Dave Elliott: In its latest “energy outlook” report, Bloomberg New Energy Finance says wind and solar photovoltaics (PV) will supply almost 50% of global electricity by 2050. Wind, it projects, will produce 26% and solar 22%, with renewables overall supplying 62% of the total. That’s despite electricity demand by 2050 increasing 62%, resulting in global generating capacity almost tripling. Nuclear will then be at 7% and fossil at 31%, according to this outlook, so renewables will clearly have won — although emissions from the fossil sector will still rise. IRENA, the International Renewable Energy Agency, is more optimistic. In a new report it says renewables and energy efficiency, boosted by electrification, could provide 90% of the necessary reductions in energy-related carbon emissions to limit the global rise in temperature to well below 2°C by 2050. Renewables can supply 86% of global power, and with electrification, they would provide 75% of the emission reductions needed. It sees electrification as a vital part of all this, especially since it can help balance variable renewables: “Clean electricity will be the principal source of power, combined with ‘smart’ digital technologies that make it possible to take full advantage of the growing amounts of low-cost renewable power”. The emphasis on electrification, and balancing via power grid-linked systems, is understandable. In IRENA’s vision, there will be a lot of green power available, much of it variable, and some of the balancing options are electricity based — supergrid power imports and exports, for example. But not all of them are. Apart from batteries, in which electricity creates chemical charge for short-term storage, and pumped storage, using power to create potential energy by pumping water uphill to a hydro reservoir, most longer-term storage systems rely on converting electricity to more easily stored heat or gas. It could be that heat and/or green hydrogen storage will become significant options for balancing — hydrogen via huge underground cavern stores and heat via giant hot water or hot rock stores. Some pilot projects are underway for heat storage, for example in Germany, looking ultimately to GWh-scale systems, and also for hydrogen, with a P2G-linked underground storage system in the UK.
Physics World 21st Aug 2019 read more »