SLO County will install floating solar energy panels like ones shown here in Lake County in a wastewater pond at the Los Osos sewer treatment plant to cut energy costs and slow the growth of algae. Photo courtesy Annie Seacrest

County Supervisors last week approved putting in a floating solar energy plant at the Los Osos Wastewater Treatment Plant in an effort to cut energy costs and reduce harmful algae growth.

Annie Seacrest, the County’s Energy and Water Coordinator, who has been very successful in getting several solar energy projects built at various county facilities, brought the project to supervisors, after trying for some time to figure out how to cut energy costs at the sewer treatment plant, which is located behind the Los Osos Cemetery.

“Unfortunately,” Seacrest told Estero Bay News, “there isn’t a lot of available ground space at Los Osos to begin with. The space that is available is set aside for preservation as part of the original environmental assessments conducted when the plant was built.
“So, a ground-mount system, like the one at the County Operations Center [off Hwy 1], won’t work. We also looked at a canopy system, like what is out at Dairy Creek Golf Course, but we don’t really have a lot of parking lot space for that, either.”

Even rooftop-mounted solar panels were nixed. “Finally, a rooftop system [we don’t have any of these yet] wouldn’t work because the available roof space was rather small and wouldn’t result in anything that could help offset electricity costs. As such, the floating is such a great option for this site not only for the energy aspect, but for the trihalomethane prevention.”
According to her staff report, the project would install a series of floating solar panels on a wastewater pond at the plant. That pond holds rain runoff and plant overflow treated wastewater.

The project would be installed on approximately 1.6 acres of the recycled water ponds at the facility. “The Facilities Planning Division is responsible for overseeing the efficient and fiscally responsible management of energy use at County of San Luis Obispo facilities,” Seacrest said in her report. “The Utilities Division is responsible for the administration and operation of safe and reliable potable and non-potable water systems such as the LOWRF (Los Osos Water Recycling Facility).

“This site was determined to be an excellent candidate for a renewable energy project due to the high energy costs of operating an energy-intensive facility and a need to maintain and improve recycled water quality.”

The County has been looking for a renewable energy project at the plant since late 2017, just over a year after the plant went on line in April 2016. In the end the County decided a floating system would work and potentially head off another troublesome problem with such ponds, the proliferation of algae growth and production of harmful, though naturally-occurring bi-products.
“Towards the end of 2018,” Seacrest said, they “determined a floating solar system could not only significantly offset energy consumption, but also reduce the amount of physical and chemical maintenance of the recycled water and greatly improve the water quality.”

The County identified three benefits from the solar floats — cutting energy costs, improving water quality for recycling, and reducing water loss by evaporation.

“The LOWRF is one of the County’s top five energy consumers,” Seacrest said, “so the primary benefit of installing the floating solar array will be reducing energy costs by offsetting energy consumption. This will demonstrate a responsible use of ratepayers’ dollars by providing an opportunity to use the electricity savings towards LOWRF’s ongoing operations and maintenance needs.”
She added that the solar arrays will cut gas emissions, and support SB 350, the State’s clean air and greenhouse gas reduction law.
Since the floats will cover a large part of the water pond, it cuts the available surface area and should inhibit algae growth. And algae growth leads to the formation of “trihalomethane,” a bi-product of chlorine reacting to organic compounds in water, she explained.

“The proposed floating array,” she said, “will decrease the pond’s water temperature by blocking the sunlight, two major factors of algae growth. The reduction of algae growth in the pond will reduce the overall solids concentration, which reduces the production of trihalomethane.”

So is trihalomethanea problem at what is still a relatively new plant? Seacrest said, “It’s something that happens with facilities such as this. Reducing the amount of algae growth in the pond will also reduce the overall solids concentration, which reduce the production of trihalomethane. Currently, the plant spends money on efforts to combat the trihalomethanes. By covering a significant portion of the area exposed to sunlight, the algae growth should significantly decrease, as should the use of chemicals to treat the trihalomethane.”

The floats will also slow evaporation losses, which Seacrest estimated at 4.68-acre feet a year, and is due mostly to wind, a prevalent factor through Los Osos Valley for much of the year.
And perhaps most important to Los Osos residents within the assessment district, who foot the bill for this plant and the collection system, is that it won’t cost them anything.

As with the solar farm on Hwy 1, the County is entering into a partnership with a private energy company, which will pay for the equipment, install it, and then operate and maintain it, charging the County a set price for the energy.
The company, Floating Solar Solutions SLO County I, LLC (FSS for short) will pay for the over $3 million facility, which is what Seacrest said it would probably cost the County to build.

The business arrangement is called an “energy service agreement,” and it’s the same arrangement that was made at other County facilities solar and battery projects are being installed.

“The price per kilowatt hour we are proposing to enter with FSS will cover the costs of the system, including engineering, construction, etc.,” Seacrest told EBN. “As such, we don’t pay any upfront costs for the system. FSS is responsible for the production, operations, and maintenance of the system for the duration of the contract. Once again, we ensured the County would

have some security built into the contract by stipulating production output and minimum performance guarantees.”
In her staff report, Seacrest broke down the costs to the County and the savings to be had. The set new energy rate is 15¢ per kilowatt with the plant currently paying Pacific Gas & Electric 17¢ a KW.

In 2019, the plant used 1.59 million kilowatts costing $280,300. In year one the floating solar panels will produce 1.23 million kilowatts and cost $185,800. Add in $62,500 to PG&E to make up the difference and the total energy bill in year one is $248,400, a savings of $31,900.

Over the solar farm’s 25-year life the County expects to save $3.14 million, according to Seacrest’s figures. This assumes a 3% per year increase in utility costs, however, in 2019, PG&E’s rate hike was 4.99%, she added.

As part of the Supervisors’ approval, Seacrest and the County will have to ask the U.S. Department of Agriculture for permission to lease the pond site to FSS for the solar array, which Seacrest said was mostly a formality.

USDA loaned the Los Osos Wastewater Assessment District the money to build the project through a rural assistance program, which took an act of Congress to achieve, a feat accomplished by former Congresswoman Lois Capps. Such funding is normally limited to communities of less than 10,000 population.

The project is one of a series of recent accomplishments for the County which installed solar energy systems at Dairy Creek Golf Course; the Hwy 1 solar farm; the County Health and Behavior Health Agencies on Johnson Avenue in SLO; and will be installing Tesla battery systems at three County water system facilities, designed to keep them working in the event of public safety power outages by PG&E.