Solid State Heat Pump Research Articles

Realizing thermoelectric cooling and power generation in N-type PbS0.6Se0.4 via lattice plainification and interstitial doping

Thermoelectrics have great potential for use in waste heat recovery to improve energy utilization. Moreover, serving as a solid-state heat pump, they have found practical application in cooling electronic products. Nevertheless, the scarcity of commercial Bi2Te3 raw materials has impeded the sustainable and widespread application of thermoelectric technology. In this study, we developed a low-cost and earth-abundant PbS compound with impressive thermoelectric performance. The optimized n-type PbS material achieved a record-high room temperature ZT of 0.64 in this system. Additionally, the first thermoelectric cooling device based on n-type PbS was fabricated, which exhibits a remarkable cooling temperature difference of ~36.9 K at room temperature. Meanwhile, the power generation efficiency of a single-leg device employing our n-type PbS material reaches ~8%, showing significant potential in harvesting waste heat into valuable electrical power. This study demonstrates the feasibility of sustainable n-type PbS as a viable alternative to commercial Bi2Te3, thereby extending the application of thermoelectrics.

Effect of Ni Doping on the Thermoelectric Properties of YbCo2Zn20.

Thermoelectric devices are both solid-state heat pumps and energy generators. Having a reversible process without moving parts is of high importance for applications in remote locations or under extreme conditions. Yet, most thermoelectric devices have a rather limited energy conversion efficiency due to the natural competition between high electrical conductivity and low thermal conductivity, both being essential conditions for achieving a high energy conversion efficiency. Heavy-fermion compounds YbT2Zn20 (T = Co, Rh, Ir) have been reported to be potential candidate materials for thermoelectric applications at low temperatures. Motivated by this result, we applied chemical substitution studies on the transition metal site in order to optimize the charge carrier concentration as well as promote more efficient phonon scatterings. Here, we present the latest investigation on the Ni-doped specimens YbCo2-xNixZn20, where enhanced thermoelectric figure of merit values have been obtained.

APRTC: advanced precise rapid thermal cycling in blow molding by applying fuzzy controller on thermoelectric devices for cooling and heating applications

This study presents an innovative approach to enhance thermal control in the blow molding production process, specifically focusing on achieving rapid and precise temperature regulation. To address the significant time consumption during mold closure, strategically deploying thermoelectric modules (TEMs) arranged according to the mold’s geometry enables meticulous temperature monitoring through integrated thermocouples. The configuration forms a matrix of interconnected TEMs, thermocouples, and controllers, orchestrating precise temperature adjustments across the mold surface. The research integrates fuzzy algorithms to facilitate seamless communication between thermoelectric devices and thermocouples for precise mold temperature control. Simulation of thermoelectric devices using COMSOL Multiphysics and implementation of fuzzy controllers in Matlab, connected through a live-link, enables real-time. I have adjustments and precise control. This integrated approach allows for a comprehensive analysis and optimization of the thermal control system, ensuring effective and adaptive temperature regulation. TEMs, operating as solid-state heat pumps, offer size versatility, adaptability to diverse mold shapes, and maintenance-free operation. Leveraging individual control capabilities significantly enhances heat transfer resolution, enabling precise manipulation of heat flux. Emphasizing the reduction of cooling time and achieving high-gloss surface quality, the study introduces the Advanced Precise Rapid Thermal Cycling in Blow Molding (APRTC) method. APRTC strategically employs TEMs to expedite cooling and elevate temperature determination accuracy, guaranteeing enhanced temperature resolution on the core mold surface. Furthermore, the study optimizes energy utilization through a closed-loop fluid circulation system, harnessing waste energy from other stages. Comparative analysis highlights APRTC's superiority, revealing a remarkable 91%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$91 \\%$$\\end{document} reduction in temperature differentials during the cooling cycle and an 89%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$89 \\%$$\\end{document} decrease in the heating stage. These findings underscore APRTC's efficacy in maintaining minimal temperature variations throughout the entire molding process.

