3. Applications using thermoelectrics in the power generation mode

The favourable characteristics of the thermoelectric devices promote the development of standalone TEGs for energy harvesting in a wide range of applications (Figure 8) as military, aerospace (e.g., powering spacecraft), biological systems (e.g., to power implanted pacemakers) and other applications (e.g., power for wristwatches or mobile communications) [67]. The key element to improve the energy conversion efficiency of TEG is the effect of waste heat recovery. Waste heat represents the heat produced by machines (e.g., exhaust pipes from automobiles), industrial processes (e.g., cooling towers, burnt solid waste and radioactive wastes), electrical equipment (e.g., kerosene lamps) and the human body. For various TEG applications (e.g., waste thermal power recovery using TEGs and powering of

sulphuric acid and cadmium) that are not friendly for the human body. In this case, the body-attached TEGs could be an alternative solution because the materials used

A TEG to be applied in a network of body sensors has been presented in [78]. In this case, the device has been fixed in a body zone, where the maximum body heat has been obtained and also maximum energy. This equipment is capable of storing about 100 μW on the battery, leading to an output voltage of 2.4 V. Another TEG has been designed to be used on the wrist [79]. The output voltage of the device was

Thermal energy sensors (like heat-flux sensors, infrared sensors, power ultrasound effect sensors, fluid-flow sensors and water condensation detectors) are used

The heat-flux sensors are used to evaluate the thermoelectric properties of micro-TEGs. In this case, the generated power and the thermoelectric conversion efficiency are measured with high accuracy [80]. The electrical signal generated by the heat-flux sensor is proportional to the heat flow rate applied to the sensor surface. The convective heat flow rate is measured from the temperature difference between two sides of a thermal resistive element plate placed across the flow of heat. The heat radiated from the mass is absorbed by the infrared sensor (IR) and the temperature increase leads to the generation of the Seebeck voltage. The ther-

About 70% of energy in the world is wasted as heat and is released into the environment with a significant influence on global warming [81]. The waste heat energy released into the environment is one of the most significant sources of clean, fuel-free and cheap energy available. The unfavourable effects of global warming can be diminished using the TEG system by harvesting waste heat from residential,

TEG is substantially used to recover waste heat in different applications ranging from μW to MW. Different waste heat sources and temperature ranges for thermo-

The automotive industry is considered as the most attractive sector in which TEGs are used to recover the lost heat. Various leading automobile manufacturers develop TEGs (P � 1 kWÞ for waste recovery to reduce the costs of the fuel for their vehicles [82]. It has been demonstrated that vehicles (the gasoline vehicle and hybrid electric vehicles) have inefficient internal combustion engines. This can be observed in the Sankey diagram depicted in [83], which presents the energy flow direction of an internal combustion engine. The fuel combustion is used in a proportion of 25% for vehicle operation, 30% is lost into the coolant and 40% is lost as waste heat with exhaust gases. In this case, the TEG technology could be an option to recuperate the waste heat energy for gasoline vehicles and hybrid electric vehicles. A significant power conversion could be achieved by combining cooling system losses with the heat recovery from automobile exhausts. The use of TEG systems with an energy conversion of 5% would raise the electrical energy in a vehicle by 6% (5% from exhaust gases and 1% from the cooling system) [25].

150 mV under normal conditions and an electric output power of 0.3 nW.

Thermoelectric Energy Harvesting: Basic Principles and Applications

DOI: http://dx.doi.org/10.5772/intechopen.83495

to convert heat flow rates into electrical signals by a TEG system [36].

moelectric IR sensor operates in a range from 7 to 14 μm [69].

3.2 High-power generation for thermoelectric harvesting

electric energy harvesting are shown in Table 2 [69].

are non-toxic [36].

3.1.2 TEG as a thermal energy sensor

industrial and commercial fields [36].

3.2.1 Automotive applications

19

Figure 8. Energy conversion applications.

wireless sensors by TEGs) even if ΔT is restricted, the available heat is higher than the capacity of the harvesters. In this case, the heat source delivers a constant heat flow rate at a constant ΔT. Low η TEGmax in such applications does not mean low TEG performance [32].

