Wind farms (i.e. local assemblies of wind turbines) for power generation can only provide negligible useful electricity to grid supply systems. Because they provide intermittent only power, they merely displace thermal power stations onto standby mode while the thermal power stations wait for the wind to change. Wind farms make no significant reduction to pollution because thermal power stations continue using their fuel and producing their emissions while operating in standby mode. The large scale use of wind farms requires upgrading of an electricity grid, more complex grid management, and operation of additional thermal power stations to protect against power cuts in time of supply failure. These effects increase the cost of electricity supplied by the grid in addition to the capital, maintenance and operating costs of the wind farms themselves. Also, wind farms cause significant environmental damage. These severe environmental costs may be worth suffering if wind farms actually provided cheap, clean, useful electricity. They do not.