Convert Waste Heat Research Articles

Experimental and Implementation of a 15 × 10 TEG Array of a Thermoelectric Power Generation System Using Two-Pass Flow of a Tap Water Pipeline Based on Renewable Energy

At the present time, the entire world is suffering from global climate change due to emissions caused by the combustion of fossil fuels. Thus, it is necessary to look for alternative power sources to generate clean electrical energy. Thermoelectric generators (TEG) are one of these alternatives. They convert thermal energy into useful electricity. There are many thermal energy sources such as hot water pipes. The current paper aims to convert waste heat from solar water-fed hot water pipes into electricity using a TEG panel made from 15 × 10 TEG modules. A pipe through which hot water flows serves as the hot side of the panel. The cold side of the panel is cooled using normal tap water. The maximum recorded temperature difference is 42.35 °C which yields an open-circuit voltage of 15.3 V. The maximum efficiency of the panel is 2.1% with an average energy production of 1.435 kWh. This proposed novel TEG panel system can be used continuously day and night. This is in contrast to a solar system, which operates only during the day, as it relies solely on solar radiation.

Advances in Thermo-Electrochemical (TEC) Cell Performances for Harvesting Low-Grade Heat Energy: A Review

Thermo-electrochemical cells (also known as thermocells, TECs) represent a promising technology for harvesting and exploiting low-grade waste heat (<100–150 °C) ubiquitous in the modern environment. Based on temperature-dependent redox reactions and ion diffusion, emerging liquid-state thermocells convert waste heat energy into electrical energy, generating power at low costs, with minimal material consumption and negligible carbon footprint. Recent developments in thermocell performances are reviewed in this article with specific focus on new redox couples, electrolyte optimisation towards enhancing power output and operating temperature regime and the use of carbon and other nanomaterials for producing electrodes with high surface area for increasing current density and device performance. The highest values of output power and cell potentials have been achieved for the redox ferri/ferrocyanide system and Co2+/3+, with great opportunities for further development in both aqueous and non-aqueous solvents. New thermoelectric applications in the field include wearable and portable electronic devices in the health and performance-monitoring sectors; using body heat as a continuous energy source, thermoelectrics are being employed for long-term, continuous powering of these devices. Energy storage in the form of micro supercapacitors and in lithium ion batteries is another emerging application. Current thermocells still face challenges of low power density, conversion efficiency and stability issues. For waste-heat conversion (WHC) to partially replace fossil fuels as an alternative energy source, power generation needs to be commercially viable and cost-effective. Achieving greater power density and operations at higher temperatures will require extensive research and significant developments in the field.

Review of the Nanostructuring and Doping Strategies for High-Performance ZnO Thermoelectric Materials

Unique properties of thermoelectric materials enable the conversion of waste heat to electrical energies. Among the reported materials, Zinc oxide (ZnO) gained attention due to its superior thermoelectric performance. In this review, we attempt to oversee the approaches to improve the thermoelectric properties of ZnO, where nanostructuring and doping methods will be assessed. The outcomes of the reviewed studies are analysed and benchmarked to obtain a preliminary understanding of the parameters involved in improving the thermoelectric properties of ZnO.

Multiple valence bands convergence and strong phonon scattering lead to high thermoelectric performance in p-type PbSe

Thermoelectric generators enable the conversion of waste heat to electricity, which is an effective way to alleviate the global energy crisis. However, the inefficiency of thermoelectric materials is the main obstacle for realizing their widespread applications and thus developing materials with high thermoelectric performance is urgent. Here we show that multiple valence bands and strong phonon scattering can be realized simultaneously in p-type PbSe through the incorporation of AgInSe2. The multiple valleys enable large weighted mobility, indicating enhanced electrical properties. Abundant nano-scale precipitates and dislocations result in strong phonon scattering and thus ultralow lattice thermal conductivity. Consequently, we achieve an exceptional ZT of ~ 1.9 at 873 K in p-type PbSe. This work demonstrates that a combination of band manipulation and microstructure engineering can be realized by tuning the composition, which is expected to be a general strategy for improving the thermoelectric performance in bulk materials.

Ba1/3CoO2: A Thermoelectric Oxide Showing a Reliable ZT of ∼0.55 at 600 °C in Air.

