Two cheers for Swansea’s tidal lagoon

Britain’s west coast is facing a revolutionary change. If renewable energy advocates get their way, swaths of shoreline will soon be peppered with giant barrages designed to turn the power of the sea into electricity for our homes and factories. These tidal lagoons could supply more than 10% of the nation’s electricity, it is claimed.

Last week former energy minister Charles Hendry published a review that strongly backed the construction of a £1.3 billion prototype lagoon in Swansea Bay. The trial project was a “no regrets option”, Hendry concluded.

Not everyone is happy, however. Critics say the price tag is massive and compares with the huge cost of the highly controversial Hinkley C nuclear power station that was recently approved by Theresa May’s government. It would be better to wait for technological improvements in other renewable energy sources – in particular solar and wind – to be achieved and to use these as the backbone of Britain’s renewable energy generation, they argued.

For their part, renewable energy experts say the Swansea Bay project should only be considered as the forerunner of a set of tidal lagoons whose individual costs would plummet as economies of scale kicked in. As Professor Paul Ekins, at University College London, put it: “One tidal lagoon is neither here nor there. They only make sense if they come as a fleet.”

The differing views underline the stark dilemma that Britain now faces. Thanks to the 2008 Climate Change Act, the nation is now committed to reducing its greenhouse gas emissions by 80% by the year 2050: an enormous task. Old coal, gas and oil power stations will have to be closed and replaced with renewable plants capable of generating billions of watts of electricity.

The trouble is that very little has been done in the past decade to trigger changes that might wean us of our fossil fuel addiction. And time is running out. As Chris Binnie, a visiting professor of engineering at Exeter University, put it: “None of the governments we have had since 2008 have had a coherent policy on how to meet our requirement to make such cuts in emissions by 2050.”

Hence the excitement about tidal lagoons. These generate electricity from the natural ebb and flow of the tides. Rising water flows into dams many miles in length, driving turbines. It is then held back behind walls as the tide recedes before being released to drive the turbines again, generating thousands of megawatts of power. For good measure, they would emit little carbon dioxide and offer the prospect of creating thousands of new jobs in Wales and west England.

The problem is that, as Ekins points out, their go-ahead only makes sense if the government commits to building half a dozen – and in recent years, ministers have proved to be woefully inconsistent in their approach to backing renewable power projects. Take the decision by David Cameron’s government last year to axe a range of measures designed to boost the sector. These included subsidies for solar power and support of energy efficient house building. The scrapping of the latter – the UK zero-carbon homes scheme – was especially egregious, said Ekins. Established in 2006, the scheme would have ensured dwellings, built from 2016 onwards, would generate as much energy on-site – through renewable sources, such as wind or solar power – as they would use in heating, hot water, lighting and ventilation. Then, in 2015, it was scrapped.

“The government gave a 10-year signal to investors and then pulled the plug after nine years,” said Ekins. “How can you expect to be taken seriously in your next policy pronouncement in the same area?”

Another example of fickle government policy has been the stalled development of Carbon Capture and Storage (CCS) schemes that would collect carbon dioxide emissions from fossil fuel power plants, liquify them and store them underground. The technology would prevent carbon dioxide reaching the atmosphere but could also help reduce existing levels, said Bob Ward of the Grantham Research Institute on Climate Change, London.

“Wood and other biological material normally rots and return their carbon dioxide content to the air. But if you burned this biomass and used CCS to capture the carbon dioxide you would be preventing it from reaching the atmosphere. You would be creating negative emission – which could be extremely useful for there may be some emissions from industry and agriculture for which we can find no substitutes. We could use CCS to create negative emissions to compensate.” Last year, however, all support for work on CCS was axed by the government.

It remains to be seen if tidal lagoons suffer a similar fate. As Robert Gross, director of policy at Energy Futures Lab, Imperial College London, put it: “Private investors welcome secure and long-term investments in energy infrastructure but only if, and it’s a big if, government really thinks long term.”

Question marks over commitment are not the only problem facing the government’s energy policy, however. There is also the issue of energy storage. Renewable power sources suffer because their outputs are often intermittent. Solar panels are fairly useless on a gloomy winter’s day in Glasgow while wind turbines cannot turn when the weather is calm. Methods to store energy are going to be vital if the UK generates most of its electricity from renewable sources.

New generations of lithium-iron batteries have had encouraging results though their capacities remain limited. By contrast, pump storage projects already have a strong track record. These schemes involve pumping water up to reservoirs in hills using electricity generated when conditions are optimal - for example when it is windy or sunny - but demand is low. Then, when generation becomes difficult and demand increases, the water is released and passed into turbines to generate power.

At present Britain has a handful of such pump-storage schemes, including a major facility at Ben Cruachan, near Oban. Several more will be needed as our reliance on renewable energy increases. “Both the Peak District and the Exmoor National Park have been pinpointed as possible sites,” said Binnie. However, creating reservoirs there would be highly controversial. “It’s another aspect of the difficult choices we will have to make but which we do not seem to be considering at all at present,” Binnie added.

These issues mostly focus on relatively remote areas. However, Professor AbuBakr Bahaj, head of the energy and climate change group at Southampton University, believes that approach is misplaced. An urban response to climate change mitigation is what is required. “Most of the nation’s energy is consumed in cities and that is where we should be thinking of generating it,” he said.

Bahaj envisages UK cities having the roofs of buildings, offices and homes covered with cheap but highly efficient solar panels. “I have done an analysis of Southampton and if you fitted all its roofs with solar power panels you could supply the city with 25% of its electricity. You could fit a panel to your home that supplied you with 3 to 4 kilowatts of power and which you could connect to the grid. If you took this approach, you could get a very good return for your money.”

Whatever approach is taken, one thing is clear, say energy experts: the kind of nation – both in its cities and in the countryside – that our children live in will be very different one from the country we currently inhabit. Radical changes to our infrastructure lie ahead. The sooner these are accepted, the better will be our chances of meeting our climate change obligation.

• This article was amended on 15 January 2017. An earlier version referred to “renewable plants capable of generating billions of gigawatts of electricity”. This has been corrected.