The Application of Thermomechanical Dynamics (TMD) to Thermoelectric Energy Generation by Employing a Low Temperature Stirling Engine

A thermoelectric generation Stirling engine (TEG-Stirling engine) is discussed by employing a low temperature Stirling engine and the dissipative equation of motion derived from the method of thermomechanical dynamics (TMD). The results and mechanism of axial flux electromagnetic induction (AF-EMI) are applied to a low temperature Stirling engine, resulting in a TEG-Stirling engine. The method of TMD produced thermodynamically consistent and time-dependent physical quantities for the first time, such as internal energy ℰ(t), thermodynamic work Wth(t), the total entropy (heat dissipation) Qd(t)and measure or temperature of a nonequilibrium state T˜(t). The TMD analysis produced a lightweight mechanical system of TEG-Stirling engine which derives electric power from waste heat of temperature (40˚CT100˚C) by a thermoelectric conversion method. An optimal low rotational speed about 30θ′(t)/(2π)60(rpm) is found, applicable to devices for sustainable, clean energy technologies. The stability of a thermal state and angular rotations of TEG-Stirling engine are specifically shown by employing properties of nonequilibrium temperature T˜(t), which is also applied to study optimal fuel-injection and combustion timings of heat engines.

Electricity Generation from Heatwaves

We chose a definition of heatwaves (HWs) that has ~4-year recurrence frequency at world hot spots. We first examined the 1940-2022 HWs climatology and trends in lifespan, severity, spatial extent, and recurrence frequency. HWs are becoming more frequent and more severe for extratropical mid- and low-latitudes. To euphemize HWs, we here propose a novel clean energy-tapping concept that utilizes the available nano-technology, micro-meteorology knowledge of temperature distribution within/without buildings, and radiative properties of earth atmosphere. The key points for a practical electricity generation scheme from HWs are defogging, insulation, and minimizing the absorption of infrared downward radiation at the cold legs of the thermoelectric generators. One sample realization is presented which, through relay with existing photovoltaic devices, provides all-day electricity supply sufficient for providing air conditioning requirement for a residence (~2000-watt throughput). The provision of power to air conditioning systems, usually imposes a significant stress on traditional city power grids during heatwaves.

Cascade utilization of full spectrum solar energy for achieving simultaneous hydrogen production and all-day thermoelectric conversion

Solar-driven photocatalytic water/seawater splitting holds great potential for green hydrogen production.However,the practical application is hindered by the relatively low conversion efficiency resulting from the inadequate utilization of solar spectrum with significant waste in the form of heat.Moreover,current equipment struggles to maintain all-day operation subjected to the lack of light during nighttime.Herein,a novel hybrid system integrating photothermal catalytic(PTC)reactor,thermoelectric generator(TEG),and phase change materials(PCM)was proposed and designed(named as PTC-TEG-PCM)to address these challenges and enable simultaneous overall seawater splitting and 24-hour power generation.The PTC system effectively maintains in an optimal temperature range to maximize photothermal-assisted photocatalytic hydrogen production.The TEG component recycles the low-grade waste heat for power generation,complementing the shortcoming of photocatalytic conversion and achieving cascade utilization of full-spectrum solar energy.Furthermore,exceptional thermal storage capability of PCM allow for the conversion of released heat into electricity during nighttime,contributing significantly to the overall power output and enabling PTC-TEG-PCM to operate for more than 12 h under the actual condition.Compared to traditional PTC system,the overall energy conversion efficiency of the PTC-TEG-PCM system can be increased by∼500%,while maintaining the solar-to-hydrogen efficiency.The advancement of this novel system demonstrated that recycling waste heat from the PTC system and utilizing heat absorption/release capability of PCM for thermoelectric application are effective strategies to improve solar energy conversion.With flexible parameter designing,PTC-TEG-PCM can be applied in various scenarios,offering high efficiency,stability,and sustainability.

Experimental Research on Tank Exhaust's Thermal Restraint Based on Thermoelectric Generation Theory

Aimed at the high temperature of tank's exhaust, the principle of applying thermoelectric generation technology to tank thermal restraint was analyzed. Its application experiments were conducted to test the exhaust temperature under different rotating speeds, The experiment results show that the thermoelectric generator can output sufficient electric energy to drive fans; the external surface temperature of radiator is reduced by over 65.0% compared with exhaust surface due to the combination effect of thermoelectric conversion, fan cooling and heat radiation; the exhaust surface temperature rise caused by increase of the engine's rotating speed results in the increases of the temperature difference of the thermoelectric generator's cold and hot sides, the fan's driving voltage and heat convection, thus, the effect of fan's cooling is more obvious than that of the temperature rise caused by exhaust.

