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The diaphragm pump is commonly utilized in the small-scale ammonia-water power cycle for pumping the liquid from absorber to evaporator. The electricity consumption and possible leakage of such a pump influence the system efficiency and reliability significantly. In order to find an alternative "pump" with high reliability and low cost, a gravity assisted thermal driven "pump" (GTP), which is consisted of three top-down organized units connecting absorber and evaporator separately, is designed. With the charging and discharging phases, the pressure in each unit fluctuates, and the level of the liquid increases and decreases alternately by the function of gravity. The results of the system show that the net work and thermal efficiency are 10.68 kW and 9.9%, respectively, when the evaporator and absorber are at 140 °C/4000 kPa and 25 °C/800 kPa separately. The optimal net work, thermal efficiency and exergy efficiency are improved by 4.87%, 3.62% and 10.06% respectively compared with the conventional cycle. An application of the GTP power cycle with the capacity of 10 kW driven by the biomass boiler is analyzed, and the results show that the electricity produced by 645 kg biomass pellets can support more than 12 households per day. Image 1 • An ammonia-water power cycle without electricity driven pump is proposed. • Gravity assisted thermal driven "pump" is designed to replace electric pump. • The maximum energy and exergy efficiency of new type cycle are 10.3% and 33.2%. • Performance of new type cycle is improved compared with conventional cycle. [ABSTRACT FROM AUTHOR]

Abstract The composite sorbents of MgSO 4 -impregnated zeolite 13X and activated alumina are developed for thermal energy storage (TES) with different temperature ranges. The sorption and desorption characteristics of raw and MgSO 4 -impregnated activated alumina are studied, and the performances of the selected sorbents are tested in a closed-system TES device. The results are compared with those of raw and MgSO 4 -impregnated zeolite 13X. It is shown that the impregnated MgSO 4 improves the overall TES performances of zeolite 13X and activated alumina. Compared to the raw host matrices, the impregnated MgSO 4 remarkably accelerates the temperature-rising rate of zeolite 13X to about three times and improves the temperature lift of activated alumina by 32.5%. The experimental energy storage densities of MgSO 4 -impregnated zeolite 13X and activated alumina are 123.4 kWh m−3and 82.6 kWh m−3, respectively. The sorption temperature region of activated alumina is more aligned with the preferred hydration temperature of MgSO 4 in comparison with zeolite 13X. The hydration characteristics of MgSO 4 can resolve the solution leakage issue of open systems. Thermodynamic analysis is conducted to evaluate the performances of the TES device with different sorbents. It is found that entransy can be used to assess thermally and electrically driven TES systems reasonably. Highlights • MgSO 4 -impregnated zeolite 13X and activated alumina are developed and tested. • The impregnated MgSO 4 improves the overall performances of the host matrices. • Sorption temperature of activated alumina is more suitable for hydration of MgSO 4. • Hydration characteristics of MgSO 4 can resolve solution leakage of open systems. • Entransy can assess thermally and electrically driven TES systems reasonably. [ABSTRACT FROM AUTHOR]

The pore shape affected by initial contact angle of a bubble entrapped by a solidification front is predicted. Initial contact angle affects bubble nucleation, surface area and solute transport across the bubble cap, solid gas pressure in the pore and shape of pores in solid. Porosity influences microstructure and functional properties of materials, etc. This work accounts for solute transport across the coupled shape of cap in balance of pressures and physico-chemical equilibrium. Similar to previous work, it shows that pore shape depends on directions and magnitudes of solute across the cap. In contrast to Case 2, solute transport in Case 1 is from the pore into surrounding liquid in the early stage. The results find that a decrease in initial contact angle expedites bubble entrapment in Case 1. Solute gas pressure in the pore further exhibits three stages for initial contact angle greater than 90°. Significant drops occur in the early and late stages. In the middle stage, where contact angle is near 90°, solute concentration at the cap is about initial solute concentration in liquid, and responsible for length of the pore. Except for initial contact angle less than 90°, an isolated pore cannot be formed in Case 2. The predicted pore shape agrees with experimental data. [ABSTRACT FROM AUTHOR]

The shape of a pore, resulting from a bubble entrapped by a solidification front, for different Henry’s law constants at the cap is predicted in this work. Henry’s law, indicating an interfacial physico-chemical equilibrium, is essentially required to relate solute concentration in liquid at the cap by solute gas pressure in the pore. Pore formation and its shape in solid influence contemporary issues of biology, engineering, foods, geophysics and climate change, etc. This work applies a previous model accounting for mass and momentum transport of solute across a self-consistently determined shape of the bubble cap subject to different cases characterized by different directions and magnitude of solute transport across the cap. Case 1 is referred to solute transport from the pore across cap to surrounding liquid in the early stage. Cases 2a and 2b, corresponding to low and high Henry’s law constants, respectively, indicate opposite directions of species transport across the cap. An increase in Henry’s law constant decreases pore radius and time for entrapment in Case 1. The pore cannot be entrapped as a pore in solid in Cases 2. The predicted pore shape in solid agrees with experimental data. Understanding, prediction and control of the growth of the pore shape have therefore been obtained. [ABSTRACT FROM AUTHOR]

An ammonia-water power cycle with a distillation stage is proposed, two Kalina cycles and one Organic Rankine Cycle (ORC) are selected for comparisons under two scenarios: medium (346 °C) and low (146 °C) heat source temperatures. The optimization efforts are aimed at maximizing net power production for all concerning cycles, the results show that the proposed cycle can produce 9% and 8% more power than the reference Kalina cycles, while a better thermal performance is achieved for thermal efficiency and exergy efficiency. When the proposed cycle compares with ORC, the amount of net power can be produced is improved by 9% and 3%, respectively. On the other hand, the thermal performance of Kalina cycles and ORC are largely relied on the design of internal heat exchangers, requiring relatively larger size of internal heat exchangers. The proposed cycle, however, is much more compact because of less amount of internal heat transfer needed, leading to less irreversibilities. The proposed cycle can be further simplified by using a solution cooled absorber which eventually decreases the system complexity. A parametrical study shows that the proposed cycle has a better capability of adaptation to a wider temperature range of heat source conditions while maintaining a better performance. [ABSTRACT FROM AUTHOR]

