Environmental Impacts From the Solar Energy System

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  See discussions, stats, and author profiles for this publication at: Environmental Impacts from the Solar Energy Systems  Article   in  Energy Sources Part A Recovery Utilization and Environmental Effects · December 2008 DOI: 10.1080/15567030701512733 CITATIONS 22 READS 11,535 3 authors , including: Some of the authors of this publication are also working on these related projects: ENERJ İ  UYGULAMALARINDA KULLANILAN NANOAKI Ş KANLARIN ISIL ÖZEL İ KLER İ   View projectAir-conditioning with desiccant cooling   View projectHuseyin GunerhanEge University 35   PUBLICATIONS   516   CITATIONS   SEE PROFILE Arif HepbasliYasar University 129   PUBLICATIONS   2,913   CITATIONS   SEE PROFILE All content following this page was uploaded by Huseyin Gunerhan on 31 July 2014. The user has requested enhancement of the downloaded file.   Energy Sources, Part A , 31:131–138, 2009Copyright © Taylor & Francis Group, LLCISSN: 1556-7036 print/1556-7230 onlineDOI: 10.1080/15567030701512733 Environmental Impacts from theSolar Energy Systems H. GUNERHAN, 1 A. HEPBASLI, 1 and U. GIRESUNLU 2 1 Mechanical Engineering Department, Faculty of Engineering, Ege University,Bornova, Izmir, Turkey 2 M.Sc. Student in Center for Environmental Studies, Ege University, Bornova,Izmir, Turkey Abstract  Solar energy technologies offer a clean, renewable, and domestic energysource, and are essential components of a sustainable energy future. Solar energysystems (i.e., photovoltaics, solar thermal) provide significant environmental benefitsin comparison to the conventional energy sources. It is known that these systemshave some minor negative impacts on the environment during their production and operation. This study presents an overview of some positive impacts of the solar energy systems and negative impacts covered by environmental impact assessment. Keywords  environmental impact, renewable energy, solar energy systems Introduction Extensive fossil fuel consumption in almost all human activities has led to some undesir-able phenomena such as atmospheric and environmental pollutions, which have not beenexperienced before in known human history. Consequently, global warming, greenhouseaffect, climate change, ozone layer depletion, and acid rain terminologies started toappear in the literature frequently. Since 1970, it has been understood scientifically byexperiments and researches that these phenomena are closely related to fossil fuel usesbecause they emit greenhouse gases such as carbon dioxide (CO 2 ) and methane (CH 4 ),which hinder the long-wave terrestrial radiation escape into space, and, consequently, theearth troposphere becomes warmer. In order to avoid further impacts of these phenomena,the two concentrative alternatives are either to improve the fossil fuel quality withreductions in their harmful emissions intothe atmosphere or, more significantly, to replacefossil fuel usage as much as possible with environmentally friendly, clean, and renewableenergy sources. Among these sources, solar energy comes at the top of the list due to itsabundance and more even distribution in nature than any other renewable energy type,such as wind, geothermal, hydro, wave, and tidal energies (Sen, 2004).Solar energy technologies are essential components of a sustainable energy future.Energy from fossil fuels may be inexpensive and assurances may have been given of theplentiful supplies of petroleum and other fossil fuels, but these fuels are finite in natureand a major source of greenhouse gas emissions (IEA, 2002). Address correspondence to Dr. Arif Hepbasli, Mechanical Engineering Department, Facultyof Engineering, Ege University, 35100 Bornova, Izmir, Turkey. E-mail: 131  132 H. Gunerhan et al. When energy demands increase, energy production and its negative impacts on theenvironment increase as well. As a result, environmental pollution became a globalthreat. Therefore, the importance of unpolluted energy sources such as solar energyhas increased in recent years. But even solar energy technologies have introduced somelevel of environmental effects. In this study, these effects will be discussed and necessaryconditions to avoid this environmental effects will be investigated. Solar Energy Solar energy has been used since time immemorial to dry agricultural products, to providespace heat in cold seasons, or to create ventilation in homes, applications which are stillused in many developing countries. More than 2,000 years ago, Heron of Alexandriaconstructed a simple water pump driven by solar energy, and in 214 B.C., Archimedes of Syracuse used concentrating solar mirrors to set fire to Roman ships (Vanderhulst et al.,2006).The sun showers the earth with a nearly infinite supply of energy. Each day moresolar energy falls to the earth than the total amount of energy the planet’s 5.9 