A highly efficient solid-state heat pump.

The high efficiency of a newly developed electrocaloric device brings theory closer to reality.

Performance Study on an Electrocaloric Heat Pump Based on Ga-Based Liquid Metal

A solid-state heat pump using the electrocaloric effect (ECE) provides a new idea for the future development of heat pumps. However, most of the electrocaloric (EC) heat pumps presented in the literature are low in efficiency and use at least one moving part, which significantly reduces the reliability of the heat pump and adds to its complexities. In this context, combining the positive and negative ECEs, we proposed a plate-laminar non-mobile EC heat pump adopting Gallium-based liquid metal as an intermediate medium to guarantee highly efficient heat transfer. Numerical simulation in COMSOL Multiphysics has been performed to investigate the correlation between different operating parameters and the performance of the EC heat pump. Changing the temperature span only, a COP of 8.13 and a UVHP of 746.1 W·dm−3 were obtained at a temperature span of 7 K. It was also found that the UVHP increased by 28.45% and COP increased by 25.46% after adding one layer of EC material. The electric-induced quantity of heat and cooling capacity was found to significantly affect the heating performance. The biggest heating power of 7132.7 W·dm−3 was obtained under 200 MV·m−1, and the biggest COP of 14.84 was obtained under 150 MV·m−1 at a cyclic period of 8 s. This study provides a highly efficient, non-mobile EC heat pump that employs fluid-thermal conjugated heat transfer, and exploration of the parameters makes the optimization of the heat pump possible by fine-tuning the operation parameters.

Employing the Peltier Effect to Control Motor Operating Temperatures

Electrical insulation failure is the most common failure mechanism in electrical machines (motors and generators). High temperatures and/or temperature gradients (HTTG) are the main drivers of insulation failure in electrical machines. HTTG combine with and augment other destructive effects from over-voltage, to voltage transients, overload and load variations, poor construction techniques, and thermal cycling. These operating conditions cause insulation damage that leads to electrical insulation failure. The insulation failure process is greatly accelerated by pollutants and moisture absorption. A simple and robust way to reduce HTTG and moisture adsorption is by maintaining constant internal temperatures. The current method to maintain elevated internal temperatures and reduce condensation issues is by internal electrical heating elements. This paper examines the effectiveness of applying thermoelectric coolers (TECs), solid-state heat pumps (Peltier devices), as heaters to raise a motor’s internal temperature by pumping heat into the motor core rather than heating the internal air. TEC technology is relatively new, and the application of TECs to heat a motor’s internal volume has not previously been explored. In this paper, we explore the hypothesis that TECs can pump heat into a motor when out of service, reducing the HTTG by maintaining high winding slot temperatures and eliminating condensation issues. This paper describes a test motor setup with simple resistive heating (traditional method), compared with the application of TECs with heat sinks, heat pipes, and a water circulation heat exchanger, to gauge the capability of TECs to heat the inner core or winding area. In this paper, we demonstrate the full integration of TECs into a motor. The results show that each of the systems incorporating the TECs would effectively pump heat into the core and keep the winding hot, eliminating condensation issues and water ingress due to thermal cycling.

Electrocaloric heat pumps using two independently-controlled layers to achieve high cooling power

