Nano-Solar - A Technique for Optimal Usage of Solar Energy

Transcription

1 Nano-Solar - A Technique for Optimal Usage of Solar Energy HARISH THUTUPALLI Electronics and Instrumentation engineering, CVR College of Engineering, Hyderabad , AP, India. E.Mail: harish.endeavour.fluky@gmail.com Abstract: Nano-solar is a technique designed in order to help the world to fulfill its energy requirements. Our resources of energy are in their merge of extinction. So to fabricate our present luxury and comfort we are in urge to have an alternative for this energy generation. This alternative will surely be renewable energies i.e. solar energy. But it needs investments such as large working area and also amount in huge. To avert this we are applying nanotechnology in case of this conversion of solar energy into electrical energy. Photo voltaic cell is used for the generation of electricity from the renewable solar energy. The application of nanotechnology in forms of nano-tubes in consideration with photovoltaic cells is done. The implementation of photovoltaic cells is also explained. It also provides a designated solution for space requirements in case of implementing the conversion process of solar energy into electrical energy. The paper reveals how this world can get its freedom in energy requirements. Energy requirements of the world will also be solved only through nanotechnology and applications. So nanotechnology is not only an atomic re-constructor but also a sensitive and efficient tool for energy generation and also for many other aspects. So if nanotechnology has been implemented incase of photovoltaic cells, it will surely be resolution for power generation from the solar energy. By applying the nanotechnology, world will be the handled device of nanotechnology and it will also be true in case of energy generation. Introduction We are all in the world of extinction i,e. our resources of energy are in their merge of extinction, with their depletion the world will be a zero in case we have then nothing to do with this world. So to fabricate our present luxury and comfort we are in urge to have an alternative for this energy generation. This alternative will surely be renewable energies. With that the best we are having is our life giving solar energy. Even though we are generating our energy by means of solar energy, it needs investments such as large working area and also amount in huge. To avert this we are applying nanotechnology in case of this conversion of solar energy into electrical energy [2]. Nanotechnology can be prominently be defined as an application of particles which are nanometers in size. We can have nanotubes, nanopoweders, nanorobots etc, in the sense we can also define nanotechnology as a tool for atomic reconstruction of products, so no property of a material will be getting modified. Nanotechnology can also be used as reducing the size of the atoms without altering its property. We are having photovoltaic cells for the generation of electricity from solar energy this photo voltaic cell can be defined as semi conductor devices, usually made of silicon, which contain no liquids corrosion chemicals or moving parts, nanotubes which are applied with photo voltaic cells can be defined as nanocrystalline material and can grow up to 200 nanometers. With this property the efficiency of the photo voltaic cells has been tending to increase. Nanotubes are best replacers to certain dye sensitive areas in solar cells. Need To Apply Nano Technology in Energy Generation Even though we are having many existing technologies to generate electrical energy from solar but all need wide space and huge economic. We all know with solar energy, we can even generate energy 20 times as more than this world is requiring, but due to large scale of economy and lack of efficiency we are unable to implant the current technologies. So the experts are now in the thirst for new technology which should have to overcome the defects of prevailing IJAEM SRC. All rights reserved.

