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102-527: Solar water disinfection is usually accomplished using some mix of electricity generated by photovoltaics panels (solar PV), heat ( solar thermal ), and solar ultraviolet light collection. Solar disinfection using the effects of electricity generated by photovoltaics typically uses an electric current to deliver electrolytic processes which disinfect water, for example by generating oxidative free radicals which kill pathogens by damaging their chemical structure. A second approach uses stored solar electricity from

204-752: A DC clamp meter or shunt and logged, graphed, or charted with a chart recorder or data logger. For optimum performance, a solar panel needs to be made of similar modules oriented in the same direction perpendicular to direct sunlight. Bypass diodes are used to circumvent broken or shaded panels and optimize output. These bypass diodes are usually placed along groups of solar cells to create a continuous flow. Electrical characteristics include nominal power (P MAX , measured in W ), open-circuit voltage (V OC ), short-circuit current (I SC , measured in amperes ), maximum power voltage (V MPP ), maximum power current (I MPP ), peak power ( watt-peak , W p ), and module efficiency (%). Open-circuit voltage or V OC

306-592: A battery, and operates at night or at low light levels to power an ultraviolet lamp to perform secondary solar ultraviolet water disinfection. Solar thermal water disinfection uses heat from the sun to heat water to 70–100 °C for a short period of time. A number of approaches exist. Solar heat collectors can have lenses in front of them, or use reflectors. They may also use varying levels of insulation or glazing. In addition, some solar thermal water disinfection processes are batch-based, while others (through-flow solar thermal disinfection) operate almost continuously while

408-549: A factor of 4 between 2004 and 2011. Module prices dropped by about 90% over the 2010s. In 2022, worldwide installed PV capacity increased to more than 1 terawatt (TW) covering nearly two percent of global electricity demand . After hydro and wind powers , PV is the third renewable energy source in terms of global capacity. In 2022, the International Energy Agency expected a growth by over 1 TW from 2022 to 2027. In some instances, PV has offered

510-910: A fraction of the emissions caused by fossil fuels . Photovoltaic systems have long been used in specialized applications as stand-alone installations and grid-connected PV systems have been in use since the 1990s. Photovoltaic modules were first mass-produced in 2000, when the German government funded a one hundred thousand roof program. Decreasing costs has allowed PV to grow as an energy source. This has been partially driven by massive Chinese government investment in developing solar production capacity since 2000, and achieving economies of scale . Improvements in manufacturing technology and efficiency have also led to decreasing costs. Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have supported solar PV installations in many countries. Panel prices dropped by

612-731: A general lack of sanitation and hygiene. Studies on the reduction of diarrhea among SODIS users show reduction values of 30–80%. The effectiveness of the SODIS was first discovered by Aftim Acra, of the American University of Beirut in the early 1980s. Follow-up was conducted by the research groups of Martin Wegelin at the Swiss Federal Institute of Aquatic Science and Technology (EAWAG) and Kevin McGuigan at

714-474: A light beam through a column of water should be calibrated and reported in JTUs. The propensity of particles to scatter a light beam focused on them is now considered a more meaningful measure of turbidity in water. Turbidity measured this way uses an instrument called a nephelometer with the detector set up to the side of the light beam. More light reaches the detector if there are many small particles scattering

816-476: A number of chemical reagents that are available for treating turbidity. Reagents that are available for treating turbidity include aluminium sulfate or alum (Al 2 (SO 4 ) 3 ·nH 2 O), ferric chloride (FeCl 3 ), gypsum (CaSO 4 ·2H 2 O), poly- aluminium chloride , long chain acrylamide -based polymers and numerous proprietary reagents. The water chemistry must be carefully considered when chemical dosing as some reagents, such as alum, will alter

918-449: A number of solar cells containing a semiconductor material. Copper solar cables connect modules (module cable), arrays (array cable), and sub-fields. Because of the growing demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years. Cells require protection from the environment and are usually packaged tightly in solar modules. Photovoltaic module power

1020-586: A number of solar cells , which generate electrical power. PV installations may be ground-mounted, rooftop-mounted, wall-mounted or floating. The mount may be fixed or use a solar tracker to follow the sun across the sky. Photovoltaic technology helps to mitigate climate change because it emits much less carbon dioxide than fossil fuels . Solar PV has specific advantages as an energy source: once installed, its operation does not generate any pollution or any greenhouse gas emissions ; it shows scalability in respect of power needs and silicon has large availability in

1122-878: A panel can be expected to produce 400  kWh of energy per year. However, in Michigan, which receives only 1400 kWh/m /year, annual energy yield will drop to 280 kWh for the same panel. At more northerly European latitudes, yields are significantly lower: 175 kWh annual energy yield in southern England under the same conditions. Several factors affect a cell's conversion efficiency, including its reflectance , thermodynamic efficiency , charge carrier separation efficiency, charge carrier collection efficiency and conduction efficiency values. Because these parameters can be difficult to measure directly, other parameters are measured instead, including quantum efficiency , open-circuit voltage (V OC ) ratio, and § Fill factor . Reflectance losses are accounted for by

