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Different heating processes were applied to pretreat the pulp and paper mill sludge to enhance the hydrolysis stage. Hot air oven, autoclave, microwave and water bath were used for comparison. Chemical analyses exposed that all the pretreatment methods have shown improvement in solubilisation of organic matter. Among the pretreatments studied, heat transfer through hot air (80 °C for 90 min) mode had the highest impact on sludge solubilisation. There was an increase in cellulose (P = 0.0096), acid soluble (P = 0.0053) and insoluble lignin (P = 0.0012), but decrease in hemicellulose (P = 0.0009) content after pretreatment. The XRD and FT-IR spectroscopic characterisation shows the development of aliphatic, unsaturated and carbonyl carbon functionalities in the pretreated samples at higher severities. FESEM picture also confirms the change in structure after pretreatment. Thus, pretreatments contribute to disruption of the lignocellulosic structure making the cellulose easily accessible to acidogenic microorganisms. [ABSTRACT FROM AUTHOR]

Abstract Inkjet printed electronic devices, as a new kind of thin film electronics, have got much attention due to their advantages of fast manufacturing, flexibility and cost saving. The challenge of this field is efficient sintering at low temperature, which is necessary for the wearable and flexible electronic application, especially on heat-sensitive substrates, e.g. papers and plastics. To solve the cracking phenomenon at high-temperature sintering which is a common problem for photo paper substrate, we proposed an effective multiple-step method combining acetone washing with LED-assisted low-temperature heating. The sintering temperature was reduced dramatically through using this method, with the resistivity of silver tracks treated at 70 °C equal to that treated by thermal sintering at 150 °C. Thus, we broke through the bottleneck resulting from high-temperature sintering of cracking of long conductive tracks. The mechanisms of the capping agents' removal and LED-assisted low-temperature sintering were investigated by X-ray photoelectron spectra (XPS). Besides, the size of silver nanoparticles (NPs) was well controlled by adjusting the dropping speed of the solution, which helped improve the electrical performance of the ink. The surface properties including morphologic roughness, bonding strength and flexibility were also investigated. By combining inkjet-printing and post-processing method, we showed exemplary applications of paper electronics with fast-manufactured, no-mask-required, pattern-programmable and precisely-controlled characteristics. Our results provide a simple and convenient approach for developing high-performance flexible thin-film electronic devices based on inkjet printing technology. Highlights • Substrate-harmless low-temperature sintering for paper electronics • High-yield silver nanoparticles with controlled size • Applications of flexible electronic circuits, 3D RFID antenna and strain sensor • Good mechanical performance of printed tracks withstanding 1000 bending cycles [ABSTRACT FROM AUTHOR]

A solution-processed conductive paper heater (CPH) with metallic features is used as a new class of low voltage ignitor of nanoenergetic materials (nEMs). In contrast to conventional electrothermal ignition techniques that typically require high operating voltages, the combustion of a paper substrate with a relatively low ignition point generates high thermal energy instantaneously, which makes it possible to ignite nEMs even at low voltages as low as ∼1 V. In addition, the ignition and explosion properties of CPH-based low voltage ignitors are highly controllable and reproducible, mainly due to their simple fabrication and reliable electrical properties. Based on the low voltage ignition property, a compact remote ignition system is demonstrated by integrating wireless a switching circuit, portable batteries, and heater mounter in a small plastic package and operated remotely to ignite the nEMs. [ABSTRACT FROM AUTHOR]

Pyrolysis process of coffee paper cup samples was investigated in a flow stream of nitrogen at different heating rates (10, 20, 30 and 40°Cmin−1), using thermo-analytical techniques. It was found that second pyrolysis stage can be described by Šesták-Berggren (SB) autocatalytic model, with mechanism function f(α)=α0.011(1−α)1.459. Based on analysis of SB kinetic exponents (designated by M and N), it was found that second pyrolysis stage is mainly controlled by chemical process, involving reactions with reaction-order (n) higher than unity. Applying specific statistical analysis, in order to obtain precise distribution of reactivity, the discrete (binomial) distribution has shown that there are two important areas of current distribution for corresponding energy outcomes, within the apparent activation energy as random variable. The first "concentration" area of energy outcomes corresponds to start of chain end depolymerization reaction forming levoglucosan at high enough temperature region, while second "concentration" area of energy outcomes includes occurrence of macro-radicals in liquid phase propagate with radical addition on unsaturated C-C bonds, with cross-linking and formation of small chemical species. It was found that further elevating of temperature (above 340°C), will leads to fact that rate of tar-forming reactions increases and formation of char decreases. [ABSTRACT FROM AUTHOR]

Ultrafast high-temperature heating methods based on the Joule heating of carbon heaters can dramatically shorten the time required for material synthesis/sintering. However, commonly used porous carbon heaters cannot provide stable high temperatures in air, limiting their applicability to the processing of atmosphere-sensitive materials. In this study, we present a novel configuration for ultrafast high-temperature heating in air using commercial graphite paper. This configuration enables stable high temperatures of ~1330–2230 °C in air, on the time-scale of minutes, and ultrafast heating rates, reaching ~104 oC/min. We describe the mechanism behind the excellent performance of our proposed configuration, and further demonstrate its flexibility and controllability by considering ultrafast high-temperature sintering of ZnO ceramics with tunable microstructures using different heating profiles. Our configuration provides a complementary approach to simplifying the ultrafast high-temperature heating process, reducing costs, and meeting the requirements of synthesis/sintering in air. [ABSTRACT FROM AUTHOR]

In this paper, we generalize a fast Fourier transforms (FFTs) based preconditioner and propose a novel α -absolute value preconditioner for all-at-once systems from heat equations. Our preconditioner is symmetric positive definite and can also be computed efficiently using fast Fourier transforms or discrete sine transforms (DSTs). Furthermore, we prove that the corresponding preconditioned matrix has a unitary-plus-low-rank decomposition, and the eigenvalues of the preconditioned matrix are clustered at ±1, which leads to fast convergence rate of the preconditioned MINRES method. Finally, numerical examples on all-at-once systems from heat equations with different discretization scheme demonstrate the effectiveness of our new preconditioner. [ABSTRACT FROM AUTHOR]

Abstract: Morphology-controlled iron-based oxides, including Fe2O3, LaFeO3, NiFe2O4, ZnFe2O4, and CoFe2O4, were obtained using filter paper as a template. A thimble filter paper was soaked in ethylene glycol solution of metal nitrates, and the thimble filter paper–metal nitrate composite was calcined to form the desired iron-based oxides with morphology of thimble filter paper. Choice of ethylene glycol as a solvent and slow heating for removal of the paper template are crucial for maintaining the morphology of paper. [Copyright &y& Elsevier]

Waste heat is one of the major problems associated with the energy system. This paper discusses an energy, exergy, and emissions approach for the hybrid system by utilizing waste heat to the maximum extent. A thermoelectric generator (TEG) is incorporated to utilize the low-temperature waste heat from a hybrid model of a solid oxide fuel cell (SOFC) and a combined heat and power (CHP) system. SOFC is an electrochemical cell that generates power at high temperatures through an electrochemical reaction. The high-temperature, unutilized fuel leaves the SOFC, which is burned in the afterburner. The afterburner temperature controls the operating temperature of SOFC. Here, three recuperators are used to utilize this high-temperature waste heat to improve the performance of SOFC and simultaneously generate heat power from the water or gas recuperator. TEG is an auxiliary power production technology that converts waste heat into energy. A novel integration of TEG with SOFC–CHP hybrid system to utilize the low temperature waste heat, is employed. The main goal of this study is to analyze a novel SOFC–CHP-TEG hybrid system in terms of its thermodynamics and emissions. A Two stage TEG is integrated with the SOFC–CHP hybrid system. The simulation model of high temperature fuel cell (SOFC) is developed on MATLAB and validated with published results. This study analyses the impact of pressure ratio and afterburner temperature on the performance of SOFC–CHP-TEG. To do this, perform energy and exergy assessments using the principles of the first and second laws of thermodynamics. A novel exergy-based sustainability index with emissions analysis for the proposed SOFC–CHP is presented. The achieved overall energy efficiency is 62.54% at a pressure ratio of 12 and an afterburner temperature of 1000 K. With an increase in pressure ratio and temperature, the level of CO emissions reduces significantly. [Display omitted] • A novel energy exergy for SOFC–CHP-TEG system is presented. • Exergy based performance is compared and achieve 56.62. • Utilization of waste heat via TEG. • Energy efficiency of SOFC–CHP-TEG is 62.54% at rp = 12 and afterburner temperature of 900 K. [ABSTRACT FROM AUTHOR]

