Energy storage1 is completely uneconomic for the amounts of energy required. So we must use back-up generation. Constantly, instantly available back-up must be provided by reliable energy sources (to provide power whenever the wind speed drops). Coal, gas, hydro and nuclear power provide reliable power, but not all are suitable as back up generators for wind power. Back-up generation is mostly provided by gas turbines in Australia. The reasons why gas provides the back-up rather than one of the other energy sources are: 1. We have insufficient hydro resources to provide peak power let alone provide back-up for wind power. Hydro energy has high value for providing peak power and for providing rapid and controllable responses to changes in electricity demand across the network. So our very limited hydro resource is used to generate this high value power. 2. Coal generates the lowest cost electricity and, therefore, coal generation is the last to be displaced when a new source of electricity becomes available (such as when the wind blows). That is, when wind energy is available it displaces the highest cost generator first. Coal is displaced last. 3. Coal generators cannot follow load changes rapidly. Brown coal power stations (as used in Victoria) are designed to run at full power all the time. They can only reduce power by venting steam, but they continue to burn the same amount of coal and hence produce the same amount of emissions whether or not they are generating electricity. Black coal power stations have some limited capability to follow the load but cannot follow the rapid changes in wind power. 4. Gas turbines can follow load changes fairly well but not as rapidly as the wind power changes. Gas turbines power up and down like a turbo-prop aircraft engine, but with slower response. Next to hydro, gas turbines are best able to follow the load changes created by wind power…

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