Deliverable Energy Research Articles

Effects of interlayer space engineering and surface modification on the charge storage mechanisms of MXene nanomaterials: A review on recent developments.

Two-dimensional MXenes were discovered in 2011 and, because of their outstanding properties, have attracted significant attention as electrode materials for supercapacitors, rechargeable batteries, and hybrid energy storage devices. Numerous studies were dedicated to identifying feasible charge storage mechanisms in MXenes and investigating the effects of structural and superficial properties on the corresponding mechanisms. The results clarify that interlayer distance and surface termination groups in MXenes significantly determine the deliverable energy and power density in respective energy storage devices. Additionally, due to van der Waals interactions, adjacent MXene sheets tend to aggregate and restack during electrode preparation or charge and discharge cycling, reducing the MXene interlayer distance and deteriorating its energy storage ability. In this review, we first summarize the different charge storage mechanisms applicable to MXenes in different energy storage devices and describe the effect of interlayer spacing and surface termination groups. Then, different interlayer space engineering methods are reviewed in terms of materials and procedures, and their impact on the electrochemical behavior and restacking tendency of MXene is described.

Accurate Identification of Critical Boundary Hyperplanes of Practical Steady-State Security Region in Distribution Grids

The practical steady-state security region (PSSR) in distribution grids describes the region where the power flow can be managed securely. The PSSR is irrelevant to operation states and its boundaries can be approximated by hyperplanes (HPs). Benefit from these, the PSSR can dramatically simplify complicated optimal scheduling problems, such as deliverable energy flexibility scheduling. However, calculating the PSSR boundaries corresponding to all the power flow security constraints indiscriminately will theoretically produce lots of HPs to bound the whole PSSR and thus make solving of the PSSRbased optimal scheduling challenging. In fact, the whole PSSR is the intersection of the regions bounded by all the HPs within practical power injection ranges, and only a few HPs, called the critical boundary hyperplanes (CHPs), can bound it. Therefore, it is necessary to identify the CHPs before applying them to the optimal scheduling as power flow security constraints, so as to accelerate the solution. In this paper, a fast and accurate method is first proposed to identify the CHPs. The identified results are irrelevant to the specific objective and can be applied to different optimal scheduling problems. The proposed method is applied to several case-study networks and the results demonstrate its effectiveness and speed.

Comparative Study of Wind Energy Potential Estimation Methods for Wind Sites in Togo and Benin (West Sub-Saharan Africa)

The characterization of wind speed distribution and the optimal assessment of wind energy potential are critical factors in selecting a suitable site for wind power plants (WPP). The Weibull distribution law has been used extensively to analyze the wind characteristics of candidate WPP sites, and to estimate the available and deliverable energy. This paper presents a comparative study of five wind energy resource assessment methods as they applied to the context of wind sites in West Sub-Saharan Africa. We investigated three numerical approaches, namely, the adaptive neuro-fuzzy inference system (ANFIS), the multilayer perceptron method (MLP), and support vector regression (SVR), to derive the distribution law of wind speeds and to optimally quantify the corresponding wind energy potential. Next, we compared these three approaches to two well-known Weibull distribution law-based methods: the empirical method of Justus (EMJ) and the maximum likelihood method (MLM). Case study results indicated that the neural network-based methods, ANFIS and MLP, yielded the most accurate distribution fits and wind energy potential estimates, and consequently, are the most recommended methods for the wind sites in Togo and Benin. The orders of magnitude of the root mean squared error (RMSE) in estimating the recoverable energy using ANFIS were, respectively, 10-4 and 10-5 for Lomé and Cotonou, while MLP achieved an RMSE order of magnitude of 10-3 for both sites.

