UK: UK Intellectual Property Office Sinks Embley Energy Patent

Last Updated: 29 August 2008
Article by Chris Moran

The UK Intellectual Property Office ("UKIPO", formerly The Patent Office) has recently issued an opinion regarding the validity of Embley Energy Limited's patent for a control system for a wave energy device. While the patent remains in force, the UKIPO has stated that it considers the majority of its patent claims to be invalid.


Bristol based Embley Energy Limited obtained a patent (GB 2,424,042) in 2007 around its SPERBOY" floating wave energy converter. The device relies on the oscillating water column principle and consists of a partially submerged buoy with a central enclosed column. Waves drive water oscillations within the column, displacing the air above. This movement of air in turn drives turbines at the top of the column. The Embley patent concerned the control of the turbines so as to improve the efficiency of the wave powered device. In particular, the speed of the turbine rotor is optimised based on the velocity of the airflow through it, with means for inputting energy into the rotor from an external source. This could be done based on either a prediction or a calculation of the airflow velocity.

In February of this year a request was made to the Intellectual Property Office for them to consider the validity of Embley's patent. The UKIPO has, for several years, run an "opinion" service where it considers requests from interested parties as to whether UK patents are valid and/or whether they would be infringed by certain acts. This opinion service offers a quick (opinions are typically given within three months) and relatively cheap way for companies to assess the strength or otherwise of patents. Typically requests are made by patent holders questioning whether a competitor's product infringes their patent, or alternatively by competitors themselves seeking an opinion as to whether their own products might potentially infringe and whether the patents in question might in fact be invalid. In this instance, the requesting party (who acted through a patent agent, thereby keeping its identity confidential) only sought an opinion regarding the validity of Embley's patent. Infringement was, therefore, not an issue.

It is important, however, to note that these opinions are not legally enforceable, i.e. they do not have the same authority as a court decision. Specifically, the patent remains fully in force despite the UKIPO's views.

The decision

The requester identified three documents published prior to the Embley patent, each of which it claimed described the same invention. For a patent to be valid it must describe an invention which is both new and inventive. Therefore, the UKIPO had to give its opinion as to, firstly, whether any of these three prior art documents did in fact describe each feature of Embley's "invention". Then, if not all the patent features were described in the prior art, the UKIPO had to consider whether the missing features would have been obvious to a person working in the field at the time, thereby depriving the Embley patent of the required inventiveness.

The first document described the OSPREY (Ocean Swell Powered Renewable Energy) project. This was an ill-fated device which was to be sited 100 metres off the shore at Dounreay. Unfortunately it was destroyed by heavy waves prior to the completion of its construction in 1998. The document described the collector vessel formed by a water column and four (uni-directional) Wells turbines and generators mounted above it. It also described a "Power Electronic Interface" and "Long Term Wave Predictor" to ensure that the mean turbine speed was optimum for energy recovery. Embley argued that this was not sufficient to destroy the novelty of their claim 1, which required an optimisation based on the velocity of airflow through the turbine. Unfortunately for Embley the UKIPO disagreed. The opinion noted that for a fixed geometry device (which was all that the Embley Patent envisaged) there would be a fixed relationship between the wave conditions and the velocity of airflow through the turbine. This lead to the finding that optimising the turbine speed based on a prediction of the wave conditions (as taught by OSPREY) was effectively the same as optimising it based on a prediction of the velocity of airflow through the turbine (as subsequently taught by Embley's Patent).

The final part of claim 1 of Embley's patent required a means for inputting energy into the rotor in order to adjust its speed. Embley considered this ability to speed up the rotor to be part of the efficiency optimisation during normal use of the device. Unfortunately for them the patent was not drafted in that limited way. It simply required there to be a means of inputting energy into the rotor. As the OSPREY device included a description of motoring the turbine to ensure it would start, the UKIPO found this feature to be present and, therefore, claim 1 of the patent to be invalid for lack of novelty.

For completeness the UKIPO then went on to consider the two other prior art documents. The first being a description of an oscillating water column pilot plant in the Azores, again with a Wells turbine. The second document was a description of the LIMPET (Land Installed Marine Power Energy Transformer), a the follow-up design to the OSPREY, and its vastly more successful installation on the Isle of Islay in 2000. However, neither publication was found to describe the claimed feature of a control system for adjusting the speed of the rotor based on the velocity of airflow to optimise its efficiency.

Having decided that the main patent claim was invalid, the UKIPO went on to consider the host of other claims. In what at first sight appears to be a slightly odd decision, the UKIPO found that while the OSPREY document described the optimisation of rotor speed based on a "prediction" of airflow velocity, it did not teach, nor was it obvious, to base the same optimisation on a "calculation" of the airflow. Hence, the Embley patent claim to optimisation of rotor speed based on a means of "calculating" the airflow was considered to be valid. The distinction between "prediction" and "calculation" in the Embley Patent and the UKIPO decision is unclear, particularly when the computer performing the "prediction" seems likely to be performing calculations as part that task. It is therefore possible that the UKIPO took "calculate" in this context to involve the physical measurement of the airflow, perhaps using an accelerometer as alluded to in the specification of the Embley Patent. Other claims to the use of an impulse turbine and to a water-driven turbine were also not described or rendered obvious by the air-driven Wells turbines (reaction turbines) described in the prior art. Hence, these claims were also considered to be valid.


UKIPO opinions are a quick and low cost approach to assessing the strength (or otherwise) of a patent. Despite their non-enforceable nature they have proved to date to be a popular part of companies' patent strategies, particularly for companies wishing to avoid the cost of full blown patent litigation.

The company requesting this Patent Office opinion will no doubt be satisfied that, in the UKIPO's view, the majority of the claims of the Embley patent are invalid. The opinion gives a clear indication that Embley would be in treacherous waters should it seek to enforce the patent before the courts. Whether the requesting party has, or is planning on launching, a similar system or perhaps is just seeking funds to do so, this opinion will likely give it confidence to press ahead with its plans.

Given the rapidly increasing amount of R&D in the renewable energy sector and the increasing number of participants and patents within it, we can expect further requests to the UKIPO as parties seek insight as to the strength and scope of patents in this area.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

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