Power and Compression Analysis of Power-To-Gas Implementations in Natural Gas Pipelines With Up to 100% Hydrogen Concentration

Abstract

The introduction of hydrogen or synthetic natural gas produced from renewable electricity into gas pipelines is being considered to enable decarbonization and energy storage. Prior published studies show that hydrogen concentrations over 20–30% are likely to require significant infrastructure modifications and that significant concentrations of hydrogen will decrease energy transport capacity and/or reduce transport efficiency due to higher compression work. A comparative analysis of four power-to-gas implementations utilizing alkaline electrolysis, steam methane reforming, and catalytic methanation at hydrogen concentrations from 0–100% is performed in order to quantify production and transport power requirements utilizing pipeline or electrical transport. The pipeline transport analysis evaluates the pipeline transport capacity, efficiency, and emissions at various hydrogen concentrations and their sensitivity to pipeline diameter and compressor station spacing. The results show that production costs for hydrogen and synthetic natural gas dominate the overall energy requirement, requiring more power to create product than will be delivered for end use. Pipeline transport power requirements also increase by a maximum factor of 6–8 depending on surface roughness at high hydrogen percentages, but pipeline transport losses are less than electrical transmission losses in all cases. The increased pipeline compression power increases CO2 emissions along the pipeline up to a peak value of 240% relative to pure methane at a mole fraction of 65% hydrogen, above which CO2 emissions reduce. An analysis of pipeline compression conditions shows that flow requirements for all cases exceed the capabilities of reciprocating compressors but are mostly within the capabilities of centrifugal compressors, although multiple bodies may be required at hydrogen concentrations exceeding approximately 40–85%.

Hydrogen Blending into Natural Gas Pipeline Infrastructure: Review of the State of Technology

“…It is important to note, however, that although pressure drop reduces with increasing hydrogen concentration at constant volumetric flow rate, total energy flow rate also reduces due to the lower volumetric energy density of hydrogen. The studies found that for a constant energy flow rate, pressure drop increases with increasing hydrogen content until an apex at 70%-85% hydrogen by volume, after which pressure drop decreases (Allison et al 2021). These results are consistent with those found by Bainier and Kurz (2019), which illustrate that with fixed pressure drop, volumetric flow increases with hydrogen concentration.…”

“…To compensate for the reduction in transmission capacity, pipeline operators can increase gas flow rates to maintain consistent energy delivery. Increasing flow rates, however, results in increased pressure drops along the pipeline, which could in turn require higher pipeline pressure to maintain the delivery pressure required at city gates and by other end-users (Allison et al 2021). The ability to maintain energy transmission capacity will depend on equipment and network constraints.…”

“…Pressure drop is a function of a variety of pipeline properties and conditions that change with gas composition, including fluid flow rate, gas density, friction factor, and average gas temperature. Several prior publications have reported on the impact of hydrogen on pipeline pressure drop on either a constant volumetric flow rate (Blacharski et al 2016;Witkowski et al 2018;Kuczyński et al 2019), constant energy transmission basis (Allison et al 2021) or both (Schouten 2004). Blacharski et al (2016) and Witkowski et al (2018) studied the impact of different blending compositions on transmission pipeline pressure drop.…”