Wiktor Wise
Thermoelectric generators (TEGs) are solid-state devices that convert heat into electrical energy. They are also known as Seebeck generators, after Thomas Johann Seebeck, who discovered in 1821 that a thermal gradient between two different conductors can produce electricity. This phenomenon is now known as the Seebeck effect, a form of the thermoelectric effect. The amount of electricity produced by a TEG depends on the temperature difference between the hot and cold sides of the device, with greater differences resulting in more electrical power. For example, a temperature difference of 270 degrees Celsius can produce up to 21 watts of electrical power. TEGs have a range of applications, including powering portable communications transmitters and wearables that harvest energy from the human body.
| Characteristics | Values |
|---|---|
| What is a thermoelectric generator (TEG) | A solid-state device that converts heat into electrical energy |
| How does it work | A temperature gradient in a conducting material results in heat flow, which creates a voltage difference |
| Efficiency | A maximum of about 7.5% or 10% by the late 1980s; efficiency increases with a larger temperature difference |
| Power generated | A temperature difference of 10°C produces milliwatts per TEG, and a difference of 270°C can produce up to 21 watts of electrical power |
| Cooling method | Air cooling may be sufficient for 1-2 TEGs, but liquid cooling is more effective |
| Use cases | Power plants, factories, automobiles, space probes, portable communications transmitters |
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What You'll Learn
- Thermoelectric generators (TEGs) are solid-state devices that convert heat into electrical energy
- The greater the temperature difference, the more electrical power is produced
- TEGs are ideal for off-grid locations with a heat source
- TEGs are more expensive and less efficient than heat engines
- Silver selenide is a semiconductor with high electrical conductivity, making it ideal for thermoelectric applications
Thermoelectric generators (TEGs) are solid-state devices that convert heat into electrical energy
The amount of electricity generated by a TEG depends on the temperature difference between the hot and cold sides of the device. A greater temperature difference results in higher electrical power output. For instance, a temperature difference of 10°C can produce milliwatts, while a difference of 270°C can yield up to 21 watts of electrical power. The efficiency of this heat-to-electricity conversion can reach a maximum of about 7.5%. This means that for every 100 watts of heat passing through the TEG, a maximum of 7.5 watts of electricity will be produced.
TEGs can utilise a variety of heat sources, including furnaces, wood stoves, fireplaces, exhaust pipes, engines, solar collectors, and more. They are particularly useful in remote locations that are off the grid but have access to a heat source. The versatility of TEGs makes them a valuable source of power in various applications, such as powering space probes or increasing fuel efficiency in automobiles.
The efficiency of a TEG is influenced by its design geometry, with the arrangement of thermocouples (the basic components of a TEG) being planar, vertical, or mixed. Additionally, advancements in materials science have led to the development of novel processing techniques that improve the thermoelectric efficiency of TEGs. For example, a bismuth antimony tellurium ternary system can achieve a zT value of 1.86, surpassing the efficiency of current commercial TEGs.
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The greater the temperature difference, the more electrical power is produced
Thermoelectric generators (TEGs), also known as Seebeck devices, Peltier generators, or Seebeck generators, are solid-state devices that convert heat into electrical energy through the Seebeck effect, a type of thermoelectric effect. This phenomenon was discovered by Thomas Johann Seebeck in 1821 and revolves around the principle that a temperature gradient in a conducting material results in heat flow, leading to the diffusion of charge carriers and, consequently, the creation of a voltage difference.
The efficiency of a TEG is influenced by the design geometry, and it is crucial to select appropriate junctions and materials that can withstand mechanical and thermal conditions. The arrangement of thermocouples within the thermoelectric module can be planar, vertical, or mixed. A planar design, for instance, enables the creation of longer and thinner thermocouples, enhancing thermal resistance and the temperature gradient, ultimately resulting in increased voltage output.
The key factor impacting the electrical power generated by TEGs is the temperature difference between the hot and cold sides. This relationship is expressed as Delta T, which is calculated by subtracting the temperature of the cold side (Tcold) from the temperature of the hot side (Thot). As Delta T increases, so does the efficiency of the heat flow to electricity conversion. For example, a temperature difference of 10°C can yield milliwatts per TEG, while a substantial temperature difference of 270°C can produce approximately 21 watts of electrical power.
Maintaining a cool temperature on the cold side of the TEG is essential to optimize the temperature difference and, consequently, the electrical power output. While various cooling methods can be employed, liquid cooling is generally more effective than air cooling in achieving and sustaining the desired temperatures.
TEGs have a wide range of applications, particularly in remote locations with limited access to traditional power grids. They can utilize various heat sources, such as furnaces, wood stoves, fireplaces, engines, solar collectors, and more, to generate usable electrical power. Additionally, TEGs can be employed in power plants and factories to convert waste heat into supplementary electrical energy, enhancing overall energy efficiency.
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TEGs are ideal for off-grid locations with a heat source
Thermoelectric Generators (TEGs) are solid-state devices that convert heat into electrical energy through the Seebeck effect, a type of thermoelectric effect. TEGs have no moving parts and are designed to function across a wide range of temperatures and weather conditions. This makes them ideal for off-grid locations with a heat source, providing a reliable source of unattended power.
TEGs can utilise a variety of heat sources, including furnaces, wood stoves, fireplaces, solar collectors, and engines. The key requirement is the presence of a temperature difference between the hot side and the cold side of the TEG. This temperature differential drives the production of electrical power, with a larger difference resulting in greater power output. For example, a temperature difference of 270°C can produce up to 21 watts of electrical power.
