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Technical and economic assessment of renewable hydrogen production and utilization for the transportation sector
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Date
2024
Authors
Li, Yunfei
Journal Title
Journal ISSN
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Publisher
University College Cork
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Abstract
Hydrogen energy is mooted to play a critical role in decarbonization of the transportation sector, due in part to its relatively high energy density (120 MJLHV/kg) and clean combustion product (the only combustion product is water). Renewable hydrogen can be generated from various renewable energy sources (such as solar, wind, tidal, and biomass) through technologies including water electrolysis, biomass gasification, microbial fermentation, and water thermochemical cycles. The produced renewable hydrogen can then be utilized in the transportation sector via hydrogen fuel cell vehicles or after conversion to other renewable fuel vectors (including but not limited to ammonia (NH3), methane (CH4), methanol (CH3OH) or Fischer-Tropsch (F-T) fuels). However, despite extensive research on renewable hydrogen production and application technologies in the current literature, there is no definitive specific technical roadmap for its production and application in the transportation sector. This is viewed as an overarching state-of-the-art research gap in this thesis. Therefore, this study aims to undertake a quantitative analysis and comparison of renewable hydrogen production technologies as well as utilization using techno-economic analysis (TEA) and multi-criteria decision analysis (MCDA) methods.
For the renewable hydrogen production technologies, a literature review indicates that polymer electrolyte membrane (PEM) water electrolysis technology has quickly become a prominent method for renewable hydrogen production due to its high electrolyser stack efficiency (58%-75%), the high purity of the produced hydrogen (99.99%), rapid advancement in technology readiness level ((TRL) which is expected to reach 9 by 2030), quick system response time (milliseconds), compact design, and flexible scalability to meet varying production demands. Alternatively, biomass gasification technology is also suitable for current hydrogen production requirements due to its maturity (TRL = 8 based on 2024 scenario), wide applicability to different feedstocks (including but not limited to willow, coconut shell, rice husk, and forestry thinning), ability to mitigate the environmental impact of waste disposal, and capability to produce value-added byproducts such as syngas for chemical synthesis and biochar for soil enhancement. Thus, PEM water electrolysis and biomass gasification technologies are suggested as the most suitable renewable hydrogen production methods for short-term implementation by 2030.
For renewable hydrogen utilization, the produced renewable hydrogen can be used directly or as a feedstock, in conjunction with a source of biogenic CO2 to produce synthetic hydrocarbons or combined with N2 to produce NH3. Therefore, this thesis introduces the concepts of power-to-x (PtX) and biomass-to-x (BtX) to produce renewable CH4, CH3OH, NH3, and F-T fuels. Following the numerical calculations of mass and energy flows for these technological pathways, a techno-economic analysis was performed for each pathway, providing a comprehensive assessment of the system performance of these renewable fuel production technologies.
Technically, it is calculated that hydrogen production technologies exhibit the highest system energy efficiency (74% for power-to-hydrogen (PtH2) and 63% for biomass-to-hydrogen (BtH2)) among the five renewable fuels when excluding the efficiency associated with sourcing biogenic CO2. However, when biogenic CO2 is utilized to produce renewable hydrocarbons, the CO2 mass demand varies by nearly 100% depending on the renewable hydrocarbon pathway despite use of the same electrolyser. The sustainable supply of biogenic CO2 is a critical bottleneck for the development of renewable hydrocarbons. From an energy perspective, the CH3OH synthesis pathway shows superior system energy efficiency to other hydrocarbons (which include carbon and as such excludes hydrogen itself as a separate energy vector), achieving 59.8% in the PtX configuration (based on a 60 MW electrolyser capacity) and 61.0% in the BtX configuration (based on a 50 MW gasification capacity). This is followed by the CH4 synthesis pathway, with efficiencies of 55.3% for PtX and 52.5% for BtX.
Economically, PtX technology is heavily reliant on the availability of abundant renewable electricity and water, which accounts for more than 90% of the annual operating expenditure. In contrast, the capital expenditure (CAPEX) for the BtX pathway is approximately 46%-49% higher than that of the PtX pathway, resulting in a levelised cost of energy (LCOE) that is 4%-40% higher than that of PtX fuels, making BtX technology less economically favorable.
The TEA method demonstrates notable limitations when comparing technologies across multiple criteria. To address this limitation, this thesis introduces the MCDA method to facilitate the comparison of PtX and BtX pathways and assess the hierarchy ranking of these renewable fuel production technologies. This study employs the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR), and Weighted Sum Method (WSM) methods for the MCDA process. Six technical and economic criteria were evaluated: system energy efficiency, land area requirements for feedstock cultivation, resource potential, capital expenditure, operating expenditure, and the levelized cost of renewable energy. The results indicate that "capital expenditure" receives the highest weight based on the objective weighting method Criteria Importance Through Intercriteria Correlation (CRITIC). Following in importance are the criteria "land area requirements for feedstock cultivation" and "resource potential". The MCDA results rank power-to-hydrogen (PtH2) highest, followed by power-to-ammonia (PtNH3) and power-to-methanol (PtCH3OH), with Biomass-to-Fischer-Tropsch (BtF-T) fuels lowest ranked. The subsequent sensitivity analysis confirms the stability of the top-ranked production technology despite changes in technical and economic criteria weights.
This thesis provides strategic insights into the selection of renewable hydrogen production and utilization technologies by evaluating their technical and economic performance, equipping stakeholders with essential knowledge to facilitate the integration of renewable hydrogen into the decarbonization pathways of transportation sector.
Description
Keywords
Renewable hydrogen , Techno-economic analysis , Transportation decarbonization
Citation
Li, Y. 2024. Technical and economic assessment of renewable hydrogen production and utilization for the transportation sector. PhD Thesis, University College Cork.