Excess Thermal Energy Research Articles

Kinetic study of lithium orthosilicate pellets for high‐temperature chemical heat pumps

AbstractLithium orthosilicate/carbon dioxide/zeolite (Li4SiO4/CO2/zeolite) chemical heat pump (CHP) systems have been discussed for storage and transformation of surplus thermal energy (at ∼650°C) generated from renewable and nuclear energy systems. Tablet forms of Li4SiO4 (referred to as K‐tablets) have been developed with a new pelletizing method for practical application in packed bed CHP reactors. To understand the carbonation and decarbonation mechanisms of K‐tablets, a double‐shell model was suggested and used for explaining experimental results. Isothermal carbonation, decarbonation, and cyclic experiments were conducted under several reaction temperatures for characterization of the K‐tablet. The developed K‐tablet exhibited superior carbonation and decarbonation performance compared to pure Li4SiO4 powder at low temperatures, even when the powder was formed into a tablet shape. The K‐tablet also demonstrated enough durability and a stable reacted conversion value (Δx = 0.75) during cyclic experiments under all temperature. Higher kinetic performances of the K‐tablet than those of pure powder at 650°C and 600°C were also confirmed. The K‐tablet exhibited a high Woutput‐max of 9.82 kW/kg‐tablet at 650°C on the 10th cycle and that value was higher than that of the pure powder (3.25 kW/kg‐Li4SiO4) under the same reaction temperature. The developed K‐tablet has sufficient potential as a CHP material for heat transformation of thermal energy at 600°C to 650°C to >700°C.

Assessment of an Integrated Gasification Combined Cycle using waste tires for hydrogen and fresh water production

In this paper, an Integrated Gasification Combined Cycle (IGCC), which uses waste tires as a feedstock, for power, hydrogen and freshwater production is modeled using both EES and Aspen Plus software packages and assessed thermodynamically. During the study, it is found that tire gasification is a viable solution for leftover tire waste in the world. Furthermore, the novel integration of a multi effect desalination plant, driven by the excess heat from the combined cycle, further increases the systems plant efficiency. The hydrogen production to feed rate ratio is found to be 0.154, which is competitive to high-quality coals, such as Illinois No.6, making waste tires an excellent feedstock to produce hydrogen. The net power production output from the combined cycle is 14.5 MW which was driven by the excess thermal energy of the syngas. The water distillate production rate from the forward flow multi-effect desalination plant at the set conditions is found to be 0.99 kg/s. The systems overall energy and exergy efficiencies obtained are 58.9% and 57.4%, respectively.

Analysis of the research results of the zeolite drying process

The object of research is the zeolite drying process by radiation method. Loose zeolite of two fractions (0–1 mm and 0–5 mm) are used as prototypes. Drying occurs at a layer thickness of zeolite equal to 3 and 5 mm. According to the source of thermal energy, an electric infrared emitter of ceramic type with a nominal electric power of 1 kW is used. The influence of the zeolite fractions, the thickness of the zeolite layer during drying, and the heat flux density on the kinetics of the drying process is established. The numerical values of the zeolite drying time in different periods of drying are determined. According to the analysis of the research results of zeolite drying by a radiation method, it is established that the kinetic laws of this process are similar to the process of drying capillary-porous bodies. The duration of the drying periods depends on the heat flux density and decreases with increasing heat flux density. An increase in the value of the zeolite fractions intensifies the drying process in the warm-up periods and the first drying period, but does not affect the drying rate in the second period. Also a certain influence of the drying process parameters on the moisture content at the end of the first period. The temperature of the zeolite in the first period of drying is not constant, but increases. This indicates an excess of thermal energy supplied during this period. Analysis of the research results also shows that the drying time of the zeolite fraction 0–5 mm is less than the fraction 0–1 mm. Therefore, it is advisable to dry the zeolite fraction of 0–5 mm and, if necessary, further grind after the drying process. This will reduce energy costs and production time of the zeolite as a whole. The obtained curves of zeolite drying allow to predict the nature of the process and can be used to design drying plants.