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1224-565: A preference for the SODIS method over boiling or other basic water treatment methods. A very simple solar water purifier for rural households has been developed which uses 4 layers of saree cloth and solar tubular collectors to remove all coliforms. In July 2020 researchers reported the development of a reusable aluminium surface for efficient solar-based water sanitation to below the WHO and EPA standards for drinkable water. The Swiss Federal Institute of Aquatic Science and Technology (EAWAG), through

1326-578: A rather large amount of uncertainty. The values of human labor and water consumption, for example, are not precisely assessed due to the lack of systematic and accurate analyses in the scientific literature. One difficulty in determining effects due to PV is to determine if the wastes are released to the air, water, or soil during the manufacturing phase. Life-cycle assessments , which look at all different environment effects ranging from global warming potential , pollution, water depletion and others, are unavailable for PV. Instead, studies have tried to estimate

1428-480: A reagent, generally a flocculant , evenly dispensed over the surface of the body of water. The flocs then settle at the bottom of the water body where they remain or are removed when the water body is drained. This method is commonly used at coal mines and coal loading facilities where stormwater collection ponds have seasonal issues with turbidity. A number of companies offer portable treatment systems for in-situ water treatment or direct dosing of reagents. There are

1530-520: A similar program with 539 residential PV systems installed. Since, many countries have continued to produce and finance PV systems in an exponential speed. Photovoltaics are best known as a method for generating electric power by using solar cells to convert energy from the sun into a flow of electrons by the photovoltaic effect . Solar cells produce direct current electricity from sunlight which can be used to power equipment or to recharge batteries . The first practical application of photovoltaics

1632-574: A simple rooftop system, some 90% of the energy cost is from silicon, with the remainder coming from the inverters and module frame. In an analysis by Alsema et al . from 1998, the energy payback time was higher than 10 years for the former system in 1997, while for a standard rooftop system the EPBT was calculated as between 3.5 and 8 years. The EPBT relates closely to the concepts of net energy gain (NEG) and energy returned on energy invested (EROI). They are both used in energy economics and refer to

1734-677: A structure of front electrode, anti-reflection film, n-layer, p-layer, and back electrode, with the sun hitting the front electrode. EPBT ranges from 1.7 to 2.7 years. The cradle to gate of CO 2 -eq/kWh ranges from 37.3 to 72.2 grams when installed in Southern Europe. Techniques to produce multi-crystalline silicon (multi-si) photovoltaic cells are simpler and cheaper than mono-si, however tend to make less efficient cells, an average of 13.2%. EPBT ranges from 1.5 to 2.6 years. The cradle to gate of CO 2 -eq/kWh ranges from 28.5 to 69 grams when installed in Southern Europe. Assuming that

1836-422: A theoretical 28% efficient device, found that, compared to monocrystalline Si, the environmental impacts from 1% SWCNT was ~18 times higher due mainly to the short lifetime of three years. Turbid Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye , similar to smoke in air . The measurement of turbidity

1938-400: A turbidity reading), a correlation between turbidity and total suspended solids (TSS) is somewhat unusual for each location or situation. Turbidity in lakes, reservoirs, channels, and the ocean can be measured using a Secchi disk . This black and white disk is lowered into the water until it can no longer be seen; the depth (Secchi depth) is then recorded as a measure of the transparency of

2040-409: Is a key test of both water clarity and water quality . Fluids can contain suspended solid matter consisting of particles of many different sizes. While some suspended material will be large enough and heavy enough to settle rapidly to the bottom of the container if a liquid sample is left to stand (the settable solids ), very small particles will settle only very slowly or not at all if the sample

2142-518: Is a limited amount of shade. One of the most important things to consider for public health workers reaching out to communities in need of suitable, cost efficient, and sustainable water treatment methods is teaching the importance of water quality in the context of health promotion and disease prevention while educating about the methods themselves. Although skepticism has posed a challenge in some communities to adopt SODIS and other household water treatment methods for daily use, disseminating knowledge on

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2244-401: Is around 18 grams (cradle to gate). CdTe has the fastest EPBT of all commercial PV technologies, which varies between 0.3 and 1.2 years. Third-generation PVs are designed to combine the advantages of both the first and second generation devices and they do not have Shockley-Queisser limit , a theoretical limit for first and second generation PV cells. The thickness of a third generation device

2346-502: Is assumed this is because of the improved surface area to volume ratio in SODIS bags. In remote regions plastic bottles are not locally available and need to be shipped in from urban centers which may be expensive and inefficient since bottles cannot be packed very tightly. Bags can be packed more densely than bottles, and can be shipped at lower cost, representing an economically preferable alternative to SODIS bottles in remote communities. The disadvantages of using bags are that they can give

2448-422: Is available, SODIS is a more economical and environmentally friendly option. The application of SODIS is limited if enough bottles are not available, or if the water is highly turbid . In fact, if the water is highly turbid, SODIS cannot be used alone; additional filtering is then necessary. A basic field test to determine if the water is too turbid for the SODIS method to work properly is the newspaper test. For