Self-heating of sensing elements on gas sensors is an effective solution to avoid using external heaters. In this paper, a self-heated hydrogen gas sensor is presented. The sensor was created using the DC sputtering method, which involved fabricating it on a thermal-insulating Kapton flexible substrate. This process utilized a thin film of SnO 2 with thick 50 nm that was modified with nanoclusters of Pt, serving as the sensing material. The SnO 2 /Pt material film was analyzed for microstructure and composition by SEM, XRD, and XPS analysis. Infrared images show that the self-heating effect is mainly concentrated in the strip of gas-sensitive material. It showed many good performances, such as high sensitivity (able to detect down to 50 ppm of H 2), good selectivity (poor response to CO, NH 3 , H 2 S, and NO 2), the sensor's performance is little changed by environmental humidity, and low power consumption (89 μW at 5V). The sensor is also stable and low-cost, suitable for portable H 2 detection devices due to its low generated heat and small size. • The SnO 2 /Pt thin film sensor was fabricated on flexible substrate (Kapton). • The sensor showed good performance to H 2 gas (able to detect down to 50 ppm H 2). • The sensor showed good selectivity (poor response to CO, NH 3 , H 2 S, and NO 2). • The self-heated sensors consume ultralow power (89 μW at 5 V). • The fabricated sensor slightly reduced its sensitivity at ambient humidity of above 90% R.H.. [ABSTRACT FROM AUTHOR]

Abstract: Sintering of printed metal nanoparticles can be made not only by conventional heating, but also by, e.g., electrical, microwave, plasma, laser and flash lamp annealing. We demonstrate sintering by using low-cost incandescent lamps as an effective way of obtaining highly conductive contacts of two types of ink-jet printed metal-nanoparticle inks on paper; both alkanethiol protected gold nanoparticles and a commercially available silver nanoparticle ink. This low-cost roll-to-roll compatible sintering process is especially suitable on paper substrates because of the high diffuse reflectance, relatively high thermal stability and low thermal conductivity of paper. A volume resistivity of around 10μΩcm was achieved of the inkjetted silver nanoparticles within 15s of exposure to an IR lamp, which corresponds to a conductivity of 10–20% of that of bulk silver. Too long exposure time and too high intensity, however, lead to darkening of the paper fibers. Both the crack formation and the coffee ring effect of the inkjet printed gold nanoparticles were, furthermore, found to be reduced on paper as compared to glass or plastic substrates. [Copyright &y& Elsevier]

Recent advances in renewable energy research have suggested the fuel cell as a promising future energy source. Compared to the conventional power generation process, which has multiple-step conversion, a fuel cell is a single-step conversion process and produces power and sometimes heat. The efficiency of the individual existing conventional system is increased by integrating with fuel cells. The purpose of hybridization is to fulfill the demand and supply of power and heat. This paper starts with the historical development of fuel cell proceed with different categorize of hybrid systems. Discuss the possibilities of integration of existing fuel cell with other existing technologies such as SOFC-PEMFC, FC-CHP, FC-GT-ST, FC-Hybrid Vehicle, FC-PV/Battery. Numerical modeling can be done for each hybrid system considering mass balance, energy-exergy balance. At the end of the paper a discussion on the technical, economical, and commercial challenges and their solutions with future possibilities is presented. [Display omitted] • Study the integration potential of fuel cell with other power generating systems. • Fuel-cell hybrid configurations are analyzed. • Modelling aspect of various fuel cell hybrid configurations were summarized. • Fuel cell behavior with power and heat generation is presented. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present our preliminary studies into naphthoquinones as novel reagents for the detection of latent fingermarks on paper. Latent fingermarks deposited on paper substrates were treated with solutions of selected naphthoquinones in ethyl acetate/HFE-7100, with subsequent heating. The selected compounds were 1,4-dihydroxy-2-naphthoic acid, 1,2-naphthoquinone-4-sulfonate, 2-methoxy-1,4-naphthoquinone and 2-methyl-1,4-naphthoquinone. All of the tested compounds yielded purple-brown visible fingermarks, which also exhibited photoluminescence when illuminated with a high intensity filtered light source at 555nm and viewed through red goggles. Indirect heat using an oven at 150°C for 1h was found to be superior to direct heat with an iron, which while providing faster development lead to increased levels of background colouration. Luminescence spectrophotometry revealed differences in photoluminescence characteristics for fingermarks developed with the different naphthoquinones, with excitation over the range 530–590nm. Luminescence spectrophotometry of developed lysine, glycine and serine spots on paper was used to confirm that the naphthoquinones were reacting with amino acids in the latent fingermark. [ABSTRACT FROM AUTHOR]

Abstract: Carbon paper is commonly used as the gas diffusion layer (GDL) in polymer electrolyte membrane (PEM) fuel cells as it exhibits high chemical and mechanical durability. This diffusion medium is also anisotropic, which directly affects its transport properties and specifically the thermal conductivity. In this study, the in-plane thermal conductivity of the carbon paper GDL was determined using thermal diffusivity measurements for a temperature range from −20 to +120°C and four Teflon loadings (0, 5, 20 and 50wt.%). It is important to understand the effect of temperature on the thermal conductivity since PEM fuel cells are designed to operate under various temperatures depending on the application of use. Further, Teflon is used to change the hydrophobic properties of the carbon paper GDL with 20wt.% as the most widely used percentage. In this study, the Teflon loadings were chosen to gain a comprehensive understanding of the thermal resistance due to Teflon. In this study, a quasi-steady method was used to measure the thermal properties of the carbon paper; hence, the phase transformation in the presence of PTFE was investigated. The thermal conductivity decreases with an increase in temperature for all samples. The addition of as little as 5wt.% Teflon resulted in high thermal resistance decreasing the overall thermal conductivity of the sample. Further addition of Teflon did not have major effects on the thermal conductivity. For all treated samples, the thermal conductivity lies in the range of 10.1–14.7W/mK. Finally, empirical relations for the thermal diffusivity and conductivity with temperature were deduced. [Copyright &y& Elsevier]

Abstract: We thank R. Konings et al. for their interest and their valuable critical discussion of our article regarding the fission product release from irradiated oxide fuel during thermal treatment and reply to their comments appearing in this issue. Their feedback stimulated us to give more details on the sampling procedure of investigated materials as well as the measurement procedure in order to exclude misunderstandings. The release curves for iodine and cesium are compared to blank profiles and reanalyzed to demonstrate the features of inductive heating approach applied in authors’ recent study on FP release under inert and oxidizing conditions. [Copyright &y& Elsevier]

• Paper-based microfluidic device combined with a graphene heater for silicon nanodots synthesis. • Total carbohydrates determination based on fluorescence intensity of the silicon nanodots. • Heater temperature controlled by portable electronic system with wireless communication. We report a simple, rapid, low-resource and one-step method for formation of fluorescent silicon nanodots (SNDs) in a microfluidic paper-based analytical device (μPAD) incorporated in a reusable, portable and flexible heater for determination of total carbohydrates. The synthesis of SNDs is based on the redox reaction between (3-aminopropyl) triethoxysilane (APTS) reagent and carbohydrates, which act as a reducer. The graphene-based heater was fabricated by laser ablation of Kapton polyimide. Thereby, the developed system heat the μPAD during the synthesis of SNDs at 80 °C for 30 min. The blue emitting SNDs formed have an emission peak wavelength at 475 nm. We used a digital camera and smartphone for the quantitative analysis of total carbohydrates expressed such as index of glucose or fructose with grey scale value as the analytical parameter. Under the optimal conditions, the method has a low detection limit (0.80 μM for glucose and 0.51 μM for fructose, respectively), and a linear response (10–200 μM for glucose and 10–100 μM for fructose). The method has been applied to the determination of glucose in biological fluids (serum and urine samples). In addition, determination of total carbohydrates in commercial juices and teas have been carried out. [ABSTRACT FROM AUTHOR]

