Figure 1 Structure of solar cell ("Rethinking energy: Towards," 2014) 4
Figure 2 Internal structure solar cell ("Rethinking energy: Towards," 2014) 5
Figure 3 Working principle of solar modules (Rongqiang) 5
Figure 4 Installation mechanism of photovoltaic cell to generate electricity (Rongqiang). 6
Figure 5 Electricity production by PV cell during 1999-2010 (Rongqiang) 6
Figure 6 Worldwide PV installation in the year 2005 (Rongqiang) 7
Figure 7 Classification PV cells, (http://sovoxglobal.com/cell_classification.html) 7
Figure 8 Internal structure of crystalline silicon cell 8
Figure 9 working phenomena of thin film cell 8
Solar Energy: Role of Photovoltaic Cells
Executive Summary
This report delineates solar energy with particular emphasizes on photovoltaic cells. Renewable sources of energy has been playing its role in shaping the energy supply. The development of technology has introduced variety of photovoltaic cells that make the solar energy as one of the major sources of energy. It has many benefits including being pollution free, helps in reducing greenhouse effect, cheap and can be easily convertible to any other form of energy like heat and electricity very comfortably. Photovoltaic energy cell is the mechanism to grasp solar energy and make it useable for multiple purposes. There are different types of cells available today including crystalline silicon, thin film, and so forth. Apart from generation of electricity photovoltaic cells are in use in different electronics equipment as calculators, digital watches and the likes. The efficiency of commercial solar energy system based on photovoltaic system is almost 16.5%. In the year 2005, the distribution of PV installation in Germany, Japan and United States is reported as 57%, 20% and 7% respectively on the globe. In addition, the installation price for 10 Kw, 10-100 kW and larger than 100 Kw is reported as $6.13, $5.62 and $4.87 per watt for a system during 1998-2011.This means that installation cost could be decreased by increase in capacity.
Solar Energy: Role of Photovoltaic Cells
Introduction
Renewable energy has remarkable positive undulation effect on society in the context of social, environmental and economic objectives. Solar energy that is one of the best renewable energy sources has holistic strategically potential to promote healthy environment and prosperity within a nation. Solar energy obtained from abundance sunlight have been playing significant role in shaping the energy supply, and few countries have been seeking remarkable growth opportunities in it. It is however expected that solar energy will become the core component of future energy sources. This is expected that the solar market will grow at tremendous rate in the coming few decades (Kühne & Aulich, 1992; "Rethinking energy: Towards," 2014)
Working of Photovoltaic
Normally, photovoltaic (PV) systems work on the availability of cells that is required to convert solar radiation into electrical energy. This cell could be of different shape and size as compared to the outer structure but internally, the cell is coated with semi-conducting material usually situated in the form of layers revolving the whole cell. When the light hits the cell or shines on the cell, there occurs an electric field causing a particular amount of electricity to flow through the cell. The rate of this electricity is dependent on the coming or shining of light that hits the cell. This means greater the intensity of light; greater there would be a flow of electricity going out from a cell. Figure 1 and Figure 2 are presenting the structure of solar cell. As the evaluation of electricity is greatly dependent on the hitting of light on the cell, therefore, a problem may occur in the absence or decreased availability of light during the day time. But, this is the advantage or feature of a photovoltaic cell that it can easily conduct electricity even without having a great amount of light entering or hitting upon the cell or whether there are any clouds.
Figure 1 Structure of solar cell ("Rethinking energy: Towards," 2014)
Figure 2 Internal structure solar cell ("Rethinking energy: Towards," 2014)
Photovoltaic system does not require any high medium of light or any bright light for its operation of generating electricity. The overall performance of this photovoltaic or solar cell is measured in efficiency, whether how much this system converts light energy coming at the cell and converting it to the electricity. Figure 4 displaying the installation mechanism of photovoltaic cell to generate electricity. The best example of the working of solar cell can be recognized by the functionality of commercial solar module. It has an efficiency approximately up to 16.5% that could be defined in other words to be over one-sixth of the hitting of a sunlight at the surface of the photovoltaic module. However, there are efforts in progress to develop an efficient and perfect model of photovoltaic cell that could convert less amount of sunlight. It means that could easily work at even dense sunlight and gives a huge amount of electricity at a proper way. The working principle of solar modules is shown in Figure 3.
