The displaced dispatchable generation could be coal, natural gas, biomass, nuclear, geothermal or storage hydro. Rather than starting and stopping nuclear or geothermal, it is cheaper to use them as constant power. Any power generated in excess of demand can displace heating fuels, be converted to storage or sold to another grid. Biofuels and conventional hydro can be saved. Variable renewable energy (VRE) or intermittent renewable energy sources (IRES) are renewable energy sources that are not dispatchable due to their fluctuating nature, such as wind power and solar power, as opposed to controllable renewable energy sources, such as dammed hydroelectricity or bioenergy, or. The penetration of intermittent renewables in most power grids is low: global electricity generation in 2021 was 7% wind and 4% solar. However, in 2021 Denmark, Luxembourg and Uruguay generated over 40% of their electricity. Penetration refers to the proportion of a (PE) source in an electric power system, expressed as a percentage. There are several methods of calculation yielding different penetrations. The penetration can be calculated either as: • • • • • Dammed hydroelectricity, biomass and geothermal are dispatchable as each has a store of potential energy; wind and solar without storage can be decreased (curtailed) but are not. The displaced dispatchable generation could be coal, natural gas, biomass, nuclear, geothermal or storage hydro. Rather than starting and stopping nuclear or geothermal, it is. Great BritainThe operator of the British electricity system has said that it will be capable of operating by 2025, whenever there is enough renewable. • Sivaram, Varun (2018). Taming the Sun: Innovation to Harness Solar Energy and Power the Planet. Cambridge, MA: MIT Press.
