Solar panels to help power Santa Rosa micogrid

When California’s energy grid gets stressed out during heat waves, energy managers send out so-called flex alerts asking people to conserve energy.

An innovative energy project underway in Santa Rosa aims to take that flexibility to new levels by helping a huge energy user - the city’s water treatment plant - quickly reduce its energy usage while still performing its core mission of cleaning water.

A 125-kilowatt solar array popping up above the parking lot of the Laguna Subregional Water Reclamation plant on Llano Road is the first visible sign of a yearslong effort to turn the plant into a microgrid capable of reducing its use of electricity from the grid.

“Increasing our flexibility to produce energy on-site allows us to adjust our demand on the macro grid, and doing that is worth money,” said Mike Prinz, deputy director of Santa Rosa Water.

Microgrids, as the name implies, are small electric networks that can operate, to varying degrees, independently of the larger electrical grid managed locally by Pacific Gas & Electric Co.

The solar panels are not the core of the new system, but will help recharge the batteries that are being installed later this year as part of the project.

“These are icing on the cake,” Prinz said.

The 372 panels are mounted on steel supports above the parking lot, a technique becoming common for commercial-scale solar installations.

The panels will help recharge the storage batteries that, combined with upgrades to the plant’s four large gas generators, will allow the plant, when asked by grid managers, to reduce its demand on the grid.

“They’ll get a call that says, ‘You need to reduce. How much do you want to reduce?’ It’s voluntary,” said Richard Swank, a program manager with Trane.

The energy company in 2015 won a highly competitive $5 million grant from the California Energy Commission to test the viability of a microgrid on such a large facility.

The treatment plant cleans and recycles an average of 17.5 million gallons of wastewater daily from 250,000 customers in Santa Rosa, Sebastopol, Rohnert Park and Cotati. The plant’s pumps, aerators and ultraviolet disinfection system consume an average of ?4.4 mega-watts of electricity, enough to power nearly 3,000 homes.

The plant has recently increased its ability to produce electricity from biogas from both human waste and commercial sources such as food, oil and grease. Today it can generate more than 1 megawatt of electricity on-site through this method. But that still leaves a lot of electricity to buy from its provider, Sonoma Clean Power.

The microgrid project will enhance the self-generation capacity further by installing large catalytic converters on two of those large gas generators, allowing them to operate on up to 100 percent natural gas and still remain within strict air quality regulations, Prinz said.

The expectation is that because of the low cost of natural gas, the plant will be able to generate its own electricity less expensively than what the utility would charge, Prinz said.

The city may benefit further by getting paid for reducing its energy use during these peak periods, but how much remains to be seen, Prinz said. Once the project is up and running, the city will operate the plant with an eye toward maximizing value for ratepayers, he said.

The treatment plant solar installation avoided the fate of a recently canceled Sonoma Clean Power solar project. That far larger project sought to build 12.5 megawatts of power on six Sonoma County Water Agency holding ponds, but fell victim to a number of challenges, including President Donald Trump’s tariff on imported solar panels.

But the solar panels at the treatment plant were purchased before the tariffs went into effect, Swank said, from an Ontario-based company called Canadian Solar.

You can reach Staff Writer Kevin McCallum at 707-521-5207 or kevin.mccallum@pressdemocrat.com. On Twitter @srcitybeat.