Figure 1 shows the current step in the evaluation methodology…

Figure 1 Showing the current step in the methodology for evaluating a facility level energy storage deployment.

If the selected electrical energy storage devices (LightSail RAES V1 or the Prudent VRB-ESS® ) were to be deployed without onsite renewable energy generation, in this scenario, the device would only be used for the purpose of Demand Charge Management. In an optimal deployment, the facility would have a method of predicting the peak power consumption for each day. In this situation the energy storage device would be fully discharged in order to lower the peak power consumption for the day. The goal of this deployment would be lowering the highest peak for the month and reducing demand charge payments. Predicting the peak power can be done through reviewing historical load profile records, forecasting the weather to understand HVAC loads, managing/scheduling power consumption events, etc.(Baxter, 2012). For this first pass evaluation, only load profile records will be used.

Figure 2 shows the load profile for the facility on the peak power consumption day of the year at the facility. The dashed line in Figure 2 represents the new reduced peak that would be realized if either the LightSailRAES V1 or the Prudent VRB-ESS® were deployed. Conveniently, both devices have the same power and energy rating, 250 kW and 1000 kWh (depending on the amount of storage media) respectively. The equation for the new reduced peak at full power is:

Figure 2 showing the Load profile on peak usage day at the facility. The dashed line represents the peak that would be realized if the energy storage device were operated at full power.

Using a 250 kW energy storage device to reduce the 1,583 kW demand peak to a new shifted peak of 1,333 kW would require 1123 kWh of energy output from the device. In Figure 2 the area above the dashed line and below the power usage curve represents the energy produced by the energy storage device. As both devices are rated at 1 MWh, the power output of the device must be reduced from the maximum rated output to a level that meets the 1MWh energy limit of the device. MS Excel Goal Seek optimization can be used to determine that a new shifted peak of 1,346 kW achieved by reducing the 1,583 kW demand peak by 236 kW (instead of 250 kW) will accommodate the storage device’s 1 MWh energy limit.

Repeating this goal seek optimization for every day of available power/energy data will reveal the new reduced peaks in each month. The monthly power reduction resulting from energy storage is calculated using the following equation: