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Fossil Fuel Backup Generators Hidden Source of Power, Pollution

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6,496 BUGs are littered throughout the Bay Area, capable of generating nearly four gigawatts of electricity, and producing upwards of 259,000 pounds of greenhouse gases a day, as well as thousands of pounds of other polluting air emissions, like diesel particulate matter, that can elevate public health risks. Points represent facilities which can have multiple sources or generators.

More than 6,400 backup generators – not counting the thousands of small engines in household garages and backyards – are littered throughout the San Francisco Bay Area, squatting at police stations, health care facilities, internet server farms and other places.  Ninety percent use diesel, a fuel that when burned can emit high levels of asthma-inducing particulate matter, as well as toxic carbon monoxide and smog-producing, climate-changing pollutants.

The engines mostly sit idle, waiting to be called on during an electricity grid outage.  But there’s so many of them, a slug of which – known as “prime generators” – are used more actively, that even their intermittent use can add up to notable emissions.  In an era in which many California municipalities, including San Francisco, are striving for 100 percent renewable power, the generators are a hidden fly in the ointment.  

All told, the Bay Area’s “BUGs” as they’re aptly named, have the capacity to generate more than 3,800 megawatts of power, roughly one-fifth of the state’s total electricity requirements on a mild spring Saturday. There’s almost 800 of them in San Francisco alone, able to make close to 530 MW, in excess of one-third of the City’s total needs on a peak demand day.  It’s likely that throughout California the swarm of BUGs is large enough to constitute a parallel, unseen, electricity system equal in generating capacity to the formal grid.

The generators have an important purpose. When the grid goes down, mostly as a result of distribution level outages, the BUGs light up, ensuring that water supplies continue to be pumped, college computers stay on, and emergency facilities remain at the ready.  Their existence, however, at a time of relentless change in the electricity system – including bankruptcy of one of the nation’s largest utilities and a chaotic scramble to manage how much the climate will change due to human activities – irritates public health, the environment, and the economy.  And with expanding availability of lower cost, dispersed, clean energy sources, existing BUG species can now be beneficially ushered into extinction, replaced by more wholesome creatures.

BUGs are largely invisible to the public, and to energy regulators.  Although their availability provides an extra layer of reliability to their owners, this benefit isn’t considered in multi-million-dollar generation and transmission investment decisions.  Instead, the state’s electricity grid operator, the inelegantly named California Independent System Operator, averts its eyes, and insists on having access to enough other assets to cover multiple potential system failures, not counting BUGs. It’s belt, suspender, button, and snap redundancies that increase electricity rates, which could increase by more than 20 percent over the next two years.  

The result is an inverse of private alarm systems.  Individual homes and businesses pay to install and operate them, but all taxpayers cover the cost of responding to the ensuing rise in distress signals, some of which are caused by strong winds, urban animals, or extra anxiety prompted by the felt-need for the systems in the first place.  BUG owners pay for their fossil fuel generators, but the extra dependability they provide isn’t considered in electricity grid planning; all of us pay for a larger network than necessary to safeguard reliability. 

A whiff of the generators can sometimes be smelt in the lobbies of tall buildings; diesel-powered stink BUGs being tested to make sure they’re operational. While their intermittent use makes individual generator emissions modest, the pollution can add up, as can the risks of diesel spills and mini natural gas explosions.  

Without being actively used during outages or the like, simply testing the Bay Area’s BUGs to see if they can fly emits the equivalent amount of carbon dioxide from almost 7,000 cars busily buzzing throughout the year, not even considering lung-damaging particulate matter. More than one-third are located within a half-mile of a school; in excess of one out of ten are even closer: a quarter mile, a five-minute walk, of concentrations of children. 

It hardly needs to be said that BUGs don’t meet municipal net-zero carbon emissions criteria. If they’re triggered, by an earthquake- or storm-induced utility distribution failure, the resulting plumes of diesel pollutants are likely to be cold comfort to those left without power. 

BUGs are a deadweight cost to their public and private sector owners, draining millions of taxpayer dollars into capital and operating expenses.  The hope is that they’re never used, like an unpleasant form of insurance.  Yet they could provide financial, environmental, and equity benefits if they were replaced with non-fossil-fueled resources and networked into the grid.  

Battery costs have declined by 76 percent over the past half-decade; renewable energy combined with storage can now compete against fossil fuel BUGs. Meanwhile, rapid statewide expansion of solar photovoltaics has upended the electricity supply curve, making power used during “ramping” hours, roughly 4 p.m. to 8 p.m., especially expensive. Extra demand during peak periods is filled by natural gas power plants, which could be replaced by sustainable storage, hiking the value of stowing renewable power and offering it to the grid when it’s needed.  Ongoing roll-out of “time-of-use” electricity prices, along with charges triggered when a customer’s energy demand exceeds certain levels, offers opportunities to price-arbitrage power use between time periods.  Storage companies are actively vending products that reduce electricity users’ expenditures based on these rates.  

As electric vehicle (EV) fleets, including light-, medium-, and heavy-duty, trucks, steadily expand, built-in storage assets will eventually be available to provide ancillary duty, to help manage business and grid reliability and costs. Given concentrations of BUGs in low-income neighborhoods that suffer from elevated asthma rates, particularly in the East Bay, their replacement with clean resources could serve to induce greater penetration of EVs in underserved locations, helping, along with reduced BUGs-related emissions, to improve environmental equity.

The California Public Utility Commission is leading a process under which the state’s investor-owned utilities are reimagining distribution investments at a local level, identifying community-based resources that could displace traditional “poles and wires” investments at a lower cost.  This, along with utility threats to turn off power when wildfire risks are high, could also make storage more attractive, potentially opening up revenue streams to those who now maintain storage capacity principally as a reliability measure.  Instead of being pests, BUGs could light the way.

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