Experimental study on low-temperature waste heat thermoelectric generator

In order to further studies on thermoelectric generation, an experimental thermoelectric generator unit incorporating the commercially available thermoelectric modules with the parallel-plate heat exchanger has been constructed. The experiments are carried out to examine the influences of the main operating conditions, the hot and cold fluid inlet temperatures, flow rates and the load resistance, on the power output and conversion efficiency. The two operation parameters such as the hot fluid inlet temperature and flow rate are found to significantly affect the maximum power output and conversion efficiency. A comparison of the experimental results with those from the previously published numerical model is also presented. The meaningful results obtained here may serve as a good guide for further improving the numerical model and conducting a system level optimization study in the next step. Also, the present study shows the promising potential of using this kind of thermoelectric generator for low-temperature waste heat recovery.     

Powering microbial electrolysis cells by electricity generation from simulated waste heat of anaerobic digesters using thermoelectric generators

Waste heat from anaerobic digesters can be converted to electricity by using thermoelectric generators (TEG). Herein, such energy was employed to power a microbial electrolysis cell (MEC) for producing hydrogen gas. Four TEG units could deliver a voltage of ~0.5 V, sufficient to drive the MEC that achieved a hydrogen production rate of 0.48 ± 0.13 m³ m⁻³ d⁻¹. This rate was further improved to 0.75 ± 0.05 m³ m⁻³ d⁻¹ when the temperature difference for TEG was increased from 18 to 28 °C. There was no significant difference between the TEG-powered MEC and power supply-supported MEC (at 0.6 V), in terms of current generation, hydrogen production, and organic removal. Ambient air was also studied as a cold-side source for TEG, although some challenges were encountered to maintain a large temperature difference. Those results will encourage further exploration of using TEG as a feasible power supply for sustainable MEC operation.     

A mathematic model of thermoelectric module with applications on waste heat recovery from automobile engine

Over two-thirds energy of fuel consumed by an automobile is discharged to the surroundings as waste heat. The fuel usage can be more efficient if thermoelectric generators (TEG) are used to convert heat energy into electricity. In this study, a thermoelectric module composed of thermoelectric generators and a cooling system is developed to improve the efficiency of an IC engine. Two potential positions on an automobile are chosen to apply this module, e.g. exhaust pipe and radiator to examine the feasibility. To predict the behaviors of this module, a one dimensional thermal resistance model is also build, and the results are verified with experiments.     

Design and testing of a locally made loop-type thermosyphonic heat sink for stove-top thermoelectric generators

The performance of a thermoelectric generator, among other aspects, depends on the use of an effective heat sink. While forced cooling using either air or water (or other coolants) is efficient, it is parasitic on the generated power and/or bulky and inconvenient. Heat pipes are known to be highly effective heat transport devices. Coupled to a thermoelectric generator, these can be used to give acceptable power output. Basing the cooling on water gives low-cost, simplicity, safety, together with good performance. In this work, the design and general performance of a small single-module thermoelectric generator configured for a stovetop waste-heat application and coupled to a locally-made thermosyphonic loop-type heat sink was undertaken. Development and performance cctesting gave mixed results and further numerical and experimental study is under way.     

Study of the influence of heat exchangers' thermal resistances on a thermoelectric generation system

In this paper, a computational study of the influence of the heat exchangers' thermal resistances (in both the hot and cold side) on the efficiency of a thermoelectric generation device has been carried out.     

Experimental investigation of a novel heat pipe thermoelectric generator for waste heat recovery and electricity generation

