Thermal Electric System Research Articles

Cryogenic Liquid Rocket and Nuclear Thermal Rocket: A Survey of the Current Technology and a Comparison for Future Mars Missions

The innovation of reusable rockets holds the potential to revolutionize both Mars scientific exploration and commercial tourism. Thus, this paper aims to indicate the most promising propulsion system for the Mars mission. While SpaceX proposed the cryogenic liquid rocket Starship to achieve Mars colonization by 2050, the viable nuclear thermal propulsion has been outlined by rocketry experts for space travel. This paper surveys the current state-of-the-art of both popular propulsion systems, indicating their advantages and disadvantages. Methods to increase the delivery and cost efficiency are also offered, including on-orbit refueling for cryogenic liquid rockets and various nuclear core variants for nuclear thermal rockets. Subsequently, their comparative analysis is delivered in the discussion, focusing on their transportation efficiency and cost efficiency for future mass missions. With faster travel, greater payload, and reduced propellant consumption, nuclear thermal propulsion has shown to be a brighter prospect and potential than cryogenic liquid rocket. Nevertheless, the author believes a new class of bimodal nuclear thermal electric propulsion system is the most promising option, combining the merits and complementing drawbacks of cryogenic liquid propulsion, nuclear thermal propulsion, and nuclear electric propulsion.

Analytic investigations of snow melting efficiency and temperature field of thermal conductive asphalt concrete combined with electrical-thermal system

Electrical-thermal technique is a promising method for asphalt pavement snow melting with minimal external intervention. To employ this technology in practical engineering applications, plenty researches have focused on the electrical-thermal system configuration and design. In this study, an effective method to improve the efficiency of melting by combination of thermal conductive asphalt concrete (TCAC) and electrical-thermal system was proposed. The TCAC is designed with steel slag as the thermal conductive filler and used in the upper layer of the pavement to improve the heat transfer efficiency of the electrical-thermal system. The thermal conductivity (λ), road performance and electrical-thermal snow melting performance were studied in the laboratory. It is demonstrated that the mean λ of TCAC reaches a peak value when the steel slag (3–5 mm) volume content is 60 %, and it increased by 8.23%. The road performance parameters of TCAC, such as dynamic stability, flexural tensile strength, water stability and expansion ratio, can all meet the specification requirements. The snow melting effect of TCAC is better than that of ordinary asphalt concrete (OAC), and the heating rate and the snow melting efficiency of the thermal conductivity slab are increased by 25–50 % and 25–38 %, respectively. In addition, the test road was constructed based on the laboratory results, the temperature field and surface temperature prediction in the practical engineering are further analyzed. Results show that the temperature distribution of the test road is relatively uniform and the surface temperature is 0.8–1.5 °C higher than that of the ordinary section. The surface temperature of test road can be predicted and evaluated well by the Back Propagation (BP) neural network, 87 % of error is within 1 °C, and the fitting coefficient is 0.9325.

Sensitivity analysis and practical application of an automatic snow-melting membrane roof

In recent decades, numerous membrane structures have been built in the cold regions of China. Nevertheless, uneven snow distribution and snow sliding from the edge of roofs cause frequent collapsing, which threatens people's lives and properties. To prevent the collapsing of membrane structures, we present an automatic snow-melting membrane roof based on an electrical–thermal system (ASMR-ETS) in this paper. ASMR-ETS is environmentally friendly, clean, and can be used for eliminating snow that accumulates on membrane roofs. The most important task in designing ASMR-ETS is the determination of its feasibility. A thermal simulation method for the snow-melting process is described in this paper. The surface temperature was obtained using the commercial software ABAQUS. The applicability and rationality of the thermal simulation were verified via snow-melting experiments. The heating wire spacing and heating wire power were set as heating wire parameters. The wind velocity, solar irradiation, ambient temperature, and snow thickness were selected to be the climatic conditions. The surface temperature of ASMR-ETS was simulated, and the snow-melting performance (snow-free area ratio and coefficient of variation of temperature) was analyzed for different heating wire parameters and climatic conditions. According to the simulation results, increasing the wind velocity and snow thickness decreases the snow-free area ratio and improves the coefficient of variation of temperature, whereas solar irradiation and ambient temperature showed an opposite effect. Furthermore, the snow-melting performance of the membrane structure was studied, and different layout schemes of the heating wire were considered. The results show that ASMR-ETS is practical and can therefore be used to clear snow on membrane structures.

