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Environmental regulations have always been an essential component in the natural gas supply chain with recent and greater emphasis on shipping operations. Recently more stringent regulations have been imposed by the International Maritime Organization on global maritime shipping operations. This review explores the challenges and opportunities associated with substituting heavy fuel oils used for maritime transportation with relatively cleaner fuels. First the review considers the feasibility and environmental dimensions of different bunker fuels including liquefied natural gas hydrogen and ammonia. Also the operational viability and optimal conditions for these fuels are examined. Secondly the review considers the entire supply chain with an emphasis on how liquefied natural gas exporters can establish synergies across the supply chain to also deliver the end-product required by customers instead of delivering only liquefied natural gas. Finally measures that can support ship operators to comply with environmental regulations are suggested. The outcomes of this review supports the notion that the demand for alternative fuels will continue to increase as the transportation sector moves towards integrating cleaner fuels to comply with increasing environmental regulations.

This paper discusses the numerical modeling of an automobile fuel cell system using a two-stage turbo-compressor for air supply. The numerical model incorporates essential input parameters for air and hydrogen flow. The model also performed mass and energy balances across different components such as pump fan heat-exchanger air compressor and keeps in consideration the pressure losses across flow pipes and various mechanical parts. The compressor design process initiates with numerical analysis of the preliminary design of a highly efficient two-stage turbo compressor with an expander as a single-stage compressor has several limitations in terms of efficiency and pressure ratio. The compressor’s design parameters were carefully studied and analyzed with respect to the highly efficient fuel cell stack (FCS) used in modern hydrogen vehicles. The model is solved to evaluate the overall performance of PEM FCS. The final compressor has a total pressure and temperature of 4.2 bar and 149.3°C whereas the required power is 20.08kW with 3.18kW power losses and having a combined efficiency of 70.8%. According to the FC model with and without expander the net-power outputs are 98.15kW and 88.27kW respectively and the maximum efficiencies are 65.1% and 59.1% respectively. Therefore it can be concluded that a two-stage turbo compressor with a turbo-expander can have significant effects on overall system power and efficiency. The model can be used to predict and optimize system performance for PEM FCS at different operating conditions.

Overview of advances in the technology of solid state hydrogen storage methods applying different kinds of novel materials is provided. Metallic and intermetallic hydrides complex chemical hydride nanostructured carbon materials metal-doped carbon nanotubes metal-organic frameworks (MOFs) metal-doped metal organic frameworks covalent organic frameworks (COFs) and clathrates solid state hydrogen storage techniques are discussed. The studies on their hydrogen storage properties are in progress towards positive direction. Nevertheless it is believed that these novel materials will offer far-reaching solutions to the onboard hydrogen storage problems in near future. The review begins with the deficiencies of current energy economy and discusses the various aspects of implementation of hydrogen energy based economy.

This study discusses and thermodynamically analyzes several energy storage systems namely; pumped hydro compressed air hot water storage molten salt thermal storage hydrogen ammonia lithium-ion battery Zn-air battery redox flow battery reversible fuel cells supercapacitors and superconducting magnetic storage through the first and second law of thermodynamics. By fixing an electrical output of 100 kW for all systems the energy efficiencies obtained for the considered energy storage methods vary between 10.9% and 74.6% whereas the exergy efficiencies range between 23.1% and 71.9%. The exergy destruction rates are also calculated for each system ranging from 1.640 kW to 356 kW. The highest destruction rate is obtained for the solar-driven molten salt thermal energy storage system since it includes thermal energy conversion via the heliostat field. Furthermore the roundtrip efficiencies for the electrochemical and electromagnetic storage systems are compared with the analyzed systems ranging from 58% to 94%. Renewable sources (solar wind ocean current biomass and geothermal) energy conversion efficiencies are also considered for the final round-trip performances. The molten salt and hot water systems are applicable to solar geothermal and biomass. The highest source-to-electricity efficiency is obtained for the super magnetic storage with 37.6% when using wind ocean current and biomass sources.