#### 3.1 Low-power generation for thermoelectric harvesting

### 3.1.1 Microelectronic applications

The TEG devices are especially suitable for waste heat harvesting for low-power generation to supply electric energy for microelectronic applications. Wearable TEGs harvest heat generated by the body to generate electricity. For this reason, it is possible to use waste human body heat to power a TEG watch device. In this case, the wristwatch can capture the thermoelectric energy. Now, body-attached TEGs are commercially available products including watches operated by body temperature and thin film devices. Some manufacturers produce and commercialise wristwatches with an efficiency about 0.1% at 300 mV open circuit voltage from 1.5 K temperature drop and 22 μW of electric output power under of TEG normal operation. A thermo-clock wristwatch produces a voltage of 640 mV and gives a power of 13.8 μW for each °C of temperature difference. A wristwatch with 1040 thermoelements generates in the same conditions at about 200 mV [25]. The wearable TEG performance is affected by the utilisation of the free air convection cooling on the cold side of TEG, the low operating temperature difference between the body and environment, as well as the demand for systems that are thin and lightweight, being practical for long-term usage [68].

Furthermore, various microelectronic devices, like wireless sensor networks, mobile devices (e.g., mp3 player, smartphones and iPod), and biomedical devices are developed. The thermoelectric energy harvesters are microelectronic devices made of inorganic thermoelectric materials, at different dimensions, with a lifetime of about 5 years [69] and electric output powers are cardiac pacemakers (P ¼ 70÷100 μW) [70], pulse oximeter ð Þ P ¼ 100 μW [71], wireless communication ð Þ P � 3 mW [72], electrocardiography (ECG)/electroencephalography (EEG)/ electromyography (EMG) with P ¼ 60÷200 μW [73], EEG headband (P ¼ 2÷2:5 mW) [74], ECG system (P � 0:5 μWÞ [75], Hearing aid (P � 1 μWÞ [76] and Wireless EEG [77]. Together with the progress of flexible thermoelectric materials (both organic and inorganic materials), flexible TEGS system benefits from special attention. The flexible thermoelectric materials and maximum electric output power of various TEG systems are reported in [44].

For these microelectronic devices, standard batteries are used. These batteries are made of various inorganic materials (like nickel, zinc, lithium, lead, mercury, Thermoelectric Energy Harvesting: Basic Principles and Applications DOI: http://dx.doi.org/10.5772/intechopen.83495

sulphuric acid and cadmium) that are not friendly for the human body. In this case, the body-attached TEGs could be an alternative solution because the materials used are non-toxic [36].

A TEG to be applied in a network of body sensors has been presented in [78]. In this case, the device has been fixed in a body zone, where the maximum body heat has been obtained and also maximum energy. This equipment is capable of storing about 100 μW on the battery, leading to an output voltage of 2.4 V. Another TEG has been designed to be used on the wrist [79]. The output voltage of the device was 150 mV under normal conditions and an electric output power of 0.3 nW.

#### 3.1.2 TEG as a thermal energy sensor

wireless sensors by TEGs) even if ΔT is restricted, the available heat is higher than the capacity of the harvesters. In this case, the heat source delivers a constant heat flow rate at a constant ΔT. Low η TEGmax in such applications does not mean low

The TEG devices are especially suitable for waste heat harvesting for low-power

generation to supply electric energy for microelectronic applications. Wearable TEGs harvest heat generated by the body to generate electricity. For this reason, it is possible to use waste human body heat to power a TEG watch device. In this case, the wristwatch can capture the thermoelectric energy. Now, body-attached TEGs are commercially available products including watches operated by body temperature and thin film devices. Some manufacturers produce and commercialise wristwatches with an efficiency about 0.1% at 300 mV open circuit voltage from 1.5 K temperature drop and 22 μW of electric output power under of TEG normal operation. A thermo-clock wristwatch produces a voltage of 640 mV and gives a power of 13.8 μW for each °C of temperature difference. A wristwatch with 1040 thermoelements generates in the same conditions at about 200 mV [25]. The wearable TEG performance is affected by the utilisation of the free air convection cooling on the cold side of TEG, the low operating temperature difference between the body and environment, as well as the demand for systems that are thin and lightweight, being

Furthermore, various microelectronic devices, like wireless sensor networks, mobile devices (e.g., mp3 player, smartphones and iPod), and biomedical devices are developed. The thermoelectric energy harvesters are microelectronic devices made of inorganic thermoelectric materials, at different dimensions, with a lifetime

(P ¼ 70÷100 μW) [70], pulse oximeter ð Þ P ¼ 100 μW [71], wireless communication ð Þ P � 3 mW [72], electrocardiography (ECG)/electroencephalography (EEG)/

