How alumna Wenxi Zhao used a public service internship to explore the future of hydropower

Switching on a light and turning on a faucet require an epic collaboration that spans hundreds of miles. 

In August of 2020, the Pine Flat Dam in Fresno County was operating on a flat generating curve; irresponsive to the prices in California’s wholesale electricity market, the dam was generating energy at a fixed rate. Several constraints – including a minimum flow requirement imposed by California Fish & Game and a mandated maximum downstream temperature level – left the revenue subject to the fluctuating price of electricity. Power prices dropped in the afternoons when solar energy was abundant and rose in the early evening when people got home and increased demand. The dam’s power plant operation plan needed a tune-up.

As an intern at the California Department of Water Resources, Stanford University master’s student Wenxi Zhao, MS ’21, was assigned to look at the Pine Flat Dam’s generating curve and reshape its operating schedule to model and optimize revenue. After taking historical data and forecasted energy prices and running them through an optimization model, Zhao developed a plan.

“We wanted to sell our generation to the grid at times when energy prices were the highest, and store our generated energy when prices are low,” she explains. “By doing that, we would still get the best revenue without making significant changes to the dam operation.We proposed connecting a utility-scale energy storage system, which would store excessive generation from low-demand intervals, and sell that excess energy when the demand became higher.”

The first part of Zhao’s plan for changing the operating schedule of the dam is now under consideration to be incorporated into the Department of Water Resources’ generation plan. Zhao says that the second part of her plan – the battery system – is now being evaluated at pumping plants throughout the DWR system. The state water agency is both an enormous producer of electricity and California’s largest consumer, using power to move water to cities and towns.

“Grid-scale batteries could have two benefits,” says Zhao. “The first is that we will cut water delivery costs, and the second is that by doing this, we actually help the grid to replace some of its fossil fuel-based resources with renewable resources. So, we are kind of helping the grid to decarbonize itself.”

Zhao landed her internship at the DWR through Stanford’s Shultz Energy Fellowships program, named for the former U.S. Secretary of State George P. Shultz. The program provides opportunities for students to discover the work of government agencies in the energy sector and encourages students to consider careers in public service.

“As an international student, I never pictured myself in the public sector. I didn’t even think it was possible. But the experience of the fellowship gave me a whole new perspective of what public sector work looks like, and it turns out I enjoy it.”

Engineering water resources

Through an exchange program from China, Zhao spent her undergraduate years at University of Waterloo in Canada, where she majored in geology with a focus on hydrology. At Stanford, Zhao pursued the water resources track under her master’s degree program in the Department of Civil & Environmental Engineering. After taking the course Dams, Reservoirs and Their Sustainability with Prof. David Freyburg, Zhao says she became less interested in the science of groundwater and more into the engineering of water facilities.

“That course got me interested in how bigger water facilities are operated, and the challenges they will face with climate change and rising sea levels. How could they face the physical and economic challenges of a changing world?”

Inspired by the possibilities of engineering within water facilities, Zhao decided to apply to intern at the DWR through the Shultz Energy Fellowships program, which is a partnership of the Precourt Institute for Energy, Bill Lane Center for the American West, Haas Center for Public Service, and Stanford in Government. She began at the power and risk office of the DWR’s State Water Project. The  project stores and delivers water across the state of California; its facilities include canals, pipelines, reservoirs, and hydroelectric power plants. 

“I became fascinated by the work I did during my internship. I found it challenging, and I enjoyed seeing that my efforts could actually make a change,” said Zhao

The State Water Project’s power and risk office has hosted one graduate student and one undergraduate student from the Shultz Energy Fellows program each of the past five years. Ghassan ALQaser, chief of the power and risk office, mentored Zhao and all the graduate students so far.

"DWR is proud and elated to be part of and supportive of the Precourt Institute for Energy programs and their efforts in developing future energy leaders," ALQaser said. "All Stanford students who interned at DWR were exemplary during their tenures in terms of skills, being eager to learn and dedication to achieve set goals for their projects."

After graduating from Stanford, Zhao returned to the DWR to help develop an integrated resource plan for the State Water Project. Zhao is one of two recent Shultz fellows that have taken full-time jobs at their agencies after graduation. Ever curious, she described the possible paths she sees her career taking.

“I got really interested in the water-related laws involved in my project. It’s gotten me thinking how laws can affect the agencies underneath them, and how the cooperation of several agencies can add up to something really big that can make a difference in the renewable-energy future. But for right now, I’m really liking my work with models.”

Zhao also described the magnitude of the water and energy issues in California. 

“The more I dive in, the more I realize how serious the problem is and how many components within the system we have to coordinate to get the lights on and the water running. It is not easy.&rdquo

But Zhao has confidence that the work of the people in her office and across the state can solve some of the issues. She also thinks Stanford students have a lot to contribute.

“I hope more Stanford students come into the public sector,” she says.

Claudia I. Moses is a Stanford student and communications intern at the Precourt Institute.