SHIJIAZHUANG, Dec. 11 (Xinhua) -- As China seeks to curb air pollution and win the battle for blue skies, more Chinese cities have switched from coal to geothermal heating during this year's winter heating season, as part of their efforts to become "smokeless cities."

"My family has replaced coal-fired boiler with geothermal heating this year," said Sun Shujuan, a villager in Xiongxian County, northern China's Hebei Province. "Burning coal was dirty and tiring."

Xiongxian, about 130 kilometers away from Beijing, is part of the Xiongan New Area, another new area of "national significance" established in April 2017 to facilitate the coordinated development of Beijing and the surrounding region.

The county began exploiting its rich geothermal resources, a clean and sustainable energy, in 2009. Now it provides geothermal heating to all its urban areas and is looking to expand in rural households.

"We have provided geothermal heating for about 6,000 households in Xiongxian's 12 villages this year," said Chen Menghui, deputy general manager of Sinopec Green Energy Geothermal Development Co., Ltd.

The company, established in 2006, is a joint venture between Arctic Green Energy Corporation of Iceland and Sinopec Star Co., Ltd., a subsidiary of China Petrochemical Corporation (Sinopec), China's largest geothermal developer.

"Compared with coal-fired boilers, geothermal heating can reduce carbon dioxide emissions by at least half," Chen said. "It is estimated that we can replace over 10,000 tonnes of coal and cut emissions of more than 40,000 tonnes of carbon dioxide this year in Xiongxian."

He added that the cost of geothermal heating is about half that of natural gas heating.

Xiongxian is one of the 10 Chinese cities where Sinopec has helped replace coal with geothermal energy, including cities in Shanxi, Shaanxi and Henan provinces.

The company now provides geothermal heating to an area of around 50 square km, and it aims to increase the area by 100 square km by 2023 and help build a total of 20 "smokeless cities" nationwide.

"Local governments are very willing to cooperate with us given the mounting pressure of environmental protection," Chen said.

China aims to have clean energy replace 74 million tonnes of coal and generate 50 percent of winter heating in northern China by 2019, according to a plan released by Chinese government in 2017.

Rich in resources of geothermal energy, the country now has about 150 square km of geothermal energy heated areas, according to an international forum on geothermal energy held in Shanghai in November.

The areas that have access to geothermal heating or cooling are expected to reach 1,600 square km by 2020, according to a five-year plan for developing geothermal energy released by Chinese government in 2017.