Measurement Of The Electric Energy Storage Capacity In Solar Thermoelectric Generators' Energy Harvesting Modules

Reducing energy consumption is mandatory in self-powered sensor nodes of wireless sensor networks that obtain all their energy from the environment. In this direction, one first step to optimize the network is to accurately measure the total energy harvested, which will determine the power available for sensor consumption. We present here a technique based on an embedded circuit with an ultra-low-power microcontroller to accurately measure the efficiency of flat-panel solar thermoelectric generators operating with environmental temperature gradients. Experimental tests showed that when a voltage of 180 mV (best case in an environmental flat-panel solar thermoelectric generators) is applied to the input of the DC-DC converter, the proposed technique eliminates a measurement error of 33% when compared with the conventional single supercapacitor strategy.13

Power generation from salinity gradient solar ponds using thermoelectric generators

The thermoelectric devices have been introduced for over 50 years and numerous research and methods have been carried out to improve its conversion efficiency, represented by the figure of merit, Despite having a low conversion efficiency compared to other heat engine, thermoelectric is gaining attention owing to its stationary and simplest operating condition that requires no maintenance. From the literature study conducted, most of the applications of the thermoelectric generators are focusing on generating electricity from a non-storage heat source, which means in order to avoid intermittency in the power supply due to temporary unavailability of adequate heat source; a battery storage system is needed. In order to address an alternative for the aforementioned scenario, a thermal storage system that will able to constantly providing sufficient heat for power generation is proposed, which introduces the solar pond (SP) as the heat source. Acting as a solar energy collector as well as thermal storage, solar ponds have been available in large scale for providing low grade heat source from 50 ºC to 100 ºC. Moreover, in terms of scalability, both thermoelectric generators and solar pond are highly scalable in size. As the thermoelectric cells are able to work interchangeably between heat pump and heat engine, it results in two variations of the thermoelectric cells available in the market, being sold as Peltier cooler and thermoelectric generators, with a significant price difference (the former is costing less than the latter). This study has started by investigating the performance and reliability of the thermoelectric cooler available functioning as thermoelectric generator. Later, in the next chapter, the performance of the thermoelectric cells is incorporated and coupled with a transient heat transfer for solar pond, in order to set up the potential of the thermoelectric-solar pond power generation system. Two practical power generation systems have been brought to fruition and presented in this thesis, which are a plate type power generation unit operating at atmospheric pressure and a submersible type thermoelectric power generation unit, and their comprehensive investigation have been delineated separately in the following chapters. Finally, the outcomes from the prior chapters (the system’s performance via transient model and prototype testing) are joined in the last part of this thesis, to form a sound feasibility study of the system. From the establishment of theoretical framework to the examination of the system's feasibility from the potential and practical viewpoint, this thesis had attended the essential of power generation from solar pond using thermoelectric generators

SUSTAINABLE ENERGY HARVESTING TECHNOLOGIES – PAST, PRESENT AND FUTURE

Chapter 8: Energy Harvesting Technologies: Thick-Film Piezoelectric Microgenerato

Low power energy harvesting and storage techniques from ambient human powered energy sources