Fabrication and performance evaluation of the thermoelectric generation and performance measuring system

A novel thennoelectric generating and performance measuring system （TGPMS） was designed and fabricated. TGPMS can not only achieve the function of thennoelectric generation, but also measure the thennoelectric performance parameters of the bismuth-telluride-based thennoelectric device accurately. These thennoelectric performance parameters mainly include the dependence of the Seebeck coefficient of the thennoelectric device on the device＇s temperature in the low temperature range （about 40 ~ 190~C ）, and the dependence of the power output and thermoelectric conversion efficiency on the temperature dif- ference or output load. With the optimum load, the optimal value of the power output is 3.39W when the temperature difference reaches 231.2~C, and the optimal value of the conversion efficiency is 3.22% when the temperature difference reaches 208.9~C. TGPMS provides an experimental foundation for the application of the thennoelectric generators in the space field.

Numerical Study of Thermoelectric Generation within a Reciprocal Flow Porous Media Burner

A numerical study based on direct thermal to electric energy conversion was performed in a reciprocal flow porous media burner embedded with two layers of thermoelements. The burner lean combustibility limit was sought in order to maximize global efficiency of thermal to electrical energy conversion by minimizing fuel consumption. Once the pairs of operational variables, composition and filtrational velocity of gas inlet mixture were found, the optimal length and placement of thermoelectric elements within the reactor high thermal gradients were sought to maximize the electric current, thermoelements and system overall efficiency. A two temperature-resistance model for finite time thermodynamics was developed for the thermoelectric elements energy fluxes. Results indicate a distribution of current and efficiencies that presents a maximum at different themoelements length. Maximum values for current and system efficiency obtained were 44.3 m A and 2.5%, respectively.

The Disk-Magnet Electromagnetic Induction Applied to Thermoelectric Energy Conversions

The thermoelectric energy conversion technique by employing the Disk-Magnet Electromagnetic Induction (DM-EMI) and improved DM-EMIs is shown, and possible applications to heat engines as one of the energy harvesting technologies are also discussed. The idea is induced by integrating irreversible thermodynamical mechanism of a water drinking bird with that of a Stirling engine, resulting in thermoelectric energy generation different from conventional heat engines. The current thermoelectric energy conversion with DM-EMI can be applied to wide ranges of temperature differences. The mechanism of DM-EMI energy converter is examined in terms of axial flux magnetic lines and categorized as the axial flux generator. It is useful for practical applications to macroscopic heat engines such as wind, geothermal, thermal and nuclear power turbines and heat-dissipation lines, for supporting thermoelectric energy conversions. The technique of DM-EMI will contribute to environmental problems to maintain clean and susceptible energy as one of the energy harvesting technologies.

Zn_4Sb_3高性能热电材料的制备(英文)

A "reaction-extrusion process" has been developed to prepare Zn4Sb3 bulk materials with high thermoelectric performance.The synthesis,densification,and shape-forming of Zn4Sb3 bulk materials were realized simultaneously in one hot-extrusion process,and the resulting extrudates had high density with single β-Zn4Sb3 phase.A large extrusion ratio and a small punch speed are advantageous to enhance thermoelectric performance.The extruded Zn4Sb3 materials exhibited excellent thermoelectric performance,for example,the dimensionless thermoelectric figure of merit is 1.77 at 623 K,which is 36% higher compared to conventional hot-pressed materials.On the other hand,the incorporation of 1% SiC nanosized particles into Zn4Sb3 matrix leads to improvements in both thermoelectric and mechanical properties.

Photovoltaic,thermoelectric and electromagnetic generation technologies applied in power systems for mobile unmanned systems

Unmanned systems are increasingly adopted in various fields,becoming an indispensable technology in daily life.Power systems are the lifeblood of unmanned systems,and affect the working time and task complexity.However,traditional power systems,such as batteries and fuels have a fixed capacity.Therefore,once the power supply is exhausted and cannot be replenished in time,the unmanned systems will stop working.Hence,researchers have increasingly begun paying attention to renewable energy generation technologies.The principles,advantages,and limitations of renewable energy generation technologies are different,and their application effects in different unmanned systems are also uneven.This paper presents a comprehensive study of the application and development status of photovoltaic,thermoelectric,and magnetoelectric generation technologies in four kinds of unmanned systems,including space,aviation,ground,and water,and then summarizes the adaptability and limitations of the three technologies to different systems.Moreover,future development directions are predicted to enhance the reliability of renewable energy generation technologies in unmanned systems.This is the first study to conduct a comprehensive and detailed study of renewable energy generation technologies applied in unmanned systems.The present work is critical for the development of renewable energy generation technologies and power systems for unmanned systems.