(P ¼ 2÷2:5 mW) [74], ECG system (P � 0:5 μWÞ [75], Hearing aid (P � 1 μWÞ [76] and Wireless EEG [77]. Together with the progress of flexible thermoelectric materials (both organic and inorganic materials), flexible TEGS system benefits from special attention. The flexible thermoelectric materials and maximum electric out-

For these microelectronic devices, standard batteries are used. These batteries are made of various inorganic materials (like nickel, zinc, lithium, lead, mercury,

of about 5 years [69] and electric output powers are cardiac pacemakers

electromyography (EMG) with P ¼ 60÷200 μW [73], EEG headband

put power of various TEG systems are reported in [44].

3.1 Low-power generation for thermoelectric harvesting

TEG performance [32].

Energy conversion applications.

Green Energy Advances

Figure 8.

3.1.1 Microelectronic applications

practical for long-term usage [68].

18

Thermal energy sensors (like heat-flux sensors, infrared sensors, power ultrasound effect sensors, fluid-flow sensors and water condensation detectors) are used to convert heat flow rates into electrical signals by a TEG system [36].

The heat-flux sensors are used to evaluate the thermoelectric properties of micro-TEGs. In this case, the generated power and the thermoelectric conversion efficiency are measured with high accuracy [80]. The electrical signal generated by the heat-flux sensor is proportional to the heat flow rate applied to the sensor surface. The convective heat flow rate is measured from the temperature difference between two sides of a thermal resistive element plate placed across the flow of heat. The heat radiated from the mass is absorbed by the infrared sensor (IR) and the temperature increase leads to the generation of the Seebeck voltage. The thermoelectric IR sensor operates in a range from 7 to 14 μm [69].

#### 3.2 High-power generation for thermoelectric harvesting

About 70% of energy in the world is wasted as heat and is released into the environment with a significant influence on global warming [81]. The waste heat energy released into the environment is one of the most significant sources of clean, fuel-free and cheap energy available. The unfavourable effects of global warming can be diminished using the TEG system by harvesting waste heat from residential, industrial and commercial fields [36].

TEG is substantially used to recover waste heat in different applications ranging from μW to MW. Different waste heat sources and temperature ranges for thermoelectric energy harvesting are shown in Table 2 [69].

#### 3.2.1 Automotive applications

The automotive industry is considered as the most attractive sector in which TEGs are used to recover the lost heat. Various leading automobile manufacturers develop TEGs (P � 1 kWÞ for waste recovery to reduce the costs of the fuel for their vehicles [82]. It has been demonstrated that vehicles (the gasoline vehicle and hybrid electric vehicles) have inefficient internal combustion engines. This can be observed in the Sankey diagram depicted in [83], which presents the energy flow direction of an internal combustion engine. The fuel combustion is used in a proportion of 25% for vehicle operation, 30% is lost into the coolant and 40% is lost as waste heat with exhaust gases. In this case, the TEG technology could be an option to recuperate the waste heat energy for gasoline vehicles and hybrid electric vehicles. A significant power conversion could be achieved by combining cooling system losses with the heat recovery from automobile exhausts. The use of TEG systems with an energy conversion of 5% would raise the electrical energy in a vehicle by 6% (5% from exhaust gases and 1% from the cooling system) [25].


experimental results showed good performance of the system at high speeds. Hsiao et al. [87] carried out an analytical and experimental assessment of the waste heat recovery system from an automobile engine. The results showed better performance by attaching TEGs to the exhaust pipe than to the radiators. Hsu et al. [88] introduced a heat exchanger with 8 TEGs and 8 air-cooled heat sink assemblies, obtaining a maximum power of 44 W. An application to recover waste heat has been developed by Hsu et al. [89], for a system consisting of 24 TEGs used to convert heat from the exhaust pipe of a vehicle to electrical energy. The results show a temperature increase at the hot side T<sup>h</sup> from 323 to 403 K and a load resistance of 23–30 Ω to harvest the waste heat for the system. Tian et al. [90] theoretically analysed the performance between a segmented TEG (Bi2Te3 used in low-temperature region and Skutterudite in high-temperature areas) used to recover exhaust waste heat from a diesel engine and traditional TEG. They found that a segmented TEG is suitable for large temperature difference and a hightemperature heat source, and has a higher potential for waste heat recovery compared to the traditional device. Meng et al. [91] addressed the automobile performance when applying TEG in exhaust waste heat recovery. The results showed that the effects of the different properties and the heat loss to the environmental gas on

