Water-Cooled 566 Kilowatt Solar Energy System Installed at South Feather Water & Power Agency

A 566-kilowatt DC photovoltaic (solar energy) system was commissioned in July for the South Feather Water & Power Agency in Oroville. The 2.2-acre solar system, mounted on unused land adjacent to the freshwater treatment plant, provides all the electrical power for plant operations, including pumps, controls and other equipment, during the day. The treatment plant, which runs 24/7, uses grid power at night and on rainy days.

The ground-mount panels are tilted at the optimum angle to collect the most sunlight on summer afternoons. Water provided under pressure by South Feather both cools and cleans the solar panels to boost productivity. The total cost of the photovoltaic (PV) system was $4 million, of which $2 million was rebated by the California Public Utilities Commission.

The solar system produces surplus energy on sunny days, which is automatically sent to the grid for credit with PG&E in a net metering arrangement. The combination of solar energy and utility credits, which South Feather taps into for nighttime operations, will completely eliminate the agency’s net annual electric bill. South Feather will enjoy free energy after 2024, when the solar system will be paid off. The solar panels are warranted by the manufacturer for 25 years.

Energy costs are one of the largest expenses in running a water treatment facility. South Feather experienced spiking electric bills in the past five years, like all businesses and public works agencies in California. In 2003 South Feather’s electric bill, a significant component of the water agency’s annual budget, exceeded $160,000. The bill rose 17% annually over the previous five-year period.

“Going solar allows us to have more control over our rates,” said Michael Glaze, general manager of South Feather Water & Power. “As PG&E’s rates go up, our ratepayers’ water rates have to go up, too. I can’t imagine that a public agency would sit around and continue to pay an ever-increasing electric bill. When they can have the power for less money, doing nothing just does not make sense.”

Glaze assumed that PG&E, the local electric utility, would continue to raise rates, causing instability in South Feather’s annual budget. In recent years the agency has asked ratepayers to reduce water consumption between noon and 6:00 PM to save water and reduce energy use. The water agency switched to PG&E’s A-6 time-of-use rate schedule and installed more efficient pumps to reduce the treatment plant’s electricity demand and save money.

“By the time the solar project is paid for, our utility electric bills will be double what they are now, whereas with the solar system our payments are fixed over the next 20 years, and after that they’ll be free,” said Glaze. “Going solar was essentially the only choice.”

The 566-kW solar energy system, which generates the equivalent energy needed to supply 200 homes, removes South Feather’s demand on the public utility grid and adds energy to the grid during afternoon peak demand periods when California needs it the most. The state has a shortfall of energy on hot summer afternoons when air conditioning is in high use. This is also when solar produces the most energy.

The South Feather solar system replaces 603 tons of carbon dioxide that would otherwise be emitted into the atmosphere annually by a typical California natural gas-fired power plant. It takes 47 acres of trees to absorb this much CO₂.

Designed for High Performance

The half-megawatt solar system is composed of 3,060 Sharp 185-watt PV panels, two Xantrex PV225 inverters and one Xantrex PV45 inverter. The arrays, or groups of PV panels, are tilted at a 22.5-degree angle to collect the most sunlight during peak periods on summer afternoons at South Feather’s latitude.

PG&E’s time-of-use rate schedule is unique in the United States. During peak demand periods, from noon to 6:00 PM, May 1 through October 31, the utility charges 3.7 times the off-peak rate. Likewise, PG&E credits renewable energy producers 3.7 times the off-peak rate for energy that they send back to the grid during peak periods. South Feather’s solar system is oriented to earn these valuable peak-period credits, which the water agency taps into at night and on rainy days.

The active component of PV panels is silicon, and like silicon computer chips, PV panels perform most efficiently when cool. Heat causes electrical resistance in silicon, slowing computer chips and reducing energy production in solar panels.

Where computers have fans to keep the chips cool, the PV panels were mounted on open steel supports to allow air to flow across the top and bottom of the panels so they can shed heat. South Feather’s own crews graded the 2.2-acre PV system site and covered it with a weed barrier and crushed gravel to allow cool air from the nearby reservoir to flow unencumbered across the panels.

For very hot days, a water misting system was integrated with the steel supports for the PV panels. Water under pressure, readily available at the site, is supplied by South Feather. The misting system automatically switches on when the air temperature climbs over 90° F (32° C). A fine mist sprays into the space between the PV panels and the ground to move stagnant air and break up the convection effect. This lowers the temperature of the PV panels, boosting performance by up to 6%.

A separate water spray system installed rinses dust off the top surface of the panels during dry periods to keep them clean and productive. Airborne dust that settles on PV panels reflects sunlight, reducing their ability to generate electricity. The cleaned PV panels have up to a 4% value advantage.

The South Feather solar system is monitored in real time. Actual electrical production is posted live to an interactive kiosk in South Feather’s customer service center in downtown Oroville, and is also available on the Internet.

How Solar Works

Solar energy systems are composed of PV panels, inverters and a performance monitor. PV panels convert sunlight into DC (direct current) electricity. The inverters change the DC into safe, usable AC (alternating current), the same power supplied by electric utilities. The AC is distributed through a facility’s electrical service panels and flows to outlets, lights and switches. The performance monitor shows the amount of power the system is actually producing at any time. Solar is the cleanest form of energy production, is solid state and has no moving parts, needs little or no maintenance, runs all the time while the sun is shining, is silent and produces no emissions — air, ground or water — ever.

About Sun Power

Sun Power & Geothermal Energy designed and built the South Feather Water & Power Agency system. Sun Power (www.sunpowergeo.com) designs and constructs the most powerful large-area on-site solar energy systems in the nation. Sun Power is a leader in the integrated design and construction of solar systems for business, government, schools and homes, ranging in size from one kilowatt to one megawatt. Sun Power’s performance-based solar solutions are monitored real-time on the Internet via Sun Power’s proprietary SunSpot^® monitoring system. Sun Power is headquartered in San Rafael, California, and has regional offices in Oroville and Sacramento. Sun Power is a bonded and insured General B and Electrical C-10 contractor, California license #759086.

Contact: Greg Kerwin
Sun Power & Geothermal Energy
415-459-4201
greg@sunpowergeo.com

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