As key players in the utility industry begin piloting hydrogen projects to meet their carbon reduction goals, one of the main questions consumers are asking is how the shift to hydrogen – natural gas blends will affect their home appliances. Today, consumers use natural gas to prepare their meals and heat their homes. The main appliances in a residential home utilizing natural gas are:
- Cooking appliances such as ovens, grills, stoves
- Air conditioners
- Refrigerators and freezers
- Water Heaters
Citation: Bolt, 2023
Will these appliances be able to sustain the hydrogen transition, or will a blend of natural gas and hydrogen require consumers to replace their appliances? This question along with the pros and cons of each are being evaluated extensively.
Performance of Appliances
Recent studies have proven current natural gas appliances are sustainable for a hydrogen blend of up to 20% (Font, Kernan, Widder, 2023). Specifically, studies conducted by the Canada Standards Association (CSA) proved appliances to still be high performing with 5% and 15% hydrogen blends. Once the hydrogen blend surpasses 20%, the performance of an appliance begins to deteriorate and cause safety concerns, which would require shifting to hydrogen appliances.
There are multiple parameters for determining the performance of a residential appliance such as ignition, burner operating characteristics (BOC), temperature rise, combustion, flue loss, and condensation (Suchovsky, Ericksen, Williams, Nikolic, 2021). However, these parameters proved to have the most variation when testing with hydrogen blends, causing concern (Font, Kernan, Widder, 2023) :
Hydrogen has a higher combustion rate than natural gas by 4.25 m/s, meaning it “requires less oxygen than burning the equivalent amount of natural gas” (Guarco, Langstine, Turner). The combustion of hydrogen releases water and no carbon dioxide; moreover, it also will require less oxygen than a standard combustion reaction resulting in surrounding air being heated to a greater degree than natural gas. Due to the higher heated air content, the performance of the appliance suffered since the temperature of the flame is affected by the higher air temperature and combustion reaction. Studies have shown “the effect on tested appliance efficiency is minimal, varying only 1 to 1.5% for 30% hydrogen blend in natural gas”, leading to concerns with 100% hydrogen or higher blends (Font, Kernan, Widder, 2023).
Like the increased rate of combustion, hydrogen also produces more condensation in comparison to natural gas. This difference becomes a concern especially in reference to dryers. Condensation in dryers can cause a performance issue due to additional moisture build-up, creating the need for equipment upgrades. In appliances other than dryers, condensation is a point of concern due to necessary improvements needed to ventilate the additional moisture, if the ventilation system is not already established. The NEEA, Hydrogen-Ready Appliances Assessment Report, determined that a 20% hydrogen blend will cause an 8% increase in condensation.
The color of a hydrogen flame becomes relevant with appliances such as hearths and stove tops. Many consumers use the flame as a detection for safety and strength. A flame can notify the consumer whether the appliance is continually heating and ultimately, if the appliance is still on. With a hydrogen flame, as the hydrogen blend increases, the flame becomes more difficult to see, in addition to being odorless, resulting in safety concerns (Kiwa, 2016 ). Figure 1 shows the variation of flame colors for different variations of hydrogen blends. Likewise, many appliances use ionization sensors to detect flames or thermoelectric flame failure devices. Due to the inability of these sensors to detect hydrocarbon combustion, many safety features of appliances will begin to fail at higher hydrogen blends and may cause gas build up, leading to safety concerns (Font, Kernan, Widder, 2023).
Hydrogen is slowly beginning to be blended with natural gas and entering residential homes. With this transition comes concern of how the blend will affect consumer appliances and whether it will be a cause for homes to upgrade to new equipment. Current studies show that today’s equipment feasibly sustains a hydrogen blend of up to 20%. However, blends of higher than 20%, may compromise performance and safety of existing gas appliances, requiring an upgrade to 100% hydrogen appliances.