Workers check solar panels at a photovoltaic power station in Ningxia Hui Autonomous Region on Dec. 28. The Hongsipu photovoltaic power station, the region's biggest with an annual capacity of 50 megawatts, was put into operation the same day. With a total investment of 1.19 billion yuan (US$189 million), the project has yielded 20.12 million kilowatt-hours of power since its connection to the state grid. [Photo: Xinhua]