Publications

During the last two decades Gulf Cooperation Council (GCC) countries have seen their population economies and energy production growing steeply with a substantial increase in Gross Domestic Product. As a result of this growth GCC consumption-based carbon dioxide (CO2) emissions increased from 540.79 Metric tons of CO2 equivalent (MtCO2) in 2003 to 1090.93 MtCO2 in 2020. The assumptions and strategies that have driven energy production in the past are now being recast to achieve a more sustainable economic development. The aim of this study is to review and analyze ongoing energy transition strategies that characterize this change to identify challenges and opportunities for bolstering the effectiveness of current strategic orientations. The ensuing analysis shows that since COP26 GCC countries have been pursuing a transition away from carbon-based energy policies largely characterized by the adoption of solar PV with other emerging technologies including energy storage carbon capture and hydrogen generation and storage. While as of 2022 renewable energy adoption in the GCC only represented 0.15 % of global installed capacity GCC countries are making strong efforts to achieve their declared 2030 energy targets that average about 26 % with peaks of 50 % in Saudi Arabia and 30 % in the UAE and Oman. With reference to solar energy plans are afoot to add 42.1 GW of solar photovoltaics and concentrated solar power which will increase 8-fold the current installed renewable capacity (5.1 GW). At the same time oil and gas production rates remain stable and fossil fuel subsidies have grown in the last few years. Also there is a marked preference for the deployment of CCUS and utility-scale solar energy technology vs. distributed solar energy energy efficiency and nature-based solutions. The pursuit of energy transition in the GCC will require increased efforts in the latter and other overlooked strategic endeavors to achieve a more balanced portfolio of sustainable energy solutions with stronger emphasis on energy efficiency (as long as rebound effects are mitigated) and nature-based solutions. Increased efforts are also needed in promoting governance practices aimed to institutionalize regulatory frameworks incentives and cooperation activities that promote the reduction of fossil fuel subsidies and the transition away from fossil fuels.

Hydrogen Refueling Stations (HRS) are a key infrastructure to the successful deployment of hydrogen mobility. Their cost-effectiveness will represent an increasingly crucial issue considering the foreseen growth of vehicle fleets from few captive fleets to large-scale penetration of hydrogen vehicles. In this context a detailed component-oriented cost model is important to assess HRS costs for different design concepts layout schemes and possible customizations respect to aggregate tools which are mostly available in literature. In this work an improved version of a previously developed component-oriented scale-sensitive HRS cost model is applied to 5 different European HRS developed within the 3Emotion project with different refueling capacities (kgH2/day) hydrogen supply schemes (in-situ production or delivery) storage volumes and pressures and operational strategies. The model output allows to assess the upfront investment cost (CAPEX) the annual operational cost (OPEX) and the Levelized Cost of Hydrogen (LCOH) at the dispenser and identify the most crucial cost components. The results for the five analyzed HRS sites show an LCOH at the nozzle of around 8-9 €/kg for delivery based HRSs which are mainly dominated by the H2 retail price and transport service price and around 11-12 €/kg for on-site producing HRS for which the electrolyzer CAPEX and electricity price plays a key role in the cost structure. The compression storage and dispensing sections account for between 1-3 €/kg according to the specific design & performance requirements of the HRS. The total LCOH values are comparable with literature standard market prices for similar scale HRSs and with the 3Emotion project targets.

