With the increased concern about climate change, the interest in renewable energy generation and electric transport is continually increasing. Integrating the electricity grid, renewable energy, and transport systems is the way forward to reduce carbon emissions, improve the environment and provide sustainable energy and transport systems. Battery technology plays a key role in this integration. This lecture talk will give an overview of the challenges facing electricity grids due to the increased deployment of renewable energy sources and electric vehicles. It will also cover opportunities that battery energy storage systems provide not only to meet these challenges but also to foster new operational models that will help maintain reliable and affordable electricity and transport systems as well as improve their efficiency and lower their environmental impacts.