Computational insights into the energy storage of ultraporous MOFs NU-1501-M (M = Al or Fe): Protonization revealing and performance improving by decoration of superalkali clusters

In 2020, Chen et al. reported the synthesis of a series of promising metal–organic frameworks (MOFs) based on Al/Fe trinuclear clusters, known as NU-1501-M (M = Al or Fe). Both the gravimetric and volumetric Brunauer-Emmett-Teller (BET) areas of this novel structure are in an ideal range, making it highly promising for hydrogen storage. However, the physical chemistry of its adsorption processes has not been investigated. In this work, we applied grand canonical Monte Carlo (GCMC), density functional theory (DFT), and ab initio molecular dynamics (AIMD) to study their adsorption behaviours in details. These simulations suggest that the balance between the chemical porosity and the electronic structure is critical in determining the quality of the designed MOFs materials in deliverable energy storage. Moreover, theoretical predictions reveal the possible protonization of oxygen atoms from M trinuclear nodes by hydrogen molecules. To protect MOFs from being protonized, we proposed to employ NAl3 clusters to decorate the MOFs. Simulations reveal that this novel strategy can not only stablize the oxygen atoms, but also significantly improve the hydrogen storage performance by almost one order of magnitude. Our work proposes an important and promising way to improve the energy storage performance of these MOFs.

Transmission Laser Welding of Similar and Dissimilar Semiconductor Materials

AbstractLaser micro‐welding is an advanced manufacturing method today applied in various domains. However, important physical limitations have prevented so far to demonstrate its applicability in silicon (Si) and other technology‐essential semiconductors. Concentrating on circumventing the optical limits on the deliverable energy density at interfaces between narrow‐gap materials with intense infrared light, the first feasibility demonstration of transmission laser welding between Si workpieces using nanosecond laser pulses is made. A shear joining strength of 32 ± 10 MPa which compares very favorably to the complex process alternatives is obtained. Supported by experiments repeated on different material combinations including gallium arsenide, it is confirmed that this remarkable performance level is achievable for similar and dissimilar semiconductors. The demonstrations rely on a small footprint fiber laser, an aspect that holds great promises for the advent of a high‐efficiency flexible process beneficial for important technology developments including lab‐on‐a‐chip and hybrid semiconductor systems.

Molecularly engineered organic copolymers as high capacity cathode materials for aqueous proton battery operating at sub-zero temperatures

High-performance aqueous all-organic rechargeable batteries are promising candidates for cost-effective, safe, and environment-friendly next-generation energy storage devices. Herein, two organic copolymers with nanorod-like morphology (AN-TA, and AN-PA), composed of different tertiary amines, are synthesized as the cathode material for an aqueous proton battery. The individual copolymer electrodes possess the dominated diffusion-controlled electrode kinetics resulting from the proton insertion/de-insertion along with the surface-controlled processes in 2 M HCl and 2 M H2SO4. Among the two copolymers, AN-PA exhibits the maximum specific capacity of 145 mAh g−1 at 1 A g−1 and then, even at the higher current density of 10 A g−1, it possesses the capacity as 110 mAh g−1 in 2 M HCl. The assembled aqueous proton battery comprising of AN-PA as a cathode delivers the capacity of 80 mAh g−1 at 1 A g−1 in 2 M HCl. The maximum deliverable energy density of 33.9 Wh kg−1 is achieved at the power density of 423 W kg−1. Notably, our proton battery can well operate at the sub-zero temperature of −25 °C with a cell voltage of 1.1 V. More importantly, the device retains 84 % of the initial capacity after 1000 cycles at 2 A g−1 and exhibits the retention of specific capacity of about > 93% when compared to that of room temperature.

