In April 2018, the International Maritime Organisation adopted an ambitious plan to contribute to the global efforts to reduce the Greenhouse Gas emissions, as set by the Paris Agreement, by targeting a 50% reduction in shipping’s Green House Gas emissions by 2050, benchmarked to 2008 levels. To meet these challenging goals, the maritime industry must introduce environmentally friendly fuels with negligible, or low SO_X, NO_X and CO₂ emissions. Ammonia use in maritime applications is considered promising, due to its high energy density, low flammability, easy storage and low production cost. Moreover, ammonia can be used as fuel in a variety of propulsors such as fuel cells and can be produced from renewable sources. As a result, ammonia can be used as a versatile marine fuel, exploiting the existing infrastructure, and having zero SO_X and CO₂ emissions. However, there are several challenges to overcome for ammonia to become a compelling fuel towards the decarbonisation of shipping. Such factors include the selection of the appropriate ammonia-fuelled power generator, the selection of the appropriate system safety assessment tool, and mitigating measures to address the hazards of ammonia. This paper discusses the state-of-the-art of ammonia fuelled fuel cells for marine applications and presents their potential, and challenges.

We report the three-phase (hydrate–liquid water–vapor) equilibrium conditions of the hydrogen–water binary system calculated with molecular dynamics simulations via the direct phase coexistence approach. A significant improvement of ∼10.5 K is obtained in the current study, over earlier simulation attempts, by using a combination of modifications related to the hydrogen model that include (i) hydrogen Lennard-Jones parameters that are a function of temperature and (ii) the water–guest energy interaction parameters optimized further by using the Lorentz–Berthelot combining rules, based on an improved description of the solubility of hydrogen in water.

Thermodynamic models based on the van der Waals–Platteeuw statistical theory (Adv. Chem. Phys. 2, 1 (1959)) can be very accurate in describing hydrate equilibrium conditions, even for some occasions when multiple cavity occupancy occurs. These are cases outside the range of assumptions used for the development of the original statistical theory. However, during multiple cavity occupancy such models can perform poorly when calculating the cavity occupancies. This paper reports novel Grand Canonical Monte Carlo molecular simulations for the case of pure structure II N₂ hydrate and compares the calculated cavity occupancies with experimental data and observe reasonable agreement. Also examined are the van der Waals–Platteeuw-based modifications that retained the single-occupancy assumption of the original theory and how they perform when predicting cavity occupancies and hydrate equilibrium pressures.

Clathrate hydrates have characteristic properties that render them attractive for a number of industrial applications. Of particular interest are the following two cases: (i) the incorporation of large amounts of gas molecules into the solid structure has resulted in considering hydrates as possible material for the storage/transportation of energy or environmental gases, and (ii) the selective incorporation of guest molecules into the solid structure has resulted in considering hydrates for gas-mixture separations. For the proper design of such industrial applications, it is essential to know accurately a number of thermodynamic, structural and transport properties. Such properties can either be measured experimentally or calculated at different scales that span the molecular scale-up to the continuum scale. By using clathrate hydrates as a particular case study, we demonstrate that performing studies at multiple length scales can be utilised in order to obtain properties that are essential to process design. GRAPHICAL ABSTRACT

Small mοdular reactors (SMRs) are nuclear reactors with a smaller capacity than traditional large-scale nuclear reactors, offering advantages such as increased safety, flexibility, and cost-effectiveness. By producing zero carbon emissions, SMRs represent an interesting alternative for the decarbonization of power grids. Additionally, they present a promising solution for the production of hydrogen by providing large amounts of energy for the electrolysis of water (pink hydrogen). The above hint at the attractiveness of coupling SMRs with hydrogen production and consumption centers, in order to form clusters of applications which use hydrogen as a fuel. This work showcases the techno-economic feasibility of the potential installation of an SMR system coupled with hydrogen production, the case study being the island of Crete. The overall aim of this approach is the determination of the optimal technical characteristics of such a system, as well as the estimation of the potential environmental benefits, in terms of reduction of CO₂ emissions. The aforementioned system, which is also connected to the grid, is designed to serve a portion of the electric load of the island, while producing enough hydrogen to satisfy the needs of the nearby industries and hotels. The results of this work could provide an alternative sustainable approach on how a hydrogen economy, which would interconnect and decarbonize several industrial sectors, could be established on the island of Crete. The proposed systems achieve an LCOE between EUR 0.046/kWh and EUR 0.052/kWh while reducing carbon emissions by more than 5 million tons per year in certain cases.