Apr. 23—The City of Mesa wants to get into the business of producing its own electricity to supply Mesa electric utility's 17,000 customers during peak demand times.
The utility's service area covers 5.5 miles in the city's core.
Producing its own energy would allow the city's electric utility to avoid the open energy market when prices are high during times of peak demand — such as sundown when solar generation is declining and people are returning home from work and flipping on lights and air conditioning.
To make the city-owned electric utility better able to meet these peaks with in-house electricity, Mesa is eyeing investments in plants powered by natural gas.
That fossil fuel emits about 117 pounds of carbon dioxide into the atmosphere per million BTUs, compared with 160 pounds for gasoline and 200 pounds for coal.
The city Energy Department staff said during a budget study session last week that they are considering land next to the Rogers Substation at University Drive and Stapley Road, just north of the Sherwood Mesa neighborhood, for a "large-scale" natural gas power plant in the future.
The project is still in the study phase, staff said.
The alternative to building a natural gas power plant like this, according to staff, would be utility-scale battery storage.
Big batteries can add energy to the grid at the flip of a switch and can be charged from solar sources or from the energy market when prices are low.
While staff said it is still exploring both a large gas-fired plant and battery storage, the mayor endorsed moving forward with adding robust gas-burning capacity.
"Natural gas is not renewable energy," Giles said, "but until we develop the sustainable technology to avoid it, I think it is how you bridge the gap. I think that gap will be there for a generation or more."
Energy Resources Program Manager Tony Cadorin told the city council that Mesa would take its first steps into natural gas generation with the installation of two 3-megawatt natural gas generators downtown to power microgrids tied to public safety facilities and other critical services.
The first of those generators is currently in design.
Staff said the two smaller generators will be available during emergencies, but they will primarily be used to produce electricity for the Mesa's eclectic utility during peak energy use times, running between three and nine months a year, Cardorin said.
The mayor asked if this plan worked on a small scale, then why shouldn't the city consider doing it at a large scale.
Staff told the mayor it is indeed interested in large-scale generation.
City Manager Chris Brady said that burning natural gas could be especially lucrative for the city because "we're in the natural gas business."
Brady was alluding to Mesa's natural gas utility, which could presumably supply the fuel for its power plants at lower cost than buying it on the market.
All the talk of the city ramping up its fossil fuel use prompted Councilwoman Jenn Duff to remind her colleagues and staff about Mesa's Climate Action Plan.
Passed in 2021, the plan calls for the city to draw down its fossil fuel use and reach 100% renewable energy sources by 2050.
"I appreciate that we're doing this microgrid for resiliency and self-reliance," Duff said, "but I do caution if we do a lot of expansion in this we have to put it in line with our sustainability goals because natural gas is still burning fossil fuels."
"We have to balance (gas plants) with growth opportunities that meet our sustainability goals," she added.
Mesa Energy and Sustainability Director Scott Bouchie replied that Mesa can't expand its reliance on solar energy without other power sources to fill gaps.
He said that battery storage, natural gas and the energy market "are different pieces to the puzzle," and the city would be studying the "best combination" of those and would present its findings to council later.
"When you talk to SRP, they look at ... either natural gas or battery storage as the key for them to expand their solar capabilities," he said.
Councilman Mark Freeman predicted that large-scale battery storage would be critical in the future, but added:
"I do have some concerns about some battery storage, because there has been battery fires in Surprise as well as Chandler that knocked out a lot."
Mesa residents seem to have mixed views about renewable energy.
When Mesa updated its Climate Action Plan last year with resident feedback, a group of residents praised the effort, but one commenter asked the city to be more ambitious with its climate goals and speed up its target for carbon neutrality from 2050 to something sooner.
On the other hand, in the council meeting following the study session in which staff members presented plans to develop natural gas plants, a citizen decried the city's investments in green initiatives like public transportation and tree planting.
"We don't need the taxpayers forced to do anything except minimum services, " she said.
If Mesa steps into the natural gas plant business, it could be in it for a long time. The website of power plant designer Sargent and Lundy says owners should anticipate a 25- to 30-year life span for natural gas generators.
Large Arizona energy suppliers SRP and APS are still dependent on burning fossil fuels like coal and natural gas for most of their electricity, but they have plans to draw these fuels down by 2050.
If Mesa moves forward with a large-scale natural gas plant, it may have to build or buy a lot of solar or other renewable sources to keep up with the renewable portfolio of the wider energy market.
Mesa energy officials said the city is making progress on expanding Mesa's use of solar at the same time as it is planning investments in natural gas generation.
Cadorin told council the city has the first round of downtown solar panel installations, with .8 megawatts now installed in the City Plaza area.
An additional 2.8 megawatts of downtown solar panels are also in the works for the library, transportation building, Mesa Arts Center and other city buildings.
Cardorin also said the city is negotiating with SRP to purchase 16 megawatts of solar power, which is equivalent to about 15% of Mesa's annual energy.
If a deal is signed, "it will be a huge step forward for Mesa in terms of Climate Action Plan progress," he said.
In addition, Cadorin touted a pair of projects that aim to reduce the impacts of Mesa's use of natural gas, a partnership with company Project Canary to detect gas leaks using infrared cameras, and a Flare to Fuel project that will capture methane produced during the wastewater treatment process and turn it into utility-grade natural gas.
Previously the city burned off the methane in a flare to convert it to less harmful CO2. Cardorin said the captured gas could supply 20% of the fuel used by the city's fleet of compressed natural gas vehicles.