A 250 kWh Long-Duration Advanced Iron-Chromium Redox Flow Battery

The electricity generation cost using renewable resources has been reduced to such a low level that it is possible to replace all the fossil fuel-based energy with renewables soon. However, the intermittent property with most renewables, such as solar and wind, requires vast amount, flexible and affordable energy storage products. None of the current widely used energy storage technologies can meet these requirements.An aqueous-based true redox flow battery has many unique advantages, such as long lifetime, safe, non-capacity decay, minimal disposal requirement, and flexible power and energy design. All these make it a great candidate for the vast renewable energy storage market. The key issue with this technology is the cost and availability of the energy-storage media. Due to the limited vanadium resources, it is difficult for the widely studied vanadium-based redox flow battery to be commercially used for fast-growing renewable energy storage market.Iron-chromium redox flow battery was invented by Dr. Larry Thaller’s group in NASA more than 45 years ago. The unique advantages for this system are the abundance of Fe and Cr resources on earth and its low energy storage cost. Even for a mixed Fe/Cr system, the electrolyte cost is still less than 10$/kWh. The major issue with this system is the continuous capacity decay due to hydrogen generation, which makes this system impractical for long-term operations.In the past two years, this limiting problem was successfully solved by researchers at Creek Channel, Inc.1,2 By using a special system design, the hydrogen generation level was largely reduced, down to less than 0.5% per full cycle. A capacity recovery system was also successfully developed, which can compensate the system capacity loss due to hydrogen generation. More than 1000 cycles of operation have been carried out using a system with a kW-scale stack and 100 L electrolyte over a few months. Stable system capacity and stable continuous operation were successfully achieved.With these breakthrough results, a demonstration project of 30 MWh capacity using containerized product is being developed at Lion Creek Co. Ltd. For a 20’ ISO container-sized product, the deliverable energy is 250 kWh, and the max discharge capacity is 35 kW. For a Two 40’ ISO container-sized product, by using a hybrid design integrating with a 200 kW and 100 kWh Li-ion battery, the deliverable energy is 1100 kWh, and the long-duration discharge power can be as high as 330 kW. Larger projects can be readily built up using multiple 1.1 MWh units. The cost for such these products is lower than 100$/kWh, and the energy storage cost using this product is less than $0.02/kWh. With this energy storage cost, it is possible to achieve our ambitious 100% renewable energy goal in the near future.In this presentation, detail performance of the 250 kWh battery unit will be discussed. US 10777836 B1. Redox Flow Battery Systems Including a Balance Arrangement and Methods of Manufacture and Operation.US 10826102 B1. Fe-Cr Redox Flow Battery Systems Including a Balance Arrangement and Methods of Manufacture and Operation. Figure 1

A 1 mWh Advanced Iron-Chromium Redox Flow Battery and 200 Kw Li-Ion Battery Hybrid Unit

An aqueous-based true redox flow battery has many unique advantages, such as long lifetime, safe, non-capacity decay, minimal disposal requirement, and flexible power and energy design. All these make it a great candidate for the vast renewable energy storage market. The key issue with this technology is the cost and availability of the energy-storage media. Due to the limited vanadium resources, it is very difficult for the widely studied vanadium-based redox flow battery to be commercially used for fast-growing renewable energy storage market.Iron-chromium redox flow battery was invented by Dr. Larry Thaller’s group in NASA more than 45 years ago. The unique advantages for this system are the abundance of Fe and Cr resources on earth and its low energy storage cost. Even for a mixed Fe/Cr system, the electrolyte cost is still less than 10$/kWh. The major issue with this system is the continuous capacity decay due to hydrogen generation, which makes this system impractical for long-term operations.In the past two years, this limiting problem was successfully solved by researchers at Creek Channel, Inc.1,2 By using a special system design, the hydrogen generation level was largely reduced, down to less than 0.5% per full cycle. A capacity recovery system was also successfully developed, which can compensate the system capacity loss due to hydrogen generation. More than 1000 cycles of operation have been carried out using a system with a kW-scale stack and 100 L electrolyte over a few months. Stable system capacity and stable continuous operation were successfully achieved.With these breakthrough results, a demonstration project of 30 MWh capacity using containerized product is being developed at Lion Creek Co. Ltd. For a 20’ ISO container-sized product, the deliverable energy is 250 kWh, and the max discharge capacity is 35 kW. For a Two 40’ ISO container-sized product, by using a hybrid design integrating with a 200 kW and 100 kWh Li-ion battery, the deliverable energy is 1100 kWh, and the long-duration discharge power can be as high as 330 kW. Larger projects can be readily built up using multiple 1.1 MWh units. The cost for such these products is lower than 100$/kWh, and the energy storage cost using this product is less than $0.02/kWh. With this energy storage cost, it is possible to achieve our ambitious 100% renewable energy goal in the near future.In this poster, we will present our recent progress on the development of a 1 MWh advanced Fe-Cr redox flow battery and 200 kW Li-ion battery hybrid unit. US 10777836 B1. Redox Flow Battery Systems Including a Balance Arrangement and Methods of Manufacture and Operation.US 10826102 B1. Fe-Cr Redox Flow Battery Systems Including a Balance Arrangement and Methods of Manufacture and Operation. Figure 1

