Liquid hydrogen is a high-specific-impulse propellant which is widely used in aerospace. Hydrogen storage is a key problem in the long-distance space exploration. In recent years, zero boil-off (ZBO) storage of cryogenic propellants (LH2, LO2, LCH4) is a significant storage technology for space exploration where the cryocooler is used to achieve ZBO. However, it is difficult to achieve the large cooling capacity at 20 K in space. The reverse turbo-Brayton cycle cryocooler has the obvious advantages of large cooling capacity, low vibration, high reliability and long life which is used as the cryocooler in ZBO system. In this study, a reverse turbo-Brayton cycle cryocooler combining nitrogen and helium cycles is designed to provide the cooling capacity at 20 K and 90 K for liquid hydrogen and liquid oxygen. The nitrogen cycle in the system can provide the cooling capacity of 20 W at 90 K for liquid oxygen storage while the helium cycle in the system can provide the cooling capacity of 5 W at 20 K for liquid hydrogen storage. There are three centrifugal compressors and one expander in the nitrogen cycle. The expander is coaxial with the one of compressors which can recover the expansion work. There are four centrifugal compressors and one expander in the helium cycle. A heat exchanger is used to connect the nitrogen cycle and helium cycle. The nitrogen cycle can provide the cooling capacity for the pre-cooling of the helium cycle. In addition, the cryocooler can also provide the cooling capacity of 200 W at 90 K for liquid oxygen and 200 W at 120 K for liquid methane by the nitrogen cycle. The reverse turbo-Brayton cycle cryocooler in this study can achieve the ZBO storage of liquid hydrogen, oxygen and methane in space. This work can provide the theoretical guidance for the design of ZBO storage in the long-distance space exploration.
The reduction of waste heat in energy intensive industrial processes in combination with digital technologies will play a key role for the development and decarbonization of modern industrial energy systems. In the last few years, a significant share of the CO2 related to energy was emitted by the industry sector. Since industrial processes often are batch processes, waste heat recovery in these processes requires thermal energy storage systems for closing the temporal gap between energy supply and demand. The ongoing digitalization in the field of industrial energy systems enables modern applications like digital twins to increase the efficiency of energy intensive processes. This paper presents the implementation of a five-dimensional digital twin platform for a packed bed thermal energy storage test rig. The five-dimensional digital twin platform allows the development of services and applications in interdisciplinary teams and facilitates their interaction on a standardized platform. By that the digital twin helps to make modern industrial energy systems more efficient.
Co-gasification technology provides a feasible solution for the energetic valorization of various types of biomass feedstocks, especially those not directly applicable for gasification owing to their low-calorific values or high ash content. Numerical modelling is a promising approach to evaluate the performance and analyze the conversion processes inside the gasifier, but the complexity of cogasification technology has put forward challenges to the model formulation. This paper established the Multiple Thermally Thick Particle (MTTP) model for simulating the co-gasification process. MTTP model could not only calculate the individual conversion processes of different fuels, but also simultaneously reflect the characteristics of thermally thick particles and the interactions between different fuels through sub-grid models for the solid phase. Experimental results of a downdraft fixed-bed co-gasification from literature were adopted for model validation. The modelling results from the MTTP model are in good agreement with the measured values of temperature and syngas composition upon changing the co-gasification ratio (CGR). Further analysis of the weight-loss process of different fuel particles and the corresponding intraparticle temperature distribution have confirmed the different conversion characteristics and interactions between different fuels during co-gasification process.
Liquid hydrocarbons made from crude oil serve many functions: (1) a dense, easy-to-store, easy-to-transport energy source, (2) a method for daily-to-seasonal energy storage, (3) a chemical feedstock, (4) a chemical reducing agent and (5) a method to enhance high-temperature heat transfer in many furnaces and industrial processes. There are multiple methods to produce and use liquid hydrocarbons without increasing atmospheric carbon dioxide levels including (1) negative carbon emissions to balance carbon dioxide releases from burning crude-oil products and (2) producing liquid hydrocarbons from non- fossil feedstocks such as carbon dioxide or biomass. Understanding liquid hydrocarbon demand is the starting point in assessing options for producing and using liquid hydrocarbons without increasing atmospheric carbon dioxide levels. Our assessment is that U.S. demand for liquid hydrocarbons is unlikely to go below the equivalent of 10 million barrels per day of crude oil. The costs to replace liquid hydrocarbons increases rapidly at lower liquid hydrocarbon consumption rates. Hydrocarbon biofuels from cellulosic feedstocks can meet such demands but options based on more limited feedstocks (bio oils, sugars, etc.) can’t meet such demands.
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.
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.
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.
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.
Waste heat recovery (WHR) based on thermoelectric generators (TEG) could improve energy efficiency and reduce carbon emissions. TEG could directly convert low-grade heat into electric energy. There have been many reports on laboratory experiments on evaluating the performance of TEG by measuring the power output at different conditions. However, there have been few field tests using waste heat with a temperature of less than 100 °C with TEG devices, which is of great significance because there is huge waste heat within this temperature range. TEGs were usually and mostly used for low-power microelectronic devices. In these cases, only one or several instead of hundreds of TEG modules were utilized. In this study, we conducted the field tests of TEG using the waste heat with a temperature of 80 °C at a gas power plant located in Shanxi province, China. We tested two TEG devices with 10 (240 TEG modules) and 20 layers (360 TEG modules), respectively. To our best knowledge, the number (20) of layers in one TEG device is the biggest so far reported in the literature. The field test results were analyzed and compared with laboratory experiments and other field tests at a high temperature of 170 °C. The power output and efficiency of TEG were measured and calculated at different temperature differences and flow rates. The TEG device could provide a power of 167.8 W for a flow rate of 3 cubic meter per hour at a temperature difference of 60 °C (the temperature of the heat resource was 80 °C). The cost of TEG device used in the field tests was estimated and compared with other power generation technologies. The field test results in this study demonstrate the feasibility of using TEG for recovering large scale waste heat.
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.