Hybrid Cycle Research Articles

Year-round operation the solar powered hybrid adsorption-compression refrigeration cycle

In our earlier papers a hybrid adsorption-compression refrigeration cycle was presented. The hybrid, two stages cycle is based only on the natural refrigerants: water and carbon dioxide. The main advantage of the hybrid cycle is that the carbon dioxide compression cycle is subcritical because during the year-round operation it is possible to maintain the condensing temperature below 20 oC. During the hot season, this is achieved by adsorption cooling, during cold seasons the wet cooling tower is sufficient. Already several years of experience, allowed to gather a considerable amount of measurement data. The refrigeration system is working in our laboratory constantly since 2013. In 2015 the adsorption system was upgraded by the manufacturer. In 2017 frequency inverter for wet tower fan controlling was introduced. The refrigeration chamber was used for tests with different content and operation of the refrigeration chamber (loading and unloading). The assumed CO2 evaporating temperature was -35 oC. The averaged for HT(High Temperature) part of the cascade (adsorption cycle only) COPHT=0.51 for the whole year 2018. This may be considered a very good performance. 

Assessing geothermal/solar hybridization – Integrating a solar thermal topping cycle into a geothermal bottoming cycle with energy storage

Geothermal and concentrating solar power (CSP) technologies typically use heat at different temperatures in their commercial deployments. This enables a technically viable hybridization of a solar topping cycle and a geothermal bottoming cycle at locations where both resources are available. In this article, an underperforming geothermal power system based at Burley, Idaho is used as a baseline to investigate the technical and economic potential of such a hybrid cycle. A direct thermal energy storage (TES) system is also integrated to overcome the intermittency of the solar resource. Design and off-design behavior of key components are modelled to simulate the annual performance of the hybrid system on an hourly basis. The sizing of the solar field and thermal storage is investigated and is seen to significantly impact the annual electricity generation and efficiency. Various cost scenarios for the solar field and thermal energy storage are investigated. An economic metric – levelized cost of electricity (LCOE) – is used to optimize the solar field sizing and TES capacity. The hybrid plant converts the additional solar heat input into additional work with an efficiency of 32.9%. Retrofitting a geothermal plant with solar and eight hours of energy storage can achieve an LCOE of 0.136 $/kWhe in current cost scenarios and 0.081 $/kWhe in a future cost reduction scenario. Although the hybrid system cannot directly compete with current PV systems without batteries, it has an LCOE 32% lower than that of a PV-battery system. This paper provides insights into the research and development of the future grid with a high renewable energy penetration and encourages further study of energy hybridization for improved efficiencies and economics.

Surge and Stall Detection Using Acoustic Analysis for Gas Turbine Hybrid Cycles

Abstract Compressor dynamics were studied in a gas turbine—fuel cell hybrid power system having a larger compressor volume than traditionally found in gas turbine systems. This larger compressor volume adversely affects the surge margin of the gas turbine. Industrial acoustic sensors were placed near the compressor to identify when the equipment was getting close to the surge line. Fast Fourier transform (FFT) mathematical analysis was used to obtain spectra representing the probability density across the frequency range (0–5000 Hz). Comparison between FFT spectra for nominal and transient operations revealed that higher amplitude spikes were observed during incipient stall at three different frequencies, 900, 1020, and 1800 Hz. These frequencies were compared to the natural frequencies of the equipment and the frequency for the rotating turbomachinery to identify more general nature of the acoustic signal typical of the onset of compressor surge. The primary goal of this acoustic analysis was to establish an online methodology to monitor compressor stability that can be anticipated and avoided.

A sensitive fluorometric bio-barcodes immunoassay for detection of triazophos residue in agricultural products and water samples by iterative cycles of DNA-RNA hybridization and dissociation of fluorophores by Ribonuclease H