A comprehensive model and its optimal dispatch of an integrated electrical-thermal system with multiple heat sources

As essential parts of the combined heat supply network with multiple heat sources, the electrical-heating and heat storage technology can simultaneously achieve the goal of clean heating and renewable energy accommodation. The paper introduces the integrated electrical-thermal system with multiple heat sources that consist of combined heat and power (CHP), coal-fired boiler (CB), and electrical boiler (EB) with thermal energy storage (TES). Considering the integration of electrical and thermal networks, we construct a comprehensive model that includes the electrical energy transmission and the overall heat transfer and storage processes based on the heat current method. Based on the comprehensive model, the optimal dispatch of the integrated system is discussed, and an iteration solving method is proposed, which can achieve acceptable convergence and solving efficiency. The simulation results show the combined operation of multiple heat sources has higher system operation efficiency but not necessarily a higher utilization rate of renewable energy. In the test system the combined operation of CHP and coal-fired boiler can reduce the coal consumption of the system by 2%. However, the wind utilization of the system decreases by 4.17%. Moreover, the introduction of an electrical boiler with a TES device can improve the system's flexibility and reduce wind curtailment, wherein the test system is 12.11% more wind consumption. Further, the heat load level can affect the operation efficiency of CHP, the combined operation of multiple heat sources can achieve the balance between reducing coal consumption and increasing renewable energy power generation.

Multiscale Modeling and Experimental Characterization for Enhancement in Electrical, Mechanical, and Thermal Performances of Lithium-Ion Battery

Lithium-ion batteries are the thriving energy storage device in multiple fields, including automobiles, smart energy grids, and telecommunication. Due to its high complexity in the electrochemical–electrical–thermal system, there are certain non-linear spatiotemporal scales for measuring the performance of lithium-ion batteries. The fusion of experimental and modeling approaches was used in this study to enhance the performance of lithium-ion batteries. This article helps to evaluate the properties of the LiMn2O4 cathode material for Li-ion batteries and also characterize the crystalline nature, morphological structure, and ionic and electronic conductivity of the electrode material using an experimental approach. In addition, a new computational model was designed and formulated to support various other models for computational investigation. This simulation was designed to analyze the one-dimensional structure of coin cell batteries and to evaluate electrochemical and thermal performances. All computational performances have been validated with the help of experimental techniques and also provide multiple benchmarks for future integration of experimental and computational approaches.

Atomic-Scale Observation of Unusual Dislocations in GaAs-GaAsSb Heterostructured Nanowires.

Cognizing the structural characteristics of a heterointerface is significant to understand the growth mechanism of heterostructured nanowires. Here, the structural characteristics of a heterointerface in GaAs-GaAsSb heterostructured nanowires were investigated by employing spherical aberration (CS)-corrected transmission electron microscopy (TEM). It is found that some unusual dislocations are formed at the heterointerface, leading to the bending of nanowires. Further, the atomically inhomogeneous distribution of Sb content near the heterointerface is revealed, which is responsible for the formation of dislocations. By applying a thermal electric system equipped in the Cs-corrected TEM, a direct observation of structural evolution at the heterointerface was enabled and the stability of GaAs-GaAsSb heterostructured nanowires was evaluated. In situ high-resolution TEM imaging indicates that the destabilization of the heterointerface occurs during nanowire annealing. This study builds a direct correlation between the nanowire heterointerfacial structure with nanowire growth behavior and its stability, which is of importance for heterostructured nanowire design for practical use.