Photothermal hygroscopic hydrogel for simultaneous generation of clean water and electricity

Harvesting water from the air using adsorbents and obtaining fresh water by solar-driven desorption is considered as one of the most effective ways to solve the freshwater crisis in arid and desert regions.Based on a simple and low-cost photothermal hygroscopic hydrogel,a new strategy is proposed to boost solar energy efficiency by coupling solar-driven atmospheric water harvesting technology with thermoelectric power generation technology in this paper.Photothermal hygroscopic hydrogel ink PAM-CaCl_(2)is prepared by in situ polymerization using Acrylamide as monomer,Ammonium persulfate as thermal initiator and CaCl_(2)as hygroscopic component.During the day,the photothermal hygroscopic hydrogel absorbs solar energy and evaporates its own internal water to obtain fresh water.Simultaneously,the residual waste heat is utilized to power the thermoelectric panel,which produces electricity based on Seebeck effect.At night,the hydrogel harvests water molecules in the air to achieve regeneration.This hybrid system can achieve a water production rate of 0.33 kg m^(-2)h^(-1)and an additional electrical energy gain of 124 mW m^(-2)at 1 kW m^(-2)solar intensity.Theoretical model of the hybrid system is developed to understand the heat flow and thermoelectric generation process.The results provide new insights into energy and freshwater replenishment options in arid or desert areas with abundant solar energy.

Thermoelectric interface materials:A perspective to the challenge of thermoelectric power generation module

The past years has observed a significantly boost of the thermoelectric materials in the scale of thermoelectric figure-of-merit,i.e.ZT,because of its promising application to harvest the widely distributed waste heat.However,the simplified thermoelectric materials'performance scale also shifted the focus of thermoelectric energy conversion technique from devices-related efforts to materials-level works.As a result,the thermoelectric devices-related works didn't get enough attention.The device-level challenges behind were kept unknown until recent years.However,besides the thermoelectric materials properties,the practical energy conversion efficiency and service life of thermoelectric device is highly determined by assembling process and the contact interface.In this perspective,we are trying to shine some light on the device-level challenge,and give a special focus on the thermoelectric interface materials(TEiM)between the thermoelectric elements and electrode,which is also known as the metallization layer or solder barrier layer.We will go through the technique concerns that determine the scope of the TEiM,including bonding strength,interfacial resistance and stability.Some general working principles are summarized before the discussion of some typical examples of searching proper TEiM for a given thermoelectric conversion material.

Study on the performance of TEG with heat transfer enhancement using graphene-water nanofluid for a TEG cooling system

Improvement of the heat transfer effect of cold side of a thermoelectric generator(TEG) is one of the approaches to enhance the performance of the TEG systems.As a new type of heat transfer media,nanofluids can enhance the heat transfer performance of working liquid significantly.In this study,the performance of a commercial TEG with graphene-water(GW) nanofluid as coolants in a minichannel heat exchanger is investigated experimentally at low temperatures.The results show that the output power of TEG increases with the flow rate under 950 mL/min.However,the fluid flow rate has no influence on the output power of TEG with higher flow rate(larger than 950 mL/min) when the heat transfer dynamic balance state of the system is reached.The optimal concentration and flow rate of nanofluid are 0.1 wt%and 950 mL/min,respectively.At the optimal conditions,the improved voltage,output power and conversion efficiency with GW nanofluid applied in the cooling system are increased by11.29%,21.55%and 3.5%in comparison with those with only water applied,respectively.

Dynamic reconfiguration for TEG systems under heterogeneous temperature distribution via adaptive coordinated seeker

A thermoelectric generation(TEG)system has the weakness of relatively low thermoelectric conversion efficiency caused by heterogeneous temperature distribution(HgTD).Dynamic reconfiguration is an effective technique to improve its overall energy efficiency under HgTD.Nevertheless,numerous combinations of electrical switches make dynamic reconfiguration a complex combinatorial optimization problem.This paper aims to design a novel adaptive coordinated seeker(ACS)based on an optimal configuration strategy for large-scale TEG systems with series-paral-lel connected modules under HgTDs.To properly balance global exploration and local exploitation,ACS is based on'divide-and-conquer'parallel computing,which synthetically coordinates the local searching capability of tabu search(TS)and the global searching capability of a pelican optimization algorithm(POA)during iterations.In addition,an equivalent re-optimization strategy for a reconfiguration solution obtained by meta-heuristic algorithms(MhAs)is proposed to reduce redundant switching actions caused by the randomness of MhAs.Two case studies are carried out to assess the feasibility and superiority of AcS in comparison with the artificial bee colony algorithm,ant colony optimization,genetic algorithm,particle swarm optimization,simulated annealing algorithm,TS,and POA.Simulation results indicate that ACS can realize fast and stable dynamic reconfiguration of a TEG system under HgTDs.In addition,RTLAB platform-based hardware-in-the-loop experiments are carried out to further validate the hardware implemen-tation feasibility.