The present paper deals with the influence of different hydrogen enrichment on oxy-fuel combustion of natural gas, enabling important insights regarding decarbonization of high-temperature processes. Experiments were conducted using a high-impulse multifuel burner for industrial applications for hydrogen contents between 0 and 100%. The fuel input varied between 100 and 140 kW, while water-cooled lances were used to simulatethermal loads. The analysis included temperature measurement points, atomic and energy balances and the cooling capacity of the thermal load for steady-state operation. The obtained results show that the flue gas temperature decreases by up to 126 K for pure hydrogen, while the cooling capacities of the thermal load increased by up to 16.3% at constant calorific energy input. The flames for different hydrogen enrichments were also compared visually. Overall, all investigated fuel blends were highly interchangeable with the investigated burner and showed high potential for a timely decarbonization of industrial heating. • Oxy-fuel combustion of hydrogen-enriched natural gas with 0–100% H 2. • Experimental analysis of a semi-industrial scale furnace at steady state conditions. • How the flame length, heat distribution and flow rates depend on H 2 content in NG. • Analysis of mass and energy fluxes with positive pressure within the furnace. • Promising solution for timely CO 2 reduction in high-temperature processes. [ABSTRACT FROM AUTHOR]

• A new finned tube heater used for household frost-free refrigerator is proposed. • The duration of the defrosting cycle is shortened by 12%. • The overall energy consumption is reduced by 0.025 kW·h (10.4%). • FC temperature rise decreases by 2.4 °C. For frost-free refrigerators, the tubular metal sheathed type defrosting heater installed at the downstream of the evaporator is usually stainless steel circular tube defrosting heater (CTDH). During the defrosting process, a large part of the heat leaks into the cabinets of the refrigerator, causing the cabinet temperature to rise. This paper proposes a finned tube defrosting heater (FTDH) by using an aluminum alloy finned square tube as the metal sleeve of the defrosting heater. The external surface area of the defrosting heater is greatly increased due to the existence of the fins, thus strengthening the natural convection between the air and the defrosting heater and shortening the defrosting duration. The defrosting performance (defrosting duration, temperature rise, energy consumption) between FTDH and CTDH are compared experimentally. Results show that the whole defrosting cycle duration is shortened by 12%, while the freezer cabinets (FCs) temperature rise is reduced by 2.1 °C and the maximum FC temperature is reduced by 2.4 °C. In addition, the shorter defrosting operation cycle and the lower FC maximum temperature result in a 10.4% reduction in energy consumption of the whole defrosting cycle. In conclusion, FTDH is promising in refrigerators for reducing the FC temperature rise, shortening the duration and decreasing energy consumption during the defrosting cycle. [ABSTRACT FROM AUTHOR]

Uncertain parameters and factors substantially impact the operational performances of combined cooling, heating, and power (CCHP) systems. This paper constructs a chance-constrained programming model for system design and energy dispatch management of a hybrid solar CCHP system under the uncertainties of solar energy and building loads. The uncertain scenarios with probability distributions are generated in the Latin hypercube sampling and clustering methods. The chance-constrained model transforms stochastic optimization into deterministic optimization based on these scenarios. Then, the multi-objective optimization model of CCHP system considering the performances of economic, energy, emission, and flexibility is established, and the modified ε -constraint method is employed to obtain Pareto solutions. A case study validates the proposed model. The capacities and operational strategies of components in the hybrid CCHP system are optimized, and the impacts of the confidence level of probability distributions of uncertain factors on the optimization results are discussed. The results indicate that the photovoltaic capacity in the hybrid CCHP system declines by 87.5% when the confidence level increases from 0.50 to 0.99. But other components' capacities are raised, and the gas turbine capacity as the key component rises by 10.49%. The energetic and environmental performances of the CCHP system rise with the confidence level, and the operation safety is improved. [ABSTRACT FROM AUTHOR]

The surface faceting of metals has been studied for several decades, typically using experimental methods such as low-energy electron diffraction. In the current paper, surface faceting of tungsten pellets was studied during in situ heating inside an environmental scanning electron microscope (ESEM), which allowed for direct, high-fidelity observation of morphological changes in response to high-temperature annealing under a moderate vacuum (0.8 Torr). Additionally, a second set of tungsten samples was annealed in an ultrahigh vacuum chamber (10−8 Torr), albeit without direct observation via ESEM. This study revealed that oxygen plays a crucial role in tungsten surface faceting and in a morphological transition to vertex rounding. Furthermore, this paper discusses relevant techniques for identifying the crystallographic indices of surface facets. It is demonstrated that a combination of electron backscatter diffraction, tilted-sample imaging from multiple angles, and serial sectioning in a focused ion beam system can be effectively deployed to determine the geometry of faceting, which in turn can be verified with the aid of software for generating Wulff shapes. The influence of processing environment on tungsten surface faceting enables the possibility of designing and controlling the morphology and crystallographic facets of tungsten surfaces. • ESEM annealing of W at 0.8 Torr resulted in oxide sublimation and surface faceting. • The surfaces of samples annealed under UHV remained flat and smooth. • Temperature and grain orientation influence W surface facet size and sharpness. • SEM tilted-sample imaging and serial sectioning tomography aided facet indexing. • Wulffmaker software helped determine relative surface energies of low-index facets. [ABSTRACT FROM AUTHOR]

• Saturated-wave theory for snubber modeling is modified to fix three conceptual errors. • The equivalent resistance and inductance of the snubber are recalculated. • Calculating the thickness of eddy-current region no longer relies on external circuit. • The current rise of the model is nearly the same as the experiment with about 10 % over-estimated peak shorting current. Core snubber is a common device used for breakdown protection in auxiliary heating systems. It absorbs energy from the high-voltage power supply to protect the load. The existing snubber models are based on saturation-wave theory, but the theory still has several conceptual problems. In this paper, an improved saturated-wave theory is presented. We consider that the eddy current region of the tape needs to be layered and that there is an unsaturated region in the tape which enables the snubber to be equated to an inductor. Then we divided the working process of snubber into 4 stages and rederived the circuit model of the snubber. The comparison with the existing simulation model shows that the new model in this paper is closer to the experimental data, especially in the rising phase of short-circuit current. It can more accurately analyze the conditions within a few microseconds after breakdown, and give a useful reference for the design of breakdown protection and power supply systems. [ABSTRACT FROM AUTHOR]

Decarbonising the heating sector is one of the key elements to realizing the ambitious dual carbon goals of China, which is the largest carbon emitter and energy consumer globally. Currently, district heating (DH) systems have penetrated approximately 88% of the urban heating areas in Northern China. Nevertheless, around 90% of the heating demand in China still relies on fossil fuels. A larger scale integration of renewable energy and waste heat sources into the DH systems is critical for decarbonising the entire heating sector in China. However, a deeper level of comprehension is required to harness its full potential. This paper provides a thorough investigation of the status, potential, and national policy schemes of renewable energy and waste heat recovery in the DH systems of China. Combined with a critical review of recent literature on relevant areas published in both international and Chinese domestic sources, the trends, challenges, and future perspectives are discussed from scientific research and practical implementation aspects. This paper highlights the synergy of the integration of renewable energy and waste heat sources in DH, the energy efficiency improvements as well as the use of thermal storage technologies through the implementation of 4th generation district heating and smart energy systems that could offer a more economically viable pathway forward. • Focus on renewable energy and waste heat (REWH) in the district heating (DH) systems in China. • A systematic review of REWH in Chinese DH systems from status, policy, and literature aspects. • Identification of research gaps based on the review of both international and Chinese journals. • Policy recommendations proposed to promote REWH in Chinese DH systems. • The introduction of international experiences on REWH in DH for analysis in the Chinese context. [ABSTRACT FROM AUTHOR]

