Thermoelectric Energy Harvesting Device Research Articles

Interface-driven seebeck effect in two-dimensional trilayer-stacked PtTe2/MoS2/MoS2 heterostructures via electron–electron interactions

Two-dimensional (2D) platinum telluride (PtTe2), which is one of the promising metallic transition metal dichalcogenides, has been proven as an essential candidate for electronic devices, magnetic devices, type-II Dirac fermions, topological superconductors, and other optoelectronic applications. However, the formation and thermal transport as important thermoelectric (TE) device applications have not been realized in large-area 2D PtTe2 films due to their semi-metallic properties. Here, we report an innovative approach to enhance the in-plane TE power factors by piling the metallic PtTe2 films on high-resistance (> 10 MΩ) intrinsic MoS2 films to form bilayer-PtTe2/MoS2 (5 nm/7 nm)//sapphire and trilayer-PtTe2/MoS2/MoS2 (5 nm/7 nm/7 nm)//sapphire heterostructures via wet-transfer stacking method. Such approaches can be achieved by utilizing 2D/2D heterostructure to increase the electron effective mass due to the strong electron–electron interaction at interface under temperature gradient along the samples and ultimately increase Seebeck coefficients via interface-driven Seebeck effect along with a metallic high-conductivity top-PtTe2 films. The trilayer-stacked PtTe2/MoS2/MoS2 heterostructures exhibit an extremely high Seebeck coefficient of −21.6 μV/K and power factor of ∼0.2 mW/m·K2, which are 231 % and ∼727 %, higher than those of the metallic 5-nm-thick single PtTe2 film on the sapphire substrate, respectively. Our new physics and observation can pave the way toward an effective strategy for understating 2D/2D TMDC heterostructure materials for high Fig.-of-merit TE energy harvesting devices.

Thermoelectric energy harvesting for wireless onboard rail condition monitoring

ABSTRACT A thermoelectric energy harvesting device is evaluated to power a bearing health monitoring system. Unlike wayside equipment, the new system is an onboard wireless solution utilizing accelerometer and temperature sensors to assess the bearing condition continuously. The harvesting system consists of two thermoelectric generator modules with aluminium heat sinks, a switching boost converter, a battery management circuit, and a lithium rechargeable battery. The performance of the harvester is validated on an AAR class bearing mounted on a laboratory tester, with load and speed simulating common freight routes of up to 896 miles. The energy harvested varies with operating conditions, and data is presented showing the effect of load and speed. Over a realistic route, the net energy harvested is more than double that needed to indefinitely power a Bluetooth Low Energy sensor. The critical design parameters are the ratio of open-circuit voltage to the temperature difference for the thermoelectric module, and the cold start voltage of the boost converter.

Excellent optoelectronic and thermoelectric properties of two-dimensional transition metal dinitride HfN2

Optoelectronic and thermoelectric properties of two-dimensional (2D) transition metal dinitride (HfN2) have been studied using first-principles calculations. Monolayer and bilayer HfN2 transport properties were calculated by solving the transport equations for electrons and phonons. The highest calculated ZT value for the bilayer HfN2 was 0.85 at 900 K in the negative chemical potential region. This high value of the figure of merit suggests that the material would be an excellent choice for thermoelectric energy harvesting devices. The optical property of the material suggests that it is a very good absorber in the ultraviolet (UV) region; thus, it can also be used as a UV-photodetector and as an absorber layer in photovoltaic devices.

Seebeck Analysis of ALD Synthesized Thermoelectric Sb2Te3 Thin Films

Thermoelectric materials have attracted significant attention due to their potential application in power generation and refrigeration systems, because they can convert thermal energy into electric energy from waste heat recovery. Thin thermoelectric films can be used to create thermoelectric generators, where the power they create does not result in any additional emissions. PbTe, PbSe and Sb2Te3, Bi2Te3 present excellent choices for thermoelectric energy harvesting devices. Among these, Sb2Te3 and its derivatives have high Seebeck coefficient and good electrical conductivity, which make these the most promising p-type material for low temperature thermoelectric device. The high figure of merit ZT values at relatively low temperature make these exceptional thermoelectric materials. This study investigates Seebeck coefficient measurements of Sb2Te3 thin film synthesized by Atomic Layer Deposition (ALD) technology using a Veeco Nanotech thermal ALD reactor. For the ALD synthesis of Sb2Te3 we used SbCl3 as precursor1 and (Si(CH3)3)2Te Bis(trimethylsilyl)telluride as precursor 2. Antimony trichloride Sb2Te3 is a solid ALD precursor requiring preheating to the melting temperature around 73 ℃ to generate sufficient vapor pressure. A typical film morphology of ALD Sb2Te3 is shown in the SEM micrograph of Fig.1. The efficiency of thermoelectric materials is expressed by the dimensionless thermoelectric figure of merit, ZT = S2σT/ k, where S is the Seebeck coefficient, σ is the electrical conductivity, and k is the thermal conductivity. Because the crucial Seebeck coefficient factors directly into the equation by the power of two to determine ZT and the power factor, it is imperative to optimize the thermoelectric thin film material for maximum Seebeck coefficient. Maximizing the figure of merit ZT is challenging because in thermoelectric materials the quantities S, σ and κ are interrelated in such a way as to make independent control of these variables to increase ZT not straightforward. An increase in S typically results in a decrease of σ. Following the Wiedeman- Franz law a decrease in σ produces a decrease in the electronic contribution to κ complicating matters. Figure 1

