Cycle Scheme Research Articles

A new thermodynamic modeling method for Brayton cycle schemes based on heat flux of the heat source

The supercritical carbon dioxide Brayton cycle is a promising option for power generation. However, the existing models for assessing its performance lack universality for various layouts and rely on challenging-to-acquire thermodynamic parameters at state points (such as the inlet temperature of the turbine). The present study proposes a modular thermodynamic modeling method, making it suitable for various layouts. A parameter-matching method is proposed using the heat flux of the heat source as an input, making it more practical than methods relying on parameters at state points. The method's accuracy is verified with a deviation not exceeding ±1.5%. Subsequently, four typical schemes including simple recuperation, recompression, intercooling, and reheating cycles are analyzed. The effect of heat flux on power generation and thermal efficiency of each scheme is also evaluated. It is found that the simple recuperation cycle is capable of operating effectively within lower thresholds for both maximum pressure and temperature. For maximizing power generation, the intercooling cycle offers an advantage. As for thermal efficiency, the simple recuperation cycle is best suited for heat fluxes under 1.6 MW/m2, while the recompression cycle is recommended for fluxes exceeding this limit. The outcomes can guide the designing and optimization of Brayton cycle schemes.

(Invited) Low Temperature Atomic Layer Deposition Processes for Large-Area Synthesis of 2D Transition Metal Dichalcogenides

2D materials have been the focus of intense research in the last decade due to their unique physical properties. This presentation will highlight our recent progress on the large-area synthesis of two-dimensional transition metal chalcogenides for nanoelectronics using advanced atomic layer deposition cycle schemes. First, how we can use advanced cycle schemes to deposit wafer-scale polycrystalline MoS2 thin films at very low temperatures down to 100 °C. We have identified the critical role of hydrogen during the plasma step in controlling the composition and properties of molybdenum sulfide films. By increasing the H2/H2S ratio or adding an extra hydrogen plasma step to our ALD process, we are able to deposit pure polycrystalline MoS2 films at temperatures as low as 100 °C. To the best of our knowledge, this represents the lowest temperature for crystalline MoS2 films prepared by any chemical gas-phase method.[1]The most dominant methods for preparing MoS2 via ALD is to alternately expose a substrate to a metalorganic precursor and a hydrogen sulfide (H2S) or a plasma containing H2S. H2S is a corrosive, toxic, and flammable gas that is heavier than air, which makes it hazardous and expensive to store, install, and transport. Alternative sulfur precursors in the solid or liquid phase would be beneficial in terms of cost and safety and would require the installation of no additional hardware for most ALD reactors. In the second half of this contribution, the widely researched ALD process using bis(tert-butylimido)bis(dimethylamino)molybdenum(IV) ((tBuN)2(NMe2)2Mo) and H2S plasma is compared to a novel ALD process using (tBuN)2(NMe2)2Mo, hydrogen plasma, and di-tert-butyl disulfide (TBDS), which is an inexpensive, liquid-phase sulfur precursor.[1] M. Mattinen et al., Chem. Mater. (2022), 34, 5104

Life-cycle assessment of hydrogen produced through chemical looping dry reforming of biogas

Chemical looping dry reforming of methane (CLDRM) using perovskites as a catalyst is considered a promising option for producing hydrogen from biogas. In this work, the life-cycle performance of a system compiling a CLDRM unit paired with a water gas shift unit, a pressure swing adsorption unit, and a combined cycle scheme to provide steam and electricity was assessed. The main data needed to reflect the behavior of the reforming reaction was obtained experimentally and implemented in an Aspen Plus® simulation. Inventory data was obtained through process simulation and used to assess the environmental performance of the process in terms of carbon footprint, acidification, freshwater eutrophication, ozone depletion, photochemical ozone formation, and depletion of minerals and metals. Overall, the environmental viability of the production of green hydrogen from biogas was found to be heavily dependent on the biogas leakage in anaerobic digestion plants. The CLDRM system was benchmarked against a conventional DRM implementation for the same feedstock. While the conventional DRM plant environmentally outperformed the perovskite-based CLDRM, the latter might present advantages from an implementation point of view.