Increasing the demand for water and energy resources as well as the clean energy policies and the need for pollution emission reduction has developed the research on the renewable energy resources. This paper reviews the recent advances in multi-generation units for heat, electricity, and desalinated water production. It tries to investigate the new papers in this arena which were not mentioned in the previous reviews. The main parts of this work introduce the co-generation systems for the production of "water and electricity", "heat and water", and "electricity, water, and heat". The results show that among the solar energy receiving devices, Photovoltaic/Thermal panels (PV/Ts) and parabolic trough solar collectors are the most used in co-generation systems. On the other hand, a combination of solar collectors and power cycles makes them a suitable choice for the establishment of a large-scale co-generation plant. Therefore, solar collector-based electricity and water co-generation systems have at least 10 times more output capacity than PV- or PV/T-based systems. On the other hand, most heat and water co-generation systems can achieve an output temperature of 60 °C or more and produce around 10000 kg/year of freshwater based on system size. Examining the co-generation systems of water, electricity and heat also shows that these systems have a high production capacity compared to other co-generation systems. Systems based on heliostat solar tower can produce maximum powers of more than 18 MW and fresh water of 90 kg/s. • Recent advances in solar multi-generation units are reviewed. • PV/Ts and parabolic trough solar collectors are most used collectors in cogeneration systems. • RO and MED have more applications in solar-based co-generation units. • Using waste heat can increase technical and economic performance of system. [ABSTRACT FROM AUTHOR]

Loop heat pipes, as a type of two-phase thermal control device, can not only eliminate the reliance on pump transportation technology in single-phase fluid circuits, but also utilize the structural features of gas-liquid pipeline separation to reasonably achieve the evaporation and condensation process. Considering that the loop heat pipes have good application prospects in the field of heat dissipation system in space environment, the condensation pipeline layout on its heat dissipation plate has been optimized in this paper to achieve lightweight while meeting the operational constraints. Based on previous research results, different static surrogate model training methods were compared and combined with genetic algorithms to complete preliminary optimization. After observing insufficient accuracy from static surrogate model, dynamic surrogate model technology was introduced. The results show that the dynamic surrogate model based on hybrid update strategy proposed in this paper can balance the local prediction accuracy, the global convergence ability, and the optimization calculation efficiency, which was more efficient and accurate in lightweight optimization. • Lightweight optimization was performed for radiation radiator by surrogate models. • A dynamic surrogate model based on hybrid update strategy was proposed. • The proposed method has good prediction accuracy and convergence. [ABSTRACT FROM AUTHOR]

• Thermal saturation occurs at bore field center due to the confined boreholes in the interior region. • Boreholes at the bore field center are less efficient boreholes. • Shorter boreholes in the interior region, and deeper ones in perimeter could reduce the total BHE-length. • Total BHE-length savings of this design are affected by the borehole spacing. Most studies about vertical borehole heat exchangers (BHEs) tended to focus on optimizing total borehole length with all boreholes having the same depth. This is mainly because most of the vertical BHEs design tools do not have the feature of designing mixed borehole depths at the same bore field. Because thermal saturation occurs over time at the center of the field due to thermal interaction between the confined boreholes in the interior region, reducing depth of these less efficient boreholes is a desired goal. This paper studies the effects of mixed borehole depths where shorter boreholes are designed to be in the interior region, and deeper ones in the perimeter. The python package pygfunction has been adapted in this paper to generate the thermal response factor of a bore field with mixed borehole depths and to simulate its performance in difference design scenarios. The results reveal that total BHE-length could be decreased by up to 10 % in some cases of mixed borehole depths compared with the case of same-depth boreholes. However, since the total BHE-length could increase in few cases, careful examination is crucial when applying mixed borehole depths. [ABSTRACT FROM AUTHOR]

The majority of small district heating systems (DHS) in Poland are supplied with coal and do not have a status of efficient ones according to Energy Efficiency Directive. They should transform into efficient ones by taking an appropriate measures by the end of 2035. At the same time, a significant reduction of CO 2 emissions is expected in this sector. One of the possible solution for such systems is to apply unites fueled with fuels alternative to coal such as biomass. Cost benefits analysis of implementation a biomass ORC (Organic Rankine Cycle) cogeneration unit in municipal district heating system of 22 MW thermal capacity is the subject of the paper. The research included building configuration scenarios of a heat source regarding ORC size and operation modes. Different economic inputs such as electricity, fuel and European Union Allowance (EUA) for CO 2 prices as well as financial support mechanisms were considered. Economic indexes (Net Present Value, Internal Rate of Return and payback times) have been derived for both Polish and German conditions. [ABSTRACT FROM AUTHOR]

In this paper, we study the diffusive limit of the steady state radiative heat transfer system for non-homogeneous Dirichlet boundary conditions in a bounded domain with flat boundaries. By taking account of the boundary layers, a composite approximate solution is constructed using asymptotic analysis. The convergence to the composite approximate solution in the diffusive limit is proved using a Banach fixed point theorem. The major difficulty lies in the nonlinear coupling between elliptic and kinetic transport equations. To overcome this difficulty, a spectral assumption is proposed to ensure the linear stability of boundary layers. Moreover, a combined L 2 - L ∞ estimate and the Banach fixed point theorem are used to obtain the convergence proof. This result extends our previous work [6] for the well-prepared boundary data case to the general boundary date. [ABSTRACT FROM AUTHOR]

• Combination of the absorption and vapor compression heat pump. • Maximum performance enhancements for heating is 45.8%. • Maximum performance enhancements for cooling is 18.9%. • Power savings for heating and cooling are 16.0% and 31.4%, respectively. • Lower the heat-driven temperature for absorption to 60 °C. Decarbonizing the energy sector becomes a key topic to solving man-made climate change. For achieving indoor thermal comfort conditions, conventional heating, ventilating, and air-conditioning systems consume so much energy in both residential and public buildings. In this paper, a novel solar-assisted absorption-compression system for both heating and cooling is proposed to utilize solar thermal energy throughout the year for the heating/cooling supply. The experimental prototype was built and operational modes including solar-assisted heating/cooling mode and vapor compression individual heating/cooling mode. The performance enhanced by assisted heat input of the proposed system is evaluated by comparing it with air-source heat pumps operated under the same ambient conditions. Performance indices consisting of COP ele increment, power-saving ratio (PSR) and energy-saving ratio (ESR) are presented. The results indicate that the combination of the absorption heat pump subsystem and the vapor compression subsystem lowers the heat-driven temperature to 60 °C and thus makes higher solar collection efficiency possible. The maximum of the COP ele increment and the PSR under solar-assisted heating mode are achieved at conditions with 80 °C hot water temperature, of 45.8% and 31.4%, respectively, and the corresponding value for solar-assisted cooling mode are 18.9% and 16.0%. The speed of compressor as well as fan frequency of terminal has a greater influence on heating performance that on cooling performance due to the different coupling mechanisms. [ABSTRACT FROM AUTHOR]

