WP3 is the core of the project with its extensive test campaign
Short term tests are carried out to observe how appliances react in the short term (few minutes to few hours) on different H2NG mixtures.
The first issue observed is a limited number of appliances whose design makes them sensitive to delayed ignition. This will happen from 15% H2 and maybe already at 10% H2 for some segments. There is probably no better solution but replacing those appliances or changing some components (retrofit). Adjustment of appliances could worsen the delayed ignition issue.
The second issue that may happen starting from 20% or maybe below, is high CO production with premix appliances that can be adjusted on-site. The most critical case is when they are adjusted at a time when there is H2 in the blend and used with a rich gas without H2 later. Luckily, this issue or at least part of it can easily be solved with adjusting with O2 instead of CO2 or through other proposals listed in THyGA deliverable D5.2.
The third issue is Flashback. It generally occurs for 30% H2 or more, appearing first on partially premix appliances when increasing the H2 %.
The impact on NOx emissions is positive for the vast majority of the tested appliances (decrease of measured emissions). Note that this conclusion only applies to the test done under conditions simulating a real domestic or commercial installation, where no changes are made on appliances when the gas quality changes
The impact on appliance efficiency is generally very modest and can be either positive or negative (several competing phenomena, decrease of Wobbe Index, of heat input, more condensation in some cases…).
Long term test were carried out to observe possible appliances alterations (performances or physical alteration) in the long term (few month) with a blend of natural gas with 30% hydrogen. Appliances run through an accelerated test program, amounting to more than 3000 testing hours for each of the 5 boilers and more than 2500 testing hours for each of the 2 cookers (~20 000 hours in total). The percentage of hydrogen tested was 30%. The tests carried out have not shown any particular impact on the performances and safe operation of the appliances. The signs of wear and tear that were observed for boilers would have also been observed using pure natural gas and there is no visible additional impact due to the presence of hydrogen.
Leakage tests aimed at observing possible leakages on components taken from existing gas line within the building from Germany, Denmark, Belgium and France and tested with a mixture 60%H2+40%CH4+, at 30mbar. It can be concluded that in the tested conditions, and with gas lines properly installed, the leakage rates will be below the current admissible standard rates both for gas line and appliances as well. At those low pressures, no differences between leakage rates in air, He and in the H2NG blend was observed. Furthermore, for the lines able to hold the pressure for longer, after about 200 hours of test, no deterioration of the components or loss of tightness was observed.
WP4 worked on the identification of existing regulatory and standardization work dealing with certification of natural gas appliances and the ways to deal with hydrogen admixtures within this framework. Main conclusions are in D4.3
Part I of the report covers considerations regarding test gases for assessing combustion related risks of supply with gaseous fuels of the second family (i.e. natural gases) blended with hydrogen of which the concentration may vary between 0 and a maximum hydrogen concentration X (called “X% H2NG”) to gas appliances within the scope of the Regulation (EU) n°2016/426. If relevant, a specific view is given on 20% H2NG as this is often put forward as a meaningful limit if hydrogen injection is considered.
Part II covers risks to be considered when revising existing gas appliance standards for H2NG supply. It gives an overview of risks impacted by the presence of hydrogen linked to the corresponding essential requirement stated in annex I of the GAR. It serves as guide for the concerned CEN TCs for assessing the existing appliance standard(s) and/or for elaborating new appliance standards in their scope.
WP5 worked on the identification of mitigation measures to allow higher rates of hydrogen for appliances, the main take-away from the WP are based on adjustment risks and safety check
Especially, field adjustment of gas appliances can be an issue if current practices are not updated. For some appliances, when they are adjusted with a low Wobbe Index gas mixed with 20% hydrogen and used afterwards with a high Wobbe Index gas without hydrogen, it can produce high amounts of CO emissions. Several mitigation solutions have been studied