Thermodynamic analysis of a hybrid ammonia-water refrigeration cycle with low-temperature solar heat

The performance of a solar-driven single-effect ammonia absorption refrigeration unit was studied numerically and experimentally. The thermal performance and unit operation status of small refrigerators were studied under various designing and operating conditions. A thermodynamic cycle scheme of hybrid ammonia-water refrigeration (HAWR) is proposed to operate in parallel with the compressor and ammonia absorption refrigeration, and the performance of the thermodynamic circulation system is evaluated by considering the thermodynamic coefficient and thermodynamic refrigeration ratio as evaluation indexes. Aspen Plus simulation software was introduced to simulate the HAWR and optimise the operation strategy. The results indicate that adjusting the compressor outlet pressure can stabilise the refrigeration capacity of the ammonia refrigeration system. The optimised working point pressure is 600 kPa, while the corresponding evaporation, condensation, absorption, and generation temperatures are 15 °C, 40 °C, 42 °C, and 85 °C respectively, the thermodynamic coefficient is 0.307, and the thermodynamic refrigeration ratio is 0.443. Under the rated cooling conditions, 44.3 % of the cooling capacity is driven by solar energy, and 55.7 % is driven by electric energy in the optimal working state. Under non-optimal working conditions, the proportion of the cooling capacity driven by electric energy is as high as 79.5 %. Under the conditions of sunny weather and with the absence of the compressor, the cooling capacity increases from 2.5 to 7.5 kW as the radiation intensity increases from 600 to 950 W/m2, while the system performance tends to be stable and the coefficient of performance maintains around 0.738 as the irradiation intensity exceeds 800 W/m2.

Implementation of thorium-based fuel for Indonesia Micro Reactor (IMR)

Indonesia has committed to reducing greenhouse gas emissions in the framework of net zero emissions, and nuclear energy will be a part of the energy mix. Indonesia has been developing a 10 MWt micro reactor of high temperature gas-cooled reactor (HTGR) with pebble fuel containing 17 % enriched UO2 kernel with OTTO cycle scheme. For the government’s interest to use thorium, this paper assesses the possibility of replacing uranium with thorium. The assessment is performed by calculating the effective neutron multiplication factor (keff). Neutrons captured by 232Th lead to the formation of two intermediate isotopes, namely 233Th and 233Pa, the latter being a significant neutron absorption cross-section. Neutronics analysis is performed using parameters of thorium mass fraction, core temperature, and active core height. The thorium mass fractions varies from 0 % to 90 % Th. The core temperatures are in the range of the normal operating temperature at 900 K, assumed superheat temperature at 1200 K, and shutdown temperature at 300 K. The active core height varies at 197, 180, 150, 130, and 125 cm. This paper aims to determine the keff of the IMR at maximum thorium/uranium mass fraction composition, maximum active core height, core temperature, and fuel burn-up. The MCNP code is used for analysis. The results show that keff decreases with increasing thorium mass fraction and core temperature, and decreasing active core height. Calculations with thorium mass fraction of 15 %, core active height of 197 cm in 20 steps show that the reactor may be continuously operated for more than 920 days without refueling. The analysis results show that IMR design has negative temperature reactivity, inherent safety characteristics, and the ability to use thorium-based fuels.

