Wavepiston is a concept to harness wave power using a long string with collector plates that move with the waves. Hydraulic pumps between the plates pump water onshore, where it can either drive a turbine to create electricity or be used in desalination.

The concept has been developed since 2009, with Wavepiston A/S incorporated in 2014, based in Helsingør, Denmark.

The first full-scale device was installed off the coast of Gran Canaria in early 2024.

The device is a floating string with a series of plates, or energy collectors, spaced along it. These move back and forward with the passing waves and the relative motion is used to drive hydraulic pumps that suck in and pressurise seawater. This pressurised water is then sent onshore where it can drive a turbine to create electricity and/or be used in a reverse osmosis desalination plant.

By incorporating multiple collectors on a single string, the wave forces on each collector help to "cancel out" the forces transmitted to the moorings. This means the device only needs two small moorings. The string is formed from a steel wire rope, and has a slack mooring at each end.

As the device sits just below the sea surface, it has a low visual profile, and thus could be a good fit for tourist destinations.

Wavepiston claim that as their device uses lightweight modular components, the costs are significantly reduced.

The concept has been developed since 2009, when the first patent was awarded. Since then it has been tested at increasing scales. In 2010, tank testing was performed at 1:30 scale in the wave basin at Aalborg University. This was followed by sea trials in Nissum Bredning at 1:9 scale and at Hanstholm at 1:2 scale. There were also plans to test a device at Isola Piana, on the south-west coast of Sardinia as part of the Wave to Energy and Water (W2EW) project.