In situ electrochemical microcantilever bending tests were conducted in this study to investigate the role of grain boundaries (GBs) in hydrogen embrittlement (HE) of Alloy 725. Specimens were prepared under three different heat treatment conditions and denoted as solution-annealed (SA) aged (AG) and over-aged (OA) samples. For single-crystal beams in an H-containing environment all three heat-treated samples exhibited crack formation and propagation; however crack propagation was more severe in the OA sample. The anodic extraction of H presented similar results as those under the H-free condition indicating the reversibility of the H effect under the tested conditions. Bi-crystal micro-cantilevers bent under H-free and H-charged conditions revealed the significant role of the GB in the HE of the beams. The results indicated that the GB in the SA sample facilitated dislocation dissipation whereas for the OA sample it caused the retardation of crack propagation. For the AG sample testing in an H-containing environment led to the formation of a sharp severe crack along the GB path.

Recently interest in developing H2 strategies with carbon capture and storage (CCS) technologies has surged. Considering that this paper reviews recent literature on blue H2 a potential low-carbon short-term solution during the H2 transition period. Three key aspects were the focus of this paper. First it presents the processes used for blue H2 production. Second it presents a detailed comparison between blue H2 and natural gas as fuels and energy carriers. The third aspect focuses on CO2 sequestration in depleted natural gas reservoirs an essential step for implementing blue H2. Globally ~ 75% of H2 is produced using steam methane reforming which requires CCS to obtain blue H2. Currently blue H2 needs to compete with other advancing technologies such as green H2 solar power battery storage etc. Compared to natural gas and liquefied natural gas blue H2 gas results in lower CO2 emissions since CCS is applied. However transporting liquefied and compressed blue H2 entails higher energy economic and environmental costs. CCS must be appropriately implemented to produce blue H2 successfully. Due to their established capacity to trap hydrocarbons over geologic time scales depleted natural gas reservoirs are regarded as a viable option for CCS. Such a conclusion is supported by several simulation studies and field projects in many countries. Additionally there is much field experience and knowledge on the injection and production performance of natural gas reservoirs. Therefore using the existing site infrastructure converting these formations into storage reservoirs is undemanding.

As a result of particular locations of large-scale energy producers and increases in energy demand transporting energy has become one of the key challenges of energy supply. For a long-distance ocean transportation transfer of energy carriers via ocean tankers is considered as a decent solution compared to pipelines. Due to cryogenic temperatures of energy carriers heat leaks into storage tanks of these carriers causes a problem called boil-off gas (BOG). BOG losses reduce the quantity of energy carriers which affects their economic value. Therefore this study proposes to examine the effects of BOG economically in production and transportation phases of potential energy carriers produced from natural gas namely; liquefied natural gas (LNG) dimethyl-ether (DME) methanol liquid ammonia (NH3) and liquid hydrogen (H2). Mathematical approach is used to calculate production and transportation costs of these energy carriers and to account for BOG as a unit cost within the total cost. The results of this study show that transportation costs of LNG liquid ammonia methanol DME and liquid hydrogen from natural gas accounting for BOG are 0.74 $/GJ 1.09 $/GJ 0.68 $/GJ 0.53 $/GJ and 3.24 $/GJ respectively. DME and methanol can be more economic compared to LNG to transport the energy of natural gas for the same ship capacity. Including social cost of carbon (SCC) within the total cost of transporting the energy of natural gas the transportation cost of liquid ammonia is 1.11 $/GJ whereas LNG transportation cost rises significantly to 1.68 $/GJ at SCC of 137 $/t CO2 eq. Consequently liquid ammonia becomes economically favored compared to LNG. Transportation cost of methanol (0.70 $/GJ) and DME (0.55 $/GJ) are also lower than LNG however liquid hydrogen transportation cost (3.24 $/GJ) is still the highest even though the increment of the cost is about 0.1% as SCC included within the transportation cost.

