Engineering projects show growing promise for tidal energy

Tidal energy has been slow to develop into a reliable form of grid power, but recent demonstration projects suggest that might be changing. If the technology continues to mature, tidal energy could become a significant renewable power source in many countries.

The problem: Although energy developers have long sought ways to exploit ocean tides to generate electricity, few large-scale projects are actually running in the water. That's because operating in the ocean poses a frustratingly difficult engineering problem: Corrosion, biofouling and extreme wave and current forces all contribute to the slow destruction of devices.

Tidal power's benefits:

• Tidal energy is dense: Seawater is 830 times denser than air. This means, at least in theory, that a tidal energy converter has a smaller physical footprint than a solar or wind array producing the same amount of power.
• Tides are predictable and easy to forecast — not just hours in advance, but decades. The intermittency is predictable, which from a grid perspective makes tidal energy much easier to integrate.

What's new: Proving reliability through large-scale demonstration projects is a key step toward making tidal power a reality.

• Last month, Atlantis Resources, a U.K.–based tidal energy developer, announced that its MeyGen project has cumulatively delivered about 6 GWh to the grid since it was connected a year ago. It produced 1,400 MWh in March alone, equivalent to the monthly energy consumption of about 1,500 U.S. homes.
• Scotrenewables, another U.K. tidal developer, reports that as of last April its device generated a cumulative 2 GWh since August 2017.

The bottom line: Tidal energy still has a ways to go before it becomes cost-competitive with other renewable energy technologies, but these numbers point to a maturing sector that is reliably generating real power for the grid.

David Hume is a marine engineer contractor supporting the U.S. Department of Energy Water Power Technologies Office's marine renewable energy portfolio and founder of The Liquid Grid. The views expressed are his own.