Waste heat recovery helps reduce energy consumption, decreases carbon emissions, and enhances sustainable energy development. In China, energy-intensive industries dominate the industrial sector and have significant potential for waste heat recovery. We propose a novel waste heat recovery system assisted by a heat pipe and thermoelectric generator (TEG) namely, heat pipe TEG (HPTEG)，to simultaneously recover waste heat and achieve electricity generation. Moreover, the HPTEG provides a good approach to bridging the mismatch between energy supply and demand. Based on the technical reserve on high-temperature heat pipe manufacturing and TEG device integration, a laboratory-scale HPTEG prototype was established to investigate the coupling performances of the heat pipes and TEGs. Static energy conversion and passive thermal transport were achieved with the assistance of skutterudite TEGs and potassium heat pipes. Based on the HPTEG prototype, the heat transfer and the thermoelectric conversion performances were investigated. Potassium heat pipes exhibited excellent heat transfer performance with 95% thermal efficiency. The isothermality of such a heat pipe was excellent, and the heat pipe temperature gradient was within 15°C. The TEG's thermoelectric conversion efficiency of 7.5% and HPTEG's prototype system thermoelectric conversion efficiency of 6.2% were achieved. When the TEG hot surface temperature reached 625°C, the maximum electrical output power of the TEG peaked at 183.2 W, and the open-circuit voltage reached 42.2 V. The high performances of the HPTEG prototype demonstrated the potential of the HPTEG for use in engineering applications.     

Experimental and analytical study on thermoelectric self cooling of devices

This paper presents and studies the novel concept of thermoelectric self cooling, which can be introduced as the cooling and temperature control of a device using thermoelectric technology without electricity consumption.For this study, it is designed a device endowed with an internal heat source. Subsequently, a commonly used cooling system is attached to the device and the thermal performance is statistically assessed. Afterwards, it is developed and studied a thermoelectric self cooling system appropriate for the device.Experimental and analytical results show that the thermal resistance between the heat source and the environment reduced by 25-30% when the thermoelectric self cooling system is installed, and indicates the promising applicability of this technology to devices that generate large amounts of heat, such as electrical power converters, transformers and control systems. Likewise, it was statistically proved that the thermoelectric self cooling system leads to significant reductions in the temperature difference between the heat source and the environment, and, what is more, this reduction increases as the heat flow generated by the heat source increases, which makes evident the fact that thermoelectric self cooling systems work as temperature controllers.     

Improving power density and efficiency of miniature radioisotopic thermoelectric generators

We have built and tested a prototype miniaturized thermoelectric power source that generates 450 μW of electrical power in a system volume of 4.3 cm³. The measured power density of 104 μW cm⁻³ exceeds that of any previously reported thermoelectric power system of equivalent size. This improvement was achieved by implementing a novel thermopile design in which wagon wheel-shaped thermoelectric elements contact the entire circumference of the heat source whereas traditional approaches utilize only one heat source surface. The thermopile consists of 22 wagon wheel-shaped elements (11 P–N thermocouples) fabricated from 215-μm thick bismuth–telluride wafers having ZT = 0.97 at 30 °C. The power source operates on a 150 mW thermal input provided by an electrical resistance heater that simulates a capsule containing 0.4 g of ²³⁸PuO₂ located at the center of the device. Our primary research objective was to develop and demonstrate a prototype thermopile and radioisotopic thermoelectric generator (RTG) architecture with improved power density at small scales. Output power from this device, while optimized for efficiency, was not optimized for output voltage, and the maximum power was delivered at 41 mV. We also discuss modifications to our prototype design that result in significantly improved voltage and power. Numerical predictions show that a power output of 1.4 mW, power density of 329 μW cm⁻³, and voltage of 362 mV, is possible in the same package size.     

Experimental investigation of thermoelectric power generation versus coolant pumping power in a microchannel heat sink

The coolant heat sinks in thermoelectric generators (TEG) play an important role in order to power generation in the energy systems. This paper explores the effective pumping power required for the TEGs cooling at five temperature difference of the hot and cold sides of the TEG. In addition, the temperature distribution and the pressure drop in sample microchannels are considered at four sample coolant flow rates. The heat sink contains twenty plate-fin microchannels with hydraulic diameter equal to 0.93 mm. The experimental results show that there is a unique flow rate that gives maximum net-power in the system at the each temperature difference.     

