At AEI, I take a pride in disclosing to the public, the most comprehensive list of globally-listed alternative energy stocks - it continues to grow at quite a rate.

I do however, have a few rules;

- no pink sheet or OTC stocks e.g. ZAP
- no stocks with an alternative energy exposure of less than approximately 25% to alternative energy in sales e.g. General Electric - don't believe the ecomagination hype, alternative energy is still well under 10% of their sales but has obviously great potential to grow faster than the rest of the business
- no energy efficiency stocks (because all energy efficiency ultimately leads to increased energy consumption due to the rebound effect to the M3 part of the money supply)

I'm always playing catchup however to the alternative energy universe. Apart from my own media scanning, I always welcome an email telling me of a stock I may not know about which should be included - so let me know if there any that should be included. In that vein, here are 4 new stocks - all geothermal and in Australia - that I have just added; Geothermal Resources, GreenRock Energy, Petratherm and Torrens Energy.

This image I have taken from here and sums up perfectly Australia's geothermal potential. Australian geothermal stocks are doing well because the leader of the opposition party Kevin Rudd, who has a strong chance of winning the next election, prefers geothermal development to nuclear power. And by the way, see this useful wiki on geothermal power, although it is a bit US-centric.

The bottom line is that if you can dig deep enough, you will always get a high enough temperatures to boil water, turn it into steam and power a turbine. At the centre of the earth, temperature reaches a staggering 223,000 degrees centigrade. But we will probably never manage to drill that far. In other words, it helps if you live in Iceland which is basically volcanic, just below the surface.