A hybrid robust-stochastic approach for unit commitment scheduling in integrated thermal electrical systems considering high penetration of solar power

With increasing environmental concerns, limited oil reserves and governmental incentives, installation of photovoltaic (PV) systems have gained substantial momentum in smart electric distribution systems (EDS), which is considered to be a great success. That said, widespread integration of these PV units, comes with uncertainty issues that puts the flexibility of the system at stake. In this regard, local district heating systems (DHS) are considered to be an effective tool in enhancing the flexibility of the power system on account of their high thermal inertia. In this study, we propose hybrid robust (RO)- stochastic programming (SP) optimization framework for commitment scheduling of distributed generation units and local DHS considering high penetration of PV units. Furthermore, the impact of flexible thermal and electrical loads on total operational cost and overall flexibility of the system is evaluated. The SP is utilized to deal obscurity of solar radiation, and RO is utilized to handle price uncertainties. The uncertainty management via the electrical storage system is also scrutinized. The results are evaluated by different cases studies implemented on an integrated IEEE 33-bus EDS and an 8-node DHS. Eventually, the mixed integer linear problem is solved with a standard CPLEX solver.

A Study on the Characteristics of the Concentrated Solar Photovoltaic/thermal Integrated System

This paper mainly introduces a comprehensive solar energy utilization system with low-CPC and polycrystalline silicon solar photovoltaic components. Outdoor experiments have been made to test the electrical efficiency, heat efficiency and their changes of the system with fixed temperature of outlet water and different sunshine conditions. Besides, this paper also compares the effects of outlet water at various temperatures on the efficiency of the whole system as well as the temperatures and flow rate responses with different PID parameters. Through analysis of these experimental data, the most desirable temperature of outlet water and PID parameters have been obtained in CPC-PV/T Hybrid Thermal-electric System, thus providing references for relevant experimental research.

Optimization design and prediction of the snow-melting pavement based on electrical-thermal system

Electrically heated roads are used as a substitute for chemicals and mechanical devices to ensure mobility and traffic safety in winter weather. This paper aims to design an electrical-thermal system and recommends the best system parameters based on the melting efficiency, energy costs and mechanical durability of the pavement. In addition, the snow melting effect was verified experimentally according to the recommended parameters and the accuracy of the electrical-thermal system was predicted and evaluated by back-propagation neural network. Experiment results indicate that the 24 K Teflon‑carbon fiber heating wire is suitable for the road heating system. It can provide a stable heat source and has the characteristics of high temperature/pressure resistance during the asphalt mixture molding and rolling process. The system parameters were recommended based on snow melting efficiency and mechanical durability of the pavement such as temperature stress and temperature uniformity. The optimal heating wire spacing is 10 cm, set heating wire depth as 4 cm, besides, the heating wire power can be determined based on energy consumption, and actual environmental conditions. The recommended parameters were used for snow melting laboratory experiments to verify the validity of the electrical-thermal system. Finally, the temperature trend of this system can be predicted and evaluated well with high accuracy by the back-propagation neural network. The research enriches the theory of thermodynamic structural design for snow melting pavement systems.

Performance evaluation of a hybrid alkali metal thermal electric converter-two stage thermoelectric generator system

• A two-stage thermoelectric generator is proposed to recover waste heat from AMTEC. • Feasibility and effectiveness of TTEG as bottoming cycle are justified. • Power density, energetic and exergetic efficiency gain obvious improvements. • Effects of some key parameters on the system performance are revealed. A great part of high-quality heat is wasted, which significantly lowers the performance of alkali metal thermal electric converters. To achieve gradual and efficient utilization of the waste heat, a new cogeneration system model composed of an alkali metal thermal electric converter and a two-stage thermoelectric generator is established, in which the high-quality waste heat of alkali metal thermal electric converter is further reused by two-stage thermoelectric generator for additional power generation. Based on the theories of electrochemistry and non-equilibrium thermodynamics, mathematical expressions of power outputs and efficiencies of alkali metal thermal electric converter, two-stage thermoelectric generator and hybrid system are derived by taking the main irreversible losses into account. Calculations show that the maximum attainable power output density and its efficiency of hybrid system are, respectively, 5152.7 W/m 2 and 30.0%, which are approximately 54.1% and 27.7% greater than that of the sole alkali metal thermal electric converter system in previous studies. Two-stage thermoelectric generators are efficient to utilize the waste heat from alkali metal thermal electric converters. Comprehensive parametric studies show that operating conditions and designing parameters can be tuned to optimize the hybrid system performance. The results may offer some theoretical guidance for designing and running such a hybrid system.