Doped Organic Micro‐Thermoelectric Coolers with Rapid Response Time

AbstractLocal thermal management has important implications regarding comfort, energy consumption, and electronic device performance/lifetime. While organic thermoelectrics have emerged as promising materials for flexible thermoelectric energy harvesting devices, their potential as Peltier cooling element has been largely overlooked. Here, micro‐thermoelectric coolers based on doped small molecule thin‐films with a fast response time (around 25 µs) which is among the fastest micro‐thermoelectric coolers reported are presented. This experimental cooling performance is supported by simulation using the finite‐element method for thermal transport. The results show that organic thermoelectrics offer great potential for flexible and wearable micro‐thermoelectric cooling applications.

Interface-Induced Seebeck Effect in PtSe2/PtSe2 van der Waals Homostructures.

The Seebeck effect refers to the production of an electric voltage when different temperatures are applied on a conductor, and the corresponding voltage-production efficiency is represented by the Seebeck coefficient. We report a Seebeck effect: thermal generation of driving voltage from the heat flowing in a thin PtSe2/PtSe2 van der Waals homostructure at the interface. We refer to the effect as the interface-induced Seebeck effect. By exploiting this effect by directly attaching multilayered PtSe2 over high-resistance PtSe2 thin films as a hybridized single structure, we obtained the highly challenging in-plane Seebeck coefficient of the PtSe2 films that exhibit extremely high resistances. This direct attachment further enhanced the in-plane thermal Seebeck coefficients of the PtSe2/PtSe2 van der Waals homostructure on sapphire substrates. Consequently, we successfully enhanced the in-plane Seebeck coefficients for the PtSe2 (10 nm)/PtSe2 (2 nm) homostructure approximately 42% compared to that of a pure PtSe2 (10 nm) layer at 300 K. These findings represent a significant achievement in understanding the interface-induced Seebeck effect and provide an effective strategy for promising large-area thermoelectric energy harvesting devices using two-dimensional transition metal dichalcogenide materials, which are ideal thermoelectric platforms with high figures of merit.

Multi-parameter optimization design of thermoelectric harvester based on phase change material for space generation

In this study, a thermoelectric energy harvesting device based on phase change material is presented which can be applied with large temperature variation in space for power supply. Aiming at multi-parameter optimization of thermoelectric harvester, an assessment of the generalized design rules for the proposed harvester has been implemented. The effect of thermal conductivity, melting temperature and mass of phase change material on the thermodynamic process were investigated to obtain the design criterion for thermoelectric harvester. Besides, both simulation and experiment validated that choosing PCM with a suitable melting temperature is quite essential to the temperature control by balancing the heat storage and release process, consequently enhancing the power output. This work offers a unique powering solution for wireless sensor involving location with temperature variation in space application.

A novel thermoelectric harvester based on high-performance phase change material for space application

In this study, a thermoelectric energy harvesting device applied with extremely large temperature variation (from +100 °C to −50°C) for space application is presented using phase change material (PCM) for thermal control and storage. Aiming at developing a high-performance PCM to fill into the heat storage unit (HSU) of the device, the thermal conductivity, leakage and thermal reliability of paraffin-based composites with different loadings of expanded graphite (EG) were investigated. Results showed the form-stable paraffin/EG composite has enhanced thermal conductivity and maintainable latent heat storage capacity after repeated thermal cycling test. Furthermore, the prototype device of thermoelectric harvester was developed, where the proportion of EG in the PCM is key to balance the heat storage capacity and the heat transfer rate. Both simulation and experiment are used to evaluate the performance of the harvester. The experimental evidence verifies that the thermoelectric harvester with paraffin/5 wt% EG composite owns the largest total energy output and the most portion of high-grade electrical energy.

