What to Know About Backup Diesel Generator Alternatives

Amid growing concerns over grid reliability, many educational facilities are looking to expand backup power capabilities.

Diesel generators remain the go-to option. Yet these systems contribute to local air pollution and global climate change — and, if not properly maintained, present reliability concerns of their own.

Some governing authorities are starting to issue waivers for the approval of certain alternative backup power systems. In the event of a power emergency, are these systems ready for prime time?

Diesel Generators Remain the Predominant Backup Power Solution

Generator use is growing. Since 2021, manufacturer Generac has seen a 70-percent increase in diesel generator sales as grid failures, wildfires, and extreme weather events become more common.

Diesel generators are the most popular backup power option. They remain generally reliable and relatively cheap. Benefits include superior load carrying capacity, proven ability to deliver high-quality electrical power, rapid response times, easy access to fuel supplies, and an expansive network of service professionals.

Following the National Fire Protection Association (NFPA) 110 Standard for Emergency Standby Power Systems, many jurisdictions only allow the use of liquefied petroleum (diesel), liquefied petroleum gas (propane), or natural gas. That said, the Centers for Medicare and Medicaid Services recently clarified that, if a local jurisdiction issues a waiver, critical facilities such as academic medical centers could rely upon alternative sources for emergency power.

Diesel Generator Challenges

Diesel generator emissions contain harmful levels of nitrous oxide (NOx), sulfur dioxide, particulate matter, and volatile organic compounds. Diesel engine exhaust can be filtered and scrubbed to reduce on-site pollution, but it is still a fossil fuel.

Modern units pollute significantly less than older models. Tier 4 generators emit 94 percent fewer NOx and 91 percent less particulate matter than Tier 2 engines. Still, diesel operations can undermine higher-education institutions’ goals to achieve carbon neutrality. To reduce campus-wide carbon emissions, many institutions are installing cleaner energy sources.

When not properly maintained, generators are prone to mechanical issues that can prevent equipment from starting or running as intended.

If generators are run infrequently, common issues include mechanical failure of the voltage controllers, dead starter battery, oil lubrication system, or fuel injectors. Among regularly maintained and tested generators, risks are more often related to failure of worn-out components. After the generator starts, failures could include engine overheating, component structural issues, or clogged filters due to degraded or spoiled fuel supplies.

Diesel generators can only last for as long as fuel supplies are available. As seen following 2024’s Hurricane Helene, disaster events undermine the availability of critical refueling supplies. Hospitals are required to store at least 96 hours of fuel onsite. Commercial facilities typically have enough fuel only to last 36 hours. Educational facilities do not have strict requirements and many fuel storage supplies last less than 24 hours. If diesel resupply shipments are disrupted due to a natural disaster or supply chain issues, the generator will eventually become useless.

Beyond reliability concerns, educational institutions are constrained by the limited space available for fuel storage. Facility leaders must balance how much real estate is dedicated to backup power or other campus space needs, such as parking, housing, and new academic facilities.

Alternative Backup Power Solutions

Many generator models are now available with dual-fuel capabilities. This flexibility enables facilities to use diesel, natural gas, or alternative blends — provided the facility has installed necessary storage infrastructure.

Fuel alternatives include renewable diesel, biodiesel, and hydrogen. Renewable diesel and biodiesel are chemically equivalent to petroleum-based distillate, instead produced using fats, oils, or greases. Hydrogen is a clean-burning fuel that emits water vapor as its only byproduct, produced through chemical reactions powered by natural gas or renewable energy

Natural gas, and potentially hydrogen in the future, come with the advantage of utilizing existing pipeline networks. That said, extreme weather events such as 2021’s Winter Storm Uri demonstrate that even hardened pipelines can experience pressure loss and production curtailment.

Solar energy can be harnessed and stored using lithium-ion battery technology. To work as a resilient backup power source, the battery energy storage system (BESS) will need to remain charged and ready in the event of a power disturbance. Capacity is dependent on battery size and solar output.

Because energy storage technology is still in its infancy, BESS is not relied on for long duration events (longer than 4 hours).  For applications where long-duration storage is required, a blend of technologies should be considered.

Fuel cells and linear generators produce power through chemical or electromechanical reactions. For both systems, new models are available that are fuel flexible, relying on natural gas, hydrogen, or other alternative fuels. Fuel cells and linear generators are dispatchable and energy efficient.

Gauging Risk

Any backup power system comes with some level of uncertainty. To identify the right system, it is important to understand the campus’ unique operational demands and infrastructure-specific requirements. Detailed engineering analyses should evaluate site-specific circumstances, financial considerations, and long-term planning goals.

Additional factors to consider:

• Is the local grid prone to outages? If so, campus leaders may want to think twice before relying entirely on intermittent backup power. A solar + BESS configuration may be sufficient if the local grid has proven to be generally resilient.
• Is the generator connected to a mission-critical facility such as a teaching hospital or high-value research institute? If a loss of power cannot be tolerated, for any reason or duration, specific analyses should be undertaken to ensure sufficient backup power.
• Are there plans to expand or redevelop the campus? Otherwise, replacing a generator’s mechanical, electrical and plumbing equipment will be costly.
• Will the local jurisdiction impose stringent pollution control measures? Some are restricting permits or increasing the operational costs of diesel-fired systems as part of policies to reduce on-site emissions or improve building energy efficiency.

Generators form the backbone of emergency power supply systems. When replacing a backup power system, educational facilities must tread carefully. If a power disruption occurs, having an appropriately designed system is crucial to ensure such critical infrastructure is ready for whatever the next emergency brings.

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Patrick Eddy is a project manager specializing in Power & Utilities at Burns Engineering, Inc. and can be reached at [email protected]. This is his first article for Facilities Manager.