DEC 2015
River Power: Where Solar and Flowing Water Meet

Recently two San Diego professors proposed a new use for a 10+ mile stretch of the Tijuana River: a huge solar energy farm. The portion of the river under consideration was converted to a concrete canal over forty years ago in order to reclaim and develop the surrounding flood-prone land.

According to the San Diego Union-Tribune, the project is envisioned as a “giant energy farm” running along the length of the channel that would involve placing solar panels across the top. Underneath the panels, the professors have proposed using algae systems to clean the river water before it intermingles with the Pacific Ocean.

The idea grew out of a class the pair taught at University of California San Diego. The plan is projected to produce 94 megawatts of solar energy, enough to power 30,000 homes, while also cleaning the roughly 13 million gallons of water that flows through the canal every day.

This innovative use of solar technology on canals was pioneered by SunEdison in 2012 for the Narmada Canal Top Project in Gujarat, India and implemented again in the recently completed 1-megawatt DC canal-top solar power plant in Karnataka.

Canal-top solar plants offer some unique advantages. The opportunity to use a canal’s existing structure for panels means there’s no need to acquire or develop additional land, saving an enormous amount of money and time. In addition, the canal and solar array mutually benefit each other. Panels tend to operate more efficiently when they’re cool and the cool river water brings down the temperature of the panels, allowing more power to be generated. In turn, the panels shield the water from the hot sun, reducing water loss from evaporation.

Canal-top plants like the one proposed for the Tijuana River can also provide some unique challenges, including potentially higher construction costs than land-based projects, and less control over the placement of PV panels—southern exposure is optimal (for projects in the northern hemisphere), but on a canal that curves through the landscape, may not be possible.

U.N. Secretary-General Ban Ki-moon had high praise for India’s canal-top solar projects on a visit in January, saying, “I saw more than glittering panels—I saw the future of India and the future of our world. I saw India's bright creativity, ingenuity and cutting-edge technology." 

By the end of 2017, India’s Ministry of New and Renewable Energy plans to create 100 megawatts of capacity from solar power plants built on canals and their banks.