Antonino Calabretta

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Summary

This thesis discusses the pathways for hydrogen production and distribution in the mobility sector aiming at assessing pros and cons and particularly energy efficiency and costs features for some of the most relevant technology chains. The discussion is also sustained by specific experimental information provided by the ZeroRegio project (www.zeroregio.com).

Nowadays we are facing two main challenges: ensuring the sourcing of adequate and affordable energy to support economic growth in emerging countries and make a rapid transformation towards a low carbon energy production system. Oil availability would be able to sustain global energy needs for at least next 30 years, but, if current trends in CO 2 emissions will not change, a constant increase of global temperature will also be inevitable with consequences difficult to predict, but probably disastrous.

The possibilities of Hydrogen for fuelling the mobility system have been widely examined. However often the available information have been affected by misleading political interests that are proposing “panacea” solutions to the large and justified social expectations and needs for a  sustainable energy production-consumption system.

Indeed Hydrogen fuel production and utilization may enter in one of the possible pathways for reducing greenhouse gas emissions. However his its possibilities and constrains would need to be clearly assessed. Indeed this analysis concerns some of these points examining main aspects of i) the different ways of hydrogen storage and on-board utilization with PEMFC cars, ii ) the processes for hydrogen production and distribution.

In particular it is noted that the data already available in literarure concerning steam reforming, coal gasification, water electrolysis and biomass pyrolysis are examined and compared with those of a new Eni technology named Short Contact Time – Catalytic Partial Oxidation (SCT-CPO). This last technology can be utilized for large scale H2 production plants but also for small scale units and indeed it has been demonstrated within the framework of the ZeroRegio project for producing H2 within the fences of a multi-fuel Agip station located in the urban area of Mantova.

Some hydrogen pathways from feedstock to filling station were selected. A well-to-thank analysis was made for each selected pathway to estimate costs and total emissions. Results reveal a trade-off between costs and greenhouse emissions. For example, a transition from a fossil-fuel-based transports system towards a system based on hydrogen produced by electrolysis from wind power could enable a reduction in CO2 emissions above 85%. Onthe other hand, hydrogen from renewable sources has an uncompetitive cost. Results show that hydrogen produced with these technologies has a cost from two to six times higher than current cost of gasoline.

The best performances in economic terms are obtained by hydrogen production from fossil fuels. Among examined technologies, steam reforming, SCT-CPO and gasification are the processes by which it's possible to obtain the lowest cost hydrogen. SCT-CPO show very competitive performance: compared to steam reforming, SCT-CPO determines in some contexts a production cost lower of 30% and a significantly smaller size. However, production from fossil fuels generates a level of greenhouse emissions higher than current transport system.

The study shows that the use of liquid hydrogen dramatically increases the total costs of distribution. Moreover, issues related to evaporation and energy expenditure of the cryogenic storage make this technology very disadvantageous.

Production by electrolysis is the best way to reduce emissions and offers a possibility to relocate the plants economically. However, until electricity is not available at low cost from renewable sources, the technology is not a viable solution on large scale.

All data included in the evaluation of emissions and costs are referred to TRIAS project [2007] and Eni.