Disaggregation of energy storage operation by timescales

We discuss the ex-post disaggregation of electric storage operation by time differences between charging and discharging, i.e. by how long energy is stored prior to the discharge. This adds a new dimension to the analysis of storage time shifting revenue and allows for additional insights into the historic value loss of storage assets. We apply this method to stylized pumped hydro and battery storage systems operating on historic European (Swiss and German/Austrian) day-ahead electricity price curves (2007-2017). We find that historic trends of the disaggregated revenue are highly diverse depending on the timescales. Changes in relative revenue shares are primarily driven by the price profile distortion due to increasing photovoltaic electricity generation. In the battery storage case this results in a 1.5 h reduction of charging-discharging time differences between 2008 and 2012. The case of pumped hydro storage plants is more complex: Main revenue losses occur for time differences of 6 to 12 h. Revenues on other timescales are much more stable or even increasing. This especially holds for short transfer times between 0 and 6 h: In the German/Austrian market area, they contribute 17% to total pumped hydro storage revenue in 2016, as compared to 3% in 2008. The disaggregation also enables the analysis of contributions from hours with outlier electricity prices. These are found to be especially significant in the years 2007 and 2008. Overall, we find that storage operation has been increasingly diversified due to the historic price profile evolution. The often discussed revenue erosion offers new opportunities on different timescales.