Abstract
The permanent introduction of green hydrogen into the energy economy would require that a discriminating selection be made of its use in the sectors where its value is optimal in terms of relative cost and life cycle reduction in carbon dioxide emissions. Consequently, hydrogen can be used as an energy storage medium when intermittent wind and solar power exceed certain penetration in the grid, likely above 40%, and in road transportation right away, to begin displacing gasoline and diesel fuels. To this end, the proposed approach is to utilize current technologies represented by PHEV in light-duty and HEV in heavy-duty vehicles, where a high-performance internal combustion engine is used with a fuel comprised of 15–20% green hydrogen and 85–89% green methane depending on vehicle type. This fuel, designated as RHYME, takes advantage of the best attributes of hydrogen and methane, results in lower life cycle carbon dioxide emissions than BEVs or FCEVs and offers a cost-effective and pragmatic approach, both locally as well as globally, in establishing hydrogen as part of the energy economy over the next ten to thirty years.
Highlights
The notion of hydrogen as a chemical fuel, energy carrier and energy storage medium appears to have started just about 200 years ago [1]
The competing technologies in road transportation consist of: (a) conventional vehicle (CV) with internal combustion engine (ICE) and a hydrocarbon fuel, typically gasoline, diesel or natural gas, representing the majority of vehicles on the road today; (b) hybrid electric vehicle (HEV) combining an ICE fueled by a hydrocarbon fuel with an electric motor and batteries charged by the ICE; (c) plug-in hybrid electric vehicle (PHEV), which is similar to the HEV with the added feature that batteries can be charged externally; (d) battery electric vehicle (BEV) with only an electric motor and batteries charged externally; and (e) fuel cell electric vehicles (FCEV) with an electric motor powered by a fuel cell utilizing onboard stored hydrogen fuel
The green fuel of choice should be a combination of green or renewable hydrogen and of green methane choice to reduce the life cycle emission of carbon dioxide and compete economically with fossils fuels and their cleaner derivatives, as we examine
Summary
The notion of hydrogen as a chemical fuel, energy carrier and energy storage medium appears to have started just about 200 years ago [1]. EU hydrogen strategy is lower to reduce figure given thatcumulatively the price of natural in the is two to three times thanthe that current cost of electrolysis units from EUR900/kW to EUR 450/kW by 2030 [20] This will require increasing the 2020 capacity by almost a factor of ten in this decade. In analogy to the hydrogen classification, we can distinguish grey methane, which is essentially fossil natural gas, blue methane, which is methane with some capture of carbon dioxide, and green methane, which is biomethane produced via the anaerobic digestion of organic wastes and energy crops. The utilization of the carbon dioxide in the biogas with green hydrogen to produce more green methane results in an overall conversion efficiency over 100% because of wind power use and in even more negative carbon dioxide emissions.
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