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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.

Without storage all our solar, tidal, wind and solar based electricity is going to be pretty useless and we are running out of options.

Lithium is politically-economically unsafe, the price could rise greatly at any moment in time, the only reason the price has been dropping is to draw the world into its dependence for the financial trap.

Hydrogen is almost totally produced from carbon fuels at the moment, mass generation from water or air has not been resolved, disposal of waste oxygen could be a problem if produced on massive scales. Grid level storage is limited in locations.

Hydro is not feasible.

Thermal sand pits aren't being looked at in this country and would probably meat a lot of environmental barriers. Some parts of the country haven't got suitable locations.

Cryo-storage seems far fetched in massive scales.

Mechanical storage would be large in physical volume and number of sites.

That basically leaves synfuels based on CO2 conversion, I can't find the efficiency figures. Liquid carbon fuels have a lot of advantages, energy density being the main one followed closely by convenience.

The only other thoughts I've been having is undersea/underwater storage of gases, below a certain depth the gas becomes neutral then negatively buoyant so would only require weak containerisation such as bladders around those depths.

"Mechanical storage would be large in physical volume and number of sites"

The UK uses about 1 TWh a day of electrical energy. To run 100% on intermittent renewable energy we probably need to store ten times that 10 TWh

Now a 360 metre tower with a a hundred tonne weight will store 100 kWh Let's assume its 10 metres by 100 metres Ten of those taking 1,000 square metres would store 1 MWh. A GWh is 1000, times a MWh so to store a GW would take a million square metres. But we are not there yet.

A TWh is a thousand GWh so to store a TWh in this way requires a thousand million square metres and to reach our required storage capability we need 10,thousand million square metres of land.

So in a single building we are talking about a structure taller than the tallest building in the UK, but covering an area 100 km by 100 km. Even split into ten thousand units this would involve 10,000 buildings, each covering a square kilometre of land.

I don't believe mechanical storage is even close to being feasible.

Contrast this with hydrogen storage. Electricity should be converted to hydrogen as close to turbines / solar farms as possible. This can now be done at 95% efficiency - comparable with the efficiency of an electrical transformer. This hydrogen could be stored in solution mined caverns in deep salt strata at high pressure. Caverns of up to a million cubic metres are feasible and at 350 bar pressure could store a TWh. Ten of these would meet our required 10 TWh storage.

Pumping to high pressure takes about 4% of the energy in the gas, assuming industrial compressors are reasonably efficient, and this energy is in theory recoverable, although it probably won't be worth the effort.

The technology is widely used for storing natural gas and in much lower quantities for hydrogen so it is proven to work. The caverns are quick to create, and involve very little use of land - merely a valve head building. It is also possible to use exhausted natural gas fields to store hydrogen. The Rough gas field off the west cost of the UK has been proposed for this.

Conversion back to electricity can be done at about 60% efficiency, the remaining 40% appearing as heat, but a better solution is to pipe pure hydrogen to the user where this 'waste heat' can be used for space or water heating. We use about five times as much energy in heating as in electrical uses so using a Fuel an efficient fuel-cell based CHP unit would have to convert ost of the electrical output back to heat in resistance heaters. However, a more practical solution would be to use less expensive much less efficient fuel cells in the CHP unit. It is worth noting that moving large amounts of energy in electrical form is not very efficient. Even at high voltages, we lose about 10% of the electricity in transmission losses on average. Gas, bu contrast is far more efficient and transmission losses are negligible.

Fears of explosions and leakages are ludicrously exaggerated. We in the UK used 60% or more hydrogen for 150 years or more in coal gas. We have experience of it and it worked even without modern additions like flame failure detectors and excess flow shut off valves etc.

I can't see any other technology that would meet our needs when you do the necessary sums to this sort of level.