The density, dynamic viscosity and kinematic viscosity of protic and aprotic polar solvent (pure and mixed) systems: An experimental and theoretical insight of thermophysical properties

We report herein the thermophysical properties of pure protic and aprotic polar solvents (water, dimethyl sulfoxide and N,N-dimethyl formamide) and their mixed (binary and ternary) systems. The experimental density (ρ) and viscosity (η) were determined for these systems by varying temperature range from 293.15 K to 343.15 K. The excess properties (viz., excess molar volumes (VE), excess thermal expansion coefficient (αE), viscosity deviation (Δη) and excess Gibb's free energy (ΔGE) for viscous flow) were computed for mixed systems from experimental values. The excess properties of the mixed systems show clearly a non-ideal behaviour. Especially, a mixture of water with aprotic polar component show better thermophysical properties than pure systems. The pure (DMF) system shows increasing dynamic viscosity values at higher temperature region. Both the binary as well as ternary mixed systems show maximum activation energy (Ea) in the presence of water depicts their thermal stability of the mixed systems. The thermal expansion coefficient (α) also revealed increase in the thermal behaviour for the protic-aprotic systems. In addition to that, thermodynamic parameters are also evaluated for better understanding of thermal stability.

The effects of encapsulation on damage to molecules by electron radiation

Encapsulation of materials imaged by high resolution transmission electron microscopy presents a promising route to the reduction of sample degradation, both independently and in combination with other traditional solutions to controlling radiation damage. In bulk crystals, the main effect of encapsulation (or coating) is the elimination of diffusion routes of beam-induced radical species, enhancing recombination rates and acting to limit overall damage. Moving from bulk to low dimensional materials has significant effects on the nature of damage under the electron beam. We consider the major changes in mechanisms of damage of low dimensional materials by separating the effects of dimensional reduction from the effects of encapsulation. An effect of confinement is discussed using a model example of coronene molecules encapsulated inside single walled carbon nanotubes as determined from molecular dynamics simulations calculating the threshold energy required for hydrogen atom dissociation. The same model system is used to estimate the rate at which the nanotube can dissipate excess thermal energy above room temperature by acting as a thermal sink.

Enhanced laser crystallization of thin film amorphous molybdenum disulfide (MoS2) by means of pulsed laser ultrasound.

Experimental evidence is presented that pulsed laser generated ultrasound can reduce the power necessary to phase convert a nm-scale amorphous film into the crystalline phase. The amount of energy carried by pulsed ultrasound is scant when compared to the CW laser power used to crystallize but the effect is substantial. The evidence points to the extra-ordinary effects possible when a small energy perturbation is applied at a critical juncture in dynamical systems. The candidate system is MoS2 (10 nm) sputtered on yttrium-stabilized zirconia single crystal substrate. A focused CW laser elevates the film - initially in a metastable disordered phase - to the order-disorder conversion (crystallization) temperature. Approximately 25 spot sizes removed from the heating source is a second, high repetition rate laser that induces ultrasonic excitation within the film/substrate via thermoelastic action. The processing is done on a moving stage with direct write patterning control. High resolution ex situ Raman spectroscopy, optical profilometry, and TEM are used to characterize the converted material. For this experimental configuration, we measure a 10% reduction in the heating power required to initiate crystalline formation. The measured phenomenon cannot be attributed to excess thermal energy supplied by the ultrasonic laser.

Novel routes for urban bio-waste management: A combined acidic fermentation and anaerobic digestion process for platform chemicals and biogas production

A combined acidic fermentation and anaerobic digestion (AD) treatment has been developed on pilot scale for urban bio-waste conversion into volatile fatty acid (VFA) and biogas. The specific waste mixture was composed by the pre-treated organic fraction of municipal solid waste (OFMSW) and waste activated sludge (WAS), both produced inside the Treviso (northeast Italy) municipality. The effect of temperature (37 °C and 55 °C) was investigated in both steps. Only the mesophilic fermentation process provided a VFA-rich stream (19.5 g CODVFA/L) with stable physical-chemical features, with no need of chemicals addition for pH control. The sludge buffering capacity made this step technically feasible. The AD step was performed on the solid-rich fraction of fermented bio-waste, after dilution with excess WAS. No relevant differences were observed under the two investigated temperature: in the steady state (organic loading rate of 2.5 kg VS/m3 d), the specific biogas production was 0.40 and 0.45 m3/kg VS at 37 °C and 55 °C respectively, with similar CH4 content (63–64% v/v). The scaled-up version of the system (in an average urban municipality of 170,000 Person Equivalent) revealed that the whole process is thermally sustainable if both reactors are operated at mesophilic temperature: 36% of surplus thermal energy and 13,03 MWh/d of produced electricity, which corresponds to a revenue of 609,605 €/year. In addition, 2,262 kg CODVFA/d are available for parallel purposes, such as the synthesis of bio-products with higher added value than bio-methane (e.g. biopolymers).

