Arturo Di Filippi
IMAGE LICENSED BY INGRAM PUBLISHING
Meeting ever-increasing capacity demands has emerged as a perceptual challenge for the data center industry. The continuous digitalization of businesses and society necessitates further capacity expansion, despite substantial investments in new infrastructure over the past five years. According to the Dell’Oro Group, investments in hyperscale data centers are projected to double in the next five years.
The rapid growth in data centers poses a significant risk of increasing greenhouse gas emissions associated with their operations. Data centers inherently consume substantial amounts of energy, despite the advancements in efficiency achieved by modern facilities. Data centers consumed an estimated 200 to 250 TWh of energy in 2020 according to the International Energy Agency. A significant portion of this electricity is generated from carbon-based fuels, leading to the generation of Scope 2 emissions for data center operators. Addressing these emissions is crucial for the industry to mitigate its environmental impact.
Data centers have the potential to decrease emissions by enhancing efficiency and optimizing equipment utilization. Although this is a crucial step, it alone cannot fully propel data centers toward their carbon-neutral objectives. Presently, operators rely on power purchase agreements (PPAs) and renewable energy credits to counterbalance their reliance on carbon-intensive fuels. In 2021, the adoption of clean energy PPAs surged by 24% compared to 2020, reaching an unprecedented record of 37.1 GW. This signifies a significant stride toward integrating clean energy sources into the data center industry and underscores the commitment to transitioning toward more eco-friendly practices.
Data center operators recognize that the ultimate objective is to power their facilities with clean energy. However, considering that utility grids in most regions cannot currently offer 100% renewable power to all customers, operators are taking the responsibility to collaborate with their partners to devise innovative solutions that facilitate carbon-free operations. By working hand-in-hand with their stakeholders, operators are actively seeking ways to overcome the limitations of existing grid infrastructure and advance toward more sustainable energy practices within the data center industry.
Implementing local energy generation through renewable sources like solar or wind power may not be suitable for some data center locations. The intermittent nature of renewable energy also poses challenges for data centers that require continuous operation. Nevertheless, there is a promising solution in the form of hydrogen produced using renewable energy. This approach offers a viable option for on-site energy generation at a diverse array of data center sites.
This article explores the latest advancements in fuel cell technology that have resulted in enhanced performance and attractiveness for stationary applications. Specifically, it delves into the emergence of hydrogen-powered fuel cells as a viable alternative to traditional diesel generators for backup power in data centers. Furthermore, it investigates the reasons why fuel cells hold great promise as a long-term solution for achieving zero-carbon primary power in data centers.
Fuel cells may even be utilized for load sharing with the grid in cases when electricity costs are high and partial disconnection from the utility may bring relevant savings on electricity bills, or also for grid support applications. In such cases, fuel cells serve as a reserve power, contributing to supply the load in place of the utility. This not only reduces pressure on the grid but also helps to reduce overall emissions when compared to the current practice of utilizing diesel generators. Moreover, data centers equipped with grid-interactive uninterruptible power supply (UPS) offer numerous opportunities for dynamic grid support and integration with multiple energy sources.
The need to support the power grid is increasing; the progressive rise of renewable energy sources, distributed generation, decarbonization efforts, and increasing energy demand is having a transformative impact on the power generation industry. This shift brings notable challenges to the stability of the grid, primarily due to reduced grid inertia resulting from the decommissioning of large power plants and the intermittent nature of renewables. Consequently, frequency variations caused by temporary imbalances are more frequent and severe.
Conventional frequency regulation methods might not offer a sufficient rapid response to maintain the frequency within defined thresholds. There is a need for faster-acting frequency containment reserves that can adjust electricity demand in real time to address sudden frequency fluctuations. In this evolving energy scenario, data centers and other critical infrastructures play a vital role and are well-suited to provide grid balancing services. These facilities possess assets, like battery energy storage systems that can be harnessed to create new revenue streams, capitalize on cost-saving opportunities, and alleviate strain on grid infrastructure.
A grid-interactive UPS equipped with an appropriately sized energy storage system can effectively fulfill the requirements for frequency containment while facilitating various income-generating services and cost-saving opportunities through demand management.
In the following sections, we first describe the need for dynamic grid support based on the grid industry requirement and how Vertiv UPS systems can provide such a service. Next, we describe the roadmap of data centers with fuel cells as primary and backup power. In fuel cell-powered data centers, UPS again play a critical role. Our perspective on the two technologies for future data centers is provided in the “Conclusions” section.
