Orkney’s fast-flowing tidal inlets and coastlines are forever battered by ocean swells, and for two decades, targeted by wave and tidal stream energy firms developing new electricity sources.
One Scottish ocean energy company, Orbital Marine Power, has been testing tidal stream technologies that are ready to go large-scale, including a giant turbine capable of powering over 1,700 homes. With the first “O2” turbine due to be deployed this year at Orkney’s European Marine Energy Centre (EMEC), and another to follow in 2023, it is one of several commercial marine energy farms that could contribute up to a fifth of the UK’s power needs. For technical reasons, wave energy itself has proven difficult to harness. Of the countless wave generator prototypes designed and tested in the last 20 years, very few have reached commercial scale — despite much promise. The key problem is variability. AbuBakr Bahaj, professor of sustainable energy at the UK University of Southampton and editor-in-chief of the International Marine Energy Journal, says that because waves are in constant flux and move in multiple directions and heights, devices must also be flexible and durable enough to both harness energy and handle heavy and constant motion. “It’s very difficult to capture a lot of energy,” he said. Tidal stream energy on the other hand is significantly more reliable. Based on the pull of the moon and earth’s rotation, tidal flows are “very predictable,” said Bahaj. “You can do a plan for the next 15 years of energy coming from tidal without missing a minute.” Tidal energy can be a reliable backup within a renewable power grid that is vulnerable to wind and solar power variability — a role that is often being filled by climate change-inducing fossil energy, natural gas.
Despite a stuttering beginning, global wave and tidal stream energy production rose tenfold between 2009 and 2019, according to a 2020 report. Marine energy industry group Ocean Energy Europe is attempting to harness this growth with its 2030 Ocean Energy Vision. By bringing the marine energy price down to a competitive 90 euro ($108) per megawatt-hour (MWh) in the next decade — the same price as wind — the ultimate goal is to increase output to 100 gigawatt hours (GWh), which it says would cover 10% of Europe’s current electricity needs. While the ambitious target draws on the vast potential of Europe’s sea basins, the UK, which has around 50% of Europe’s tidal energy and 35% of its wave energy, will be key to achieving the target.
Indeed, the UK government says 20% of power for electricity could be drawn from the ocean, raising output to above 30 GWh of domestic capacity. But these targets remain a long way off, with just 1.5 MW of tidal stream capacity added in Europe in 2019, and just above 0.5 MW for wave energy. By contrast, around 3.6 GW of offshore wind capacity was installed across Europe that year. So, while wave and tidal energy is growing in potential, the reality of it being able to cover 10% of all of Europe’s energy needs seems a distant way off.
Ocean energy about to ride a wave, Deutsche Welle, 2021-02-09