At scale biomass-based fuels are seen as long-term alternatives to conventional shipping fuels to reduce greenhouse gas emissions in the maritime sector. While the operational benefits of renewable methanol as a marine fuel are well-known its cost and environmental performance depend largely on production method and geographic context. In this study a techno-economic and environmental assessment of renewable methanol produced by gasification of forestry residues is performed. Two biorefinery systems are modeled thermody namically for the first time integrating several design changes to extend past work: (1) methanol synthesized by gasification of torrefied biomass while removing and storing underground a fraction of the carbon initially contained in it and (2) integration of a polymer electrolyte membrane (PEM) electrolyzer for increased carbon efficiency via hydrogen injection into the methanol synthesis process. The chosen use case is set in California with forest residue biomass as the feedstock and the ports of Los Angeles and Long Beach as the shipping fuel demand point. Methanol produced by both systems achieves substantial lifecycle greenhouse gas emissions savings compared to traditional shipping fuels ranging from 38 to 165% from biomass roadside to methanol combustion. Renewable methanol can be carbon-negative if the CO2 captured during the biomass conversion process is sequestered underground with net greenhouse gas emissions along the lifecycle amounting to − 57 gCO2eq/MJ. While the produced methanol in both pathways is still more expensive than conventional fossil fuels the introduction of CO2eq abatement incentives available in the U.S. and California could bring down minimum fuel selling prices substantially. The produced methanol can be competitive with fossil shipping fuels at credit amounts ranging from $150 to $300/tCO2eq depending on the eligible credits.

The use of green hydrogen as a high-energy fuel of the future may be an opportunity to balance the unstable energy system which still relies on renewable energy sources. This work is a comprehensive review of recent advancements in green hydrogen production. This review outlines the current energy consumption trends. It presents the tasks and challenges of the hydrogen economy towards green hydrogen including production purification transportation storage and conversion into electricity. This work presents the main types of water electrolyzers: alkaline electrolyzers proton exchange membrane electrolyzers solid oxide electrolyzers and anion exchange membrane electrolyzers. Despite the higher production costs of green hydrogen compared to grey hydrogen this review suggests that as renewable energy technologies become cheaper and more efficient the cost of green hydrogen is expected to decrease. The review highlights the need for cost-effective and efficient electrode materials for large-scale applications. It concludes by comparing the operating parameters and cost considerations of the different electrolyzer technologies. It sets targets for 2050 to improve the efficiency durability and scalability of electrolyzers. The review underscores the importance of ongoing research and development to address the limitations of current electrolyzer technology and to make green hydrogen production more competitive with fossil fuels.

Green hydrogen (GH2) is expected to play an important role in future energy systems in their fight against climate change. This study after briefly recalling how GH2 is produced and the main steps throughout its life cycle analyses its current development environmental and social impacts and a series of case studies from selected literature showing its main applications as fuel in transportation and electricity sectors as a heat producer in high energy intensive industries and residential and commercial buildings and as an industrial feedstock for the production of other chemical products. The results show that the use of GH2 in the three main areas of application has the potential of contributing to the decarbonization goals although its generation of non-negligible impacts in other environmental categories requires attention. However the integration of circular economy (CE) principles is important for the mitigation of these impacts. In social terms the complexity of the value chain of GH2 generates social impacts well beyond countries where GH2 is produced and used. This aspect makes the GH2 value chain complex and difficult to trace somewhat undermining its renewability claims as well as its expected localness that the CE model is centred around.

Electrolytic hydrogen from renewable sources is central to many nations' net-zero emission strategies serving as a low-carbon alternative for traditional uses and enabling decarbonisation across multiple sectors. Current stringent policies in the EU and US are set to soon require hourly time-matching of renewable electricity generation used by electrolysers aimed at ensuring that hydrogen production does not cause significant direct or indirect emissions. Whilst such requirements enhance the “green credentials” of hydrogen they also increase its production costs. A modest relaxation of these requirements offers a practicable route for scaling up low-carbon hydrogen production optimising both costs and emission reductions. Moreover in jurisdictions with credible and near-to-medium-term decarbonisation targets immediate production of electrolytic hydrogen utilising grid electricity would have a lifetime carbon intensity comparable to or even below blue hydrogen and very significantly less than that of diesel emphasising the need to prioritise rapid grid decarbonisation of the broader grid.