Europe’s electricity industry value chain has experienced significant transformations over the past decade. Alongside the liberalization of markets both within and across borders, there has been a distinct separation between network operations and electricity suppliers. With this separation, electricity system operators, transmission system operators, and distribution system operators have unique needs and objectives. Consequently, businesses and consumers can unlock new opportunities in the industry by actively engaging in this transformation by offering grid-balancing services and capitalizing on energy storage applications.
Balancing services can uphold grid stability and enable opportunities for revenue generation and energy savings, and thus play a crucial role in ensuring that power supply aligns with actual demand. Participants in grid balancing programs contribute to the decarbonization efforts and the transition toward renewable energy sources. By addressing imbalances associated with renewable power generation, they help secure the electricity supply while actively supporting global sustainability goals.
Supplementary services bring benefits to any electricity-consuming asset connected to a meter. Figure 1 illustrates these devices, referred to as behind the meter (BTM) assets, which differ from front of the meter (FTM) assets in terms of their ultimate destination. In simple terms, BTM refers to the power consumed on site, on the energy user’s side of the meter. Conversely, electricity on the grid or utility side must be measured before reaching the end user and is therefore classified as FTM.
Figure 1. Energy storage market segments within electricity supply chain: FTM versus BTM. T&D: transmission and distribution; C&I: commercial and industrial.
Data center owners have intriguing opportunities to leverage their BTM systems and participate in revenue-generating initiatives, such as fast-frequency response programs. Moreover, BTM assets can effectively reduce electricity costs through effective demand management techniques, like peak shaving and energy arbitrage. By storing energy in batteries, they can balance supply and demand. During periods of low demand or high supply, excess energy can be stored in the batteries and later released during times of high demand or low supply. Alternatively, controlled energy management allows for discharging the battery when electricity prices are high and recharging it when prices are low.
Balancing service programs differ across countries in Europe. Typically, energy markets are regulated by a combination of frequency-based balancing services and slower reserve services (>30-min response time). The speed of response required to participate in the frequency control program through grid services is determined by the electricity market and energy providers.
In the present scenario, there is a growing requirement for faster-reacting frequency response reserves to swiftly address sudden frequency fluctuations and make rapid adjustments to electricity demand. These reserves encompass primary reserves, which can respond within seconds, as well as secondary reserves that can adapt within minutes. Demand and response services can be roughly classified into two categories to target frequency control (fast frequency response) and demand management.
Fast frequency response programs leverage UPS battery storage systems to efficiently store and quickly release energy in accordance with the following guidelines:
Demand management, also referred to as energy arbitrage or peak shaving, which involves reducing electricity consumption during periods of scarcity or high energy costs, offers an alternative strategy for aligning electricity supply and demand. By actively managing and curbing electricity demand when it is most needed or expensive, demand management helps optimize resource allocation and mitigate the strain on the grid.
There are two primary types of programs used to implement demand management strategies:
Vertiv empowers data center owners by enabling UPS grid services that exhibit enhanced speed of response to frequency variations and external commands. This capability enables data centers to actively participate in demand and response programs tailored to their needs, such as fast frequency response and peak shaving. By leveraging Vertiv’s solutions, data center owners can contribute to grid stability and capitalize on the benefits of these specific programs.
To implement grid support features on the Vertiv™ Liebert® EXL S1, the integration of an external controller is necessary. This controller’s primary role is to detect grid frequency variations, such as underfrequency (49.8 Hz) or overfrequency (50.2 Hz). It then communicates with the UPS, sending commands to adjust its input power accordingly. The UPS control system is specifically designed to respond rapidly to these commands, meaning that the system reaches the specified power set point within a total response time of less than 500 ms.
The dynamic grid support functionalities of the Vertiv Liebert EXL S1 are compatible with both valve-regulated lead–acid and lithium-ion batteries (LIB). However, for grid applications, LIBs are generally preferred. They offer advantages, such as a higher number of cycles, quick charge and discharge capabilities, and the ability to be monitored and controlled through a battery monitoring system (BMS). The BMS facilitates the exchange of information between the battery and the UPS, further enhancing the overall performance and control of the system.
To actively participate in auxiliary services, a grid-interactive UPS should possess the ability to modulate its power demand while providing sufficient battery runtime to back up the critical load. This backup runtime allows for a smooth transition to generators in case of a utility failure.
