Complex sentence: The growth of output from wind turbines on Shetland has increased instability in the local grid (which is not connected to the national grid on mainland Scotland) and SSE have installed a 1 MW sodium-sulphur battery in a nearby building to ameliorate the peak loads.
Split into simpler sentences: The growth of output from wind turbines on Shetland has increased instability in the local grid (which is not connected to the national grid on mainland Scotland). SSE installed a 1 MW sodium-sulphur battery in a nearby building to ameliorate the peak loads.