Abstract

The water electrolysis process requires a high DC current supply that can sustain the desired hydrogen production rate over a large period of operation at a competitive cost. During the conversion of electricity from AC to DC, power quality may be affected because of the non-linear effect caused by the power electronics. Most of the recent research has focused on exploring different rectifier topologies. None of them have investigated the influence of cell stack degradation on the performance of power electronics. In this work, we built a one-way interaction model to predict the influence of electrolyzer degradation on power electronics output over multiscale operational time (from milliseconds to years) for proton exchange membrane electrolyzer (PEM). In this model, we assume a constant degradation rate on the electrolyzer that results in a linear increase of internal resistance over time. Counterintuitively, rather than the power quality decreasing, results show that the power quality increased with the electrolyzer degradation for both the AC (power factor and THD) and DC side (ripple) for the 6-pulse thyristor.
Furthermore, the influence of three variables (degradation rate, load current, and topology) on AC (power factor and THD) and DC (ripple factor) side power output were investigated. Finally, results were partially validated with experimental data from a 20 MW scale PEM electrolyzer.

Abstract

The pace of emissions reduction in coal power strongly affects the peaking time of total CO2 emissions in China. Applying Kaya identity, Rollback model, and health impact assessment model, this study proposes an integrated framework for simulating coal power demand and the related CO2 emissions in China’s 29 provinces during 2020-2035, with the evaluation of CO2related health impact in life and economic loss. It is found that the total coal power demand in China kept rising by 5.19% per year in 2009-2019. And the projection demand would still increase, ranging from 4687.26 to 8897.13 billion kW·h under the BAS scenario. Results of spatial heterogeneity show that East China would contribute to the greatest CO2 emissions, valuing as 149.47, 156.11, and 190.21 mg/m3 of CO2 concentrations for the period of 2020-2025, 2026-2030, and 2031-2035. Rapid development scenario (RDS) suggests a potential emission reduction path, in which could avoid life loss of 10539 years and economic loss of 1.07 billion dollars nationwide during 2020-2035. Our findings could provide a deeper understanding of potential peaking paths by provinces, and also assist policymakers in better establishing emissions reduction targets for other nations from a top-down perspective, thus could be of global significance.

Abstract

CO2 injection is a well-documented method for improving hydrocarbon production rates and increasing oilfield recovery factors. In light of climate concerns, there has been a significant push to utilize CO2 injection for the dual objectives of enhancing oil recovery and carbon storage. Despite the proliferation of CCUS related literature, practical considerations related to reservoir management are rarely discussed. Intelligent reservoir management of a field from primary to tertiary recovery phases yields an understanding of key physical properties and mechanism that govern oil recovery. A well-managed reservoir is also better prepared to benefit from CO2 injection for the synergistic objectives of oil recovery and carbon storage. In this work, we address several underexplored areas in CCUS research:

1.Optimization of primary and tertiary depletionplans to “prepare” a field for carbon storage, takinginto consideration pressure, free gas saturation, andliquid phase saturation distributions. Designparametersinclude appropriate production/injection depths andpattern design/rates.
2.Utilization of primary phase learnings to acceleratethe reservoir into tertiary phase (skippingwaterflooding) to maximize carbon storage.
3.The balance of technical and commercialconsiderations for gas injection design, includinggas supply constraints.

Optimizing oil reservoir development for carbon storage is particularly important in countries with absent or nascent CCUS policies. In our work, we present an integrated carbon storage focused development strategy for a mature Indian oilfield. We leverage multiple analytical and numerical tools to perform an integrated analysis of a depleted stacked pay reservoir. The work uses actual field data from multiple sources with over 30 years of dynamic data. The reservoir has a storage potential of over 5 million metric tonnes, with an incremental oil recovery factor of 11%. Eliminating the waterflooding stage addsapproximately 0.5 million tonnes of storage. Continual production of aquifer water adds an estimated 0.35 million tonnes of storage potential annually. The client has over 50 reservoirs at various developmental stages; this work highlights the tremendous potential of these fields for carbon storage with an integrated reservoir management approach.

Abstract

Natural gas has the potential to replace the conventional liquid-based fuel economy. The shale gas boom catalyzed the development of natural gas catering facilities and inventions worldwide. Natural gas has contributed to lowering pollutant emissions and efficient energy conversion in transportation. The significant challenge presents to transporting natural gas economically and more safely. It has been published that liquefied natural gas transportation is favorable for a longer range, while small-scale transportation can be taken using compressed natural gas. Medium-scale natural gas transportation may be tackled by using gas hydrate as a transporting medium for natural gas. The current study discusses storing synthetic natural gas in the form of gas hydrate. The extensive experimental approach was used in the presence of well- known kinetic hydrate promotors and thermodynamic hydrate promotors. The micro Differential Scanning Calorimetry study was also performed in order to understand the fundamentals of the formation and dissociation of natural gas hydrate. The study was also extended for the artificial neural network-based modelling to reduce the future experiments’ dependency.