Although the toxicity of triazophos is high and it has been pulled from the market in many countries; it is still widely used and frequently detected in agricultural products. While conventional analyses have been routinely used for the quantification and monitoring of triazophos residues, those for detecting low residual levels are deemed necessary. Therefore, we developed a novel and sensitive fluorometric signal amplification immunoassay employing bio-barcodes for the quantitative analysis of triazophos residues in foodstuffs and surface water. Herein, monoclonal antibodies (mAbs) attached to gold nanoparticles (AuNPs) were coated with DNA oligonucleotides (used as a signal generator), and a complementary fluorogenic RNA was used for signal amplification. The system generated detection signals through DNA-RNA hybridization and subsequent dissociation of fluorophores by Ribonuclease H (RNase H). It has to be noted that RNase H can only disintegrate the RNA in DNA-RNA duplex, but not cleave single or double-stranded DNA. Hence, with iterative cycles of DNA-RNA hybridization, sufficient strong signal was obtained for reliable detection of residues. Furthermore, this method enables quantitative detection of triazophos residues through fluorescence intensity measurements. The competitive immunoassay shows a wide linear range of 0.01–100 ng/mL with a limit of detection (LOD) of 0.0032 ng/mL. The assay substantially meets the demand for the low residue detection of triazophos residues in agricultural products and water samples. Accuracy (expressed as spiked recovery %) and coefficient of variation (CV) were ranged from 73.4% to 116% and 7.04% to 17.4%, respectively. The proposed bio-barcodes immunoassay has the advantages of being stable, reproducible, and reliable for residue detection. In sum, the present study provides a novel approach for detection of small molecules in various sample matrices.

Genome Synteny Has Been Conserved Among the Octoploid Progenitors of Cultivated Strawberry Over Millions of Years of Evolution.

Allo-octoploid cultivated strawberry (Fragaria × ananassa) originated through a combination of polyploid and homoploid hybridization, domestication of an interspecific hybrid lineage, and continued admixture of wild species over the last 300 years. While genes appear to flow freely between the octoploid progenitors, the genome structures and diversity of the octoploid species remain poorly understood. The complexity and absence of an octoploid genome frustrated early efforts to study chromosome evolution, resolve subgenomic structure, and develop a single coherent linkage group nomenclature. Here, we show that octoploid Fragaria species harbor millions of subgenome-specific DNA variants. Their diversity was sufficient to distinguish duplicated (homoeologous and paralogous) DNA sequences and develop 50K and 850K SNP genotyping arrays populated with co-dominant, disomic SNP markers distributed throughout the octoploid genome. Whole-genome shotgun genotyping of an interspecific segregating population yielded 1.9M genetically mapped subgenome variants in 5,521 haploblocks spanning 3,394 cM in F. chiloensis subsp. lucida, and 1.6M genetically mapped subgenome variants in 3,179 haploblocks spanning 2,017 cM in F. × ananassa. These studies provide a dense genomic framework of subgenome-specific DNA markers for seamlessly cross-referencing genetic and physical mapping information and unifying existing chromosome nomenclatures. Using comparative genomics, we show that geographically diverse wild octoploids are effectively diploidized, nearly completely collinear, and retain strong macro-synteny with diploid progenitor species. The preservation of genome structure among allo-octoploid taxa is a critical factor in the unique history of garden strawberry, where unimpeded gene flow supported its origin and domestication through repeated cycles of interspecific hybridization.

Comparing Fuel Consumption and Emission Levels of Hybrid Powertrain Configurations and a Conventional Powertrain in Varied Drive Cycles and Degree of Hybridization

Hybrid electric powertrains in automotive applications aim to improve emissions and fuel economy with respect to conventional internal combustion engine vehicles. Variety of design scenarios need to be addressed in designing a hybrid electric vehicle to achieve desired design objectives such as fuel consumption and exhaust gas emissions. The work in this paper presents an analysis of the design objectives for an automobile powertrain with respect to different design scenarios, i. e. target drive cycle and degree of hybridization. Toward these ends, four powertrain configuration models (i. e. internal combustion engine, series, parallel and complex hybrid powertrain configurations) of a small vehicle (motorized three wheeler) are developed using Model Advisor software and simulated with varied drive cycles and degrees of hybridization. Firstly, the impact of vehicle power control strategy and operational characteristics of the different powertrain configurations are investigated with respect to exhaust gas emissions and fuel consumption. Secondly, the drive cycles are scaled according to kinetic intensity and the relationship between fuel consumption and drive cycles is assessed. Thirdly, three fuel consumption models are developed so that fuel consumption values for a real-world drive cycle may be predicted in regard to each powertrain configuration. The results show that when compared with a conventional powertrain fuel consumption is lower in hybrid vehicles. This work led to the surprisingly result showing higher CO emission levels with hybrid vehicles. Furthermore, fuel consumption of all four powertrains showed a strong correlation with kinetic intensity values of selected drive cycles. It was found that with varied drive cycles the average fuel advantage for each was: series 23 %, parallel 21 %, and complex hybrids 33 %, compared to an IC engine powertrain. The study reveals that performance of hybrid configurations vary significantly with drive cycle and degree of hybridization. The paper also suggests future areas of study.

