scholarly journals Discrepancy between Constant Properties Model and Temperature-Dependent Material Properties for Performance Estimation of Thermoelectric Generators

Entropy ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1128
Author(s):  
Prasanna Ponnusamy ◽  
Johannes de Boor ◽  
Eckhard Müller
Keyword(s):  
Material Properties ◽  
Heat Balance ◽  
Internal Heat ◽  
Electrical Energy ◽  
Joule Heat ◽  
Performance Estimation ◽  
Maximum Efficiency ◽  
Asymmetric Distribution ◽  
Heat Distribution ◽  
Entropy Flow

The efficiency of a thermoelectric (TE) generator for the conversion of thermal energy into electrical energy can be easily but roughly estimated using a constant properties model (CPM) developed by Ioffe. However, material properties are, in general, temperature (T)-dependent and the CPM yields meaningful estimates only if physically appropriate averages, i.e., spatial averages for thermal and electrical resistivities and the temperature average (TAv) for the Seebeck coefficient (α), are used. Even though the use of αTAv compensates for the absence of Thomson heat in the CPM in the overall heat balance, we find that the CPM still overestimates performance (e.g., by up to 6% for PbTe) for many materials. The deviation originates from an asymmetric distribution of internally released Joule heat to either side of the TE leg and the distribution of internally released Thomson heat between the hot and cold side. The Thomson heat distribution differs from a complete compensation of the corresponding Peltier heat balance in the CPM. Both effects are estimated quantitatively here, showing that both may reach the same order of magnitude, but which one dominates varies from case to case, depending on the specific temperature characteristics of the thermoelectric properties. The role of the Thomson heat distribution is illustrated by a discussion of the transport entropy flow based on the α(T) plot. The changes in the lateral distribution of the internal heat lead to a difference in the heat input, the optimum current and thus of the efficiency of the CPM compared to the real case, while the estimate of generated power at maximum efficiency remains less affected as it is bound to the deviation of the optimum current, which is mostly <1%. This deviation can be corrected to a large extent by estimating the lateral Thomson heat distribution and the asymmetry of the Joule heat distribution. A simple guiding rule for the former is found.

scholarly journals Smart energy monitoring based on IoT Lora-Wan on the campus buildings: Case study Indonesian Defence University (Unhan), Sentul, Bogor

2021 ◽  
Vol 878 (1) ◽  
pp. 012065
Author(s):  
S Ramadhan ◽  
L Lisapaly ◽  
D Boesrony
Keyword(s):  
Interconnection Networks ◽  
Electrical Energy ◽  
Physical Structure ◽  
Maximum Efficiency ◽  
Smart Devices ◽  
Energy Usage ◽  
Smart Building ◽  
Energy Meter ◽  
Campus Building

Abstract Smart building constructions such as Campus Buildings have been designed for use, where the physical structure and system components are interrelated and can maximize functionality for operation and maintenance. So that the Campus building can be used with a longer age. One of the sub-systems that can monitor and notify the range of energy usage on a campus building is a smart electrical energy meter (kWh meter), which is connected to all devices that consume electrical energy in campus buildings. These interconnected smart devices use IoT (Internet of Things) interconnection networks and low power wireless technology (Lora). In a case study of the use of this system at the Indonesian Defense University, Unhan, Sentul, Bogor, West Java, it can be seen how the maximum efficiency in the use of electrical energy can be obtained in the smart campus building construction, which runs automatically.

Performance Improvement of a Combined Power and Cooling Cycle for Low Temperature Heat Sources Using Internal Heat Recovery and Scroll Expander

2019 ◽  
Author(s):  
Martina Leveni ◽  
Arun Kumar Narasimhan ◽  
Eydhah Almatrafi ◽  
D. Yogi Goswami
Keyword(s):  
Low Temperature ◽  
Heat Recovery ◽  
Pressure Ratio ◽  
Internal Heat ◽  
Operating Conditions ◽  
Maximum Efficiency ◽  
Water Mixture ◽  
Heat Sources ◽  
Scroll Expander ◽  
Temperature Heat

