Energy Storage Solutions for Renewable Energy Generators

Many studies investigating the short-term variations associated with the power output from wind turbine generators utilise simulated or modelled data in the analysis. This current study uses short-term empirical data downloaded directly from operational onshore wind turbines via electrical power quality meters. The empirical data shows that the short-term variations (one-second or sub-one-second timeframe) occur continuously over most of the power output range. A novel name is proposed, the Geeth Effect, for this variability phenomenon. The Geeth Effect is measured using the coefficient of variation mathematical expression and is likely contributing to (i) lower-than-expected financial and environmental benefits associated with the vast increase in connected wind turbine capacity, (ii) significant challenges faced by the transmission system operators as they seek to deliver a stable electricity grid. Calculated coefficient of variation values includes 64% (10-kW wind turbine), 46% (300-kW wind turbine), 30% (3-MW wind turbine), 1.4% (169-kW solar PV), and 3.2% (40-kW hydroelectric plant). Cloudy conditions affect the coefficient of variation values of PV systems. The main energy storage/stability methods discussed in this chapter recommended to minimise the Geeth Effect are (i) filters (supercapacitors), (ii) battery energy storage systems, both systems connected to the output stage of the wind turbine generators, and (iii) synchronous compensator. Supercapacitors have the advantage of being better suited to continuous charge/discharge cycling events, which can be detrimental to battery energy systems. A low coefficient of variation values is desirable and high values undesirable.