Thermoelectric Energy Harvesting: Basic Principles and Applications

DOI: http://dx.doi.org/10.5772/intechopen.83495

The conversion efficiency for the TEG system could be in the range of 5–10% [83]. The researchers' attention is focused on the development of new thermoelectric materials that offer improved energy conversion efficiency and a working temperature range more significant than for internal combustion engines. It is planned by 2020, about 90% of cars in the USA to have mounted TEGs for their cooling equipment, thus replacing the air conditioning systems. In this case, an amount of 5% of daily average gasoline consumption would be saved and a signifi-

To recover waste heat from the exhaust gas of engines, the research efforts of manufacturers focused on different solutions to compete in the production of evercleaner cars. Even if the cost of the bismuth telluride is relatively high, the technical feasibility of TEGs for the automobile industry is widely demonstrated, making it very attractive. The goal of the manufacturers is to develop TEG systems with

A considerable amount of heat is released into the atmosphere from space vehicles (turbine engines from helicopters and aircraft jet engines) [29]. To obtain a significant reduction of the gas pollutant into the environment, it is necessary a remarkable reduction of electricity consumption and utilisation of the available energy in these types of vehicles. Implicitly, their operating costs are reduced [25]. To power these space vehicles, TEG systems are used (e.g., on fixed-wing aircraft). The backup TEG is a type of static thermoelectric energy harvesting system with a significant temperature difference across the TEG around 100°C [92].

TEG for energy harvesting uses the available temperature gradient and collects sufficient energy to power up an energy wireless sensor node (WSN) to be autonomous. This WSN is used for health monitoring systems (HMS) in an aircraft structure. The main components of a WSN are the energy source and the wireless sensor unit. An in-depth review of WSN mechanisms and applications is presented in [10]. A TEG energy harvesting captures enough energy for a wireless sensor. One side

of the TEG is fixed directly to the fuselage and the other side is attached to a

cant reduction of greenhouse gas emissions would be obtained [25].

automated production and low-cost thermoelectric materials [29].

performance are considerable.

3.2.2 Air applications

21

3.2.2.1 Space vehicle applications

#### Table 2.

Different waste heat sources and temperature ranges for thermoelectric harvesting technology.

A TEG with ZT ¼ 1:25 and efficiency of 10%, can recover about 35–40% of the power from the exhaust gas where the power generated can help to increase the efficiency to up 16% [84]. The components where TEGs could be attached in a vehicle are the exhaust system and the radiators. In this case, the amount of waste heat is decreased and exhaust temperatures are reduced. These aspects require more efficiency from the TEG device. Furthermore, the design of such power conversion system takes into account various heat exchangers mounted on the TEG device. These systems have a lifecycle from 10 to 30 years and the materials accumulated on their surfaces from the exhaust gas, air or coolant represent a major concern in order to not damage their proper operation [85]. Important testing is helpful to confirm the reliability of TEG systems in automotive applications. Furthermore, the design requires knowing the maximum electric output power and conversion efficiency from TEG systems [37].

The main components of the automotive TEG that considers waste heat like their energy source are one heat exchanger which takes heat from engine coolant and the exhaust gases and release it to the hot side of the TEG; the TEG system; one heat exchanger which takes the heat from the TEG and releases it to the coolant or to the air; the electrical power conditioning and the interface unit to supply the electric output power of the TEG system to the automobile electric system (Figure 9). Supplementary at these components, there are secondary components (e.g., the electronic unit, the electric pump, sensors system, valves, fans and so on) depending on the vehicle design and application type [85].

Thacher et al. [86] carried out the feasibility of the TEG system installed in the exhaust pipe in a light truck by connecting a series of 16 TEG modules. The

Figure 9. The main components of an automotive TEG system.

