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Thermoelectric technology is commonly used in waste heat utilization of automotive internal combustion engines and widely combined with solar energy units to form solar thermoelectric generator systems. The structure of the Thermoelectric Generator (TEG) needs to be optimized in order to obtain better performance for wider applications. In this paper, the influence of temperature on the height of PN-type thermoelectric arms was analyzed using an improved one-dimensional heat conduction model with the calculus method. At the same time, both the calculation formula of the maximum output power and the calculation formula of various size parameters of the TEG was derived when the influence of temperature on the performance of thermoelectric materials has been considered. In addition, the relationships among different size parameters were derived to obtain the maximum efficiency. The relationships include the most commonly used classical optimization relationship, that is, when the Seebeck coefficient, thermal conductivity and resistivity are averaged, the relationship is consistent with the classical optimization relationship. By considering the impact of temperature on the performance of thermoelectric materials, an improved calculation formula of the figure of merit (Z) was also given. The new optimization formula was compared with the classical optimization method by taking the maximum output power as the optimization index. In the case study, the temperatures of the cold end and the hot end were set at 330 K and 700 K, respectively. PbTe and PbSe were used as the materials with intermediate temperature, and Bi 2 Te 3 was used as the material with low temperature. Through theoretical analysis, it is found that the maximum output power of the new optimization formula can be higher than that of the classical optimization formula. [ABSTRACT FROM AUTHOR]

Thermoelectricity technology, as a kind of cost-effective and pollution-free power generation solution, is often used for waste heat recovery and utilization. In this paper, the temperature distribution of a Two-stage Thermoelectric Generator (TTEG) under constant temperature conditions has been studied using a one-dimensional heat conduction model. Moreover, by combining the obtained temperature distribution with the three-dimensional size of TTEG, a calculation formula of resistance and voltage was developed based on the calculus method. When the sum of cross-sectional areas of all the PN-type thermoelectric arms respectively in high- and low-temperature layers is constant, the optimal ratio between cross-sectional areas of a single PN-thermoelectric arm respectively in high- and low-temperature layers can be calculated using the proposed formula in this study to achieve the maximum output power. Results also showed the relationship between the heights of PN-type thermoelectric arms and the temperature distributions in high- and low-temperature layers. Using PbTe as the medium temperature thermoelectric material and Bi 2 Te 3 as the low temperature thermoelectric material, a case study was conducted on the PN-type thermoelectrics with the same total height and the same total cross-sectional area. The theoretical calculation results showed that the bigger of maximum output power between the two-stage thermoelectric generator and that of the Segmented Thermoelectric Generator (STEG) is related to the hot and cold end temperature. [ABSTRACT FROM AUTHOR]

In this paper, we show that PO(2, 1) can be represented by invertible split quaternions. We introduce the concepts of t-similarity and t-pseudosimilarity of split quaternions. By such two similarities, we obtain several equivalence relations in split quaternions. We also show that a and b are semisimilar if and only if a2 and b2 are similar. [ABSTRACT FROM AUTHOR]

In this paper, we find the roots of lightlike quaternions. By introducing the concept of the Moore-Penrose inverse in split quaternions, we solve the linear equations axb = d, xa = bx, x a = b x ¯ and axb = x. As applications, we obtain necessary and sufficient conditions for two split quaternions to be similar or pseudosimilar. [ABSTRACT FROM AUTHOR]

Split quaternions are noncommutative and contain nontrivial zero divisors. Generally speaking, it is difficult to solve equations in such an algebra. In this paper, by using the roots of any split quaternions and two real nonlinear systems, we derive explicit formulas for computing the roots of x 2 + b x + c = 0 in split quaternion algebra. [ABSTRACT FROM AUTHOR]

