role of nanocoating in maintaining solar pv efficiency ...

ISSN: 2231-3842 (Print)

ISSN: 2277-8691 (Online)

ROLE OF NANOCOATING IN MAINTAINING SOLAR PV EFFICIENCY: AN OVERVIEW Vandana Yadav1*, Abhilasha Mishra2 University of Petroleum & Energy Studies, Dehradun 2 Advance Institute of Scinece &Technology, Dehradun *Email: [email protected]

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Abstract: Solar energy is cleaner and sustainable than any of the other energy streams. A drop of efficiency of solar PV panels is due to the depositions left by birds, pollution and the dust caused by traffic or from the agricultural activities. Ideally solar panels should be cleaned every few weeks to maintain peak efficiency, which is especially hard to do for large solar-panel arrays. Cleaning dirty panels with commercial detergents can be time-consuming, costly and hazardous to the environment. To overcome the loss in power output of solar PV due to dust, application of nanocoating is one of the possible solutions. Here we are discussing about self cleaning nanocoatings for solar panels which enhance their efficiency. Nanostructured coatings offer great potential for various applications due to their superior characteristics that are not typically found in conventional coatings. A nanocoating repels dust, pollen and other particles, and could keep solar panels clean and operating at their peak efficiency longer than conventional panels. Keywords: Solar panels, nanocoatings, efficiency, hydrophobic, nanostructured. INTRODUCTION Energy demand is expected to increase considerably in the coming years as the result of population growth and economic development. The world is presently facing an ‘energy chal-lenge’ and there is an urgent need for alterna-tive energy resources to fossil fuels. Of these, renewable energy sources that are CO2-neu-tral includes solar, wind, geothermal, hydro, etc. provides an option. Out of these, all resources are not present everywhere. So we need a source which is present in most of the places in our earth. Without any doubts, it is Solar Energy as we all know that rays of sun reaches almost each and every corner of our planet. So, it is definitely a source which would empower our future. International Journal of Applied Science and Technology

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Solar cells are photovoltaic (PV) devices which can convert photons into electrical energy by way of the photoelectric effect. A drop in the efficiency of a solar PV panel throughout its life cycle is not desired, since the capital cost for the system is quite high. PV cells can normally last for about 25 years, and it takes approximately up to six years for the solar PV module to generate the equivalent amount of energy consumed in its manufacturing processes [1]. The beauty of solar energy is that it can be produced by every house hold on his rooftop or farm. We consume only a fraction of the energy delivered by the Sun. Theoretically; it is possible to convert the rest into usable and transportable energy. If we add into that the potential of energy generated by Sun’s invisible rays (infrared), the potential is really immense. Moreover this energy will be cleaner and sustainable than any of the other energy streams. Because of that possibility, in today’s time, not only energy but clean energy is becoming a huge business in itself. Many of the developments in clean energy revolve around strategic applications of nano science. Every day, the Earth is hit by 165 000 TW of solar power; in the words of Nobel Prizewinner Richard E. Smal-ley, every day ‘we are bathed in energy’ [2]. The problem is that renewable energy sources like solar energy are not constant in time and evenly distributed geographically. Therefore, solar energy collection, conversion, storage and distribution are major challenges: the entire pro-cess needs to be efficient and cost effective. In order to meet the ‘energy challenge’ through solar energy, solar PV cells with conversion efficiencies in the order of 45 % are needed where as cur-rent solar panels have about 15–20 % energy conversion efficiency. One of the contributing factors in the drop of efficiency of solar PV panels in India as well as in other country is the depositions left by birds, pollution and the dust caused by traffic or from the agricultural activities. Solar panels need a clean surface to gather light efficiently from the sun which can be a challenging task in dusty environments. The accumulation of dust, dirt, or debris can reduce their power capabilities by up to 20% during a dry summer [3]. To Cleaning dirty panels with commercial detergents can be time-consuming, costly, hazardous to the environment, or even corrode the solar panel frame. Ideally solar panels should be cleaned every few weeks to maintain peak efficiency, which is especially hard to do for large solar-panel arrays. 22

International Journal of Applied Science and Technology

ISSN: 2231-3842 (Print)