Optimized dual-gas co-production from hydrate reservoirs with underlying gas through depressurization & well closure cycling: An experimental evaluation

The regular depressurization method for the exploitation of natural gas hydrate, while effective in gas production, carries a high risk of hydrate regeneration and significant reservoir shrinkage. In this study, the hydrate reservoirs containing underlying gas were synthesized by controlling the initial water distribution, and confining pressure was applied to replicate sub-seafloor conditions. An innovative cyclic depressurization (DP) + well closure (WC) cycling scheme was implemented to facilitate the joint production of hydrate and underlying gas. The heat transfer, gas production, and sediment deformation characteristics during dual-gas co-production were compared and examined considering different DP and WC duration. The findings clearly indicate that the DP + WC cycling method yielded significantly superior results compared to the regular DP approach. Specifically, it achieved effective CH4 recovery rates 1.83–2.33 times higher, temperature recovery rates 1.2–1.3 times greater, and a reduced the duration of reservoir contraction. More importantly, the extent of influence on these factors could be controlled by adjusting DP or WC duration. A discovery like this offers diverse gas production approaches tailored to various hydrate reservoir requirements. Overall, this study provides preliminary evidence that the DP + WC cycling method allows for the simultaneous attainment of efficient production and reservoir security, highlighting its potential significance for gas production from hydrate reservoirs containing underlying gas.

Thermodynamic, exergetic and environmental evaluation and optimization of a bio-fuel fired gas turbine incorporated with wind energy derived hydrogen injection

The fluctuating nature of wind energy and shortage of biomass resources, as two types of renewables, can be fulfilled via their hybridization. In this respect, present research proposes a hybrid biomass/wind energy driven power generation framework based on combined gas turbine-Rankine cycle scheme. The gas turbine includes a reheat stage where the produced hydrogen is added to the combustion chamber for increasing flue gas temperature to enhance output power. The injected hydrogen is generated via a water electrolyzer which is powered by electricity from the wind turbines. The proposed scheme of biomass/wind powered system leads to a reduction in biomass consumption and will fulfill the fluctuations and non-continuous availability of wind energy. To appraise the feasibility of developed hybrid scheme, thermodynamic first and second law-based analyses were performed. Also, the exergo-environmental evaluation of the hybrid plant is conduced using three exergo-environmental indices. Finally, optimum operation conditions of the proposed hybrid plant is determined based on the minimization of environmental damage index. The results under optimum operation indicate that, the proposed hybrid power generation plant yields exergy efficiency of 47.35 % with environmental damage index of 0.0104.

Two-dimensional electronic spectroscopy from first principles

The recent development of multidimensional ultrafast spectroscopy techniques calls for the introduction of computational schemes that allow for the simulation of such experiments and the interpretation of the corresponding results from a microscopic point of view. In this work, we present a general and efficient first-principles scheme to compute two-dimensional electronic spectroscopy maps based on real-time time-dependent density-functional theory. The interface of this approach with the Ehrenfest scheme for molecular dynamics enables the inclusion of vibronic effects in the calculations based on a classical treatment of the nuclei. The computational complexity of the simulations is reduced by the application of numerical advances such as branching techniques, undersampling, and a novel reduced phase cycling scheme, applicable for systems with inversion symmetry. We demonstrate the effectiveness of this method by applying it to prototypical molecules such as benzene, pyridine, and pyrene. We discuss the role of the approximations that inevitably enter the adopted theoretical framework and set the stage for further extensions of the proposed method to more realistic systems.

THE RESULTS OF THE APPROBATION OF METHODS OF SYNCHRONIZATION OF LIBIDO SEXUALIS OF HITSYNCH AND OVSYNCH ON COWS OF MEAT PRODUCTIVITY

The article presents data on the comparative effectiveness of synchronization schemes of the sexual cycle in cattle using the Hitsynch and Ovsynch methods, various GnRH, prostaglandin F2a, and estrogens were used in synchronization schemes to activate sexual processes and increase fertilization. In order to increase their effectiveness, biologically active substances were included in the synchronization schemes. The aim of the study was to determine the effectiveness of various synchronization schemes when biologically active substances are included in them. The authors note that stimulation of the genitals using the methods of synchronization of sexual libido of Hitsynch and Ovsynch with the additional inclusion of biologically active substances in the schemes significantly improves the arrival of cows in libido and increases fertilization. These indicators were more pronounced when synchronizing sexual libido using the Hitsynch method. The novelty of the conducted research is the determination of effective modern schemes of synchronization of sexual libido. It was found that the complex use of hormonal drugs "Surfagon", "Oestrophan" biologically active substances vitamin complex "Tetravit" and estrogenic hormone ECP activates the manifestation of sexual processes stimulates the manifestation of sexual libido and increases the fertilization of cows.