In view of the particularity of offshore operations, a new layered pressure swing adsorption (PSA) method for natural gas purification was proposed. CH4 is enriched in the three-component CH4/CO2/N2 crude mixed gas. The pressure swing adsorption process is based on the traditional method. The adsorption bed is divided into two layers, which are the first layer with activated carbon as the adsorbent to remove CO2 impurities, and the second layer with molecular sieve as adsorbent to remove N2 impurities. The process of PSA was simulated by Aspen Adsorption software. The simulation results show that after the process of double layered PSA, the purity of the product gas CH4 reached 98.7%, and the recovery rate of gas production was 89%. The concentration of CO2 was successfully reduced to 0.23% in the activated carbon layer, and the concentration of N2 was reduced to 1.2% in the molecular sieve layer of the first Tower. [ABSTRACT FROM AUTHOR]

In this work, an artificial neural network (ANN) model based on the experimental data was developed to study the performance of vacuum membrane distillation (VMD) desalination process under different operating parameters such as the feed inlet temperature, the vacuum pressure, the feed flow rate and the feed salt concentration. The proposed model was found to be capable of predicting accurately the unseen data of the VMD desalination process. The correlation coefficient of the overall agreement between the ANN predictions and experimental data was found to be more than 0.994. The calculation value of the coefficient of variation ( CV ) was 0.02622, and there was coincident overlap between the target and the output data from the 3D generalization diagrams. The optimal operating conditions of the VMD process can be obtained from the performance analysis of the ANN model with a maximum permeate flux and an acceptable CV value based on the experiment. [ABSTRACT FROM AUTHOR]

Thispaper presents a simulation study of vacuum membrane distillation(VMD) for desalination. A simulation model was built on the AspenPlus platform as a user defined unit operation for the VMD module.A simplified mathematical model was verified, and the analysis ofprocess performance based on simulation was also carried out. Temperatureand concentration polarization effects are significant in the conditionsof higher feed temperature and/or vacuum pressure. The sign of (PI,f– PI,p), difference of the vapor pressures between the membranes at theinterfaces, is an indicator of the vacuum pressure threshold. Increasingthe vacuum pressure at lower feed temperature is an effective wayto increase the permeate flux and reduce the energy consumption simultaneously. [ABSTRACT FROM AUTHOR]

In this work, a novel concept in freeze desalination (FD) was introduced. Nowadays the total liquefied natural gas (LNG) production capacity has reached 290 Mt/year. Its enormous cold energy released from re-gasification can be used in the freeze desalination process to minimize the overall energy consumption. A process of FD on flake ice maker utilizing LNG cold energy was designed and simulated by HYSYS software. An ice bucket on flake ice maker was chosen as seawater crystallizer mainly due to its continuous ice making and removing ice without heat source. A dynamic model of the freezing section has been developed and simulated through gPROMS software. The results show that the consumption of 1 kg equivalent LNG cold energy can obtain about 2 kg of ice melt water. In addition, it is shown that the power consumption of this LNG/FD hybrid process is negligible. [ABSTRACT FROM AUTHOR]

In this paper we show that the answer to problem 3.9 in [Duke Math. J. 69 (1993) 593] is positive when n=2 and negative when n⩾3. [Copyright &y& Elsevier]

The renewable energy mobile offshore platform, which adopts the combined power supply of renewable energy and energy storage, is an important carrier for the development and utilization of marine resources. The randomness of renewable energy generation has a more prominent effect on the bus voltage stability and transient voltage deviation of the power system with small capacity and low inertia. Considering the operation and maintenance characteristics of the offshore platform, a virtual inertia control method for small‐ and medium‐sized wind turbines is proposed. Firstly, by analyzing the characteristics of the renewable energy microgrid of the unattended offshore platform, considering the operating environment with high average wind speed at sea, the mechanical inertia in the wind turbine is selected as the energy source of virtual inertia. The structure of the wind power generation unit is analyzed, and small signal modeling is carried out. A virtual inertia control method based on power droop is proposed, and the rotational inertia and the damping coefficient are obtained from the characteristics of transient and steady‐state analysis of the system. Finally, the DC microgrid experiment platform of the offshore platform is constructed, and it is verified that the proposed method makes full use of the characteristics of the offshore platform to enhance system inertia and improve the operational stability of the offshore platform DC microgrid system. [ABSTRACT FROM AUTHOR]

