Just over three years ago, UK Government effectively killed off a bid to build a tidal lagoon in Swansea Bay by refusing to guarantee the price of electricity it generated that its backers were demanding.

With energy prices now skyrocketing the idea of a reliable, sustainable and green supply of energy on our doorstep is looking more appealing than ever.

According to emeritus professor at Cardiff Universities School of Engineering, Roger Falconer, using Wales' incredible coast line could be a gamechanger in solving the UK's energy crisis. He believes that tidal power should be given the same attention as nuclear, solar and wind when it comes to making our energy green.

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What would tidal lagoons in Wales look like?

Put very simply tidal lagoons generate power using the tides. dams are put under the water which contain turbines. When the water moves between high and low tide (and visa versa) these turbines are turned which generate electricity. No fossil fuels are involved at all therefore this energy doesn't contribute to climate change.

Speaking to WalesOnline Professor Falconer suggests that a tidel lagoon south of the Severn Estuary and a lagoon in North Wales near Colwyn Bay could generate 10% of all the UK's energy.

He said: "This is a credible option that deserves the same attention as other options - now more than ever. This would give us complete independence and predictability. It would make a major contribution in my mind to UK Ltd energy security and Wales can play a very important part in that."

The area of North Wales potentially acting as a lagoon

Why is this so appealing?

One of the key advantages of tidal power is that it is predictable. Unlike wind and solar energy, they are not weather dependent. The moon is not going anywhere therefore tidal energy is more reliable.

"When something is predictable it becomes very attractive," said Professor Falconer. "Wind is not predictable. Solar panels are not as much use in the middle of winter because the daylight is massively reduced and you need power much more in the middle of winter than you do in the middle of summer.

"Though there is disadvantage of tidal power because you a spring tide you have a very large tidal range with lots of power then later in the 14-day cycle you have a lot less power."

The good thing about having lagoons in the north and south of Wales is that high and low tide are not at exactly the same time. This means that there will not be sudden spikes and then falls in energy supply but a more continuous source.

Professor Falconer said: "If you built a lagoon on the South Wales coast or in the Bristol Channel and you build a lagoon off the North Wales coast they are out of phase. So in other words high tide occurs in the Bristol Channel about 4 hours ahead in Llandudno for example. If you were to build the two lagoons of the one in the Bristol Channel and one in North Wales those two would complement each other.

Visualisation of the wall at Swansea Bay's proposed (but now rejected) tidal lagoon

What are the challenges and what are the answers?

Since the the early 2010's when a small pilot lagoon project in Swansea Bay was first proposed - planned as the first of three lagoons in the Severn Estuary, there have been according to Professor Falconer advancements that makes tidal power both more appealing and better value for money.

This includes using artificial intelligence (AI) to manage the flow through the turbines to target peak demand hours, different types of turbine to allow migrating fish through and flexible funding options to make the projects more appealing for investors.

"Using artificial intelligence techniques you could operate the system so in that you might have more power to produce more energy when it's needed - or example at 7am in the morning and between 7pm and 10pm at night..

Methods of optimising energy output using AI have shown an increase of energy output of around 40%," said Professor Falconer. "Developing construction techniques, including robotic methods, and repeat construction, can be expected to reduce future construction costs by 10 to 20%."

Professor Falconer believes that the overall effect of the improvements in energy output should reduce energy cost from the more economic tidal range schemes to around £100 per MWh which is comparable to nuclear energy - and on a par with current wholesale electricity prices in the UK.

Prof Falconer added that there were also improvements in how the tech impacted on fish.

He said: "When I was debating in 2012 about lagoons the showstopper was always fish. Migrating fish going to the Wye and Severn and so forth. The turbine developers have worked considerably on this and now have what they called triple regulated turbines. The ones that were proposed by Swansea Bay, as I understand it, operated at a fixed speed. So when the water was flowing through the turbines always go through the same speed.

"These new ones operate under variable speed which makes it much easier for fish to pass through the turbines. I'm not an expert in this area but this is my understanding. We now have a turbine which is much more attractive in terms of fish migration the amount of fish deaths."

He adds that because tidal range schemes are "mostly in areas of high unemployment", there could be benefits in terms of regeneration.

The table below shows key schemes currently being considered and what they could generate:

What about using the whole of the Severn Estuary through a barrage?

Professor Falconer had long been a proponent of using the Severn Estuary for tidal power through a barrage from Wales to England, enclosing the entire estuary. However he says he has now been persuaded that the environmental cost would be too high for the original plan..

He said: "The Severn Estuary in terms of just delivery of hydro power is very attractive. It has the second highest rising and falling tide in the world. But there are a long list of unique environmental characteristics in Severn Estuary so I would find it very difficult these days myself to justify damaging the aquatic environment and the ecology of the Severn Estuary.

"If you come out of the Severn Estuary which is basically from Lavernock Point to Hinkley Point C on the English side you still have a pretty large the tidal range. You have you still have the whole of the Welsh coastline South of the Severn Estuary which is not a site most special scientific interest."

One of the big issues about having tidal power in this area is the impact it will have on intertidal mudflats. When you drive over the Severn Bridge you will often see the incredible mudflats exposed by the tides. Estimates suggests that 50% of this could be lost with the original plans for a barrage in the estuary.

However, under that scheme the energy generation only happened on the ebb tide (when the tide is going out to sea) not the flood tide (when the tide is going inland). This no longer has to be the case according to Professor Falconer.

He said: "I was originally heavily involved in the Severn barrage project. the original scheme only produced power on the ebb tide.

"However the problem with that is is that there is is a huge loss of what they call intertidal mudflats. With the original scheme we were losing about 140km of intertidal mudflats if the scheme was to be built in the way it was originally proposed.

"As an engineer I thought I originally regarded it as secondary importance and felt for benefits of tidal energy far outweighed for loss of intertidal mudflats. But I started working more closely with the RSPB in particular and I learnt a lot from them that if you are going to to do this you might as well go for both n and flood generation. This will massively reduce the loss of intertidal habitats.

"It means that the tidal range is preserved upstream though it is delayed by three hours. With ebb generation only you are chopping off the bottom half of the tide. It will reduce the 10m tidal range of stream to about 5.

"The RSPB explain to me but it was an important feeding ground for birds and some of these birds were very rare and they put forward a very strong case to protect it at all costs. My then Cardiff University team found ebb and flood generation generated almost the same amount of power for much less habitat loss."

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