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Driven by decarbonization, energy efficiency standards, and lucrative incentives, home and building owners are installing high-efficiency electric heating and cooling equipment. When powered by renewable electricity, these electric HVAC systems have the potential to decarbonize heating and cooling. However, the electric utility infrastructure in many areas is not yet scaled to fully support this level of electrification, especially during peak times of the year, and only 20% of U.S. electricity is produced by renewable energy.

While most electric HVAC systems are designed to draw power from the grid, not all of them have to. There are other net-zero fuels that can power electric HVAC systems, including green hydrogen. Hydrogen is a promising alternative fuel that is positioned to help decarbonize several fossil fuel-heavy sectors. Likewise, hydrogen presents a bold new opportunity for HVAC system manufacturers and contractors who are looking for ways to minimize greenhouse gas (GHG) emissions from their systems.

Transforming HVAC technology to incorporate hydrogen as a fuel and power source will require new investments in technology. This technology must be engineered and tested to deliver hydrogen safely and efficiently to industrial and commercial locations using HVAC systems.

OVERCOMING THE LIMITATIONS OF THE ELECTRICITY GRID

Today’s HVAC systems still rely heavily on fossil fuels — either directly via natural gas or through electric power from power plants that are still mostly fossil fuel-powered. In many regions, power for heat pumps comes from the grid, which is still heavily dependent on fossil fuel sources. During extreme temperatures, urban areas can see an increase in the use of HVAC systems, which can stress local electric grids and increase the amount of greenhouse gases that are released into the atmosphere.

Typical heat pump operation in the northernmost regions of the country is not efficient during the coldest times of the year due to the reliance on heat transfer between large temperature differences. Electric HVAC systems are also prone to faulty breakers, overheating, and extended troubleshooting to solve issues. All these factors can be at odds with or slow HVAC decarbonization efforts.

In comparison, hydrogen fuel cells are independent of the electricity grid and generate zero carbon emissions when combusted. While there is no single solution to immediately and easily transform HVAC systems from dependence on GHGs to hydrogen, expanding hydrogen fuel cells to generate electricity for electric heat pumps is an HVAC technology with positive potential. Using hydrogen fuel cells to power heat pumps can alleviate the strain on the electric power grid. Especially when there are surges in grid demand, hydrogen fuel cells may also be a more efficient solution compared to large-scale grid battery storage. In this way, hydrogen can help the industry solve these challenges and accelerate the pace of decarbonization.

What’s more, hydrogen fuel cells can offer higher efficiency levels compared to traditional HVAC systems, which can further reduce energy consumption and utility costs. Hydrogen fuel cells can convert fuel energy more directly to electrical energy than combustion-based power systems can, requiring less fuel to do the same work.

IMPROVING BURNER AND BOILER EFFICIENCY AND OVERALL EQUIPMENT EFFECTIVENESS 

In addition to helping decarbonize heat pumps, hydrogen can also help improve overall equipment effectiveness (OEE) of burners and boilers.

Boilers: Hydrogen offers significant potential as a clean-burning fuel to generate heat used in thermal water heating applications. Combusting hydrogen generates zero greenhouse gases (although the reaction does produce nitrous oxide, which is subject to emissions controls in many locations).

Hydrogen combustion combined with condensing technology can provide efficient thermal water heating. For example, there are companies that have developed residential tankless water heaters that can operate with up to 30% blending of hydrogen with natural gas, and one has even launched a pilot system that uses 100% to heat water.

Another firm is developing a residential fuel cell boiler, generating heat and electricity simultaneously to meet both space heating and hot water demands. This application can be effective for commercial and industrial applications as well as residential, if properly and efficiently scaled.

Supplying both heat and electricity from one reaction without generating GHG emissions provides optimal energy utilization. Industrial-scale fuel cells can reduce demand on the electric power grid — which can be very useful for large commercial applications such as data centers, semiconductor fabs, and factories.

Burners: Heating equipment, such as multi-burner industrial furnaces, can also be designed to use hydrogen fuel. To improve combustion efficiency in hydrogen-powered equipment, there are advantages to closely matching the heat load in furnaces to the actual demand of the system. Frequent start-ups and shutdowns of burner systems lead to unnecessary fuel waste and excessive emissions. By installing valve systems with higher turndown ratios and flow factors, it is possible to significantly reduce on/off cycles and increase fuel efficiency. Implementing these valves makes good environmental sense, helps control fuel costs, and enables facilities to comply with increasing regulations limiting nitrous oxide emissions.