The laser‐cooling of low‐lying states of gold‐aluminum MRCI+Q study including spin‐orbit coupling

AbstractThe possible laser cooling of AuAl molecules was investigated using high‐level ab initio calculations and considering the spin‐orbit coupling effect. Multi‐reference configuration interaction and the Davidson correction were also employed. Six Λ‐S electronic states were obtained, which were divided into 14 Ω states via spin‐orbit coupling. The optical transition showed potential for laser‐cooling applications owing to its highly diagonal Franck‐Condon factors and larger vibrational branching ratios. A possible optical cycling scheme using four lasers at near‐resonance wavelengths to eliminate vibrational branching loss is proposed. This scheme can be experimentally tested in future laser‐cooling experiments.

(Invited) Advanced Atomic Layer Deposition Cycle Schemes for Large-Area Synthesis of 2D Transition Metal Dichalcogenides

2D materials have been the focus of intense research in the last decade due to their unique physical properties. This presentation will highlight our recent progress on the large-area synthesis of two-dimensional transition metal chalcogenides for nanoelectronics using advanced atomic layer deposition cycle schemes. First, how we can use advanced cycle schemes to deposit wafer-scale polycrystalline MoS2 thin films at very low temperatures down to 100 °C. We have identified the critical role of hydrogen during the plasma step in controlling the composition and properties of molybdenum sulfide films. By increasing the H2/H2S ratio or adding an extra hydrogen plasma step to our ALD process, we are able to deposit pure polycrystalline MoS2 films at temperatures as low as 100 °C. To the best of our knowledge, this represents the lowest temperature for crystalline MoS2 films prepared by any chemical gas-phase method.[1]ALD-grown 2D films tend to exhibit a high density of out-of-plane 3D structures in addition to 2D horizontal layers. While the out-of-plane 3D structures are ideal for catalysis applications, the presence of such 3D structures can hinder charge transport, which hampers device applications. In this presentation I will show how we used mechanistic insight obtained by HRTEM to tune the shape and density of the 3D structures during plasma-enhanced ALD using advanced atomic layer deposition schems. The obtained morphology control was further confirmed by electrical measurements.[2]Earlier [3] we have shown that ALD is an excellent technique to make MoxW1-xS2 alloys with precise control over the alloy composition. Here, I will focus on how (plasma-enhanced) atomic layer deposition can aid in synthesizing doped 2DTMCs with precise control over the doping concentration by using elaborate ALD dosing schemes.[1] M. Mattinen et al., Chem. Mater. (2022), 34, 5104[2] S. Balasubramanyam, et al. ACS Appl. Mater. Interfaces (2020), 12, 3873[3] J. J. P. M. Schulpen et al. 2D Mater. (2022), 9, 025016

A multi-index evaluation method of supercritical CO2 Brayton cycle for nuclear power plants design