When the external controller detects variations in grid frequency, it issues commands to the UPS. These commands direct the UPS to respond to both positive and negative regulation by charging or discharging the batteries within their operational limits. This dynamic battery adjustment enables the UPS to effectively follow the frequency variation request, thereby contributing to grid stability and additional service requirements.
The UPS manages the input power to achieve specific targets or fulfill certain services by operating in different modes. These modes optimize performance and enable the UPS to align with the desired objectives:
Figure 2. Standard UPS operation: considering 800-kW load, full power is coming from the utility grid.
Figure 3. Full disconnection: considering 800-kW load; full power is coming from the batteries.
Figure 4. Partial disconnection: considering 800-kW load, 600 kW are taken from utility grid, through the rectifier input, and 200 kW from the battery.
Figure 5. Recharge mode: considering 800-kW load, 1,000 kW are taken from the utility grid, through the rectifier input, and 200 kW are used to charge the batteries.
By adapting its response according to predefined frequency and voltage thresholds, the Liebert® EXL S1 UPS offers versatile support for dynamic and static frequency. Additionally, the UPS facilitates demand management by adjusting the input power in response to commands related to demand control flexibility.
Dynamic regulation is performed via Modbus with dynamic power response based on frequency deviation.
It is important to note that the primary function of the UPS is always to safeguard the critical load and enable uninterrupted runtime in all conditions. This objective holds the highest priority, prompting the control system to exit or pause the dynamic grid support mode when operating conditions deviate from specifications or pose an increased risk.
Unlike batteries, fuel cells do not store energy but generate electrical power through chemical reactions involving a fuel source and oxygen. Hydrogen and natural gas are commonly used as fuel sources for fuel cells. When hydrogen is utilized, the only byproducts produced are water and heat, making it a clean option. On the other hand, natural gas-powered fuel cells benefit from well-established production and distribution infrastructure, allowing a continuous supply in many regions. Although natural gas fuel cells are relatively clean, they do generate some greenhouse gas emissions. Some fuel cell manufacturers are adapting their designs to enhance fuel flexibility for various applications using natural gas.
In contrast, hydrogen production capacity is more limited and requires a robust distribution network. However, efforts are underway to address these limitations. Hydrogen fuel cells have the potential to support carbon-neutral operations, depending on the production method of hydrogen.
Currently, the majority of hydrogen production relies on fossil fuels through processes like steam-reforming natural gas, partial oxidation of heavier hydrocarbons, or coal gasification. This type of hydrogen, known as gray hydrogen, carries an environmental footprint due to its association with fossil fuels. The emissions produced during these processes should be considered when determining the overall environmental impact of fuel cell applications. Alternatively, hydrogen can be produced using renewable energy through water electrolysis, resulting in “green hydrogen” that doesn’t generate greenhouse gas emissions during production. By utilizing green hydrogen to power fuel cells, zero-carbon on-site energy generation becomes achievable.
However, the absence of an extensive hydrogen distribution network poses challenges for using hydrogen fuel cells in stationary power applications. In practical terms, hydrogen would need to be transported from production sites to the locations where it is required. This limits the immediate feasibility of utilizing hydrogen fuel cells for primary data center power. Nonetheless, for backup power purposes, storing enough hydrogen on site can sustain continuous operation for up to 48 h in large data centers. Thus, hydrogen fuel cells offer a viable solution for backup power while advancements in hydrogen distribution networks continue to progress.
Proton exchange membrane (PEM) fuel cells utilize hydrogen as their fuel source and incorporate a solid polymer electrolyte. These fuel cells have a unique characteristic of delivering high power density, allowing for a smaller physical footprint compared to other types of fuel cells. They operate at relatively low temperatures, with a maximum range of up to 80 °C (176 °F). One advantage of PEM fuel cells is that they do not require the high temperatures typically needed by other fuel cell technologies, enabling quick startup times. This quality makes them well-suited for backup power applications. However, it’s important to note that PEM fuel cells require a noble-metal catalyst, such as platinum, to facilitate the separation of hydrogen’s electrons and protons. This feature necessitates special safety precautions due to the potential hazards associated with handling such materials.
