We visited the Dinorwic pumped storage sytem in Wales a few years ago. We were told that more electricity was used pumping the water uphill to the storage area than was generated when it was released through the tubines.
Think about that.
It worked because the water was pumped up when demand for electicity was low (late at night/early morning) and released to generate power when power demand was at its highest.
From Katie59's post I deduce that something similar happens when you compress air, more power is needed for compression than is generated when it is released.
The biggest danger from big batteries, however efficient they are, is the danger of explosions- and a big battery exploding would do a lot of damage over a large area.
You may remember a few years ago Samsung developed a small high capacity battery for one of its mobile phones, but it had to be withdrawn after a few months because of its tendency to explode, especially on planes.
At the end of the day there is no easy way out of the current system of hydrocarbon generated electricity. No matter how many wind turbines we build offshore all round the British Isles, The British Isles are often covered by large weather systems that mean the wind conditions are the same, whether on the furthest northern top of the Shetlands to the southern most tip of the Scilly Islands and in all our coastal waters.
I regularly check a site called GridWatch gridwatch.co.uk/ which gives the source of all the electricity the country is consuming at any given time. Over the last fortnight, on different days, it has been as much as 40% + of all our power and as little as 3%. It means that we will always need to have nearly as much back up capacity as there is wind capacity installed to provide support for when the wind doesn't blow.
Like it or not, until the Holy Grail of Fusion is sorted, the only way we can meet the exponentially growing demand for electricity, as everything now powered by hydrocarbons moves to electricity, is nuclear power.
Not the huge behemoths costing billions of £s and requiring Chinese technology, but the much smaller modular systems championed by Rolls Royce with the nuclear reactor based on their expertise in designing the engines for our nuclear submarines which have been in use for decades.
How do you acknowledge Easter.
Mothers Day - interested in opinions