ABSTRACT This paper investigated four different S-CO2 Brayton cycle layouts for nuclear energy conversion: simple recuperation cycle (SR), recompression cycle (RC), re-heating cycle (RH), and intercooling cycle (IC). We compared these S-CO2 Brayton cycle schemes for nuclear energy conversion using the G1+TOPSIS multi-index evaluation method. The evaluation results of different schemes based on their safety, thermodynamics, techno-economic and compactness are given. The results show that for Generation IV reactors with the same designed thermal power, the thermodynamic performance of the S-CO2 system is better for higher reactor exit temperature. Among the schemes, the gas-cooled fast reactor (GFR)+RC scheme has the highest thermal efficiency (47.4%) and exergy efficiency (56.48%). The GFR+IC scheme has the lowest specific cost (1861.3$/W) and the internal rate of return (24.8%). The re-heating cycle (RH) has worse indexes, but it requires the lowest initial investment cost. The intercooling cycle (IC) has the lowest levelized cost of electricity (0.0134 $/KW•h) coupling to GFR. Considering all indexes of four aspects, the reactor’s performance ranking is MSR>LFR>SFR>GFR, and the S-CO2 system's performance ranking is RC>SR>IC>RH. For Generation IV nuclear energy conversion technologies, the molten salt reactor (MSR)+RC scheme should be given priority, while GFR+RH schemes should be carefully considered.

Improving nitrogen cycling in a land surface model (CLM5) to quantify soil N2O, NO, and NH3 emissions from enhanced rock weathering with croplands

Abstract. Surficial enhanced rock weathering (ERW) is a land-based carbon dioxide removal (CDR) strategy that involves applying crushed silicate rock (e.g., basalt) to agricultural soils. However, unintended biogeochemical interactions with the nitrogen cycle may arise through ERW increasing soil pH as basalt grains undergo dissolution that may reinforce, counteract, or even offset the climate benefits from carbon sequestration. Increases in soil pH could drive changes in the soil emissions of key non-CO2 greenhouse gases, e.g., nitrous oxide (N2O), and trace gases, e.g., nitric oxide (NO) and ammonia (NH3), that affect air quality and crop and human health. We present the development and implementation of a new improved nitrogen cycling scheme for the Community Land Model v5 (CLM5), the land component of the Community Earth System Model, allowing evaluation of ERW effects on soil gas emissions. We base the new parameterizations on datasets derived from soil pH responses of N2O, NO, and NH3 in ERW field trial and mesocosm experiments with crushed basalt. These new capabilities involve the direct implementation of routines within the CLM5 N cycle framework, along with asynchronous coupling of soil pH changes estimated through an ERW model. We successfully validated simulated “control” (i.e., no ERW) seasonal cycles of soil N2O, NO, and NH3 emissions against a wide range of global emission inventories. We benchmark simulated mitigation of soil N2O fluxes in response to ERW against a subset of data from ERW field trials in the US Corn Belt. Using the new scheme, we provide a specific example of the effect of large-scale ERW deployment with croplands on soil nitrogen fluxes across five key regions with high potential for CDR with ERW (North America, Brazil, Europe, India, and China). Across these regions, ERW implementation led to marked reductions in N2O and NO (both 18 %), with moderate increases in NH3 (2 %). While further developments are still required in our implementations when additional ERW data become available, our improved N cycle scheme within CLM5 has utility for investigating the potential of ERW point-source and regional effects of soil N2O, NO, and NH3 fluxes in response to current and future climates. This framework also provides the basis for assessing the implications of ERW for air quality given the role of NO in tropospheric ozone formation, as well as both NO and NH3 in inorganic aerosol formation.

Assessing Cycling Accessibility in Urban Areas through the Implementation of a New Cycling Scheme

Cycling’s integration into the intricate facets of urban design, together with walking and public transportation, offers an effective solution to the mobility issues plaguing urban spaces, and is critical to the sustainability of modern cities. In this context, in this research urban cyclists’ needs and preferences are analyzed through questionnaires, and bicycle accessibility to urban areas is assessed using multicriteria analysis. The public’s familiarity with the integration of novel mobility solutions (e.g., e-bicycles) that support accessibility and inclusiveness is tested and analyzed by recording cyclists trajectories on bicycle routes. The European hub of Patras was selected as the case study for a pilot scheme in this analysis. Similar to many medium-sized European cities, several mobility obstacles, including urban topography, hinder bicycle accessibility in the city, especially between the Modern and Old City areas. The research findings indicate that, addressing these obstacles, electric bicycles can substantially increase bicycle accessibility in the city center. The public usage of electric bicycles is encouraged in the pilot study, and the results indicate that it can increase accessibility to urban areas while reducing restrictions related to age, physical condition, and disabilities. Providing citizens access to e-bicycles can increase the number of daily bicycle users, leading to positive impact in urban cohesion, resilience, and sustainability.

