Photovoltaic Efficiency: Solar Panel - Article Example

PHOTOVALTIAC EFFICIENCY: SOLAR PANAL - Advances in industrialisation coupled with high rural urban migration has created the need for increased demand for energy. Solar energy has thus been noted to be a very useful source of renewable natural energy that is safe and environmentally friendly. Through secondary data review, the paper has noted that photovoltaic efficiency depends on several factors and conditions. Some of these factors that have been elaborated in the paper include the absorbing power of the solar panels, efficacy of solar inventers and effectiveness of solar tracking system to better the performance of the photovoltaic (PV) power. In effect, selecting the right solar panel model from such alternatives as conventional PV, concentrated PV and high concentrated PV is thus a responsibility that must be taken critically to augment PV efficiency. On the whole, high concentrated PV has been pointed to be the most robust and result oriented PV. Keywords— Photovoltaic system components, solar panels, conventional PV, concentrated PV, high concentrated PV, solar tracking. I Introduction There are several photovoltaic (PV) systems on the market which range in sizes and functionality. The essence of the current paper is to look into PV efficiency. This issue has been necessitated given the increasing reliance on solar energy in various parts of the world, especially in areas where the use of hydroelectric sources no longer proves to be a viable choice [1]. Unlike before, solar energy was known to be a supplementary source of energy, which was used to support other major forms of energy provision. But an increasing demand for solar energy means that PV systems which are a major component of the functionality of solar energy be checked for its efficiency [2]. The paper therefore looks at solar energy from the perspective of PV systems, solar panels and the concept of solar tracking. II PHOTOVOLTAIC (pv) SYSTEMS COMPONENTS A PV system can be said to be a power system that is specially designed with the capabilities of supplying usable solar power through the mechanisms of photovoltaics [2]. Writing on photovoltaics, reference [1] explained it to be an energy conversion method where solar energy is changed into direct current electricity. Photovoltaics is enabled through the processes of several components, most of which are semiconducting materials that must have the power to demonstrate a photovoltaic effect [4]. There are several components that can be associated with PV systems. Some of these include solar array, battery, cabling, monitoring and metering, charge controller, solar trackers, and solar inverters [3]. Relating these components to the functionality of PV systems, it was stressed that the individual functions of the components when put together makes PV systems a centralised part of solar energy generation [3]. III HOW DO SOLAR PANELS WORK? The processes by which solar panels work can simply be said to be related or linked to the usual procedure for generating the flow of electricity. The only difference however has to do with the mechanisms that come in play to trigger this functioning. For example, solar panels are known to be photon permissible, allowing particles of light such as photons to trigger free motion of electrons as a way of causing the flow of electricity [5]. This means that until photons are captured, the function of solar panels to generate electricity cannot start. This activity of capturing photons is undertaken within the solar panel by photovoltaic cells which are the smallest units of operation within the panel. Several isolated photovoltaic cells must therefore come together to constitute the solar panel [6]. Even though the photovoltaic cells are technically referred to as the smallest unit within the panel, they are actually comprised of pairs of semi-conducting materials such as silicon or other materials. As semi-conducting materials, the splitting silicon works by establishing an electric field, which is used to create an electric charge within the cells and thus improve their ability to generate electricity [5]. Because of the useful presence of electrons to be knocked from electrons to generate the flow of electricity, the semi-conducting material such as silicon may be doped to get the addition of extra electrons, which are negatively charged and thus attract with the positive charge within the electric field generated to offset the electricity generation [4]. Apart from the electric field which turns the electrons into usable power called electricity, solar thermal and concentrated solar power have all been noted to be means by which electrons are turned into usable power within the solar panel. Fig. 1 PV components in an array [10] IV SOLAR PANEL MODELS There are several means by which a typical PV system or a solar panel may be put to work. This means constitutes the model of function. Three of these are discussed below. A Conventional PV As the name implies, conventional PV system are used largely following the traditional procedural functional activity of photovoltaics that have been discussed above. In this, three major solar panels may apply. These are monocrystalline silicon solar cells (mono-Si), polycrystalline silicon solar cells (p-Si) and thin-film solar panels (TFSC) [7]. Mono-Si often comprise of cylindrical silicon ingots, which have been associated with high efficiency [6]. They also take lesser space and have longer lifespan. P-Si on the other hand are made from raw silicon which is melted and fused into a square mold, a process that is not in line with the Czochralski process [7]. P-Si has the advantage of using less silicon when compared to mono-Si. Its efficiency is however measured to be only 13-16% [4]. Lastly, the TFSC are formed by the method of putting some thin layers of PV materials in substrates such as amorphous