John Stumbles wrote:
On Mon, 28 Mar 2011 16:57:29 +0100, The Natural Philosopher wrote:

No, you don't. You need a 10 year stockpile of uranium.

I think the problem is that with current technology there isn't enough
uranium to generate anything like the amounts of power we need in non-
breeder Uranium-cycle reactors[1]. Fast breeders could get close to a
useful sustainable energy output[2] but are still relatively unproven and
expensive. Thorium looks promising (to the Chinese, who are not known for
soft-headedness in economic matters) but is still pretty speculative
technology.

I part agree. Therer almost certainly is enough uranium, and we have a
lot of plutonium, not exactly lying about, but 'avaialable'

Ironically what both (current technology) nuclear and wind (and many
other renewables such as PV, wave and tide) have in common, when used for
electricity generation, is that they really need some form of storage, or
quick-response (and inevitably fossil-fuelled) fill-in generation
capacity. However as oil gets more expensive we may find ourselves using
electricity for oil-replacement technology such as hydrogen where storage
over a period of weeks is much more feasible, and obviously renewables
such as wind would be a good match for that.

I really don't see large scale gas storage as being feasible. the energy
density is too low. Liquids are a bit better, but we don't have much
storage capacity for that either. Wheras coal can be piled up and we
dont need so very much uranium. After all each reactor carries a year of
fuel rods inside it anyway.

Whilst the ideal major source of non-fossil energy is perhaps something
like Thorium which would seem to avoid the problems of restricted supply,
horrendous long-term (circa million years) radioactive waste management
and proliferation potential, that's going to take realistically at least
a couple of decades to develop and roll out[3]. In the meantime we *can*
with today's technology generate useful amounts of non-fossil energy from
renewables.

No we cant. Or rather, if we try, it will be less and less effective at
reducing fossil fuel.

renewale can only work in symbiosis with hydro - which we don't have
enough of - or fossil fuel. By themselves they are useless.

For every wind farm, you also need a conventional power station.
Because nuclear can't dispatch properly, that means your a stuck with
fossil fuel if you go with renewables. It weds you completely to fossil.



[1] According to Prof David Mackay in his 'Sustainable Energy - Without
The Hot Air' we can't sustainably fuel our existing installed base of
once-through Uranium fission reactors with existing land-based sources of
Uranium:
http://www.inference.phy.cam.ac.uk/w...page_162.shtml


As I read it, that depends entirely on what you consider the reserves to
be. Since uranium is barely worth mining at the moment no one is
actively looking. So nop one actually knows. IIRC he als says 'abou 7450
years supply' in there somewhere.




[2] 33kWh per day per person according to MacKay, which would almost do
for our current space heating and cooling consumption:
http://www.inference.phy.cam.ac.uk/w...page_103.shtml


That's total energy, not electrical. at an average of about 30GW we
consume about 500W per head of electricity..so 12Kwh per day.


[3] or, longer term, obviously, fusion

Or something as yet undreamed of.