Composing Energy Services in a Crowdsourced IoT Environment

We propose a novel framework for composing crowdsourced wireless energy services to satisfy users' energy requirements in a crowdsourced Internet of Things (IoT) environment. A new energy service model is designed to transform the harvested energy from IoT devices into crowdsourced services. We propose a new energy service composability model that considers the spatio-temporal aspects and the usage patterns of the IoT devices. A multiple local knapsack-based approach is developed to select an optimal set of partial energy services based on the deliverable energy capacity of IoT devices. We propose a heuristic-based composition approach using the temporal and energy capacity distributions of services. Experimental results demonstrate the effectiveness and efficiency of the proposed approach.

An Advanced Iron-Chromium Redox Flow Battery

Nowadays, the electricity generation cost using renewable resources has been reduced to such a low level that it is possible to replace most fossil fuel-based energy with renewables in the near future. However, the intermittent property with most renewables, such as solar and wind, requires vast amount, flexible and affordable energy storage products. None of the current widely used energy storage technologies can meet these requirements.An aqueous-based true redox flow battery has many unique advantages, such as long lifetime, safe, non-capacity decay, minimal disposal requirement, and flexible power and energy design. All these make it a great candidate for the vast renewable energy storage market. The key issue with this technology is the cost and availability of the energy-storage media. Due to the limited vanadium resources, it is very difficult for the vanadium-based redox flow battery to be widely used for fast-growing renewable energy storage market.Iron-chromium redox flow battery was invented by Dr. Larry Thaller’s group in NASA more than 45 years ago. The unique advantages for this system are the abundance of Fe and Cr resources on earth and its low energy storage cost. Even for a mixed Fe/Cr system, the electrolyte raw material cost can still be less than 10$/kWh. The major issue with this system is the continuous capacity decay due to hydrogen generation, which makes this system impractical for long-term operations.Here we report our recent results on this system. By using a special system design, the hydrogen generation level was largely reduced, down to less than 0.25% per full cycle. A capacity recovery system was successfully developed, which can compensate the system capacity loss due to hydrogen generation. More than 1000 cycles of operation have been carried out using a system with a kW-scale stack and 100 L electrolyte over a few months. Stable system capacity and stable continuous operation were successfully achieved.With these results, a containerized product is proposed. For a 20’ ISO container-sized product, the deliverable energy is 250 kWh, and the normal and maximum discharge powers are 25 and 50 kW respectively. The cost for such a product is lower than 80$/kWh, and the energy storage cost using this product is less than $0.02/kWh (assuming the product has 15 yr lifetime, and it operates 300 full cycle per year). With this energy storage cost, it is possible to achieve our ambitious 100% renewable energy goal in the near future.

Coordinated deliverable energy flexibility and regulation capacity of distribution networks

The increasing capacity of distributed flexibility resources (DFRs) in power distribution systems provides an unprecedented opportunity for distribution system operators (DSOs) to offer the available distributed flexibility as services in electricity markets. This paper proposes a novel model to define and co-optimize the deliverable energy flexibility and frequency regulation capacity of power distribution systems. The distributed flexibility is provided in distribution buses by flexible loads, modeled by a novel queuing system, energy storage (ES) devices, and distributed solar resources with controllable inverters. The proposed model co-optimizes the DFRs schedule in three operating points that model the operation of flexible loads, distributed solar generation units, and ES devices in distribution networks for providing energy flexibility, as well as regulation up and down capacity in electricity markets. The proposed model takes into account the interdependence between DFRs schedule in the three operating points, which enables the DSO to provide non-conflicting capacity offers to different services in the market. In addition, the proposed model ensures the deliverability of energy flexibility and regulation capacity in the markets by satisfying the power flow constraints of distribution networks in all three operating points. The numerical studies, conducted on the 33-bus test distribution system, demonstrate the effectiveness of the proposed model for scheduling realistic energy flexibility and regulation capacity offers that are deliverable in the markets.