Thermoelectric energy conversion technology has attracted attention as an energy harvesting technology that converts waste heat into electricity by means of the Seebeck effect. Oxide-based thermoelectric materials that show a high figure of merit are promising because of their good chemical and thermal stability as well as their harmless nature compared to chalcogenide-based state-of-the-art thermoelectric materials. Although several high-ZT thermoelectric oxides (ZT > 1) have been reported thus far, the reliability is low due to a lack of careful observation of their stability at elevated temperatures. Here, we show a reliable high-ZT thermoelectric oxide, Ba1/3CoO2. We fabricated Ba1/3CoO2 epitaxial films by the reactive solid-phase epitaxy method (Na3/4CoO2) followed by ion exchange (Na+ → Ba2+) treatment and performed thermal annealing of the film at high temperatures and structural and electrical measurements. The crystal structure and electrical resistivity of the Ba1/3CoO2 epitaxial films were found to be maintained up to 600 °C. The power factor gradually increased to ∼1.2 mW m–1 K–2 and the thermal conductivity gradually decreased to ∼1.9 W m–1 K–1 with increasing temperature up to 600 °C. Consequently, the ZT reached ∼0.55 at 600 °C in air.

Comprehensive Insights into Synthesis, Structural Features, and Thermoelectric Properties of High-Performance Inorganic Chalcogenide Nanomaterials for Conversion of Waste Heat to Electricity

Comprehensive Insights into Synthesis, Structural Features, and Thermoelectric Properties of High-Performance Inorganic Chalcogenide Nanomaterials for Conversion of Waste Heat to Electricity

(Digital Presentation) Strategy to Enhance the Power Factor in Carbon Nanotubes

Flexible thermoelectrics, which can convert waste heat into electricity at surfaces with various shapes and moving parts, is one of important techniques for efficient use of our limited energy resources. Carbon nanotubes are one of possible candidates for flexible thermoelectrics, and then we have investigated the relationships between electronic structure, location of Fermi-energy level, morphology, and thermoelectric performance of the carbon nanotubes. Particularly, we have clarified the one-dimensional characteristics in thermoelectric properties of single walled carbon nanotubes (SWCNTs). In the case of metallic SWCNTs, the thermoelectric trade-off is violated when the Fermi-energy level is tuned around van hove-singularity [1]. Thus, simultaneous enhancement of Seebeck coefficient and electrical conductivity is possible in the metallic type. In the case of semiconducting SWCNTs, we theoretically clarified that it is very difficult to identify the 1D characters in the properties of their Seebeck coefficient, power factor, and electrical conductivity. We found it is necessary to clarify the relationships between thermoelectrical conductivity (L12 term) and electrical conductivity (σ) to discuss the dimensionality in thermoelectric properties of semiconducting nanomaterials. We observed clear peak structure in the L12-σ plot in high-purity (6,5) SWCNT thin films, reflecting the 1D traces in semiconducting SWCNTs[2]. Morphology control is also important to enhance power factor of carbon nanotubes. The Seebeck coefficient does not depend on the directions of heat flow and nanotube axis, but the electrical conductivity can be enhanced when the current direction is parallel to the nanotube axis [1, 3]. On the basis of above characteristics, we determined the following strategy to enhance the power factor (PF) of SWCNTs. Fine tuning of Fermi-energy level in the metallic type of nanotube can enhance PFAligned nanotubes with good electrical conductivity can enhance PF. Thus, we started to study the thermoelectric properties of carbon nanotube fibers with extremely good electrical conductivity, which are produced by Prof. Pasquali Group in Rice Univ [4]. As a result, we found the gigantic power factor of the nanotube fiber, which is 14 mWm-1K-2, with proper Fermi-level tuning [5]. Flexible thermoelectrics with such large PF will be useful for active cooling application.

