•Decarbonisation of the energy system is fundamental to combating climate change. There are different pathways to a decarbonised energy system including efficiency, nuclear energy, carbon capture and renewable energy. Renewable energy harnessed through the electricity system and the electrification of large parts of the economy (e.g. transport and heat) is recognized as technologically and economically a very likely pathway. 

•It is gaining traction with e.g. widespread electrification of transport and rapid deployment of variable renewable energy sources on electricity systems. It is likely that different pathways will evolve in different regions, but renewables will globally be a part of the solution. It is important to understand the technological and economic challenges of integrating renewables into the electricity system. 

•This will help in identifying what is known and is implemented, what is known but requires implementation through e.g. education, and what is unknown and requires research and innovation ranging from technology development to business models to analysis. Finally, it can indicate from a decarbonization objective what is best done using another approach e.g. a portfolio of renewables and nuclear. 

•The challenges are not only engineering and economic which are the focus here but include broader social science challenges including public acceptance of infrastructure and adoption of technological solutions.