Net zero emissions and low-carbon alternatives

Energy systems must achieve net zero emissions of carbon dioxide if they are to stop putting pressure on the climate, and this chapter begins with the climate science behind this requirement. Alternative energy end-use and supply technologies that could contribute to this outcome are surveyed. The core of such systems is increasingly clear with recent advances in solar PV, wind turbines and batteries. At their core would be electricity systems with zero or negative emission and substantial generation shares from renewable resources, along with widespread electrification of economic activities. This core is now seen as relatively 'easy to decarbonize'. But other activities, especially in heavy industry and commercial transport, appear 'hard to decarbonize', needing low-carbon fuels such as hydrogen or carbon dioxide removal technologies. While two decades ago most energy emissions then appeared hard to decarbonize, advancing low-carbon alternatives supported by innovation and industrial policies are expanding opportunities for change.