The tide is turning for tidal?

[Moxi]

I agree the Severn has a difficult upstream system but as the EA and others are now realising part of the solution to the bad practice of building on flood plains is to slow down water in tertiary and secondary tributaries feeding into the major rivers. Paying Farmers to allow upland areas to return to bog is helping as is the re-introduction of beavers to some parts of the UK but theres also the opportunity to have a whole raft of upstream hydro turbines and impounding ponds to slow water down and produce power.

On the Severn flood plain you could still have a barrage which would help prevent flooding when high tides coincide with high inland rainfall - much the same as the Thames barrier works. The rest of the time the barrage could generate using the ebb and flow of the tides.

Most estuaries would not lend themselves to a full barrage, but lagoon systems of varying sizes would be practical for most areas. Silt fouling is a problem with a solution - in fresh and brackish water systems the silt can be reclaimed back to the farmland from whence it was stripped - it will have a cost but that cost is less than soils irrevocably lost to the oceans.

As I said before, the mechanics of tidal and hydro systems are well understood and barring the various Governments of the day and their departments being cost and opportunity averse we could have a seriously reliable contributor to power needs, flood control and water for treatment in to wholesome drinking water. Instead of which we suffer wet flooded winters, damage to property and land, the loss of amenity from fresh water washed out to sea with sediments and soils from the fields, and lost energy production.

Clearly infrastructure of this nature takes time and therefore should be outside the portfolio of short-sighted ministers who arguably only have interest in whas gets them re-elected for the next 5 year term. - that or change the parliamentary system - I dont care which but clearly the Government system we have these days seems to no longer be not fit for purpose.

Moxi

[Fintray]

Think you've got an extra "not" in that last sentence Moxi.

[Oldgreybeard]

The problem with a whole Severn barrage is that, whichever way it's arranged, the mean water level at the lower end of the Severn would be higher. This is the thing that really seems to mess up the hydrography, as when the tide comes in the Severn drainage rate under flood conditions decreases, when it goes out the drainage rate increases. A barrage will reduce the height of the high tide peaks, but will also increase the height of the low tide dips, so the net result is decrease in flow velocity and a longer period when water backs up the whole of the Severn under flood conditions.

It's this dynamic impact on the flow during flood conditions that is one of the main challenges, and a part of the reason why alternative schemes, like those put forward by several environmental groups, like Friends of the Earth, have suggested using isolated lagoon arrangements, that reduce the impact on flow into the Bristol Channel and don't impact the mean tidal level in the lower reaches of the Severn.

The snag with these is that their output is a lot lower, maybe 3GW or so in total, compared with up to 15GW for the downstream barrage option.

[Moxi]

OGB,

Totally agree that the severn is more complex than a single barrage but the fact remains that lagoons over a section of the Severn are a workable way to generate power - I for one wouldn't mind having 3GW at the bottom of the garden!

Lets also remember that there are a few other rivers besides the Severn quite a few of which don't have issues with a full barrage system, local to me there are the rivers at Barmouth and Pothmadog that are both three quarters closed at the mouth of the estuary by man-made impounding structures.

At both sites this was done to allow railway lines to cross in Victorian times.

Both these estuaries could easily have tidal turbines installed, we don't have to build one large structure, indeed as noted before its preferable to have such generation distributed around the national grid infrastructure to assist in load management and transmission.

What if the UK installed an Archimedean screw generator on every suitable water course in the uk, on longer rivers there could be multiple units at reasonable intervals.

This all takes energy from the water - especially in winter when flood control is required and coincides with when we normally need more heating less energy in the water means slower flow so tactical use of these generators could allow the EA to control water flow from highland areas to the flood plains and limit flooding.

Done right we would benefit many times over from the investment, jobs, power, flood management etc

If we considered options for small pumped hydro across the country we could benefit even more by securing fresh water and power

Moxi

[dan_b]

I'm still somewhat scarred by the opposition to, and eventual scrapping of, the small scale hydro scheme that I had backed at Teddington Lock, on the Thames. It seems kind of obvious now that the main opposition to, and funder of, all the NIMBY campaigning against was driven by The Lensbury Club (which is owned by Shell) - who protested that the hydro scheme would spoil the view and make excessive noise. This on an already industrialised part of the river with the weir scheme and the tidal locks! Muppets. Anyway, they got the planning application approval overturned on appeal at the High Court, the scheme never went ahead and I lost a fair amount of cash.

[Oldgreybeard]

I'm still somewhat scarred by the opposition to, and eventual scrapping of, the small scale hydro scheme that I had backed at Teddington Lock, on the Thames. It seems kind of obvious now that the main opposition to, and funder of, all the NIMBY campaigning against was driven by The Lensbury Club (which is owned by Shell) - who protested that the hydro scheme would spoil the view and make excessive noise. This on an already industrialised part of the river with the weir scheme and the tidal locks! Muppets. Anyway, they got the planning application approval overturned on appeal at the High Court, the scheme never went ahead and I lost a fair amount of cash.

