China is developing a quota system to assure that distribution grid operators carry a certain amount of electricity generated from wind or other renewable resources, a senior official said Monday.

Shi Lishan, deputy director of the renewable energy department at the National Energy Administration, made the statement at a sub-forum on the Expo Central China 2010, which was scheduled to run from Sept. 26 to Sept. 28.

However, Shi did not reveal the specific proportions under the quota, but added that deciding on the quota was really "a challenging job".

"This might be the most important policy amid China's efforts to promote renewable energy development," he said.

Further, Shi said efforts must be made to solve the technological bottleneck and improve the traditional grid system, which had become a major hurdle dampening the development of renewable energy power.

Renewable energy, such as wind and solar energy, is usually subject to weather changes and cannot produce consistent power supplies, which makes it difficult to smoothly transmit power through the traditional grid that carries only stable thermal power supplies.