2 HARISH THUTUPALLI technologies such as size of product and low efficiency. After curious research and implementation we have got nanotechnology solution for this above described problems. Because when we apply normal technologies size of solar cell will be at least up to 200mm but when the same is engineered or created with the application of nanotechnology, the overall size of solar cell will be restricted up to 50nms. Because if normal photo voltaic cell with dye sensitive agents in the size of 5mm generates 3watts of power then same photovoltaic cell but dyes sensitive agent replace with nanotubes can generate power up to 6.4watts. So no technology can bridge the nanotechnology. Hence nanoprodudcts or nanomaterials are having higher efficiency in comparison with other products. So need for implementation has made clear cut of nanotechnology in energy generation. The current goal for the research community is to improve the life time and efficiency of organic solar cells. Generation of Electricity with Photovoltaic Cells Photo voltaic cells come in many sizes, but most are 10cm by 10cm and generate about half a volt of electricity. PV cells are bundled together in modules or panels to produce higher voltages and increased power. A 12volt module, for example, depending on its power output, could have 30-40PV cells. A module producing 50 watts of power measures approximately 40cm by 100cm. PV panels are not highly efficient, converting only 12-15%of the sun s light in to electricity, but laboratory proto types are reaching 30% efficiency. PV modules generate D.C, the kind of electricity produced by batteries. Although incandescent light s can operate on D.C, most electric devices require 120volt AC as supplied by utilities a device known as an inverter converts DC to AC current. Inverters vary in size and in the quality of electricity they supply. Less expensive inverters are suitable for simple loads, such as lights and water pumps, but models with good quality wave form output are needed to power electronic devices such as TVs, stereos microwave ovens and computers. Working of PV Photovoltaic is the direct conversion of light into electricity at atomic level. Some materials exhibit a property known as photo electric effects that causes them to absorb photons of light and release electrons. When these electrons are captured, an electric current result that can be used as electricity. The diagram above illustrates the operation of a basic photovoltaic cell, also called a solar cell. Solar cells are made of the same kinds of semiconductor materials, Such as silicon. For solar cells, a thin semiconductor wafer is specially treated to form an electric field, positive on one side and negative on the other. When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconducting material. This electricity can then be used to power a load, such as a light or a tool. A number of solar cells electrically connected to each other and mounted in a support structure or frame is called a photovoltaic module. Modules are designed to supply electricity at a certain voltage, such as a common 12 volts system. The current produced is directly dependent on how much light strikes the module [3]. Implementation of PV Cells When a photon is absorbed, its energy is given to an electron in the crystal lattice. Usually this electron is in the valance band, and is tightly bound in covalent bonds between neighboring atoms, and hence unable to move far. The energy given to it by the photon excites it into the conduction band, where it is free to move around within the semiconductor. The covalent bond that the electron was previously is a part of now has one fewer electron-this is known as a hole. The presence of a missing covalent bond allows the bonded electrons of neighboring atoms to move in to the hole, leaving another hole behind, and in this way a hole can move through the lattice. Thus, it can be said that photons absorbed in the semiconductor create mobile electron-hole pairs. A photon need only have greater energy than that of band gap in order to excite an electron from the valance band in to the conduction band. However, the solar frequency spectrum approximates a black body spectrum at ~6000k, and as such, much of the solar radiation reached. Multiple modules can be wired together to form an array. In general the larger the area of a module or array, the more electricity that will be produced. Photo voltaic modules and arrays produce D.C. they can be connected in both series and parallel electrical arrangements to produce any required voltage and current combination. Today s most common PV devices use a single junction, or interface, to create an electric field with n a semi conductor such as a PV cell. In a single junction PV cell, only photons whose energy is equal

3 Nano-Solar - A Technique for Optimal Usage of Solar Energy to or greater than the band gap of the cell material can free an electron for an electric circuit. In other words, the photovoltaic response of single junction cells is limited to the portion of the sun s spectrum whose energy is above the band gap of the absorbing material, and lower energy photons. remain efficient even when the sun is not directly overhead. That could allow them to be used on spacecraft without the mechanical aiming systems that maintain a constant orientation to the sun, reducing weight and complexity and improving reliability. The efficiency of our cells increases as the sunlight goes away from perpendicular, so we may not need mechanical arrays to rotate our cells, Ready noted [1]. The ability of the 3D cells to absorb virtually all of the light that strikes them could also enable improvements in the efficiency with which the cells convert the photons they absorb into electrical current. In conventional flat solar cells, the photovoltaic coatings must be thick enough to capture the photons, whose energy then liberates electrons from the photovoltaic materials to create electrical current. However, each mobile electron leaves behind a hole in the atomic matrix of the coating. The longer it takes electrons to exit the PV material, the more likely it is that they will recombine with a hole -- reducing the electrical current. Because the 3D cells absorb more of the photons than conventional cells, their coatings can be made thinner, allowing the electrons to exit more quickly, reducing the likelihood that recombination will take place. That boosts the quantum efficiency the rate at which absorbed photons are converted to electrons of the 3D cells. Fig. 1. Implementation of PV Cells One way to get around this limitation is to use two or more different cells, with more than one band gap and more than one junction, to generate a voltage. These are referred to as multijunction cells. Multijunction devices can achieve higher total conversion efficiency because they can convert more of the energy spectrum of light to electricity. Application of Nanotechnology in Photovoltoic Cells The GTRI photovoltaic cells trap light between their tower structures, which are about 100 microns tall, 40 microns by 40 microns square, 10 microns apart -- and built from arrays containing millions of verticallyaligned carbon nanotubes. Conventional flat solar cells reflect a significant portion of the light that strikes them, reducing the amount of energy they absorb. Because the tower structures can trap and absorb light received from many different angles, the new cells Fabrication of the cells begins with a silicon wafer, which can also serve as the solar cell s bottom junction. The researchers first coat the wafer with a thin layer of iron using a photolithography process that can create a wide variety of patterns. The patterned wafer is then placed into a furnace heated to 780 degrees Celsius. Hydrocarbon gases are then flowed into furnace, where the carbon and hydrogen separate. In a process known as chemical vapor deposition, the carbon grows arrays of multi-walled carbon nanotubes atop the iron patterns.

