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.
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.
Assistant General Manager