Publications

To provide an effective energy transition hydrogen is required to decarbonize the hard-toabate industries. As a case study this paper provides a holistic view of the hydrogen energy transition in the United Arab Emirates (UAE). By utilizing the directional distance function undesirable data envelopment analysis model the energy economic and environmental efficiency of UAE sectors are estimated from 2001 to 2020 to prioritize hydrogen sector coupling. Green hydrogen production efficiency is analyzed from 2020 to 2050. The UAE should prioritize the industry and transportation sectors with average efficiency scores of 0.7 and 0.74. The decomposition of efficiency into pure technical efficiency and scale efficiency suggests policies and strategies should target upscaling the UAE’s low-carbon hydrogen production capacity to expedite short-term and overall production efficiency. The findings of this study can guide strategies and policies for the UAE’s low-carbon hydrogen transition. A framework is developed based on the findings of the study.

Future energy systems could rely on hydrogen (H2) to achieve decarbonisation and net-zero goals. In a similar energy landscape to natural gas H2 emissions occur along the supply chain. It has been studied how current gas infrastructure can support H2 but there is little known about how H2 emissions affect global warming as an indirect greenhouse gas. In this work we have estimated for the first time the potential emission profiles (g CO2eq/MJ H2HHV) of H2 supply chains and found that the emission rates of H2 from H2 supply chains and methane from natural gas supply are comparable but the impact on global warming is much lower based on current estimates. This study also demonstrates the critical importance of establishing mobile H2 emission monitoring and reducing the uncertainty of short-lived H2 climate forcing so as to clearly address H2 emissions for net-zero strategies.

In electricity systems mainly supplied with variable renewable electricity (VRE) the variable generation must be balanced. Hydrogen as an energy carrier combined with storage has the ability to shift electricity generation in time and thereby support the electricity system. The aim of this work is to analyze the competitiveness of hydrogen-fueled gas turbines including both open and combined cycles with flexible fuel mixing of hydrogen and biomethane in zero-carbon emissions electricity systems. The work applies a techno-economic optimization model to future European electricity systems with high shares of VRE.<br/>The results show that the most competitive gas turbine option is a combined cycle configuration that is capable of handling up to 100% hydrogen fed with various mixtures of hydrogen and biomethane. The results also indicate that the endogenously calculated hydrogen cost rarely exceeds 5 €/kgH2 when used in gas turbines and that a hydrogen cost of 3–4 €/kgH2 is for most of the scenarios investigated competitive. Furthermore the results show that hydrogen gas turbines are more competitive in wind-based energy systems as compared to solar-based systems in that the fluctuations of the electricity generation in the former are fewer more irregular and of longer duration. Thus it is the characteristics of an energy system and not necessarily the cost of hydrogen that determine the competitiveness of hydrogen gas turbines.

Global efforts towards de-carbonization give rise to remarkable energy challenges which include renewable energy penetration increase and intermediate energy carriers for a sustainable transition. In order to reduce the dependence on fossil fuels alternative sources are considered by commodities to satisfy their increasing electricity demand as a consequence of a rise in population and the quantity of residential appliances in forthcoming years. The near-term trends appear to be in fuel and emission reduction techniques through the integration of carbon capture and storage and more efficient energy carriers exploiting alternative energy sources such as natural gas and hydrogen. Formulating both the fuel consumption and emission released the obtained experimental results showed that the total production cost can be reduced by making use of natural gas for the transition towards 2035’s targets. Maximum profits will be achieved with hydrogen as the only fuel in modern power plants by 2050. In this way the lowest electricity production can be achieved as well as the elimination of carbon dioxide emissions. Since the integration of renewable energy resources in the sectors of electricity heating/cooling and transportation will continuously be increased alternative feedstocks can serve as primary inputs and contribute to production cost profits improved utilization factors and further environmental achievements.

Hydrogen fuel cells have the potential to play a significant role in the decarbonization of the transportation sector globally and especially in California given the strong regulatory and policy focus. Nevertheless numerous questions arise regarding the environmental impact of the hydrogen supply chain. Hydrogen is usually delivered on trucks in gaseous form but can also be transported via pipelines as gas or via trucks in liquid form. This study is a comparative attributional life cycle analysis of three hydrogen production methods alongside truck and pipeline transportation in gaseous form. Impacts assessed include global warming potential (GWP) nitrogen oxide volatile organic compounds and particulate matter 2.5 (PM2.5). In terms of GWP the truck transportation pathway is more energy and ecologically intensive than pipeline transportation despite gaseous truck transport being more economical. A sensitivity analysis of pipeline transportation and life cycle inventories (LCI) attribution is included. Results are compared across multiple scenarios of the production and transportation pathways to discover the strongest candidates for minimizing the environmental footprint of hydrogen production and transportation. The results indicate the less ecologically intensive pathway is solar electrolysis through pipelines. For 1 percent pipeline attribution the total CO2eq produced per consuming 1 MJ of hydrogen in a fuel cell pickup truck along this pathway is 50.29 g.