In the debate on the decarbonisation of heat, renewable electricity tends to play a much more dominant role than green gases, despite the potential advantages of gas in terms of utilising existing transportation networks and end-use appliances. Informed comparisons are hampered by information asymmetry; the renewable electricity has seen a huge grid level deployment whereas low-carbon hydrogen or bio-methane have been limited to some small, stand-alone trials. This paper explores the regulatory and commercial challenges of implementing the first UK neighbourhood level 100% low-carbon hydrogen demonstration project. We draw on existing literature and action research to identify the key practical barriers currently hindering the ability of strategically important actors to accelerate the substitution of natural gas with low carbon hydrogen in local gas networks. This paper adds much needed contextual depth to existing generic and theoretical understandings of low-carbon hydrogen for heat transition feasibility. The learnings from pilot projects, about the exclusion of hydrogen calorific value from the Local Distribution Zone calorific value calculation, Special Purpose Vehicle companies, holding of liability and future costs to consumers, need to be quickly transferred into resilient operational practice, or gas repurposing projects will continue to be less desirable than electrification using existing regulations, and with more rapid delivery. • This paper explores barriers for the first UK 100% hydrogen distribution project. • Learnings from pilot projects need to be transferred into UK operational practice. • Existing regulations present barriers to gas distribution innovation projects. [ABSTRACT FROM AUTHOR]

The ideal non-collapse heated oil shale reservoir may lead to the maximum preservation of pores and fractures. However, the previous research on the pore evolution during heating in oil shale reservoirs has focused only on the analysis of capillary pores, ignoring the supercapillary pores (including fractures) that can provide the free flow of fluid. Through open thermal system experiments, combined with multi-scale visual statistics and quantitative testing, this paper reveals that the surface porosity of supercapillary pores increased from 0.27% to 15.95% and the porosity of capillary pores and microcapillary pores increased from 0% to 39.55%, in which the contribution rate of organic matter pores increased from 2.36% to 87.46%. From the perspective of the trap, we propose that the displacement pressure, breakdown pressure and overburden pressure of surrounding rock determine the pressure of injected CO 2. Regarding the adsorption and free state, through an improved formula for carbon storage potentials, the maximum theoretical CO 2 storage per unit volume for the Minhe depleted oil shale reservoir was estimated to be approximately 0.261 × 109 t/km3. Thus, a depleted oil shale reservoir is a suitable place for CO 2 storage owing to the large storage potential. [ABSTRACT FROM AUTHOR]

• A Stirling heat pump with a temperature gradient in the heat exchanger is studied. • The heat exchanger with a temperature gradient achieves cascade output of energy. • Negative effect due to the mix of gases at different temperatures is insignificant. • Considering economy and efficiency, single large heat pump is also a good choice. The free-piston Stirling heat pump (FPSHP) is efficient, environmentally friendly and has a wide available temperature range, making it a promising device for building heating. The temperature of the external heat-carrying fluid is different at the inlet and outlet of the heating heat exchanger, so there is a temperature gradient in the heating heat exchanger. The larger the scale of the FPSHP, the more pronounced the temperature gradient. However, the influence of such a temperature gradient on system performance has not been investigated so far. This paper therefore presents a detailed study of the FPSHP with a circumferential temperature gradient in the heating heat exchanger. The calculation results show that a cascade output of energy can be achieved when there is a circumferential temperature gradient in the heating heat exchanger. With the same outlet temperature, the larger the temperature difference between the inlet and outlet of the heating heat exchanger, the higher the COP. However, due to the mixing of internal working gases with different temperatures in the compression space, part of the high temperature heat is directly transferred to the low temperature module and output at a lower level, adversely affecting system efficiency. Fortunately, this adverse effect is found to be insignificant when compared with multiple independent small FPSHPs without circumferential temperature gradients. Considering the higher investment cost of multiple small FPSHPs, a single large FPSHP is also a good choice for large heating capacity demand. [ABSTRACT FROM AUTHOR]

Integrated Energy Systems (IES) serve as an effective solution to address grid fluctuations. However, mainstream IES still adhere to established supply strategies such as thermal and electrical non-conversion (TENC), heat determined by power (HDP), and power determined by heat (PDH). These strategies overlook the additional flexibility generated by the synergy between electricity and heat, preventing the full realization of their advantages in supporting the grid. This paper proposes a Flexible Scheduling (FS) operational strategy for IES that maximizes the utilization of flexibility resources to meet the demands of heating, cooling, and electricity while maintaining grid stability. The superiority of this strategy is analyzed through an IES multi-objective optimization scheduling model and a comprehensive flexibility margin model. The results of a case study indicate that the FS strategy reduces total costs by 19.9% compared to TENC, 16.6% compared to HDP, and 5.2% compared to PDH. It exhibits the strongest support for the grid, increasing the overall flexibility margin of IES by 40.5% compared to TENC, 12.7% compared to HDP, and 8.2% compared to PDH. The FS-based IES operational strategy proposed in this paper contributes significantly to the flexible and economical operation of IES. • Established a multi-objective optimization scheduling model for integrated energy systems that considers both economic and environmental factors. • Established a model for the flexibility margin of system electricity and heat. • Proposed the system's "flexible scheduling" operating strategy and validated it. [ABSTRACT FROM AUTHOR]

• Establish an optimization scheduling strategy for electrothermal joint operation. • Increase wind power consumption with electric boiler & heat storage tank. • Simulation shows 87 % wind power absorption rate with electric boiler & heat storage tank. • Combined use of electric boiler & heat storage lowers system operating costs. The intermittency and volatility of wind power and the characteristics of the operating mode of cogeneration units pose certain challenges to the wind power consumption of the power grid. To optimize the performance of the power and heat combined operation system and maximize the wind power consumption, this paper establishes a mathematical model for each component of the cogeneration system, including the thermal dynamic characteristics of the heat network, buildings, cogeneration units, electric boiler, and heat storage tank. At the same time, a scheduling optimization model is proposed, which considers the power load demand, and wind power output of the regional heating system. The research results provide insights and optimal dispatching strategies for ensuring the reliable operation of the power system and heating system and realizing the efficient utilization of wind power. This paper verifies the effectiveness and feasibility of optimizing the cogeneration system and provides a practical solution to the challenge of cogeneration economics. [ABSTRACT FROM AUTHOR]

Traditional flat PV heat pumps has low irradiation density, large PV area, and the PV evaporators are always fixed, causing large area occupation and lots of irradiation missing, which limit the application and system efficiency. To solve the problems, a novel concentrated PV-air dual-source heat pump system (CPV-DSHP) was proposed in the previous paper, but the annual performance and economic comparison with flat PV-DSHP (FPV-DSHP) are still blank, which are extremely concerning to researchers. Besides, the paper also fills related content about the impact of irradiation composition on the system performance and economics, as well as the irradiation comparison on tracking CPV and fixed FPV surface. From the calculation of the validated model, it's found that the CPV-DSHP system could capture 6098 MJ and 2213 MJ more solar energy, and produce 282.21 kWh and 100.16 kWh more electricity in Garze and Hefei in a year. The annual concentration efficiency is 82.73 % in Garze where direct irradiation accounts for 68.89 %, which is only 73.15 % in Hefei with 39.84 %.The COP PVT is annually lifted by 0.40 in Garze. Although the two systems could both get payback in 5∼6 years, the CPV-DSHP only shows economic advantages in places with good direct irradiation conditions like Garze. • A novel concentrated PV-air dual-source heat pump system (CPV-DSHP) is presented. • The annual performance and economic comparison in different cities are supplemented. • The CPV-DSHP could produce 282.21 kWh more electricity in Garze in a year. • The annual concentration efficiency is 82.73 % in Garze with better direct irradiation. • Payback time is 5∼6 years but CPV-DSHP only shows economic advantage in Garze. [ABSTRACT FROM AUTHOR]

Although fully automated, operation of the District Heating Systems (DHS) is considered reactive and simplistic since control decisions are most often made based on the real-time ambient temperature. The research presented in this paper is aiming at facilitating proactive DHS control, by using predictive modeling techniques based on modern Artificial Intelligence (AI) architectures, namely the Deep Learning (DL)-based multivariate time-series forecasting. Proactive approach involves controlling fluid temperature in the DHS supply line, based on relevant meteorological features, heat demand in the past and weather forecast. In this paper, we evaluate state-of-the-art DL architectures for multivariate one-step and multi-step prediction based on Long-Short Term Memory (LSTM) approach, namely, stacked LSTM, bi-directional LSTM, encoder-decoder and attention models. The initial results of forecasting heat demand and local explanations are provided for the case of small 8MW DHS. For local explanations, Local Interpretable Model-agnostic Explanations (LIME) was successfully validated. [ABSTRACT FROM AUTHOR]