The development of electrocaloric materials (ECMs) with strong electrocaloric effect (ECE) in recent years offers a great opportunity for the development of solid-state heat pumps without using environmentally unfriendly vapor-based technologies. Currently existing ECE-based heat pumps (CEHPs) use one ECM layer that has to be moved back and forth between the thermal source (SO) and sink (SI), which raises reliability and safety concerns. Here, a design, which uses two layers of an ECM and the electric field on each layer is independently controlled with a special pattern, is introduced to develop ECE-based heat pumps with a high cooling power. In the design, the two ECM layers are permanently bound together and used as a single ECM module. The performance of the heat pumps is calculated using the newly introduced analytical solutions. First of all, it is found that the cooling power of CEHPs is strongly dependent on, while the cooling power of heat pumps using the two-ECM-layers module (TELM) is insensitive to, the materials used as the SO/SI. This would significantly expand the application of ECE-based heat pumps since in many applications there is no freedom to choose the materials to be used as the SO/SI. Secondly, the heat pumps using the TELM exhibit a high cooling power. For example, when different materials are used as the SO/SI, the cooling power of CEHPs would be changed over more than 100 times, while it is only changed less than 2 times when the TELM is used to replace the ECM layer used in CEHPs. And the cooling power of heat pumps using the TELM can be more than 7 times higher than the highest cooling power obtained in CEHPs. More importantly, the TELM can be permanently bound to the SO (or the SI) (i.e., the ECM is not moved at all during the operation), which would result in a high reliability. In this case, the cooling power of the heat pumps using the TELM can only be changed less than 25 % when different materials are used as the SO/SI and this cooling power is close to the highest cooling power obtained in the CEHPs.

Identification of ARX Model for Thermoelectric Cooling on Glass Windows

Thermoelectric cooling (TEC) is a solid-state heat pump that uses the Peltier effect to dissipate the heat generated by the electronic packaging system. TECs are widely used in aerospace, military, scientific work and industry due to small size, lack of moving parts, and ease of integration. In this study, a cooling system integrated with TEC is developed in a testing area (lecturer’s office) with the aim to reduce the temperature of the hot glass window area due to solar radiation that passes through it. This cooling system used direct TEC, for keeping the cooling temperature on the window to about 26 °C which is equivalent to an air conditioning setting temperature of 26 °C set during the experiment. This work includes experimental and modelling studies conducted on cooling systems integrated with TEC. The main target of this study is to develop a dynamic model of a cooling system integrated with TEC. The black box modelling approach in producing a mathematical model was selected based on the ARX model that corresponds to the actual dynamic state of the cooling system. The best model was finalized based on the best match on curve patterns when comparing the real and estimated models using the system identification tools in MATLAB, and also had the least error. The accuracy of the models was compared and analysed. The results showed that the 4th order of the ARX model produced a higher best fitting and standard deviation values of 78.14% and 0.030769. This system accuracy is almost within the acceptable range for most error calculations in the validation method. In addition, the ARX model is found incapable of achieving the highest fitting due to the losses from the dynamic environment and losses from the TEC itself. Still, the use of this black box model used in this study is a significant variation where system parameters can be identified even offline.

Barocaloric Properties of Thermoplastic Elastomers

Solid-state refrigeration represents a promising alternative to vapor compression refrigeration systems which are inefficient, unreliable, and have a high global warming potential. However, several solid-state cooling technologies—including those relying on a temperature change induced by an applied electric field (electrocaloric effect), magnetic field (magnetocaloric effect), and uniaxial stress (elastocaloric effect)—have been investigated, but their efficiency and scalability remain a concern. Materials with a large barocaloric response—temperature/entropy change induced by hydrostatic pressure—hold a significant promise for solid-state cooling but remain comparatively less explored. These materials need to be inexpensive, compressible, and show a large barocaloric response around the temperature of interest. Soft materials have the potential to meet these requirements and enable the development of low-cost high-efficiency solid-state heat pumps. Here, we investigate the barocaloric performance of commercially available block copolymer thermoplastic elastomers. We characterized the mechanical, thermal, and barocaloric properties of these materials and evaluated their potential for solid-state refrigeration. We utilized rheometric measurements to evaluate the isothermal compressibility and normalized refrigerant capacity of the thermoplastic elastomers. In addition, we directly measured the pressure-induced temperature change of the test materials and compared them with their normalized refrigeration capacity. The measured isothermal compressibility was in the 0.1–0.4 GPa−1 range, while the normalized refrigeration capacity varied between 13.2 and 41.9 kJ K−1 GPa−1 for a 100 MPa applied pressure and 65°C temperature span. The corresponding pressure-induced temperature change for an applied pressure of 434.1 MPa varied between 2.2 and 28°C. These results demonstrated the superior barocaloric properties of thermoplastic elastomers and their promise for next generation barocaloric solid-state refrigeration devices.

