Arizona Public Service's Diverse Solar Portfolio

By Barbara Lockwood

The utility operates one of the country's largest thermal-solar central generating plants and encourages wide installation of photovoltaic arrays on rooftops. It has a program to get PV arrays installed specifically on school rooftops, providing the buildings with power while introducing students to the benefits of solar technology.

One day our world will be powered entirely by renewable energy. While we can debate when this will occur, we cannot debate whether it will occur. In the past, we have seen starts and stops when it comes to renewable energy. But now, geopolitical imperatives, energy concerns, natural disasters and grassroots support all point in the same direction. We are already beyond the point of no turning back.

At the vanguard of this change is Arizona Public Service, the state’s largest and longest serving utility. APS has developed a diversified portfolio of renewable generation resources, including wind, biomass, biogas, geothermal and the most important renewable resource for Arizona, solar. Its 750 megawatts of solar capacity represents a highly diverse portfolio of technologies, including solar electric systems, solar water heaters and utility-scale plants, both photovoltaic and thermal.

Solana, one of the largest solar plants in the United States, is a thermal generator being built about 70 miles southwest of Phoenix. It will provide enough electricity to meet the needs of 70,000 Arizona customers. APS has committed to purchasing all the plant's output for the next 30 years.

In the Solana facility, parabolic mirrors will track the sun and focus solar energy onto a heat transfer fluid. In an exchanger, the liquid will convert water to steam, which will drive the plant’s turbines to create electricity. The thermal energy in the fluid can also be stored and used at a later time to generate electricity.

This means that APS customers will be able to receive solar energy even after the sun goes down.

Another major project in APS’s solar portfolio is the AZ Sun program. Here, the company is investing more than $800 million to build 200 MW of solar throughout the state. To date, installations amounting to 86 MW are in operation, with another 64 MW in construction and 50 MW awaiting final regulatory approval.

One element in this program, the 35 MW Foothills project, is located on state land that APS has leased for 35 years. The $10 million leasing proceeds go to the State Land Trust, primarily Arizona Common Schools, supporting grades K through 12. This model for utility-scale solar development has been recognized as a best practice around the country.

In addition to large solar projects, more than 20,000 APS customers have installed solar arrays on their homes and businesses. These systems can be as small as 2 kilowatts, like those on homes in Flagstaff, or as big as 20 megawatts or more, like the roof-top system at Arizona State University.

As we transition to renewable energy, we must look to the future. This means looking to our children, who need to learn about the changing world and get a glimpse of their future. It means bringing solar into their everyday lives. And the best place to make that happen is their schools.

APS has brought solar to more than 300 schools in 70 school districts across Arizona, resulting in more than 100 MW of solar. Students at these schools are getting an up-close and personal experience of how solar energy works and the benefits it brings.

The schools program provides the opportunity to “go solar” in two different ways. Schools can work directly with APS or with a qualifying solar contractor. In working with APS, the school is provided a solar system (free of charge), which APS owns, operates and maintains for the life of the system. In exchange for hosting the system, the school receives a special, fixed rate for the approximate output of the solar system, allowing the school to stabilize its energy costs. Each school is also provided the ability to have the students monitor, in real-time, the energy output of their school’s electric system. Teachers are encouraged to find ways to incorporate this learning opportunity into their curriculum.

Schools can also own the solar electric system themselves or work with a third-party solar provider. In either case, APS provides financial incentives to the school to help lower the cost of installing the system. If the system is not owned by the school, a third-party will own, operate and maintain the system. The school and the third-party then work out an agreement on how the school will pay for the output of the solar electric system.

Altogether, APS has committed to spend more than $300 million on solarizing schools.

Whether it’s installing small roof-top solar electric systems on schools in Phoenix, a large solar thermal plant in Gila Bend or a wind farm on the road to the Grand Canyon, renewable and solar energy are thriving in Arizona today. With the continuing development of renewable energy, APS and its customers are headed on the right path toward a brighter future.




Barbara Lockwood is the General Manager of Energy Innovation for Arizona Public Service (APS), managing APS’s expanding solar generation fleet, renewable energy programs and technology innovation efforts. As the company’s chief technology strategist, she led development and implementation of a self-healing grid program, energy storage systems, home energy management and electric vehicle programs. She joined APS in 1999, having begun her career at DuPont as a chemical engineer and manager. She holds a Bachelor of Science in Chemical Engineering from Clemson University in South Carolina and a Master of Science degree in Environmental Engineering from Georgia Institute of Technology.