Parametric Study and Sensitivity Analysis of Latent Heat Thermal Energy Storage System in Concentrated Solar Power Plants

Compared to solar photovoltaics, concentrated solar power (CSP) can store excessive solar thermal energy, extend the power generation, and levelize the mismatch between the demand and supply. Thermal energy storage (TES) system filled with phase change material (PCM) is a key to make CSP competitive, and it is also a promising indirect energy storage technique. It is of great interests to the solar thermal engineering community to apply the latent heat thermal energy storage (LHTES) system for large-scale CSP application, because PCMs can store more energy due to the latent heat during the melting/freezing process. Therefore, a comprehensive parametric analysis of LHTES system is necessary in order to identify the most sensitive ranges of various parameters to design the LHTES system with better systematic performances. In this study, unlike the existing parametric study based on dimensional parameters, we aimed to provide a more general analysis using dimensionless parameters; therefore, an 11-dimensionless-parameter space of LHTES system was developed, by considering the technical constraints (material properties and operation parameters), without economic constraints. The parametric study and sensitivity analysis were then performed based on a 1D enthalpy-based transient model, and the energy storage efficiency was used as the objective function to minimize the number of variables in the parameter space. It was found that Stanton number (St), dimensionless PCM radius (r/D), and void fraction (ε) are the three most important dimensionless parameters. It is expected that the discovery of this study can bring more discussions in the solar thermal engineering community about the implementation of LHTES system in CSP plant, to further explore the significances of these three dimensionless parameters to the operation of the LHTES system.

A novel model for pyro-electro-catalytic hydrogen production in pure water.

The pyro-electro-catalytic induced generation of hydrogen gas is an environmentally friendly and sustainable way to convert excess thermal energy into a storable form. The main idea is to make use of spontaneous polarization of pyroelectric materials that can be altered by temperature changes. Thus, surface potential changes and subsequent electron exchange with surrounding molecules can be induced. In this work, a fundamental model to describe the behavior of a thermally excited pyroelectric material in pure water is developed. The model combines the fields of pyroelectricity, electrochemistry, diffusion and semiconductor theory. After derivation, it was used to explore some basic questions on pyro-electro-catalytic hydrogen production and the accuracy was tested with experimental data. The results show that p/εr has to be balanced depending on the temperature gradient to maximize the hydrogen production. The validation of the experimental data revealed good agreement.

Complementary Configuration and Optimal Energy Flow of CCHP‐ORC Systems Using a Matrix Modeling Approach

A mass of thermal energy from the combined cooling, heating, and power (CCHP) system will be wasted by the buildings with low ratio of heat to power demand. To further improve the using efficiency of the excess thermal energy, an active method, which adds the organic Rankine cycle (ORC) equipment in the CCHP system, is configured. A complementary configuration of this CCHP‐ORC is also investigated. This paper presents a matrix modeling approach to establish a mathematical model of the CCHP‐ORC system. The CCHP‐ORC system can be viewed as a multiple input and multiple output (MIMO) model. Energy conversion of the system components is described as the efficiency matrices. Energy flow between the system components is described as dispatch matrices. Energy conversion and flow from the system input to output are modeled by a conversion matrix. The objective function and the constraints of the system are determined. The optimal operation strategies are obtained by solving the optimization problem of minimizing the evaluation criteria function. Comprehensive case studies are conducted based on a hypothetical CCHP‐ORC system. The study results reveal that the effectiveness and economic efficiency of the proposed approaches outperform those obtained from conventional CCHP systems.

Pumping Metal

Almost every form of energy conversion creates heat, making it one of the most prevalent forms of energy. When used for mechanical work, thermal energy is most efficient when it can be moved, stored, and converted at its highest possible temperature. But most of today’s pumps and compressors are made from superalloys and ceramics and can’t handle that extreme heat. A team from Georgia Tech has developed a ceramic pump they and others expect to spur a new generation of highly efficient, low-cost systems for storing, transporting, and converting surplus thermal energy produced by renewables like solar and wind.

Photonic structures improve radiative heat exchange of Rosalia alpina (Coleoptera: Cerambycidae)

The insect cuticle serves a multitude of purposes, including: mechanical and thermal protection, water-repelling, acoustic signal absorption and coloration. The influence of cuticular structures on infrared radiation exchange and thermal balance is still largely unexplored. Here we report on the micro- and nanostructured setae covering the elytra of the longicorn beetle Rosalia alpina (Linnaeus, 1758) (Coleoptera: Cerambycidae) that help the insect to survive in hot, summer environments. In the visible part of the spectrum, scale-like setae, covering the black patches of the elytra, efficiently absorb light due to the radiation trap effect. In the infrared part of the spectrum, setae of the whole elytra significantly contribute to the radiative heat exchange. From the biological point of view, insect elytra facilitate camouflage, enable rapid heating to the optimum body temperature and prevent overheating by emitting excess thermal energy.

