Tidal Power

Construction of the SeaGen Tidal Stream Generator on Strangford Lough, Co. Down, NI. Commissioned 2008, Decommissioned 2019.
Tidal energy project, Strangford Lough – photo by Aubrey Dale, used under
Creative Commons Attribution-Share Alike 2.0

Generating Electricity From the Sea

Britain is an Island, so why don’t we generate electricity from the sea? We now have plenty of solar and wind power generation in the UK. That may seem great, but the problem is that no electricity is generated if there is neither sun nor wind. It is obvious that we need a mix of methods to make electricity which will work all of the time. 

To discuss electricity generation, you must first understand the difference between peak and baseload generation. Baseload is the minimum amount of electricity that the country needs all of the time. Peak electricity is the maximum demand (when it is cold in the early evening in winter).

The demand for electricity varies during the day and also between the seasons and the name of the game is to match exactly supply and demand. People do not want power cuts, but the industry does not want to spend money generating electricity which simply goes to waste. 

So what happens now when there is a massive sudden demand for electricity as everyone decides to switch on the TV and boil the kettle (or cook their Christmas dinner)? As I write this at 6.35pm on a Sunday evening, the UK is using 35.9 gigawatts (GW), of which approx 31% is being generated by wind and 31% by gas, and the rest by other means (such as nuclear and interconnection with other countries). The National Grid live website is full of interesting live statistics.

Since it is very important that we divest from any fossil fuels, we must stop using gas quickly to top up the electricity supply when demand rises. This means that all our baseload electricity must be generated using green methods.

Unfortunately wind power cannot be classified as baseload, but can still be usefully used for peak generation. Indeed the problem is that we are now generating more wind power than we can actually use. So I suggest that it can be used for making green hydrogen, when not delivered to the National Grid.

Why Not Wind And Waves?

I have often wondered why all these wind turbines out at sea can’t also be fitted with a wave power gadget at the right level on their poles, which would mean that each one could generate more electric power. I have never had a straight answer from any of the technical people. Of course we all know that the salty sea is hard on any machinery, but that doesn’t stop the shipping.

Another way of meeting peak demand is to pump water up to a storage lake and then generate electricity through turbines when it flows downhill to meet peak demand. There is one such site in mid Wales. That provides 3.6% of the current electricity supply, and biomass (a relatively new technology for electricity generation) supplies 4.5%.

How to deliver the green baseload power that we need? At present Nuclear is supplying 16.9%, but this comes at huge cost, and some older power stations need to be retired. In recent years around 20% of our electricity was supplied by Nuclear power stations – although about half of this capacity will be retired by 2025, including Dungeness power station in Kent.

This is why Hinkley C power station is being built at a cost of £22 billion. It will supply approximately 7% of our demand for electricity and will start operating before 2025.

Many people disapprove of nuclear power stations, believing the technology might heap up trouble in the future, especially the difficult decision-making about how to dispose of the radioactive waste safely. Germany came unstuck by banning Nuclear, but is now having to use more fossil fuels such as coal and gas to deal with demand.

When comparing the cost of the Hinkley C nuclear plant, many people point out that building the Severn Barrage would have cost £3.8 billion and would have supplied 20% of the UK electricity requirement.

The scheme was rejected because it would affect wildlife (mainly birds). Yet it could still be built without the wildlife downside and produce 10% of our electricity needs – which is more than Hinkley Point C nuclear power station.

Diagram from 1921 of the proposed Severn River Tidal Power project, rejected because of its negative impact on wildlife.
Severn River Tidal Power Project 1921 – Unknown author, Public domain

This brings me to the point of using tidal power – which is constant and could supply our baseload requirements. There are several suitable sites around the UK – not only on the River Severn, but also in South Wales, and between the Orkney Isles and Northern Scotland, and also in the Shetland Isles.

The government has completely ignored a report by Charles Hendry given to Parliament in 2017 on the role of tidal power. He recommended that tidal power should certainly be developed as part of the low-carbon energy mix. Once built, the power for many years to come would effectively be free.

Tidal power doesn’t compare with nuclear (which can be “on” all the time) because there are two tides per day. So electricity can be generated predictably for several hours each day and those hours are known in advance.

An assessment of tidal power by the National Infrastructure Commission compared the price of electricity at various times in the future and wrongly compared it to wind generation (which is rapidly coming down in price). They completely missed the point about the need for non-carbon baseload generation. Yet when they did compare the price of the electricity, tidal was still cheaper than Hinkley Point C nuclear power.

Now it is time for a new analysis which compares the price of electricity generated by the smaller nuclear plants as proposed by Rolls Royce and the various tidal power proposals.

What the government fails to understand is that if you develop a new technology, then you can usually export it to other countries (as the Danes did with wind turbines). By failing to do anything about tidal power generation, they have allowed other countries, such as South Korea, to get ahead with this technology.