• Historic library indoor microclimate campaign, methodology and results. • Heritage microclimate risk and prediction risk damage application to a heritage building. • Monitoring and alert protocol. This paper aims to illustrate and give an interpretation of the results emerged from a pilot activity developed within the ROCK project, by the Department of Architecture of the University of Bologna, Alma Mater Studiorum. Through this activity, we studied the indoor microclimate of the University Library of Bologna (BUB), in the Archive and in the Lecture Hall, with the aim to detect how these spaces are affected by the influence of factors such as the outdoor climate and the cooling and heating systems. Moreover, the paper presents the customisation of the probes' alert system and of the probes itself, used for a one-year monitoring campaign started on the 20th of December 2018. In addition, we calculated the Heritage Microclimate Risk index, to verify the level of risk to which the heritage in the Library is exposed due to the indoor microclimate, and the Predicted Risk of Damage index, that evaluate the more specific risks of damage to which precise objects hosted in there are exposed. Therefore, this paper enriches the research field of Historic Indoor Microclimate, started in 2013, which concerns issues as preventive conservation and restoration in historic buildings. The new insights about the Bologna University Library facilitate the possibility to draw up a specific 'Indoor Microclimate Management Protocol (IMMP)' aimed at the preventive conservation of manuscripts and books in historical libraries. [ABSTRACT FROM AUTHOR]

HFC refrigerants as R134a, R404A, R407C and R410A are commonly used in heating, air conditioning and refrigeration (HACR) systems since Kyoto protocol. However, they are phased-out due to their high global warming potential (GWP). There are various options to replace high GWP refrigerants, among all hydrofluorolefin (HFO) fluids, such as R1234yf, represents an excellent alternative. With GWP <1, R1234yf is a promising substitute for R134a. This paper presents the most relevant researches concerning the application of R1234yf in the last decade. This review paper regroups experimental and theoretical studies which assess the performance of pure R1234yf as working fluid of the compression systems such as mobile and residential air conditioning, air and water heat pump, domestic refrigerator and freezer. Studies depict that R1234yf can be recommended for small-scale systems instead of R134a, but an optimization process is necessary to achieve the optimum operating conditions. [ABSTRACT FROM AUTHOR]

In this paper, the influence of measurement uncertainties on the key performance indicators f sav and F S C in solar-assisted heating systems is investigated. The impact of temperature, volumetric flow rate, and irradiance sensors with different measurement accuracies is analysed with a combination of Gaussian error propagation and Monte Carlo Analysis. To identify the sensor equipment with best cost–benefit-ratio (BCBR), different sensor combinations are investigated. If f sav and F S C are to be measured, additional sensors must be installed. The resulting costs range from 250 € for an inexpensive equipment to 330 € for recommended BCBR equipment and up to 780 € for the maximum accuracy equipment. For smaller economically dimensioned systems the use of inexpensive sensors results in large uncertainties, e.g. f ˆ sav = (15. 2 ± 13. 7) %. The uncertainties for larger systems are significantly lower, e.g. f ˆ sav = (56. 7 ± 6. 3) %. This is true as well if better sensors are used. Regardless of the system's size, with the BCBR sensor equipment the resulting expanded uncertainties can be reduced by 60 % (relative) compared to the results with the inexpensive sensor equipment. With maximum accuracy sensor equipment the resulting expanded uncertainties can even be reduced by 77 % (relative). The results show the importance of a carefully selected sensor equipment and the influence of the system's size. Inexpensive sensors can lead to large uncertainty ranges for the important key performance indicators f sav and F S C. Thus, these key figures effectively cannot be used for assessing the performance of a solar-assisted heating system. • Accuracy of f sav and FSC strongly depends on installed sensor qualities. • Analysis based on Monte-Carlo method and Gaussian Error Propagation. • Most influential sensors: temperatures in auxiliary and space heating loop. • Commonly used, inexpensive sensors result in very imprecise performance indicators. • Cost-efficient sensor equipment reduces uncertainties by 60% (fsav) and 45% (FSC). [ABSTRACT FROM AUTHOR]

• This study focuses on optimization of an air source transcritical CO 2 heat pump. • Factors influencing the optimal discharge pressure were examined experimentally. • A correlation formula for the optimal discharge pressure was determined. • Compared with the experimental results, the maximum error was less than 10%. • A control strategy for based on degree of superheat correction was proposed. The compressor discharge pressure is an important parameter for optimizing the performance of a transcritical CO 2 heat pump system. In this study, the factors influencing the optimal compressor discharge pressure of an air source transcritical CO 2 heat pump system were examined experimentally. The results showed that the optimal compressor discharge pressure is affected by the gas cooler water inlet temperature and gas cooler CO 2 outlet temperature. Consequently, a correlation formula for the optimal compressor discharge pressure appropriate for a more comprehensive temperature range and higher prediction accuracy was determined based on the experimental data. Compared with the experimental results, the maximum error was less than 10%, which is minor considering the lower gas cooler CO 2 outlet temperature. In addition, a control strategy for the optimal compressor discharge pressure based on the degree of superheat correction was proposed. Subsequently, under variable operating conditions, the air source transcritical CO 2 heat pump crude oil heating system was continuously operated based on this control strategy. The results showed that the compressor discharge pressure agreed with the optimal compressor discharge pressure calculated using the new correlation formula. Compared with the control strategy of constant opening under a variable frequency mode, the results showed that the system could operate under the control strategy proposed in this paper, the thermodynamic perfection of the system being higher. [ABSTRACT FROM AUTHOR]

Heat recovery in industry is limited by thermodynamic and economic factors. Increased heat recovery in an existing heat exchanger calls for higher costs in terms of capital and pumping due to increased exchanger size and pressure drop. One design option to offset the rapid growth of surface area to meet the upgraded heat load is to seek strategies to increase the heat recovery by increasing the heat transfer coefficient with a moderate increase on pressure drop. Compabloc heat exchangers have the construction features that make them suitable for such purposes. This paper presents a new design methodology for this type of exchanger and discusses its application in retrofit projects. The approach exploits the use of utility paths as the simplest and more practical way of identifying energy savings projects. The importance of analysing and quantifying temperature disturbance propagations is discussed. Applications to two case studies demonstrate the economic viability of using compabloc exchangers to achieve large energy recovery and savings. It is demonstrated that with an additional pumping cost of $66,776.12 USD/year, a total surface area of 1140.8 m2 and capital investment of $1062,272.0 USD, 24.8 MW of additional energy can be recovered, saving $5339,675.52 USD/year, giving a payback of 2.8 months. • A practical approach to the use of compabloc heat exchangers in retrofit applications is introduced. • Compabloc exchangers are sized using a new design methodology and new generalised thermohydraulic correlations. • Utility paths and temperature disturbance propagation are important aspects of the approach. • Compabloc exchanger can achieve high heat recovery, energy savings and short payback periods. [ABSTRACT FROM AUTHOR]

The simultaneous energy and food resources management can be a challenging problem for researchers working in this field. Solar dryers are equipment that can employ solar energy in order to dry degradable food for long-term storage. However, these systems should also utilize an auxiliary energy source because of non-availability of continuous access to the solar radiation. In this paper, a cabin solar dryer equipped with a heating element as an auxiliary heat source has been used to dry four types of products. The tested products consist of apple, kiwi, banana slices, as well as quince julienne strips. The experiments were performed in four days during autumn, when the solar energy had a low level intensity and the heating element was employed for aiding the energy supply. Temperature and humidity have been measured using temperature and humidity sensors mounted at the inlet and outlet of the collector and dryer cabin. Then the thermal efficiency of the collector and the cabin is investigated via the energy and exergy analysis, and the thermal performance of the system is analyzed. Lastly, an economic analysis is presented to calculate the production cost of per kilogram of products. The results show that thermal efficiency, drying process exergy, produced exergy and specific moisture evaporation rate (SMER) of julienne strips of quince are higher than those of other products. Although banana slices have better conditions in terms of these parameters among the sliced products. Due to the results, it was found that the quince julienne strips have the highest cost about 1.137 $/kg and the lowest drying rate about 0.188 kg/h. On the contrary, the minimum cost belongs to the apple slices about 0.478 $/kg and the maximum drying rate about 0.3224 kg/h. • Hybrid dryer combined with spiral solar air heater and auxiliary heating system is used. • Four types of products are dried. • The tested products consist of apple, kiwi and banana slices and quince julienne strips. • Energy, exergy and economic analysis are performed. • Thermal performance and the cost of production per kilogram of product are estimated. [ABSTRACT FROM AUTHOR]

