SYSTEM INTEGRATION
Technology essentially based on radio-frequency identification (RFID).The RF Receiver and power harvester receives RF energy emitted from mobile phone towers and television transmission stations and convert it to electrical energy using RFID tags. Since this power is very feeble it is fed to a power management circuitry which performs voltage rectification and amplification and this electrical energy is stored in a storage capacitor.
The amount of energy that can be scavenged from the environment from machinery vibration is limited. Care must be taken in optimizing the generation and utilization of available power. A power budget is managed in the design and operation of the selfpowered sensor node. The approach often taken is to optimize each component. However, due to the coupling that exists among the elements, optimization of individual components will likely result in a suboptimal system design. A series of analytical laboratory studies were conducted to determine the power consumption characteristics of Sensor (accelerometer) Oil purifier Energy Converter Energy Storage(Capacitor bank) Power Conversion and Control Radio Circuit (802.15.4) Processor Energy Harvesting (piezo-electric cantilever beam) Energy Harvesting Module Power Bus Memory Environment the system elements. An FFT algorithm was implemented in a wireless sensor node as a representative calculation for machinery health assessment. While the percent of time is spent transmitting data is typically very small, the power requirements are significant (Figure 3). Power utilization in the self-powered sensor node may be optimized by judiciously balancing the amount of processing done locally in the sensor node with the amount of data that will be sent to a central processor for subsequent processing and analysis. The implication of this decision and the uncertainties in future processing demand and communications requirement provide the parameters for a dynamic optimization problem. The experimental results from the shipboard experiment provide realistic data to begin framing this optimization problem.
Scope of Energy Harvesting
Scope of Energy Harvesting
Advanced technical developments have increased the efficiency of devices in capturing trace amounts of energy from the environment and transforming them into electrical energy. In addition, advancements in microprocessor technology have increased power efficiency, effectively reducing power consumption requirements. In combination, these developments have sparked interest in the engineering community to develop more and more applications that utilize energy harvesting for power.
Energy harvesting from a natural source where a remote application is deployed, and where such natural energy source is essentially inexhaustible, is an increasingly attractive alternative to inconvenient wall plugs and costly batteries. This essentially free energy source, when designed and installed properly, is available maintenance-free and is now available throughout the lifetime of the application. Such systems can be more reliable than wall plugs or batteries.
In addition, energy harvesting can be used as an alternative energy source to supplement a primary power source and to enhance the reliability of the overall system and prevent power interruptions. The history of energy harvesting dates back to the windmill and the waterwheel. People have searched for ways to store the energy from heat and vibrations for many decades. One driving force behind the search for new energy harvesting devices is the desire to power sensor networks and mobile devices without batteries. Energy harvesting is also motivated by a desire to address the issue of climate change and global warming.
The main motivation factors for the implimentation of the RF Energy harvesting are
n Advancements in microprocessor technology- The advanced microprocessors need less power consumption
n Advanced technical developments – Even Minute amount of Energy can be harvested
n A battery alone has a short lifetime
n Solar cells has its limitations
n A steady growth in the distances over which the tags can communicate
Advanced technical developments have increased the efficiency of devices in capturing trace amounts of energy from the environment and transforming them into electrical energy. In addition, advancements in microprocessor technology have increased power efficiency, effectively reducing power consumption requirements. In combination, these developments have sparked interest in the engineering community to develop more and more applications that utilize energy harvesting for power.
Energy harvesting from a natural source where a remote application is deployed, and where such natural energy source is essentially inexhaustible, is an increasingly attractive alternative to inconvenient wall plugs and costly batteries. This essentially free energy source, when designed and installed properly, is available maintenance-free and is now available throughout the lifetime of the application. Such systems can be more reliable than wall plugs or batteries.
In addition, energy harvesting can be used as an alternative energy source to supplement a primary power source and to enhance the reliability of the overall system and prevent power interruptions. The history of energy harvesting dates back to the windmill and the waterwheel. People have searched for ways to store the energy from heat and vibrations for many decades. One driving force behind the search for new energy harvesting devices is the desire to power sensor networks and mobile devices without batteries. Energy harvesting is also motivated by a desire to address the issue of climate change and global warming.