Study on thermal properties of steel slag asphalt concrete for snow-melting pavement

The utilization of steel slag in asphalt concrete can improve the thermal conductivity of steel slag asphalt concrete. The thermal conductivity of asphalt concrete largely affects the surface temperature distribution of asphalt pavement, which in turn affects the mechanical characteristics of asphalt pavement and the temperature of the environment near the surface pavement. In this study, the thermal properties of asphalt concrete with different steel slag volume contents were investigated in a laboratory. The thermal conductivity was tested using a parallel hot-wire and transient plane source method, and the uniformity and surface temperature were studied through infrared thermal imaging. Next, a 3D infrared image was analyzed based on regional statistics, image binarization, and the coefficient of variation evaluation. The practical snow melting efficiency of thermally conductive asphalt concrete was evaluated using an electrical-thermal system. Experimental results indicate that the thermal conductivity, heating distribution uniformity, and surface temperature of asphalt concrete are first increased, before decreasing with an increase in the steel slag replacement. Regardless, the thermal properties of steel slag asphalt concrete were shown to be better than those of conventional asphalt concrete. The most effective steel slag volume in asphalt concrete was shown to be 60 vol %. The snow melting efficiency of thermal conductivity asphalt concrete can be improved using an electrical-thermal system. The results of this study will help mitigate a shortage of natural resources and improve the temperature distribution of pavements.

A Research on Various Solar Thermal Power Technologies

Solar thermal electric systems are simplest and hold promise of viability. Solar thermal systems have great similitude with conventional power system. In this paper we present an overview of various solar thermal power technologies to evolve criteria for selection of best systems.

Exergy optimal multi-physics aircraft microgrid control architecture

The more electric aircraft (MEA) concept aims to reduce emissions, fuel costs, and enable incorporation of electric weapon systems and advanced sensor platforms. These systems will further burden the electrical system due to the pulse like loading and require advanced control strategies and distributed energy storage systems to ensure stability. Furthermore, multi-physical coupling of thermal electrical systems are often compartmentalize and analyzed separately, forgoing congruency that could occur if analyzed together. Here, we study how exergy, the amount of useful energy throughout a system, can guide control design and system operation. A multi-physics networked microgrid model was developed of an aircraft with two generation sources, interconnecting power converters, a lumped thermal mass model and pulsed loading. The Hamiltonian Surface Shaping Power Flow Control (HSSPFC) strategy is applied to the electrical grid via idealized and distributed storage elements. The HSSPFC was first developed to solve a general, scalable, form a networked microgrid architecture and then applied to the specific aircraft model. Implementation of the HSSPFC requires an outer loop to balance installed generation and to manage storage. This was accomplished through an exergy optimal set point generation scheme that minimized exergy destruction in the power converters. Bus regulation of within 3% of the desired set point was achieved while servicing a 100 kW pulsed load. A tradeoff between optimization update rate and storage regulation was found to be limited by the algorithm execution speed. Increased optimization update rates were linked to reduced storage use and fewer transients in bus voltage. The thermal model was electrically coupled through pumping loads and by cooling the power electronics. Exergy optimal coolant pump operation was also studied. The minimal exergy and pump energy consumption were obtained by operating the coolant system near the upper temperature limit of the coolant, which minimized cooling electrical loads.

Selection of biomass supply for a gasification process in a solar thermal hybrid plant for the production of electricity