Solid oxide fuel cells (SOFC) employ a ceramic compound as the electrolyte. These fuel cells operate at considerably higher temperatures, typically ranging from 800 to 900 °C (1,472 to 1,652 °F), which eliminates the need for precious-metal catalysts. However, this high operating temperature results in longer startup and shutdown times, making them more suitable for continuous duty applications rather than intermittent use. SOFCs offer greater flexibility in terms of input fuel, with natural gas being the primary choice, although certain designs can also accommodate pure hydrogen. One notable advantage of SOFCs is their high operating efficiency, which can be further enhanced by capturing and utilizing the heat generated during operation. Given their elevated operating temperature, significant thermal shielding is necessary to retain heat and ensure personnel safety. It is worth noting that the thermal stress endured by the cell materials in an SOFC system can limit the number of on/off cycles over its lifetime.
Considering the existing advancements in fuel cell technology and the continuous evolution of critical power solutions in data centers, it is conceivable to imagine a future where fuel cells play a pivotal role in providing clean and reliable primary and backup power. Presently, PEM fuel cells are well-suited for backup power applications, while SOFCs are better suited for primary power generation. However, in cases where not all SOFCs can be reconfigured to operate with pure hydrogen, there is potential for PEM fuel cells to serve as primary power sources.
Vertiv has undertaken thorough research to explore the utilization of fuel cells in data centers and is actively engaged in multiple pilot projects (Figure 6). These initiatives aim to ensure that fuel cells meet the stringent requirements of data centers in terms of reliability and performance.
Figure 6. The path to CO2 free operation. FC: fuel cell.
The operators of diesel generators are currently being prompted to reduce reliance on these systems as they contribute significantly to Scope 1 emissions in data centers. One potential solution is to enhance battery runtimes, enabling the battery system to support longer outage durations. This approach can be effective for operators requiring outage protection of 30 min or less. However, for data centers that need to remain operational during outages lasting 24 to 48 h to meet service level agreements and user expectations, relying solely on batteries becomes impractical due to the substantial size of the required battery system.
Emerging technologies, such as linear generators, are being explored as potential solutions for the future. On the other hand, fuel cells, which are already utilized in various applications, such as transportation, military, and marine sectors, present a more established and proven solution. Moreover, the costs associated with fuel cells have significantly decreased in the past five years, with this downward trend expected to continue in the future.
However, it is worth noting that while fuel cells are employed in diverse applications at present, their implementation in large stationary power applications like data centers presents certain technical challenges that need to be addressed. As of now, the adoption of fuel cells in data centers remains limited, but ongoing advancements aim to overcome these obstacles and unlock their potential for this specific use case.
UPS systems are employed to address the relatively slow response of fuel cells to load changes and dissipate excess energy. By configuring the fuel cells and the UPS system’s LIBs in parallel, the fuel cells can store excess energy in the battery system resulting from load changes.
With this configuration, there is no need to transfer the load to the backup power source during load changes. Instead, when an outage occurs, the system transfers the load to the batteries. The fuel cells continuously charge the batteries until the stored hydrogen is depleted. Additionally, UPS energy management capabilities enhance the value of fuel cells by enabling peak shaving and other grid services.
Here are the key components of a data center backup power solution capable of replacing a diesel generator (Figure 7):
Figure 7. In this application, fuel cells serve as the main source of power with the grid providing backup power in conjunction with LIBs.
Due to the current limitations surrounding hydrogen distribution, the transition toward utilizing fuels cells as a primary, zero-carbon power source for data centers takes longer compared to their application in backup power scenarios. However, significant progress is underway to address these challenges, and in the meantime, while hydrogen distribution infrastructure is expanded, natural gas-powered fuel cells, which offer emission reduction benefits and other advantages, can serve as an interim solution.
As part of this effort, Vertiv is actively involved in a project funded by the Fuel Cells and Hydrogen 2 Joint Undertaking, supported by the European Union’s Horizon 2020 research and innovation program, Hydrogen Europe, and Hydrogen Europe Research. This initiative aims to pilot the use of natural gas-powered SOFCs as the primary power source for hyperlocal edge data centers. The project’s objective is to minimize the environmental impact of these data centers and promote the development of a comprehensive open standard for fuel cell applications within the data center industry.
In this particular application, SOFCs function as the primary power source, while the grid provides backup power in conjunction with LIBs. The UPS will eventually assume control over the interface between the batteries and fuel cells. It will manage fuel cell set points and handle excess power resulting from load changes or transients. Looking ahead, the UPS could evolve into an energy manager, coordinating multiple power sources, such as the utility grid, fuel cells, and even a backup generator if available. It will continuously assess and select the optimal power source based on factors like cost, reliability, and other considerations, while ensuring smooth transitions between sources.