An automatic slope compensation adjustment technique for peak-current mode DC-DC converters

In a current-mode switching DC-DC converter, the amount of deliverable energy to the load depends on the inductor current limit for the safety of the power components and the slope compensation current which is determined by the slope of the inductor current and the switching duty cycle. However, excess or insufficient slope compensation current may reduce the available load current or cause subharmonic oscillations, respectively. This paper presents an input-to-output conversion ratio sensing circuit which sets a proper slope-compensation (SC) current to avoid both excess slope compensation current and subharmonic oscillations. Both the slope and the duty-cycle of the proposed slope-compensation current are automatically adjusted based on the sensed input-to-output conversion ratio. As a result, the maximum available output current and the main-loop bandwidth of the converter are improved by the proposed structure. The compensation current is generated based on a fast (<0.5 μs settling time) sensing circuit to track the input voltage or the load current changes. The proposed slope-compensation circuit was integrated into a boost topology with 0.038 mm2 extra silicon area and 190 μA current consumption.

Implementing Metal-Organic Frameworks for Natural Gas Storage

Methane can be stored by metal-organic frameworks (MOFs). However, there remain challenges in the implementation of MOFs for adsorbed natural gas (ANG) systems. These challenges include thermal management, storage capacity losses due to MOF packing and densification, and natural gas impurities. In this review, we discuss discoveries about how MOFs can be designed to address these three challenges. For example, Fe(bdp) (bdp2− = 1,4-benzenedipyrazolate) was discovered to have intrinsic thermal management and released 41% less heat than HKUST-1 (HKUST = Hong Kong University of Science and Technology) during adsorption. Monolithic HKUST-1 was discovered to have a working capacity 259 cm3 (STP) cm−3 (STP = standard temperature and pressure equivalent volume of methane per volume of the adsorbent material: T = 273.15 K, P = 101.325 kPa), which is a 50% improvement over any other previously reported experimental value and virtually matches the 2012 Department of Energy (Department of Energy = DOE) target of 263 cm3 (STP) cm−3 after successful packing and densification. In the case of natural gas impurities, higher hydrocarbons and other molecules may poison or block active sites in MOFs, resulting in up to a 50% reduction of the deliverable energy. This reduction can be mitigated by pore engineering.

Deliverable Energy Flexibility Scheduling for Active Distribution Networks

This paper proposes a fundamental model for defining and optimizing distributed energy flexibility in distribution buses, as well as deliverable energy flexibility as the aggregate distributed flexibility that is available for offering to the day-ahead energy market by distribution system operators (DSOs), without jeopardizing the operational constraints of the distribution network. The distributed energy flexibility is provided by flexible loads in distribution buses, which are modeled by clustered queuing systems representing the aggregation of large population of flexible loads with different energy and service quality requirements. Further, controllable inverters interfacing distributed solar generation provide reactive power flexibility in distribution buses. The deliverable energy flexibility is optimized by the proposed model that coordinates the energy flexibility of queued flexible loads and controllable inverters to maximize DSO’s profit of participating in the day-ahead energy market, while satisfying the service quality constraints of flexible loads, the operational limits of controllable inverters, and power flow constraints of distribution network that are formulated using the branch flow model. Moreover, an index is proposed to calculate the contribution of each distribution bus in providing the deliverable energy flexibility. The proposed model is implemented on the IEEE 33-bus distribution network. The numerical results exhibit profit opportunities for DSOs from providing the deliverable energy flexibility in the day-ahead energy market.

Optimization of Design Parameters and Operating Conditions of Electrochemical Capacitors for High Energy and Power Performances