The great potential for bioenergy in Spain is undeniable given our country´s enormous biomass supply. This fact contrasts with the limited evolution in the biomass sector for thermal and electricity generation over recent years. In this paper, we consider the utilization of fluidized bed gasification (FBG) as a biomass utilization technology incorporated into a thermal electric system to improve power plant production both thermally and electrically. Firstly, we studied the biomass resources available within a 100 km radius of the plant’s location in Almería province (Spain). This biomass included almond shells, olive tree prunings, holm oak prunings and vegetable residues from greenhouse tomato and pepper plants. Technical criteria were applied to determine the most appropriate biomass to use in the gasification process; this included the physical-chemical characterization, the cost and the logistic-agronomic profile. The physical-chemical characterization included humidity, ash, calorific value, an elemental analysis, sulfur and chlorine, etc. On the basis of this characterization, almond shells were found to be the optimal biomass (Mar = 12.9%, Ar = 1.1%, Vd = 82.2%, Qp,net,d =18,470 kJ/kg and Cl = 60 mg/kg), and depending on certain parameters, could be classified as A1 or A2. Both the olive tree prunings (Mar = 6.2%, Ar = 5.5%, Vd = 83.4%, Qp,net,d =18,193 kJ/kg and Cl =15 mg/kg) and the holm oak prunings (Mar = 9.2%, Ar = 4.1%, Vd = 80.3%, Qp,net,d =16,335 kJ/kg and Cl =12 mg/kg) were also considered to be good biomass resources, and were given an A2 or B1 classification. However, greenhouse vegetable residues (tomato and pepper) did not have suitable technical parameters (Mar = 82.6-29.6%, Ar = 35.5-6.4%, Vd = 75.1-59.1%, Qp,net,d = 17277-11529 kJ/kg and Cl = 1196-751 mg/kg) for use in the gasification process. Concerning the economic criteria, the best cost per kilogram (0.01€/kg) was found for the greenhouse vegetable residues, followed by the olive tree prunings (0.04€/kg); the highest cost corresponded to almond shells (0.07€/kg). With regard to the logistic-agronomic criteria, the theoretical hours of production in the power station are determined by the total availability of the resource in the particular location. The results indicate that the amount of almond shells available in the area was not sufficient (3854 h) to ensure the operation of the power station at full load (8760 h) but it would be possible in conjunction with other biomass types. The final decision regarding the optimal biomass to use was made on the basis of a multivariable analysis using the Visual Preference Ranking Organization Methods for Enrichment Evaluations (PROMETHEE) tool. From this analysis, olive tree prunings were selected as the optimum biomass to use because of their extensive local availability (58,080 t/year), in addition to them having suitable physical-chemical characteristics (Mar = 6.2%, Ar = 5.5%, Vd = 83.4%, Qp,net,d =18,193 kJ/kg and Cl =15 mg/kg)) and a reasonable cost (0.07€/kg).

Ultrafast and efficient photothermal conversion for sunlight-driven thermal-electric system

Thermoelectric battery is effective in converting thermoelectricity based on Seebeck effect. As an all-solid-state energy conversion model, this battery is highly significant in improving the utilization of solar energy using a clean and noiseless process. However, efficient photothermal conversion and temperature difference control are the key challenges in enhancing solar-thermal-electric conversion. Herein, we constructed a novel sunlight-driven thermoelectric system with temperature difference control characteristic. In which the light-driven phase change heat storage material (PCHSM) was used as the hot side, and the phase change cool storage material (PCCSM) as the cold side. Ultrafast photothermal conversion of the PCHSM was achieved through the nonradiative decay of the excited state, which was revealed by means of femtosecond transient absorption technique. Solar radiation was efficiently utilized as shown by the excellent visible light absorption, ultrafast photothermal transformation, and phase change heat storage characteristics of the PCHSM. The PCCSM with high phase change cool storage performance could provide enough cold energy to maintain the cold-side temperature. Temperature gradient was controlled using the cold-side and hot-side materials based on the phase-change temperature control characteristics.

Solving a Classical Optimization ProblemUsing GAMS Optimizer Package: Economic Dispatch ProblemImplementation

This paper presents an effectiveness strategy to model and solve nonlinearmathematical optimization problems in electrical engineering using Gene-ral Algebraic Modeling System (GAMS) for undergraduate students. Aclassical problem known as economic dispatch has been selected to showthe need of using mathematical tools to solve a large scale optimizationproblem related with engineering. The economic dispatch is a classical op-timization problem in operation of thermal electric systems, being the mainidea to find an economical operation for thermal generators. This opera-tion is based on a quadratic cost curve with some operating constraints,i.e., power balance and generation capacities. A numerical simulation isimplemented using GAMS optimization package in demo version. Thisresearch has been developed with the support of 36 students of the courseof Regulation and Operation of Electrical Systems (ROES) in the programof Electrical Engineering at Universidad Tecnológica de Pereira (UTP).