Abstract Low temperature heat sources inherently result in lower cycle efficiencies, which can be improved by means of combined power and cooling generation. In order to produce power and cooling, appropriate thermodynamic cycles and working fluids must be used. Goswami cycle is a combined cycle that produces power and refrigeration by using ammonia-water mixture for low temperature heat sources. In the present study, a scroll expander is modeled specifically for the cycle operating conditions and a theoretical investigation is conducted to determine the cycle performance. A scroll expander design suitable for the operating conditions improves the power output and thereby overall thermal efficiency. The scroll expander efficiency varied between 0.05 and 0.61 for the pressure ratio between 2.2 and 8.6, with a maximum efficiency of 0.697 achieved at a pressure ratio of about 4.4. An internal heat recovery from the rectifier is proposed along with a flow split in the strong solution and analyzed for overall cycle energy efficiency improvement. Internal heat recovery from the rectifier increased the first law effective efficiency and the effective exergy efficiency by 7.9% and 7.8%, respectively, over the basic configuration.

scholarly journals Conductive Fabric Heaters for Heat-Activated Soft Actuators

Actuators ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 9 ◽  
Author(s):  
Mark Cartolano ◽  
Boxi Xia ◽  
Aslan Miriyev ◽  
Hod Lipson
Keyword(s):  
Phase Change ◽  
Material Properties ◽  
Stress And Strain ◽  
Heat Distribution ◽  
Cyclic Heating ◽  
Linear Strain ◽  
Electrically Conductive ◽  
Thermally Induced ◽  
Soft Actuators ◽  
Fabric Design

We examine electrically conductive fabrics as conductive heaters for heat-activated soft actuators. We have explored various fabric designs optimized for material properties, heat distribution and actuation/de-actuation characteristics of the soft actuators. We implemented this approach in the silicone/ethanol composite actuators, in which ethanol undergoes a thermally-induced phase change, leading to high actuation stress and strain. Various types of conductive fabrics were tested, and we developed a stretchable kirigami-based fabric design. We demonstrate a fabric heater that is capable of cyclic heating of the actuator to the required 80 °C. The fabric with the special kirigami design can withstand temperatures of up to 195 °C, can consume up to 30 W of power, and allows the actuator to reach >30% linear strain. This technology may be used in various systems involving thermally-induced actuation.

Modeling of Segmented Peltier Cooling with Discrete and Continuous Concentration Function

2005 ◽  
Vol 492-493 ◽  
pp. 507-516 ◽  
Author(s):  
S. Walczak ◽  
Winfried Seifert ◽  
Eckhard Müller
Keyword(s):  
Differential Equation ◽  
Seebeck Coefficient ◽  
Temperature Profile ◽  
Material Properties ◽  
Performance Estimation ◽  
Cooling Power ◽  
One Dimensional ◽  
Peltier Cooling ◽  
Cooling Devices ◽  
Te Material

Commercialization of Peltier coolers has progressed during last years and special efforts have been undertaken to enhance the efficiency of thermoelectric (TE) devices. Along with the continued search for advanced TE materials, the concept of FGM offers a strategy of gradual improvement of device performance. In reality a functional gradient in a TE material means a related spatial variation of all TE properties – Seebeck coefficient, electrical, and thermal conductivity – whereas the most relevant effect is linked to the gradient of the Seebeck coefficient. Due to the spatial dependence of the Seebeck coefficient, Peltier heat is absorbed or released inside the TE element under current flow (distributed Peltier effect) which can be exploited to shape the internal temperature profile in a desired manner. Starting from the first principles of thermoelectricity, a differential equation governing the coupling of thermal and electrical transport is derived within the frame of a one-dimensional model. It is shown that this approach can be also used to model multi-segment Peltier cooling devices. Temperature profiles T(x) have been calculated for a segmented TE element within the framework of a constant parameters theory. The work presents an analytical model for performance evaluation of multiply-segmented Peltier elements. The problem is treated in a one-dimensional approach for a p-type stack containing N segments of different properties. Assuming constant TE material properties in each of the segments, the differential equation of TE transports has been solved to obtain the temperature profile T(x) in each segment. With the material properties values in each segment representing volume average values this model gives an excellent approximation also for continuously graded elements. The boundary conditions of the TE problem set-up, as conservation of heat at any intermediate junction between the segments, and fixed temperature at the cold and hot end of the element, lead to a linear equation system, which can be easily solved by means of standard methods. From the solution, all desired performance parameters can be deduced. Based on realistic material data exemplary calculations are presented for stacked and continuously graded elements. To demonstrate the developed numerical algorithm, gradients of the Seebeck coefficient are mainly considered. Calculations have been performed for N = 2, 5, 10, and continuous gradients. As target parameters, the C.O.P. and the cooling power have been calculated as functions of the electric current. As well, the minimum temperature of the cold side has been determined for various shape of the Seebeck gradient. It is shown that the TE FGM effect can be almost completely utilized already by a stack of two to five homogeneous segments. The results allow for giving an estimation on the order of magnitude of performance improvement of both discontinuously and continuously graded Peltier cooling devices. The model calculation was implemented with the software tool MATHEMATICA. The code provides an easy to handle convenient instrument for performance estimation of non-homogeneous Peltier pellets. Technological studies for controlled fabrication of those pellets are underway.

