Hundreds of protesters have marched on Aberthaw power station, calling for its closure, and more investment in green jobs.
They say closing the station could reduce deaths from air pollution and "end the suffering of communities living near to opencast coal mines in Wales."
They argue that inefficient power stations are not needed, and that Wales should be moving towards renewable energy, with projects such as the Swansea Bay lagoon.
Owners of the station, RWE, say they are investing £5m in technology that will 'significantly lower' the station's emissions, and the Welsh Government have reiterated their commitment to renewable energy.
We are committed to using energy more efficiently in Wales by moving from our traditional association with fossil fuels to a nation renowned for its clean energy. The Environment Secretary recently set out her priorities for energy in Wales. This included plans to support energy intensive industries to become more efficient and support proposals to phase out the use of unabated coal fired power and limit opportunities for new coal development.