Conventional electrochemical batteries power most of the portable and wireless electronic devices that are operated by electric power. In the past few years, electrochemical batteries and energy storage devices have improved significantly. However, this progress has not been able to keep up with the development of microprocessors, memory storage, and sensors of electronic applications. Battery weight, lifespan and reliability often limit the abilities and the range of such applications of battery powered devices. These conventional devices were designed to be powered with batteries as required, but did not allow scavenging of ambient energy as a power source. In contrast, development in wireless technology and other electronic components are constantly reducing the power and energy needed by many applications. If energy requirements of electronic components decline reasonably, then ambient energy scavenging and conversion could become a viable source of power for many applications. Ambient energy sources can be then considered and used to replace batteries in some electronic applications, to minimize product maintenance and operating cost. The potential ability to satisfy overall power and energy requirements of an application using ambient energy can eliminate some constraints related to conventional power supplies. Also power scavenging may enable electronic devices to be completely self-sustaining so that battery maintenance can eventually be eliminated. Furthermore, ambient energy scavenging could extend the performance and the lifetime of the MEMS (Micro electromechanical systems) and portable electronic devices. These possibilities show that it is important to examine the effectiveness of ambient energy as a source of power. Until recently, only little use has been made of ambient energy resources, especially for wireless networks and portable power devices. Recently, researchers have performed several studies in alternative energy sources that could provide small amounts of electricity to low-power electronic devices. These studies were focused to investigate and obtain power from different energy sources, such as vibration, light, sound, airflow, heat, waste mechanical energy and temperature variations. This research studied forms of ambient energy sources such as waste mechanical (rotational) energy from hydraulic door closers, and fitness exercise bicycles, and its conversion and storage into usable electrical energy. In both of these examples of applications, hydraulic door closers and fitness exercise bicycles, human presence is required. A person has to open the door in order for the hydraulic door closer mechanism to function. Fitness exercise bicycles need somebody to cycle the pedals to generate electricity (while burning calories.) Also vibrations, body motions, and compressions from human interactions were studied using small piezoelectric fiber composites which are capable of recovering waste mechanical energy and converting it to useful electrical energy. Based on ambient energy sources, electrical energy conversion and storage circuits were designed and tested for low power electronic applications. These sources were characterized according to energy harvesting (scavenging) methods, and power and energy density. At the end of the study, the ambient energy sources were matched with possible electronic applications as a viable energy source

Feasibility of a photovoltaic-thermoelectric generator: performance analysis and simulation results

This paper describes a theoretical approach to evaluate the performance of a hybrid solar system made with photovoltaic cells and thermoelectric (TE) modules. After a brief treatment of the integrated system, energy conversion and performance parameters are evaluated through numerical simulations depending on the global radiation and temperature distribution obtained by the Joint Research Center of the European Commission and of the National Renewable Energy Laboratory. The contribution of TE module to total energy seems significant in southern European towns and less substantial when the locations considered are very distant from the equator and show the possibility of using TE devices for energy production

A review of commercial energy harvesters for autonomous sensors

Current commercial autonomous sensors are mainly powered by primary batteries. Batteries need to be replaced and hence can become the largest and most expensive part of the system. On the other hand, our environment is full of waste and unused energy such as that coming from the sun or mechanical vibrations. As a result, commercial energy harvesters are increasingly available to power autonomous sensors. This work presents and analyses commercial energy harvesters currently available. First, environmental energy sources are classified and described. Then, energy harvesting principles are described and some guidelines are given to calculate the maximum power consumption allowed and the energy storage capacity required for the autonomous sensor. Finally, commercial energy harvesters are evaluated to determine their capability to power a commercial autonomous sensor in some given circumstances

Preparation and caracterization of thermoelectric materials

This work presents a complete study of thermoelectric materials. It starts with a study of a Solar Concentrator and the development of a Genetic Algorithm and Cross-Entropy for analyzing experimental data. Contains a study on thermoelectric devices, from a new experimental setup. It also counts on the development and manufacture of an entire equipment for measuring thermoelectric materials, both bulks and thin films. It ends with the preparation of a specific thermoelectric material, the MoS2, and the use of all the apparatus previously developed for its study

Advanced Thermoelectric Materials for Energy Harvesting Applications

Electrical energy consumption is negatively affecting our environment and contributing to climate change. Therefore the research and industrial communities are working hard to minimize energy consumption using promising energy-efficient and renewable energy technologies. We know that it is possible to convert heat energy into electrical energy using thermoelectric devices; this heat energy can be from the sun or from an electro-mechanical device. However, thermoelectric devices traditionally suffer from lower efficiencies of energy conversion. This book, Advanced Thermoelectric Materials for Energy Harvesting Applications, is a researchintensive textbook consisting of eight chapters organized into three sections. Section 1 consists of Chapters 2, 3, and 4, which cover advanced thermoelectric materials and the topics of organic/inorganic thermoelectric materials, quantum theory of the Seebeck coefficient for the advancement of thermoelectric superconducting material, and the limits of Bismuth Telluride-based thermoelectric materials. Section 2, containing Chapters 5 and 6, evaluates behaviors and performance of thermoelectric devices. Section 3, containing Chapters 7 and 8, focuses on energy harvesting applications of thermoelectric devices. This book will be of interest to a wide range of individuals, such as scientists, engineers, researchers, and undergraduate and postgraduate students in the field of advanced thermoelectric materials