Abstract
Solar reforming of biogas or biomethane represents an example hydrogen production from the combination of renewable sources such as biomass and solar energy. Thanks to its relatively low-cost and flexibility, solar-reforming can represent a complementary source of hydrogen where/when the demand exceeds the green hydrogen availability from water electrolysis powered by PV or wind. Molten salts can be used as heat transfer fluid and heat storage medium in solar-driven steam reforming. The main units of the process have been developed at the pilot scale and experimentally tested in a molten salt experimental loop at ENEA-Casaccia research center: a molten salt heater and a molten salt membrane reformer. After experimental validation, techno-economic studies have been carried out to assess the solar reforming technology on commercial scale and exploitation opportunities have been analysed.
Highlights
The growing interest on hydrogen requires evaluating all possible conversion processes for its production.Technologies developed so far allow hydrogen production from renewable sources using electrochemical, photochemical, thermochemical or biochemical pathways; there are opportunities for further improvement of green hydrogen production in terms of costs reduction and efficiency in the deployment of primary sources [1].Besides water-splitting by electrolysis driven by renewable power sources, steam reforming of biomassderived methane represents a reliable and complementary thermochemical route, provided that this heat-demanding process is supplied with renewable heat to obtain 100%“green” hydrogen.Today, steam methane reforming is the most used industrial process for hydrogen production
This paper presents the state of the art of research activities carried out by ENEA on renewable-heated steam reforming and the perspectives for process optimization to obtain cost-competitive green hydrogen production
The above described process scheme includes several innovative process units integrated in the molten salt loop: the concentrating solar thermal (CST) system with Thermal Energy Storage (TES), the molten salt heater (MSH), the steam generator and the steam reformers heated with the molten salt
Summary
The growing interest on hydrogen requires evaluating all possible conversion processes for its production. The above described process scheme includes several innovative process units integrated in the molten salt loop: the CST system with TES, the MSH, the steam generator and the steam reformers heated with the molten salt These key units have been individually developed and successfully tested at the pilot or pre-commercial scales by ENEA in different projects. In the project MATS, ENEA has developed and demonstrated an innovative approach that integrates the following units at the 5 MW (thermal) scale: parabolic linear concentrators with direct solar heating of molten salt up to 550°C, a gas fuelled MSH, and single-tank TES integrated with a super-heated steam generator (Figure 4). Specific CO2 emissions yearly operation hours solar-only 4,456 hr/year hybrid 8,000 hr/year
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