The construction sector accounts for 40% of total energy consumption and is increasing. To reduce energy consumption of heating and cooling systems during peak demand while maintaining thermal comfort, phase change materials (PCMs) are used more and more. Appropriate application of PCM and design of latent heat thermal energy storage (LHTES) requires in practice an in-depth knowledge of the thermal properties of PCMs. The aim of the paper is to present the results of experimental determination of the properties of two commercially available, organic PCMs – RT22HC and RT28 HC, using T-history method and pipe Poensgen apparatus. Results of experimental tests showed that these low-temperature PCMs could effectivity store heat and cold in a narrow temperature range of approx. 7 K for RT22 HC and about 3–4 K for RT28 HC. The average measured latent heat values are 190 kJ/kg for RT22 HC and 244 kJ/kg for RT28 HC. The distribution of energy stored in RT22 HC shows the peak in the temperature range of 21–23 °C (with 20–50 kJ/kgK for heating, 22–71 kJ/kgK for cooling). For RT28 HC this range is 27–28 °C (75–130 kJ/kgK for heating, 40–125 kJ/kgK for cooling). The diagrams of enthalpy present small hysteresis (0.5–1 K) in these materials. Thermal conductivity measurements using pipe Poensgen apparatus demonstrated that these PCMs have a low conductivity of 0.12–0.33 W/mK. The presented experimental research is intended to provide the data necessary for the correct design of LHTES with RT22 HC or RT28 HC intended to use in heating and cooling systems and to maintain thermal comfort in buildings. • RT22 HC and RT28 HC were tested using T-history method and pipe Poensgen apparatus. • The average measured latent heat is 190 kJ/kg for RT22 HC, 244 kJ/kg for RT28 HC. • Results of T-history method and three-layer calorimeter are in good agreement. • Pipe Poensgen apparatus was used to determine thermal conductivity of PCMs. • Tested PCMs confirmed their potential to reduce peak energy consumption. [ABSTRACT FROM AUTHOR]

This paper is presented a concept of thermochemical recuperation of waste heat based on hydrogen extraction from liquid organic hydrogen carriers (LOHC), on the example of methylcyclohexane-toluene system. The advantages of this concept is described, for example, a possibility to use a moderate low temperature of waste heat for generation high-exergy "green" hydrogen fuel. To understand the effect of operating parameters on the energy and mass balance, the thermodynamic analysis was performed. The chemical system for hydrogen generation was analyzed via Gibbs free energy minimization method. The thermodynamic analysis was conducted under various operating conditions: temperature of 100–400 °C, pressure of 1–4 bar. Aspen HYSYS software was used for the energy and mass conservation analysis. Sankey diagram for the energy flows is depicted. The results showed that the maximum energy efficiency the thermochemical waste heat recuperation system have in the temperature range above 300–350 °C. In this temperature range, the effect of pressure on the energy balance is negligible and it is recommended for the thermochemical recuperation system to use LOHC with a pressure of 1.5–2 bar. Based on the analysis, it was concluded that the temperature potential of waste heat for about 300–350 °C is enough for the investigated concept. An analysis of a mass balance showed that the decreasing in condensation temperature leads to a significant increasing in the share of condensed toluene from toluene-hydrogen mixture after a reactor. If temperature of a hydrogen-toluene mixture of 20 °C at pressure above 2 bar about 96% of toluene can be condensed after the first condenser. • Concept of thermochemical recuperation based on liquid organic hydrogen carriers (LOHC). • Effect of pressure and temperature on energy and mass balance is studied. • Temperature of waste heat for efficient using of LOHC is 300–350 °C. • Effect of pressure on energy balance of the thermochemical recuperation system is negligible. [ABSTRACT FROM AUTHOR]

The heat pump operated single-stage humidification-dehumidification desalination system, configured with a subcooler and a heat regenerator, has been proven highly effective in improving both freshwater productivity and energy efficiency. To investigate the potential benefits of increasing the number of humidification stages, this paper presents a heat pump operated two-stage humidification-dehumidification desalination system by adding a pre-humidifier. Subcooler and condenser of the heat pump are used as the heat sources of the main humidifier and the pre-humidifier, respectively. Through parametric studies, a comparative analysis is conducted on the thermodynamic and economic performances of both the heat pump operated single-stage system and two-stage system at various operating conditions. The results show that such system modification can greatly improve system performances. Compared to the single-stage system, the maximum freshwater productivity of the two-stage system is 42.89 kg/h, increased by 19.77 %; the peak gain output ratio is 7.93, up by 9.53 %; and the lowest specific electricity consumption is 79.34 kWh/m3, reduced by 15.15 %. Furthermore, the freshwater production cost for the two-stage system, ranging from 7.78 to 13.33 $/m3, is also superior that of the single-stage system, further demonstrating its substantial value in practical product development and market promotion. • A heat pump operated two-stage humidification-dehumidification system is proposed. • Performances of single and two-stage systems are compared at identical conditions. • Freshwater production costs of the two-stage system range from 7.78 to 13.33 $/m3. • The two-stage system is significantly more efficient than the single-stage system. [ABSTRACT FROM AUTHOR]

Packed-bed latent heat storage (PBLHS) system has been widely studied in the solar energy application area due to its properties of solving the time-space mismatch of energy supply and demand. The paper delves into the cyclic thermal performance of PBLHS tanks, seamlessly integrated with flat-plate collectors, to manage building heat loads effectively. A 1D transient mathematic model of PBLHS integrated with the solar collector for a building is established using MATLAB which is validated with the experimental results from the literature. Based on this model, the effect of different sizes, flow rates, inlet temperature thresholds and different heating months are discussed. The results show that: 1). Building heat load can have a significant influence on the thermal performance of the PBLHS system. 2). The optimal size of the tank for a 96 m2 house is 1.0*1.0 m and the optimal flow rate is 0.05 kg/s 3). The weather data can significantly affect the thermal performance of PBLHS, the storage tank heating durations for one week in different heating months are 108.4h, 73.6h,70.8h and 81.7h. These insights are pivotal for the optimal design of PBLHS tanks, paving the way for more efficient building heating solutions. • PBLHS tank integrated with a flat plate operating under heat load is modelled. • Energetic and thermal performance assessments of a PBLHS tank are obtained. • The cyclic operation of the PBLHS system under long-term intermittent loads is presented. • Influences of different mass flow rates, inlet temperature limits and different size tanks are evaluated. • The operation of the PBLHS system under heating seasons is analyzed. [ABSTRACT FROM AUTHOR]