#### Thermoelectric Energy Harvesting: Basic Principles and Applications DOI: http://dx.doi.org/10.5772/intechopen.83495

experimental results showed good performance of the system at high speeds. Hsiao et al. [87] carried out an analytical and experimental assessment of the waste heat recovery system from an automobile engine. The results showed better performance by attaching TEGs to the exhaust pipe than to the radiators. Hsu et al. [88] introduced a heat exchanger with 8 TEGs and 8 air-cooled heat sink assemblies, obtaining a maximum power of 44 W. An application to recover waste heat has been developed by Hsu et al. [89], for a system consisting of 24 TEGs used to convert heat from the exhaust pipe of a vehicle to electrical energy. The results show a temperature increase at the hot side T<sup>h</sup> from 323 to 403 K and a load resistance of 23–30 Ω to harvest the waste heat for the system. Tian et al. [90] theoretically analysed the performance between a segmented TEG (Bi2Te3 used in low-temperature region and Skutterudite in high-temperature areas) used to recover exhaust waste heat from a diesel engine and traditional TEG. They found that a segmented TEG is suitable for large temperature difference and a hightemperature heat source, and has a higher potential for waste heat recovery compared to the traditional device. Meng et al. [91] addressed the automobile performance when applying TEG in exhaust waste heat recovery. The results showed that the effects of the different properties and the heat loss to the environmental gas on performance are considerable.

The conversion efficiency for the TEG system could be in the range of 5–10% [83]. The researchers' attention is focused on the development of new thermoelectric materials that offer improved energy conversion efficiency and a working temperature range more significant than for internal combustion engines. It is planned by 2020, about 90% of cars in the USA to have mounted TEGs for their cooling equipment, thus replacing the air conditioning systems. In this case, an amount of 5% of daily average gasoline consumption would be saved and a significant reduction of greenhouse gas emissions would be obtained [25].

To recover waste heat from the exhaust gas of engines, the research efforts of manufacturers focused on different solutions to compete in the production of evercleaner cars. Even if the cost of the bismuth telluride is relatively high, the technical feasibility of TEGs for the automobile industry is widely demonstrated, making it very attractive. The goal of the manufacturers is to develop TEG systems with automated production and low-cost thermoelectric materials [29].

#### 3.2.2 Air applications

A TEG with ZT ¼ 1:25 and efficiency of 10%, can recover about 35–40% of the power from the exhaust gas where the power generated can help to increase the efficiency to up 16% [84]. The components where TEGs could be attached in a vehicle are the exhaust system and the radiators. In this case, the amount of waste heat is decreased and exhaust temperatures are reduced. These aspects require more efficiency from the TEG device. Furthermore, the design of such power conversion system takes into account various heat exchangers mounted on the TEG device. These systems have a lifecycle from 10 to 30 years and the materials accumulated on their surfaces from the exhaust gas, air or coolant represent a major concern in order to not damage their proper operation [85]. Important testing is helpful to confirm the reliability of TEG systems in automotive applications. Furthermore, the design requires knowing the maximum electric output power and conversion effi-

Temperature ranges, °C Temperature, °C Waste heat sources

760–815 760–110 620–730

425–650 425–650

> 27–50 27–88

Different waste heat sources and temperature ranges for thermoelectric harvesting technology.

Aluminium refining furnaces Copper reverberatory furnace Copper refining furnace Cement kiln Hydrogen plants

Reciprocating engine exhausts Catalytic crackers Annealing furnace cooling systems

> Cooling water Air compressors Forming Dies and pumps

High temperature (>650°C) 650–760

Medium temperature (230–650°C) 315–600

Low temperature (230–650°C) 32–55

The main components of the automotive TEG that considers waste heat like their energy source are one heat exchanger which takes heat from engine coolant and the exhaust gases and release it to the hot side of the TEG; the TEG system; one heat exchanger which takes the heat from the TEG and releases it to the coolant or to the air; the electrical power conditioning and the interface unit to supply the electric output power of the TEG system to the automobile electric system

(Figure 9). Supplementary at these components, there are secondary components (e.g., the electronic unit, the electric pump, sensors system, valves, fans and so on)

exhaust pipe in a light truck by connecting a series of 16 TEG modules. The

Thacher et al. [86] carried out the feasibility of the TEG system installed in the

depending on the vehicle design and application type [85].

ciency from TEG systems [37].

Table 2.

Green Energy Advances

Figure 9.

20

The main components of an automotive TEG system.

#### 3.2.2.1 Space vehicle applications

A considerable amount of heat is released into the atmosphere from space vehicles (turbine engines from helicopters and aircraft jet engines) [29]. To obtain a significant reduction of the gas pollutant into the environment, it is necessary a remarkable reduction of electricity consumption and utilisation of the available energy in these types of vehicles. Implicitly, their operating costs are reduced [25].