Much the same here. I got involved in a small scale hydro system a few miles away, that was planning to convert an old mill into an Archimedean screw generator. Massive amount of opposition and red tape, such that the community group eventually just walked away from the ruined mill and left it to fall into further disrepair.

[Joeboy]

I'm still somewhat scarred by the opposition to, and eventual scrapping of, the small scale hydro scheme that I had backed at Teddington Lock, on the Thames. It seems kind of obvious now that the main opposition to, and funder of, all the NIMBY campaigning against was driven by The Lensbury Club (which is owned by Shell) - who protested that the hydro scheme would spoil the view and make excessive noise. This on an already industrialised part of the river with the weir scheme and the tidal locks! Muppets. Anyway, they got the planning application approval overturned on appeal at the High Court, the scheme never went ahead and I lost a fair amount of cash.

Much the same here. I got involved in a small scale hydro system a few miles away, that was planning to convert an old mill into an Archimedean screw generator. Massive amount of opposition and red tape, such that the community group eventually just walked away from the ruined mill and left it to fall into further disrepair.

Both stories, absolutely soul destroying...
Gotta keep doing the thing in front of us. Would nice to think if we have any fresh hydro projects or resurrection in old projects due to a change in political winds thT the news is spread here early?

[AE-NMidlands]

Would nice to think if we have any fresh hydro projects or resurrection in old projects due to a change in political winds thT the news is spread here early?

https://nmce.co.uk/ (local to me) looks promising, also Dane Valley Hydro is looking at a phase 2 which will be a second screw and pv on roofs nearby. https://www.congletonhydro.co.uk/volunt ... congleton/ was an earlier notification, there is a new one for members but it's not on line yet.

I'm (now) not convinced by tidal because a) it's not often in phase with demand and b) it can destroy inter-tidal habitats which waders rely on. Our greed for power shoudn't be satisfied at the expense of wildlife.
Big barrages obviously fail test (b) and even smaller lagoons like the Swansea one have problems with (a) even if they swing/generate both ways.
A

[Moxi]

Given the tidal range around Britain its got to coincide with demand at some points and if not then either don't generate or generate and export to Europe?

Part of the problem with any new infrastructure appears to be the model UK government uses to fund them, private finance expects a quick and lucrative payback an isn't interested in efficiency or environment or diversification just "whats in it for me" its the. Its a flawed mechanism for essential infrastructure and we wouldn't be in the state we are today if we hadn't sold the CEGB off, but thats water under the bridge now.

With a balanced design we can obtain some power from tidal and riverine (hydro) whilst maintaining a reasonable and diverse intertidal/ river environment - indeed you could argue that if done right some areas of intertidal habitat could be protected from the winter storms and increasing sea levels that otherwise risk their existence ?

Lets also remember that large schemes like Hinckley C also affect the intertidal habitat as well as the fully marine environment for many miles down and upstream in terms of thermal pollution and changes to water column velocities.

We need a change in the way we think about national infrastructure.

Moxi

[Mart]

I'd suggest the exact opposite, that tidal lagoons are more often in phase with demand than not. In fact looking at the evening peak 4pm to 8pm, then tidal lagoons would always be generating during part of this period, as they generate for four 3.5hr periods per day, with four 2.5hr periods of slack tide. So even in the worst case scenario they would generate for 1.5hrs out of the 4hr peak, and in the best, for 3.5hrs out of the 4.

[Edit - Also, the tidal lagoons will not all operate at the same time. And whilst the Severn has the best resources, lagoons on the East coast of the UK, would (I think?) have the opposite cycle timewise.]

Fourteen hours of generation per day, every day, and predictable is excellent. Taking the issue a tad further, purely for theoretical purposes, a co-located battery with a 2.5hr discharge would have good economics (four cycles per day) and porvide 24/7 generation. Yes the amount of genertaion per day will vary with the movement of the Moon, but again predictable.

Also worth pointing out that tidal lagoons could bring benefits to the areas they are located. Both Swansea and cardiff built barrages purely for aesthetic purposes (I visted the Cardiff one with work, whilst under construction). The cardiff Docks area went from one of the poorest parts of Cardiff to the place to be, with business headquarters and apartment blocks.

The Swansea tidal scheme, also involves water front property development (floating properties, I think?) floating PV and other parts that would help the economics.

However Swansea is really just a proof of concept with generating costs possibly as high as nuclear, whereas the 10x larger Cardiff scheme should generate at half the cost (double the circumference of a circle (barrage wall) and quadruple the area (water contained)).