Theoretical expressions for performance parameters of different electrochemical capacitors (ECs) were optimized by writing MATLAB scripts to solve them and also via MATLAB R2014a optimization tool box. Performance of different kind of ECs at given circumstances were compared through theoretical equations and simulation of various models subject to conditions of device components, using optimal coefficient associated to battery-kind material and constant associated to electrolyte material KBMopt and KEopt , as well as our symmetric electric double layer capacitor (EDLC) experimental data. Estimations of performance parameters were feasible and achievable once details of electrodes mass ratio, operating potential range ratio and specific capacitance of electrolyte are known. Performances of asymmetric EC with suitable electrode mass and operating potential range ratios using aqueous electrolytes, and that with suitable electrode mass and operating potential range ratios using organic electrolyte with appropriate operating potential range and specific capacitance were factors of 2.2 and 5.56, respectively, greater than those of symmetric EDLC and asymmetric EC using the same aqueous electrolyte, respectively. This enhancement came along with reduction in cell mass and volume. Also, storable and deliverable energies of asymmetric EC with suitable electrode mass and operating potential range ratios using proper organic electrolyte were factor of 12.9 greater than those of symmetric EDLC using aqueous electrolyte, with reduction in cell mass and volume. Storable energy, energy density and power density of asymmetric EDLC with suitable electrode mass and operating potential range ratios using proper organic electrolyte were factor of 5.56 higher than those of similar symmetric EDLC using aqueous electrolyte with reduction in cell mass and volume by a factor 1.77. Also, introduction of asymmetric EDLC with the same type of electrode, and suitable electrodes mass ratio, working potential range ratios and proper organic electrolyte enhanced performance of conventional symmetric EDLC using aqueous electrolyte with reduction in cell mass and volume. These results can obviously reduce number of experiments to determine optimum manufacturing state of EC, and also demonstrated that institution of asymmetric electrode and organic electrolyte was very successful in improving performance of EC with reduction in cell mass and volume. These results can as well be a guideline for design, fabrication and operation of electrochemical capacitor with outstanding storable energy, energy and power densities. Key words: Electrodes symmetry; Modelling and simulation; Performance parameters; Electrolytes type; Working potential range; Asymmetric capacitors.

CASSIOPeiA – A new paradigm for space solar power

Recent debate (Clack v. Jacobson, 2017) argues the feasibility of 100% terrestrial renewables (wind, water, solar) by 2050, on the premise of restricting world consumption to 2012 levels (∼12 TW-years). Given the expected population rise by 3 billion over the same time frame, and the correlation between prosperity and energy availability – are we to impose energy equality, requiring some to reduce consumption by 87%, or are we to condemn the majority to relentless poverty? Choosing neither implies ever-increasing carbon emissions and the risk of catastrophic climate change. Nuclear fission is one energy technology which could be expanded to provide sufficient carbon-free power, but faces widespread opposition from public fear and distrust. Future terrestrial fusion is another, but first pilot operations are not expected until 2050 – which may be too late. We could make much better use of one existing fusion power source, our Sun. The fundamentals of Space Solar Power (SSP) are well understood and could lead to a world of energy abundance; the deliverable energy from just a 10 km geostationary (GEO) band exceeds 570 TW-years – enough to supply ten billion people at six-times current US per-capita levels. Despite this, SSP has languished for fifty years. GEO is one of few candidates for baseload power, but physics dictates a kilometre-scale microwave transmitter irrespective of the power delivered – hence economics favours the multi-gigawatt (per-satellite) engineering limit. Given the complexity of the differentially rotating solar collector, sub-gigawatt SSP suffers both economically and technically, with different solutions required at different scales – which has led to exorbitant (hence prohibitive) start-up costs. CASSIOPeiA breaks this non-scaling paradigm by eliminating the rotating interfaces; all SPS subsystems are able to share one lightweight modular structure, with near-invariant areal power density from sub-megawatt to gigawatt systems. With additional fixed mirror concentrators, CASSIOPeiA can also be expanded into the multi-gigawatt regime. CASSIOPeiA's unique beam-steering capability facilitates baseload delivery from alternative, closer orbits, with the possibility of single payload deployment requiring no on-orbit assembly. By starting with sub-megawatt, near-term stratospheric station-keeping platforms – with retrieval, servicing and transfer of gained knowledge – the era of SSP may commence at much lower risk and expense.

Numerical analysis on 10 MJ solenoidal high temperature superconducting magnetic energy storage system to evaluate magnetic flux and Lorentz force distribution