4 HARISH THUTUPALLI Once the carbon nanotube towers have been grown, the researchers use a process known as molecular beam epitaxy to coat them with cadmium telluride (CdTe) and cadmium sulfide (CdS) which serve as the p-type and n-type photovoltaic layers. Atop that, a thin coating of indium tin oxide, a clear conducting material, is added to serve as the cell s top electrode. conducting polymeric films. This has opened up new opportunities in solar cell research and development and, consequently, there is considerable investor interest in solar nanotechnology startups. The Use of Carbon Nanotubes in Solar Cells Carbon nanotubes have been integrated in organic photovoltaic devices both as an electron accepter material and as a transparent electrode. CNTs are well suited for such uses since they can not only efficiently transport electrons, but can also provide a high electric field at the nanotubes interfaces. The charge transfer mechanism in polymer matrix containing fullerenes also provided the motivation for investigating the use of carbon nanotubes as an electron transport material. The tubes are then heated in oxygen so that they crystallize. The process turns the opaque coating of titanium in to a transparent coating of nanotubes. This nanotube array is then coated in a commercially available dye. The dye coated nanotubes make up the negative electrode and a positive electrode seals the cell which contains an iodized electrolyte. When sun shines through the glass, the energy falls on the dye molecules and an electron is freed. If this electron and others make their way out of the tube to the negative electrode, a current flows. Many electrons do not and are recombined, but the tube structure of the titanium dioxide allows an order of magnitude more electrons to make it to the electrode than with particular coatings. Fig. 2. Carbon nanotubes in solar panels The impact of nanotechnology maybe to lower the cost of solar PV by reducing the materials required or by introducing more effective manufacturing methods. It also increases the efficiency of semi conductor materials and enable novel applications of solar PV technology. The functional aspects would be Durability: The target lifetime for a PV cell is at least 20 years, in a temperature range of -40 to 85 degrees centigrade Easy installation: The lighter the PV cell is, the more numerous locations in which they can be installed. Disposable: A solar PV cell is environmentalfriendly, it is important that cells can be disposed safely at the end of their life. This mitigates against the use of heavy metals. Future Electricity Generation with Nanotechnology Concerning Effectiveness of PV Cells With Nano Technology With an increased focus on alternative sources of cheap, abundant, clean energy, solar cells are receiving lots of attention. Harnessing the power of the sun to replace the use of fossil fuels holds tremendous promise. One way to do this is through the use of solar, or photovoltaic, cells. By nanotechnology, this is now being challenged by a development of a new generation of solar cells based on thin film materials, nanocrystilline materials and Imagine the year 2035 with full of nano s applications if it happens the all of us are the richer most and anything can be kept under the control of us i.e. world becomes a village and will come within our palm. In the future nanotechnology will be a best and effective solution for the lack of energy resources. Nanotechnology a upside down technology we are saying that because country s wealth is depending upon its capacity and its self-sustained in case of energy. but in future a country s wealth will be surely depending upon the implementation of nanotechnology and also by creating some nanomaterials. In the year of 2007 nanotechnology industry has reached its turn over of $10 billion with 48 products marketed by 400 companies worldwide. So in future

5 Nano-Solar - A Technique for Optimal Usage of Solar Energy this industry will be having a traditional impact over a country s economy. In case of Japan the fast growing nation in this world has a project that includes the application of nanotechnology in electricity generation from solar energy and this will soon be completed in the year of 2035 and when this is implemented each and every Japanese will be charging their laptops not in their room but even in beach under the solar umbrella.so in future nanotechnology will surely be a good opt for solar recreation. So when each and every stats to implements it there no energy starvation in this beautiful world.so people should aware about the applications of nanotechnology and they should also be provided with nanomaterials for energy generation by the government to pave the way for comfort of nation [1]. Conclusions Even though it is hypothetical now, when implemented it will surely be a boon to be the future generation. Likewise energy requirements of the world will also be soluted only through nanotechnology and applications. So we can say nanotechnology not only an atomic reconstructor and also as a sensitive and efficient tool for energy generation and also for many other aspects. So if nanotechnology has been implemented incase of photovoltaic cells, it will surely be resolution for power generation from the solar energy. It will also act as a good solution where the energy is required as high.we can have a credit by applying the nanotechnology and in 2025 world is the handled device of nanotechnology and it will also be true in case energy generation. REFERENCES [1] Erik Drexler.: Nanotechnology a Future, The technical journal Chemical and Engineering (2005) [1] Gregory M Fahy,: Nanotechnology, (1992) [2] [3] [4] [5] [6]