Multi-objective optimization of pyroelectric thermal–electrical cycles

Pyroelectric thermal–electrical cycles enable a class of solid-state heat engines that convert waste heat to electrical energy. This article numerically investigates thermal-to-electrical energy conversion in a PbZr0.52Ti0.48O3 (PZT) pyroelectric layer near room temperature and optimizes operating parameters to maximize the electrical energy output. A general thermodynamic cycle is modeled after the prototypical pyroelectric Ericsson cycle—implemented based on the Ginzburg–Landau–Devonshire theory—with variable operating temperature range, and heating/cooling and charging/discharging time intervals. We used a Pareto optimization approach to simultaneously maximize electrical energy density and power density for different PZT sample and cycle parameters. The evaluated Pareto optimal fronts showcase the possibility of achieving multiple optimal solutions and highlight the trade-off between output energy density and power density in pyroelectric energy conversion. Specifically, we demonstrate that a 4× enhancement in power density is achievable with a less than 10% reduction in energy density for the same sample and operating conditions primarily by optimizing heat transfer. The multi-objective optimization approach and results presented in this study could provide a framework to facilitate the design and operation of pyroelectric cycles for waste heat energy harvesting systems.

Modeling of a Combined Kalina and Organic Rankine Cycle System for Waste Heat Recovery from Biogas Engine

Converting waste heat into electricity has captured the interest of scientists for years because of its enormous potential to improve energy efficiency and to lessen environmental impacts. While there are numerous applications to recover lost energy, they are often not efficient or cheap enough to make a real-world impact. The aim of this study is to develop a heat recovery system for the waste recycling factory operating in Hatay, Turkey. We combined the Kalina Cycle (KC) with the Organic Rankine Cycle (ORC) to extract exhaust gas and jacket water waste heat from a combined heat and power engine. An ammonia–water mixture was selected as the working fluid in KC, while R123, R236ea and R124 were chosen and tested for the ORC. The selection of working fluids was made based on certain environmental impacts such as global warming or ozone depletion potential, without further exploring other working fluid options, which could be considered a limitation of this study. The optimal values of KC parameters, including mass fraction, turbine inlet pressure and inlet temperature, were found to be 90%, 430 °C and 90 bar, respectively. The KC was then combined with the ORC using three different working fluids, among which R123 yielded the best results. The net power, exergy and thermal efficiency of the combined cycle were calculated as 211.03 kW, 52.83% and 26.50%, respectively, while the payback period was estimated to be 4.2 years. It should be noted that the applicability domain of the obtained results is limited to the climate conditions studied here. We concluded that the combination of the KC and ORC can be efficiently used for the recovery of waste heat energy.

An Experimental Study of the TEG Performance using Cooling Systems of Waterblock and Heatsink-Fan

Two third of the total energy in the internal combustion engine (ICE) system is lost and turns as waste heat through the exhaust system and coolant circulations. Therefore, it is necessary to have a technology that is able to convert waste heat from ICE into electrical energy using thermal electric generator (TEG). To have the best thermoelectric generator (TEG) performance in terms of higher electricity generation, the temperature on the hot surface should be higher, and the temperature on the cold surface should be as low as feasible. The goal of the study was to study how differences in TEG cooling systems affected the overall performance. Water block and heatsink-fan are two different types of cooling systems that have been used in this experiment. The water flow rate in water block cooling systems varies between 200, 300, 400, 500, and 600 l/h. The TEG module was heated with gas-fired lighters. Arduino-based data loggers were used to record hot and cold temperatures on the TEG surface. A USB multimeter is used to measure TEG performance as electrical voltage. The results showed that 300 l/h was the best water flow rate for TEG cooling. When using a water block cooling system instead of a heat sink, the electrical voltage generated by the TEG module is 12 percent higher. This study found that a cooling system with water blocks is superior to heatsink-fan.

Drop-in Replacement of Conventional Automotive Refrigeration System to Hybrid-Ejector System with Environment-Friendly Refrigerants