Gait Control of a Fully Actuated Walking Robot

Abstract This paper considers the problem of feedback control of a fully actuated biped robot such that a virtual holonomic constraint (VHC) is enforced concomitant with control of the stance leg using a reach control methodology. The reach controller achieves safety and liveness specifications on the stance leg speed and the step size, resulting in a polytopic state space for the restricted hybrid dynamics on the VHC constraint manifold. It is shown that both the restricted system and the full hybrid system exhibit a stable, hybrid limit cycle. The design method can provide a way to compliantly adjust gait speed, for instance, to gently transition between different gaits, while maintaining transients within safe bounds.

Detection of microRNA using enzyme-assisted amplifying and DNA-templated silver nanoclusters signal-off fluorescence bioassay

A Simple and fast analysis strategy of fluorescence quenching based on DNA-templated silver nanoclusters was developed for detection of miR-122 related to diseases such as human liver. We used Exo III to cleave the silver cluster template and assist in the DNA-RNA complex cycle. When the target is absent, the silver cluster template remains intact, and DNA-AgNCs are generated under the action of AgNO3/NaBH4, producing a strong background fluorescence signal. Once the target is added, the site of the Exo III occurs after a series of hybridization cycles, the Exo III acts, the template DNA is continuously hydrolyzed, and the fluorescence intensity of the system is significantly reduced. By comparing the changes in the fluorescence signal, we found that this strategy has good sensitivity and the detection limit is as low as 84.0 pM. The strategy also has excellent discriminating ability and good selectivity, it can provide a persuasive reference for the early diagnosis of liver cancer and hepatitis.

Proposal and comprehensive analysis of an innovative CCP plant based on an internal integration of double flash power system and ejector refrigeration cycle

Utilizing high-efficient systems for cooling and electricity generation from green energy resources is an efficient method of sustainable development. For this aim, an innovative hybrid cycle for simultaneous power and cooling generation is recommended. The presented system is an internal integration of double-flash ejector refrigeration and power systems. First-law and second-law analysis are employed to investigate the feasibility of the system. Besides, a single-objective optimization performed by the implementation of the GA technique. The optimal energy and exergy efficacies are achieved by 72.57% and 27.69%, respectively.Furthermore, a thorough parametric analysis indicated that the energy and exergy efficacies could be optimized according to turbine pressure and ejector pressure. Moreover, it is showed that a higher energy efficacy and cooling capacity is obtainable by augmenting the ejector pressure, evaporator temperature, and compressor pressure ratio. Whereas, the exergy efficacy can be enhanced by increasing condenser #2 pressure. Besides, based on the exergy efficacy of each constituent of the system, the flashing chamber 1 shows the most excellent exergy efficacy among all the constitutes while the highest value of exergy is destroyed within the condenser 1.

Technical analysis of a hybrid solid oxide fuel cell/gas turbine cycle

The relatively high operating temperature of the solid oxide fuel cell allows for a highly efficient conversion to power, internal reforming, and high-quality by-product heat for cogeneration or a bottoming cycle. Besides, high-temperature fuel cells offer a good opportunity for coupling to a gas turbine. Fuel cell systems have demonstrated minimal air pollutant emissions and low greenhouse gas emissions. This paper focuses on the investigation and technical analysis of a direct internal reforming solid oxide fuel cell (DIR-SOFC) and a gas turbine (GT) system. The technical analysis comprises of an energy and exergy analysis of the hybrid cycle, using the Gibbs function minimization technique for the methane steam reforming process. The assessment is performed to determine the influence of the hybrid cycle operating temperature and pressure, steam-to-carbon ratio and fuel and oxidant usage in the fuel cell. Equilibrium calculations are made to find the ranges of inlet steam-to-carbon ratio and the operating current density of the fuel cell. After that, a hybrid system consists of a DIR-SOFC and a GT is evaluated using computer simulation. The results showed that the fuel cell is the main power producer system at the design point. The high-energy efficiency (around 62%) and exergy efficiency (around 58%) are achieved by the hybrid cycle compared to fuel cell efficiency (about 40%) and the GT (around 38%). The power ratio (SOFC/GT) found was 1.50. An analysis varying the fuel cell current density and the GT pressure ratio was performed showing that the fuel cell power production decreases about 7% with increasing current density when the GT becomes the main power-producing equipment. However, the system energy efficiency decreases with the reduction of power produced by the fuel cell.