Abstract

The global emissions increase requires the adoption of proper countermeasures, aimed at tackling climate change. On the one hand, the transition towards a renewable-based energy sector is an undeferrable need, because of its important impact on the overall emissions balance. On the other hand, a single final use can be fed by more than one commodity, and their coexistence/competition paves the way to the development of a multi-commodity energy system, enabling the implementation of the so-called ”cross-sector integration”. In this paper, we propose a conceptual framework for the comparative assessment of the various energy commodity chains, aimed at defining the preferrable ones for residential and transport uses. The evaluation of their overall performance is carried out determining the quantity and the quality of the involved commodities, by adopting energy and exergy efficiency along the entire chain, provided that one unit of primary energy can supply one chain only. This straightforward assessment method is not constrained by any generation capacity and/or emission related targets and introduces a commodity-based evaluation framework, that differs from the already existing ones that adopt a technology-oriented approach.

Abstract

Indirect evaporative cooling (IEC) is a well- known sustainable cooling technology that can potentially replace mechanical cooling equipment and operate as an efficient energy recovery unit or standalone cooling system. However, the technology relies heavily on water evaporation in the wet channels to cool the fresh air in the adjacent channel. Although many moisture-absorbing materials have been proposed for IEC to improve the surface wettability, the uneven water membrane coverage caused by inappropriate nozzle parameters is still a great problem that degrades the evaporation. Therefore, it is critical to optimize the nozzle parameters in water spray systems and arrange the nozzles reasonably above the IEC for more efficient evaporation performance. In this research, a novel 3D simulation model describing the vapor and liquid phase distribution from the spray system was developed to allow a comprehensive parametric study based on Computational Fluid Dynamics (CFD). A test rig of an open-circuit wind tunnel was built to measure the actual wetted areas on the surface of a single channel pair for model validation. The results based on the verified simulation model showed that the water membrane coverage ratio could achieve the optimal value of 0.21 as the droplet diameter was 0.05 mm. Furthermore, the wet-bulb efficiency of the IEC with a size of 260 × 400 × 400 mm3 could reach a maximum value of 52%, supported by two spray nozzles 160 mm apart with a droplet size of 0.05 mm.

Abstract

This paper focuses on development of a full- scale heat injection experiment to investigate the feasibility of an Advanced Geothermal Energy Storage (AGES) system using an existing oil well in Illinois. AGES systems hold a significant potential to provide renewable and sustainable energy development and decarbonizing the oil and gas industry. The field experiment included sealing of the well and injection of a heated brine into the targeted heat storage formation. Temperature data were collected during the experiment using a Distributed Temperature Sensing (DTS) system and were analyzed over a period of 15 days. The results are interpreted and presented. The results indicate that implementing an AGES system is feasible.

Abstract

The UN demands that the world community has to change the current unsustainable consumption and production patterns to achieve a green economy with significantly lower CO2 emissions to meet the Paris Agreement [1, 2]. For the transformation of the current unsustainable consumption and production patterns, currently two narratives are being discussed [3]: Ecomodernism and Degrowth. A dynamic 2- country Computable General Equilibrium (CGE) Model is used to analyze the two green economy approaches. Country A represents the Ecomodernism pathway to a green economy and country B is on a Degrowth path. To analyze these two approaches, a de-growth wedge is developed, which is based on the Harberger triangle [4-6]. The de-growth scenario can be seen as a distortion to the current market economy. The wedge measures the excess burden of welfare losses against the background of the traditional economic model represented by the Ecomodernism approach. The results of our stylized economic model for the Ecomodernism path of country A and for the Degrowth path of country B show a continuing spread of the economic development of the two countries. The results showed that especially the FEW-nexus has to deal with increasing challenges. An aggravating factor is that the cross-country FEW-Nexus has to be managed against the background of two different green economy approaches: Ecomodernism and Degrowth.

Abstract

When waste heat is recovered from vehicle exhaust gas at medium and high temperatures, using a unileg thermoelectric module (TEM) can effectively reduce thermal stress and increase its lifespan. To simultaneously maximize power generation and minimize the thermal stress of a unileg TEM, this study combines the Taguchi method and ANOVA to design the TEM, and a new objective function of the output power/thermal stress (P/S) ratio is conducted to find its maximum value. The Taguchi method considers four geometrical factors, including TE leg geometry, TEM height, copper thickness, and ceramic thickness, with four levels. The analysis suggests that the optimal geometric design considers the Rectangular geometry as the TE leg, a TEM height of 1 mm, a copper substrate thickness of 0.8 mm, and a ceramic thickness of 0.9 mm, yielding a P/S value of 0.01255 W·MPa-1 with the maximum output power and thermal stress of 2.9 W and 232.32 MPa, respectively. The optimized case increases the P/S value by 1.29%. The ANN in this study achieves the average error values of 1.61% and 0.35% for the predictions of dual objective functions by multiple-step optimization. The relative errors of predicted P/S value and conversion efficiency by ANN under the Taguchi method suggestion optimal combination are 2.8% and 0.55%, respectively.

Abstract

This paper focuses on providing insights and knowledge on repurposing abandoned oil and gas wells for geothermal applications. Abandoned wells emit alarming amounts of greenhouse gases and pose serious health hazards and they require a thorough procedure for decommissioning for two reasons. The ordinary cement used in sealing of the wells used in decommissioning deteriorates with time and often leak harmful These obstacles can be addressed by retrofitting abandoned wells for geothermal energy utilization. This paper presents a comprehensive overview on the available conversion technologies, available case studies along with challenges and opportunities pertaining to repurposing for geothermal development. The proposed technology presents an attractive alternative that will reduce the overall costs of developing a geothermal system and decrease the negative environmental impact of abandoned oil and gas wells.