Low carbon hydrogen can be an excellent source of clean energy which can combat global climate change and poor air quality. Hydrogen based economy can be a great opportunity for a country like Qatar to decarbonize its multiple sectors including transportation shipping global energy markets and industrial sectors. However there are still some barriers to the realization of a hydrogen-based economy which includes large scale hydrogen production cost infrastructure investments bulk storage transport & distribution safety consideration and matching supply-demand uncertainties. This paper highlights how the aforementioned challenges can be handled strategically through a multi-sector industrial-urban symbiosis for the hydrogen supply chain implementation. Such symbiosis can enhance the mutual relationship between diverse industries and urban planning by exploring varied scopes of multi-purpose hydrogen usage (i.e. clean energy source as a safer carrier industrial feedstock and intermittent products vehicle and shipping fuel and international energy trading etc.) both in local and international markets. It enables individual entities and businesses to participate in the physical exchange of materials by-products energy and water with strategic advantages for all participants. Besides waste/by-product exchanges several different kinds of synergies are also possible such as the sharing of resources and shared facilities. The diversified economic base regional proximity and the facilitation of rules strategies and policies may be the key drivers that support the creation of a multi-sector hydrogen supply chain in Qatar.

Hydrogen fuel production from methane cracking is a cleaner process compared to steam methane reforming due to zero greenhouse gas emissions. Carbon black that is co-produced is valuable and can be marketed to other industries. As this is a high-temperature process using solar energy can further improve its sustainability. In this study an integrated solar methane cracking system is proposed and the efficient utilization of the hydrogen and carbon products is explored. The carbon by-product is used in a direct carbon fuel cell and oxy- combustion. These processes eliminate the need for carbon capture technologies as they produce pure CO2 exhaust streams. The CO2 produced from the systems is used for enhanced oil recovery to produce crude oil. The produced turquoise hydrogen is liquified to make it suitable for exportation. The process is simulated on Aspen Plus® and its energy and exergy efficiencies are evaluated by carrying out a detailed thermodynamic analysis. A reservoir simulation is used to study the amount of oil that can be produced using the captured CO2. The overall system is studied for oil production over 20 years and energy and exergy of efficiencies 42.18% and 40.18% respectively were found. Enhanced oil recovery improves the recovery rate from 24.8% to 64.3%.

Countries are under increasing pressure to reduce greenhouse gas emissions as an act upon the Paris Agreement. The essential emission reductions can be achieved by environmentally friendly solutions in particular the introduction of low carbon or carbon-free fuels. This study presents a comparative life cycle assessment of various energy carriers namely; liquefied natural gas methanol dimethyl ether liquid hydrogen and liquid ammonia that are produced from natural gas or renewables to investigate greenhouse gas emissions generated from the complete life cycle of energy carriers accounting for the leaks as well as boil-off gas occurring during storage and transportation. The entire fuel life cycle is considered consisting of production storage transportation via an ocean tanker to different distances and finally utilization in an internal combustion engine of a road vehicle. The results show that using natural gas as a feedstock total greenhouse gas emissions during production ocean transportation (over 20000 nmi) by a heavy fuel oil-fueled ocean tanker and utilization in an internal combustion engine are 73.96 95.73 93.76 50.83 and 100.54 g CO2 eq. MJ1 for liquified natural gas methanol dimethyl ether liquid hydrogen and liquid ammonia respectively. Liquid hydrogen produced from solar electrolysis is the cleanest energy carrier (42.50 g CO2 eq. MJ1 fuel). Moreover when liquid ammonia is produced via photovoltaic-based electrolysis (60.76 g CO2 eq. MJ1 fuel) it becomes cleaner than liquified natural gas. Although producing methanol and dimethyl ether from biomass results in a large reduction in total greenhouse gas emissions compared to conventional methanol and dimethyl ether production with a value of 73.96 g CO2 eq. per MJ liquified natural gas still represents a cleaner option than methanol and dimethyl ether considering the full life cycle.