acceleration). In contrast, the patent claimed a system which reduced rotor speed in response to wind speed increasing. Kitchen LJ held that measuring the filtered rotor acceleration did not equate to measuring increases in wind speed; the rotor accelerates or decelerates depending on the turbulence rather than the wind speed.

A copy of the judgment can be found here.

Headnote by Rachael Cartwright, Bristows LLP