Disaster Response and Mutual Aid

Healdsburg, Calif., to cut ribbon on 3-MW floating solar project

On Feb. 24, the City of Healdsburg plans a virtual ribbon cutting for a 3-megawatt (MW) floating solar project on ponds that hold recycled water at the California city’s wastewater treatment plant.

The solar project, which has been providing power for the city since December, includes about 11,600 solar panels that can generate 6.5 million kilowatt hours (kWh) a year, enough to supply about 8 percent of Healdsburg’s annual energy needs. With the project’s 3.0 MW (ac) rating equivalent to 4.78 MW (dc), the Healdsburg installation is the largest floating solar project in the nation.

Healdsburg, like other municipalities in California, is working toward meeting statewide targets to derive 60% of their energy from renewable sources by 2030. Currently, Healdsburg is at about 40% renewables.

The project, which was arranged in coordination with the Northern California Power Agency (NCPA), was developed, financed and built by White Pine Renewables.

Healdsburg will buy the electrical output of the solar array under a 25-year power purchase agreement with White Pine. The developer is also taking the tax credits associated with the project as Healdsburg, as a municipality, cannot not use them. The tax credits help reduce the overall costs of the project, ultimately lowering costs for end-users. Healdsburg officials estimated that Healdsburg will save about $1 million compared with wholesale energy prices over the life of the power purchase agreement.

Among the benefits of a floating solar project is that it does not use up valuable farm land. Healdsburg, in Sonoma County, is in wine country. The solar panels also provide shade that can reduce water evaporation and algae growth, improving the quantity and quality of the water in Healdsburg’s ponds, which is used for irrigation.

Healdsburg is also in contract for another solar project in Southern California, for about 2 MW, and working through contract language to gain energy from an existing hydropower project. The three projects – floating solar, solar PPA, hydro PPA – combined with the city’s existing geothermal resources will put it “very close to the 60%-by-2030 renewable mandate,” Terry Crowley, the city’s utilities director, said via email.

Further in the future, the solar project could also be the basis of a microgrid. “Since the city is subject to transmission level Public Safety Power Shutoffs (PSPS) we are considering adding battery storage to effect a microgrid,” Crowley said. “A microgrid would help keep portions of the city energized during the loss of our single transmission source.”

Timing of the possible microgrid depends on utility scale battery pricing, Crowley said. “Right now, batteries, without significant state or federal funding, don’t pencil for our customers,” he said.

The floating solar project came out of a request for proposals (RFP) conducted by NCPA for its members as part of the agency’s community solar program. The city was one of seven interested members to participate in the program.

NCPA and its members began scoping the community solar project in 2016. “The primary goal was to support Community Solar and develop a fleet of solar plants in participating members’ service territories,” Sarah Taheri, state government relations and external affairs manager at NCPA, said via email.

NCPA’s role for Healdsburg included project management for site selection, site screening, conceptual physical and electrical layouts, fatal flaw analysis and Mitigated Negative Declaration (MND), California Environmental Quality Act (CEQA) filing obligations, as well as legal support and public bid process management.

“NCPA has multiple paths to assist members with meeting their local and state GHG goals,” Taheri said. In addition to its community solar program, NCPA also has a renewable RFP that solicits proposals for renewable energy resources, carbon-free resources, and energy storage solutions.

The intent of the rolling RFP is to provide members an avenue to continually assess projects that could support them in meeting GHG emissions reduction goals and requirements, Taheri said. Respondents can submit proposals at any time, she added.