silicon, copper indium gallium selenide and cadmium telluride [8]. The efficiency of TFSC is said to be 7-13% [8]. TABLE I difference between conventional pv Mono-Si P-Si TFSC Single crystal cells are used Multiple crystal cells are used Chemical vapour deposition (CVD) are used Czochralski method is used in construction Czochralski method is not employed in construction Czochralski method is not employed in construction Efficiency ranges from 15-20% Efficiency ranges from 12-14% Efficiency ranges from 6-8% Most expensive type on the market Relatively cheap on the market Cheapest on the market Adopted from [7] Major advantage that can be associated with the use of conventional PV is the fact that consumers have the option of selecting from an array of alternatives that serve their needs most. There is however a disadvantage of relatively lower efficiencies [8]. Fig. 2 Types of Conventional PV [11] B Concentrated PC (CPV) In CPV, there is the use of optics including lenses and mirrors to concentrate large amount of sunlight unto relatively small area of a solar panel. The deviation from the norm therefore is that in CPV, it is not the natural state of the sunlight that gets unto the solar panel but that there is a third party, which is the concentrator [7]. Again, CPV does not require a wider area of the PV cells of the solar panel to function. As a result, it is possible to make use of several areas of the solar panel surface. Because of the function of active solar tracking that is used in CPV, their efficiency have been rated highly [8]. There is also a booster reflector which can be used to increase solar electric output to as high as 30% of what a conventional PV may offer [8]. Fig 3. Mechanism of CPV [12] The advantage with the use of CPV is the ability to control the movement of the sun towards a scope of usability that is most desired [5]. This means that utility is better guaranteed. There is however a disadvantage in the sense that the functionality of CPV may be hampered when solar tracking systems are not available. Particularly two-axes solar trackers [6]. C High-Concentrated PV (HCPV) As the name implies, HCPV is a type of CPV. This is because CPV comes in three different forms which are low, medium and high. What is unique or different about the HCPV is that it makes use of dish reflectors which intensifies the natural abilities of the sunlight by over 1000 folds [9]. Even though this is seen as a major advantage which helps in raising the efficiency of solar panels, thermal destruction can actually occur when high-capacity solar cells which can sink heat are not used [7]. It is also known that life expectancy losses can occur when effective cooling systems are not implemented into the HCPV to make them heat proof. But once all these measures are put in place, high current density can be achieved which ensures that the highest efficiency is achieved. Fig. 4 HCPV [12] This is the model that guarantees the highest form of efficiency and thus efficiency can be mentioned as an advantage. Its disadvantage however includes the fact that it requires a cooling system for the multijuction solar cells [6]. The absence of this cooling system can reduce efficiency and economy [7] V Solar tracking From all the discussions above, it would be agreed that until energy is captured from the sun unto a solar panel, the functions of photovoltaic systems cannot begin. This makes solar tracking very important in ensuring that payloads are better oriented towards the sun. By implication, through solar tracking, it is not it is not the sun’s energy that it directly oriented to the solar panel but then the payloads which functions as part of the solar panel. Because payloads are used differently in different solar panel models, the reliance on solar trackers differ from one model to another [9]. It is however common that CPVs would have the highest usage of solar trackers to make the optical components more functional [8]. Fig. 5 Single axis tracking system at work [13] VI Conclusions The ability of solar energy to be used as substantive source of energy in meeting the large energy gaps in industries and residential demands depends largely on photovoltaic efficiency. It has been noted in the paper however that photovoltaic efficiency is dependent on several factors and conditions including the solar panel model that is used. With advancement in technology, it is expected that the HCPV will further be equipped to become the most effective and efficient solar panel model. This is because the additional functionality of this model in doing more on a very small solar panel space means that greater capacity can be served with this model. What is more, it is strongly recommended that solar tracking will be used to improve the performance of solar payloads and solar panels as a whole. Once all these are followed, efficiency issues with the use of solar energy can be well catered for. Acknowledgment I am thankful to all people who have contributed to the success of my project. These include..... References [1] A. L. Darul’a and I. S. Marko. "Large scale integration of renewable electricity production into the grids". Journal of Eelectrical Engineering, 2007, 58.4, p. 58–60. [2] V. M. Andreev. Concentrator Photovoltaics. Berlin: Springer Verlag. 2007. [3] I. Luque-Heredia. The Sun Tracker in Concentrator Photovoltaics. Berlin: Springer Verlag. 2009. [4] W. D. Lubitz, "Effect of Manual Tilt Adjustments on Incident Irradiance on Fixed and Tracking Solar Panels", Applied Energy, Vol. 88, pp. 1710-1719, 2011 [5] C.F. Gay, and J.H. Wilson, and J.W. Yerkes. "Performance advantages of two-axis tracking for large flat-plate photovoltaic energy systems". Conf. Rec. IEEE Photovoltaic Spec. Conf, vol. 16: p. 1368. 1982 [6] R. Winston, J .C. Miñano and P. Benítez. Nonimaging Optics. London: Academic Press. 2005. [7] A. Al-Mohamad. 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