| Independently Powered Energy News

A potential air quality crisis in the state best known for pollution regulation pushed the California Energy Commission into a full day forum Thursday on alternatives to diesel generators.

The use of backup generators has soared in California with the growing frequency of preventive power outages during climate-exacerbated fire conditions. That includes large diesel projects recently exempted from state permitting by the Energy Commission and hundreds of megawatts of utility diesel generators approved by the California Public Utilities Commission. The soaring use of these generators has raised serious concerns about the impacts to human and climate health.

“We know we have to do better,” CEC Chair David Hochschild said.

The CEC provides millions of dollars in ratepayer funds each year to advance new and emerging clean power technologies.

In the Bay Area alone, there are 10,000 permitted backup systems, according to Jakub Zielkiewicz, with the Bay Area Air Quality Management District. That is up from 7,000 systems three years ago. Of those, 60 facilities have a combined 1GW of diesel generation. Another 1.5GW of diesel backup is being installed at data centers.

Commissioner Janea Scott said the focus should be on replacing polluting diesel as soon as possible.

Data centers were a key focus of the workshop because of the size of the systems and rising number of data centers in and outside Silicon Valley.

Diesel fuel is cheap, powerful, and usually widely available. But it seriously exacerbates air pollution and undermines state efforts to decarbonize the economy by 2045. In addition, the delivery of diesel during extended outages can be constrained.

Air districts set emission limits for systems larger than 50 horsepower, but the restrictions do not apply during emergencies, notably during power outages. In addition, a considerable number of generators were installed before emission limits were set, Zielkiewicz said.

The Energy Commission certifies large diesel projects between 50-100 MW, but largely exempts them from the process.

Air regulators are looking for strategies to reduce emissions, particularly in struggling polluted communities, the California Air Resources Board’s Pippin Mader said.

Expanded use

Not only have diesel backup installations soared but so too has individual use. Last year, for example, one company ran its diesel backup 400 hours above its permitted allowance, Zielkiewicz noted.

The California grid operator’s Mark Rothleder said that energy resiliency was not the only thing driving up the use of backups, particularly at data centers. Zielkiewicz pointed not only to the August heat storm and local grid outages but also human error last year.

In addition to the growing number of backup systems and increased operating times, is the changing nature of their use.

“Outages are not all the same nature,” said Carsten Bauman, with Schneider Electric.

The vast majority of outages at data centers are typically about an hour, Bauman said. And because of rising fire-related power shutoffs, there is growing need for both short and long duration backup supplies.

A mix of technologies is preferable at these sites to address the different outage durations and reduce harmful emissions, panelist said Thursday. For example, batteries could keep power flowing during short outages paired with gas-powered fuel cells for longer term supply.

Gas-fueled backup systems, including those that run on natural, blended, and renewable gas, are currently considered the most reliable because the fuel source comes from underground pipelines.

Solar and battery-paired systems are becoming more common, but it is not practical to install them at sites with heavy demand. Solar arrays that serve large loads are land intensive.

Fuel cells and reciprocal gas engines

Much of the focus at the workshop was on solid oxide fuel cells and reciprocal gas engines, both which are far cleaner than running diesel systems.

Gas used in fuel cells produces power by an electrochemical process, thus there is no combustion. Bloom Energy has 265 MW of systems spread across hundreds of sites in California. Some businesses use them around the clock while others employ them as backup. But current regulatory incentives favor backup systems, according to Bloom’s Brian Kane, undermining the economics of systems running 24/7.

Many expect different gases to play a growing role in backup energy. Those include gas obtained from sewage, manure, or decaying garbage; and green hydrogen, obtained by spitting water with renewable electricity.

All these options are considerably more expensive than diesel on a narrow money cost basis. But proponents have long argued that if the grid services provided by clean backup energy were properly compensated, let alone health costs taken into account, they would outperform diesel.

Mike Petouhoff, with One Grid Energy Solutions, said Apple and many big tech companies have worked to green their daily power supply, but their behind-the-meter backup systems are another matter because of the costs. “The economics are tough, and we are looking for a more robust wholesale market.”

Gas-powered fuel cells and reciprocal engines can be dispatched to the grid and are cleaner than the natural gas-fired peaking plants they can replace, said Allan Schurr, chief operating officer of Enchanted Rock, a provider of natural gas fueled microgrids. With capacity and energy market payments, the net cost of these more efficient gas systems is between $50--$275 kW, and cheaper than diesel.