• The carbon surface weakly adsorbs Hg0, but strongly adsorbs NO/NO 2. • NO x enhances Hg0 adsorption on zigzag surface through the Eley-Rideal mechanism. • The adsorption of Hg0 involves electron transfer and the formation of ionic bonds. • In the presence of NO 2 , mercury primarily adsorbs onto carbon as Hg-O species. The simplification of surface chemical reactions is crucial for comprehending the role of nitrogen oxides (NO x) in the adsorption behavior of elemental mercury (Hg0) onto carbon-based sorbents, thereby contributing to technological advancements in reducing mercury emissions. In this study, we developed two fundamental models for activated carbon and investigated the interactions among the carbon surface, NO/NO 2 , and Hg0 using density functional theory (DFT) calculations. Additionally, thermally-treated activated carbon (TAC) was utilized for Hg0 adsorption, and X-ray absorption fine structure (XAFS) analysis was conducted to examine the morphology and bonding environment of captured Hg. The results suggest that the carbon surface exhibits weak physisorption towards Hg0, but effectively adsorbs NO/NO 2. Adsorption of NO/NO 2 on the carbon surface with a zigzag edge leads to a decrease in the ADCH charge and surrounding electrostatic potential (ESP) of neighboring carbon vertices, thereby enhancing Hg0 adsorption in those regions through the Eley-Rideal reaction mechanism. The interaction between Hg0 and the surface with ZNO1, ZNO2, or ZNOO2 configurations involves electron transfer and subsequent formation of Hg-C ionic bonds, resulting in adsorption energies ranging from −91.33 to −87.56 kJ/mol. Notably, the adsorption of Hg0 onto the surface with ZNOO1 configuration results in a more extensive electron transfer, facilitating the formation of a robust Hg-O ionic bond and leading to a further reduction in Hg0 adsorption energy to −430.02 kJ/mol. XAFS analysis confirms that predominant formation of Hg-O species occurs following Hg0 adsorption on TAC under syngas containing NO 2. [ABSTRACT FROM AUTHOR]

• A system combining thermal desalination and water-lithium bromide absorption cycle. • Three operating modes—water, water-cooling and water-heating—for different seasons. • Greatly improved energy and exergy utilization. • Great operational flexibility in water, cooling and heating production. Water-refrigeration cogeneration systems combining thermal desalination and absorption cycle have been identified as an effective and promising way of utilizing low-grade heat. To take full advantage of the synergy that can be achieved by the combination and overcome the disadvantages of the existing systems, this study proposes and analyzes a multi-function system composed of a single-effect water-lithium bromide absorption heat pump, a single-effect water-lithium bromide absorption refrigeration heat pump and a low-temperature multi-effect evaporation desalination unit. Consuming mainly low-grade heat, the system can operate in at least three modes: water-refrigeration mode for summer, water-only mode for spring/autumn and water-heating mode for winter, thus capable of meeting the requirements of different seasons. The mathematical model is presented and validated, and thermodynamic performance is studied. The results show that all the modes have good energy/exergy performance, as demonstrated in a case study where the energy- and exergy-based coefficients of performance of the absorption unit are 1.60 and 0.62, 1.75 and 0.87, and 1.75 and 1.01 for the three modes, respectively, and the energy saving rates are all as high as 42.7% compared with conventional systems. The proposed system also features great operational flexibility. In water-refrigeration mode, the refrigeration load rate can be regulated from 20% to 100% for a water load rate within 55.2%–110%. In water-heating mode, the heating load rate can be regulated between 0 and a top limit allowed which reaches 256% under a water load rate of 50%, peaks at 459% under 90% and decreases to 358% under 110%. Therefore, the system has good internal synergy, reflected in the whole-year multi-purpose operation, efficient energy utilization, and great operational flexibility. [ABSTRACT FROM AUTHOR]

