Why not tidal power?

[IsleofRum]

We have wind turbines and they are good at generating electricity when the wind blows, but the tide comes in and out twice(three times in some parts) a day. In some areas (pentland firth, north channel, Western isles) the tide stream is calculable, known to mariners and anyone who understands charts.
Why do we not exploit this to generate wave and tidal power?

There is a tidal power project in Swansea I think

@deplorabelle

There is a tidal power project in Swansea I think

That got scrapped because the government wouldn't fund the subsidies it needed.

www.bbc.co.uk/news/uk-wales-south-west-wales-44589083

Places like the Pentland Firth are extremely inhospitable for both engineers and equipment. Salt water with vast amounts of uncontrolled energy running through it, plus weather. I think that's the main reason it's not been cracked yet. But it's definitely being worked on.

It's mind boggling isn't it? I'm sure I remember a documentary years ago saying that the tidal surge up the Bristol channel is so strong that they estimated that a tidal power station cited there could generate 7% of the total UK needs.

I wonder if other leaders at Glasgow are listening to Boris blab on with his fake seriousness, thinking "well who made you Greta, you've done fuck all to wean yourself off fossil fuels so far, despite running a country surrounded by sea, full of hills and these days pretty sunny in large areas."

The one is wales was scrapped, but there are so many engineers working on the solution, Google sea snakes.

It’s being worked on! Everything’s too late, really – we’re trying to suddenly scale up tidal, wind, solar and hydrogen, and battery storage, and a million other issues, with not enough funding or skills or time. It’s not as simple as: waves! Electricity! Worldwide!

There was one in NI, but this article says it was decommissioned. www.power-technology.com/projects/strangford-lough/

Some of the older ideas for harnessing tidal power would have devastated the rich coastal habitats.
Hopefully there will be newer ideas which are truly 'environmentally friendly'.

The amount of structural steel is great relative to the amount of electricity generated and also the engineering challenges are substantial.

With tidal barrier schemes a substantial tidal drop is required along with a sizeable barrier, and again the relative amount of electricity generated is small compared to say wind.

Lots of reasons. Most fast flowing tidal streams are in relatively shallow water, this makes large submerged turbines difficult to position, especially in a shipping lane. Deep water fast flows are relatively few and the engineering is incredibly expensive. Maintenance underwater is difficult, raising the turbine is expensive. There is a huge amount of debris in coastal water that could damage the turbine.

There is one in the Pentland Firth — the Meygen Project.

But the way you apply for government grants changed. Marine energy used to have a ring-fenced pot, then it was changed to all green energy generation. Marine is a lot less developed, and therefore more expensive, than wind power, so they weren't competitive anymore. I think they're stuck in Phase 2 trials.

Apologies for resurrecting this thread from last year, but the current energy crisis got me thinking about tidal power - predictable, year-round energy along hundreds of miles of our island coasts that could be harnessed.

I'd guess that the huge costs are becoming more and more affordable in the light of the current situation.

I am not sure about tidal energy but there was a group trying to put electricity generating turbines in the river near me. The project was discontinued due to cost vs amount of power generated, and difficulty siting the turbines. I would imagine some of the same issues come into play for tidal schemes.

With the energy situation today, the cost benefit ratio may see more of these kinds of projects going ahead. Although the cost of construction materials are really high as well, so not sure.

I saw this thread title and was about to say exactly what I said last time.

@limer see my previous post but I'll also add that while the tides round the UK are fast compared to many others they are still relatively slow, typically 0.5 to 1 m/s in a relatively few places up to 3 m/s. A lot of people don't realise there is also a huge variation in the tides between neaps and springs, and there are also slack periods at both and low tide.

Fundamentally is doesn't make commercial sense. The overall energy in moving water can be immense but tapping into it is very difficult.

I recall a Horizon episode years ago called Professor Salter's Duck. He'd invented a floating device about the size of an oil drum that sat rocking on the surface even in gentle seas anything above flat calm, with a device inside using the kinetic enery from that movement to generate a small amount of electricity. The plan was to connect hundreds of then together to scale up the electricity produced. It seemed hopeful at he time but I don't know what happened to it.

im in the north there’s been talk of one for years but always gets squashed due to wild life environmental reasons
within 80 mile radius we’ve had the following
all objected to
solar farm
wind farm ( had to do a very small version)
coal mine
Fracking
Nuclear (already got 2 due to be decommissioned)
unfortunately we want the energy but won’t accept the solution

They have a interesting power station in north wales which while isn’t tidal works on a similar principle of hydroelectricity. I did a power station tour a long time ago and they pump the water up high and store it, when they need electricity they let the water drop down and that rush of water creates energy. They were certainly singing it’s praises during the tour about how much energy is produced. So not sure why this hasn’t been replicated.

It is being used/harnessed already - but not on a big scale - nor is it ever likely to be. Even Nova Scotia tides wouldn’t power Canada.

marine.gov.scot/sma/assessment/case-study-nova-innovation-shetland-tidal-array

I think Bristol channel's tide can offer a great amount of power.
We are talking of thousands upon thousands of tonnes of water running in and out.
It is not easy peasy, but there are two bridges, a tunnel, and ports and quays alongside it, so surely placing turbines could not be that difficult, at least not impossible.

@MushMonster according to a 2019 study, commercial-scale tidal energy is estimated to cost $130-$280 per megawatt-hour, compared to $20 per megawatt-hour for wind. If you take the median $210 that makes tidal energy 10x the cost of wind. Link here

Tidal is expensive but predictable

Building enough wind to account for its unpredictability probably means building 10 times more than you would otherwise think

Which makes predictable tide look a lot more attractive

If you mean pumped hydro (Electric Mountain near Llanberis) that's a very different thing - it takes more energy to pump the water up to the reservoir than you get back when it's released. It doesn't generate energy, it's a useful way to store it to balance the load. More energy storage will be needed to work alongside renewables but pumped hydro needs an appropriate location and is obviously expensive to build. There are quite a few around the world, the Swiss have recently completed a big new one and I think there's another at some stage of development in Scotland

There was a really interesting I side Science podcast all about tidal power and why it’s hard to implement - www.bbc.co.uk/sounds/play/m0016pw1?partner=uk.co.bbc&origin=share-mobile

Inside Science - on iplayer