Lake Sihwa in South Korea is home to the world’s largest operating tidal power station, using the tides to generate enough power for a city of half a million people. This regular rise and fall of the seas is more predictable than sunny or windy weather and can be forecast years in advance. Nine thousand miles away in Northern Ireland is Strangford Lough. A narrow inlet leading to the mighty Atlantic Ocean means it’s one of the world’s best sites for harnessing tidal energy. The fast and strong currents have led to the world’s first commercial-scale tidal energy power station being built here. But now that’s being decommissioned.

The technology for harnessing tidal energy has been around for more than half a century and the potential to create energy from the sea is huge. Yet tidal power only accounts for a tiny proportion of the global renewable energy mix. Presenter Graihagh Jackson finds out what’s holding tidal power back. Thanks to our contributors: Rémi Gruet, CEO of Ocean Energy Europe Dr Carwyn Frost, Lecturer at Queen’s University Belfast Choi Jae-baek, Senior Manager of K-water Email: theclimatequestion@bbc.com Presenter: Graihagh Jackson Reporters: BBC’s Jordan Dunbar in Norther Ireland and freelance journalist Malene Jensen in South Korea Producer: Ben Cooper Researcher: Octavia Woodward and Shorouk Elkobrosi Editor: Alex Lewis Sound Engineer: Tom Brignell