A high efficient semi-open system of fresh water production is established with novel consolidated composite sorbent. This device collects 14.7 kg of water with packing 40.8 kg of consolidating sorbents in 0.4 × 0.4 × 0.6 m size of sorbent bed. The consolidated active carbon felt combined with LiCl sorbent and its corrugated filling mode are invented, which has large cycle sorption quantity, excellent heat transfer performance, and enough mass transfer channels. The sorption and desorption performances of device are tested at different experiments conditions. In sorption process, 14.7 kg, 13.6 kg, and 12.5 kg fresh water is obtained under the condition of 85%, 75%, and 65% RH; while in desorption process, 14.5 kg, 13.6 kg and 0 kg water is got under the condition of 90 °C, 77 °C, and 60 °C respectively. This appliance ensures the large adsorbing capacity at 23 °C and 90% RH, and achieves a large amount of desorption (0.65 g/g) between 70 and 80 °C with 8.8 Pa flow resistance. The pressure drop and velocity distribution of the actual operation in the unit structure of sorbent bed are simulated, and the water mass is calculated to analyze the sorption and desorption performances of the device. [ABSTRACT FROM AUTHOR]

LiCl/H 2 O and CaCl 2 /H 2 O show a great potential for sorption air-to-water and thermal energy storage (TES) with their large water sorption capacity. A concept of three-phase composite solid-liquid/gas sorption is proposed by using activated carbon fiber (ACF) felt as a porous host matrix to combine with LiCl and CaCl 2 . Samples with different proportions of salts and varied mass ratios between LiCl and CaCl 2 are developed, and thermal conductivity, sorption kinetics and simultaneous thermal analysis (STA) are experimentally investigated. Results reveal that ACF is a better choice of matrix because water uptake and energy storage density of aforementioned samples are greatly increased. It appears that the composite sorbent of ALiCa30(3:1) is a promising material for sorption air-to-water and TES, with water uptake of 2.98 g g −1 at 25 °C and 90% relative humidity, mass energy storage density of 0.41 kWh kg −1 and volume energy storage density of 223 kWh m −3 . [ABSTRACT FROM AUTHOR]

An innovative resorption system is established and investigated for seasonal thermal energy storage. Solar energy is stored in form of chemical potential in summer whereas the stored energy could be released in form of sorption heat in winter. Working pair of MnCl 2 -CaCl 2 -NH 3 is selected and composite sorbents are developed with expanded natural graphite treated with sulfuric acid as the matrix for heat and mass transfer intensification. It is indicated that the highest effective heat storage density, heat power density and system COP are able to reach 1047 kJ kg −1 , 402 W kg −1 and 0.58 under the condition of 30 °C heat output temperature and 15 °C ambient temperature. Novel resorption thermal energy storage system verifies the feasibility for seasonal energy storage at high ambient temperature in winter, which reveals great potentials for solar energy utilization. Also worth noting that two possible solutions i.e. temperature upgrade mode and sorption-compression mode are analyzed and compared when ambient temperature is relatively low i.e. below 0 °C. Results demonstrate that heat could be supplied in term of −15 °C ambient temperature and 50 °C heat output temperature. Two methods could deal with the issues at low ambient temperature, which have their respective advantages for different applications. [ABSTRACT FROM AUTHOR]

A novel two-stage sorption refrigeration system is established and analyzed, which is driven by heat source with the temperature lower than 100 °C. CaCl 2 -BaCl 2 -NH 3 is selected as working pair whereas matrix of expanded natural graphite treated with sulfuric acid (ENG-TSA) is used for the improved heat and mass transfer performance of composite sorbent. The non-fin filling technique is adopted to decrease mass and volume of sorption reactor, which further improves system compactness. Results show that two-stage sorption refrigeration system is flexibly adapted to different heat source with temperature below 100 °C. COP and SCP of the novel system range from 0.185 to 0.22 and from 50 W kg −1 to 76 W kg −1 , respectively under the condition of 70 °C–90 °C heat source temperature and 5 °C–10 °C evaporation temperature. Performance of novel two-stage sorption refrigeration system is also compared with that of previous type by using the conventional fin tube sorption reactor based on mass and volume of the whole system. It is indicated that the highest improvement of SCP sys and VCP sys for the novel system are able to reach 28.1% and 32.5%, respectively when heat source temperature is 70 °C. [ABSTRACT FROM AUTHOR]

A small-scale pumpless Organic Rankine Cycle (ORC) system driven by the low temperature heat source is established to investigate the overall performance. Hot water temperature from 75 °C to 95 °C is adopted for performance analysis whereas the environmental temperature is about 25 °C. Refrigerant R245fa is selected as working fluid, and scroll expander is employed for power generation. One worth noting fact is that pumpless ORC system shows great potential for low temperature heat recovery. Experimental results indicate that the maximum power output is 232 W, which is obtained at 95 °C hot water inlet temperature. Correspondingly, the average power output is 204 W which is lasted for 6.6 min, revealing the high stability for power generation. For different hot water inlet temperature, the highest energy and exergy efficiency of the system are 2.4% and 13.7%. Besides, performance of novel pumpless ORC system is compared with that of our previous prototype. It shows a remarkable improvement in terms of power output, energy efficiency and exergy efficiency. Power generation process is able to keep constant for 95% of the cycle time. As a result, pumpless ORC may become an alternative solution to low grade heat utilization when compared with conventional small-scale ORC. [ABSTRACT FROM AUTHOR]