Ejector refrigeration system (ERS) is a propitious cooling skill for automobiles with a reduced fuel consumption along with structural simplicity, low cost, and driven by engine waste heat. Conversely, the lower coefficient of performance (COP) of standalone ERS is the major drawback for automotive applications, which can be overcome by hybridizing with a conventional compression system. Therefore, an indigenously designed hybrid cooling system is proposed to switch in three different cooling modes based on required thermal comfort— compressor, ejector, and hybrid. A real gas property-based theoretical model of this hybrid system is established under critical and sub-critical modes with a variable area ejector for a better entrainment ratio. In parallel, the performance of the proposed system is explored with two environment-friendly hydrofluorocarbon (HFC) refrigerants R152a, R440a and four extremely low global warming potential (GWP) hydrofluoroolefin (HFO) refrigerants R1234yf, R1243zf, R1234ze(E) and R513a, as an immediate replacement of commonly used R134a. The thermodynamic performance variation is compared for an extensive choice of the evaporator, generator, and condenser temperatures. Due to the conversion of waste heat into work in the hybrid mode, the compression ratio reduces maximum by 54% and cooling capacity increases by almost 22% more than in the conventional compressor mode. Moreover, compared with the standalone ejector system, the hybrid system improves the cooling capacity and COP by up to 4 times. Irrespective of the circumstances, the maximum entrainment ratio and COP are achieved with refrigerant R1234yf in hybrid mode, claiming ideal replacement of R134a for automotive air conditioning applications.

Enhancing thermoelectric properties in TiNiSi structure-type semimetal ZrNiSi by doping

The orthorhombic TiNiSi structure-type compounds show interesting electronic structures comprising in most cases a pseudogap in the density of states and several small electron and hole pockets at the Fermi energy. These features are promising and can be exploited to test their potential as thermoelectric materials for waste heat conversion. Here, we investigate the effect of electron doping in the semimetallic member $\mathrm{ZrNiSi}$ of this family. We show that by doping with Sb for Si in $\mathrm{ZrNiSi}, S$ and $\ensuremath{\sigma}$ can both be increased simultaneously for initial Sb doping defying the oppositely directed trend commonly observed in most materials. In the doped samples, $\ensuremath{\sigma}$ at $300\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ increases from $1000\phantom{\rule{0.28em}{0ex}}\mathrm{S}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ to as high as $2500\phantom{\rule{0.28em}{0ex}}\mathrm{S}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$; at the same time, the peak value of $S$, which is $\ensuremath{-}20\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{V}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ in $\mathrm{ZrNiSi}$, increases by more than a factor of two. The simultaneous enhancement of $\ensuremath{\sigma}$ and $S$ has been explained using the first-principles density functional theory based band structure calculations. The as-cast (i.e., unannealed) ${\mathrm{ZrNiSi}}_{1\ensuremath{-}x}{\mathrm{Sb}}_{x}$ samples show phase segregation due to a spinodal-type decomposition with two coexisting TiNiSi structure-type phases with different Sb/Si ratios. The thermal conductivity ($\ensuremath{\kappa}$) in the doped samples drops significantly from $12\phantom{\rule{0.28em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ ($x=0$) to nearly $2\phantom{\rule{0.28em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ ($x=0.2$) at 300 K. As a result, the peak thermoelectric figure of merit ($zT$) increases from 0.005 $(x=0)$ to 0.023 $(x=0.2)$. Further enhancement in $zT$ is obtained by codoping of Hf (Zr site) and Sb (Si site), which improves the phase stability and chemical homogeneity while keeping the thermal conductivity still very low due to Zr-Hf point mass fluctuation, resulting in a peak $zT$ value of 0.055, i.e., almost an order of magnitude higher value than for the pristine $\mathrm{ZrNiSi}$. We show that the thermoelectric properties of TiNiSi structure-type semimetals can be enhanced by aliovalent doping. This principle can be employed on other members of the TiNiSi to improve the $zT$ in this family of compounds further.

Experimental study on thermoelectric generation Device based on accumulated temperature waste heat of coal gangue

Coal gangue is industrial waste formed during coal production. Due to the accumulation of a large amount of heat inside, it is prone to spontaneous combustion. At present, the use of heat pipes to extract heat from coal gangue has become a relatively effective method, but the extracted heat has not been used rationally, causing damage to the natural environment. This paper proposes to use this part of thermal energy for thermoelectric conversion to realize thermoelectric generation, and on the basis of the experiment platform, and the factors that affect the maximum output power such as the arrangement mode, hierarchical structure and cold end heat dissipation mode of the thermoelectric module are studied. The paper also presents a thermoelectric conversion structure of “pipe in pipe”, which reduces heat loss, increases the contact area between the heat pipe and the thermoelectric generation sheet, and improves the energy conversion efficiency and reduces energy waste, thus the output power of thermoelectric conversion increases. The use of thermoelectric conversion to convert waste heat energy into electrical energy is of great significance to the secondary use of energy.