2550-459: Is commonly treated using a settling or filtration process, or both settling and filtration. Depending on the application, flocculants may be dosed into the water stream to increase the effectiveness of the settling or filtration process. Potable water treatment and municipal wastewater plants often remove turbidity with a combination of settling tanks, granular media filtration , and clarifiers . In-situ water treatment or direct dosing for

2652-529: Is converted to a turbidity. Open source hardware has been developed following the ISO 7027 method to measure turbidity reliably using an Arduino microcontroller and inexpensive LEDs . There are several practical ways of checking water quality, the most direct being some measure of attenuation (that is, reduction in strength) of light as it passes through a sample column of water. The alternatively used Jackson Candle method (units: Jackson Turbidity Unit or JTU )

2754-435: Is due to its exposure to solar radiation as well as other external conditions. The degradation index, which is defined as the annual percentage of output power loss, is a key factor in determining the long-term production of a photovoltaic plant. To estimate this degradation, the percentage of decrease associated with each of the electrical parameters. The individual degradation of a photovoltaic module can significantly influence

2856-425: Is essentially the inverse measure of the length of a column of water needed to completely obscure a candle flame viewed through it. The more water needed (the longer the water column), the clearer the water. Of course water alone produces some attenuation, and any substances dissolved in the water that produce color can attenuate some wavelengths. Modern instruments do not use candles, but this approach of attenuation of

2958-468: Is less than 1 μm. Two new promising thin film technologies are copper zinc tin sulfide (Cu 2 ZnSnS 4 or CZTS), zinc phosphide (Zn 3 P 2 ) and single-walled carbon nano-tubes (SWCNT). These thin films are currently only produced in the lab but may be commercialized in the future. The manufacturing of CZTS and (Zn 3 P 2 ) processes are expected to be similar to those of current thin film technologies of CIGS and CdTe, respectively. While

3060-456: Is measured under standard test conditions (STC) in "W p " ( watts peak ). The actual power output at a particular place may be less than or greater than this rated value, depending on geographical location, time of day, weather conditions, and other factors. Solar photovoltaic array capacity factors are typically under 25% when not coupled with storage, which is lower than many other industrial sources of electricity. Solar-cell efficiency

3162-472: Is mostly widely used in Europe, whereas NTU is mostly widely used in the U.S. The ISO 7027 provides the method in water quality for the determination of turbidity. It is used to determine the concentration of suspended particles in a sample of water by measuring the incident light scattered at right angles from the sample. The scattered light is captured by a photodiode , which produces an electronic signal that

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3264-645: Is needed in order to support certain species, such as to protect juvenile fish from predators. For most mangroves along the eastern coast of Australia , in particular Moreton Bay , turbidity levels as high as 600 Nephelometric Turbidity Units (NTU) are needed for proper ecosystem health. The measurement of turbidity is a key test of both water clarity and water quality . There are two standard units for reporting turbidity: Formazin Nephelometric Units (FNU) from ISO 7027 and Nephelometric Turbidity Units (NTU) from USEPA Method 180.1. ISO 7027 and FNU

3366-459: Is observed (which can last several months and up to two years), followed by a later stage in which the degradation stabilizes, being then comparable to that of crystalline silicon. Strong seasonal variations are also observed in such thin-film technologies because the influence of the solar spectrum is much greater. For example, for modules of amorphous silicon, micromorphic silicon or cadmium telluride, we are talking about annual degradation rates for

3468-402: Is processed from mined quartz until it is very pure (semi-conductor grade). This is melted down when small amounts of boron , a group III element, are added to make a p-type semiconductor rich in electron holes. Typically using a seed crystal, an ingot of this solution is grown from the liquid polycrystalline. The ingot may also be cast in a mold. Wafers of this semiconductor material are cut from

3570-997: Is regularly agitated or the particles are colloidal . These small solid particles cause the liquid to appear turbid. Turbidity (or haze) is also applied to transparent solids such as glass or plastic. In plastic production, haze is defined as the percentage of light that is deflected more than 2.5° from the incoming light direction. Turbidity in open water may be caused by growth of phytoplankton . Human activities that disturb land, such as construction , mining and agriculture , can lead to high sediment levels entering water bodies during rain storms due to storm water runoff . Areas prone to high bank erosion rates as well as urbanized areas also contribute large amounts of turbidity to nearby waters, through stormwater pollution from paved surfaces such as roads, bridges, parking lots and airports. Some industries such as quarrying , mining and coal recovery can generate very high levels of turbidity from colloidal rock particles. In drinking water,

3672-535: Is the maximum voltage the module can produce when not connected to an electrical circuit or system. V OC can be measured with a voltmeter directly on an illuminated module's terminals or on its disconnected cable. The peak power rating, W p , is the maximum output under standard test conditions (not the maximum possible output). Typical modules, which could measure approximately 1 by 2 metres (3 ft × 7 ft), will be rated from as low as 75 W to as high as 600 W, depending on their efficiency. At

