Towards a Realistic Performance Analysis of Storage Systems in Smart Grids

Energy storage devices (ESDs) such as lithium-ion batteries and flywheels have the potential to revolutionize the electricity grid by allowing the smoothing of variable-energy generator output, and the time-shifting of demand away from peak times. Numerous recent investigations have studied the impact of ESDs on energy systems, but usually by assuming ideal ESD behaviour, such as infinite ESD charging and discharging rates, and zero self-discharge. However, real-life ESDs are far from ideal. We investigate the effect of non-ideal ESD behaviour on system performance, presenting an analytical ESD model that retains much of the simplicity of an ideal ESD, yet captures many (though not all) non-ideal behaviours. This allows us to compute performance bounds for systems using non-ideal ESDs using standard teletraffic techniques. We provide performance results for five widely used ESD technologies and show that our models can closely approximate numerically computed performance bounds.