Phase-transition-induced giant Thomson effect for thermoelectric cooling

The Seebeck and Peltier effects have been widely studied and used in various thermoelectric technologies, including thermal energy harvesting and solid-state heat pumps. However, basic and applied studies on the Thomson effect, another fundamental thermoelectric effect in conductors, are limited despite the fact that the Thomson effect allows electronic cooling through the application of a temperature gradient bias rather than the construction of junction structures. In this article, we report the observation of a giant Thomson effect that appears owing to magnetic phase transitions. The Thomson coefficient of FeRh-based alloys reaches large values approaching –1000 μV K−1 around room temperature because of the steep temperature dependence of the Seebeck coefficient associated with the antiferromagnetic–ferromagnetic phase transition. The Thomson coefficient is several orders of magnitude larger than the Seebeck coefficient of the alloys. Using the active thermography technique, we demonstrate that the Thomson cooling can be much larger than Joule heating in the same material even in a nearly steady state. The operation temperature of the giant Thomson effect in the FeRh-based alloys can be tuned over a wide range by applying an external magnetic field or by slightly changing the composition. Our findings provide a new direction in the materials science of thermoelectrics and pave the way for thermal management applications using the Thomson effect.

Distributed and localized cooling with thermoelectrics

G. Jeffrey Snyder is a Professor of Materials Science and Engineering at Northwestern University in Evanston Illinois. His interests are focused on engineering of electronic and thermal properties, and he is well known for his work on thermoelectric materials. He has developed new methods of electron band structure engineering and microstructure engineering of thermal and electrical properties of complex materials. His interdisciplinary approach stems from his background in solid state chemistry at Cornell University and the Max Planck Institute for solid state research, applied physics at Stanford University, and thermoelectric materials and device engineering at NASA/Jet Propulsion Laboratory and California Institute of Technology (Caltech).

The employment of caloric-effect materials for solid-state heat pumping

In this paper we draw a map of the energy performances of a solid-state caloric heat pump working with different caloric-effect materials. The investigation is performed considering a number of various caloric effect materials and employing them in a caloric heat pump based on Active Caloric Regenerative heat pumping cycle. The tests were performed through a 2-Dimensional model, already validated in previous investigations, solved with Finite Element Method. The employed materials selected are electrocaloric and mechanocaloric; gadolinium, the benchmark magnetocaloric material, was also tested for comparative purposes. We evaluated the energy performances of the heat pump as temperature span, heating power and coefficient of performance. From global considerations based on the simultaneous evaluation of these three energy parameters, we consider mechanocaloric as the most suitable caloric effect to be employed for heat pump applications, especially with reference to the elastocaloric Ni–Ti and to the barocaloric Acetoxy Silicone Rubber, since their heating powers with respect to the energy expenses required, give satisfying coefficients of performance and temperature spans.

A Full-Solid-State Humidity Pump for Localized Humidity Control

Summary Humidity management is essential and widely needed in various fields. Traditional moisture removal technologies are mostly based on cooling condensation or desiccant dehumidification. These methods come with inherent defects of energy efficiency and are bulky and complex for small-space humidity-control applications. Here, we demonstrate a full-solid-state humidity pump using the advantages of commercial thermoelectric coolers and silica gel materials. Silica gel is coated on the surface of heat sinks to minimize contact thermal resistance between the material and heat source while maintaining enough heat and mass transfer area between the desiccant and the air. The humidity pump device exhibits 0.61 g W−1 h−1 humidity transfer efficiency, corresponding to a humidity transfer rate of 28.38 g h−1. The proposed device neither uses refrigerant nor introduces liquid water. It opens up the possibility of use in localized humidity control applications with higher efficiency and a wider ambient temperature range than traditional technologies.