Figure 3 Working principle of solar modules (Rongqiang)
The functionality of the solar system must be perfect within cost effective limits that be affordable to each and every person. In last 5 years, the use of solar energy created a great competition for other methods that were used in the recent times such as energy generated by coal, oil, wind and so forth. ("Rethinking energy: Towards," 2014). The electricity production by solar cell has been increased from 20 MW to 2000 MW during the period of 1999 to 2010 that is presented in Figure-5. The distribution of PV installation in the year 2005 was reported as 57%, 20% and 7% in Germany, Japan and United States respectively as presented in Figure 6 (Rongqiang).
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Figure 4 Installation mechanism of photovoltaic cell to generate electricity (Rongqiang).
Figure 5 Electricity production by PV cell during 1999-2010 (Rongqiang)
Figure 6 Worldwide PV installation in the year 2005 (Rongqiang)
Photovoltaic Technologies
The advancement of technology has facilitated in developing a large number of components that could be used for the making and preparation of these cells. The different advanced technologies could be used that are available within the market. Normally, Crystalline Silicon (monocrystalline or polycrystalline) as well as Thin Film are frequently used nowadays (Fthenakis, 2009). The flow diagram for the classification of solar cells is shown in Figure 7.
Figure 7 Classification PV cells, (http://sovoxglobal.com/cell_classification.html)
Crystalline Silicon is made up of different pieces or cuts driven out from a single piece of silicon (monocrystalline) or even from the blocks of silicon crystals also known as polycrystalline. Their efficiency varies from both 16% and 19%. As this product and its components are highly guaranteed for a better working or conversion of sunlight energy into electricity. Therefore, nearly 87% of today’s market is equipped with this component and there are different products are composed of these elements (Fthenakis, 2009; "Rethinking energy: Towards," 2014). The structure of crystalline Silicon is shown in Figure 8.
Figure 8 Internal structure of crystalline silicon cell
Source adopted: http://cleangreenenergyzone.com/crystalline-silicon-solar-cell-technology/
Thin Film is made up of depositing thin layers of photosensitive materials or components onto a low-cost material or component such as glass, stainless steel and even plastic. The use of such elements are considered low in cost, but their working capability is quite low related to another level of components. Some of them are used in Crystalline Silicon even, therefore, the overall efficiency of this Thin Film is greatly disturbed with the involvement of such components. Normally, the efficiency of this Thin Film is 10% to 15% (Fthenakis, 2009).The working of thin film PV cell is presented in Figure 9.
Figure 9 working phenomena of thin film cell
Source adopted: http://science.howstuffworks.com/environmental/green-science/thin-film-solar-cell.htm
These were the two elements that are mostly used nowadays due to their costs (in which Thin Film is even more affordable) and also, due to their better working. But, there is a variety of other products or components that could be used as a technology for the development of photovoltaic cell. Among other technologies, one is concentrated photovoltaic. It is used to perform with a concentrated amount of sunlight using a particular lens for the purpose of gathering sunlight, as well as the conversion of sunlight into electrical energy. Moreover, flexible cells are used having a technology similar to that of thin film but with such advance equipment used in it, the overall range of applications is increased greatly (Fthenakis, 2009).
Photovoltaic Applications
As today's world is suffering greatly from the loss of energy sources that are in great danger, and it is on the increase with the passage of time due to the extra loss of these energy resources. Therefore, a large number of organizations, companies and even families have started to give much of their interest and concentration to install such equipment that could easily fulfill the requirement of electricity at any time. Photovoltaic cells could be of different types and could be used at different locations. They are either fitted at the roofs or be integrated into buildings envelope or could be fitted within the ground basements. The uses of these photovoltaic cells are huge. They could be used in houses, organizations or commercial areas, and even in power plants. These photovoltaic cells could be connected to the grid, or it could be used without any grid (Tsoutsos et.al, 2005).
Solar Cells at the Top of Roofs: These photovoltaic cells are used at different locations. Either at the top of a roof or even fitted during the installation of wires or tiles or even installed directly at the ground level of the home. Photovoltaic cells are used with two methods. Either, connected to the grid (element that provides electricity resource) or even without any source of grid. Photovoltaic connected to the grid results in different advantages. This grid electricity will provide energy or power to these solar cells that would help them to store it. This stored energy could be used at such scenario when there is dense amount of sunlight available (Tsoutsos et.al, 2005).
