Project Profile: Solar Offset

April 18, 2017

Utilities are energy-intensive. No one knows that better than those who operate them and have to keep an eye on the energy consumed by treatment systems and conveyance, including pump stations.

“Wastewater and water plants are very energy-dependent and operate 24/7,” points out John Mandrick, utilities director for Florida’s Fernandina Beach Utilities Department, which is responsible for water and sewer services as well as stormwater management. “Anytime you can reduce the amount of power, it’s definitely beneficial,” he adds.

For Fernandina Beach, that has meant using solar power. And that choice is becoming more popular. Cindy Wallis-Lage, president of Black & Veatch’s Global Water Business, points out in an article on the company’s website that the water and wastewater industry consumes 7% of the electricity generated in the world.

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“Facilities across the globe are exploring solar, wind, biogas, and hydro as ways to offset high electrical costs and even contribute to the power grid,” she writes.

In Fernandina Beach, some 80% of the water utility’s service is provided to the city’s 18,000 residents and 20% to other residents of Nassau County.

The utility operation has three interconnected water plants, with a water system rated for 18.1 mgd and a typical peak of 7.5 mgd. Its wastewater system has a discharge rating of 3.5 mgd and utilizes direct surface water discharge. There are 37 lift stations.

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Fernandina Beach’s wastewater plant energy consumption averages 108,000 kWh per month for the treatment of average flow of 1.781 mgd.

“Our energy bill for the wastewater plant is between $9,000 and $12,000 per month,” points out Mandrick. “Our cost for energy is a little more than 11 cents per kilowatt-hour.”

Mandrick sought out ways to reduce the monthly electric bill.

In studying the options, Mandrick and his team considered wind turbines, “but our area in Florida is extremely poor for that,” he notes. Fernandina Beach is situated on the Atlantic Ocean and is Florida’s northernmost city.

Another option: an anaerobic digester. That was “cost prohibitive due to additional labor requirements. We chose solar due to the available sunshine and little to no maintenance needed,” says Mandrick.

“The ability to roll the meter backwards is why we’re putting the solar in our high-energy-use areas because we realize the utility industry and our electric utility provider is not going to pay us what the electricity is actually worth,” he points out. “The best we can do is reduce our usage and not try to be a generator. You’re never going to be cost effective when it comes to generating power on a large scale. We’re never going to be competing against 500 MW gas turbines with solar. Your best bet is to reduce your power footprint.”

Mandrick brought a lot of his own skills to the table for the project, given that he is a licensed engineer in the state of Florida who signs and seals his own plans. He’s also a licensed general contractor who pulls his own permits. Mandrick conducted an energy audit before launching the solar project to pinpoint areas of high energy usage.

“The main consumers were large horsepower motors that ran 24 hours a day,” notes Mandrick. “The blower motors on our digester are 200 HP and consumed 3,576 kWh a day—almost half of our monthly bill.

“So we figured out how to run the plant without them,” he adds. “We also switched as much lighting as possible off at night and changed most fixtures over to LEDs. After exhausting all the reductions we could do, we looked at how to make kilowatt hours to reduce our consumption from the electric supplier. Solar was the best fit for us.”

In 2010, the city of Fernandina Beach installed a beta system of 20 solar panels at the wastewater treatment plant and soon it had generated more than 30,000 kilowatt hours. The system is grid-tied with no energy storage, says Mandrick.

Fernandina Beach’s strategy is to execute the project in multiple phases.

“We are doing our solar projects in phases so that as we reduce our power bill, it frees up more funds in our budget to be used in capital projects each year,” notes Mandrick, adding the current total cost to build the solar array systems is averaging about $1.50 per watt.

“Anytime we reduce operations and maintenance costs, we try to move that money to additional capital projects that continue to reduce O&M expenses,” he adds. “Most components on a wastewater system need to be replaced within 20 to 30 years. Constantly funding capital projects is critical to maintaining a healthy utility.”

Mandrick points out that the solar array project was constructed with no grant dollars, but was 100% paid for by ratepayers’ money.

“Once we get our solar plan completed—we’re in phase six out of 10 phases—the wastewater plant should be 52% powered by the sun,” he says.

The first phase of the solar project began in March 2010, with the installation of a 4-kW system at one of the wastewater plant buildings as the beta test.

Following the success of that initial phase, the second phase was constructed in September 2014, where a 12-kW system was placed at a six-bay garage building at the wastewater plant. The third phase, a 12.72-kW system, was constructed at a conference room building at the plant.