Experimental Study of the Effect of Cryogenic Treatment on the Performance of Electro Discharge Machining

2009 ◽  
Author(s):  
Murali Meenakshi Sundaram ◽  
Yakup Yildiz ◽  
K. P. Rajurkar
Keyword(s):  
Material Properties ◽  
Removal Rate ◽  
Cryogenic Treatment ◽  
Cold Treatment ◽  
Electrical Energy ◽  
Machining Process ◽  
Deep Cryogenic Treatment ◽  
Electrically Conductive ◽  
Conductive Materials ◽  
Electro Discharge Machining

Cryogenic treatment is a heat treatment process in which the specimen is subjected to an extremely low temperature of the order of −300° F and below, to cause beneficial changes in the material properties. The advantages of cryogenic treatment include relieved residual stresses, and better electrical properties. Electro discharge machining (EDM) is a well known nontraditional machining process in which electrical energy is converted to thermal energy to remove material by melting and evaporation from electrically conductive materials. The process performance of EDM is affected by several factors including the material properties. In this study, the effect of cryogenic treatment on the performance of EDM is investigated experimentally. Copper tool electrodes were subjected to two different treatment methods, namely cold treatment (around −150° F) and deep cryogenic treatment (around −300° F). Using these electrodes, experiments were conducted to study the effect of various process parameters. Significant improvement in material removal rate was observed for EDM with cryogenically treated tools. However, their effect on tool wear is only marginal.

Effects of Various Types of Binary Cycles on Thermal and Exergy Efficiency of Combined Flash-Binary Power Plants

2012 ◽  
Author(s):  
Mahshid Vatani ◽  
Masoud Ziabasharhagh ◽  
Shayan Amiri
Keyword(s):  
Power Plants ◽  
Organic Rankine Cycle ◽  
Internal Heat ◽  
Rankine Cycle ◽  
Exergy Efficiency ◽  
Maximum Efficiency ◽  
Working Fluid ◽  
Internal Heat Exchanger ◽  
Different Types ◽  
Geothermal Power

With the progress of technologies, engineers try to evaluate new and applicable ways to get high possible amount of energy from renewable resources, especially in geothermal power plants. One of the newest techniques is combining different types of geothermal cycles to decrease wastage of the energy. In the present article, thermodynamic optimization of different flash-binary geothermal power plants is studied to get maximum efficiency. The cycles studied in this paper are single and double flash-binary geothermal power plants of basic Organic Rankine Cycle (ORC), regenerative ORC and ORC with an Internal Heat Exchanger (IHE). The main gain due to using various types of ORC cycles is to determine the best and efficient type of the Rankine cycle for combined flash-binary geothermal power plants. Furthermore, in binary cycles choosing the best and practical working fluid is an important factor. Hence three different types of working fluids have been used to find the best one that gives maximum thermal and exergy efficiency of combined flash-binary geothermal power plants. According to results, the maximum thermal and exergy efficiencies both achieved in ORC with an IHE and the effective working fluid is R123.