Validation, Optimization and Simulation of a Solar Thermoelectric Generator Model

This study explores thermoelectrics as a viable option for small-scale solar thermal applications. Thermoelectric technology is based on the Seebeck effect, which states that a voltage is induced when a temperature gradient is applied to the junctions of two differing materials. This research proposes to analyze, validate, simulate, and optimize a prototype solar thermoelectric generator (STEG) model in order to increase efficiency. The intent is to further develop STEGs as a viable and productive energy source that limits pollution and reduces the cost of energy production. An empirical study (Kraemer et al. in Nat Mater 10:532, 2011) on the solar thermoelectric generator reported a high efficiency performance of 4.6%. The system had a vacuum glass enclosure, a flat panel (absorber), thermoelectric generator and water circulation for the cold side. The theoretical and numerical approach of this current study validated the experimental results from Kraemer’s study to a high degree. The numerical simulation process utilizes a two-stage approach in ANSYS software for Fluent and Thermal-Electric Systems. The solar load model technique uses solar radiation under AM 1.5G conditions in Fluent. This analytical model applies Dr. Ho Sung Lee’s theory of optimal design to improve the performance of the STEG system by using dimensionless parameters. Applying this theory, using two cover glasses and radiation shields, the STEG model can achieve a highest efficiency of 7%.

Observation and Characterization of the Thermoelectric Power Generation

Authors report methodical studies on some novel, alternative energy technologies, and produced results of a thermoelectric power generation (TEPG) system. For the sake of evaluating critical thermoelectric (TE) features, they have invented the state-of-the-art equipment that has important specification capability. The studies cover the efficiency and many aspects of TEPG features as follows. A thermoelectric module is measured in situ that includes TE efficiency, force response curve, current-voltage (I-V) and power-voltage (P-V) characterization, and power temperature (P-T) response curve. They have improved both the higher total output power and the more efficient TEPG efficiency than their comparison TE devices and systems in their studies. In addition, authors will present a series of design, construction, and characterization of a thermal electric generation system which aims to achieve a large power output and high efficiency for the energy harvesting application. Furthermore, their studies lead to important knowledge of TEPG systems in terms of multi-stack modules and of the optimization in TEPG applications. Finally, the prototypes are built for both the tabletop and other applications with new findings. Several sets of prototype TEPG are developed for experimental investigation and data analysis, followed by the summary and conclusions based on the data.

Solar Hybrid Heating & Cooling Systems on District Level – The Austrian Project CiQuSo

The Austrian research project City quarters with optimised solar hybrid heating and cooling systems-. (CiQuSo) aims to develop, evaluate and optimize concepts for solar energy systems to provide energy for buildings and cities. The comparison and alignment of the energy demand (heating, cooling, domestic hot water, electricity) with the production in terms of dynamic behavior and spatial distribution enables the optimization of the energy performance of a district or a small city. Based on solar thermal and solar electrical systems highly innovative solar hybrid concepts (based on the assumption of possible energy exchange between certain or all buildings in the district) will be developed and will be applied in Heating, Ventilation and Air Conditioning- (HVAC) systems for buildings. The applications will be evaluated on city district level in order to identify further optimization potentials gained by the intra-building energy exchange as well as load shifting strategies. The applicability of the developed methods and concepts will be tested in Itzling, a district in the city of Salzburg, Austria.This paper presents the planned methodology to optimize the use of solar energy on a district level and will reports on first achievements of the project activities.

Integrated Electrical and Thermal Grid Facility - Testing of Future Microgrid Technologies

This paper describes the Experimental Power Grid Centre (EPGC) microgrid test facility, which was developed to enable research, development and testing for a wide range of distributed generation and microgrid technologies. The EPGC microgrid facility comprises a integrated electrical and thermal grid with a flexible and configurable architecture, and includes various distributed energy resources and emulators, such as generators, renewable, energy storage technologies and programmable load banks. The integrated thermal grid provides an opportunity to harness waste heat produced by the generators for combined heat, power and cooling applications, and support research in optimization of combined electrical-thermal systems. Several case studies are presented to demonstrate the testing of different control and operation strategies for storage systems in grid-connected and islanded microgrids. One of the case studies also demonstrates an integrated thermal grid to convert waste heat to useful energy, which thus far resulted in a higher combined energy efficiency. Experiment results confirm that the facility enables testing and evaluation of grid technologies and practical problems that may not be apparent in a computer simulated environment.