3774-433: Is the portion of energy in the form of sunlight that can be converted via photovoltaics into electricity by the solar cell . The efficiency of the solar cells used in a photovoltaic system , in combination with latitude and climate, determines the annual energy output of the system. For example, a solar panel with 20% efficiency and an area of 1 m will produce 200 kWh/yr at Standard Test Conditions if exposed to

3876-815: The Greek φῶς ( phōs ) meaning "light", and from "volt", the unit of electromotive force, the volt , which in turn comes from the last name of the Italian physicist Alessandro Volta , inventor of the battery ( electrochemical cell ). The term "photovoltaic" has been in use in English since 1849. In 1989, the German Research Ministry initiated the first ever program to finance PV roofs (2200 roofs). A program led by Walter Sandtner in Bonn, Germany. In 1994, Japan followed in their footsteps and conducted

3978-733: The Royal College of Surgeons in Ireland . Clinical control trials were pioneered by Ronan Conroy of the RCSI team in collaboration with Michael Elmore-Meegan . A joint research project on SODIS was implemented by the following institutions: The project embarked on a multi-country study including study areas in Zimbabwe , South Africa and Kenya . Other developments include a continuous flow disinfection unit and solar disinfection with titanium dioxide film over glass cylinders, which prevents

4080-611: The SOLAQUA Foundation , several Lions Clubs , Rotary Clubs, Migros , and the Michel Comte Water Foundation. SODIS has also been applied in several communities in Brazil, one of them being Prainha do Canto Verde , Beberibe west of Fortaleza . Villagers there using the SODIS method have been quite successful, since the temperature during the day can go beyond 40 °C (104 °F) and there

4182-510: The World Health Organization , more than two million people per year die of preventable water-borne diseases, and one billion people lack access to a source of improved drinking water. It has been shown that the SODIS method (and other methods of household water treatment) can very effectively remove pathogenic contamination from the water. However, infectious diseases are also transmitted through other pathways, i.e. due to

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4284-630: The Department of Water and Sanitation in Developing Countries (Sandec), coordinates SODIS promotion projects in 33 countries including Bhutan, Bolivia, Burkina Faso, Cambodia, Cameroon, DR Congo, Ecuador, El Salvador, Ethiopia, Ghana, Guatemala, Guinea, Honduras, India, Indonesia, Kenya, Laos, Malawi, Mozambique, Nepal, Nicaragua, Pakistan, Perú, Philippines, Senegal, Sierra Leone, Sri Lanka, Togo, Uganda, Uzbekistan, Vietnam, Zambia, and Zimbabwe. SODIS projects are funded by, among others,

4386-682: The Earth's crust, although other materials required in PV system manufacture such as silver may constrain further growth in the technology. Other major constraints identified include competition for land use. The use of PV as a main source requires energy storage systems or global distribution by high-voltage direct current power lines causing additional costs, and also has a number of other specific disadvantages such as variable power generation which have to be balanced. Production and installation does cause some pollution and greenhouse gas emissions , though only

4488-554: The Linke turbidity factor (T L ). Governments have set standards on the allowable turbidity in drinking water. In the United States, public water systems that use conventional or direct filtration methods must not have a turbidity higher than 1.0 NTU at the plant outlet and all samples for turbidity must be less than or equal to 0.3 NTU for at least 95 percent of the samples in any month. Systems that use filtration other than

4590-492: The SODIS method are located between latitude 15°N and 35°N, and also 15°S and 35°S. These regions have high levels of solar radiation, with limited cloud cover and rainfall, and with over 90% of sunlight reaching the earth's surface as direct radiation. The second most favorable region lies between latitudes 15°N and 15°S. these regions have high levels of scattered radiation, with about 2500 hours of sunshine annually, due to high humidity and frequent cloud cover. Local education in

4692-540: The SODIS method could be used as regions with highly turbid water could be treated for low costs. SODIS may alternatively be implemented using plastic bags. SODIS bags have been found to yield as much as 74% higher treatment efficiencies than SODIS bottles, which may be because the bags are able to reach elevated temperatures that cause accelerated treatment. SODIS bags with a water layer of approximately 1 cm to 6 cm reach higher temperatures more easily than SODIS bottles, and treat Vibrio cholerae more effectively. It

4794-524: The Standard Test Condition solar irradiance value of 1000 W/m for 2.74 hours a day. Usually solar panels are exposed to sunlight for longer than this in a given day, but the solar irradiance is less than 1000 W/m for most of the day. A solar panel can produce more when the Sun is high in Earth's sky and will produce less in cloudy conditions or when the Sun is low in the sky; usually

4896-476: The Sun is lower in the sky in the winter. Two location dependant factors that affect solar PV yield are the dispersion and intensity of solar radiation. These two variables can vary greatly between each country. The global regions that have high radiation levels throughout the year are the middle east, Northern Chile, Australia, China, and Southwestern USA. In a high-yield solar area like central Colorado, which receives annual insolation of 2000 kWh/m /year,

4998-479: The U.S. market are UL listed, meaning they have gone through testing to withstand hail. Potential-induced degradation (also called PID) is a potential-induced performance degradation in crystalline photovoltaic modules, caused by so-called stray currents. This effect may cause power loss of up to 30%. The largest challenge for photovoltaic technology is the purchase price per watt of electricity produced. Advancements in photovoltaic technologies have brought about