Combined effects of thermal pretreatment and increasing organic loading by co-substrate addition for enhancing municipal sewage sludge anaerobic digestion and energy production

Abstract In this work, the thermal pretreatment of municipal sewage sludge (MSS) associated to its anaerobic co-digestion with the olive processing wastewater (OPW) was investigated for increasing complex organic matter disintegration and bio-conversion into energy. The hydrolysis of MSS (47%–49%) was performed at 120 °C during 30 min of pretreatment, which was confirmed by Fourier transform infrared (FTIR) spectroscopy. Results showed that increasing total solid (TS) from 0.58% to 3.2% has no effect on the suspended volatile solid (VS) disintegration. Anaerobic co-digestion of pretreated MSS (PMSS) mixed with OPW was investigated and the effect of increasing OPW proportion on the bio-methane potentials (BMP) was examined. The anaerobic digestion of better ratios of PMSS/OPW(80%/20% and 70%/30%) was also performed in sequencing batch reactors (ASBRs). The high biodegradation yields of VS and phenols (81% and 92%, respectively) were obtained at PMSS/OPW of 70%/30% corresponding to a methane yield of 0.441 L/gVSinlet. Therefore, thermal pre-treatment of MSS and OPW addition improved significantly methane yield (50%–160%) and wastes stability. Furthermore, they increased total energy production from 30.9 kW h/ton to 93.5 kW h/ton, which would provide 0.56 M€/year net benefits only from the electric power, which is considered interesting. The excess thermal energy should be used for wastes pretreatment and digester heating.

Possible Mechanism of Sex Determination in Mammals

It is known that undifferentiated embryonic gonads (UEG) in embryos of mammals have a dual nature. They consist of an outer layer of cortex, from which in the process of differentiation develop female sex cells, and from the inner layer – medulla – develop male gametes. During the determination of sex, one of the layers of the gonad develops and the other is suppressed. Therefore, the sex of the future fetus depends on which of the tissue cells - medulla or cortex - survives in the UEG. However, almost nothing is known about the causes for the survival of the medulla or cortex.We believe that, perhaps, the main cause for the development of one of the layers of the gonad and the suppression of the other is cell thermoregulation. The survival of the tissue cells of medulla depends on whether they can avoid heat death, which is determined by their ability to effectively remove excess metabolic heat from the cell nucleus. Since excess thermal energy is released into the cytoplasm through a dense layer of condensed chromatin around the nucleus, consisting predominantly of chromosomal constitutive heterochromatin regions (cHR), the fate of the medulla directly depends on the cHR in its cells.Seemingly, the sex in mammals and human is determined by the cHR on Y chromosomes. It is important not so much the amount of cHR on Y chromosome as its localization in the interphase cell around the nucleoli. Thanks to this localization, excess heat is more effectively removed from the "hottest" point of the nucleus, where ribosomes are formed, which is also necessary for the production of proteins that inhibit the development of cortex cells. Otherwise medulla doomed to degeneration and a cortex tissue will remain in the UEG.

Conversion of CO2-Rich Natural Gas to Liquid Transportation Fuels via Trireforming and Fischer–Tropsch Synthesis: Model-Based Assessment

This paper presents a model-based analysis of a process coupling trireforming and Fischer–Tropsch technologies for the production of liquid fuels from CO2-rich natural gas. The process also includes an upgrading section based on hydrocracking, a separation section, a water gas shift unit, and a Rankine cycle unit for recovering the excess thermal energy produced by the Fischer–Tropsch reactor. Simulations are carried out in the process simulator Aspen Plus using standard unit operation models where applicable, while modeling the nonconventional units, such as the Fischer–Tropsch and hydrocracking reactors, using Aspen Custom Modeler. The proposed process could achieve a carbon conversion efficiency upward of 50% in the analyzed scenario, despite a natural gas feedstock with 30 mol % CO2. The analysis also reveals that the plant-wide electricity consumption could be covered nearly entirely by the Rankine cycle unit, enabling significant cost savings alongside a reduction of the overall global warming poten...

Persistent optical hole-burning spectroscopy of nano-confined dye molecules in liquid at room temperature: Spectral narrowing due to a glassy state and extraordinary relaxation in a nano-cage.