Duty Cycle and Transport Phenomenon Analysis of Battery Storage System for Hybrid Locomotive Application

2012 ◽  
Author(s):  
Sarang Subhedar ◽  
Pradip Majumdar ◽  
Rao Kilaparti ◽  
David Schroeder
Keyword(s):  
Diesel Engine ◽  
Simulation Analysis ◽  
Storage System ◽  
Traction Force ◽  
Electrical Energy ◽  
Maximum Efficiency ◽  
Regenerative Braking ◽  
Battery Storage ◽  
Simulation Code ◽  
Excessive Heat

The interest for developing hybrid electric locomotives consisting of diesel engine, regenerative braking and battery storage is growing due to increased demand and cost of diesel oil, uncertainty in the steady supply of oil, and increased standards for reduced emissions. Electrical energy is lost from electric locomotives in the form of heat during dynamic braking. Routing this energy using a regenerative braking system into battery stacks can improve the overall efficiency as it can be used later to provide traction force during acceleration. Objective of this study is to perform a feasibility analysis of modes of regenerating the energy developed in the braking and storing the energy in an electric battery storage system for use in railroad locomotive applications. Various road locomotive duty cycles, charge and discharge rates, and environmental conditions have been considered as this is expected to substantially influence the optimal performance and safety of the battery as well as the potential fuel savings that could be realized using a hybrid design. A computational algorithm is developed to determine the amount of energy that can be obtained from regenerative breaking during the run of locomotive and can be stored back into the stack of battery, which can be coupled with diesel engine to save additional consumption of fuel. A combined electrochemical and thermal simulation analysis of several battery configurations using multiphysics simulation code has also been performed in order to understand the thermal management and cooling requirements of the batteries subject to the charging and discharging requirements of a locomotive engine. Such an analysis assists in addressing the key issue of operating the battery at an maximum efficiency level while dissipating any excessive heat generated during the operation, and maintaining the battery at a desired temperature range using a cooling scheme.

The Mechanism and Application of Effusion Cooling

1959 ◽  
Vol 63 (578) ◽  
pp. 73-89 ◽  
Author(s):  
P. Grootenhuis
Keyword(s):  
Heat Transfer ◽  
Porous Material ◽  
Heat Balance ◽  
Gas Turbines ◽  
Internal Heat ◽  
Published Data ◽  
Insulating Layer ◽  
Rocket Motors ◽  
The Heat Transfer Coefficient ◽  
Internal Heat Transfer

Summary:Effusion cooling consists in forcing a gas under pressure through a porous material thereby absorbing heat from the material and forming a heat insulating layer on the exposed surface. The internal heat transfer between the porous material and coolant is considered and the heat transfer coefficient obtained from experiment. An approximate analysis for the heat insulating effect based on a heat balance method is derived in detail and applied to experiments with porous plugs set into the side of a duct carrying hot gases, and to porcras cylinders swept by hot gases. It has been found that this analysis applies reasonably accurately to the results of these experiments and of most of the published data. The manufacture of porous materials is discussed briefly and a representative list of commercially available materials is included. The application of effusion and sweat cooling to the blading and combustion chamber linings for gas turbines, rocket motors and the outside skin of flying vehicles is considered.

The Effect of Sintering and Soaking Temperature on the Dye-Sensitized Solar Cell Performance

2015 ◽  
Vol 827 ◽  
pp. 135-139
Author(s):  
Tika Paramitha ◽  
Tifa Paramitha ◽  
Agus Purwanto
Keyword(s):  
Solar Cell ◽  
Electrical Energy ◽  
Dye Sensitized Solar Cell ◽  
Maximum Efficiency ◽  
Solar Cell Performance ◽  
Dye Sensitized ◽  
Photoelectrochemical Solar Cell ◽  
Varied Temperature ◽  
Efficiency Test ◽  
Soaking Temperature

Dye-sensitized solar cell (DSSC) is a photoelectrochemical solar cell that is able to convert solar energy into electrical energy. Sintering of TiO2film and soaking process of TiO2film in the dye solution have significant effect on the DSSC performance. The TiO2film was sintered at varied temperature from 200 °C to 500 °C for 60 minutes. From the efficiency test, it is found that the optimum performance of DSSC was produced when the TiO2film was sintered at 450 °C. In addition, the dye soaking temperature was evaluated from the temperature 40 °C to 50 °C for 6 hours. The optimum soaking temperature was 50 °C of DSSC with maximum efficiency at 2,621 %.

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