The main motivation factors for the implimentation of the RF Energy harvesting are
n Advancements in microprocessor technology- The advanced microprocessors need less power consumption
n Advanced technical developments – Even Minute amount of Energy can be harvested
n A battery alone has a short lifetime
n Solar cells has its limitations
n A steady growth in the distances over which the tags can communicate
Classification of Energy Harvesting devices
Classification of Energy Harvesting devices
We may classify the different energy harvesting devices in two ways: considering who or what provides the energy for conversion, and what type of energy is converted. Table 2 relates the two classification schemes. In the first classification scheme we can distinguish between two kinds of devices. First, devices that use part of the energy of the user of the electronic appliance. It will usually be a human, but it could be also an animal , for example for a remote monitoring device. We call this first kind of devices
The second kind of energy harvesting device gets its energy from the environment, and thus we call them Environment Energy devices. This classification takes into account that, following the first principle of thermodynamics, a greater amount of energy must be spent to obtain a certain amount of electrical energy. In the case of Human Power it is the user that in some way or other provides this energy and, though the energy levels are very small, the effect may prove noticeable when several devices depend on the activity of a single use.
In order to evaluate the burden of energy harvesting on user activities, it is possible to use a simple biomechanical model to calculate the energy involved in a human step,11 obtaining around 40 J. In comparison, the energy of a short RF transmission can be evaluated in the order of 100 μW. This means that the extra energy demanded to obtain enough energy is very small for some applications, and therefore it makes sense to consider human beings as a possible energy source
The second classification scheme may consider three types of energy: kinetic, electromagnetic radiation (including light and RF), and thermal. For Human Energy devices only kinetic and thermal energy are available. In the case of kinetic Human energy, one may distinguish between those actions made specifically to generate energy and casual movements made during normal behavior. These two cases are called by the Human Power research group of the Delft University of Technology12 Active and Passive Human Energy respectively. Following this definition, thermal Human Energy is always passive. Environment Energy sources include kinetic energy in the form of vibrations, radiation as solar energy or RF radiation, and thermal energy. The energy harvesting devices may pick up vibrations when located on machines, building elements or other places near vibrating sources. Radiation may come from natural or artificial sources. Thermal energy depends on the existence of a temperature gradient. While the transducing methods may be similar to the Human Energy devices, the excitation magnitudes, frequency spectra and periodicity are very different, and therefore each case must be studied separately. This will also have consequences in the electrical power conditioning circuit.
We may classify the different energy harvesting devices in two ways: considering who or what provides the energy for conversion, and what type of energy is converted. Table 2 relates the two classification schemes. In the first classification scheme we can distinguish between two kinds of devices. First, devices that use part of the energy of the user of the electronic appliance. It will usually be a human, but it could be also an animal , for example for a remote monitoring device. We call this first kind of devices
The second kind of energy harvesting device gets its energy from the environment, and thus we call them Environment Energy devices. This classification takes into account that, following the first principle of thermodynamics, a greater amount of energy must be spent to obtain a certain amount of electrical energy. In the case of Human Power it is the user that in some way or other provides this energy and, though the energy levels are very small, the effect may prove noticeable when several devices depend on the activity of a single use.
In order to evaluate the burden of energy harvesting on user activities, it is possible to use a simple biomechanical model to calculate the energy involved in a human step,11 obtaining around 40 J. In comparison, the energy of a short RF transmission can be evaluated in the order of 100 μW. This means that the extra energy demanded to obtain enough energy is very small for some applications, and therefore it makes sense to consider human beings as a possible energy source
The second classification scheme may consider three types of energy: kinetic, electromagnetic radiation (including light and RF), and thermal. For Human Energy devices only kinetic and thermal energy are available. In the case of kinetic Human energy, one may distinguish between those actions made specifically to generate energy and casual movements made during normal behavior. These two cases are called by the Human Power research group of the Delft University of Technology12 Active and Passive Human Energy respectively. Following this definition, thermal Human Energy is always passive. Environment Energy sources include kinetic energy in the form of vibrations, radiation as solar energy or RF radiation, and thermal energy. The energy harvesting devices may pick up vibrations when located on machines, building elements or other places near vibrating sources. Radiation may come from natural or artificial sources. Thermal energy depends on the existence of a temperature gradient. While the transducing methods may be similar to the Human Energy devices, the excitation magnitudes, frequency spectra and periodicity are very different, and therefore each case must be studied separately. This will also have consequences in the electrical power conditioning circuit.
