The Hinckley point nuclear deal is comically badly managed, and two EDF executives were so opposed to it, they resigned before the contract was signed.

All of it is down to the creative accounting of the conservative government to demonstrate that they eliminated the deficit.

Instead of financing the construction directly and purchasing the plant as "turn-key" asset, they forced EDF to take a multi-decade loan and agreed a price of electricity decades in the future that would enable EDF to pay back that loan. This doubled or triples the cost.

http://www.bbc.com/news/business-35741772

What's 'a ton' of pumped storage? Thats doesn't mean much. Can it can back up at least 16GWh, the equivalent of a single nuclear reactor's output over night. I have never heard of a project of this magnitude that wasn't just on the drawing board.

The reason Hinkley was structured as it was is because every other nuclear decomissioning results in socialising the cost to the state. This was intended to ensure that was not the case - despite the massive state subsidy. Which rather brings us to the normality of nuclear - the costs are always indicative of comical mismanagement, overrun and very often completely ignoring the decommissioning entirely. So it never, ever brings electricity at the alleged cost it can in the developed world - decommissioning makes a complete mockery of the figures, every damn time.

Considering Dinorwig cost £425m in the 1980s to get around 10GWh, even allowing for inflation and construction costs rising much in excess, there should be easily enough for multiple times 16GWh from $89bn even with major overruns. Hence "a ton". Probably enough to derive most generation from wind with more than adequate storage underlying it.

Clearly that needs suitable geography for several sites, but considering there were two backup sites within 10mi of Dinorwig should the main site prove unsuitable, and given the geography of the UK those should not be lacking. I know where I would spend my money given the outlook for renewable costs - absolutely not on nuclear. I was once quite keen in my naive twenties.

That is assuming you have the suitable terrain and don't have a problem with forcibly moving the inhabitants - its not the 50/60's the locals might not just pack up and move.

In some or even many cases neither need necessarily apply.

It doesn't always have to be a populated valley that gets dammed. There's a decent selection of disused quarries, maybe some of the Highland lochs that have potential to create something like Dinorwig at minimal disruption to environment once complete. What I don't know is how those constructions compare in today's money to alternatives. Still, £70bn brings an awful lot of choices, especially when lifespan is indefinite, just periodic turbine replacements.

If the geography isn't available there's the Netherlands project that's pumped storage on entirely flat land. Involves building an artificial lake, with a cavern and turbines below it. Suitable rock for the cavern is quite a long way down, which adds to the cost, but also adds to the head so it should end up with significant capacity. As far as I know it is the first such scheme, so costs are projection only at this stage, but it looks pretty interesting if it turns out to be viable economically: https://o-pac.nl

Or the UK company that has a plan involving winching weights (thousands of tonnes) up and down disused mine shafts. The open question of course is how many of the world's thousands of disused mine shafts are going to be viable. If viable the advantage seems to be very low surface profile.

All these large-scale energy storage projects are in their infancy. I haven't heard of anyone breaking ground on a project multi-GWh capacilty. Until that happens, it's all hypothetical.

Also, I am no expert on the subject, but digging out underground reservoir sounds expensive.

Dinorwig is 10GWh. There were two backup sites chosen in the same immediate area to cover the case the main site had proved impractical. Many years have passed so it's unlikely they're still there, but geography is not lacking if the political will were there.

There is still bad feeling in wales about some of the valleys that where flooded in the 60's.

With devolved government now in Wales and Scotland and new Pumped storage will face more push back

Given rule changes even without devolved government repeats of the Liverpool reservoir would be much harder. Dinorwig used already existing disused quarries - not flooding a pristine valley.

In the case of Scotland it's been the Scottish government looking at using lochs. No idea what the case is in Wales.

Your version of head assumes discharge into bedrock. Are they building a cavern of many cubic hectares down there too?

That seems to be the plan - enough capacity to store the whole topside lake, which seems to be planned at 500m x 500m (depth 10m). No idea how feasible or economic it will be compared to caverns from hollowing out a mountainside.