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Backup power for data centers of the future: the case for hydrogen fuel cells

By Nicholas Reppas
28-02-2024 | 7 min read

Accelerating digital transformation and advances in artificial intelligence (AI) is ushering in an unprecedented demand for computational power and storage, leading to a significant expansion of data centers worldwide. Today, data centers serve as the foundation for digitalization and connectivity. At the same time, their immense power consumption means they have an important role to play in addressing climate change.

In 2022, data center electricity consumption was estimated at 240-340 TWh, which is equivalent to approximately 1-1.3% of global electricity demand1. In recent years, many data center developers and owners, including the likes of Microsoft, Amazon, Alphabet, etc., have taken steps to address sustainability concerns by leveraging renewable sources, primarily through clean power purchase agreements (PPAs). Some data center developers have also announced plans to power their facilities directly with renewable sources.

These efforts are a critical step on the journey to carbon neutrality. However, decarbonizing emergency backup power is a problem that the industry has had difficulty solving.

Emergency power for data centers

Reliable power is a requirement for all tier standard-compliant data centers in operation today2. Disruption to grid power is not considered a failure, but an anticipated operational condition that the facility must be prepared for.

In recent years, data center owners have made strides to reduce power-related outages, though they are still a major pain point. According to a 2022 survey from the Uptime Institute, power-related problems accounted for 43% of significant outages at data centers (outages that caused downtime and financial loss)3.

Moreover, the cost of downtime is increasing. In the same Uptime survey, it was reported that 60% of failures resulted in at least $100,000 in total losses, up from 39% in 2019. The share of outages that resulted in >$1 million in losses increased from 11% to 15% over the same period.

Given the importance of uptime on profitability, it is no surprise that data center owners continue to rely on tried-and-true technologies like diesel generators as a source of backup power. This is despite their high NOx, SOx, and carbon emissions, which are increasingly at odds with the industry’s desire to reduce its climate impact.

Permitting is also becoming a challenge in many regions, as authorities look to implement more stringent emissions regulations. So too is noise. Even without a power outage, diesel generators require weekly testing (i.e., running on no load) to ensure operability.

Today, clean alternatives to backup diesel generators are limited. While some developers have turned to natural gas-fired generators to reduce their carbon footprint, they are still incompatible with net-zero ambitions. Furthermore, NOx and SOx emissions are not eliminated, and noise levels are similar to that of diesel generators.

Batteries are critical for delivering the instantaneous power provided by uninterruptable power systems (UPS). However, batteries are typically not a viable option for handling the sustained power loads that many data centers require for backup (i.e., continuous power for hours or possibly days). Large data center power demand can range from 100 -1000 MW. A battery system capable of handling the facility’s entire load for an extended period of time would be highly prohibitive from both a footprint and CAPEX perspective.

Producing clean, dispatchable power with hydrogen

Hydrogen-powered fuel cell generators represent a captivating prospect for data centers seeking an alternative to diesel for backup power. The central challenge lies in balancing the use of UPS (for providing immediate power to critical loads), BESS (for mid-duration energy storage and backup power), and fuel cells (for long-term backup power) to ultimately usher in a future where diesel generators are no longer needed.

Fuel cells generate electricity through a chemical reaction between hydrogen and oxygen. The only byproduct of the process is water and heat. If the source of hydrogen for the generator is green (i.e., produced via water electrolysis powered by renewable energy), lifecycle emissions are close to zero.

Having the capability to produce clean, dispatchable power also opens up potential opportunities for data centers to realize additional revenue streams by participating in demand-side management. Although this is not an option today, it could become relevant for regions or cities with constrained power grids or where there is high penetration from intermittent renewable sources, like wind and solar. In such cases, if there is a need for additional power or grid stabilization, the hydrogen-powered generators can start up and inject clean electricity into the grid.

Similarly, if load needs to be shed due to a temporary reduction in grid power or if the price of electricity spikes due to high congestion, the data center can come offline and operate in island mode without any adverse environmental impact.