In order to improve energy utilization efficiency of low grade heat, a novel gradient thermal cycle for power and refrigeration cogeneration is proposed. The cycle is cascaded with two stages based on different thermal driven temperature. The first stage is pumpless Organic Rankine Cycle (PRC) while the second stage is two-stage sorption refrigerator. R245fa is selected as the working fluid of PRC, whereas CaCl 2 -BaCl 2 -NH 3 working pair is chosen for two-stage sorption refrigerator. Different heat source temperatures from 80°C to 95°C are adopted for analysis and comparison. Results indicate that the highest average power output and cooling effect are able to reach 204 W and 0.91 kW under the condition of 95°C heat source temperature and 10°C refrigeration temperature. For different heat source temperatures, total energy and exergy efficiency of the gradient thermal cycle for power and refrigeration cogeneration range from 9.49% to 9.9% and 10.9% to 11.8%, respectively. For gradient thermal cycle exergy efficiency of heat utilization ranges from 24% to 18.8% which is 126.5% and 70.9% higher than the PRC and two-stage sorption refrigerator, respectively, when the heat source temperature is 80°C. [ABSTRACT FROM AUTHOR]

The method of temperature–heat ( T – Q ) diagram analysis was proposed in this article. In T – Q diagram, the area between two process curves along the temperature axis represents the irreversibility degree of heat transfer, which has the same dimension with entransy dissipation. T – Q diagram can be used to optimize the heat exchange configuration and the heat exchanger network of adsorption refrigeration systems. The proposed T – Q diagram and traditional energy, exergy and entropy analyses were adopted to a multi-stage heat recovery adsorption refrigeration system. Results show that the optimal heat recovery schemes determined through T – Q diagram and cycle entropy production analyses are identical, while T – Q diagram is more intuitional since the analysis procedure is done graphically. T – Q diagram can also be applied to analyze experiment related results of process temperatures, and is capable of giving an estimation of the performance improvement for heat recovery cycle. [ABSTRACT FROM AUTHOR]

A silica gel-water adsorption chiller driven by low-grade heat is developed. System configuration without any vacuum valves includes two sorption chambers, a 4-valve hot/cooling water coupled circuit and a 4-valve chilled water circuit. Each sorption chamber is composed of one adsorber, one condenser and one evaporator. The design of this chiller, especially the design of modular adsorber, is suitable for low-cost industrial production. Efficient and reliable heat and mass recovery processes are also adopted. This chiller is tested under different conditions and it features the periodic variations of temperatures and cooling power. Through the experimental study, the optimal cooling time, mass recovery time and heat recovery time are 720 s, 40 s and 24 s, respectively. Besides, the obtained cooling power, COP and SCP are 42.8 kW, 0.51 and 125.0 W kg −1 , respectively, under typical conditions of 86/30/11 °C hot water inlet/cooling water inlet/chilled water outlet temperatures, respectively. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES) is regarded as one promising technology for renewable energy and waste heat recovery. Among TES technologies, sorption thermal energy storage (STES) has drawn burgeoning attention due to high energy storage density, long-term heat storage capability and flexible working modes. Originating from STES system, resorption thermal energy storage (RTES) system is established and investigated for recovering the heat in this paper. The system is mainly composed of three high temperature salt (HTS) unit beds; three low temperature salt (LTS) unit beds, valves and heat exchange pipes. Working pair of MnCl 2 –CaCl 2 –NH 3 is selected for the RTES system. 4.8 kg and 3.9 kg MnCl 2 and CaCl 2 composite adsorbents are filled in the adsorption bed. Results indicate that the highest thermal storage density is about 1836 kJ/kg when the heat charging and discharging temperature is 155 °C and 55 °C, respectively. Volume density of heat storage ranges from 144 to 304 kWh/m 3 . The highest ratio of latent heat to sensible heat is about 1.145 when the discharging temperature is 55 °C. The energy efficiency decreases from 97% to 73% when the discharging temperature increases from 55 to 75 °C. [ABSTRACT FROM AUTHOR]

A novel MnCl 2 /CaCl 2 –NH 3 two-stage solid sorption freezing cycle is designed and established for the refrigerated truck with the rated power of 80 kW. The conventional sorption/desorption process and the resorption process are combined in the two-stage cycle. Theoretical analysis shows that such a cycle could adapt to the low heat source temperature and the high cooling temperature of the sorption beds very well, which is quite essential for the truck when the running speed and the load are low in summer. The expanded natural graphite treated with sulfuric acid (ENG-TSA) is chosen as the matrix, and composite adsorbents of MnCl 2 /ENG-TSA and CaCl 2 /ENG-TSA are developed. The hot air heated by the electric heater is used to simulate the engine exhaust gas to drive the system. When the hot air, the ambient air and the refrigerating temperature are 230 °C, 30 °C and −5 °C, respectively, the average refrigerating capacity is 2.2 kW in the sorption process. Correspondingly, the COP and SCP are 0.13 and 91.7 W/kg, respectively. The average refrigerating capacity of 1.1 kW in one cycle is gotten, which could meet the required refrigerating capacity of the light refrigerated truck at the low engine load engine in summer. [ABSTRACT FROM AUTHOR]

