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Why is Steve Rotheram so keen to spend an estimated £6 billion damming the Mersey, causing massive disruption, to generate the same amount of energy that a medium sized wind arm in the Irish sea would produce at only £2 billion? This would involve no disruption and would be built in a fraction of teh time.

Has he lost his mind?

Because it generates employment and income for the region which is his job. I'm totally against it, the Mersey will silt up much more than it is now, I don't believe their dredging plan will be anywhere near enough.

They need to put tidal turbines in the area of the existing offshore wind turbines instead of destroying the Mersey.

But most of all they need to create mechanical storage, we already have the facilities to produce more than enough power, we just can't distribute it to the right places at the right time. Cheap mechanical storage in the correct locations will get energy to the right places at the right time without have to rebuild much of the the national grid which is part of the current plan.

We are in the ridiculous position of paying electricity generators huge sums of money not to generate electricity, storage will reduce that waste.

I asked the chief engineer of the last barrage project how much siltation he expected . His answer was that they'd lose 30% in ten years, even with constant dredging.

Storage is needed, but it needs to be in huge quantities. Terawatt hours, and many of them.

Mechanic storage is useless on this scale . The biggest pumped scheme in the world is in China and it manages only 40 GW. about one twenty fifth of just one TWh.

Hydrogen is the ONLY way to store that quantity, held at high pressure in solution mined caverns in deep salt strata. This is widely used for natural gas A single caver of a million cubic metres capacity is possible and at 350 bar it would hold the best part of a TWh.

There is good information on one near us at stublack in Cheshire. You'll find details of it on the internet easily enough.

I'm quite a fan of hydrogen but while its energy density by weight is brilliant, its energy density by volume is pretty poor. Also hydrogen molecules are a much smaller than natural gas so leakage in salt mines would be far worse. Distribution facilities are expensive because of the high pressure and high volume required.

Stublack will hold two days worth of natural gas, the same size facility for hydrogen would only be something like 6 hours if they are the same pressure.

By mechanical storage I was thinking of gravity storage using rock, its cheap, scaleable, simple, highly efficient and can be located anywhere. It is also the probably easiest and cheapest to maintain.

High temperature thermal storage using dry sand is also taking off, any reasonably deep old quarry can be filled with sand.

There is a lot of push for cryogenic storage of liquid air but I can't see it being that efficient, its going to be throwing thermal energy away at every stage unless you store and recycle the hot & cold. Also extreme cold and high pressures are not good bedfellows, things crack too easily.

The most obvious one cost wise is synfuels - synthetic petrol or other hydrocarbons. Utilising the existing storage and distribution infrastructure is a massive saving. Its carbon neutral to keep everyone happy but as yet not as efficient as other storage methods.

Liquid sulpher batteries look good apart from the requirement to try and keep the sulpher liquid, its a lot of downtime if they solidify.

If we are basing our renewable energy supplies on tidal, solar and wind power it is essential to build the storage facilities otherwise we are literally throwing both money and energy away.

Mechanical storage is not really on. From the top of my head, a tonne falling 35 metres stores 1 kWh. A TWh is a thousand million kWh .

I'll leave you to work out what a TWh mechanical store would look like.

A million cubic metres at 350 Bar of hydrogen deep underground will store a day's electricity fot teh UK

ERRATUM

I should have said a tonne falling 360 metres generates 1 KWh. The Beetham tower is about half that height. Apologies.