A parallel geometric multigrid method for adaptive topology optimization

This work presents an efficient parallel geometric multigrid (GMG) implementation for preconditioning Krylov subspace methods solving differential equations using non-conforming meshes for discretization. The approach does not constrain such meshes to the typical multiscale grids used by Cartesian hierarchical grid methods, such as octree-based approaches. It calculates the restriction and interpolation operators for grid transferring between the non-conforming hierarchical meshes of the cycle scheme. Using non-Cartesian grids in topology optimization, we reduce the mesh size discretizing only the design domain and keeping the geometry of boundaries in the final design. We validate the GMG method operating on non-conforming meshes using an adaptive density-based topology optimization method, which coarsens the finite elements dynamically following a weak material estimation criterion. The GMG method requires the generation of the hierarchical non-conforming meshes dynamically from the one used by the adaptive topology optimization to analyze to the one coarsening all the mesh elements until the coarsest level of the mesh hierarchy. We evaluate the performance of the adaptive topology optimization using the GMG preconditioner operating on non-conforming meshes using topology optimization on a fine-conforming mesh as the reference. We also test the strong and weak scaling of the parallel GMG preconditioner with two three-dimensional topology optimization problems using adaptivity, showing the computational advantages of the proposed method.

Laser Scheme for Doppler Cooling of the Hydroxyl Cation (OH+).

We report on a cycling scheme for Doppler cooling of trapped OH+ ions using transitions between the electronic ground state X3Σ- and the first excited triplet state A3Π. We have identified relevant transitions for photon cycling and repumping, have found that coupling into other electronic states is strongly suppressed, and have calculated the number of photon scatterings required to cool OH+ to a temperature where Raman sideband cooling can take over. In contrast to the standard approach, where molecular ions are sympathetically cooled, our scheme does not require co-trapping of another species and opens the door to the creation of pure samples of cold molecular ions with potential applications in quantum information, quantum chemistry, and astrochemistry. The laser cooling scheme identified for OH+ is efficient despite the absence of near-diagonal Franck-Condon factors, suggesting that broader classes of molecules and molecular ions are amenable to laser cooling than commonly assumed.

Modelling and assessment of hydrogen combined cycle power plant using aluminum-water reaction as renewable fuel

Owing to contamination of air and environmental hazards, the demand for sustainable fuels in power plants and other heat engines has climbed undeniably. Aluminum metal is classified among high energy density and low carbon content, which can be reacted with water and repeatedly released a large amount of heat and hydrogen. Since hydrogen is one of the zero-carbon and clean fuels, aluminum can be exploited as a promising energy-carrying and renewable source of energy. This paper is dedicated to the customization of two novel schemes of the combined cycle of power generation systems. The main components of the proposed integrated installations include a hydrogen turbine, gas turbine, multi pressure steam turbines, condenser, heat recovery steam generator and aluminum-water reactor, in which pressurized water absorbs produced heat of the reactor then superheated steam expands in steam turbines. Direct supplied hydrogen, which is generated from the Al-water reaction, expands in the hydrogen turbine and subsequently burns in the combustion chamber of the gas turbine. Hydrogen properties, consumed heat of reactor, generated powers, effects of streams pressure, energetic and exergetic productivity variation of both schemes were evaluated comparatively to ensure the best system performance along with the high net efficiency. According to the numerical analysis of the thermodynamic characteristics in steady state regime using EES software, the energy and energy efficiencies of scheme A were calculated to be 40.72% and 38.36%, besides in scheme B were 39.6% and 37.3%, respectively.