billioninhabitants would consume in 27 years. While it is neither possible nor necessary to usebut a small portion of this energy, the potential of solar energy was hardly tapped. Only inthe last few decades, when growing energy demands, increasing environmental problems,and declining fossil fuel resources made us look to alternative energy options, has theattention been focused on truly exploiting this tremendous resource (NREL, 2002).The sun is the main energy source of the earth. Almost all of the natural energysources (excluding nuclear and geothermal energy) on the earth are a converted form of solar energy. For example, water cycle, wind cycle, and other energy systems requiresolar energy as the primary driving source. Due to being a relatively environmentallyfriendly energy form, solar energy systems have covered a wide range of applications inthe recent years. It is also a relatively infinite energy source compared to fossil energyforms (Atagunduz, 1989). Solar Energy Systems Solar Collectors There are basically three types of collectors: flat-plate, evacuated-tube, and concentrating.Flat-plate collectors are the most commonly used types.1. Flat-plate collectors: The basic working principle of these collectors is based onthe conversion of the solar energy to the thermal energy. Flat-plate collectors aremade of a glass cover as a transparent material, an absorbing plate, and a body.Radiation passed through the glass plate is absorbed by the solar plate. This plateis covered with paints or special surfaces for high absorbing properties. Almost90% of the solar radiation felt on the surface are absorbed by these plates. Theremaining are radiated back as thermal radiation and convective losses.2. Concentrating collectors: These collectors are used to obtain higher enthalpywater or other processing fluids. Usually temperatures above 140 ı C cannot beobtained by flat-plate solar collectors, and concentrating collectors are utilizedabove 140 ı C. Concentrating collectors are made of two components, namely, theoptical system and the receiver. The function of the optical system is to direct   Environmental Impacts from the Solar Energy Systems 133 and focus the solar rays to the receiver. The function of the receiver is to absorbthe solar rays and convert it to the thermal energy. The receiver is made of absorber, protection, and isolation parts. The ratio of open space for solar rays tothe receiver space where the solar rays will be absorbed is called the condensingratio. Concentrating collectors can be classified according to their condensingratios (Atagunduz, 1989):   flat receiver and flat reflectors   pipe or spherical-shaped receiver and parabolic reflectors   pipe or spherical-shaped receiver and flat, moving reflectors in separaterows   pipe or spherical-shaped receiver and flat, single-moving reflectors.3. Evacuated-tube collectors: Evacuated tubes are the absorber of the solar waterheater. They absorb solar energy converting it into heat for use in water heating.Evacuated tubes have already been used for years in Germany, Canada, China,and the UK. There are several types of evacuated tubes in use in the solar industry(Apricus, 2006). Solar Heating 1. Active heating systems: There are examples of solar active heating systems, likeheating the water by solar collectors and the transmission of heated water to theexisting central heating installation, and thus the transportation of heated air forneeded areas.2. Passive heating systems: Passive heating systems using solar energy operate asa ray trap. Solar radiation enters a covered volume through glass and similartransparent materials and is absorbed by some absorbing surfaces. The heatedsurfaces radiate energy by radiation, but these heat rays cannot pass through theglass surface where sun rays can get through. Thus, the heat energy carried bythe solar rays is kept inside (Atagunduz, 1989).  Drying Using Solar Energy The drying process can be defined as the removal of water from a solid substance byevaporation. When the energy needed by this process is supplied by solar energy, this iscalled “drying using solar energy.”Solar drying is one of the oldest solar applications of mankind. The simplest solardryer, at zero cost, is a black asphalt road on which people spread their grains to increasethe natural (solar) drying process (NREL, 2002).  Electrical Energy Converters 1. Solar cells: Solar cells are systems that convert solar rays to electrical power.Radiation energy radiated as electromagnetic waves that reach the surfaces of the solar cells cause a photo-electromotive power with the help of the forming of electron/deflection pairs during the P-N transition of the semi-conductive crystals.These pairs get separated in the electrical area during the P-N transition and thuscause a current in the circuit that was connected to the semi-conductive crystal.
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