A 1 kWh lab-scale sorption prototype using LiCl-water was theoretically and experimentally investigated for sorption thermal energy storage. A type of consolidated composite matrix is developed for the system by using AC (activated carbon), LiCl, expanded natural graphite treated with sulphuric acid (ENG-TSA) to increase heat transfer and SS (silica solution) to enhance mechanical strength. Thermal conductivity and permeability were measured first. A two-dimensional model considering the combined heat and mass transfer was developed to predict the sorption kinetics of the reactor. Under the operation condition of a charging temperature of 85 °C and a discharging temperature of 40 °C, the experimentally recovered heat is 2517 kJ, resulting a heat storage efficiency of 93%. The heat storage density is 874 kJ/kg consolidated sorbent or 2622 kJ/kg LiCl. The experimental results of the prototype were compared with the simulated results. The established two-dimensional model proves to be effective since the general evolution trends of experimental and simulated outlet fluid temperatures are in good agreement. An average gap of about 0.4 °C between the experimental and simulated outlet temperature may be caused by the heat loss and the constant pressure assumption. [ABSTRACT FROM AUTHOR]

Thermochemical sorption heat storage technology is an attractive way for thermal energy storage, the application of thermal energy storage technologies improves the mismatch between energy supply and demand in time and space, and reduces adverse environmental impacts. It contributes to the realization of cleaner and more efficient energy systems. For the thermochemical resorption system, MnCl 2 –SrCl 2 /NH 3 was selected as the working pair. A laboratory-scale thermochemical resorption heat storage device was constructed, and the MnCl 2 –SrCl 2 /NH 3 thermochemical resorption system's heat storage capacity under various operating circumstances was assessed. The effect of several factors on the heat storage capacity of the thermochemical resorption system was assessed using comparative studies of operating parameters. Under the low-temperature salt adsorption/regeneration temperatures of 20 °C, 45 °C for discharging, and 177 °C for charging, the maximum value of the total heat storage density is 2027.74 kJ/kg composite adsorbent. The total heat storage efficiency varies from 0.354 to 0.947. This work is beneficial to promote the application of thermochemical sorption heat storage technology in the low-grade thermal energy recovery, and thus improve the efficiency of energy utilization and achieve the energy-saving as well. [ABSTRACT FROM AUTHOR]

Heat recovery is an effective way to improve adsorption refrigeration system performance due to its easy realization and obvious improvement. Three kinds of heat recoveries (circular heat recovery is complete type and serial and passive heat recoveries are part type) have been applied in recent adsorption refrigerators. Theoretical analysis of three heat recovery methods has been done and results show that serial and passive heat recoveries (part type) are more optimal than circular heat recovery (complete type) when manufacture and cost are considered. Furthermore, a CFD model of a fin-tube type adsorber has been established and simulations of serial and passive heat recoveries have been done. The simulation results show that recovery time of passive heat recovery has an effective range whose value is approximately double of optimum recovery time. Thus, serial heat recovery is more reliable than passive heat recovery. Besides, Optimum recovery time of both serial and passive heat recoveries is approximately equal to the ratio of tube length to heating/cooling flow rate. Contribution distribution of recovered heat has also been analyzed. And the results show that contributions of fluid and tube regions are respectively 89%∼94% and 5%∼10% while contributions of adsorbent and fin regions are negligible. [ABSTRACT FROM AUTHOR]

Abstract: PCM (phase change material) is one of the most popular media in TES (thermal energy storage) system for its high energy storage density and suitable melting temperature. However, its low heat transfer performance leads to low rate of heat stored and released. In this paper, a highly thermal conductive additive of ENG-TSA (expanded natural graphite treated with sulfuric acid) had been used to improve the thermal conductivity of the KNO3/NaNO3 nitrate mixture. Composite samples with different densities and mass fractions of ENG-TSA were produced by the cold-compression method. The thermal conductivities, phase transition properties, thermal stability and micro structures of different samples were evaluated, and results showed that the highest effective thermal conductivity of composite PCM was 50.78 W/(mK), which was 110 times higher than that of salt powder. The additive of ENG-TSA in the PCM caused a slight decrease in latent heat, but there was no remarkable variation in phase change temperature. The salt segregation from the consolidated composite PCM blocks could be controlled at a small value when the densities and mass fractions of ENG-TSA were optimized. [Copyright &y& Elsevier]

• MnCl 2 -NH 3 cycle has the optimal results at high heat source temperature of 175 °C. • Resorption cycle and multi-stage cascading cycle can widen the working range. • The proper combination of working pair is important for multi-stage cascading cycle. • MnCl 2 /CaCl 2 -NH 3 cycle has better adaptability to unsteady heat source. Long-term thermal energy storage is one of the potential and critical solutions to solve the mismatching between thermal energy supply and demand. Even though single-stage sorption cycle, resorption cycle and multi-stage cascading cycle have been proposed for long-term thermal energy storage, the results are difficult to be utilized for selecting optimal cycles because most of them are investigated under different conditions and their performances are not compared under the same criterion experimentally. Herein, the experimental comparative study of different energy storage cycles is implemented for a wide range of heat source temperature and output temperature. For cycles with CaCl 2 /expanded nature graphite treated by the sulphuric acid (ENG-TSA) sorption bed as the output side, CaCl 2 /NH 4 Cl-NH 3 cascading cycle has distinct advantage on effective discharging time. Under the general working conditions with relatively high heat source temperature and low output temperature, CaCl 2 -NH 3 sorption cycle is the optimal choice. For cycles with MnCl 2 /ENG-TSA sorption bed as the output side, MnCl 2 -NH 3 sorption cycle has the maximum thermal energy storage density, thermal energy storage efficiency and temperature lift of 420 kJ·kg−1, 0.51 and 15.0 °C, respectively, at high heat source temperature of 175 °C. Under the critical conditions such as the heat source temperature lower than 155 °C, MnCl 2 /CaCl 2 -NH 3 cascading cycle is more suitable and shows optimum adaptability to unsteady heat source. The experimental results exhibit the suitable working range of heat source temperature and output temperature for different cycles, and the guidance is revealed for selecting optimal cycles for different types of low-grade thermal energy. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this paper is to present the performance analysis of a multifunction heat pipe type adsorption ice maker with activated carbon–CaCl2 as compound adsorbent and ammonia as refrigerant. For this test unit, the heating, cooling and heat recovery processes between two adsorbent beds are performed by multifunction heat pipes. A novel mass and heat recovery adsorption refrigeration cycle is developed. When mass recovery process is implemented before heat recovery process, the performance of the cycle with novel mass and heat recovery processes is much better than that for the cycle with the conventional mass and heat recovery processes. The experimental results show that the former cycle can increase the coefficient of performance (COP) and specific cooling power (SCP) by more than 17% compared with the latter cycle. In comparison with the basic adsorption cycle, the mass and heat recovery cycle can enlarge the cycled refrigerant mass and reduce the power consumption of boiler; the COP and SCP were improved by more than 11% when the mass recovery time was 20 s, while at the optimal mass recovery time of 40 s, the COP improvements for conventional and novel mass and heat recovery cycles are 43.8% and 68.7%, respectively. It was concluded that the novel mass and heat recovery processes are more beneficial to improve the performance of adsorption refrigeration system in comparison with the conventional mass and heat recovery processes. [Copyright &y& Elsevier]