Modeling,experimental study and optimization on low-temperature waste heat thermoelectric generator system

Thermoelectric generation technology, due to its several kinds of merits, especially its promising applications to waste heat recovery, is becoming a noticeable research direction. Based on basic principles of thermoelectric generation technology and finite time thermodynamics, thermoelectric generator system model has been established. In order to investigate viability and further performance of the thermoelectric generator for waste heat recovery in industry area, a low-temperature waste heat thermoelectric generator setup has been constructed. Through the comparison of results between theoretic analysis and experiment, reasonability of this system model has been verified. Testing results and discussion show the promising potential of using thermoelectric generator for low-temperature waste heat recovery, especially in industrial fields. Several suggestions for system performance improvement have been proposed through the analysis on this system model, which guide optimization and modification of this experimental setup. By integrating theoretic analysis and experiment, it is found that besides increasing waste heat temperature and TE modules in series, expanding heat sink surface area in a proper range and enhancing cold-side heat transfer capacity in a proper range can also be employed to enhance performance of this setup.     

高温热管在小氮肥余热回收中的应用

将高温热管蒸汽发生器应用于小氮肥造气工艺，以取代原普通余热锅炉回收煤气工段的高温余热，解决了合成氨生产工艺中煤气降温的难题，取得了很好的经济效益和社会效益。     

A novel maximum power point tracker for thermoelectric generation system

In this paper, a novel hybrid maximum power point tracking (MPPT) method is proposed and investigated. The proposed MPPT technique combines the simplicity of perturb and observe (P&O) method and the fast tracking ability of open circuit voltage (OCV) method. The advantages of the proposed MPPT approach include fast tracking speed, no additional circuit required and no temporary power loss. To validate the feasibility of the proposed MPPT technique, an 1.2 kW thermoelectric generation system for industrial waste heat recovery is also constructed, experimental results show that comparing with conventional P&O technique, the proposed method can improve the tracking speed for 42.9% and 86.2% when temperature differences are ΔT = 60 °C and ΔT = 180 °C, respectively. Moreover, the energy loss can be improved by 24.0% and 87.0% when temperature differences are ΔT = 60 °C and ΔT = 180 °C, respectively.     

火电厂低温余热利用技术应用分析

综述火电厂低温余热利用技术的特点及应用现状,并对各种技术进行了对比分析,其中集中式吸收式热泵供热技术在当前应用最广泛,是最具发展前景的技术。苇湖梁电厂低温余热利用项目是集中式吸收式热泵125MW水冷机组技术在国内的首次工程应用,项目具有显著的节能效果,可实现年节约标煤41688t,节水65.88万t。     

Design of innovative power conditioning system for the grid integration of thermoelectric generators

Recently, thermoelectric generators (TEGs) have emerged as a potential alternative for clean energy generation, due mainly to the technology innovation and the marked cost reduction of modules, as well as their distinctive advantages. In a TEG system, the electronic power conditioning system (PCS) plays a vital role in ensuring the effective power grid integration, since it is subject to requirements related not only to the variable thermal source itself but also to its effects on the grid operation. This paper proposes an enhanced structure of PCS for the grid integration of TEG arrays to maximize the energy capture from a variable heat source. The innovative topology employed consists of a Z-source inverter that allows the flexible, efficient and reliable generation of high quality electric power from the TEG array. A full detailed model is described and its control scheme is designed. The dynamic performance of the proposed systems is fully validated by computer simulation and experimental studies.     

Numerical study of thermoelectric power generation for an helicopter conical nozzle

This paper investigates the electric power extractable from an helicopter conical nozzle equipped with thermoelectrical modules. The thermoelectric nozzle is heated by the final exhaust gas from helicopter turbine and cooled by oil. A computer model has been developed to simulate the performance of the thermoelectric system. Results were obtained for various operating conditions showing that the electrical power produced in real operating conditions is significant but currently insufficient if we consider the weight-to-power ratio. The numerical model is also used to optimize the electric power showing a good potential for the future.     

