Here we go again.
Some key differences, however, stand out this time around. Nuclear power — which some included in the clean energy category along with wind, solar, biofuels and others — is suddenly suspect again, after the near meltdown in Japan; and turmoil through much of the oil-rich Middle East has raised worries about supply in the U.S. and elsewhere.
It was almost predictable that alternative energy stocks would benefit, and their solid gains in the past six weeks underscore the assumption that wind, solar and other energy sources are viable alternatives when fossil fuels reach such precious price levels.
The final difference is that green energy has evolved well beyond source fuels; it's also much more about efficiency and conservation, whether it is consumption, production or recycling. Resource and cost savings in this area can be achieved easier and swifter, and on a smaller scale.
Sustainability these days is very much about technology, which is why we spotlight it during our twice-yearly NBC Universal "Green Is Universal" special reports.
This one, timed as usual to coincide with Earth Day on April 22, looks at both business-to-business and business-to-consumer efforts.
Learn how companies are competing in providing oil purification technologyfor major manufacturers or recycling the rare-earth elements from old consumer electronic products. Others are adapting fiber-optic technology to make 3-D solar panels.
On the consumer side, automakers such as Ford Motor
Some companies are providing their own solutions. Info tech players are developing less energy-hungry servers.
While short-term innovation has yielded a wealth of success and reward, others continue to work hard on the the big-buck, long term solutions — which brings us back to new alternative energy sources.
Much has been made of wind, solar, geothermal and biofuels. All of them still have limitations, whether it's production, distribution or storage. Biofuels, however, may have the best chance of overcoming those hurdles. And, some say, none other than algae may be the big winner.