ENERgy Harvesting
ENERgy Harvesting
Energy Harvesting is the process of capturing minute amounts of energy from one or more of these naturally-occurring energy sources, accumulating them and storing them for later use. Energy-harvesting devices efficiently and effectively capture, accumulate, store, condition and manage this energy and supply it in a form that can be used to perform a helpful task. Similarly, an Energy Harvesting Module is an electronic device that can perform all these functions to power a variety of sensor and control circuitry for intermittent duty applications.
Energy harvesting (also known as Power harvesting or energy scavenging) is the process by which energy is captured and stored. Frequently this term is applied when speaking about small autonomous devices, like those used in sensor networks. A variety of different sources exist for harvesting energy, such as solar power, thermal energy, wind energy, salinity gradients and kinetic energy.
Traditionally electrical power has been generated from fossil fuels in large, centralized plants. Large-scale ambient energy, such as sun, wind and tides, is widely available but trickier to harvest. In urban areas, there is a surprising amount of electromagnetic energy in the environment as a result of radio and television broadcasting.
Energy harvesting devices converting ambient energy into electrical energy have attracted much interest in both the military and commercial sectors. Some systems convert random motion, such as that of ocean waves, into electricity to be used by oceanographic monitoring sensors for autonomous operation. Future applications may include high power output devices (or arrays of such devices) deployed at remote locations to serve as reliable power stations for large systems. All of these devices must be sufficiently robust to endure long-term exposure to hostile environments and have a broad range of dynamic sensitivity to exploit the entire spectrum of wave motions.
Energy can also be harvested to power small autonomous sensors such as those developed using MEMS technology. These systems are often very small and require little power, but their applications are limited by the reliance on battery power. Scavenging energy from ambient vibrations, heat or light could enable smart sensors to be functional indefinitely. Several academic groups have been involved in the analysis and development of vibration-powered energy harvesting technology, including the Control and Power Group and Optical and Semiconductor Devices Group at Imperial College London, MIT, UC Berkeley and Southampton University.
Typical power densities available from energy harvesting devices are highly dependent upon the specific application and design of the harvesting generator. For motion powered devices , typical values are a few μW/cc for human body powered applications and hundreds of μW/cc for generators powered from machinery.
Energy Harvesting is the process of capturing minute amounts of energy from one or more of these naturally-occurring energy sources, accumulating them and storing them for later use. Energy-harvesting devices efficiently and effectively capture, accumulate, store, condition and manage this energy and supply it in a form that can be used to perform a helpful task. Similarly, an Energy Harvesting Module is an electronic device that can perform all these functions to power a variety of sensor and control circuitry for intermittent duty applications.
Energy harvesting (also known as Power harvesting or energy scavenging) is the process by which energy is captured and stored. Frequently this term is applied when speaking about small autonomous devices, like those used in sensor networks. A variety of different sources exist for harvesting energy, such as solar power, thermal energy, wind energy, salinity gradients and kinetic energy.
Traditionally electrical power has been generated from fossil fuels in large, centralized plants. Large-scale ambient energy, such as sun, wind and tides, is widely available but trickier to harvest. In urban areas, there is a surprising amount of electromagnetic energy in the environment as a result of radio and television broadcasting.
Energy harvesting devices converting ambient energy into electrical energy have attracted much interest in both the military and commercial sectors. Some systems convert random motion, such as that of ocean waves, into electricity to be used by oceanographic monitoring sensors for autonomous operation. Future applications may include high power output devices (or arrays of such devices) deployed at remote locations to serve as reliable power stations for large systems. All of these devices must be sufficiently robust to endure long-term exposure to hostile environments and have a broad range of dynamic sensitivity to exploit the entire spectrum of wave motions.
Energy can also be harvested to power small autonomous sensors such as those developed using MEMS technology. These systems are often very small and require little power, but their applications are limited by the reliance on battery power. Scavenging energy from ambient vibrations, heat or light could enable smart sensors to be functional indefinitely. Several academic groups have been involved in the analysis and development of vibration-powered energy harvesting technology, including the Control and Power Group and Optical and Semiconductor Devices Group at Imperial College London, MIT, UC Berkeley and Southampton University.