Optimalisasi sistem pendingin berbasis termoelektrik berpendingin air

The use of refrigerator and air conditioner in human life causes increase in use of hydrocarbon and fluorocarbon each year. Hydrocarbon and fluorocarbon are hazardous subtances that can make a hole in ozone that cause increase in receive of ultraviolet on earth, that will give negative impact on human health. Thermoelectric refrigeration as a solid state heat pump is a safe solution to subtitute the used of hidrocarbons and fluorocarbons based refrigerator and air conditioner. The experiment is conducted to test a thermoelectric based refrigeration system which uses water as a working fluid. The result shows that refrigeration system will be optimum at 6V and 2.24A of electricity consumption, and 0.5 and 1 litre/minute of water flowrate . While Coefficient of Performance (COP) of the system is 0.86.

Numerical simulation on a compact thermoelectric cooler for the optimized design

Nowadays electronic devices’ increasing in power density and shrinking in size make it hard to remove the heat. The resulting uneven energy dissipation and high local heat flux density create hotspots that deteriorate the thermal environment. The thermoelectric cooler (TEC) is a promising solid-state heat pump that utilizes the Peltier effect to dissipate the heat and eliminate the hotspots of the electronic devices. In this article, three-dimensional numerical simulations have been performed for the optimization design of a compact TEC using finite element method, which take into account the temperature-dependent materials properties, Thomson effect, and the contact layer resistances. The optimization includes the input current, leg geometry, and contact layers, with which the TEC achieves the maximum cooling performance and high operation reliability. The results show that the Joule heat generated by the input current inside the module plays a crucial role in the TEC performance and the operation reliability. The strong temperature gradient-induced reliability issue still occurs in the TEC. With the requirements for optimal performance and reliability, the optimized TEC design approach is presented in this study.

Design and characterization of hybrid III–V concentrator photovoltaic–thermoelectric receivers under primary and secondary optical elements

Lattice-matched monolithic triple-junction Concentrator Photovoltaic cells (InGa(0.495)P/GaIn(0.012)As/Ge) were electrically and thermally interfaced to two Thermoelectric Peltier module designs. An electrical and thermal model of the hybrid receivers was modelled in COMSOL Multiphysics software v5.3 to optimize cell cooling whilst increasing photon energy conversion efficiency. The receivers were measured for current–voltage characteristics with the cell only (with sylguard encapsulant), under single secondary optical element at x2.5 optical concentration, and under Fresnel lens primary optical element concentration between x313 and x480. Measurements were taken in solar simulators at Cardiff and Jaén Universities, and on-sun with dual-axis tracking at Jaén University. The hybrid receivers were electrically, thermally and theoretically investigated. The electrical performance data for the cells under variable irradiance and cell temperature conditions were measured using the integrated thermoelectric module as both a temperature sensor and as a solid-state heat pump. The performance of six hybrid devices were evaluated within two 3-receiver strings under primary optical concentration with measured acceptance angles of 1.00° and 0.89°, similar to commercially sourced Concentrator Photovoltaic modules. A six-parameter one-diode equivalent electrical model was developed for the multi-junction cells under both primary and secondary optical concentration. This was applied to extract six model parameters with the experimental current–voltage curves of type A receiver at 1, 3 and 500 concentration ratios. Standard test conditions (1000 W/m2, 25 °C and Air Mass 1.5 Global spectrum) were assumed based on trust-region-reflective least squares algorithm in MATLAB. The model fitted the experimental current–voltage curves satisfactorily with a mean error of 4.44%. The combined primary and secondary optical intensity gain coefficient is as high as 0.92, in comparison with 0.50–0.86 for crossed compound parabolic concentrators. The determined values of diode reverse saturation current, combined series resistance and shunt resistance were similar to those of monocrystalline PV cell/modules in our previous publications. The model may be applicable to performance prediction of multi-junction CPV cells in the future.