Accurate heating load prediction is essential to supply-demand collaboration in district heating systems and energy sustainability. With the development of the Internet of Things technology, massive monitoring data is collected that provides abundant data sources for the prediction models. However, the missing data from equipment anomalies, network transmissions and the complexity of heat load changing cause difficulty in realizing accurate heat load prediction. Therefore, the hybrid model based on bidirectional long short-term memory network and temporal convolutional network proposed in this paper to improve the accuracy of the heat load prediction from the aspects of reconstruction of missing values and extraction of complex features. The bidirectional long short-term memory algorithm imputes missing values based on bi-directional features of existing data and provides solid data foundation for subsequent training of predictive models. The temporal convolutional network achieves high-level feature extraction and parallel computation, which contributes to the effective modeling of complex changes in heat load and the realization of accurate heat load prediction. Comparative study was conducted with four heat exchange stations of actual environment to evaluate the performance of the prediction model. The results showed the mean absolute percentage error of the hybrid model decreased to 2.47% which is lower than the State-of-the-Art models, such as long short-term memory, temporal convolutional network, and support vector regression etc. The superior results further validated the feasibility of this hybrid model in heat load prediction. • The missing values in heating system were reconstructed by deep learning model. • A hybrid heating load prediction model was proposed considering missing values. • Detailed experiments were conducted to validate the model's superiority. [ABSTRACT FROM AUTHOR]

Hydrogen propulsion is generally treated as the ultimate net zero-emission option for aviation, therein liquid hydrogen storage appears to provide the only feasible solution for aircraft with the constraints imposed by aircraft weight and volume. Hydrogen liquefaction consumes a great amount of energy, which significantly boosts the cost of hydrogen as an aviation fuel. Besides the H 2 chemical exergy for combustion to provide thrust, the H 2 physical exergy in the form of cold energy is also a kind of high-quality clean energy to produce power output, which offers great opportunities to achieve cost-effective use of hydrogen fuel. Thus, this paper presents a Rankine cycle and H 2 direct expansion cycle (RC-DEC) combined power generation thermal management system for the simultaneous utilization of exhaust gas heat exergy and hydrogen fuel cold exergy from the liquid hydrogen-fueled turbojet engine. In the Rankine cycle, the transcritical mode is applied on the hot side while the liquid separation condensation concept is adopted on the cold side to achieve better thermal matchings with heat and cold sources. The hydrocarbon/inert gas binary mixture is proposed as the working fluid of the Rankine cycle. The effects of key thermodynamic parameters and the influence of Para-Ortho hydrogen conversion on system performance are discussed, then a comparison of the mixture working fluid is conducted. Results show that there exists an optimal separation temperature ratio and condensation pressure of RC to obtain maximum total net power output. As the DEC expander inlet pressure increases, the total net power output first increases and then levels off. The introduction of the Para-Ortho hydrogen conversion has a negligible impact on net power output but leads to a significant reduction in the exergy efficiency, which is attributed to the cold energy release nature of Para-Ortho hydrogen conversion. The results of the working fluid comparison indicate that the optimal inert gas retardant for CH 4 is Kr, while those for C 2 H 6 and C 3 H 8 are Xe to achieve the maximum net power output and exergy efficiency of the proposed power generation system. Among them, C 2 H 6 /Xe(0.6/0.4) obtains the maximum net power output of 2717.9 kW and maximum exergy efficiency of 33.1%, which suggests an opportunity to provide megawatts of electrical power for the aircraft in place of the APU. • RC-DEC combined thermal management system is proposed for LH 2 turbojet engine. • The hydrocarbon/inert gas binary mixture is proposed for LH 2 cold exergy recovery. • The influence of the Para-Ortho hydrogen conversion on the system is revealed. • The optimal inert gas retardant for the selected hydrocarbons is determined. [ABSTRACT FROM AUTHOR]

As the coupling between power distribution systems (PDSs) and district heating systems (DHSs) becomes tighter, it is critical to develop a coordinated strategy for load restoration in integrated electric and heating systems (IEHSs) after natural catastrophes. Similar to PDS reconfiguration, DHSs can modify network topology by remotely operating the ties and sectionalizing valves. A coordinated reconfiguration with soft open points (SOPs) is proposed in this paper for resilience-oriented restoration in IEHSs, which mitigates the fault propagation during fault isolation and explores the flexibility of network topology variation with SOPs for load restoration. To guarantee the privacy of electric and heating systems, we propose an adaptive alternating direction method of multipliers (ADMM), which divides the original problem into PDS and DHS subproblems. The proposed algorithm can intelligently dispatch SOPs and switches in the PDS sub-problem and valves in the DHS subproblem. Comprehensive case studies are carried out to illustrate the effectiveness of coordinated reconfiguration with SOPs for load restoration and verify the proposed algorithm. When considering coordinated reconfiguration with SOPs under the PDS fault scenario, the resilience metrics value increases by 9.6% compared to only PDS reconfiguration. • A Distributed coordinated load restoration strategy in integrated electric and heating systems is proposed. • Soft Open Point flexibility is fully exploited to improve load restoration levels. • Coordinated reconfiguration of the PDS and DHS is provided to improve service restoration level. • The adaptive ADMM is utilized to guarantee the privacy security of electric and heating systems. [ABSTRACT FROM AUTHOR]

• A two-layer control method is proposed to deal with calculation complexity. • The clustered temperature transfer processes of bitumen tanks are analyzed. • A data-driven method is introduced to enhance computational efficiency. • A real-time predictive control method is developed to deal with uncertainties. Uncertainties and computational complexity are two growing challenges in scheduling industrial heating loads. In this paper, a data-driven real-time predictive control approach is proposed to deal with these challenges in the industrial scheduling of bitumen tanks. Specifically, predictive control technology is utilized to leverage the updated information to mitigate the negative impact of past uncertainties in equipment parameters and external environmental factors, which may lead to temperature constraint violations in the bitumen tank operation processes. Meanwhile, a data-driven method using artificial neural networks (ANN) is developed to ensure efficient computation for real-time predictive control. Moreover, a two-layer control method is devised to reduce the calculation time for day-ahead optimal scheduling of a large scale of bitumen tanks, aiming to generate sufficient high-quality data for training ANN. In the two-layer control method, the clustered temperature transfer processes of bitumen tanks are analyzed and modeled for the first time. Simulation results indicate that the two-layer control method can significantly reduce the computational time required for the day-ahead optimal scheduling of bitumen tanks, facilitating the generation of a large amount of high-quality data for training ANN. Subsequently, the application of ANN enables real-time predictive control, helping to eliminate the negative impact of uncertainties. [ABSTRACT FROM AUTHOR]

Agricultural greenhouses play a crucial role in addressing the threat of climate change to agricultural systems. The greenhouse systems control exhibits nonlinear characteristics and large lag, both affecting the regulation of the greenhouse thermal environment. In this paper, a control strategy was designed to set the dynamic reference value of the control objective of the greenhouse model, considering factors such as solar radiation and the heating capacity of water body. A complete greenhouse model was developed using TRNSYS, and then the model predictive control building and optimization were implemented through MATLAB. The control effects of traditional proportional-integral-differentiation control, initial model predictive control, and optimized model predictive control were compared. The results showed that the regulation of greenhouse temperature was improved by 10.6 % in the coldest mouth compared to the conventional proportional-integral-differentiation control by the optimized model predictive control. During a typical cold month, the violation of constraints was reduced by 29.7 % by dynamically setting the target of the greenhouse with the optimized model predictive control. The performance of greenhouse climate control is enhanced by the proposed optimized model predictive control method, ensuring a stable regulation of the crop growth environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combining global simplified and local turbulence models to calculate flow details. • Analysis of the low-pressure heater pipe failure causes. • Simulate the low-pressure heater with the porous medium model. • Obtained flow information in the damaged local area. Low-pressure heaters are critical heat exchange equipment in thermal and nuclear power generation. The high-speed steam flow in the low-pressure heaters induces pipe vibration, causing pipe failure. The large size and complex flow make it hard to calculate directly. This paper employs a combined method of the porous medium and local models by substituting the boundary to calculate and prove steam flow trajectory and velocity are consistent with the actual situation. The analysis of the turbulent kinetic energy exhibits that the primary causes of pipe vibration are the periodic vortex shedding and the impact of the impingement plate on the pipes. The stress analysis indicates that the loosening of the pipes leads to a 368 times amplification of the shear stress by 0.1 MPa. The most crucial step in solving such a problem is to strengthen the fixation of the pipes, especially near the shell region. [ABSTRACT FROM AUTHOR]