Hybrid cycle reservoir with jumps for multivariate time series prediction: industrial application in oil drilling process

Industrial oil drilling processes usually produce high-dimensional multivariate time series data, in which the significant data changes associated with key variables possibly indicate potential drilling accidents. Therefore, it is of great significance to establish a multivariate time series prediction model for the safety of drilling operations. Recently, echo state networks (ESNs) have been widely used in multitime series predictions. However, traditional ESNs use randomly generated sparse network structures and single neuron models, which makes it difficult to achieve a satisfactory performance for complex multivariate time series predictions. In response to this problem, this study proposes a novel hybrid cycle reservoir with jumps (HCRJ) which combines the hybrid wavelet neuron model with the cycle reservoir with jumps (CRJ) structure. In the face of high-dimensional data sets generated by oil drilling, this paper selects a principal component analysis algorithm combined with certain process knowledge to find key variables before related variables are specified by means of Gray correlation analysis methods. The HCRJ networks are used to realize temporal predictions based on data of related variables. To confirm the validity of the model, the HCRJ networks are applied to an oil drilling process and compared to traditional ESNs and CRJ methods. The results show that the HCRJ networks enrich the dynamic characteristics of networks without increasing the complexity of the reserve pool, which helps improve the prediction accuracy of the oil drilling sequence and reduce the occurrence of drilling accidents.

Thermal and Economic analysis of Solar Organic Rankine Cycle

The use of solar thermal energy for electricity generation is a clean and sustainable way to cover the increasing energy needs of our society. The most mature technology for capturing solar energy in high temperature levels is the Parabolic Trough Collector. In this study, an Organic Rankine Cycle coupled with Parabolic Trough Collector is analysed for two approaches. First is to develop a hybrid cycle in which the Parabolic Trough Collector field is combined with Traditional Steam Rankine Cycle without storage tank having boiler as a heat exchanger for 25MW power generation at GNFC, Bharuch. And the second approach is to develop an Organic Rankine cycle coupled with Concentrated Solar collector field (Parabolic Trough Collector Field) without storage tank and water is used as a working fluid in both the systems. Economic analysis is also reported to assess the performance and commercial viability of the system.

Thermodynamic analyses on hybrid sorption cycles for low-grade heat storage and cogeneration of power and refrigeration

This paper investigates three ways of coupling a solid/gas sorption refrigeration cycle with a Rankine cycle to create innovative hybrid cycles enabling power and refrigeration cogeneration with intrinsic energy storage. A new methodology has been developed to analyze these hybrid cycles and assess five relevant performance criteria (required heat source temperature, energy efficiency, exergy efficiency, power production ratio, and exergy storage density). Screening of 103 reactive salts implemented in the different hybrid cycle configurations highlights the most favorable configuration and reagent to meet the requirements of various applications. Analyses show that energy and exergy efficiencies can reach 0.61 and 0.40, respectively. Exergy storage density ranges from 142 to 640 kJ/kgNH3 when the heat source temperature is increased from 107 °C to 250 °C.

System principles and applications of hybrid sorption–compression heat pump – A review

Heat pumps are widely used in energy conversion and management. To take full advantage of vapor compression and sorption principles, hybrid sorption–compression heat pumps were proposed for practical needs. The hybrids have a number of advantages, such as flexible operating range, large temperature lift and high energy efficiency. A comprehensive review is performed on system principles and applications of hybrid sorption–compression heat pump including absorption–compression (ABC) and solid sorption–compression (SSC), particularly taking cycle features as the main thread. Characteristics of different hybrid cycles are summarized and analyzed. There are mainly four types of ABC cycles, featuring with the compressor placed at different positions in terms of practical need. Among them, the ABC cycle with compressor between absorber and generator is an efficient approach to upgrading industrial waste heat to a high temperature of above 100 °C. For SSC cycles, there are two main types. Ammonia or hydrogen is chosen as refrigerant. Large chemical reaction heat can considerably improve cycle efficiency. The review indicates that most researches of hybrid cycles focused on theoretical and experimental performance analysis, selection of working pairs and development of novel cycles. Few applications are found because appropriate compressors for hybrid cycles are not commercially available. In future, compressors of high efficiency and reasonable price should be specially designed and manufactured. Additionally, new working pairs for industrial waste heat recovery are expected. Moreover, energy efficiency improvement of hybrid cycles in applications is urgently needed. Finally, for SSC, some novel cycles can be developed for high thermal energy storage.

