Thermoelectric Generator Physics Investigatory Project PDF Class 12
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ABSTRACT
Nowadays the world has experiencing global warming due to excessive energy release into atmospheres. Today, a lot of research being conducted on ways to recover or reused the energy losses. An experimental investigation has been carried out to identify the most suitable cooling system techniques to achieve a stable and sustainable power output. Four types of Thermoelectric Module (TEM) was fitted and tested on different cooling system techniques. Testing was conducted using a candle flame as a heat source to produce a suitable temperature with the maximum temperature of 200°C. An electronic circuit is used to provide a constant and sufficient power. The use of suitable cooling system and Thermo Electric Module (TEM) was found by investigating the module parameters such as the temperature different of hot to cold side, number of thermo elements and internal resistance. This research contributes an important role in saving energy and reducing the dependency to primary energy sources (AC power or battery).
INTRODUCTION
It is essential for future generations to reduce the quantity of global energy consumed, and this can only be achieved through technological development and use of diversified renewable energy sources i.e. solar, wind, hydropower, in addition to the energy sources currently used. Among these different energy sources, thermoelectricity is currently emerging as a common and promising alternative energy source for the future. Their use is becoming of more interest, as they offer the advantages of recycling waste energy. This means transforming the heat from industry, or road transport into electricity, thus increasing system efficiency and decreasing operating costs and environmental pollution. Since the discovery of thermoelectricity (TE) in 1821 by Seebeck, researchers have been trying to understand and control this phenomenon. Peltier did exactly this in 1834 by discovering the opposite effect and Lord Calvin in 1851 formulated the laws that link these two phenomena. In the following century, in 1909, Edmund Altenkirch correctly calculated, for the first time, the energy efficiency of a thermoelectric generator now known as figure of merit.
THERMOELECTRIC MODULE
A typical TEG module consists of between ten and a hundred thermoelectric elements of type n and type p, electrically connected in series and thermally in parallel, and interposed between two ceramic layers, as shown in below Figure. The p-n pairs are joined by conductive tabs connected to the elements via a low melting point solder (PbSn or BiSn). When a temperature gradient occurs between its two junctions, the TEG converts thermal energy into electrical energy according to the principle of the Seebeck effect. This flat bulk architecture is the most widely used and marketed. The critical challenge in the development of TEGs is the degradation of original properties brought on by thermal fatigue, which is in turn caused by thermal expansion and thermal shock. This degradation can be brutal or progressive and result in a decrease in service life and efficiency. In fact, during normal operation of TE devices, the shunts are periodically heated and cooled and undergo thermal expansion. The TE materials connected to these shunts can experience different effects in expansion from temperature sources, which cause increased stress at the interface between them. These stresses are generally the main cause of mechanism failure and consequently the principal reason why TE materials are not sintered and integrated into shunts.
THERMOELECTRIC GENERATOR
The thermoelectric generator is a device, where electric energy is produced directly from heat energy. They are also called Seebeck generators since they used the Seebeck effect to produce power. In conventional power plants, like thermal power plants, nuclear power plants, fuel is used to heat the water. Generally, coal is burnt in that process. After the water starts boiling, and converted into steam, at high pressure, this steam is used to rotate the turbine and hence mechanical energy is converted into electric energy by Fleming’s law of electromagnetic induction. In this process, there is two-stage energy conversion, first heat energy is converted into mechanical energy and then mechanical energy is converted to electric energy. Because of this two-stage process, the efficiency of the overall system goes down. If we can directly convert heat energy to electrical energy, efficiency will be more. In the thermoelectric generator, heat energy is directly converted to electric energy, which has high economic benefits. Thermoelectric generators fundamentally use the thermoelectric principle of operation, which is based on the temperature gradient.
CONSTRUCTION
Constructional, it is made of up semiconductor materials to create the temperature gradient. The semiconductor materials used to form a thermocouple, which creates the temperature gradient and a potential difference is created. For this semiconductor device, both p-type and n-type materials are used. Metal alloys are formed using this semiconductor device. Metal alloys like Bi2Te3, Sb2Te3 are used to create the semiconductor path for the flow of charges.
WORKING PRINCIPLE
The thermoelectric generator working principle is, it works on the concept of thermoelectric effect or Seebeck effect. As per this effect, when a temperature gradient is produced between two ends, the electrons start flowing from one end to another end and create a potential difference. For the creation of the temperature gradient, thermocouple devices have to be used. Thermocouple devices are fundamentally semiconductor device which has high electrical conductivity and low thermal conductivity. For this, the properties of semiconductor devices are used.
They have generally four valence electrons in the outermost orbit. So they can be either p-type or n-type. In an n-type semiconductor, the majority of charge carriers are the electrons. They are also called donors. In p-type semiconductors, the majority of charge carriers are the holes. Holes are also called the absence of electrons. The p-type material is also called as acceptors. So when a p-type and n-type material are connected in a proper manner, and a temperature gradient is created, then it forms a potential difference across two points. Due to which the electrons start flowing from one end to another. This creates a thermoelectric generator. The thermoelectric generator temperature difference is created by this principle.
TYPES OF GENERATOR
The classification of thermoelectric generators depends on the method by which input heat is produced. Different types of thermoelectric generators are:
Fossil Fuel Generators:
In this type, the heat is generated by burning fossil fuels, the fossil fuels used for this purpose are natural gas, propane, butane, etc. Its range is from 10W to 100 W.
Solar Source Generators:
In this type, the heat is produced using solar energy.
Nuclear Fuelled Generators:
In this type, nuclear energy is used to input the heat. Its power rating is high as compared to other generators. It may go 1000 W.
ADVANTAGE AND DISADVANTAGE
The advantages of thermoelectric generators include the following:
- Economically friendly
- Recycles waste heat
- A reliable source of energy
- Lower production cost
The disadvantages of thermoelectric generators include the following:
- Low efficiency
- Limited applications
- Requires a constant source of heat
- Energy cannot be stored
APPLICATION
The applications of thermoelectric generators include the following:
- Electronics
- Space applications
- Renewable energy sources
- Gas pipelines
- Radio communication