UK policy documents from the early 1980s foresaw tidal power as a renewable technology with a rising future. Official estimates suggested that one tidal barrage scheme alone, in the Severn Estuary, might generate enough electricity to meet around 5% of the country’s needs, at a cost close to that of a new coal-fired power plant. Power without the pollution!

Official estimates suggested that one tidal barrage scheme alone might generate enough electricity to meet 5% of the UK’s needs.

Alas, in subsequent decades, support for various tidal technologies was swept away. The Severn barrage did not proceed, despite the estuary enjoying one of the highest tidal ranges in the world. A large tidal lagoon proposal at Swansea has also remained on the drawing board for years. At Strangford Lough in Northern Ireland, a much smaller tidal stream project generated electricity in the early millennium, but has now been decommissioned.

Various factors explain the ebbing enthusiasm. Building on the experience gained from onshore wind and from the UK’s North Sea oil and gas industry, the falling costs of offshore wind have surprised positively, turbo-powering it into the premier league of renewable technologies in recent decades.

Meanwhile, significant coal-to-gas switching became popular to lower the carbon intensity of power emissions across the EU and UK. Moreover, the Anglo-French entente cordiale secured funding for a new nuclear power plant at Hinkley Point. This was underpinned by support from China, viewed as an important financial ally at the time.

And yet, tides do what tides do, they turn at the lowest ebb. The geopolitical context for energy has now changed radically. Under its Contracts for Difference (CfD) scheme, the UK government has recently supported four smaller tidal stream projects, of which the largest (28MW) is at the MeyGen site in Caithness, Scotland. However, these projects, totalling under 50MW of capacity, are minuscule relative to the UK’s official ambition to install 50,000MW of offshore wind by 2030.

Do tidal power’s current ripples augur a future high tide for the technology? This will depend significantly on energy policy. Any longer-term perspective that considers the UK’s current energy needs and those of our descendants should see that the case for a surge in tidal power is rising again.  

Tidal power is genuinely renewable and completely predictable. The tides will last for millions of years. The technologies are well-understood and, with scale, cost curves are likely to follow those of wind and solar. With proper maintenance capex, the life of tidal projects is effectively infinite. If strategically located, tidal sites could play a significant role in providing reliable energy across the country, a ‘levelling up’ exercise where all UK citizens benefit from the hidden bounty on our coastlines.

Indeed, there is a subtler argument for including tidal power within our future energy mix. We have learnt only too well recently that any robust energy has the concept of diversification at its core.

Although sometimes overlooked, this principle will apply equally in the wholly renewable systems of the future.

Tidal flows are caused principally by the gravitational dance of the moon and the Earth. Even if the sun’s light were dimmed or wind patterns changed, the tides will still rise and fall.

Tidal power is well-diversified relative to traditional renewables. Solar, wind and hydro are all driven by the radiative force of the sun and its heating effects on the Earth. By contrast, tidal flows are caused principally by the gravitational dance of the moon and the Earth. In the extreme, even if the sun’s light were dimmed or wind patterns changed for some reason in the future, the tides will still rise and fall.

The case for tidal energy is strong. The real risk is short-sightedness in energy policy, in the UK and elsewhere. Regrettably, we often fail to don spectacles to correct for the optical flaw.

A sustainable energy policy needs an eye on the long term, beyond the distractions of either political opportunism or the faddism of financial markets. Rachel Carson, one of the founders of the modern environmental movement, said: “To stand at the edge of the sea, to sense the ebb and flow of the tides, is to have knowledge of things that are as nearly eternal as any earthly life can be.” Perhaps it is time for politicians and bankers to go down to the seas again.

Sophie Peck