Photovoltaic Cells Connected to Grids: Examples of such form of photovoltaic cells could be easily observed in mega malls, local residential areas (here these photovoltaic cells are located at the ground level. It can also be observed at airport terminals or even railway stations where large amount of electrical energy is required to process daily life processes. Energy from grids can be stored within the photovoltaic cells and energy from the sunlight could be stored, as well giving these solar cells dual feature of storing and using of light energy at the same time. Similarly, these solar cells could be used even without the plantation of these cells with any grid. Such examples could be easily observed everywhere. Either at large commercial or residential areas (Tsoutsos et.al, 2005).
Consumer’s Goods: Other important examples of these photovoltaic cells the goods used by the human beings as watches, calculators, toys, battery charges and so forth (Tsoutsos et.al, 2005).
Benefits & Drawbacks of Photovoltaic Technology
Benefits
There are marvelous applications and advantages of these photovoltaic cells that could be used everywhere. Some of them are discussed below:
- Major benefit of these solar or PV cells is to provide a clean electrical energy. With the evolvement of this solar energy, there won’t be any amount of harmful gases that could be easily seen with the evolvement of normal electrical energy.
- This energy is mostly adopted by nature, therefore, considered as free.
- If there is any sunlight available at the sky, one can get electrical energy anytime or anywhere.
- These cells are useful at those areas where there is a network distribution of energy among different areas.
- The overall cost that matters while the making and purchasing of these solar cells is quite low and is assumed to be much lower in future days. Their use is highly secured related to the matters concerning environmental issues apart from low cost that could easily attract everyone.
- Aspects related to the maintenance and operational cost are considered to be low or even negligible as compared to other heavy machinery used for an alternate way of generating electrical energy.
- These solar cells work calmly having no issue of noise pollution. Therefore, these are considered to be the best option for such areas where a complete silence must.
- During summer days, the heat of sunlight is quite strong. With such strong sunlight, there occurs a great level of heat among different areas of the world. Therefore, at those areas, these solar cells play a vital role by getting such high-intensity sun rays and converting them to electrical energy.
- These solar cells can be easily installed at any position with no issue of changing the overall decoration of home (Wild-Scholten & Alsema. 2004).
Drawbacks
Greenhouse Emissions
Research has proved that photovoltaic technology delivers clean and efficient electricity, but there could be some emissions in large scales that is the result of abnormal operations resulting in hazardous situations to the environment. Photovoltaic cells used these days have a higher rate of greenhouse emissions as compared to nuclear and wind energy. It has also been observed that it has higher gas emissions if installed in low irrigation areas. Greenhouse emission these days is in the range of 25-32g/kWh, and it may decrease to 15g/kWh in future. Thus, it has been expected that photovoltaic energy may get mature with the time as low carbon energy has done for various applications (Chiabrando, et.al, 2009).
Reduction in the Use of Non-Renewable Energy
Renewable source of energy never gets depleted like wind and solar energy. There is no doubt that since 1990, the consumption of fossil fuel has doubled in last 20 years. Thus, the amount of fossil fuel required to generate electricity may also get reduced with the deployment of photovoltaic technology. The power generation from photovoltaic technology works the similar way as from the fossil fuel. Despite using steam that is generated from the burning of fossil fuel, this steam is produced from the heat collected from sunlight. The implementation of PV technology in larger scales may result in a considerable reduction of emissions. It is estimated about 2 tons per person per year by assuming a global population being 7 billion (Bader, Scheidegger & Real, 2006).
Microclimate Change
During normal duration of operation, the temperature attained by PV cells is about 700 degrees Celsius due to the infrared components in solar radiation resulting in the heating of surrounding areas. This temperature is reached by a single module with the PV cell because the darker surfaces are receiving the same amount of heat. This is the reason the photovoltaic cells are equipped with proper ventilation to avoid overheating (Chiabrando, et.al, 2009).