At Hitachi Energy, we believe this is what the data center of the future could look like -- a highly flexible and low-emissions facility that plays an active role in ensuring the stability of the external grid.

In the future, data centers won’t merely exist as isolated energy consumers on the outskirts of the power grid. Instead, they will seamlessly integrate, becoming essential components of the entire system. By embracing innovative approaches, harnessing cutting-edge technologies, and actively participating in demand-side management, data centers can contribute to a more sustainable, flexible and secure grid.


Fabrizio Landini
Industry Network Leader for Data Centers
Hitachi Energy

HyFlex Hydrogen power generator

Hitachi Energy works closely with data center developers to connect their facilities to the grid. We are also developing a hydrogen power generator solution, called HyFlex, that can be used to provide clean backup power for data centers, as well as other applications, including construction sites, mines, etc.

HyFlex is a plug-and-play system, which includes fuel cell modules, power electronics, batteries, cooling, and auxiliaries. The generator is enclosed in an easily transportable container that converts hydrogen to clean electricity with minimal noise emissions.

HyFlex is completely emission-free during operation and has a low overall lifecycle footprint, producing AC power, usable heat, and water. In comparison, a 1 MVA diesel generator running at full load combusts roughly 225 kg of diesel and emits 720 kg of CO2 emissions per hour.

In November 2023, we inaugurated our first HyFlex “Demonstration Unit” which is currently available for trial purposes in Europe. The first commercial deliveries rated at 400 – 600 kVA are currently being discussed with several partners.

A high-power variant is being developed for permanent and fixed installations. The larger unit will be designed to operate in parallel and capable of meeting a broad range of megawatt-scale power requirements for facilities like data centers and other critical infrastructure in the future.

Charting a path forward

Some data center owners have already begun testing the use of hydrogen fuel cells in place of diesel generators for backup power. Today, the primary hurdle preventing wider adoption is not the technology itself, but rather procuring a reliable and low-cost supply of clean hydrogen for fuel.

A number of large-scale electrolyzer plants are set to come online over the next 5 – 10 years. Although many of these projects already have long-term offtake agreements in place with end-users, global green hydrogen production capacity is forecasted to increase substantially through 2030. As supply chain networks are established, costs will come down and the viability of using hydrogen fuel cells for clean power will increase. Some developers may even begin exploring the potential of building their data centers in proximity to green hydrogen plants or hydrogen pipelines to ensure security of supply.

Initial CAPEX is also an adoption hurdle if the hydrogen generators will only be used for backup power. However, in the future, if the data center can realize additional revenue by participating in grid ancillary services as described above, the return on investment (ROI) could improve significantly.

For some data centers, conditions may already exist to begin plans for a phased approach, where diesel generators are slowly swapped out for hydrogen generators.

By gradually transitioning between fuels – for example, by running one hydrogen generator in parallel with multiple diesel generators – developers can test the technology and improve sustainability without introducing any additional risk of downtime.

Gambia Mangroves. Aerial view of mangrove forest in Gambia. Photo made by drone from above. Africa Natural Landscape.

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Nicholas Reppas
Global Product Lead Hydrogen, Hitachi Energy Grid Integration
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Nicholas Reppas is a multi-cultural leader with a track record in both business and engineering. With several years of experience in the energy sector, he especially enjoys working cross-functionally in “intrapreneurial” settings and driving visions to reality. Nicholas believes in the power of innovation and collaboration. He engages passionate individuals, bridging the gap between technology, environment and business with the clear mission of supporting the green transition.

Currently, Nicholas leads the scale-up of the hydrogen portfolio at Hitachi Energy, including power-to-gas and gas-to-power, which are both vital to decarbonizing hard-to-abate sectors. In addition, he serves as the Sustainability Lead for the Global Product Group Grid & Power Quality Solutions and Service.

You can connect with him on LinkedIn.