Experimental characterization and multi-physics simulation of a triple-junction cell in a novel hybrid III:V concentrator photovoltaic–thermoelectric receiver design with secondary optical element

A lattice-matched monolithic triple-junction Concentrator Photovoltaic cell (InGa(0.495)P/GaIn(0.012)As/Ge) was electrically and thermally interfaced to a Thermoelectric Peltier module. A single optical design secondary lens was bonded to the CPV-TE receiver. The hybrid SILO-CPV-TE solar energy harvesting device was electrically, thermally and theoretically investigated. The electrical performance data for the cell under variable irradiance and cell temperature conditions were measured using the integrated thermoelectric module as both a temperature sensor and as a solid-state heat pump. The cell was electrically characterised under standard test conditions (1000 W/m2 irradiance, 25°C temperature and AM1.5G spectrum) for comparison with literature data. Transient multiphysics simulations in ANSYS CFX 15.0 were carried out to calculate cell temperatures and to determine the short circuit current and temperature coefficient in a scaling law. The optimization was used to determine 15 model parameters for the component sub-cells within the triple-junction cell at STC with a MATLAB scaling law. The root-mean-square error in electrical currents between measurement and simulations was 0.66%.

Thermal imaging of spin Peltier effect.

The Peltier effect modulates the temperature of a junction comprising two different conductors in response to charge currents across the junction, which is used in solid-state heat pumps and temperature controllers in electronics. Recently, in spintronics, a spin counterpart of the Peltier effect was observed. The ‘spin Peltier effect' modulates the temperature of a magnetic junction in response to spin currents. Here we report thermal imaging of the spin Peltier effect; using active thermography technique, we visualize the temperature modulation induced by spin currents injected into a magnetic insulator from an adjacent metal. The thermal images reveal characteristic distribution of spin-current-induced heat sources, resulting in the temperature change confined only in the vicinity of the metal/insulator interface. This finding allows us to estimate the actual magnitude of the temperature modulation induced by the spin Peltier effect, which is more than one order of magnitude greater than previously believed.

Performance of Thermoelectric Module as a Water Cooler and Water Heater

This paper presents the total Coefficient of Performance (CoP) of a thermoelectric module in combined heating and cooling modes, obtained through experiments and thermodynamics mathematical model. Thermoelectric module is a solid state heat pump which has a capability to pump heat with the capacity of 100 W or lower. One of the module surface will acts as a heat sink while another surface of the module rejects heat. This provides an opportunity to utilize both surfaces for cooling and heating applications. The objective of this work was to determine the total CoP of the thermoelectric module when it was operated in a combination of heating and cooling modes. The total CoP was inferred by fitting the temperature of cold and hot water streams which were obtained from experiments to a mathematical model of the thermoelectric heating and cooling system. The highest temperature difference between hot and cold streams was 40 Kelvin. The worst root-mean-square error between the measured and calculated temperature was 2 Kelvin, except for the hot stream temperature curve in the Condition 1(RMS error was 3.5 Kelvin). It was proved that the total CoP of 4.5 was achievable for thermoelectric module operated in the combined heating and cooling modes. However, the total CoP decreased as the temperature difference between hot and cold streams was increased. It can be concluded that the use of thermoelectric module in heating and cooling modes can improve its CoP which contribute to saving in electrical consumption by the module.

Analyzing the dynamics of brain circuits with temperature: Design and implementation of a miniature thermoelectric device

Traditional lesion or inactivation methods are useful for determining if a given brain area is involved in the generation of a behavior, but not for determining if circuit dynamics in that area control the timing of the behavior. In contrast, localized mild cooling or heating of a brain area alters the speed of neuronal and circuit dynamics and can reveal the role of that area in the control of timing. It has been shown that miniaturized solid-state heat pumps based on the Peltier effect can be useful for analyzing brain dynamics in small freely behaving animals (Long and Fee, 2008). Here we present a theoretical analysis of these devices and a procedure for optimizing their design. We describe the construction and implementation of one device for cooling surface brain areas, such as cortex, and another device for cooling deep brain regions. We also present measurements of the magnitude and localization of the brain temperature changes produced by these two devices.