Fountain Valley, CA
4.95 MW / 32.56 MWh
Wastewater Treatment Plant
Energy Storage, Utility Bill Optimization, Demand Response
The Orange County Sanitation District (OC San) is a public agency that provides wastewater collection, treatment, and disposal services for approximately 2.6 million people in central and northwest Orange County from two operating facilities that treat wastewater from residential, commercial, and industrial sources.
When OC San initially laid out the battery system at its Fountain Valley plant, the goal was to minimize the facility’s import of energy. The OC San team looked at how long of a time window was needed at peak tariff time versus the delta with which they could produce energy for two engines at the plant. They compared that to their everyday energy use which set the energy storage system size at about 5MW / 32MWh. During this process, they determined that it was a viable project through the Southern California Edison (SCE)’s Local Capacity Requirements (LCR) Incentive Program.
OC San’s energy storage system (ESS) was the largest behind-the-meter system installed in North America at the time of installation in August 2019. In June 2020, Stem started operating OC San’s energy storage system through the 345MWh portfolio awarded by Electrodes LLC for a 10-year period. Ever since, Stem has seamlessly coordinated trouble-free operations between OC San and the utility using Stem’s Athena® smart energy storage software.
Tasked with converting 185 million gallons of wastewater everyday into 100 million gallons of drinking water and valuable resources for organic reuse, OC San must be online 24/7/365. Since the county’s flow of water never stops, OC San’s operations must be constant.
When OC San turned to energy storage as a great opportunity to improve the facilities’ resilience and operations, the most critical obstacles were determining the revised SCE interconnection requirements. Since the plant generation capacity increased and required additional monitoring and metering information for the site, they needed an AI-driven solution to monitor OC San’s varying load conditions and cogeneration operating conditions to quickly control the ESS to maximize demand savings while meeting the utility’s demand needs.
Stem’s role at OC San is to make sure the ESS operates in a way that minimizes the overall input of electricity to the plant facilities. Stem manages OC San’s internal loads to match what’s available and what’s needed to deliver wastewater services to their 2.6 million customers.
Currently, the ESS operation is dispatched by SCE through the LCR Program. The ESS, utilizing Stem’s Athena smart energy software, controls the charging of the batteries to minimize the peak monthly demand on the power grid. In the future, if the demand response restrictions change, the battery storage system will be used to intelligently manage the plant’s peak power demand during peak power times.
Stem’s Athena software helps enable four value streams for OC San. First, OC San is receiving revenue by allowing the ESS owners to use the available plant demand. Second, the ESS is achieving energy savings and utility bill optimization with Stem by charging the batteries during lower energy costs and discharging at peak energy costs. Third, the ESS discharges when a momentary peak demand exceeds the average monthly peak during an unexpected cogeneration system shutdown. And lastly, in 2019, OC San received California’s Self-Generation Incentive Program (SGIP) funding.
OC San is able to leverage the benefit of the ESS to offset peak demand at Plant 1 and push digester gas from Plant 1 to Plant 2 to achieve near zero power import at Plant 2. This makes each plant more resilient and able to supply the power needs of each facility. Plus, OC San’s customers benefit from more reliable service. During a Power Flex Alert, the combination of the ESS and OC San load reduction allows Plant 1 to achieve a near zero power import during most of the peak power times to help the utility grid.