Large quantities of unstable or even intermittent low-grade heat are released from industrial processes, and a large proportion of them remain unused or used inefficiently. This paper is a proposal and analysis of an energy-efficient and economically feasible way of utilizing the heat to produce fresh water through thermal desalination (TD). An absorption-based thermal energy storage (ATES) unit is introduced to mitigate the mismatch between the unstable heat supply and the relatively stable need of TD. After illustrating the integration logic, a combined ATES and TD system is proposed, and the system configuration and operating modes are introduced. To illustrate the application and the energetic and economic performance of the system, a case study is carried out, where the 100 °C saturated steam intermittently available 7.5 h a day from an industrial process is used as the driving heat source. The results show that the system is energy-efficient, demonstrated by the high coefficient of performance, 1.7, of the ATES subsystem. Being able to run in different modes, the system is applicable to various unstable heat sources. As the first attempt to integrate the ATES into desalination, this study provides a new and effective way of utilizing unstable low-grade heat. [Display omitted] • A combined absorption-based energy storage and thermal desalination system is proposed. • The integration logic, system configuration, operating modes, and case study are presented. • The system is applicable to various unstable low-grade heat sources. • The system is revealed to be energy-efficient and economically feasible. [ABSTRACT FROM AUTHOR]

Large quantities of unstable or even intermittent low-grade heat are released from industrial processes, and a large proportion of them remain unused or used inefficiently. This paper is a proposal and analysis of an energy-efficient and economically feasible way of utilizing the heat to produce fresh water through thermal desalination (TD). An absorption-based thermal energy storage (ATES) unit is introduced to mitigate the mismatch between the unstable heat supply and the relatively stable need of TD. After illustrating the integration logic, a combined ATES and TD system is proposed, and the system configuration and operating modes are introduced. To illustrate the application and the energetic and economic performance of the system, a case study is carried out, where the 100 °C saturated steam intermittently available 7.5 h a day from an industrial process is used as the driving heat source. The results show that the system is energy-efficient, demonstrated by the high coefficient of performance, 1.7, of the ATES subsystem. Being able to run in different modes, the system is applicable to various unstable heat sources. As the first attempt to integrate the ATES into desalination, this study provides a new and effective way of utilizing unstable low-grade heat. [Display omitted] • A combined absorption-based energy storage and thermal desalination system is proposed. • The integration logic, system configuration, operating modes, and case study are presented. • The system is applicable to various unstable low-grade heat sources. • The system is revealed to be energy-efficient and economically feasible. [ABSTRACT FROM AUTHOR]

A graphical method is developed for evaluating the thermodynamic feasibility of combined absorption vapor compression (AVC) and low-temperature multi-effect evaporation (LT-MEE) desalination systems. The method is based on the diagram showing the relationship among the vapor pressure, temperature and concentration of absorbent solution and seawater. Three commonly used absorbent solutions—LiBr-H 2 O, LiCl-H 2 O and CaCl 2 -H 2 O, are taken as examples. A five-step procedure is proposed and three systems—a conventional water-only system, a water-refrigeration cogeneration system and an intermediate vapor absorption water-only system, are analyzed for illustration purpose. Requiring only a small amount of information, the method is suitable to be used in the preliminary planning or design phase of an AVC-MEE system. Besides, the method can also give the values or ranges of several important parameters for the AVC-MEE systems being evaluated to be feasible, thus providing useful information for further investigation. • A graphical method for evaluating the thermodynamic feasibility of AVC-MEE systems is proposed. • The method is based on the vapor pressure diagram of absorbent solution and seawater. • The method is revealed to be effective and easy to apply. • The method can provide useful information for further investigation. [ABSTRACT FROM AUTHOR]