Energy Reports (Dec 2023)
The need for energy storage on renewable energy generator outputs to lessen the Geeth effect, i.e. short-term variations mainly associated with wind turbine active power output
Abstract
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 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 operator as they seek to deliver a stable electricity grid. Calculated coefficient of variation values include 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). Energy storage methods are recommended to minimise the Geeth Effect. Recommendations include the installation of (i) filters (supercapacitors) and (ii) battery energy storage systems, both systems connected to the output stage of the wind turbine generators. Supercapacitors are the preferred choice for wind turbines because of the continuous charge/discharge cycling events, which can be detrimental to battery energy systems. Low coefficient of variation values are desirable and high values undesirable.