Pulse firing is one way to provide a smarter and more sophisticated way to improve heat distribution in hydrogen-fueled HVAC heating equipment. Consider multiple burners placed strategically on equipment based on the anticipated heat demands. Rather than have all burners operate at the same flow rate to reach the desired heat levels, burners “pulse” intermittently in a highly controlled fashion, either by firing on and off or ranging between low and high fire sequences. (Fig. 1) It is another technique that, with the proper valve technology, helps maximize boiler OEE and efficient use of hydrogen fuel sources.

Figure 1

A THEORICAL EXAMPLE: Pulse firing can help match fuel use to demand, maximizing boiler OEE and efficient use of hydrogen fuel sources. (Courtesy of Emerson)

It’s important that OEMs that manufacture HVAC systems using hydrogen and seek to gain the advantages of pulse firing properly select key components, such as safety shut-off valves, sensors, and controllers, to achieve precise and safe hydrogen combustion that yields more sustainable combustion.

Leading industry suppliers now offer motorized safety shut-off valves that can either stop the flow of fuel or provide high/low/off control to provide a range of flow rates. This new generation of safety shut-off valves has been engineered to provide optimized curvature, volumes, and capacities that support higher flow rates.

Higher flow rates allow for a higher turndown ratio, so burners in a pulse firing configuration can operate with greater flexibility, generate greater heat output — reducing the number of burner shutdowns and restarts — and, ultimately, help reach targeted goals of fuel consumption and emissions reduction.

As hydrogen is a light, extremely small molecule that can be explosive in certain conditions, it’s critical to select components like safety shut-off valves that are engineered and tested to provide reliable operation in hydrogen-fueled systems. The hydrogen molecule’s small size makes it easier for it to permeate solid metals, leading to hydrogen embrittlement and increasing the risk of leaks. It’s important to source valves that are tested and satisfy the EN161 standard for safely handling pure hydrogen gas and demonstrate zero leakage over three hours of use.

MAKING THE TRANSITION TO HYDROGEN

Hydrogen is a versatile and scalable fuel. Once it is available in commercially significant quantities, hydrogen can be an effective fuel source for residential, commercial, and industrial HVAC applications.

Many governments and private industries are expanding the renewable hydrogen infrastructure to produce, transport, and distribute green hydrogen to meet future demand and help reach net-zero targets. For instance, in late 2023 the U.S. Department of Energy announced plans to launch the Regional Clean Hydrogen Hubs Program (H2Hubs).^[ii] The $7 billion program will fund the foundation of a national clean hydrogen network to support the hydrogen value chain from production to storage through delivery and end-use.

As the hydrogen economy and infrastructure continue to evolve, stimulating end-use demand by transitioning HVAC systems to hydrogen as a fuel source can help justify future investments in green hydrogen.

ACCELERATING THE PACE OF DECARBONIZATION — TOGETHER

To reduce their carbon footprint and energy bills as well as capitalize on unprecedented incentives, many home and building owners are installing high-efficiency electric HVAC equipment. However, it will take more than one energy source to reach net zero. Green hydrogen can help accelerate the pace of decarbonization by providing the HVAC industry with another clean energy source that generates zero carbon emissions when combusted and reduces reliance on strained electricity grids.

In addition to helping relieve strain on electricity grids, hydrogen fuel cells can offer higher efficiency levels compared to traditional HVAC systems, reducing energy consumption and utility costs. And making hydrogen boiler combustion as efficient as possible can maximize the heat output of a system while helping to reduce nitrous oxide emissions that occur when burning hydrogen — significantly contributing to improving hydrogen-fueled HVAC system OEE.

With greater adoption and funding for infrastructure, hydrogen can be one of the clean fuels the world needs for the future. However, it is important to select hydrogen-specific technology that is rigorously tested and certified for use with hydrogen. To help ensure success, it’s critical to work with a technology partner with extensive experience driving the expansion of green hydrogen applications. This can help HVAC manufacturers solve technology and scale-up challenges and help accelerate a decarbonized future.