Santa Rosa to partner with Tesla in 'microgrid' project at wastewater plant

Santa Rosa is taking part in an innovative energy efficiency project that aims to improve the resiliency of the state’s power grid in part by parking a massive Tesla battery pack outside its Llano Road wastewater treatment plant.

The project, which is funded by a $5 million grant from the California Energy Commission, will allow the plant to quickly reduce the amount of electricity it draws from the power grid during times of high energy demand, such as afternoons during the recent heat wave.

In addition to reducing energy costs at the sewage plant, the project is slated to benefit ratepayers by generating revenue from sales of surplus electricity back to the grid. How much money the city could get from those sales isn’t yet known.

The Santa Rosa project involves a consortium of energy companies aiming to prove that big energy users like wastewater treatment plants can play a lead role in stabilizing a power grid increasingly reliant upon renewable - but less consistent - energy sources such as wind and solar.

“This is huge,” said David Guhin, director of the city’s water department. “If this is successful, it will become a model for treatment plants all over the state.”

Santa Rosa was one of two locations selected from a statewide pool of 40 sites that applied to set up a so-called “microgrid” at key infrastructure facilities.

The project represents another local collaboration with Tesla, the pioneering Palo Alto-based electric vehicle and energy storage company. Tesla Energy, a venture of the parent company Tesla Motors, previously partnered with Jackson Family Wines, installing 21 large battery systems at Kendall-Jackson winery and several of the Santa Rosa company’s other California wineries to smooth out spikes in energy use at the sites.

Santa Rosa’s Llano Road treatment plant is a massive operation, cleaning and recycling 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 use up to 5 megawatts of electricity per day, enough to power more than 3,000 homes. About 1 megawatt of that supply is produced on-site by generators running on biogas gathered from digesters that speed up the breakdown of waste material. That leaves about 4 megawatts of electricity that the plant needs to purchase daily from the power grid at a cost of about $3.5 million per year.

The plant already participates in a state program that pays it to reduce its power demand when needed. Upon request from utility grid managers, operators can lower the plant’s energy use by temporarily diverting up to 14 million gallons of wastewater to holding ponds for future treatment during non-peak hours. This significantly reduces the plant’s power use, freeing up valuable energy capacity, Guhin explained.

The problem is that it takes about an hour to accomplish, Guhin said.

Utility grid managers, however, need to be able to instantaneously balance supply and demand on the grid. Today’s power supply is increasingly coming from renewable energy sources that are more variable than traditional power plants, like gas-fired or hydroelectric, explained Michael Day, an engineer with Trane, the New Jersey-based company managing the project.

One way to stabilize the power supply would be to build more traditional plants, but “the problem is that as a society we’re taking those options off the table for the people who operate the utility grid,” Day explained.

So, the state is seeking to encourage more energy projects that help manage the demand side of the equation. Earlier this year it announced $27 million in grants under the Electric Program Investment Charge program.

Trane, which is known for its HVAC products but also manages renewable energy projects, reviewed the operations of numerous wastewater treatment plants in the state to find candidates for the project, Day said. Santa Rosa was far and away the top choice because of its size and existing commitment to sustainability, he said.

“It was like Barry Bonds versus the Little Leaguers. It wasn’t even close,” he said.

Details of the project were released earlier this month, after Trane and the commission finalized the contract.

The $5 million grant plus $2.2 million in technology contributions from the companies involved will fund:

The installation of a 2-megawatt Tesla Energy battery pack the size of a shipping container containing ?lithium-ion batteries similar to those that power the company’s $70,000 electric cars.

The construction of a 125-kilowatt photovoltaic solar array on site to recharge the battery pack. The plant currently has panels producing about 87 kw.

The addition of catalytic converters on the plant’s generators that will allow them to run more frequently and without violating air quality regulations.

Inverters and microgrid control equipment that will facilitate and automate the process.

The project is expected to be completed sometime in 2016.

Once it’s up and running, the plant will enjoy reduced energy costs and an improved ability to operate using local renewable energy sources, Guhin said.

It is too soon to say how much the city would be paid for the unused power it would sell back to the grid, but it will be purchased at a significantly higher rate than typical generation rates, Day said.

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