This is the twenty-third article in a series examining the technology, infrastructure, and development of data centers in Frederick County’s Critical Digital Infrastructure Overlay Zone (CDI-OZ). For this post, it’s time to get a bit technical!

In my June 22 piece, “Data Center Backup Generators: Separating Fact from Fiction,” I explained why hyperscale facilities continue to rely on EPA Tier 4 diesel generators. These systems meet some of the strictest emissions standards set by the U.S. Environmental Protection Agency (EPA) and Maryland’s Department of the Environment (MDE).

That article prompted a thoughtful reader question: “If cleaner technologies already exist, why are data centers still installing diesel generators?”

So, I did some research, and …

The short answer is reliability. Tier 4 diesel generators remain the proven, large-scale solution for emergency backup power. They start quickly, deliver high power density, and run on readily storable on-site fuel. The longer answer is that the industry is actively developing and testing what comes next.

The Bridge: Hydrogen-Assisted (Dual-Fuel) Systems

One promising transitional technology is hydrogen-diesel dual-fuel engines. These systems introduce hydrogen into the intake air alongside diesel, which serves as the ignition source. Because hydrogen burns more cleanly, it can displace a significant portion of the diesel under the right conditions.

Lab and demonstration projects have shown hydrogen substitution rates of 70–90% of the energy input. However, real-world emergency generators must perform reliably across wide temperature ranges, varying loads, and true outage scenarios. Achieving those high rates consistently in the field remains challenging.

Still, dual-fuel approaches offer a practical bridge: they leverage existing engine platforms while cutting fuel use and emissions. Commercial examples include dual-gas (hydrogen/natural gas) systems from manufacturers like INNIO Jenbacher, already deployed in some European data center projects for backup power.

Key hurdles before widespread adoption:

• Safe on-site hydrogen storage and new fueling infrastructure.
• Engine recalibration, certification, and long-term durability testing under emergency conditions.
• Supply chain and cost considerations.

This technology is real and advancing, but it is not yet plug-and-play for the demanding requirements of hyperscale data centers.

A Combustion-Free Future: Hydrogen Fuel Cells

The most transformative long-term option may eliminate combustion entirely. Hydrogen fuel cells generate electricity through an electrochemical reaction between hydrogen and oxygen, producing only water vapor, heat, and electricity. There is no combustion, meaning virtually no local emissions of NOx, particulate matter, or carbon monoxide—and far lower noise levels than traditional generators.

Major players are investing here. Microsoft has demonstrated a 3-megawatt hydrogen fuel cell system designed to match the backup capabilities of conventional generators. Partners like Plug Power, Caterpillar, Cummins, and others are developing scaled solutions specifically for data centers.

Fuel cells also offer operational advantages: faster response in some configurations and the potential for integration with renewable hydrogen.

What Still Needs to Be Solved?

The core fuel cell technology is maturing, but the bigger barriers are economic and infrastructural:

• Green hydrogen production via renewable-powered electrolysis remains expensive compared to grey or blue hydrogen.
• Storage and delivery: High-pressure tanks, cryogenic systems, or on-site generation add cost and complexity.
• Infrastructure gaps: Reliable hydrogen networks are limited in many regions, including parts of the U.S.
• Total cost of ownership: Upfront capital costs are higher, and round-trip efficiency (electricity → hydrogen → electricity) involves energy losses.

These are engineering, supply-chain, and policy challenges rather than fundamental scientific ones. Costs are expected to decline with scale, government incentives, and infrastructure buildout over the next 5–15 years. Complementary technologies like advanced batteries for shorter-duration support may also play a growing role.

Technology Evolves—So Must the Conversation

Data centers have a strong track record of innovation: servers are more efficient, cooling systems use less water and power, and AI optimizes operations in real time. Backup power is on the same trajectory.

Tier 4 diesel generators currently set the reliability and environmental benchmark for emergency use, but they are unlikely to be the end of the story. Hydrogen-assisted engines, fuel cells, batteries, and other hybrids are in active development and testing. Over the coming decades, as Frederick County’s CDI-OZ district grows, the backup power landscape will almost certainly become cleaner and quieter.

The bottom line: Public discussion should focus on verified performance data, realistic timelines, and balanced trade-offs—not yesterday’s technology or unproven promises. Data centers will need reliable power for the foreseeable future; the question is how quickly and cost-effectively we can make that power cleaner.

What are your thoughts on these emerging options? I welcome questions for future articles in the series.

Rocky Mackintosh, Broker of MacRo, LTD has been advising regional landowners, investors, and institutions for over 50 years.  He has been an active member of the Frederick community for over five decades and has served on a number of community organization boards, including as a member of the Frederick County Charter Board from 2010 to 2012.  He has firsthand experience supporting nationally recognized hyperscalers with site search and selection services throughout the Mid-Atlantic.