Showing posts with label solar cells. Show all posts
Showing posts with label solar cells. Show all posts

18 February 2009

Will need of Rare Earth Metals for Green Energy Encourage Asteroid Mining?

I'm sure many readers will be surprised initially, like I was, that most of our sources of rare Earth metals come from Astroblemes, or asteroid craters. Otherwise, these heavy metals would have migrated to Earths core early in its development. The article below highlights the need for such metals in the new energy economy, which are abundant in Near Earth Asteroids (NEAs), and perhaps on the Moon (per Dennis Wingo's MoonRush).

"Why Sustainable Power is Unsustainable"
New Scientist

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

According to Moon Rush, even the smaller of the Iron-Nickel NEAs contains more
metals than all that has ever been mined in all of history
. Further, our Moon, riddled with craters from such collisions is likely to be rich in such resources, as well. A single ‘‘Diablo Canyon’’ size impactor would have left between 450 million to 1.77 billion tons
of economically recoverable nickel, iron, cobalt, &=platinum group metals materials, worth around $20 trillion.
Besides Moon Rush, Check out Mining the Sky, High Frontier (O'Neill), and this terrific online source: