Increasing Onsite Energy Production at NapaSan
NapaSan is always working to maximize resource recovery as part of the wastewater treatment process. In addition to water recycling and biosolids reuse, NapaSan is continually striving to produce as much green energy as possible at their facility. The biogas produced from the solid materials that come into the facility coupled with fats, oils, and grease from restaurants is used to generate about 40% of the electricity used at their facility. The 1-megawatt solar power array at the treatment plant produces another 10% of the energy needed to power the treatment process, which means an average of 50% of NapaSan’s electricity needs are met by onsite energy production.

Last year, NapaSan signed an energy services agreement with DG Linear West I, LLC a NextEra Energy company. The agreement included construction and installation of a new Mainspring Linear Generator. The linear generator was installed at the end of December and will be operable in the spring of 2024. The linear generator will run on biogas produced in the digester and provide additional renewable energy to power the plant while also reducing greenhouse gas emissions.

The linear generator is a new, efficient, fuel-flexible power generation technology that converts a variety of clean fuels, including wastewater treatment plant biogas, into clean and reliable electricity. NapaSan will be the first-ever wastewater treatment facility to run a linear generator using biogas (methane) produced in an anaerobic digester.  With the linear generator, the solar array, and the electricity produced from biogas, roughly 75% of the energy needed to power NapaSan’s operations will be produced onsite.

NapaSan is also planning to lease a portion of its pond surface for the installation a 20-megawatt floating solar array that would be located on two of the treatment ponds at the facility.  This project will generate additional green energy that will be transmitted to the power utility grid. In addition to the lease revenue, the solar array will shade the pond thereby helping to decrease algae growth and reduce evaporation, which will improve water quality and reduce chemical use in the treatment process.  Construction is expected to begin in 2025 and be completed in 2026.

These projects are all part of NapaSan’s mission to protect public health and the environment through sustainable wastewater management practices. These efforts will help NapaSan reduce greenhouse gas emissions and maximize the amount of renewable energy produced at the facility.