β-Tantalum, a better candidate for spin-to-charge conversion

Abstract Development of thermoelectric energy harvesting devices has hit a stumbling block due to the intrinsically linked electrical and thermal conductivities of materials. However, this field can still be improved by employing devices that take advantage of spin-based effects. A temperature gradient can be converted to a spin-polarized current in a ferrimagnetic insulator by the spin Seebeck effect (SSE), and that spin current can be converted to an electrical voltage in a heavy metal by the Inverse spin Hall effect (ISHE). Thus, the thermal energy capture and charge production steps can be separated into two distinct regions of the thermoelectric device, allowing separate tuning of electrical and thermal conductivities. The second step of this process, spin current to electrical voltage conversion, is controlled by the strength and sign of ISHE in the metal, and platinum has become the standard for this purpose. However, here we report a better candidate, β-Tantalum, which shows a spin Seebeck voltage approximately 4 times higher than that of Pt at room temperature. The temperature dependence of spin Seebeck in YIG/β-Ta also closely follows that of YIG/Pt, consistent with magnon spin current theory. The sign of the spin Seebeck voltage in Ta found to be opposite to that of Pt, making the two materials highly complementary for fabricating spintronics-based thermoelectric modules for practical applications.

Fabrication and Characterization of Bi2Te3-Based Chip-Scale Thermoelectric Energy Harvesting Devices

Thermoelectric energy harvesters convert otherwise wasted heat into electrical energy. As a result, they have the potential to play a critical role in the autonomous wireless sensor network signal chain. In this paper, we present work carried out on the development of Bi2Te3-based thermoelectric chip-scale energy harvesting devices. Process flow, device demonstration and characterization are highlighted.

Metallic 1T phase MoS2 nanosheets for high-performance thermoelectric energy harvesting

Thermoelectric materials that can generate electricity from waste heat will play an important role in the global sustainable energy solution. Low dimensional materials open new routes to high performance thermoelectric properties due to their unique density of states with confined electrons and holes. Here, we report that the phase engineered two dimensional transition metal dichalcogenides represent a new class of high performance thermoelectric materials. The organolithium chemically exfoliated nanosheets of MoS2 containing a high concentration of metallic 1T phase MoS2 show superior thermoelectric properties, with a room temperature power factor of 73.1μWm−1K−2, which is much higher than the pristine graphene or single wall carbon nanotubes can yield. Our first principle calculations on monolayer 1T phase MoS2 provide physical insight of their metallic and hole conductive nature, which happens to be important origins of their advantageous thermoelectric properties. These metallic 1T phase MoS2 nanosheets also reveal interesting moisture sensitive thermoelectric properties, indicating their potential diverse applications not only as thermoelectric energy harvesting devices but also as self-powered gas sensors.

Performance evaluation of a thermoelectric energy harvesting device using various phase change materials

This paper compares the performance of a group of organic and inorganic phase change materials for a heat storage thermoelectric energy harvesting device. The device consists of thermoelectric generators and a closed container filled with a phase change material. One side of the generators is mounted on the aircraft fuselage and the other to the thermal mass. The group of inorganic and organic phase change materials was tested across two temperature ranges. These ranges are defined as "positive" and "negative", with the former being a sweep from +35°C to −5°C and the latter being a sweep from +5°C to −35°C. The performance in terms of electrical energy output and power produced is examined in detail for each group of materials.

A thermoelectric-based energy harvesting module with extended operational temperature range for powering autonomous wireless sensor nodes in aircraft

This paper describes the performance improvement of an energy harvesting device for aircraft by increasing its operational temperature range. The thermoelectric energy harvesting device consists of two cavities each containing a different phase change material, acting as thermal mass. Thermoelectric generator elements (TEGs) are attached to the inner part of the fuselage and to the thermal mass. Therefore, an artificially enhanced temperature difference between the bottom and the top surface of the TEGs is created during take-off and landing. Different temperature profiles mimicking short/mid-range European flights are investigated. The performance in terms of efficiency, power-to-weight ratio and energy harvested is studied in detail, both by simulations and experimental data.

Powering sea-ice instrumentation via the Seebeck Effect

Abstract This paper details the design of a novel thermoelectric energy harvesting device, capable of powering sea-ice instrumentation during the polar winter, when other sources of energy are either unavailable or unreliable. The current device employs no moving parts and exploits the Seebeck Effect and the temperature differential across the sea–ice interface to convert a flow of heat into electrical energy. Fundamental limitations are discussed and thermodynamic modelling is employed to ensure a reasonable device output. Test results from a prototype reveal typical voltage and power outputs in the region of 3 V and 200 mW, respectively, given an applied temperature differential of 30 °C.