because burning coal is a major contributor to climate change. but big coal users china and the us are not on the list. today s talks at cop26 are all about clean energy. we can join bbc wales economics correspondent sarah dickins, who is in the welsh valleys at the biggest onshore wind farm anywhere in england and wales. that s right, this is pen y cymoedd, it s where those industrial valleys known around the world for producing coalin known around the world for producing coal in the past, now have this massive wind farm called pen y cymoedd, and it s actually run by a swedish state owned company called vattenfall and the ground is owned by the welsh government. there are 76 turbines here, and let s look at how big they are. right across the landscape, they are over 100 metres high, turning every day as the wind flows. but what is interesting is