5100-877: The absorber layer of SWCNT PV is expected to be synthesized with CoMoCAT method. by Contrary to established thin films such as CIGS and CdTe, CZTS, Zn 3 P 2 , and SWCNT PVs are made from earth abundant, nontoxic materials and have the potential to produce more electricity annually than the current worldwide consumption. While CZTS and Zn 3 P 2 offer good promise for these reasons, the specific environmental implications of their commercial production are not yet known. Global warming potential of CZTS and Zn 3 P 2 were found 38 and 30 grams CO 2 -eq/kWh while their corresponding EPBT were found 1.85 and 0.78 years, respectively. Overall, CdTe and Zn 3 P 2 have similar environmental effects but can slightly outperform CIGS and CZTS. A study on environmental impacts of SWCNT PVs by Celik et al., including an existing 1% efficient device and

5202-409: The activation energy to decrease twenty-fold from 1.12 eV to 0.05 eV. Since the potential difference (E B ) is so low, the boron is able to thermally ionize at room temperatures. This allows for free energy carriers in the conduction and valence bands thereby allowing greater conversion of photons to electrons. The power output of a photovoltaic (PV) device decreases over time. This decrease

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5304-499: The amount of light reaching lower depths, which can inhibit growth of submerged aquatic plants and consequently affect species which are dependent on them, such as fish and shellfish . High turbidity levels can also affect the ability of fish gills to absorb dissolved oxygen. This phenomenon has been regularly observed throughout the Chesapeake Bay in the eastern United States. For many mangrove areas, high turbidity

5406-419: The amount of sunlight available and the efficiency of the electrical grid) and on the type of system, namely the system's components. A 2015 review of EPBT estimates of first and second-generation PV suggested that there was greater variation in embedded energy than in efficiency of the cells implying that it was mainly the embedded energy that needs to reduce to have a greater reduction in EPBT. In general,

5508-618: The bacterial regrowth of coliforms after SODIS. Research has shown that a number of low-cost additives are capable of accelerating SODIS and that additives might make SODIS more rapid and effective in both sunny and cloudy weather, developments that could help make the technology more effective and acceptable to users. A 2008 study showed that powdered seeds of five natural legumes (peas, beans and lentils)— Vigna unguiculata (cowpea), Phaseolus mungo (black lentil), Glycine max (soybean), Pisum sativum (green pea), and Arachis hypogaea (peanut)—when evaluated as natural flocculants for

5610-425: The bottles are washed before the first use. Water from possibly-contaminated sources is filled into the bottles, using the clearest water possible. Where the turbidity is higher than 30 NTU it is necessary to filter or precipitate out particulates prior to exposure to the sunlight. Filters are locally made from cloth stretched over inverted bottles with the bottoms cut off. In order to improve oxygen saturation,

5712-528: The bottom. An additional device, which may help measuring turbidity in shallow waters is the turbidity tube. The turbidity tube condenses water in a graded tube which allows determination of turbidity based on a contrast disk in its bottom, being analogous to the Secchi disk. Turbidity in air, which causes solar attenuation, is used as a measure of pollution. To model the attenuation of beam irradiance, several turbidity parameters have been introduced, including

5814-464: The bulk material with wire saws, and then go through surface etching before being cleaned. Next, the wafers are placed into a phosphorus vapor deposition furnace which lays a very thin layer of phosphorus, a group V element, which creates an n-type semiconducting surface. To reduce energy losses, an anti-reflective coating is added to the surface, along with electrical contacts. After finishing the cell, cells are connected via electrical circuit according to

5916-464: The cheapest source of electrical power in regions with a high solar potential, with a bid for pricing as low as 0.015 US$ / kWh in Qatar in 2023. In 2023, the International Energy Agency stated in its World Energy Outlook that '[f]or projects with low cost financing that tap high quality resources, solar PV is now the cheapest source of electricity in history. The term "photovoltaic" comes from

6018-689: The conventional or direct filtration must follow state limits, which must include turbidity at no time exceeding 5 NTU. Many drinking water utilities strive to achieve levels as low as 0.1 NTU. The European turbidity standard is 4 NTU. The US Environmental Protection Agency (EPA) has published water quality criteria for turbidity. These criteria are scientific assessments of the effects of turbidity, which are used by states to develop water quality standards for water bodies. (States may also publish their own criteria.) Some states have promulgated water quality standards for turbidity, including: Published analytical test methods for turbidity include: Turbidity

6120-534: The cost of each device by both reducing material and energy consumption during manufacturing. The global market share of CdTe was 4.7% in 2008. This technology's highest power conversion efficiency is 21%. The cell structure includes glass substrate (around 2 mm), transparent conductor layer, CdS buffer layer (50–150 nm), CdTe absorber and a metal contact layer. CdTe PV systems require less energy input in their production than other commercial PV systems per unit electricity production. The average CO 2 -eq/kWh