Nano technology has shown the possibility of fulfilling everyone’s dream of getting cheap and clean energy through its strategic applications. Its intersection with energy is going to change the way energy was hitherto being generated, stored, transmitted, distributed and managed. Nanotechnology is particularly going to revolutionize the solar energy sector. Nanotechnology offers more possibilities in solar energy sector than they have been experimented today. The entire technology is in the process of evolution. But one thing is sure: it offers immense potential to harness solar energy. To overcome the loss in power output of solar PV due to dust, application of nanocoating is one of the possible solutions. Nano-coating on solar glass could increase the transmission up to 96% thus raises the efficiency of solar panels. The nanocoatings reduced the reflectance of the solar cells by approximately 10% across the near UV to near IR spectral range, which provided a 17% increase in the output power of the devices (which translated to a 10% relative increase in the efficiency). It has very low dust accumulation it is easily cleaned by rain water. The anti-soil effect has a direct influence on the panel performance. A nanocoating repels dust, pollen and other particles, and could keep solar panels clean and operating at their peak efficiency longer than conventional panels. LOTUS-MIMICKING PV

COATINGS

The development of superhydrophobic self cleaning surface was first inspired by lotus leaves [4] and other plant leaves [5]. The lotus leaf is characterized by being extremely water-repellent, so much so that water simply rolls off its surface dragging dirt with it. SEM studies of lotus leaves [6] revealed that a microscopically rough surface consisting of an array of randomly distributed micropapillae with diameter ranging from 5-10 micrometer. These micropapillae are covered with hierarchical structures in the form f nanostructures with an average diameter of about 125 nm. Motivated by lotus leaves many techniques have been developed to create nanostructures mimicking the lotus effect from many organic and inorganic materials [7-8]. Superhydrophobic surfaces are useful in improving the performance of solar cells. One of the problems with this technology is that the cells are outside and, therefore, prone to becoming very dirty. This layer of dirt ‘masks’ the catalytic areas of the solar cells and so reduces their efficiency and lifetime. Coating the solar panel with a International Journal of Applied Science and Technology

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superhydrophobic coating keeps the panel considerably cleaner. Because of the nano-surface roughness, the coating is transparent to UV light, a necessity for these types of devices. The superhydrophobic coating is also durable, which further improves the solar panel lifetime. YD Ziang et al developed a high quality SiO 2 based transparent superhydrophobic coatings with double roughness microstructures and high durability. These cotings were deposited onto glass substrate by combustion chemical vapor deposition (CCVD) technique [9]. NANOCOATINGS Nanocoating are coating that produced by usage of some components at nanoscale to obtain desired properties. Nanocoatings offer great potential for various applications due to their superior characteristics that are not typically found in conventional coatings. Significant work on nanocoatings is underway globally in the area of nanocoating in the way of incorporating nanoparticles in coating formulation that enhance specific features. [1014]. Nanocoatings have been extensively used on glass, and the advantages are well known. A coating can make glass Hydrophobic & Dust Repellant and therefore makes it easier to clean the glass. Nanocoatings are a type of nanocomposite. The layer thickness of a nanocoating is usually 1–100 nm. Nanocomposite films include multilayer thin films, in which the phases are separated along the thick-ness of the film, or granular films, in which the different phases are distributed within each plane of the film. Nanocoatings make it possible to change the properties of some materials, for example to change the transmission of visible and IR radiation in glass, or to introduce new properties such as ‘self-cleaning’ effects.

Without Nano Coating

With Nano Coating

Fig.1: glass surface without and with nanocotings 24


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Nanostructured coatings offer great potential for various applications due to their superior characteristics that are not typically found in conventional coatings. Ë

Contact tension reduced (water repellence).

Ë

Moisture penetration is minimized.

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Surface roughness reduces to 1 nm for better dirt repellence.

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Nanostructured helps to maintain important surface and to accelerate drying.

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Nanoparticles helps increased hydrophobicity and alter the wetting properties.

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On a surface treating with nanoparticles water cannot adhere and at the molecular level is not in contact with the surface at all. This molecular force pushes water and anything in it away.