• Long-term thermal energy storage for solar energy and exhaust gas are analyzed. • The highest sorption reaction temperature of bi-salt sorption is higher than MnCl 2. • The maximum COP h can reach about 0.7 for both working conditions. • The energy storage density is almost twice that of conventional resorption system. In this study, a bi-salt sorbent was observed to exhibit better adaptability to the heating and cooling temperatures than conventional single-salt sorbents. A reactor filled with the bi-salt sorbent of CaCl 2 and MnCl 2 was designed, and the performance for long-term thermal energy storage, which included several months of seasonal energy storage and a few days of exhaust gas heat storage in winter, was analyzed. The thermal energy charging rate under both working conditions increased with the heating temperature; however, the COP h exhibited a downward trend. The COP h of seasonal energy storage was maintained above 0.5, and the COP h of exhaust gas heat storage was slightly higher at approximately 0.7. For both working conditions, the average heat-producing power in 50 min increased to approximately 9 kW, and the energy-storage density increased to approximately 1900 kJ∙kg−1, which was approximately 100% higher than that of existing resorption systems with single-salt sorbents. [ABSTRACT FROM AUTHOR]

The CCHP system driven by biomass energy is essential for mitigating the fossil energy crisis and reducing CO 2 emission. But few research work focuses on the micro-scale system due to the limited efficiency. In this paper an efficient household CCHP system is designed, which is driven by the water steam (100 °C-120 °C) from the biomass boiler and is consisted of an R245fa power cycle with a gravity assisted thermal driven "pump", a single-pressure R134a/DMF/He diffusion absorption refrigeration cycle, and several heat exchangers for heating supply. The models of the system are constructed, and the energy, economic and environmental indexes are evaluated. The results reveal that the higher temperature of heat source and the lower temperature of ambient could improve the thermal efficiency of the CCHP system, and realize the lower cost and CO 2 emission. The highest thermal efficiency of the CCHP system can reach to 55.26%. The quarterly energy saving for summer of a 100 m2 isolated house of a rural family can reach to 5059 kW ⋅ h (497 kW ⋅ h for cooling, 3154 kW ⋅ h for heating and 1408 kW ⋅ h for power generation), which can save about 3121.40 RMB electricity bill and reduce 0.15 t CO 2 emissions. Image 1 • A gravity assisted thermal driven "pump" is designed to replace the electric pump in power cycle. • A single-pressure R134a/DMF/He diffusion absorption refrigeration cycle is adopted. • Performance of the CCHP system under different seasons is analyzed. • The highest thermal efficiency of the CCHP system can reach to 55.26%. • The quarterly energy saving (summer, 100 m2) is about 5059 kW•h. [ABSTRACT FROM AUTHOR]

Abstract Air water harvesting (AWH) is a prospective way to make people live in extreme conditions, such as arid desert and remote islands. However, the refrigeration-based AWH suffers from ineffectiveness at low humidity, while the current sorption-based solar driven AWH has low area specific water production. To provide affordable water, it is essential to design universal and scalable systems to effectively capture moisture from air year-round with less energy consumption at different locations. Here we develop a theoretical framework and demonstrate a scalable prototype on the sorption-based AWH. The prototype adopts a temperature-insensitive and RH -broadband desiccant, achieving a large water harvesting capacity in different regions. Scalable modular sorbers with sinusoidal honeycomb structure are used. The prototype harvests ca. 38.5 kg fresh water per day, consuming ca.7.2 MJ heat/kg fresh water. The performance analyses show that our device can harvest freshwater universally, which is a promising solution to relieve the thirsty world. Highlights • The entire mechanisms of AWH from materials level to system scale level are shown. • A thermodynamic chart is first constructed on a modular sorption-based AWHs. • High water harvesting capacities are proved all year round at various areas. [ABSTRACT FROM AUTHOR]

