FYI,

"Why Sustainable Power is Unsustainable"
New Scientist
http://www.newscientist.com/article/dn16550-why-sustainable-power-is-
unsustainable.html

: Renewable energy needs to become a lot more renewable – a theme
: that emerged at the Financial Times Energy Conference in London
: this week.

: Supratik Guha of IBM told the conference that sales of silicon
: solar cells are booming, with 2008 being the first year that the
: silicon wafers for solar cells outstripped those used for
: microelectronic devices.

: But although silicon is the most abundant element in the Earth's
: crust after oxygen, it makes relatively inefficient cells that
: struggle to compete with electricity generated from fossil fuels.
: And the most advanced solar-cell technologies rely on much rarer
: materials than silicon.

: Rare metal

: The efficiency of solar cells is measured as a percentage of light
: energy they convert to electricity. Silicon solar cells finally
: reached 25% in late December. But multi-junction solar cells can
: achieve efficiencies greater than 40%.

: Although touted as the future of solar power, those and most other
: multiple-junction cells owe their performance to the rare metal
: indium, which is far from abundant. There are fewer than
: 10 indium-containing minerals, and none present in significant
: deposits – in total the metal accounts for a paltry 0.25 parts per
: million of the Earth's crust.

: Most of the rare and expensive element is used to manufacture LCD
: screens, an industry that has driven indium prices to $1000 per
: kilogram in recent years. Estimates that did not factor in an
: explosion in indium-containing solar panels reckon we have only a
: 10 year supply of it left.

: If power from the Sun is to become a major source of electricity,
: solar panels would have to cover huge areas, making an alternative
: to indium essential.

: Precious platinum

: The dream of the hydrogen economy faces similar challenges, said
: Paul Adcock of UK firm Intelligent Energy.

: A cheap way to generate hydrogen has so far proved elusive. New
: approaches, such as using bacterial enzymes to "split" water, have
: a long way to go before they are commercially viable.

: So far, fuel cells are still the most effective way to turn the gas
: into electricity. But these mostly rely on expensive platinum to
: catalyse the reaction.

: The trouble is, platinum makes indium appear super-abundant. It is
: present in the Earth's crust at just 0.003 parts per billion and is
: priced in $ per gram, not per kilogram. Estimates say that, if the
: 500 million vehicles in use today were fitted with fuel cells, all
: the world's platinum would be exhausted within 15 years.

: Unfortunately platinum-free fuel cells are still a long way from
: the test track. A nickel-catalysed fuel cell developed at Wuhan
: University, China, has a maximum output only around 10% of that a
: platinum catalyst can offer.

: A new approach announced yesterday demonstrates that carbon
: nanotubes could be more effective, as well as cheaper, than
: platinum. But again it will be many years before platinum-free fuel
: cells become a commercial prospect.

: Renewable energy technologies remain the great hope for the future,
: and are guaranteed research funds in the short term. But unless a
: second generation of sustainable energy ideas based on truly
: sustainable resources is established, the renewable light could be
: in danger of dimming.

Mark Reiff