A worker inspects solar panels at a solar Dunhuang, 950km (590 miles) northwest of Lanzhou, Gansu Province September 16, 2013. China is pumping investment into wind power, which is more cost-competitive than solar energy and partly able to compete with coal and gas. China is the world's biggest producer of CO2 emissions, but is also the world's leading generator of renewable electricity. Environmental issues will be under the spotlight during a working group of the Intergovernmental Panel on Climate Change, which will meet in Stockholm from September 23-26. REUTERS/Carlos Barria (CHINA - Tags: ENERGY BUSINESS ENVIRONMENT) - RTX13UEF