A sorption thermal energy storage (TES) device for domestic heating is presented in this article. The TES device adopts the new design scenario with valve-less adsorber and separate reservoir to eliminate the large-diameter vacuum valve for vapor flow, which decreases the cost, reduces the vapor flow resistance, and improves the system reliability. The device is charged by electric heater, which can add much flexibility to the building energy system as well as contribute to the valley filling and peak shaving from the demand side management. The newly developed composite sorbent of zeolite 13X/MgSO 4 /ENG-TSA (expanded natural graphite treated with sulfuric acid) with the salt mass fraction of 15% in the zeolite 13X/MgSO 4 mixture is tested and used in the TES device (denoted as XM15/ENG-TSA). Experimental results show that the TES device with XM15/ENG-TSA has the energy storage density of 120.3 kWh m −3 at 250 °C charging temperature and 25–90 °C discharging temperature. The temperature lift is as high as 65–69 °C under the adsorption and evaporating temperatures of 25 °C. The impregnated MgSO 4 dramatically improves the temperature rising rate during the adsorption heat recovery process, but the specific energy storage capacity of XM15/ENG-TSA is similar to that of zeolite 13X/ENG-TSA. The effect of the impregnated MgSO 4 suggests that MgSO 4 can be used for low-temperature TES to relieve the self-hindrance of the hydration reaction. [ABSTRACT FROM AUTHOR]

A novel resorption cycle with internal heat recovery process is proposed, which is expected to further explore potentials of power and refrigeration cogeneration. Two sets of basic resorption refrigeration cycles are adopted, which are integrated with turbine/expander to realize quasi-continuous output in both half cycles. An improved cogeneration efficiency could be obtained with safety feature. Different ammonia composite sorbents with better heat and mass transfer performance are selected to investigate the overall performance when heat source temperature is in the range from 200 °C to 360 °C. It is indicated that energy efficiency for power generation is able to reach up to 0.263 at 360 °C heat source temperature while refrigeration coefficient of performance could achieve up to 1.31 at 200 °C heat source temperature. The optimal total exergy efficiency of novel resorption cogeneration cycle is as high as 0.74 by using working pair of FeCl 2 -CaCl 2 -BaCl 2 at 240 °C heat source temperature. Compared with other sorption cycles for power and refrigeration cogeneration at similar heat source temperatures, the proposed resorption cycle exhibits the highest exergy efficiency, which is about 30% higher than that of water-ammonia sorption cogeneration cycle, and twice higher than that of basic resorption cogeneration cycle. [ABSTRACT FROM AUTHOR]

Expanded natural graphite and carbon coated nickel are selected as the additives in the development of novel composite sorbent. Improved thermo-physical properties of composite strontium chloride result in a faster sorption reaction rate than that without using carbon coated metal. A case study of ammonia-based resorption power generation cycle with two identical reactors is analyzed in terms of sorption characteristics of composite sorbents. Power could be generated in both half cycles, which greatly enhances working versatility and thermal efficiency. It is indicated that additive of carbon coated nickel has a positive influence on performance of resorption power generation cycles. Energy and exergy efficiency of basic resorption cycle range from 0.072 to 0.116 and from 0.402 to 0.737, respectively. Basis resorption cycle for power generation is also compared with improved resorption cycle by using different composite sorbents. Increment between improved and basic resorption cycle by using the sorbent without carbon coated nickel is larger than that using that with carbon coated nickel. Energy density by using novel composite sorbent is improved by up to 20% based on mass and volume of sorption reactor. Through reheating process, performance of basic resorption cycle is further improved by 3–5 times. [ABSTRACT FROM AUTHOR]

A novel composite strontium chloride (SrCl 2 ) is developed with porous material of expanded natural graphite (ENG) and nanoparticle of carbon coated nickel (Ni@C) as the additives. Thermo-physical properties such as thermal diffusivity, thermal conductivity and permeability are investigated and analyzed. The highest thermal diffusivity could reach 6.2 mm 2 ⋅s −1 . Correspondingly the highest thermal conductivity is 4.03 W ⋅ m −1  ⋅ K −1 , which is about 20 times higher than that of granular SrCl 2 . Permeability of novel composite SrCl 2 ranges from 1.31 × 10 −9 m 2 to 1.07 × 10 −13 m 2 . Moreover, samples with Ni@C have better sorption performance in ammonia than those without Ni@C due to the improved heat and mass transfer performance. Ammonia sorption quantities of novel composite SrCl 2 range from 0.39 kg⋅kg −1 to 0.67 kg⋅kg −1 when evaporation temperature varies from −15 °C to 15 °C. The addition of ENG and Ni@C shows great potentials for sorption refrigeration by adjusting the concentration swing. [ABSTRACT FROM AUTHOR]

Innovative modular sorption and resorption thermal cell are presented for cold and heat cogeneration. Expanded natural graphite treated with sulfuric acid is selected in the development of composite sorbents for improved heat and mass transfer performance. It is indicated that thermal conductivity and permeability range from 11.9 W m −1 K −1 to 36.5 W m −1 K −1 and from 1.04 × 10 −14 m 2 to 8.02 × 10 −11 m 2 . Sorption characteristics of composite sorbents are also investigated. Results demonstrate that MnCl 2 -CaCl 2 -NH 3 reveals the best sorption performance under the condition of 130–150 °C heat source temperature and −20 °C to 5 °C evaporation temperature. Sorption quantities of sorption and resorption working pairs range from 0.169 kg kg −1 to 0.499 kg kg −1 . Based on testing results, energy density and power density of modular resorption thermal cell are compared with that of sorption thermal cell. Results indicate that heat density ranges from 580 kJ kg −1 to 1368 kJ kg −1 whereas cold density ranges from 400 kJ kg −1 to 1134 kJ kg −1 . Simultaneously, heat and cold power density range from 322 W kg −1 to 1502 W kg −1 and from 222 W kg −1 to 946 W kg −1 . Both sorption and resorption thermal cell have their own advantages, which are flexible connected for scaling applications. [ABSTRACT FROM AUTHOR]

