Thermoelectricity represents a technology with immense potential, offering a tangible solution to convert wasted heat into a sustainable and renewable energy source. In a context where energy efficiency has become a global priority, the ability of thermoelectric materials to convert temperature differences into electricity opens new avenues for energy recovery across various industrial and domestic sectors. This transformation allows for the valorization of thermal flows previously considered as unavoidable losses, particularly in thermal engines, power plants, and heating networks. The constant development of materials with a high ZT merit factor reflects the remarkable progress made to optimize this thermal conversion while reducing production costs and minimizing environmental impact.
In 2025, research into thermoelectric materials reached a decisive turning point thanks to major innovations such as the compact “zero-vacuum gap” device developed within renowned institutions. This technology, by circumventing the limitations imposed by traditional thermal radiation laws, enables an increase in the density of electric power generated while operating at temperatures significantly lower than those required by conventional systems. Moreover, innovations are not limited to a single technique: the photovoltaic-thermoelectric coupling well illustrates this trend towards hybrid and more efficient systems capable of harnessing heat from renewable sources such as solar energy.
The applications of these materials also extend to the cooling sector, thanks to the Peltier effect, which allows for the production of robust, silent, and environmentally friendly systems. Thus, we are witnessing a diversification of uses, from electricity production from industrial waste heat to powering autonomous sensors and connected objects. In this context, thermoelectricity, based on the joint exploitation of properties such as the coefficient of performance and thermal conductivity, positions itself as an innovative pillar for the energy transition of the 21st century.
This scientific feat comes with significant technological and economic challenges, calling for rapid and controlled industrialization, aiming for seamless integration into existing infrastructures. The future of thermoelectric materials thus appears rich in promise, as they combine high performance, durability, and environmental compatibility.
In short :
- Conversion of wasted heat into clean electricity through thermoelectric materials.
- A major innovation: the “zero-vacuum gap” device that doubles power density without increasing temperature.
- Optimization of the ZT merit factor to enhance thermal conversion.
- Multiple applications: heavy industry, cooling systems, portable generators.
- Hybrid materials under development to combine photovoltaics and thermoelectricity.
- Significant industrial decarbonization prospects through thermal energy recovery.
The crucial role of thermoelectric materials in thermal energy recovery
Thermoelectric materials are at the heart of an energy revolution. Their main characteristic lies in the Seebeck effect, by which a temperature difference applied to two junctions generates an electric voltage. This capability is directly related to the electronic and phononic structure of the materials, which must exhibit an ideal combination of low thermal conductivity and high electrical conductivity.
The performance of these materials is measured by a key parameter: the thermoelectric merit factor, denoted ZT. This coefficient, defined by the relationship between electrical conductivity, thermal conductivity, and the Seebeck coefficient, determines the efficiency of thermal conversion into electricity. Achieving or exceeding a ZT greater than 3 is the sought-after goal to compete with conventional energy conversion technologies.
To achieve these performances, several families of materials are successfully used. Among them, bismuth telluride compounds (Bi2Te3) have long dominated the market, offering an acceptable compromise between efficiency and stability. However, the quest for greater energy efficiency in 2025 has propelled exploration toward complex compounds based on antimonides, giant silicon, or materials based on skutterudites. The latter allow for manipulating atomic arrangements in order to optimize phonon diffusion, promoting a strong Seebeck effect while limiting thermal losses.
For instance, a recent study conducted at a European research center has highlighted the potential of thermoelectric superlattices, where the assembly of microscopic layers on nanometric thicknesses encourages extremely low thermal conductivity, maximized for the Seebeck coefficient, thus achieving remarkably effective conversion.
This duality between high electrical conduction and low thermal conduction is critical as it maximizes thermal conversion, maximizing the amount of electricity generated for a given heat source. Moreover, this technology is wonderfully suited for industrial installations where wasted heat is substantial—foundries, cement plants, chemical production—allowing not only for energy recovery but also for reducing pollutant emissions by decreasing waste.
The choice of thermoelectric material also depends on usage conditions: temperatures, durability, corrosive environment or not, etc. In high-temperature applications, such as nuclear power plants, silicon-germanium alloys are favored for their stability. For lower temperatures, bismuth telluride remains a reference choice, often integrated into compact energy recovery devices.
