Much of the growth in renewables can be attributed to rapidly falling costs. For example, the cost of solar photovoltaic energy fell by 85 per cent between 2010 and 2020. Solar and wind are now routinely cheaper than fossil fuels such as coal.15 This has occurred despite the ongoing government subsidies of fossil fuels, which may become indefensible as battery technology improves and undermines the argument that fossil fuel-based generating capacity is necessary for when there is no wind or sunshine. A number of promising developments in materials science offer hope of increased efficiency for photovoltaics.16
There has been considerable disagreement about the role that can be played by hydrogen.17 In theory, hydrogen produced by renewable energy (“green hydrogen”) is entirely renewable, as the only waste product from burning hydrogen is water. In practice, the high demand for renewable electricity means that there tends to be little left over for hydrogen production. As a result, hydrogen may have a relatively limited role to play as a renewable energy fuel. This will largely be as “blue hydrogen”, generated as a by-product of fossil fuel combustion. Though it will not be a zero-carbon fuel until carbon capture can be achieved at commercial scales, blue hydrogen could nonetheless help mitigate “hard-to-abate” emissions such as those from shipping. Related “Power to X” technologies, such as synthetic fuels made using renewable electricity, are promising, but currently face efficiency challenges.
In the longer term, nuclear fission and fusion may also have a role to play. Recent developments suggest the goal of artificial fusion with a net output of energy is closer than ever. Nevertheless, commercial-scale fusion plants are still likely to be decades away.18 Small-scale nuclear fission reactors are also under development, although their chances of commercial success remain similarly difficult to predict.19
