Load Shifting Potential
Scottish Water provided a series of data on the WWTW site including the plants’ energy consumption which will be considered here to assess the potential for load shifting. Fig.1 plots the hourly energy consumption of the WWTW site for the first week of January. Although the resolution of the data is only one hour it shows a general trend of lower energy consumption at night and increased consumption during the day, and highlights what this concept is trying to achieve, that is, moving the areas shown in the red boxes to times when there is no renewable generation, or to peak times to help balance the grid and reduce energy costs.
WWTW case study site hourly energy consumption for the first week of January with periods of low energy consumption shown within red boxes.
Although this day and night pattern isn’t always as clear as in Fig.1, with the energy consumption of the first week of April, July and October (see Data Sources), if an average value for each hour of the day across the year is plotted, a clear pattern similar to Fig.1 emerges, as shown in Fig.2. This shows the potential for load shifting. Assuming these peaks in energy consumption are from an increase in wastewater flow, this method looks to store wastewater to then process at a time of increased renewable generation and move the peaks in energy consumption to a time of the operators choosing.
WWTW case study site averaged hourly energy consumption.
A similar plot can be made for each of the four seasons of the year as shown in Fig.3. There is a noticeably higher energy consumption during the autumn months of October to December due to storm water, with these three months having the highest precipitation in this region of Scotland. (4) From Fig.3 the potential for load shifting is again evident, particularly out with these autumn months when the plant operates with a lower energy consumption, having been designed to meet increased demand during wet weather periods. (5) The treatment works could significantly increase its power demand to match renewable generation during the drier months by storing the wastewater to process at a desired time.
WWTW case study site averaged hourly energy consumption.