This diversity makes thermoelectricity adaptable to a multitude of scenarios, demonstrating its central and essential role in the race to achieve energy optimization through the clean and silent conversion of wasted heat.
A major innovation: the thermophotovoltaic device with a “zero-vacuum gap”
A recent groundbreaking advancement in the field of thermoelectric devices has challenged preconceived notions. Led by a research team at the University of Colorado Boulder, this innovation consists of a compact thermophotovoltaic generator that exploits a novel concept called “zero-vacuum gap”. This technology capitalizes on a technological leap by circumventing the physical limitations of traditional devices related to Planck’s radiation law.
Known as TPV (thermophotovoltaic), these systems convert heat into electricity through a photovoltaic cell adapted to infrared radiations emitted by a hot source. However, between the thermal source and the cell, there is classically a vacuum or gas whose role is to prevent thermal conduction, but which also implies energy losses and thermodynamic constraints. The major novelty consists in inserting a high-refractive-index glass separator, transparent to infrared, thus eliminating the vacuum between the two faces.
This “zero-vacuum gap” multiplies the power per unit area by allowing for optimized thermal transfer without significant energy loss. The result: a power density doubled compared to classical TPVs, while operating at approximately 400 °C lower temperatures. This spectacular gain invites us to completely rethink thermal energy recovery.
The interest in this solution is not limited to its increased performance. The glass used is a low-cost material, industrially available in large quantities, which offers economic accessibility for the development of this technique. Furthermore, the simplicity of the design facilitates large-scale deployment, a crucial issue for the energy transition where multiplying energy recovery points is imperative.
To give a concrete idea, a prototype the size of a hand currently produces as much electricity as a traditional TPV system operating at 1,400 °C. This feature makes the technology easily integrable into both thermal power plants and industrial processes with moderate heat sources.
Improvement prospects remain vast. Other materials transparent to significant infrared bands, such as amorphous silicon, are being considered to further amplify the extracted electric power. This could multiply the power density by twenty, opening new doors to energy valorization.
This research, published in the journal Energy & Environmental Sciences, represents tangible proof that thermodynamic constraints are no longer an insurmountable barrier. It relies on a close collaboration between several prestigious institutions, promoting a multidisciplinary approach in the service of sustainable development.
The “zero-vacuum gap” device is a concrete response to the necessity of optimizing thermal conversion in a world where access to clean energy is becoming a global concern.
Concrete applications and industrial impact of thermoelectric materials
The integration of thermoelectric materials in industry fully aligns with a logic of decarbonization and energy efficiency. In the face of significant energy waste—where about two-thirds of consumed energy degrades in the form of wasted heat—the implementation of thermoelectric conversion systems proves crucial.
The applications primarily concern:
- Energy recovery in thermal engines of vehicles, allowing for direct powering of onboard electrical systems without overconsumption.
- Heavy industrial installations, such as steelmaking and cement plants, where residual heat is immense and constant.
- Geothermal and nuclear power plants that produce exploitable thermal flows to enhance electricity generation.
- The production of silent, efficient, and environmentally friendly thermoelectric cooling systems, addressing the thermal management challenges of electronic equipment.
Energy recovery in these areas not only improves the total efficiency of installations but also significantly reduces greenhouse gas emissions by harnessing a free and renewable energy source.
A comparative table of thermoelectric materials according to their typical properties illustrates this diversity:
| Material | Operating temperature range (°C) | ZT merit factor | Main advantages | Common applications |
|---|---|---|---|---|
| Bismuth Telluride (Bi2Te3) | 50 – 250 | 1 – 1.5 | Good electrical conductivity, stability at low temperature | Cooling, small electric generators |
| Silicon – Germanium (SiGe) | 600 – 1000 | 1 – 1.3 | Stability at high temperature | Space generators, nuclear power plants |
| Skutterudites | 300 – 700 | 1.5 – 2 | Low thermal conductivity, high efficiency | Heavy industry, energy recovery |
| Antimonides | 200 – 600 | 1.2 – 1.8 | Flexibility and adjustable performance | Varied industrial applications |
Industries now have tailored solutions for each thermal context, maximizing conversion potential while considering specific constraints. This technological maturity allows for the prospect of wide adoption in the coming years, facilitated by cost reduction and improvement in the coefficient of performance.