Novel composite strontium chloride is developed with expanded natural graphite and carbon coated nickel as the additives. It is indicated that expanded natural graphite and carbon coated nickel are conducive to heat and mass transfer performance, which result in improved sorption characteristic. For composite sorbents with carbon coated nickel, thermal conductivity and permeability range from 0.57 W · m −1 K −1 to 1.93 W m −1 K −1 and from 2.98 × 10 −10 m 2 to 2.71 × 10 −13 m 2 . Novel composite strontium chloride with carbon coated metal enjoys the faster desorption and sorption reaction rate than that without carbon coated metal. For different evaporation temperatures, sorption quantity of novel composite strontium chloride ranges from 0.28 kg kg −1 to 0.7 kg kg −1 . Based on testing results of sorbents with carbon coated nickel, a promising sorption thermal cell is developed and analyzed for combined cold and heat storage, which greatly enhances the versatility and working reliability. Under different working conditions, cold and heat density range from 384 kJ kg −1 to 811 kJ kg −1 and 549 kJ kg −1 to 1648 kJ kg −1 . Modular sorption thermal cell could be flexible connected to sorption battery for scaling applications, which reveals great potentials for renewable energy utilization and waste heat recovery. [ABSTRACT FROM AUTHOR]

We present an ab initio method to calculate elastic quantum transport at the nanoscale. The method is based on a combination of density functional theory using plane wave nonlocal pseudopotentials and the use of auxiliary periodic boundary conditions to obtain the scattering states. The method can be applied to any applied bias voltage and the charge density and potential profile can either be calculated self-consistently, or using an approximated self-consistent field (SCF) approach. Based on the scattering states one can straightforwardly calculate the transmission coefficients and the corresponding electronic current. The overall scheme allows us to obtain accurate and numerically stable solutions for the elastic transport, with a computational time similar to that of a ground state calculation. This method is particularly suitable for calculations of tunneling currents through vacuum, that some of the nonequilibrium Greens function (NEGF) approaches based on atomic basis sets might have difficulty to deal with. Several examples are provided using this method from electron tunneling, to molecular electronics, to electronic devices: (i) On a Au nanojunction, the tunneling current dependence on the electrode–electrode distance is investigated. (ii) The tunneling through field emission resonances (FERs) is studied via an accurate description of the surface vacuum states. (iii) Based on quantum transport calculations, we have designed a molecular conformational switch, which can turn on and off a molecular junction by applying a perpendicular electric field. (iv) Finally, we have used the method to simulate tunnel field-effect transistors (TFETs) based on two-dimensional transition-metal dichalcogenides (TMDCs), where we have studied the performance and scaling limits of such nanodevices and proposed atomic doping to enhance the transistor performance. [ABSTRACT FROM AUTHOR]

LiCl/H 2 O shows a great potential for sorption thermal energy storage with its large water sorption capacity. However, as a highly hygroscopic salt, LiCl is likely to turn into liquid solution when it contacts with water vapor. A new type of consolidated composite sorbent was developed, by using activated carbon (AC) as a porous host matrix to carry LiCl, mixing with expanded natural graphite treated with sulfuric acid (ENG-TSA) to increase heat transfer and adding silica solution (SS) as a binder to enhance mechanical strength. Samples with different densities and varied mass ratios between different elements were prepared and related characteristics including equilibrium water uptake, thermal conductivity, TGA/DSC simultaneous thermal analysis and kinetic performance were investigated. Results reveal the existence of an obvious sorption plateau corresponding to formation of LiCl ⋅ H 2 O, as well as two sharp increase of water uptake related to hydration reaction and three-phase deliquescence processes respectively. Activated carbon is a better choice of matrix compared with silica gel, with a water uptake up to 0.97 g/g at 30 °C and 1660 Pa. It is proved that among the four elements in the consolidated composite (AC, LiCl, ENG-TSA, silica solution), LiCl is responsible for almost all the water uptake effect. Addition of other elements do not influence the equilibrium water uptake of LiCl. Variation of bulk densities from 462 to 820 kg/m 3 displays thermal conductivities from 2.0 to 2.83 W/(m K), improving that of loose-packed AC–LiCl composite by at least 14 times. [ABSTRACT FROM AUTHOR]

Thermal energy storage is a necessary technology for the application of renewable energy and low-grade thermal energy. Chemical heat storage has been proved to be a feasible and promising method to store thermal energy. As compared to other thermal energy storage methods, chemical heat storage exhibits high energy storage density as well as feasibility for long-duration energy storage. In this paper, the basic principle of the chemical heat storage is firstly elaborated. Then the selection criteria of the chemical reaction are given. The aim of this review is to provide an insight into the promising candidate reactions for chemical heat storage application. The associated reversible chemical reactions available for thermal energy storage systems are summarized. Ongoing research and development studies illustrate that chemical heat storage is a very favorable option for the different application when diverse promising candidate reactions are selected. As working temperature is one of the key parameters for thermal energy storage systems, emphasis is given to the judgment of application temperature range for chemical heat storage. The determination of applicative temperature range of reversible chemical reactions is discussed. Besides, the challenge and prospect of the chemical heat storage technology are analyzed in the paper. [ABSTRACT FROM AUTHOR]

Highlights: [•] We present theoretical calculations for 250 atom-model of amorphous GaN x As1−x . [•] Topology analysis revealed disordered tetrahedral characteristic for all systems. [•] Electronic structure of the systems supports the BAC is provided for the first time. [•] Results are in good agreement with experiments. [•] We conclude that CRN provides an ideal initial network for amorphous materials [ABSTRACT FROM AUTHOR]