To power these space vehicles, TEG systems are used (e.g., on fixed-wing aircraft). The backup TEG is a type of static thermoelectric energy harvesting system with a significant temperature difference across the TEG around 100°C [92].

TEG for energy harvesting uses the available temperature gradient and collects sufficient energy to power up an energy wireless sensor node (WSN) to be autonomous. This WSN is used for health monitoring systems (HMS) in an aircraft structure. The main components of a WSN are the energy source and the wireless sensor unit. An in-depth review of WSN mechanisms and applications is presented in [10].

A TEG energy harvesting captures enough energy for a wireless sensor. One side of the TEG is fixed directly to the fuselage and the other side is attached to a

phase-change material (PCM) heat storage unit to obtain a temperature difference during take-off and landing (Figure 10). PCM is considered an essential element for the heat storage unit because it can maximise the ΔT of the TEG system to solve the low TEG conversion efficiency [93]. In this case, the electrical energy is generated [94]. Water is an adequate PCM for heat storage. The temperature difference across the TEG is obtained from the slow changing temperature of the heat storage unit and the rapidly changing temperature of the aircraft fuselage. A lot of energy is produced during the PC, through latent heat [95, 96].

The heat sources on the marine vessels are the main engine, lubrication oil cooler, an electrical generating unit, generator and incinerators. The utilisation of waste heat onboard is for heating heavy fuel oil and accommodation places, and for freshwater production. The main engine represents the principal source of waste heat. Board incinerators are used for burning the onboard waste instead to be thrown overboard to pollute the sea water. The incinerators are the most favourable

The specialists' attention is focused on the future design and optimisation of the high-power density TEGs for the marine environment, as well as on the development of hybrid thermoelectric ships considered as green platforms for assessing the

The industry is the field where most amounts of heat are emitted and released

Utilisation of TEGs in the industrial field is beneficial from two points of view:

• in the industrial applications where the use of thermoelectric materials reduces the need for maintenance of the systems and the price of the electric power is

• in the industrial applications where recoverability of the waste heat by the conventional system (radiated heat energy) is very difficult to be done;

The results of a test carried out on a TEG system attached at a carburising furnace (made of 16 Bi2Te3 modules and a heat exchanger) are indicated in [104]. The system harvested about 20% of the heat (P = 4 kW). The maximum electrical output power generated by TEG has been approximately 214 W, leading to thermoelectric conversion efficiency 5%. Aranguren et al. [105] built a TEG prototype. The TEG has been attached at the exhaust of a combustion chamber, with 48 modules connected in series and two different kinds of finned heat sinks, heat exchangers and heat pipes. This TEG was used to recover waste heat from the combustion chamber. In this case, the main objective has been to maximise the

For this reason, the dissipation systems have been used on both sides of TEG. This prototype has obtained a 21.56 W of net power using about 100 W/m<sup>2</sup> from the exhaust gases of the combustion chamber. To recover the radiant heat from melted metal from the steelmaking industry, the TEG systems are also considered good

Furthermore, TEGs are useful for recovery of waste heat from the cement rotary kiln to generate electricity, considering that the rotary kiln is the main equipment used for large-scale industrial cement production [106]. The performance of this hybrid Bi2Te3 and PbTe thermoelectric heat recovery system is obtained by developing a mathematical model. In this case, about 211 kW electrical output power and 3283 kW heat loss are saved by using a thermoelectric waste heat energy recovery

into the atmosphere in the form of flue gases and radiant heat energy with a negative impact to the environmental pollution (emissions of CO2). For this reason, thermoelectric harvesters are good candidates to recover waste heat from industries and convert it into useful power (e.g., to supply small sensing electronic device in a

TEG systems due to the availability of their high-temperature differences

Thermoelectric Energy Harvesting: Basic Principles and Applications

DOI: http://dx.doi.org/10.5772/intechopen.83495

[101, 102].

plant).

efficiency of TEGs [103].

3.2.4 Industrial applications

low, even if the efficiency is low [29].

electric output power generated by the TEG.

system. The contribution of TEG is about 2%.

candidates [29].

23

An application of Bi2Te3 modules on turbine nozzles has been addressed in [97]. Even though the electric power that can be harvested may be significant, the weight of the cold exchanger is still excessive for the specific application.

Future applications in aircraft may be envisioned in locations in which there are hot and cold heat flows, especially with the use of light thermoelectric materials. However, one of the main issues remains the weight of the heat exchangers [29].
