Concrete — though it seems conterintuitive — floats. And floats well. This summer, in the waters off western France, this rock-hard material — used for megaprojects from the ancient Roman dome of the Pantheon to the Hoover Dam — will be tested for its next industrial incarnation: floating wind power.

The flagship of a concrete platform-based concept being built by floating wind pioneer Ideol under the aegis of the EU’s €25m ($26.5m)