6222-452: The difference between the energy expended to harvest an energy source and the amount of energy gained from that harvest. The NEG and EROI also take the operating lifetime of a PV system into account and a working life of 25 to 30 years is typically assumed. From these metrics, the Energy payback Time can be derived by calculation. PV systems using crystalline silicon, by far the majority of

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6324-439: The electrical output of a PV system, the manufacturer must simply add more photovoltaic components. Because of this, economies of scale are important for manufacturers as costs decrease with increasing output. While there are many types of PV systems known to be effective, crystalline silicon PV accounted for around 90% of the worldwide production of PV in 2013. Manufacturing silicon PV systems has several steps. First, polysilicon

6426-409: The environmental impact of PV have focused on carbon dioxide equivalents per kWh or energy pay-back time (EPBT). The EPBT describes the timespan a PV system needs to operate in order to generate the same amount of energy that was used for its manufacture. Another study includes transport energy costs in the EPBT. The EPBT has also been defined completely differently as "the time needed to compensate for

6528-432: The first years of between 3% and 4%. However, other technologies, such as CIGS, show much lower degradation rates, even in those early years. Overall the manufacturing process of creating solar photovoltaics is simple in that it does not require the culmination of many complex or moving parts. Because of the solid-state nature of PV systems, they often have relatively long lifetimes, anywhere from 10 to 30 years. To increase

6630-691: The following countries had a high-quality grid infrastructure as in Europe, in 2020 it was calculated it would take 1.28 years in Ottawa , Canada, for a rooftop photovoltaic system to produce the same amount of energy as required to manufacture the silicon in the modules in it (excluding the silver, glass, mounts and other components), 0.97 years in Catania , Italy , and 0.4 years in Jaipur , India. Outside of Europe, where net grid efficiencies are lower, it would take longer. This ' energy payback time ' can be seen as

6732-446: The guides recommend that bottles be filled three-quarters, shaken for 20 seconds (with the cap on), then filled completely, recapped, and checked for clarity. The filled bottles are then exposed to the fullest sunlight possible. Bottles will heat faster and hotter if they are placed on a sloped sun-facing reflective metal surface. A corrugated metal roof (as compared to a thatched roof) or a slightly curved sheet of aluminum foil increases

6834-586: The higher the turbidity level, the higher the risk that people may develop gastrointestinal diseases . This is especially problematic for immunocompromised people, because contaminants like viruses or bacteria can become attached to the suspended solids. The suspended solids interfere with water disinfection with chlorine because the particles act as shields for viruses and bacteria. Similarly, suspended solids can protect bacteria from ultraviolet (UV) sterilization of water. In water bodies such as lakes , rivers and reservoirs , high turbidity levels can reduce

6936-641: The household level and is recommended by the World Health Organization as a viable method for household water treatment and safe storage. SODIS is already applied in numerous developing countries . Educational pamphlets on the method are available in many languages, each equivalent to the English-language version. Guides for the household use of SODIS describe the process. Colourless, transparent PET water or soda bottles of 2 litre or smaller size with few surface scratches are selected for use. Glass bottles are also suitable. Any labels are removed and

7038-444: The impact and potential impact of various types of PV, but these estimates are usually restricted to simply assessing energy costs of the manufacture and/or transport , because these are new technologies and the total environmental impact of their components and disposal methods are unknown, even for commercially available first generation solar cells , let alone experimental prototypes with no commercial viability. Thus, estimates of

7140-508: The important health benefits associated with these methods will likely increase adoption rates. Photovoltaics Photovoltaics ( PV ) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect , a phenomenon studied in physics , photochemistry , and electrochemistry . The photovoltaic effect is commercially used for electricity generation and as photosensors . A photovoltaic system employs solar modules , each comprising

7242-411: The junction temperature. The values of these parameters, which can be found in any data sheet of the photovoltaic module, are the following: Techniques for estimating these coefficients from experimental data can be found in the literature. The ability of solar modules to withstand damage by rain, hail , heavy snow load, and cycles of heat and cold varies by manufacturer, although most solar panels on

7344-473: The light inside the bottle. Overhanging structures or plants that shade the bottles must be avoided, as they reduce both illumination and heating. After sufficient time, the treated water can be consumed directly from the bottle or poured into clean drinking cups. The risk of re-contamination is minimized if the water is stored in the bottles. Refilling and storage in other containers increases the risk of contamination. The most favorable regions for application of

7446-437: The module changes as lighting, temperature and load conditions change, so there is never one specific voltage at which the module operates. Performance varies depending on geographic location, time of day, the day of the year, amount of solar irradiance , direction and tilt of modules, cloud cover, shading, soiling , state of charge, and temperature. Performance of a module or panel can be measured at different time intervals with

7548-419: The most important component of solar panels, which accounts for much of the energy use and greenhouse gas emissions, is the refining of the polysilicon. As to how much percentage of the EPBT this silicon depends on the type of system. A fully autarkic system requires additional components ('Balance of System', the power inverters , storage, etc.) which significantly increase the energy cost of manufacture, but in