Although this project focuses on hyperlocal data centers, the knowledge gained from it is expected to contribute to advancements in utilizing natural gas-powered SOFCs as the primary power source for larger data centers. There is a potential for transitioning these SOFCs to hydrogen power, as its cost decreases and availability increases, enabling carbon-neutral operation and further enhancing sustainability in the data center industry.
Looking at it technically, when an intelligent UPS system effectively manages fuel cells, they possess the necessary performance qualities to offer clean and dependable backup power for data centers. Considering ongoing pilot projects, it is not unreasonable to anticipate the commercialization of PEM fuel cell solutions for data center backup power within the next few years.
However, these solutions must also demonstrate cost-effectiveness to gain widespread industry support. It is not mandatory for them to be cheaper than diesel generators since there is tangible value in their ability to reduce Scope 1 emissions, and this value may grow in the future if the cost of carbon rises. Additionally, fuel cells bring added value through new capabilities like peak shaving.
At present, it is challenging to estimate the lifetime costs of a commercialized PEM fuel cell solution due to the dynamic nature of fuel cell module and hydrogen fuel costs, which are expected to decrease in the upcoming years.
The United States government is making a significant effort to reduce hydrogen costs through the Department of Energy (DOE) Earthshots Initiative. This initiative, launched in June 2021, aims to bring down the cost of clean hydrogen to US$1/kg by the end of the decade. Several key economic factors could influence the adoption of fuel cells as backup power sources in data centers:
Initially, the deployment of fuel cells to replace or supplement diesel generators will likely be driven by hyperscale operators who are at the forefront of carbon reduction efforts. However, as fuel cell technology advances, they will become an increasingly appealing solution for various types of data centers.
The integration of fuel cells and dynamic grid support in the Vertiv™ Liebert® EXL S1 will enable energy-intensive industries to proactively utilize UPS systems while maintaining the critical load protection function of the UPS intact. There is a need for new energy storage services to achieve carbon reduction goals, generate revenue, and reduce energy costs as the intermittent nature of renewable energy poses challenges to traditional power generation. By addressing these requirements, grid infrastructure constraints can be alleviated, and the utilization of renewable power sources can be increased.
Vertiv offers a comprehensive integrated solution that includes the grid interactive UPS with an external controller and energy storage, catering to end users as well as aggregator/energy service providers.
Moreover, to facilitate sustained growth while simultaneously minimizing their environmental impact, data center operators are actively seeking alternatives to carbon-based grid power and diesel generators.
Among the most promising solutions, fuel cells emerge as a key technology to assist operators in achieving their carbon-neutral objectives. Specifically, PEM fuel cells utilizing clean hydrogen demonstrate the ability to eliminate CO2 emissions during regular generator maintenance and power outages. Currently, PEM fuel cells are undergoing preliminary testing for this application and are expected to become commercially available within the next few years.
Additionally, natural gas-powered fuel cells are being piloted as primary power sources for edge data centers, contributing to the advancement of this technology in larger data centers as well.
In terms of cost, fuel cells are presently not on par with diesel generators or grid power. However, there is optimism as the costs of essential components and hydrogen fuel are anticipated to decrease in the near future, rendering fuel cells a practical and economically viable power solution for data centers.
Vertiv is spearheading the advancement of fuel cell technology, actively targeting critical infrastructure solutions that facilitate the efficient utilization of fuel cells while providing support for supplementary functionalities, such as peak shaving, frequency regulation, and integration of renewable energy sources.
“Evaluating the potential of fuel cells for data center power.” Vertiv. Accessed: Jul. 12, 2023. [Online] . Available: http://www.vertiv.com/en-us/about/news-and-insights/articles/white-papers/fuel-cells-for-data-centers/
“Powering the data center with hydrogen fuel cells.” Vertiv. Accessed: Jul. 12, 2023. [Online] . Available: http://www.vertiv.com/en-us/campaigns/powering-the-data-center-with-hydrogen-fuel-cells/
Arturo Di Filippi (Arturo.Difilippi@Vertiv.com) is with Vertiv, 40121 Bologna, Italy.
Digital Object Identifier 10.1109/MELE.2023.3291254
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