At the same time, research projects explore the combination of thermoelectricity with renewable energy sources, such as hybrid photovoltaic-thermoelectric systems, aimed at further increasing overall efficiency and powering autonomous devices. This technological convergence well illustrates the current transversality of innovations in sustainable energy, where every watt saved or generated extends the longevity of resources.
This dynamic is part of a global desire to adopt innovative solutions to meet energy and environmental challenges, demonstrating that thermoelectricity has become much more than just a scientific concept.
The scientific foundations: thermoelectric effects and key parameters of materials
Thermoelectricity is based on three fundamental effects that explain the conversion between heat and electricity: the Seebeck effect, the Peltier effect, and the Thomson effect. These interconnected phenomena define the behavior of thermoelectric materials and their potential for use.
Seebeck Effect: from temperature difference to electric voltage
When two different conductive materials are connected to form a junction, a temperature difference between these junctions generates an electric voltage. This is the basic principle used to convert heat into electricity. The magnitude of this voltage depends directly on the Seebeck coefficient, an intrinsic characteristic of the material.
Peltier Effect: reverse operation for cooling
By applying an electric voltage to the junctions of a thermoelectric material, it is possible to induce thermal transfer, generating a cooling effect at one end and heating at the other. This principle is exploited in silent refrigeration systems without moving parts, particularly valued in advanced electronics and medical applications.
Thomson Effect: thermal transfer in a conductor under current
Less known than the first two, the Thomson effect describes the heat transfer associated with the passage of an electric current through a conductor subjected to a temperature gradient. It influences the performance of thermoelectric devices by affecting their internal thermal balance.
These three effects, when combined, define the performance coefficient of thermoelectric materials and guide engineering efforts towards enhancing their properties. The ability to minimize thermal conductivity while maximizing electrical conductivity and the Seebeck coefficient is key to obtaining an efficient material.
Current research is also focused on nanostructuring and chemical modification of materials to control phonon and electronic transport at atomic scales, thus increasing the ZT merit factor. This fine control paves the way for high-performance, robust thermoelectric devices suited for a variety of energy and environmental applications.
Interactive infographic: Thermoelectric materials
Discover the key principles of thermoelectric effects and how these materials allow for the recovery of energy from wasted heat.
Seebeck Effect
Conversion of a temperature difference into electric voltage
Peltier Effect
Production of heat or cold at the junction of two conductors when a current passes
Thomson Effect
Absorption or release of heat when a current flows through a conductor with a temperature gradient
Click on one of the thermoelectric effects above to see more details.
Application example: thermal energy recovery on an exhaust pipe
The estimated thermoelectric energy recoverable will be displayed here.
Frequently Asked Questions about thermoelectric materials and energy recovery
What is the ZT merit factor and why is it important?
The ZT merit factor measures a thermoelectric material's efficiency in converting heat into electricity. It accounts for electrical conductivity, thermal conductivity, and the Seebeck coefficient. The higher the ZT, the better the energy conversion.
How do thermoelectric materials contribute to the reduction of greenhouse gas emissions?
By valuing residual heat that is often dissipated into the atmosphere, thermoelectric materials reduce dependency on fossil energy sources, thereby decreasing pollutant emissions and participating in the fight against climate change.
What are common applications of thermoelectric materials?
They are primarily used for energy recovery in industry, providing autonomous electricity for sensors, silent cooling systems, and in embedded devices where heat is abundant.
What is the difference between the Seebeck and Peltier effects?
The Seebeck effect converts a temperature difference into electricity, while the Peltier effect uses an electric current to induce thermal transfer, thus allowing for the cooling or heating of a system.
Are thermoelectric devices expensive to produce?
Costs have significantly decreased due to advancements in materials and manufacturing techniques. Innovations like the “zero-vacuum gap” device utilize low-cost materials, facilitating their industrial diffusion.