Typical power densities available from energy harvesting devices are highly dependent upon the specific application and design of the harvesting generator. For motion powered devices , typical values are a few μW/cc for human body powered applications and hundreds of μW/cc for generators powered from machinery.
Unique characteristics of a WSN include
Unique characteristics of a WSN include:
· Limited power they can harvest or store
· Ability to withstand harsh environmental conditions
· Ability to cope with node failures
· Mobility of nodes
· Dynamic network topology
· Communication failures
· Unattended operation
· Heterogeneity of nodes
· Large scale deployment
· Limited power they can harvest or store
· Ability to withstand harsh environmental conditions
· Ability to cope with node failures
· Mobility of nodes
· Dynamic network topology
· Communication failures
· Unattended operation
· Heterogeneity of nodes
· Large scale deployment
WIRELESS SENSORS
WIRELESS SENSORS
A wireless sensor network (WSN) is a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions , such as temperature , sound, vibration , pressure , motion or pollutants , at different locations . The development of wireless sensor networks was originally motivated by military applications such as attlefield surveillance . However , wireless sensor networks are now used in many civilian application areas , including environment and habitat monitoring, healthcare applications, home automation, and traffic control.
In addition to one or more sensors , each node in a sensor network is typically equipped with a radio transceiver or other wireless communications device, a small microcontrolle r, and an energy source, usually a battery. The envisaged size of a single sensor node can vary from shoebox-sized nodes down to devices the size of grain of dust , although functioning 'motes' of genuine microscopic dimensions have yet to be created.The cost of sensor nodes is similarly variable, ranging from hundreds of dollars to a few cents , depending on the size of the sensor network and the complexity required of individual sensor nodes. Size and cost constraints on sensor node result in corresponding constraints on resources such as energy, memory, computational speed and bandwidth.A sensor network normally constitutes a wireless a d - hoc network , meaning that each sensor supports a multi – hop routing algorithm ( several nodes may forward data packets to the base station).
A wireless sensor network (WSN) is a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions , such as temperature , sound, vibration , pressure , motion or pollutants , at different locations . The development of wireless sensor networks was originally motivated by military applications such as attlefield surveillance . However , wireless sensor networks are now used in many civilian application areas , including environment and habitat monitoring, healthcare applications, home automation, and traffic control.
In addition to one or more sensors , each node in a sensor network is typically equipped with a radio transceiver or other wireless communications device, a small microcontrolle r, and an energy source, usually a battery. The envisaged size of a single sensor node can vary from shoebox-sized nodes down to devices the size of grain of dust , although functioning 'motes' of genuine microscopic dimensions have yet to be created.The cost of sensor nodes is similarly variable, ranging from hundreds of dollars to a few cents , depending on the size of the sensor network and the complexity required of individual sensor nodes. Size and cost constraints on sensor node result in corresponding constraints on resources such as energy, memory, computational speed and bandwidth.A sensor network normally constitutes a wireless a d - hoc network , meaning that each sensor supports a multi – hop routing algorithm ( several nodes may forward data packets to the base station).
RF Radiation
RF Radiation
RF radiation is employed to power ID cards by directing high power electromagnetic energy to the devices from a nearby source. In addition to energy, it is possible to send information as well. However, the term energy harvesting implies that it is the same device which gets its energy from the environment. In cities and very populated areas there is a large number of potential RF sources: broadcast radio and tv, mobile telephony, wireless networks, etc. The problem is collecting all these disparate sources and converting them in useful energy. The conversion is based on a rectifying antenna (rectenna), constructed with a Schottky diode located between the antenna dipoles. The energy levels actually present are so low that no present electronic device can use them. However, future technologies may allow the fabrication of lower power devices that would “recycle” RF energy generated for other purposes by different elements
RF radiation is employed to power ID cards by directing high power electromagnetic energy to the devices from a nearby source. In addition to energy, it is possible to send information as well. However, the term energy harvesting implies that it is the same device which gets its energy from the environment. In cities and very populated areas there is a large number of potential RF sources: broadcast radio and tv, mobile telephony, wireless networks, etc. The problem is collecting all these disparate sources and converting them in useful energy. The conversion is based on a rectifying antenna (rectenna), constructed with a Schottky diode located between the antenna dipoles. The energy levels actually present are so low that no present electronic device can use them. However, future technologies may allow the fabrication of lower power devices that would “recycle” RF energy generated for other purposes by different elements
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