Abstract: A novel CaCl2/expanded graphite-NH3 adsorption refrigerator is developed and tested. Only three valves are installed in this refrigerator and they all work at the same positive pressure condition, so the operating reliability of the refrigerator is greatly improved. The experimental results show that the refrigerating power QCP, COP, SCP, electricity COPEl, and volume refrigerating density QCP-V of the refrigerator are 11.4kW, 0.27, 422.2W/kg, 32.6 and 57kW/m3, respectively, under the following conditions: the temperature of heating vapor is from 120°C to 140.3°C, the cooling water temperature is 25°C, the evaporation temperature is −15°C, the heating/cooling time is 25min including 45s mass recovery time. The SCP and volume refrigerating density of this refrigerator are about 1.8times and 1.5times that of the maximum of the former test results by other researchers. [Copyright &y& Elsevier]

Abstract: The performance of a solid sorption icemaker is investigated. CaCl2/activated carbon was used as compound adsorbent and ammonia was employed as adsorbate. The influence of operating conditions (cooling water temperature, mass recovery and heat pipe heat recovery, etc.) on the mass of ice, SCP (specific cooling power) and COP (coefficient of performance) was experimentally assessed. At the desorption temperature of 126°C, cooling water temperature of 22°C, ice produced temperature of −7.5°C, 40s of mass recovery and 2min of heat pipe heat recovery, the mass of ice, SCP and COP values are 17.6kg/h, 369.1W/kg and 0.2, respectively. [Copyright &y& Elsevier]

Abstract: This paper presents experimental data on the thermal conductivity for three types of adsorbent, namely, pure CaCl2 powder, simple composite adsorbent and consolidated composite adsorbent. The thermal conductivities were measured by the “hot wire method” at a fixed pressure and temperature under an ammonia atmosphere. Effective thermal conductivities of the expanded graphite–CaCl2 · nNH3 (n =2, 4, 8) consolidated composite adsorbent are in the range of 7.05–9.2Wm−1 K−1, which are significant higher values than those of the powders bed of 0.3–0.4Wm−1 K−1. The obtained results show that the composite adsorbent thermal conductivity λ has a strong dependence on the bulk density, the weight fraction of expanded graphite and the ammoniated state of CaCl2. [Copyright &y& Elsevier]

Abstract: Adsorption performances and thermal conductivity were tested for three types of adsorbent: Pure CaCl2 powder, simple composite adsorbent and consolidated composite adsorbent. The simple composite adsorbents show better adsorption performance because the additive of expanded graphite in CaCl2 powder has restrained the agglomeration phenomenon in adsorption process and improved the adsorption performance of CaCl2. The consolidated composite adsorbent are suitable to be used as adsorbent for ice maker on fishing boats because they have higher thermal conductivity, larger volumetric cooling capacity, higher SCP values and better anti-sway performance than simple composite adsorbents. Thermal conductivity of the consolidated composite adsorbent is 6.5–9.8Wm−1 K−1 depending on the molding pressure, ranging from 5 to 15MPa, which is about 32 times higher than the thermal conductivity of CaCl2 powder. The volumetric cooling capacity of consolidated composite adsorbent is about 52% higher than the best result obtained for CaCl2 at the evaporating temperature of −10°C. The SCP of the consolidated adsorbent increases of about 353% than CaCl2 powder from simulation results at T ad=30°C and T ev=−10°C. The consolidated composite adsorbents have good anti-sway performance and they are not easy to be scattered out when the fishing boats sway on the sea. [Copyright &y& Elsevier]

Variabilities of the particulate mass flux and associated 210Pb activity were examined on samples collected from time-series sediment traps deployed in the continental slope area of the East China Sea off northeast Taiwan and in the western South Okinawa Trough (SOT) as a part of the KEEP program. The particulate flux decreases laterally from the continental slope toward the trough, increases vertically toward the bottom at most of the mooring sites, and shows fairly synchronous temporal variations among the traps in each mooring for most of the deployments.The temporal variation of 210Pb is generally smaller than that of the particulate flux in terms of relative change as expressed in standard deviation of the mean of each trap. In the lower slope area, the mean particulate flux varies between 9.5 and 79 g/m2/d, and the mean 210Pb varies between about 44 and 81 dpm/g. In the trough, the mean particulate flux has the smallest values, from 0.06 to 5.7 g/m2/d, while the mean 210Pb has the highest, from 82 to 192 dpm/g. The particulate flux decreases while the 210Pb activity increases from the slope toward the trough. In the trough, 210Pb increases with depth while the particulate flux may show a mid-depth maximum of a nepheloid layer.Although the 210Pb activity increases from the slope toward the trough the 210Pb flux decreases toward the trough because of much greater particulate flux in the slope area. Within the trough the 210Pb flux as determined from the traps is comparable to that determined from the underlying sediments, but on the lower slope, the 210Pb flux determined from the traps is much higher than that obtained from the underlying sediments. Thus a large portion of the particulates and the associated 210Pb may have been transported laterally from elsewhere to the slope area in transit without depositing onto the underlying sediments.Plots of the mean 210Pb flux versus the mean mass flux for each of the traps show positive linear correlation with four distinctive slopes, each representing a mean 210Pb activity of a particular area or a group of traps. In the Mien-Hua canyon the mean activity is about 40 dpm/g; in the SOT the mean value is about 130 dpm/g; on the lower slope the mean values fall in-between those of the canyon and the trough. In the middle traps where the mass flux is higher in a nepheloid layer the mean activity is about 47 dpm/g, while the remaining traps yield a mean of about 65 dpm/g. Taking the mean activity of the canyon and that of the trough as the two end-member values, the slope with a nepheloid layer is a mixture of about 90% canyon and 10% trough materials, indicating the canyon as the major particulate provider for the nepheloid layer. The slope without a nepheloid layer is a mixture of about 70% canyon and 30% trough materials. [Copyright &y& Elsevier]