Photovoltaic use in UAE
United Arab Emirates (UAE) is geographically located in the Arabian Gulf. After Dubai, Abu Dhabi is considered as the second most important location within the Arabs states that play a vital role in the context of economic and natural resources. This is one of the most significant places or location related to reservoirs of oil. The overall usage of electrical energy comes from the sources such as fossil fuel where there is a great amount of the availability of highly intense sunlight that could be converted to electrical energy. Having the great availability of sunlight, Abu Dhabi, one of the most important Emirates of UAE has started such projects to develop renewable energy technology. It ca provide better advancement applied to their power grids. Over the last ten years, the Abu Dhabi government is consistently progressing to search or find such a way to develop a renewable energy resources that could be used for a longer period. One of this plans is wind energy as well. But, after spending some time on this project without significant outcome, they decided working plans to develop solar energy generation plants. Abu Dhabi, a place having an easy providence of sunlight at various places such as residential areas, commercial areas, office buildings, agricultural areas, domestic and places of transportation. This solar energy is planned to get electrical energy. There are three ways of producing electricity through sunlight:
- Photovoltaic Cell (containing crystalline cells).
- Solar Thermal Electricity.
- Hybrid PV/Thermal Electricity (PV-T).
One of the important method of getting sun rays and converting them to electricity is through concentrating solar power technology having mirrors to collect and convert sunlight into electricity. Due to such advance technologies used in Abu Dhabi, the wastage of oil is decreased. The overall costs for the electricity is reduced, as well. Reduction in noise and gas occurred, as well. Moreover, a sufficient amount of electricity is available with these solar cells. Installation of these cells is quite simple and traditional (James et.al, 2012).
Residential and Commercial Prices of PV
According to study reports, installation price has been decreased with increase in capacity during the period of 1998 to 2011. The installation price for 10 Kw, 10-100 kW and larger than 100 Kw is reported as $6.13, $5.62 and $4.87 per watt for a system respectively during (Feldman et.al, 2012).
Conclusion
Solar energy is emerged as an environment friendly source of energy. Although it some pros and cons but advancement of technology has made it a useful and economical source of energy. Deferent type of solar panel and PV cells are available including crystalline Silicon, thin film and so forth. Many countries are giving significant attention for development this technology and its use has been increased manifold in the last decade. UAE having abundance of sunlight during most of the year increased research and development in a recent past. This expected that its role would further increase in the future on the globe.
References
Bader, H.,Scheidegger,R. & Real,M. (2006). "Global renewable energies: a dynamic study of implementation time, greenhouse gas emissions and financial needs," Clean Technologies and Environmental Policy, Vol.8, No.3, pp.159-193
Chiabrando, R., Fabrizio, E., & Garnero, G, (2009). "The territorial and landscape impacts of photovoltaic systems: Definition of impacts and assessment of the glare risk," Renewable and Sustainable Energy Reviews, Vol.13, No.9, pp. 2441-2451
Feldman, D., Barbose, G., Margolis, R., Wiser, R., Darghouth, N. & Alan Goodrich, A. (2012), “Photovoltaic (PV) Pricing Trends: Historical, Recent and Near Term Projections”, Retrieved October 19, 2014 from http://www.nrel.gov/docs/fy13osti/56776.pdf
Fthenakis, V, (2009). "Sustainability of photovoltaic: The case for thin-film solar cells," Renewable and Sustainable Energy Reviews, Vol.13, No.9, pp. 2746-2750
International Renewable Energy Agency, (2014).”Rethinking energy: Towards a new power system”. Retrieved October 19, 2014 from website: http://www.irena.org/rethinking/rethinking_fullreport_web.pdf
James, T., Goodrich, A., Woodhouse,M.,Margolis,R. & Ong, S. (2012).“Building-Integrated Photovoltaic (BIPV) in the Residential Section: An Analysis of Installed Rooftop Prices”, World Renewable Energy Forum, Retrieved October 19, 2014 from http://www.nrel.gov/docs/fy12osti/55027.pdf
Kühne, H. & Aulich, H. (1992). "Assessment of present and future potential," Energy Policy, Vol.20, No.9, pp. 847-860
Rongqiang, C. Solar Energy Inst., (n.d.). “Current status and future development of photovoltaics.” Retrieved October 19, 2014from website: http://www.nacsa.com/archives/files/Solar_Event_Cui_Rongqiang.pdf
Tsoutsos, T., Frantzeskaki, N. & Gekas V, (2005). "Environmental impacts from the solar energy technologies," Energy Policy, Vol.33, No.3, pp. 289-296
Wild-Scholten, D.M. & Alsema, E, 2004, “Towards cleaner solar PV: Environmental and health impacts of crystalline silicon photovoltaic,” Refocus, Vol.5, N o.5, pp. 46-49