Previously suggested options to achieve carbon neutrality involve the use of fossil fuels with carbon capture or exploiting biomass as sources of energy. Industrial high-temperature heating could possibly exploit electrical heating or combustion using hydrogen. However it is difficult to replace all the current coal or natural gas furnaces with these options for chemical industry. In this work a method that integrates solid oxide electrolysis cells (SOEC) and H2–O2 combustion is proposed and the related parameters are modelled to analyze their impacts. There is no waste heat and waste emissions in the proposed option and all substances are recycled. Unlike previous research the heat required for SOEC operation is generated from H2 combustion. The best working condition is under thermoneutral voltage and the highest electricity-to-thermal efficiency that can be achieved is 86.88% under a current density of 12000 A/m2 and operating temperature of 750 ◦C. Ohmic overpotential has the greatest effect on electricity consumption and the anode activation overpotential is the second most important option. Increasing combustion product temperature cannot significantly improve thermal efficiency but can raise the available maximum thermal energy.

One of the many technical benefits of green diesel (GD) is its ability to be oxygenated lubricated and adopted in diesel engines without requiring hardware modifications. The inability of GD to reduce exhaust tail emissions and its poor performance in endurance tests have spurred researchers to look for new clean fuels. Improving gasohol/hydrogen blend (GHB) spark ignition is critical to its long-term viability and accurate demand forecasting. This study employed the Response Surface Methodology (RSM) to identify the appropriate GHB and engine speed (ES) for efficient performance and lower emissions in a GHB engine. The RSM model output variables included brake specific fuel consumption (BSFC) brake thermal efficiency (BTE) hydrocarbon (HC) carbon dioxide (CO2) and carbon monoxide (CO) while the input variables included ES and GHB. The Analysis of Variance-assisted RSM revealed that the most affected responses are BSFC and BTE. Based on the desirability criteria the best values for the GHB and the ES were determined to be 20% and 1500 rpm respectively while the validation between experimental and numerical results was calculated to be 4.82. As a result the RSM is a useful tool for predicting the optimal GHB and ES for optimizing spark-ignition engine characteristics and ensuring benign environment.

Due to the simple structure and quick refueling process of the compressed hydrogen storage tank it is widely used in fuel cell vehicles at present. However temperature rise may lead to a safety problem during charging of a compressed hydrogen storage tank. To ensure the refueling safety the thermal effects need to be studied carefully during hydrogen refueling process. In this paper based on the mass and energy balance equations a general heat transfer model for refueling process of compressed hydrogen storage tank is established. According to the geometric model of the tank wall structure we have built three lumped parameter models: single-zone (hydrogen) dual-zone (hydrogen and tank wall) and triple-zone (hydrogen tank wall liner and shell) model. These three lumped parameter models are compared with U.S. Naval gas charging model and SAE MC method based refueling model. Under adiabatic and diathermic conditions four models are built in Matlab/Simulink software to simulate the hydrogen refueling process under corresponding conditions. These four models are: single-zone singletemperature (hydrogen) dual-zone single-temperature (hydrogen) dual-zone dual-temperature (hydrogen and tank wall temperatures) and triple-zone triple-temperature (hydrogen tank wall liner and tank wall shell temperatures). By comparing the analytical solution and numerical solution the temperature rise of the compressed hydrogen storage tank can be described. The analytical and numerical solutions on the heat transfer during hydrogen refueling process will provide theoretical guidance at actual refueling station so as to improve the refueling efficiency and to enhance the refueling safety.

Electrical energy storage technologies for stationary applications are reviewed. Particular attention is paid to pumped hydroelectric storage compressed air energy storage battery flow battery fuel cell solar fuel superconducting magnetic energy storage flywheel capacitor/supercapacitor and thermal energy storage. Comparison is made among these technologies in terms of technical characteristics applications and deployment status.

The use of low carbon fuels (LCFs) in internal combustion engines is a promising alternative to reduce pollution while achieving high performance through the conversion of the high energy content of the fuels into mechanical energy. However optimizing the engine design requires deep knowledge of the complex phenomena involved in combustion that depend on the operating conditions and the fuel employed. In this work computational fluid dynamics (CFD) simulation tools have been used to get insight into the performance of a Volkswagen Polo 1.4L port-fuel injection spark ignition engine that has been fueled with three different LCFs coke oven gas (COG) a gaseous by-product of coke manufacture H2 and CH4. The comparison is made in terms of power pressure temperature heat release flame growth speed emissions and volumetric efficiency. Simulations in Ansys® Forte® were validated with experiments at the same operating conditions with optimal spark advance wide open throttle a wide range of engine speed (2000–5000 rpm) and air-fuel ratio (λ) between 1 and 2. A sensitivity analysis of spark timing has been added to assess its impact on combustion variables. COG with intermediate flame growth speed produced the greatest power values but with lower pressure and temperature values at λ = 1.5 reducing the emissions of NO and the wall heat transfer. The useful energy released with COG was up to 16.5% and 5.1% higher than CH4 and H2 respectively. At richer and leaner mixtures (λ = 1 and λ = 2) similar performances were obtained compared to CH4 and H2 combining advantages of both pure fuels and widening the λ operation range without abnormal combustion. Therefore suitable management of the operating conditions maximizes the conversion of the waste stream fuel energy into useful energy while limiting emissions.