International Journal of Applied Sciences, Engineering and Management ISSN 2320 – 3439, Vol. 02, No. 01, January 2013, pp. 15 - 19

Nano-Solar - A Technique for Optimal Usage of

HARISH THUTUPALLI Electronics and Instrumentation engineering, CVR College of Engineering, Hyderabad-501510, AP, India. E.Mail: [email protected]

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 Need To Apply Nano Technology in Energy electricity from solar energy this photo voltaic cell can Generation be defined as semi conductor devices, usually made of Even though we are having many existing silicon, which contain no liquids corrosion chemicals technologies to generate electrical energy from solar or moving parts, nanotubes which are applied with but all need wide space and huge economic. We all photo voltaic cells can be defined as nanocrystalline know with solar energy, we can even generate energy material and can grow up to 200 nanometers. With 20 times as more than this world is requiring, but due this property the efficiency of the photo voltaic cells to large scale of economy and lack of efficiency we has been tending to increase. Nanotubes are best are unable to implant the current technologies. So the replacers to certain dye sensitive areas in solar cells. experts are now in the thirst for new technology which should have to overcome the defects of prevailing

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

International Journal of Applied Sciences, Engineering and Management ISSN 2320 – 3439, Vol. 02, No. 01, January 2013, pp. 15 - 19 Nano-Solar - A Technique for Optimal Usage of Solar Energy to or greater than the band gap of the cell material can remain efficient even when the sun is not directly free an electron for an electric circuit. In other words, 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” the photovoltaic response of single junction cells is in the atomic matrix of the coating. The longer it takes limited to the portion of the sun’s spectrum whose electrons to exit the PV material, the more likely it is energy is above the band gap of the absorbing that they will recombine with a hole -- reducing the material, and lower energy photons. 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 Fabrication of the cells begins with a silicon wafer, The GTRI photovoltaic cells trap light between their which can also serve as the solar cell’s bottom tower structures, which are about 100 microns tall, 40 junction. The researchers first coat the wafer with a microns by 40 microns square, 10 microns apart -- and thin layer of iron using a photolithography process built from arrays containing millions of vertically- that can create a wide variety of patterns. The aligned carbon nanotubes. Conventional flat solar patterned wafer is then placed into a furnace heated to cells reflect a significant portion of the light that 780 degrees Celsius. Hydrocarbon gases are then strikes them, reducing the amount of energy they flowed into furnace, where the carbon and hydrogen absorb. separate. In a process known as chemical vapor Because the tower structures can trap and absorb light deposition, the carbon grows arrays of multi-walled received from many different angles, the new cells carbon nanotubes atop the iron patterns.

International Journal of Applied Sciences, Engineering and Management ISSN 2320 – 3439, Vol. 02, No. 01, January 2013, pp. 15 - 19 HARISH THUTUPALLI

Once the towers have been grown, conducting polymeric films. This has opened up new the researchers use a process known as molecular opportunities in solar cell research and development beam epitaxy to coat them with and, consequently, there is considerable investor (CdTe) and cadmium sulfide (CdS) which serve as the interest in solar nanotechnology startups. p-type and n-type photovoltaic layers. Atop that, a thin coating of , a clear conducting material, is added to serve as the cell’s top electrode.

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 so that they crystallize. The process turns the opaque coating of titanium in to a transparent coating of nanotubes. This Fig. 2. Carbon nanotubes in solar panels nanotube array is then coated in a commercially available dye. The dye –coated nanotubes make up the The impact of nanotechnology maybe to lower the negative electrode and a positive electrode seals the cost of solar PV by reducing the materials required or cell which contains an iodized electrolyte. by introducing more effective manufacturing methods. When sun shines through the glass, the energy falls on It also increases the efficiency of semi conductor the dye molecules and an electron is freed. If this materials and enable novel applications of solar PV electron and others make their way out of the tube to technology. The functional aspects would be the negative electrode, a current flows. Many Durability: The target lifetime for a PV cell is at least electrons do not and are recombined, but the tube 20 years, in a temperature range of -40 to 85 degrees structure of the titanium dioxide allows an order of centigrade magnitude more electrons to make it to the electrode than with particular coatings. Easy installation: The lighter the PV cell is, the more numerous locations in which they can be installed.

Disposable: A solar PV cell is environmental- friendly, 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

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. Concerning Effectiveness of PV Cells With Nano Nanotechnology –a upside down technology we are Technology saying that because country’s wealth is depending With an increased focus on alternative sources of upon its capacity and its self-sustained in case of cheap, abundant, clean energy, solar cells are energy. but in future a country’s wealth will be surely receiving lots of attention. Harnessing the power of depending upon the implementation of the sun to replace the use of fossil fuels holds nanotechnology and also by creating some tremendous promise. One way to do this is through nanomaterials. the use of solar, or photovoltaic, cells. By In the year of 2007 nanotechnology industry has nanotechnology, this is now being challenged by a reached its turn over of $10 billion with 48 products development of a new generation of solar cells based marketed by 400 companies worldwide. So in future on materials, nanocrystilline materials and

International Journal of Applied Sciences, Engineering and Management ISSN 2320 – 3439, Vol. 02, No. 01, January 2013, pp. 15 - 19 Nano-Solar - A Technique for Optimal Usage of Solar Energy this industry will be having a traditional impact over a nanotechnology not only an atomic reconstructor and country’s economy. In case of Japan the fast growing also as a sensitive and efficient tool for energy nation in this world has a project that includes the generation and also for many other aspects. So if application of nanotechnology in electricity nanotechnology has been implemented incase of generation from solar energy and this will soon be photovoltaic cells, it will surely be resolution for completed in the year of 2035 and when this is power generation from the solar energy. It will also implemented each and every Japanese will be act as a good solution where the energy is required as charging their laptops not in their room but even in high.We can have a credit by applying the beach under the solar umbrella.So in future nanotechnology and in 2025 world is the “handled nanotechnology will surely be a good opt for solar device of nanotechnology” and it will also be true in recreation. So when each and every stats to case energy generation. implements it there no energy starvation in this beautiful world.So people should aware about the REFERENCES applications of nanotechnology and they should also be provided with nanomaterials for energy generation [1] Erik Drexler.: “Nanotechnology a Future”, The by the government to pave the way for comfort of technical journal Chemical and Engineering nation [1]. (2005) [1] Gregory M Fahy,: “Nanotechnology”, (1992) Conclusions [2] www.wikipedia.com [3] www.nanosolns.com Even though it is hypothetical now, when [4] www.nanosolar.com implemented it will surely be a boon to be the future [5] www.ask.com generation. Likewise energy requirements of the [6] www.earthandsky.com world will also be soluted only through nanotechnology and applications. So we can say

International Journal of Applied Sciences, Engineering and Management ISSN 2320 – 3439, Vol. 02, No. 01, January 2013, pp. 15 - 19