This Scottish scientist produced a spreadsheet model of an electricity generating system composed primarily of wind turbines backed up with pumped-storage hydro-electricity schemes. Such modelling can predict how much wind power and pumped-storage energy capacity should be installed for satisfactory renewables-only generation. Please Register or Log in to view the hidden image! Click to view a larger image https://scottishscientist.files.wordpress.com/2015/04/windpumpedstorage_june.jpg The spreadsheet line graph above plots power & energy variables for the time-line modelled – curves for power exported, demanded, from wind, for pumping, from the hydro-turbine & a curve for the energy stored by water pumped into the upper reservoir. The time-line graphs data for the grid in Scotland, normalised in proportion to wind power and demand data for June 2014, as downloaded from the Gridwatch Database of the U.K. National Grid Status Website. Modelling assumptions for this graph – the peak demand in Scotland in 2014 was 6GW an installed maximum wind turbine power in Scotland of 33GW = 5.5 x peak demand an installed pumped-storage hydro energy capacity in Scotland of 160GWh = 1.11 peak-demand-days the pumps have a maximum power consumption of 6GW = peak demand the hydro-turbines have a maximum power output of 6GW = peak demand the pumps and the hydro-turbines both have an efficiency of 88% no other power stations are generating power. I conclude that such models will help to take the guesswork and uncertainty out of renewable-energy electricity system design! Please Register or Log in to view the hidden image! Click to view a larger image https://scottishscientist.files.wordpress.com/2015/04/windpumpedstorage_january_b1.jpg A real electricity system which had adopted wind power and pumped-storage hydro for future electricity generation would inherit existing power stations which could continue to serve on stand-by as a further back-up, reserve or emergency power supply.