The case of Wobben Properties v Siemens & Ors [2015] EWHC 2114 (Pat), saw the Patents Court considering a technical dispute concerning the alleged infringement of Patent EP (UK) 0 847 496 regarding the operation of wind turbines in high wind conditions, but also highlighted the broader commercial impacts on customers where patent disputes are not confined to patentees and equipment manufacturers and suppliers.

On 20 July 2015, the Patents Court of the Chancery Division of the High Court has handed down its judgment on the dispute between Wobben Properties GmbH (‘Wobben’) and (1) Siemens Plc, (2) Siemens Wind Power A/S, (3) Siemens AG, (4) DONG Energy A/S, (5) Westermost Rough Ltd, (6) DONG Energy Gunfleet Sands Demo (UK) Ltd, (7) A2Sea A/S, and (8) A2Sea Ltd (the ‘Defendants’).


The dispute concerns Patent EP (UK) 0 847 496 entitled "Method of Operating a Wind Power Station" which Wobben, the proprietor of the patent, alleged was infringed by the supply and use of the High Wind Ride Through ('HWRT') technology by the Defendants.

At the centre of the dispute was the Siemens HWRT technology that allows a wind turbine to operate at some storm-level wind speeds. When the wind speed is higher than 25 metres per second, wind turbines typically shut down in order to avoid overload due to extreme loads. Equipped with HWRT technology, the wind turbine will gradually reduce power output instead of shutting down immediately, deriving benefits for both the electricity generator and the grid.

Wobben alleged that the first three defendants (‘Siemens’) had infringed the patent by manufacturing, marketing and supplying wind turbines incorporating technology which was the subject of the patent.
The Dong Energy defendants were alleged to have infringed the patent in the course of their development of various wind farms which use the wind turbines manufactured by Siemens, and the A2Sea defendants were said to have infringed the patent in the course of their installation of wind turbines for Siemens and Dong Energy.

Wobben had separately brought a further set of proceedings against London Array Limited whose wind farm in the Thames Estuary uses a large number of Siemens wind turbines in which the allegedly infringing technology had been installed.

In an earlier hearing, Wobben had also taken the rather unusual step of obtaining a Norwich Pharmacal order requiring Siemens to provide details of the identity of its customers within the jurisdiction of the court where the technology had been activated, or was to be activated between the present time and the trial.

Wobben was seeking the usual relief, a declaration of infringement and validity, delivery up of infringing materials, public dissemination of the judgment and damages/account of profits in relation to the infringing activity.


The Court first considered the validity of the patent, considering the detailed expert evidence provided by both Wobben and Siemens, particularly by reference to two items of prior art relied upon by Siemens, namely a Japanese application filed in 1980 and published in 1981 (“Shozaburo”) and an article written and published in 1982 (“Bossanyi”).  Shozaburo was relied on in relation to novelty and lack of inventive step, and Bossanyi only in relation to lack of inventive step.  There was also debate as to the identity of the person skilled in the art; Wobben contending this should be a wind turbine control engineer and Siemens a more general wind turbine engineer. The Court accepted the Siemens’ formulation in this respect. 

Having reviewed the detailed technical evidence on wind turbines and their mode of operation in 1995, together with the wording of the patent, the Court concluded in Wobben’s favour on the question of the novelty of the Wobben patent over Shozaburo, but then, by reference to Bossanyi, concluded that there was no inventive activity involved for a skilled person.  Moreover, the Court concluded that the steps taken by Siemens with their HWRT technology was an obvious approach.

The Court therefore held that the patent was invalid.

The allegation of infringement also involved a large number of complex points on which the Court relied heavily on the expert evidence of the parties. A major part of Wobben's argument concerned the nature of the wind itself as experienced by a turbine rotor as a whole rather than an argument about how HWRT works.

The patent proposed that the invention causes the wind turbine to be compulsorily reduced in its operating speed above the normal shut down point depending on a rise in wind speed, whereas HWRT was held to operate by measuring filtered rotor acceleration (rather than wind speed) and it reduced rotor speed in dependence on a rise in absolute filtered rotor acceleration in order to protect the turbine from dynamic loads associated with accelerations and decelerations.

However, ultimately, the Court did not accept that the evidence supported Wobben's submission on the facts. The Court therefore also rejected Wobben's case on infringement and held that, even if the patent had been valid, it would not be infringed.


This was a highly technical case and, as such, was decided very much upon a detailed analysis of the expert evidence and the relevant technology as at the relevant date.  Whilst the outcome of the case was ultimately successful for Siemens and the other defendants, the approach of Wobben in bringing claims directly against Siemens’ customers, as well as against Siemens, and forcing disclosure of the identity of others who had purchased technology from Siemens, shows the direct broader commercial consequences where patent disputes are not confined to patentees and equipment manufacturers and suppliers.  As demonstrated by this case, proceedings can also involve those responsible for transporting and installing the infringing technology, as well as the end customers and users of the technology, who may feel that they have been caught up in someone else’s dispute.