Due to fast response and high energy density characteristics, Superconducting Magnetic Energy Storage (SMES) can work efficiently while stabilizing the power grid. The challenges like voltage fluctuations, load shifting and seasonal load demands can be accomplished through HTS magnet as this device has a great potential to supply power for a time span varies from few seconds to hours. Solenoidal configuration has been widely employed (over toroidal) in the development of SMES prototypes as it is simpler to manufacture and allows an easier handling of the mechanical stresses imposed on the structure due to Lorentz forces. A micro-SMES of capacity 10 MJ can be employed to mitigate the challenges like load leveling, dynamic stability, transient stability, voltage stability, frequency regulation, transmission capability enhancement, power quality improvement, automatic generation control, uninterruptible power supplies, etc.In this work, solenoidal configuration has been engaged in the development of 10 MJ SMES Magnet using 2 G (SuperPower, YBCO having Tc = 90 K @0T) High Temperature Superconducting (HTS) tape. The superconducting tape has been cooled at 14 K using conduction cooling. The effect of maximum operating current (3250A, 2600A, 1950A and 1300A) on the inductance, maximum storable energy and length of superconductor has also been evaluated for a constant deliverable energy of 10 MJ. A numerical analysis is done on 10 MJ HTS SMES where perpendicular field of 3T has been considered. The effect of aspect ratio (solenoidal height to bore diameter ratio) on the normal component of the magnetic field has also been assessed. Lorentz forces (N/m3) have been evaluated in the superconducting domain. It has been concluded that it would be beneficial to operate at higher currents (i.e. more current through single tape) as it can reduce the total length of the superconductor. The perpendicular component of magnetic flux for the analysis is found to 2.96T which is less than 3T.

(Invited) Fundamental Challenges to Develop High Energy Lithium Sulfur Pouch Cells

The renaissance of Li-S battery technology is evidenced by the intensive research efforts in recent years. Although the theoretical capacity and energy of a Li-S battery is theoretically very high, the projected usable energy is expected to be no more than twice that of state-of-the-art Li-ion batteries, or 500 Wh/kg. The recent “sulfur fever” has certainly gathered new knowledge on sulfur chemistry and electrochemistry, electrolytes, lithium metal, and their interactions in this “old” system; however, a real advance toward a practical Li-S battery is still missing. One of the main reasons is the lacking of fundamental understanding of Li-S batteries at cell levels. The surface/carbon composite, their particle size, sulfur electrode porosity and density critically dictate the deliverable energy from Li-S chemistry, whereas the parasitic reactions on Li metal anode determines the cycling life of the cell. This talk will briefly overviews the recent research progress on Li− S batteries, followed by a discussion of the scientific gap between lab research and realistic conditions of cell fabrication. The future work in Li-S battery research is also explored to propel relevant research efforts to accelerate the market penetration of Li-S batteries.

Green synthesis and characterization of aluminium fumarate metal-organic framework for heat transformation applications

Microporous materials with higher uptake – offtake difference per adsorption – desorption cycle have great potential to design adsorption assisted chillers, heat pumps and thermal batteries. In this context, we report a green reaction method for synthesizing aluminium fumarate (AlFum) metal-organic framework (MOF). The water uptake on AlFum shows S-shape isotherm curve with sharp increase in uptake – offtake difference in a narrow pressure range. The proposed green synthesized AlFum exhibits higher deliverable energy capacity as compared to that of conventional (dimethylformamide based synthesis) AlFum for adsorptive cooling applications.

Maximum lifetime coverage problem with battery recovery effect

Scheduling sensors to prolong the lifetime of target coverage is one of the central problems faced in wireless sensor networks. This problem, called the maximum lifetime coverage problem (MLCP), can be formulated as a linear program with exponential size and has a polynomial-time approximation scheme (PTAS). In reality, however, sensor batteries are subject to the recovery effect, which means that the deliverable energy in a battery can replenish itself if it is left idle for a sufficient duration. Thanks to this effect, we can obtain much longer sensor lifetime if each sensor is intermittently forced to turn off for some interval. In this study, we introduce two models that extend the MLCP to incorporate the battery recovery effect. The first model, called as duty cycle model, represents the battery recovery effect in a deterministic way. The second one, called as linear recovery model, uses a probabilistic model to imitate this effect. We propose two efficient algorithms that work for both models, adapting greedy and Garg–Könemann-based algorithms for the original MLCP. In our numerical experiments, our greedy algorithm performs best in the duty cycle model, while our Garg–Könemann-based algorithm performs best in the linear recovery model. For each network, we compare the longest lifetime obtained from our algorithms with the longest lifetime obtained from algorithms for the original MLCP. As a result, we found that our lifetime is 10–40% longer.