Persistent optical hole-burning spectroscopy has been conducted for a dye molecule within a very small (∼1 nm) reverse micelle at room temperature. The spectra show a spectral narrowing due to site-selective excitation. This definitely demonstrates that the surroundings of the dye molecule are in a glassy state regardless of a solution at room temperature. On the other hand, the hole-burning spectra exhibit large shifts from excitation frequencies, and their positions are almost independent of excitation frequencies. The hole-burning spectra have been theoretically calculated by taking account of a vibronic absorption band of the dye molecule under the assumption that the surroundings of the dye molecule are in a glassy state. The calculated results agree with the experimental ones that were obtained for the dye molecule in a polymer glass for comparison, where it has been found that the ratio of hole-burning efficiencies of vibronic- to electronic-band excitations is quite high. On the other hand, the theoretical results do not explain the large spectral shift from the excitation frequency and small spectral narrowing observed in the hole-burning spectra measured for the dye-containing reverse micelle. It is thought that the spectral shift and broadening occur within the measurement time owing to the relaxation process of the surroundings that are hot with the thermal energy deposited by the dye molecule optically excited. Furthermore, the relaxation should be temporary because the cooling of the inside of the reverse micelle takes place with the dissipation of the excess thermal energy to the outer oil solvent, and so the surroundings of the dye molecule return to the glassy state and do not attain the thermal equilibrium. These results suggest that a very small reverse micelle provides a unique reaction field in which the diffusional motion can be controlled by light in a glassy state.

Temperature measurement and performance assessment of the experimental composting bioreactor

Considerable amount of heat produced during composting of organic matter is usually lost to the surrounding environment. In order to utilize this potential heat source, biomass is composted in mounds or vessels and excess thermal energy is captured via heat exchangers and transported to the site for space heating, preparation of utility water and other applications. The aim of this experimental research is to measure the temperature profiles in a pilot-scale composting bioreactor and assess its performance.

Dynamic Simulation and Modeling of a Novel Combined Hybrid Photovoltaic-Thermal Panel Hybrid System

A novel combined concept and simulation model of a hybrid photovoltaic-thermal solar panel hybrid system are presented. This concept is developed to enhance the energy conversion efficiency of the PV cell and utilize excess thermal energy dissipated by the conversion process to produce domestic hot water. A heat transfer and fluid flow two dimensional dynamic model was developed to describe the behavior of a combined photovoltaic cell-thermal panel hybrid system under different solar irradiance, material properties, and boundary conditions. The model is based on dynamic mass and energy equations coupled with the heat transfer coefficients, and thermodynamic constants as well as material properties.

The density, dynamic viscosity and kinematic viscosity of protic polar solvents (pure and mixed systems) studies: A theoretical insight of thermophysical properties

The densities (ρ) and viscosities (η) have been studied for pure and mixed systems of protic polar solvents water, methanol, ethanol and propan-1-ol for entire composition range at temperature from 293K to 343K in 5K intervals at atmospheric pressure. With increase in temperature the density values as well as the dynamic viscosity values were decrease. The obtained values are used to calculate the excess properties such as excess molar free volume (VE), thermal expansion coefficient (α), excess thermal expansion coefficient (αE), viscosity deviation (Δη) and excess Gibb's free energy (ΔG⁎E) for the activation of viscous flow for mixed systems. The calculated excess properties of binary mixtures were correlated with Redlich-Kister type polynomial equation by least square regression method and fitting parameters were found for all binary systems. The temperature dependence of viscosities for mixed systems has been explained using Arrhenius type equation of Newtonian classic solvents and Eyring transition state equation. The thermodynamic parameters were also evaluated for mixed systems which show the thermal stability of system.

Indicadores de desempeño energético: Una ruta hacia la sustentabilidad. "Caso de estudio una industria torrefactora de café"

El resultado de la producción masiva de bienes y servicios; ha llevado a nuestra civilización a enfrentar un importante reto: convertir las economías industrializadas en sistemas industriales sustentables. Los indicadores de desempeño energético logran mejorar la capacidad energético-productiva de cualquier organización, contribuyen a generar valor económico, alcanzar la competitividad y mitigar el impacto ambiental. En el presente trabajo se establecieron indicadores de desempeño de energía térmica en una de las nueve industrias torrefactora de café que cubren el 90% del mercado nacional. La metodología empleada se basó en el modelo de Gestión Integral de la Energía. Se Identificaron como variables que impactan negativamente en el uso y consumo de energía: el mantenimiento, fugas de calor y falta de calibración de la presión y aire en el quemador conforme a la potencia requerida; y se determinó la magnitud del ahorro y/o gasto en exceso de energía térmica y toneladas de CO2.