The fourth phase, a 93.28-kW system, was a ground mount system placed at the wastewater plant in September 2015. Another 11.22 kW was placed at a warehouse at the plant in May 2016.

Several more phases are expected to follow. A 112.2-kW ground mount system was slated for completion in January 2017. In March, a 47.52-kW system is expected to be completed at the plant’s main warehouse, followed by a 19.8-kW system in May at the plant’s chlorine contact tanks.

The project is expected to be complete in 2018 with a 75.9-kW ground mount system in the plant’s rear swale area and a 19.8-kW system placed at Water Plant #3.

In all, the project at the wastewater plant will provide 630,000 kWh per year, which is 52.5% of the electricity consumed onsite and 2,673 kWh per year at the water plant, which is 1.78% of electricity consumed by the entire water system.

The system has a 25-year life span and is expected to generate a savings of $341,685. It will pay for itself in 7.63 years, Mandrick says.

The savings figure is derived from 25 years of operation of 400 panels through two systems, accounting for an electric rate of $0.113 per kWh with the solar power generation turning out to be an average of 14,504 kWh per month.

Mandrick emphasizes that in order to do projects such as this in-house, he had to form a team.

“Part of the team is the use of outside contractors for a specific task,” he says, adding that the city turned to Bobbi Elliot of Fishers CAD to be the contract drafter.

“Fishers CAD provided drafting services for me so that I could put together a plan set to submit for permits and build the facilities,” adds Mandrick.

In 2014, the Fernandina Beach City Commission approved the purchase of 400 Suniva solar panels to annually generate 179,172 kWh of electricity for the wastewater treatment plant.

“We custom designed all our own systems and installed them with our own crews,” notes Mandrick.

The installation is expected to reduce the amount of electricity purchased from Florida Public Utilities and provide for long-term stable power production.

While financial savings is the major benefit of the project, the system is expected to produce environmental benefits as well, reducing the amount greenhouse gases from burning coal to generate electricity by 123 tons annually.

The City of Fernandina Beach’s 93.28 KW ground array system. Pictured: John Mandrick, PE, and Bobbi Elliot of Fishers CAD

In addition to relying on renewable solar energy, Fernandina Beach’s wastewater facility also does its best to save energy though the use of a Carrousel System treatment system with secondary clarification. That system is designed to offer energy efficiency benefits as well.

The Carrousel System is designed as a “racetrack” style reactor basin with at least one vertical shaft, low-speed mechanical aerator—the Excell Aerator—installed in the center of one of the turns.

The basic system provides full BOD and ammonia reduction. Nutrient removal is added to a Carrousel System via the addition of anoxic and anaerobic selector zones or through optimized operational strategies.

The Carrousel System utilizes the Modified Lutzack-Ettinger configuration, designed for highly-efficient denitrification. The denitIR System process entails an internal recycle (IR) flow directed into the anoxic zone through a slip-stream channel using propulsion generated by the Excell Aerator. No additional energy for IR pumping is required. The IR flowrate is varied by the EliminatIR Gate. The Oculus Control System automatically controls the aeration rate and IR flow.

Additionally, the wastewater plant utilizes facultative digestion, which reduces mass by 60% without the need for blowers, notes Mandrick.

Twice a week, the wastewater operation hauls 20 tons of dewatered residuals to the local landfill.

Another state-of-the-art approach at Fernandina Beach’s wastewater treatment facility is that there are no blowers used for treatment, Mandrick points out. “We add bacterium to the process and use mechanical aerators with automatic dissolved oxygen control with variable frequency drives,” he says.

Fernandina Beach’s solar initiative has attracted international attention. During September 2015, international dignitaries from Bhutan, India, Iraq, Kazakhstan, Solomon Islands, Sudan, Suriname, and Thailand visited the Fernandina Beach Utilities Department as part of a regional tour sponsored by GlobalJax, the regional partner for the State Department’s International Visitor Leadership program.

Fernandina Beach was chosen as a destination for its exemplary state-of-the-art wastewater treatment facilities and for demonstrating innovative financial, scientific, and technical strategies for assessing, monitoring, and conserving water resources.

Mandrick’s advice to other utilities looking to go the route of reducing energy costs after conducting an audit to ascertain where the power is being used: “Start small and continue to build larger systems each year. Utilize your own staff. They will take ownership and feel pride in their facility.”