Germany has undertaken an experiment where wind-generated electricity is used to produce hydrogen which is then inserted into a natural gas pipeline serving an E.ON gas turbine power plant.
Electrolysis is used to produce hydrogen from electricity. The electrolysis unit is manufactured by Hydrogenics, which is promoting its system as a way to store excess electricity from wind, using hydrogen as the storage medium.
Snippet from Periodic Table
This is an interesting approach to ameliorating wind’s tendency to generate electricity at night when it isn’t needed.
It does not, however, solve the problem of wind being unreliable for use on the grid.
It also raises interesting questions about mixing hydrogen with natural gas in the natural gas transmission and distribution systems.
The National Renewable Energy Laboratory (NREL) has published a paper on this issue1.
Assessments need to be divided into two categories, effects on transmission lines and on distribution lines. In both, the paramount issue is safety.
Transmission lines, which can be as large as 4 feet in diameter and operate at pressures as high as 2,000 psi, are generally made from steel. The major danger in this case is hydrogen-induced cracking which can affect durability and pipeline integrity.
Distribution lines primarily use plastic and steel pipe. These pipelines operate at lower pressures where hydrogen-induced embrittlement is not a concern, but where leakage and permeability are concerns. About 60% of distribution lines use plastic pipe.
Permeability for hydrogen in plastic pipe is around 4 times greater than for natural gas. While leakage is not important in open areas, it can be very important when the leakage occurs in confined spaces.
Overall, the NREL report indicates that it’s reasonably safe to mix hydrogen with natural gas in pipelines, if the mixture contains less than 20% hydrogen.
Unanswered in the report is whether appliances, such as stoves, can safely use a mixture of hydrogen and natural gas, containing any percentage of hydrogen.
It also doesn’t address whether insertion into the natural gas pipeline has to be steady, or whether it can be intermittent.
In the report’s Appendix, prepared by the Gas technology Institute (GTI), the risk of using a 20% mixture of hydrogen in service lines is approximately 25% greater than for natural gas alone.
Costs were not addressed in the NREL report.
Adding equipment to a wind farm to convert electricity to hydrogen, adds to the total investment. The value of the hydrogen can’t be great since natural gas, which the hydrogen is replacing, costs less than $4 per thousand cubic feet.
A thorough cost analysis is bound to show that this increases the already high cost of wind-generated electricity, for which the only supposed benefit is to cut CO2 emissions.
Increasing risk by 25% and increasing costs wouldn’t seem to be a good path to go down.
- Blending Hydrogen into Natural Gas Pipeline Networks: A Review of Key Issues. The report is available at http://www.nrel.gov/docs/fy13osti/51995.pdf
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