For San Antonio’s Water and Energy Utilities, Collaboration Leads to Conservation

A hydroelectric power station at a sewage treatment plant. Water meters that transmit data via a network built for smart electrical meters.

These are just two ideas for further collaboration between CPS Energy and the San Antonio Water System discussed at a joint meeting of the two municipally owned utilities. Tuesday was the first time the trustees overseeing both utilities have met as a group since 2011.

“There’s a lot of symbolism in the room right now with us coming together,” said San Antonio Mayor Ron Nirenberg, who serves on the boards of both utilities in his official capacity. “I would just hope that we can make this conversation have legs and get to work on how to make it operational.”

The joint meeting followed a case study released earlier this year by Environmental Defense Fund, an environmental advocacy group, highlighting how San Antonio’s sister utilities often work together in ways that conserve water and energy. The report says San Antonio “is on the front-lines of energy-water nexus progress at the utility level.”

“The city should serve as an example of how breaking down siloes (sic) benefits both the utilities and customers – by reducing inefficiencies and maximizing benefits such as rebates, as well as encouraging investment in large projects,” Environmental Defense Fund Senior Manager Kate Zerrenner said in a Tuesday email.

Though CPS Energy and SAWS have vastly different origins, the utilities have seen their paths align over recent decades. CPS Energy uses more SAWS water than any other customer, and SAWS is CPS Energy’s biggest customer, utility officials have said.

One of the best examples of collaboration is CPS Energy’s use of recycled water in its power plants that comes from SAWS’ sewage treatment plants. That offsets a need for 16.3 billion gallons per year in fresh water that would otherwise have to come from rivers or aquifers.

Much of the CPS Energy portion of the meeting focused on how SAWS can piggyback off of CPS Energy’s recent replacement of almost all analog electrical and gas meters with digital meters. The utility finished this four-year upgrade as part of its $290 million Smart Grid Initiative.

SAWS is now beginning a pilot program to install digital meters of its own, with $2.6 million proposed for the program in its 2019 budget. CPS Energy officials said SAWS meters will be able to use CPS Energy’s new network to communicate.

“We have a network system, and every single meter in the system is connected to that,” CPS Energy President and CEO Paula Gold-Williams said. “That is the foundation to connect water meters … smart lighting, environmental sensors, [and] additional sensors for businesses trying to track activity.”

For years, both utilities have taken advantage of various programs to reduce demand for water and power, the Environmental Defense Fund report states.

As one example, CPS Energy’s use of recycled water allows it to lease approximately 1,000 acre-feet per year of groundwater to SAWS. The water utility also participates in CPS Energy’s program to cut electricity use during peak hours, saving SAWS up to $250,000 some years in energy costs, according to the Environmental Defense Fund report.

The two utilities have also banded together to offer rebates to customers. For years, customers could get rebates from both SAWS and CPS Energy to install high-efficiency washing machines that use less water and electricity than conventional models.

That program ended as washing machines became more efficient, but CPS Energy still distributes low-flow shower heads and faucet aerators when it weatherizes homes under its Casa Verde program, the report states.

SAWS executives who spoke at the meeting emphasized how SAWS facilities can continue to host solar farms and other energy sources, something the utilities have previously achieved.

In 2012, SAWS allowed energy company SunEdison to install a solar farm at its Dos Rios Water Recycling Center, SAWS’ largest sewage treatment plant. CPS Energy now purchases all of the solar power produced at that site.

SAWS has also contracted with a private company to take waste methane gas generated during sewage treatment and sell it back into the natural gas pipeline grid.

Lately, the utilities have been mulling whether they should install a hydroelectric power system at the tail-end of the Dos Rios treatment process, where clean water from the plant cascades down a 60-foot stair-step drop before entering the Medina River, SAWS Chief Operating Officer Steve Clouse said. That gravity power could be used to generate electricity.

The utilities are also weighing whether CPS Energy could install a solar array and battery storage system at SAWS’ sprawling H2Oaks facility in South Bexar County.

“While we’re hopefully not in the business of building [power] plants anymore because of how efficient we’ve become, the idea of generation at a water facility is still very much a part of the conversation, particularly as it relates to decentralized generation in an efficient, renewable way like solar,” Nirenberg said at the meeting.

SAWS President and CEO Robert Puente said he was proud that Environmental Defense Fund found that most ideas for working together came from the utility’s staff, not from its governing boards or City Council.

“They think longterm, knowing a project they may be working on today might not come to fruition until 10, 15 years down the line,” Puente said.

Zerrenner said that in light of a recent international report on the devastating effects of climate change as soon as 2040, “viewing conservation through a multi-faceted lens is more important than ever.”

“Co-management of water and power exists at every level in both utilities, which is really unique and a major component of why San Antonio has been successful in raising awareness and conserving these two critical resources,” she said.