Methods Used to Enhance the Conversion Efficiency of Exhaust Based Thermoelectric Generator

Majority of the current thermal power generation technologies first convert thermal energy into mechanical energy before producing electricity. Thermoelectric Generation Technology therefore, is one of the budding conversion method, which can directly convert low-grade thermal energy into electrical energy by using thermoelectric compounds (materials). But energy generated by such a system is very low making it difficult for implementation.Therefore the focus of this study is to review the basic principle of thermoelectricity and it’s process to convert waste heat from exhaust of automobiles into electricity. Furthermore, the study delves into the methods to enhance the conversion efficiency of automotive exhaust thermoelectric generators.

Thermo-electrochemical redox flow cycle for continuous conversion of low-grade waste heat to power

Here we assess the route to convert low grade waste heat (< 100 °C) into electricity by leveraging the temperature dependency of redox potentials, similar to the Seebeck effect in semiconductor physics. We use fluid-based redox-active species, which can be easily heated and cooled using heat exchangers. By using a first principles approach, we designed a redox flow battery system with Fe(CN)63−/Fe(CN)64− and I−/I3− chemistry. We evaluate the continuous operation with one flow cell at high temperature and one at low temperature. We show that the most sensitive parameter, the temperature coefficient of the redox reaction, can be controlled via the redox chemistry, the reaction quotient and solvent additives, and we present the highest temperature coefficient for this RFB chemistry. A power density of 0.6 W/m2 and stable operation for 2 h are achieved experimentally. We predict high (close to Carnot) heat-to-power efficiencies if challenges in the heat recuperation and Ohmic resistance are overcome, and the temperature coefficient is further increased.

Effects of patterned electrode on near infrared light-triggered cesium tungsten bronze/poly(vinylidene)fluoride nanocomposite-based pyroelectric nanogenerator for energy harvesting

Pyroelectric nanogenerators (PyNG) are crucial to convert waste heat into electrical energy. In this study, we develop PyNG device with screen-printed serpentine electrode (SRE) and we modify with cesium tungsten bronze (Cs0.33WO3). We incorporate Cs0.33WO3 into both the electrode and poly(vinylidene)fluoride (PVDF) layers. We investigate effects of Cs0.33WO3 on pyroelectric response and photothermal conversion and electrode pattern effects on the pyroelectric properties. The electrode pattern remarkably improves pyroelectric response in which SRE pattern with width of 2 mm (Sample 2 (S2)) presents the highest electrical current and power. Moreover, the PVDF/Cs0.33WO3 PyNG device possesses outstanding photothermal conversion and pyroelectric response in comparison to PVDF-based PyNG device. Particularly, temperature of the device with 7 wt% Cs0.33WO3 reaches 121 °C and it shows electrical output responses of 4.36 V and 214 nA. It also generates a power density of 23.28 μW/m2 at a loading resistance of 20 MΩ. The electrical energy PyNG device generate power liquid crystal display (LCD) and four light-emitting diodes (LEDs). Our PyNG device presents better pyroelectric properties than that of PyNG device in open literature. This study represents an alternative to design and develop PyNG devices to harvest solar energy.

CoSb3 based thermoelectric elements pre-requisite for device fabrication

Conversion of waste heat into useful electrical energy employing thermoelectric (TE) technology can improve power generation. However, the synthesis of efficient TE elements is critically challenging in the fabrication of the TE device. In this work, p- and n-type TE elements (single leg) were synthesized by using CoSb3 skutterudites based optimized compositions (Fe0·25Co0·75Sb2·965Se0.035 and Ni0·07Co0·93Sb2·94Te0.06, respectively), and CoSi2 has been used as a contact material. The synthesis route of the TE elements is a combination of arc melting and spark plasma sintering, which is a short and cost-effective approach. Synthesized TE elements were characterized for the device performance parameters at different temperature gradients (ΔT), employing a TE conversion efficiency evaluation system (Mini-PEM). The maximum current ∼1.9 A and ∼1.4 A has been drawn, while the maximum output voltage ∼9.8 mV and ∼19 mV was attained by the p- and n-type TE elements, respectively. Finally, the output power has been evaluated, which was found to be ∼5.26 mW at ΔT∼ 471 °C for p-type TE element, and ∼6.79 mW at ΔT∼ 465 °C for n-type TE element.

