The renewables boom, spurred by about $66 billion of subsidies last year, intensified competition between wind- turbine and solar-panel manufacturers, gutting margins from the biggest producers led by Vestas Wind Systems A/S and First Solar Inc. The 95-member WilderHill New Energy Index of renewable- energy stocks has tumbled 40 percent this year, steeper than the 14 percent drop in the MSCI World Index.

The zeal to replace fossil fuels, which take millions of years to form from dead organic matter, belies the failed efforts at the UN talks to broker a deal that would limit carbon dioxide emissions from coal and oil blamed for global warming. Without a deal, existing pollution caps under the 1997 Kyoto Protocol expire next year.

Debate in South Africa's third-largest city will include how to establish a fund that would channel an unspecified portion of $100 billion a year in climate aid pledged by rich nations to developing countries by 2020. Monitoring and verifying emissions cuts made by all nations are also on the agenda, as well as making a mechanism for transferring CO2- reducing technology between states. Discussions on those issues may be eclipsed by talks on the future of Kyoto.

Eoin Treacy's view Renewable energy makes a number of headlines but sound economics is not one of them. The industry depends heavily on government subsidy, regulation and support for viability. It is impossible to know how technologies such as solar and wind might develop but it is questionable whether they can deliver the abundant cheap energy the global economy craves.

The Powershares Clean Energy ETF continues to deteriorate. It broke below the 2009 low in September and remains in a consistent downtrend. A sustained move above $6.50 would be required to begin to question downside potential.