Maximum power density analyses of a novel hybrid system based upon solid oxide fuel cells,vacuum thermionic generators and thermoelectric generators

Apart from electricity, solid oxide fuel cell (SOFC) generates a great deal of high-grade exhaust heat, which must be immediately removed to guarantee SOFC's normal operation. To harvest the exhaust heat and improve the overall energy conversion efficiency, a new hybrid system model based upon a SOFC, a vacuum thermionic generator (VTIG) and a thermoelectric generator (TEG) is first proposed. Considering the main thermodynamic-electrochemical irreversible effects, the performance indicators assessing the whole system performance are mathematically derived. In comparison with the performance of sole SOFC, the effectiveness and feasibility of the presented system are verified. Numerical calculation examples illustrate that maximum achievable power density (MAPD) and its corresponding efficiency, exergetic efficiency and exergy destruction rate are, respectively, 26.8%, 9.8%, 9.8% and 8.8% larger than that of the stand-alone SOFC. Exhaustive sensitivity analyses are further conducted to investigate the impacts of various parameters on the tri-generation system performance. Results indicate that the grain size and average pore diameter of electrodes in SOFC and the thermoelectric element number in TEG can be optimized to maximize the hybrid system power density.     

铁合金矿热炉余热发电双压系统的技术应用分析

基于铁合金矿热炉立式双压余热发电系统,首先对4台25500kV·A硅铁矿热炉冶进行了余热资源评估及?值分析,得出烟气余热?值为65528.24MJ/h,其次对过热器热端温差取40℃,蒸发器窄点温差取30℃,省煤器接近点温差取5.0℃,得出双压系统产生蒸汽1.55MPa、360℃、40.2t/h,蒸汽0.3MPa、180℃、7.5t/h,单压系统产生蒸汽1.15MPa、360℃、42.1t/h,双压系统比单压系统排烟温度低21.5℃,汽耗率高0.16kWh/kg,发电机输出功率高774.07KW,系统整体效率高1.6%,再次根据工程实际运行经验,得出双压立式锅炉传热特性、汽水循环方式、漏风量、系统阻力、清灰效果、占地面积等均优于单压卧式锅炉。然后根据4台25500kV·A硅铁矿热炉运行情况,对双压系统进行了经济效益分析,得出年均税后利润为1142万元,全投资内部收益率20.8%,全投资回收期3.7年。最后进行了展望,根据全国年产量铁合金约为1300万吨,余热利用年发电量约能达到100亿KWh,所以这项技术具有广阔的运用前景。     

Effects of fuel cell vehicle waste heat temperatures and cruising speeds on the outputs of a thermoelectric generator energy recovery module

A thermoelectric generator (TEG) module is designed to harvest low grade waste heat from a 2 kW fuel cell vehicle and improve its energy utilization. The module integrates a TEG cell with a heat pipe and a finned heat sink. A numerical model is developed based on an experiment setup where the fuel cell temperature is 45–60 °C while the cruise speed is 25 kmh^?1. The numerical model is validated with less than 5% deviation. Extended cases are simulated for series and parallel power train configuration under changes to the waste heat temperature and vehicle speeds to evaluate the power and heat recovery ratio. A single TEG cell output between 2 and 3 W is achievable even at low grade heat. The parallel drive generates 50% more power than the series drive at 100 kmh^?1 speed. A 2% heat recovery is theoretically achievable for a 16 cell module assembly.     

A novel ice slurry producing system: Producing ice by utilizing inner waste heat

Ice storage is a potential energy saving method for air conditioning systems. An ice slurry is an ideal material for ice storage. The conventional ice slurry producing method using supercooled water suffers from the instability of ice block and depends heavily on electric power. A novel ice slurry producing system utilizing inner waste heat was proposed to improve this situation. This system consists of two major processes: an evaporative supercooling process and a liquid dehumidification process. Both theoretical and experimental works are presented about these two processes. Simulation analysis has been made on the evaporative supercooling process and the performance of the whole system. Experiments were performed about the two processes. The theoretical conclusion agrees well with the experimental results. Compared with the conventional system, this new system can alleviate the burden on electric power and raise the efficiency. Those improvements are essentially attributed to the reutilization of the inner waste heat generated from the system itself.