Investigating the wet-to-dry expansion of organic fluids for power generation

The successful and economic conversion of waste heat into electricity requires new, innovative, power cycles to be developed. The proposed wet-to-dry cycle, in which the working fluid transitions across the saturation dome during expansion, has been shown to offer significant thermodynamic benefits. However, the feasibility of achieving wet-to-dry expansion when non-equilibrium effects, which are expected during a high-speed two-phase expansion, are taken into account has not been previously established. This paper first introduces a simple method to assess the thermodynamic potential of a fluid for the wet-to-dry cycle, which confirms that the siloxanes MM and MDM are excellent contenders and under ideal conditions can achieve second law efficiencies approaching 90% whilst operating with heat-source temperatures around 200 ∘C. The second part of this paper presents a one-dimensional nozzle design tool that accounts for thermal and mechanical non-equilibrium effects, which has been verified against previous studies and non-equilibrium computational-fluid dynamic simulations of the two-phase expansion of the refrigerant R1233zd(E). The model is then applied to the wet-to-dry expansion of MM under operating conditions directly relevant for the wet-to-dry cycle. The results firstly indicate the importance of accounting for non-equilibrium effects when designing nozzles for wet-to-dry expansion and the importance of having a realistic model that accounts for the break-up of droplets during the expansion. More importantly, the results reveal that for eight of the twelve cases considered it is still possible to achieve the full vapourisation of the working fluid within the nozzle when non-equilibrium effects are considered. This confirms the potential of the wet-to-dry cycle to enhance the performance of waste-heat recovery systems, which, in turn, necessitates further investigation, including experimental investigation, to further explore the concept.

The Effect of Clearance on Energy Dissipation for the Roots Power Machine Based on Low-Quality Energy Recovery

As a new type of waste heat conversion machine, the roots power machine can convert low-quality waste heat resources that are difficult to use into mechanical energy. In order to study the influence of tip clearance and radial clearance on the roots power machine, experimental studies were conducted with the roots power machine having different combination of tip and radial clearances and their influence on the performance of the roots power machine was examined. A parametric study was undertaken using CFD to find the sensitivity of these clearances in influencing the performance of roots power machine in the range of 0.2-0.5 mm. From the analysis, it was inferred that radial clearance was sensitive for clearance range of 0.25-0.5 mm and tip clearance in the range of 0.2-0.25 mm. Reduction in clearance from 0.5 mm to 0.2 mm caused an increase of 10.368 and 11.423 % in mechanical and volumetric efficiency respectively.

Valence Disproportionation of GeS in the PbS Matrix Forms Pb5Ge5S12 Inclusions with Conduction Band Alignment Leading to High n-Type Thermoelectric Performance.

Converting waste heat into useful electricity using solid-state thermoelectrics has a potential for enormous global energy savings. Lead chalcogenides are among the most prominent thermoelectric materials, whose performance decreases with an increase in chalcogen amounts (e.g., PbTe > PbSe > PbS). Herein, we demonstrate the simultaneous optimization of the electrical and thermal transport properties of PbS-based compounds by alloying with GeS. The addition of GeS triggers a complex cascade of beneficial events as follows: Ge2+ substitution in Pb2+ and discordant off-center behavior; formation of Pb5Ge5S12 as stable second-phase inclusions through valence disproportionation of Ge2+ to Ge0 and Ge4+. PbS and Pb5Ge5S12 exhibit good conduction band energy alignment that preserves the high electron mobility; the formation of Pb5Ge5S12 increases the electron carrier concentration by introducing S vacancies. Sb doping as the electron donor produces a large power factor and low lattice thermal conductivity (κlat) of ∼0.61 W m-1 K-1. The highest performance was obtained for the 14% GeS-alloyed samples, which exhibited an increased room-temperature electron mobility of ∼121 cm2 V-1 s-1 for 3 × 1019 cm-3 carrier density and a ZT of 1.32 at 923 K. This is ∼55% greater than the corresponding Sb-doped PbS sample and is one of the highest reported for the n-type PbS system. Moreover, the average ZT (ZTavg) of ∼0.76 from 400 to 923 K is the highest for PbS-based systems.