CH-24-C035 - Is the Heating Industry Hydrogen-Ready?; A Meta-Analysis of Hydrogen Impact Assessments on Combustion Equipment in Buildings

Throughout the U.S. and Canada, there are an increasing array of utility demonstrations of hydrogen (H2)-blended natural gas (≤ 20% by vol.) and studies examining impacts of higher blends (20%+ by vol.), involving residential, commercial, & industrial end users, providing near term emissions reductions and operational experience as the costs of H2 generation, storage, and distribution decline. Plans for H2 distribution networks and microgrids are increasing in quantity and scale. As compared to methane (natural gas), blending H2 affects a range of fuel gas properties that are well-documented, for example, a 20% H2 blend into methane can yield a 17% lower volumetric density, 14% lower higher heating value, 15% lower combustion air requirement, 5% lower Wobbe Index, a 15% faster laminar flame speed, a 7% lower CO2 emissions, and lower/greater NOx emission rate depending on burner design and what compensations are employed. Also, H2-blending may affect leakage rates within or upstream of existing equipment. While some information about the gas quality can help predict the equipment’s response, such as the heating capacity of certain equipment driven by shifts in fuel Wobbe Index, the response of specific equipment to shifts in gas quality concerning safety, efficiency, emissions, and product lifetime are best understood through in-situ testing. Driven by the broader push towards decarbonization and the impetus to expand the end use demand of H2 as a decarbonization vector, many researchers have studied the impact of various H2/natural gas blends on a wide range of combustion equipment, including forced-air heating (e.g. warm-air central furnaces, unit heaters), boilers (steam and hot water), water heaters (storage and tankless-type), and other heating equipment (e.g. radiant heaters). Over the past three to five years, the output of test data on these equipment with H2 blends has accelerated, and this meta-analysis aggregates the findings of these results from industry, universities, government, and international groups (focusing on North American-type equipment). Aggregated data concerning emissions (NOx, CO), efficiency, operational safety (e.g. flashback), leakage enhancement, and material impacts are summarized across these recent studies, leading to broad themes concerning increasing H2 percentages in fuels, equipment types, and other factors.