On Saturday, 13 August 2016 11:39:44 UTC+1, John Rumm wrote:
On 13/08/2016 00:32, Johnny B Good wrote:
On Fri, 12 Aug 2016 11:28:19 +0100, John Rumm wrote:

On 12/08/2016 08:51, dennis@home wrote:
On 11/08/2016 23:02, John Rumm wrote:
On 11/08/2016 17:58, Capitol wrote:

Read a Telegraph article today on these. Do they have a
future?

Nice in that they have a long life and should not lose capacity over
time. However the normal problem of energy density still exists - many
offer less than 1MJ per litre (compared to 43MJ/l for petrol)


I don't think they are intended to replace petrol.

Not suggesting they were, just illustrating that the energy density is
pretty low in relative terms.

Yes, very low compared to our highest energy density portable fuelling
option (setting aside the needs of rocketry) but I think it's some 2 or 3
orders of magnitude better than your typical hydro pumped storage option
in terms of land usage which is why the technology is being researched at
all.

Not just land usage, but also suitable geography. The space is not much
use without the hills and water.


With pump storage, the same water can be used over and over.
The option exists of using natural underground water reservoirs .
Ie, letting water run down a borehole to generate power.