Cycle-based signal timing with traffic flow prediction for dynamic environment

This article studies adaptive traffic signal control problem of single intersection in dynamic environment. A novel cycle-based signal timing method with traffic flow prediction (CycleRL) is proposed to improve the traffic efficiency under dynamic traffic flow. Firstly, the empirical mode decomposition is applied to denoise the flow data. Then a data-model hybrid driven traffic flow prediction strategy is designed to predict the traffic flow, which combines a model-based Kalman filter and an LSTM network-based predictor and adopts another Kalman filter to fuse both prediction results to improve the prediction precision. Besides, a robust signal cycle timing strategy based on human-machine collaboration is developed to deal with dynamic traffic flow, which firstly designs a rule-based signal cycle scheme according to the predicted flow data as the preliminary scheme, and then finetunes the preliminary scheme based on Soft Actor-Critic (SAC) algorithm according to the real-time traffic dynamics. The experiments in both synthetic scenario and real-world scenario show that the proposed data-model hybrid driven traffic flow prediction algorithm has better prediction performance and the proposed CycleRL method outperforms rule-based methods, flow-based allocation methods and traditional reinforcement learning method. Moreover, it is also shown that the proposed CycleRL method has better transferability to bridge the discrepancy across domains.

Energy Efficient Priority-Based Hybrid MAC Protocol for IoT-Enabled WBAN Systems

Among the wireless body area network (WBAN) scarce resources, energy resource is an essential resource on which most of the WBAN biomedical devices activities depend upon. The biomedical devices are usually battery-powered and if they fail to operate as required because of battery power drain, the WBAN system would become unreliable, and this could lead to life-threatening situations. Consequently, it would be of advantage and logical to minimize energy consumption and energy wastage issues to achieve an energy efficient WBAN system. Following this, we proposed a coordinated superframe duty cycle hybrid MAC (SDC-HYMAC) protocol to enhance energy efficiency and to prolong the biomedical devices lifetime. To improve the energy efficiency of the WBAN system, we introduced different energy resource management strategies including the design of a priority-based slot-allocation scheme to minimize timeslot and energy wastage. Also, we proposed a coordinated superframe duty cycle (SDC) scheme to accurately select an appropriate superframe order (SO) based on the traffic information and the priority level of the biomedical devices to save energy and prolong the devices lifetime. We compared the SDC-HYMAC protocol with other related protocols like MG-HYMAC, HyMAC, and CPMAC for the sake of validation, and is simulated in MATLAB. The outcome of the simulation results revealed that the SDC-HYMAC protocol performed better than the existing protocols using performance metrics like convergence speed, energy efficiency, delay, packet drop ratio, and devices lifetime.

Controlling Action Space of Reinforcement-Learning-Based Energy Management in Batteryless Applications

Duty cycle management is critical for energy-neutral operation of batteryless devices. Many efforts have been made to develop an effective duty cycling method, including machine learning-based approaches, but existing methods can barely handle the dynamic harvesting environments of batteryless devices. Specifically, most machine learning-based methods require the harvesting patterns to be collected in advance, as well as manual configuration of the duty-cycle boundaries. In this paper, we propose a configuration-free duty cycling scheme for batteryless devices, called CTRL, with which energy harvesting nodes tune the duty cycle themselves adapting to the surrounding environment without user intervention. This approach combines reinforcement learning (RL) with a control system to allow the learning algorithm to explore all possible search space automatically. The learning algorithm sets the target state of charge (SoC) of the energy storage, instead of explicitly setting the target task frequency at a given time. The control system then satisfies the target SoC by controlling the duty cycle. An evaluation based on real implementation of the system using publicly available trace data shows that CTRL outperforms state-of-the-art approaches, resulting in 40% less frequent power failures in energy-scarce environments, while achieving more than ten times the task frequency in energy-rich environments.