Another thick shroud of smog has covered cities in North, Central and even East China, forcing the closure of expressways and delaying flights, and compelling Beijing to issue an orange alert, the second-highest level in a four-tier emergency response system, for the week-long heavy air pollution.

Bad weather is surely responsible for the situation, but smog is more common in winter because huge quantities of coal are burned to supply heating in most northern cities. Worse, many residents in rural and suburban areas, where central heating system is not available, still use primitive boilers that emit considerable coal-related pollutants to keep warm in winter.

The need for clean, renewable energy as an alternative to coal is therefore more urgent than ever. Given the technological difficulties in using wind and solar power for heating supply, a more feasible solution lies in the use of electricity, which can be generated by green energy as well as coal. In fact, about 30 percent of electricity in China is provided by clean energy.