The efficiency of a TEG is influenced by the geometry of its design. The arrangement of thermocouples within the device, for instance, can be planar, vertical, or mixed. Planar designs, which involve horizontally placed thermocouples, increase thermal resistance and temperature gradients, ultimately boosting voltage output. Additionally, advancements in processing techniques have led to improvements in the zT value, enhancing the overall efficiency of commercial TEGs.
TEGs are particularly advantageous in off-grid locations due to their ability to convert waste heat into usable power. They can be employed in power plants and factories to convert waste heat into additional electrical power. This not only reduces waste but also contributes to increased energy efficiency. Furthermore, TEGs can be integrated into multi-TEG modular solutions to provide higher power outputs, making them suitable for a range of applications, including hazardous locations and offshore platforms.
The versatility and reliability of TEGs make them a compelling option for off-grid locations, ensuring a consistent power supply regardless of external conditions. Their compatibility with renewable energy sources, such as solar power, further enhances their suitability for remote and environmentally conscious applications.
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TEGs are more expensive and less efficient than heat engines
Thermoelectric generators (TEGs) are solid-state devices that convert heat driven by temperature differences into electrical energy through the Seebeck effect, a form of the thermoelectric effect. They function similarly to heat engines but differ in that they are less bulky and have no moving parts. However, TEGs are generally more expensive and less efficient than heat engines.
The efficiency of a TEG is influenced by the geometry of its design, and extensive engineering is required to balance heat flow and maximise the temperature gradient. The junctions and materials used in TEGs must be carefully selected to withstand mechanical and thermal conditions, and the module design must ensure that the two thermoelectric materials are thermally in parallel but electrically in series. The arrangement of the thermocouples within the TEG can be planar, vertical, or mixed, each configuration offering distinct advantages in terms of thermal resistance, temperature gradient, and voltage output.
TEGs are well-suited for applications where bulkier and more efficient heat engines are impractical. They are often used for low-power remote applications, such as in space probes, where their lack of moving parts and high reliability make them ideal. TEGs can also be used in power plants and factories to convert waste heat into additional electrical power, and in automobiles to increase fuel efficiency.
Despite their advantages in certain contexts, TEGs are typically more expensive and less efficient than heat engines. Recent advancements in TEG materials have shown promise in improving efficiency. For example, bismuth telluride (Bi2Te3) has been found to offer higher conversion efficiency than other TEG materials, reaching a maximum of about 7.8% in energy conversion efficiency. Additionally, novel processing techniques that selectively reduce lattice thermal conductivity have been shown to improve the performance of commercial TEGs.
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Silver selenide is a semiconductor with high electrical conductivity, making it ideal for thermoelectric applications
Silver selenide (Ag2Se) is a semiconductor with high electrical conductivity, making it ideal for thermoelectric applications. It is one of the few thermoelectric materials that can be used at ambient temperatures, exhibiting relatively low thermal conductivity and high electrical conductivity. Silver selenide has a narrow band gap (Eg = 0.07 eV at 0 K) and exists in two stable phases: the low-temperature orthorhombic β-phase and the high-temperature cubic α-phase, with a transition temperature of around 407 K.
The thermoelectric properties of silver selenide have been studied using various techniques, including spark plasma sintering, ball-milling, microwave-assisted solution, and hot pressing. It has the highest electrical conductivity in bulk form, with values ranging from 2000 to 3000 S cm−1, while in thin films, the values are slightly lower, ranging from 750 to 1000 S cm−1. Silver selenide's Seebeck coefficient is also favourable, with values between −180 and −120 μV K−1 for thin films.
The development of new materials to replace traditional thermoelectric compounds is essential due to the scarcity and high toxicity of commonly used materials such as Bi2Te3 and PbTe. Silver selenide stands out as a promising alternative due to its high-power factor and low thermal conductivity. Its performance as an n-type semiconductor has attracted attention, and it is considered a viable option to replace toxic and expensive TE materials like Bi–Te alloys.
To optimize the thermoelectric performance of silver selenide, nanocrystalline Ag2Se is required. This presents challenges due to the energy-intensive and time-consuming nature of synthesizing Ag2Se nanoparticles, which often results in low yields. However, nanostructuring has proven valuable in adjusting the relationships between electrical conductivity, the Seebeck coefficient, and thermal conductivity. By employing nanocrystalline grains, for instance, it is possible to decouple the relationship between electrical and thermal conductivity.
In summary, silver selenide's high electrical conductivity, ambient temperature applicability, and favourable thermoelectric properties make it an ideal candidate for thermoelectric applications. Ongoing research focuses on enhancing its performance through nanostructuring and addressing the challenges associated with the synthesis of Ag2Se nanoparticles.
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Frequently asked questions
The amount of electricity generated depends on the temperature difference between the hot and cold sides of the device. A difference of 10 degrees Celsius will produce milliwatts per TEG, and a difference of 270 degrees Celsius can produce as much as 21 watts of electrical power. The typical efficiency of TEGs is around 5–8%, meaning you would need 17 kW to 20 kW of heat to produce 1 kW of electricity.
Thermoelectric devices, also known as Seebeck generators, convert heat into electrical energy through a phenomenon called the Seebeck effect, a form of the thermoelectric effect. A temperature gradient in a conducting material results in heat flow, which leads to the diffusion of charge carriers and the creation of a voltage difference. This voltage difference generates an electric current in a closed circuit.
Thermoelectric devices are solid-state devices that do not require any fluids for fuel or cooling, making them non-orientation dependent and suitable for use in zero-gravity or deep-sea applications. They can also be used in remote locations that are off the grid but have a heat source. Additionally, they function like heat engines but are less bulky and have no moving parts.
Yes, thermoelectric devices can be used for cooling by reversing the energy conversion process. This is known as a thermoelectric cooler or Peltier cooler. Electrical power is used to pump heat and produce refrigeration.