Energetic and Exergetic Investigations of Hybrid Configurations in an Absorption Refrigeration Chiller by Aspen Plus

In the present study, a steady-state simulation model was built and validated by Aspen Plus to assess the performance of an absorption refrigeration chiller according to the open literature. Given the complex heat transfer happening in the absorbers and the generator, several assumptions were proposed to simplify the model, for which a new parameter ε l i q was introduced to describe the ratio of possible heat that could be recovered from the absorption and heat-transferring process in the solution cooling absorber. The energetic and the exergetic investigations of a basic cycle and hybrid cycles were conducted, in which the following parameters were analyzed: coefficient of performance (COP), exergetic efficiency, exergy destruction, and irreversibility. According to the results, the basic cycle exhibited major irreversibility in the absorbers and the generator. Subsequently, two proposed novel configurations were adopted to enhance its performance; the first (configuration 1) involved a compressor between a solution heat exchanger and a solution cooling absorber, and the second (configuration 2) involved a compressor between a rectifier and a condenser. The peak COP and the overall exergetic efficiency (η) of configuration 1 were found to be better, increasing by 15% and 5.5%, respectively, and those of configuration 2 were also upregulated by 5% and 4%, respectively. The rise in intermediate compressor ratio not only reduced the driving generator temperature of both configurations but also expanded the operating range of the system under configuration 1, thus proving their feasibility in waste heat sources and the superiority of configuration 1. Detailed information about the optimal state for hybrid cycles is also presented.

Analysis of Hybrid Ejector Absorption Cooling System

In this paper, a hybrid ejector single-effect lithium-bromide water cycle is theoretically investigated. The system is a conventional single-effect cycle activated by an external steam-ejector loop. A mathematical model of the whole system is developed. Simulations are carried out to study the effect of the major parameters of the hybrid cycle on its performances and in comparison with the conventional cycle. The ejector performance is also investigated. Results show that the entrainment ratio rises with steam pressure and condenser temperature, while it decreases with increasing generator temperature. The effect of the evaporator temperature on ejector performance is negligible. It is shown also that the hybrid cycle exhibits better performances than the corresponding basic cycle. However, the performance improvement is limited to a specific range of the operating parameters. Outside this range, the hybrid system behaves similar to a conventional cycle. Inside this range, the COP increases, reaches a maximum, and then decreases and rejoins the behavior of the basic cycle. The maximum COP, which can be as large as that of a conventional double-effect cycle, about 1, is obtained at lower temperatures than in the case of single-effect cycles.

A Polymer Scaffold Binder Structure for Improving Long-Term Cycle Performance of Lithium Metal Powder Electrode

Lithium metal anode is being revalued as a candidate for large-scale battery systems, such as electric vehicles (EVs) and energy storage systems (ESSs), owing to its high theoretical density and lowest negative potential. However, to commercialize lithium metal in large-scale battery systems, the formation of dendrite and continuous side reactions during repeated cycling must be suppressed. In our previous contribution, we improved this problem by using Li metal powder (LiMP), which was compressed on a Cu foil with a small amount of binder instead of bare lithium metal foil. Due to higher surface area of LiMP, the actual current density felt by LiMP is much lower than that of general lithium foil. Nevertheless, during repeated cycling, the high-surface-area structure of LiMP became flatter and is finally covered with numerous dendrites. Herein, we report a LiMP electrode with a scaffold barrier using polyimide (PI) binder. As PI binder forms its own barrier structure at the interstitial region between LiMP particles, the energy density of the cell can be enhanced without additional hosting materials or processes. Especially, the scaffold structure of PI binder can confine the Li stripping/plating reactions within the matrix. Furthermore, we investigated their electrochemical properties, such as DC-IR based on hybrid pulse power characterization (HPPC), cycle performance, and Li plating/stripping mechanism.