TYPES

OF

NANOCOATING:

TRIBOLOGICAL

NANOCOATINGS

Tribological coatings are those coatings that are applied to the surface of a com-ponent in order to control its friction and wear. In this area, the term ‘thin films’ is often used as an alternative to nanocoatings, due to the fact that this is an area of innovation that has existed for many years and has now reached the nanoscale. When applied to machinery and tools, tribological coatings can reduce (or eliminate) the need for lubricants, increase cutting speed, increase the rate of material removal, reduce maintenance costs or reduce processing cycle times [5-16]. RESPONSIVE

NANOCOATINGS

Responsive nanocoatings are those where the properties of the material in the coating react to environmental conditions, such as light or heat, either in a passive or an active way. These coatings allow the properties of some materials to change, such as glass, by conferring new or improved properties Stimuli-Responsive Polymer Nanocoatings [17]. SUPERHYDROPHILIC

COATINGS

Superhydrophilic surfaces cause water to spread out. Such surfaces will naturally dry out quickly and prevent fogging up when in contact with steam or condensation. These properties are of special interest for several outdoor and indoor applications, such as windows, mirrors or shower International Journal of Applied Science and Technology

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screens. Additional applications include easy-clean household goods and road signs, anti-condensation air conditioners and anti-fouling paints [18]. Another area where superhydrophilicity is essential is photocatalytic selfcleaning surfaces [19]. In these surfaces, self-cleaning is based on a photocatalytic process, which causes a chemical breakdown of organic dirt adsorbed onto the hydrophilic surface when exposed to light [20]. SUPERHYDROPHOBIC

COATINGS

Superhydrophobic coatings are increasingly attractive to the industry and academia due to their unique self-cleaning properties as a result of their water repelling characteristics [21]. Fabrication of superhydrophobic coating is an inspiration from nature as water is seen to repel on many natural surfaces such as those of the lotus leaves, butterfly wings, water striders’ legs, and so on [22-23]. This behavior of water drops rolling off their surfaces is due mainly to the presence of a combination of rough micro-nanostructure and low surface energy waxy materials on their surfaces. This concept has been well elaborated by Neinhuis et al. [24] on the surface of the lotus leaves which has been the classic example is the field of superhydrophobicity for researchers around the globe emphasizing the .importance of the geometry and the chemistry of the surface. ADVANTAGES The three main advantages of Nano coatings for solar panels are the following: HYDROPHOBIC One of the advantages that counts for PV modules installed in rainy climates is the hydrophobic properties. This causes water to repel more quickly than uncoated “self-cleaning glass”. This hydrophobic coating helps panels to let water flow off more easily and therefore would make the solar panel more efficient during inclement weather. SELF-CLEANING

PROPERTIES

The coating’s self-cleaning effect stops dust and bird poo from sticking to PV panels. With the help of the coating, all dirt will be easily removed after a little bit of rain or after manually spraying water on the panels. This 26


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would help the panels to stay clean, maintain their efficiency and ensure that the maximum amount of electricity is produced. You would still need to ‘water your PV modules’ regularly to remove the dirt, in case you’re living in a warm climate without much rain. MAINTENANCE Climbing on a roof to clean PV modules may be dangerous. Hiring someone else to do it can be costly. If you can limit maintenance by simply spraying some water on the roof, and let the Nano coating do the rest, it sounds like a good alternative. CHALLENGES REDUCED

TRANSMITTANCE

Applying an extra coating on top of the surface of a clean PV module will not necessarily increase the efficiency. In fact, an extra coating will most likely reduce the transmittance of sunlight. It’s important to understand that efficiency is only gained, when the reduced light transmission caused by dirt is removed with the help of the coating. You will still need to wash off the PV modules regularly to keep them clean. CONCLUSIONS Solar panels need a clean surface to gather light efficiently from the sun, but they are often soiled by water and debris that can reduce their power capabilities. A nanocoating repels dust, pollen and other particles, and could keep solar panels clean and operating at their peak efficiency longer than conventional panels. A self-cleaning nano-thin hydrophobic coating layer repels water and particles without interfering with the solar panel’s ability to absorb sunlight. These coating can last for years, reducing maintenance and operation costs. REFERENCES: 1.

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