OPTIMIZATION OF ENERGY STORAGE SYSTEMS AND DEMAND SIDE MANAGEMENT TO MAXIMIZE WATER UTILITY SAVINGS: A HAWAII CASE STUDY

Energy conservation is a concern in many commercial industries, and consequently facility operators are turning to various efficiency and alternative measures to reduce electricity costs. Growing use of intermittent resources, energy storage systems (ESSs) and demand side management (DSM) options are also gaining interest to maximize potential energy savings. Here we study the potential of ESSs versus DSM for water utilities through a case study of the National Energy Laboratory of the Hawaii Authority (NELHA). NELHA is a multizone water utility, where most electricity is dedicated to pumping water. In this study the optimization of the NELHA's overall electricity charges, using both ESSs or DSM via pump load shifting and optimization of pump house output is investigated. Optimization is performed to determine the optimal size of the batteries considering the water demand and energy costs in each zone. An extended approach of considering the characteristics of individual pumps on each pump house in the optimization model is applied to provide insight to the proper optimization framework for selecting individual pumps depending on the current zonal load, given pump efficiencies and maximum flow rates from each pump. The outcome from mathematical models using general quadratic pump efficiency functions and a simplified linear version of pump efficiency is compared to determine the significance of this difference in modeling methodology. Additionally, the effect of increasing solar power on electricity purchased is analyzed. This work will help to establish the role of ESS and DSM in energy savings for water utility industry.