This paper examines the changes in the performance level and pollutant emissions of a combustion chamber for turbofan engines. Two different fuels are compared: a conventional liquid fuel of the JET-A (kerosene) class and a hydrogen-based gaseous fuel. A turbofan engine delivering a 70 kN thrust at cruise conditions and 375 kN thrust at takeoff is considered. The comparison is carried out by investigating the combustion pattern with different boundary conditions the latter assigned along a typical flight mission. The calculations rely on a combined approach with a preliminary lumped parameter estimation of the engine performance and thermodynamic properties under different flight conditions (i.e. take-off climbing and cruise) and a CFD-based combustion simulation employing as boundary conditions the outputs obtained from the 0-D computations. The results are discussed in terms of performance thermal properties distributions throughout the combustor and of pollutant concentration at the combustor outflow. The results demonstrate that replacing the JET-A fuel with hydrogen does not affect the overall engine performance significantly and stable and efficient combustion takes place inside the burner although a different temperature regime is observable causing a relevant increase in thermal NO emissions.

Biohydrogen a low-carbon footprint technology can play a significant role in decarbonizing the energy system. It uses existing infrastructure is easily transportable and produces no greenhouse gas emissions. Four technologies can be used to produce biohydrogen: photosynthetic biohydrogen dark fermentation (DF) photo-fermentation and microbial electrolysis cells (MECs). DF produces more biohydrogen and is flexible with organic substrates making it a sustainable method of waste repurposing. However low achievable biohydrogen yields are a common issue. To overcome this catalytic mechanisms including enzymatic systems such as [Fe-Fe]- and [Ni-Fe]-hydrogenases in DF and electroactive microbial consortia in MECs alongside advanced electrode catalysts which collectively surmount thermodynamic and kinetic constraints and the two stage system such as DF connection to photo-fermentation and anaerobic digestion (AD) to microbial electrolysis cells (MECs) have been investigated. MECs can generate biohydrogen at better yields by using sugars or organic acids and combining DF and MEC technologies could improve biohydrogen production. As such this review highlights the challenges and possible solutions for coupling DF–MEC while also offering knowledge regarding the technical and microbiological aspects.

The article discusses a regenerative heat exchange system for a solid oxide electrolyzer cell (SOEC) used in the production of green hydrogen. The heating system comprises four heat exchangers one condenser heat exchanger and a mixer evaporator. A pump and two throttle valves have been added to separate the hydrogen at an elevated steam condensation temperature. Assuming steady flow a thermodynamic analysis was performed to validate the design and to predict the main parameters of the heating system. Numerical optimization was then used to determine the optimal temperature distribution ensuring the lowest possible additional external energy requirement for the regenerative system. The proportions of energy gained through heat exchange were determined and their distribution analyzed. The calculated thermal efficiency of the regenerative system is 75% while its exergy efficiency is 73%. These results can be applied to optimize the design of heat exchangers for hydrogen production systems using SOECs.

Plastic waste continues to increasingly pollute the environment. Currently a significant portion of this waste is either landfilled or incinerated to generate energy which leads to substantial CO2 emissions. However thermochemical processing is a potential solution to create a circular economy with pyrolysis combined with the subsequent high-temperature treatment of the vapour-gas mixture being a method preferable to incineration. This study investigated the optimal conditions for the two-stage pyrolysis of non-recyclable plastic waste. The process involved a low-temperature treatment of feedstock followed by high-temperature exposure of the vapour-gas mixture in the presence of a carbon matrix. The final products of the two-stage pyrolysis were: synthesis gas mainly consisting of hydrogen and carbon monoxide; solid pyrolysis residue obtained in the first stage and high-carbon material during the second stage was obtained. The first stage of the two-stage pyrolysis was carried out at various temperatures ranging from 460 to 540 ◦C followed by cracking at 600 to 1000 ◦C with different ratios of packaging waste to wood charcoal (1:2 1:4 1:6). The conditions for obtaining more than 70 vol% hydrogen in the synthesis gas from packaging waste were determined the effect of changing the process parameters was studied. The decomposition kinetics of packaging waste showed activation energies of the first and second steps: 165 and 255 kJ/mol (Ozawa–Flynn–Wall method) 164 and 259 kJ/mol (Kissinger–Akahira–Sunose method) respectively. This work contributes to the study of efficient recycling methods for non-recyclable packaging waste and promotes advancements in sustainable waste management practices.