(Invited) HydroGEN Supernode: Linking Low Temperature Electrolysis/Hybrid Materials Properties to Electrode Performance

The HydroGEN Energy Materials Network (EMN) supernode in low temperature electrolysis combines capabilities from the National Renewable Energy Laboratory (NREL), Lawrence Berkeley National Laboratory (LBNL), and Savannah River National Laboratory (SRNL) to perform relevant and ground-breaking research outside of EMN-funded projects. The low temperature electrolysis supernode focuses on: evaluating and bridging the gap between rotating disk electrode half-cell activity and membrane electrode assembly single-cell performance; and understanding how electrode composition and processing parameters affects device performance. Ex-situ testing has been used to screen a variety of catalysts and correlate oxygen evolution activity to in-situ performance. Gaps between half- and single-cells were attributed to differences in configuration and standardized test parameters. While non-kinetic loss in membrane electrode assemblies are primarily due to resistance (ohmic), significantly larger transport losses are found in rotating disk electrodes due to electrode orientation and agitation. Differences in kinetics between these methods is primarily due to temperature. Increasing half-cell temperature and using flow cells can be used to bridge the gap between ex- and in-situ performance. Various oxygen evolution catalyst types, including different surfaces (metal/oxide), supports, surface areas, and components, were evaluated to address test differences across these material sets. Additionally, electrode composition and processing parameters were evaluated for their affect in electrolysis performance. Although catalyst layer uniformity may not significantly affect device performance at high loading, coating methodology is critical at low loading. Various spray coating parameters, including ink composition (ionomer content, water/alcohol ratio), drying temperature, and deposition rate were evaluated and found to alter the resulting performance in membrane electrode assemblies. Ionomer content was further correlated to half-cell tests, where low content may adversely impact ink stability (catalyst layer uniformity) and the catalyst layer interface, while high content may lower performance through contaminant effects. Parameters from spray coating tests were applied to slot die and gravure coating methods to transfer this understanding to larger-scale processes. Efforts to tune coating parameters utilize rheology studies and ex-situ characterization to assess catalyst-ionomer-solvent interactions and ionomer thin films. Multiscale modelling was used to evaluate membrane electrode assembly performance and separate kinetic, transport, and ohmic losses. Composition and processing parameters were additionally applied to hybrid cycles.

New hybrid cycle jump approach for predicting low-cycle fatigue behavior by a micromechanical model with the damage induced anisotropy concept

In this work, a new hybrid cycle jump approach was proposed to predict the low-cycle fatigue (LCF) response using a well-established micromechanical model. The damage activation/deactivation phenomenon was formulated at the macroscale. Using the concept of rate independent plasticity with the small strains assumption, the damage deactivation effect on the LCF response and its lifetime was accurately described by the model under simple and complex cyclic loading paths. Three algorithms namely, Taylor 1st and 2nd order and predictor-corrector were utilized for estimating the model response after each cycle jump. An optimum precision factor (ρ) value was defined and then tested via a suitable compromise between computation times and accuracy. In order to numerically determine the cyclic jump length (ΔN), a new hybrid approach was developed based on the overall von Mises stress and the overall damage together with monitoring the accumulated slip. Then, a comparative study revealed that the predictor-corrector algorithm was opted due to its robustness compared to the other algorithms. The numerical study was carried out using two different cyclic loading configurations. One was under simple tension-compression and the other under complex tension-torsion with 90° out-of-phase angle. The model response was described under two distinct states: (i) cycle-by-cycle and (ii) cycle jump concept. For each numerical state, the overall and local responses were recorded. With the new hybrid cycle jump approach, the model response highlights that the greater, the number of cycles, the greater, the gain in computation time but the less, the accuracy. For example, in TC for Nf = 10,000 cycles, a recorded gain in computation time was attained 77% (against 95% by means of cycles number) with a relative error of 4%; whereas in TT90 of Nf = 2124, the computation gain became 43.4% (and 73.4% with respect to number of jumped cycles) with a relative error of 3%.

Hybrid Cycle with the Combination of Flywheel and Gear System

Hybrid Cycle with the Combination of Flywheel and Gear System