Development of the membrane for the wave power plant

Presentation of the project

Cooperation on the wave power plant project came to us, Trelleborg Bohemia, Velké Poříčí with the transfer of Dunlop, from Great Britain. The project is for a customer of Bombora Wave Power, which is also based in the UK.

The principle of the wave power plant is described in the figure below. To create an idea of how great a work is, it should be noted that the size of one cell in the picture below is 16.5 m. Thus, what, you see in the picture below is a size of about 70 m in length, without a turbine.

Figure 1 – Principle of wave power plant


What Trelleborg supplies is the membrane – the interface between sea and air. It is a rubber-textile product, combining the requirements for maximum elongation in the working area with the requirements for maximum rigidity in the area of anchoring.


The mixture was developed in Trelleborg Industri AB, Sweden. The selection of the mixture was a key step, in which both the customer and colleagues from Trelleborg Industri AB participated.

Method of manufacture

The membrane will have final dimensions of approx. 16.5 x 5.5 x 0,1 m. In particular, the thickness – up to 100 mm – was from the beginning taken as a great challenge. The production is also complicated by the reinforcement of the membrane with textiles.

The production is complex already by the fabrication, the product must be homogeneous, without trapped air and constant thickness. The semi-finished product is unvulcanized “endless” strips of width of 1.5 m. The total length of the joints is almost 2,000 m.

After the hand confection the product needs to be vulcanized. From the beginning, two vulcanization technologies were considered, vulcanization in the boiler on the cylinder, or on a special and unique Rubby press, which is used for the production of rubber-textile bladders.

A series of tests were carried out to verify the possibility of production in both ways. Both vulcanization methods have advantages and disadvantages. After a long and complex discussion, it was decided to continue with the Rubby machine but with adjusted pressing pressure.

Test membranes

The customer, Bombora Wave Power, approached us in the meantime with a demand for the production of test membranes, for their testing equipment. In total we supplied 3 pcs of these membranes, with dimensions of approx. 5.5 x 2.5 m and a thickness up to approx. 12 mm.

Figure 2 – Test membrane at the facility, Pembrokeshire

These test membranes have greatly helped both the customer in the validation of his calculation models and us in the verification of production processes.

State of play

According to the original plans, at the turn of April and May 2020, 4 pcs of full-size membranes were to start. Unfortunately, the Covid-19 situation has also been delayed. For an idea of the size of the equipment, attached an image from the production of the frame of the wave power plant at the customer.

Figure 3 – Steel Frame Production

Filip Honsa, Head of R&D Bags