7650-635: The newspaper test the user has to place the filled bottle upright on top of a newspaper headline and look down through the bottle opening. If the letters of the headline are readable, the water can be used for the SODIS method. If the letters are not readable then the turbidity of the water likely exceeds 30 NTU, and the water must be pretreated. In theory, the method could be used in disaster relief or refugee camps. However, supplying bottles may be more difficult than providing equivalent disinfecting tablets containing chlorine, bromine, or iodine. In addition, in some circumstances, it may be difficult to guarantee that

7752-458: The overall performance of the plant. There are several studies dealing with the power degradation analysis of modules based on different photovoltaic technologies available in the literature. According to a recent study, the degradation of crystalline silicon modules is very regular, oscillating between 0.8% and 1.0% per year. On the other hand, if we analyze the performance of thin-film photovoltaic modules, an initial period of strong degradation

7854-462: The performance of a complete string. Furthermore, not all modules in the same installation decrease their performance at exactly the same rate. Given a set of modules exposed to long-term outdoor conditions, the individual degradation of the main electrical parameters and the increase in their dispersion must be considered. As each module tends to degrade differently, the behavior of the modules will be increasingly different over time, negatively affecting

7956-570: The portion of time during the useful lifetime of the module in which the energy production is polluting. At best, this means that a 30-year old panel has produced clean energy for 97% of its lifetime, or that the silicon in the modules in a solar panel produce 97% less greenhouse gas emissions than a coal-fired plant for the same amount of energy (assuming and ignoring many things). Some studies have looked beyond EPBT and GWP to other environmental effects. In one such study, conventional energy mix in Greece

8058-443: The power output of a solar cell and the working temperature of its junction depends on the semiconductor material, and is due to the influence of T on the concentration, lifetime, and mobility of the intrinsic carriers, i.e., electrons and gaps. inside the photovoltaic cell. Temperature sensitivity is usually described by temperature coefficients, each of which expresses the derivative of the parameter to which it refers with respect to

8160-406: The process of "doping" the silicon substrate to lower the activation energy thereby making the panel more efficient in converting photons to retrievable electrons. Chemicals such as boron (p-type) are applied into the semiconductor crystal in order to create donor and acceptor energy levels substantially closer to the valence and conductor bands. In doing so, the addition of boron impurity allows

8262-483: The production process itself will not become more efficient in the future. Nonetheless, the energy payback time has shortened significantly over the last years, as crystalline silicon cells became ever more efficient in converting sunlight, while the thickness of the wafer material was constantly reduced and therefore required less silicon for its manufacture. Within the last ten years, the amount of silicon used for solar cells declined from 16 to 6 grams per watt-peak . In

8364-479: The p–n junction also influences the main electrical parameters: the short circuit current ISC, the open circuit voltage VOC and the maximum power Pmax. In general, it is known that VOC shows a significant inverse correlation with T, while for ISC this correlation is direct, but weaker, so that this increase does not compensate for the decrease in VOC. As a consequence, Pmax decreases when T increases. This correlation between

8466-544: The quantum efficiency value, as they affect "external quantum efficiency". Recombination losses are accounted for by the quantum efficiency, V OC ratio, and fill factor values. Resistive losses are predominantly accounted for by the fill factor value, but also contribute to the quantum efficiency and V OC ratio values. Module performance is generally rated under standard test conditions (STC): irradiance of 1,000 W/m , solar spectrum of AM 1.5 and module temperature at 25 °C. The actual voltage and current output of

8568-415: The removal of turbidity, were as effective as commercial alum and even superior for clarification in that the optimum dosage was low (1 g/L), flocculation was rapid (7–25 minutes, depending on the seed used) and the water hardness and pH was essentially unaltered. Later studies have used chestnuts , oak acorns, and Moringa oleifera (drumstick tree) for the same purpose. Other research has examined

8670-539: The same period, the thickness of a c-Si wafer was reduced from 300 μm, or microns , to about 160–190 μm. The sawing techniques that slice crystalline silicon ingots into wafers have also improved by reducing the kerf loss and making it easier to recycle the silicon sawdust. Crystalline silicon modules are the most extensively studied PV type in terms of LCA since they are the most commonly used. Mono-crystalline silicon photovoltaic systems (mono-si) have an average efficiency of 14.0%. The cells tend to follow

8772-566: The sensor and custom software running on the phone analyses the sensor colour to provide a quantitative measurement of UV dose. In isolated regions the effect of wood smoke increases lung disease, due to the constant need for building fires to boil water and cook. Research groups have found that boiling of water is neglected due to the difficulty of gathering wood, which is scarce in many areas. When presented with basic household water treatment options, residents in isolated regions in Africa have shown

8874-416: The source beam than if there are few. The units of turbidity from a calibrated nephelometer can be either NTU or FTU, depending on the standard method used. To some extent, how much light reflects for a given amount of particulates is dependent upon properties of the particles like their shape, color, and reflectivity. For this reason (and the reason that heavier particles settle quickly and do not contribute to

8976-460: The specific application and prepared for shipping and installation. Solar photovoltaic power is not entirely "clean energy": production produces greenhouse gas emissions, materials used to build the cells are potentially unsustainable and will run out eventually, the technology uses toxic substances which cause pollution, and there are no viable technologies for recycling solar waste. Data required to investigate their impact are sometimes affected by

9078-450: The sun shines. Water heated to temperatures below 100 °C is generally referred to as pasteurized water. The ultraviolet part of sunlight can also kill pathogens in water. The SODIS method uses a combination of UV light and increased temperature (solar thermal) for disinfecting water using only sunlight and repurposed PET plastic bottles. SODIS is a free and effective method for decentralized water treatment , usually applied at

9180-470: The systems in practical use, have such a high EPBT because silicon is produced by the reduction of high-grade quartz sand in electric furnaces . This coke-fired smelting process occurs at high temperatures of more than 1000 °C and is very energy intensive, using about 11 kilowatt-hours (kWh) per produced kilogram of silicon. The energy requirements of this process makes the energy cost per unit of silicon produced relatively inelastic, which means that

9282-407: The time of testing, the test modules are binned according to their test results, and a typical manufacturer might rate their modules in 5 W increments, and either rate them at +/- 3%, +/-5%, +3/-0% or +5/-0%. The performance of a photovoltaic (PV) module depends on the environmental conditions, mainly on the global incident irradiance G in the plane of the module. However, the temperature T of

9384-411: The total renewable- and non-renewable primary energy required during the life cycle of a PV system" in another study, which also included installation costs. This energy amortization, given in years, is also referred to as break-even energy payback time . The lower the EPBT, the lower the environmental cost of solar power . The EPBT depends vastly on the location where the PV system is installed (e.g.

9486-414: The treatment of turbidity is common when the affected water bodies are dispersed (i.e. there are numerous water bodies spread out over a geographical area, such as small drinking water reservoirs), when the problem is not consistent (i.e. when there is turbidity in a water body only during and after the wet season) or when a low cost solution is required. In-situ treatment of turbidity involves the addition of

9588-440: The use of SODIS is important to avoid confusion between PET and other bottle materials. Applying SODIS without proper assessment (or with false assessment) of existing hygienic practices & diarrhea incidence may not address other routes of infection. Community trainers must themselves be trained first. SODIS is an effective method for treating water where fuel or cookers are unavailable or prohibitively expensive. Even where fuel

9690-619: The use of doped semiconductors to increase the production of oxygen radicals under solar UV-A. Recently, researchers at the National Centre for Sensor Research and the Biomedical Diagnostics Institute at Dublin City University have developed an inexpensive printable UV dosimeter for SODIS applications that can be read using a mobile phone. The camera of the phone is used to acquire an image of

9792-413: The user's preference. When the water is highly turbid, SODIS cannot be used alone; additional filtering or flocculation is then necessary to clarify the water prior to SODIS treatment. Recent work has shown that common table salt (NaCl) is an effective flocculation agent for decreasing turbidity for the SODIS method in some types of soil. This method could be used to increase the geographic areas for which

9894-457: The water (inversely related to turbidity). The Secchi disk has the advantages of integrating turbidity over depth (where variable turbidity layers are present), being quick and easy to use, and inexpensive. It can provide a rough indication of the depth of the euphotic zone with a 3-fold division of the Secchi depth , however this cannot be used in shallow waters where the disk can still be seen on

9996-446: The water a plastic smell, they are more difficult to handle when filled with water, and they typically require that the water be transferred to a second container for drinking. Another important benefit in using the SODIS bottles as opposed to the bags or other methods requiring the water to be transferred to a smaller container for consumption is that the bottles are a point-of-use household water treatment method. Point-of-use means that

10098-472: The water is treated in the same easy to handle container it will be served from, thus decreasing the risk of secondary water contamination. If the water bottles are not left in the sun for the proper length of time, the water may not be safe to drink and could cause illness. If the sunlight is less strong, due to overcast weather or a less sunny climate, a longer exposure time in the sun is necessary. The following issues should also be considered: According to

10200-416: The water will be left in the sun for the necessary time. Other methods for household water treatment and safe storage exist, including chlorination, flocculation/disinfection, and various filtration procedures. The method should be chosen based on the criteria of effectiveness, the co-occurrence of other types of pollution (e.g. turbidity, chemical pollutants), treatment costs, labor input and convenience, and

10302-467: Was compared to multi-si PV and found a 95% overall reduction in effects including carcinogens, eco-toxicity, acidification, eutrophication, and eleven others. Cadmium telluride (CdTe) is one of the fastest-growing thin film based solar cells which are collectively known as second-generation devices. This new thin-film device also shares similar performance restrictions ( Shockley-Queisser efficiency limit ) as conventional Si devices but promises to lower

10404-567: Was to power orbiting satellites and other spacecraft , but today the majority of photovoltaic modules are used for grid-connected systems for power generation. In this case an inverter is required to convert the DC to AC . There is also a smaller market for stand alone systems for remote dwellings, boats , recreational vehicles , electric cars , roadside emergency telephones, remote sensing , and cathodic protection of pipelines . Photovoltaic power generation employs solar modules composed of

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