Koewarasan, fotografie: Hans van der Hek





Zonne-energie


by Frida Berntsson and Jasmina Huslanovic



Index



Introduction

The Sun

How the photovoltaic cell works

How to make a photovoltaic cell
Different types of PV-cells
Crystalline silicium cells
Amorphous silicium cells
CIS-cells
Grštzel-cells
Tandem-cells
Galliumarsenid cells
Cadmium sulphide/copper sulphide cells
Photogalvanic cells
Photo electrolytic cells
How to use the solar cells

The car that never runs out of gas

The Solar car competition

Environmental influence

The cost

Advantages

Disadvantages

Conclusion

List of references

 

Introduction

We have chosen to write about solar energy, since we believe it is the energy source that is going to rule the market of producing electricity on in the future. In fact, it is the oldest and most efficient form of renewable energy. Ancient Native American tribes built their homes so that they could utilize the suns light and warmth, so to use the solar energy is not a new idea.

The coal, the oil, the natural gas and the uranium is eventually going to be used up, unlike the sun. Solar energy does not contribute to acidification and the greenhouse effect and it does not destroy the ozone layer.

For every kilo watt-hour of solar energy that we manage to transform into warmth or electrical energy, we save a little piece of the environment.

In 1839, the French physicist Edmund Baqurel was experimenting with an electrolytic cell made of two metal plates placed in a conductive solution. When the cell was exposed to light he found that the generated current could be increased - the photoelectric effect was discovered.

Thirty-four years later the British scientist Willoughby Smith discovered that selenium was sensitive to light. He found that selenium's ability to conduct electricity increased if it was exposed to more light. This discovery inspired scientists to carry out further experiments with this rare element.

Charles Fritts developed the first selenium-based solar cell in 1880.




The real breakthrough came in the 1950:s when Bell Laboratories discovered that silicon - the second most abundant element on earth - was also sensitive to light and generated a substantial voltage when treated with certain impurities. By 1954, Bell had developed a solar cell using silicon as the base material that achieved an efficiency of 6%. The first industrial use occurred soon afterwards: the powering of a remote telephone repeater station in rural Georgia.

In the late 1950:s, NASA installed a photovoltaic array on America's first satellite, "Vanguard One". The costs for such systems are understandably quite high, reaching over 800 SEK/watt. For earth-bound applications, where environmental and size constraints are not nearly so severe, much cheaper devices have been developed. Today, the satellites are driven with solar energy.




The potential for solar electricity is huge. The solar radiation that hits 2% of the worlds deserts would be sufficient to replace all the fossil fuels on earth, if the solar cells are to produce electricity that divides water into hydrogen and oxygen (electrolysis of water) and the hydrogen gas is then used as fuel. This seems to be a very good proposal, but what would happen to the environment? What would the effect be - no one knows.

Research is done within a new technology with thin film solar cells, where high grades of efficiency have been reached.

The solar power can also be used for warming up dwellings and other buildings, but we have concentrated this report on using it for electricity.

We have found most of the material on the Internet, since we had access to it, and it is a perfect information source. Besides, the information on the Internet was gathered from books, so it would have been the same thing as going to the library. Actually, we went to the library, but the books we found were written a long time ago, so they were not really current. To collect what we needed from the web seemed to be a good alternative!

The sun

The surface of the sun has a temperature of approximately 6000K and sends out electromagnetic radiation, photons.

The energy that reaches the surface of the earth is included in the wavelength area 300-2500 nm. The ozone layer on the height of 20-40 km absorbs the radiation with wavelength below 300 nm. The radiation with wavelength higher than 2500 nm is absorbed by carbon oxide and water vapour in the atmosphere.

The content of exergy in solar energy is approximately 93% of the content of energy, although it is not ideal seen from an energy point of wiev since it takes large surfaces to collect the energy.

Because of the refraction and spreading of the sunlight in the atmosphere all the solar radiation that reaches the surface of the earth is not parallel, some of it turns into diffuse light. The amount of diffuse light increases with the amount of water vapour, free drips of water and other particles in the air. In Sweden, the part of diffuse light reaches approximately 50% of the total incoming radiation. In the summer, the amount of the diffuse light is 20%, in the winter it is 80%.

How the photovoltaic cell works:

Solar cells are used to produce electricity directly out of the sunshine. The most common type of solar cells are made of silicium, or silicon as it also is called. When the solar cell is exposed to light, the front becomes negatively and the backside positively charged, the electrons start to wander and electricity is created. The best solar cells transform 20% of the sunshine to electricity.

Within an individual silicon cell there are two layers of impure silicon. One side is doped with an element that tends to lose a valence shell electron and the other with one that needs one more electron to fill its valence shell, manufacturers often use boron and phosphorous. This sets up a situation where one side tends to be positive and the other negative. Where they meet is called the P/N-junction. One has a tendency to give up an electron and the other one to attract an electron. Light energy in the form of photons creates a movement of electrons across the P/N-junction. Each one of these cells is connected with other cells in series and in parallel to form a module. Modules are then grouped into arrays, which creates a large source of power.

There are contacts on both sides of the cell that can be connected to a battery, a transformer or any other unit that accumulates or forwards the extracted energy. The contact on the side, which faces the sun, is constructed so the sunlight can reach the semiconductor plate, while the backside of the cell often contains wall-to-wall contact plate. Because of the contacts and the covering glass, the otherwise thin PV-cells gets a manageable thickness.

How to make a photovoltaic cell:




The top layer in a PV-cell must fulfil two important demands; it must let through as much sunlight as possible and also protect the PV-cell from being exposed to the clerk of the weather. As much of the solar energy as possible must pass through the top layer to the PV-cell itself. Each protective layer, which absorbs solar energy, reduces the effect of the PV-cell. The top layer must therefore be made of glass containing low percentage of iron.

Etanvinylacetat, EVA, is a plastic material with good conductivity and relatively high melting point. EVA is the material, which is used to attach the protective glass to the PV-cell and also to attach the PV-cell to the material on the backside of the cell. A plastic material or a metal plate, for example aluminium, is used as a bottom plate. Metallic contacts are fastened on the PV-cell's upper and bottom side. The upper contact on the PV-cell is therefore attached to the lower contact on the next cell. This PV-cell module is placed between two layers of EVA plastic. Thereafter is the glass plate placed on top and the bottom plate below the module. This sandwich of several materials is placed in a hot vacuum chamber where all air bubbles are removed; the plastic melts and seals the spaces between the glass, the PV-cell and the bottom plate. If the air bubbles are not removed before the solar cell is sealed, they will surely expand in the warmth of the sun and thereby destroy the entire function of the photovoltaic cell.

Different types of PV-cells:

There are lots of different kinds of PV-cells. Below we have listed a few of them, new ones are constantly coming as a result of research. The efficiency and the price varies from model to model.

Crystalline silicium cells

Silicium cells are the solar cells that are the most common type today and in the future will be the most current because of the large amount of silicium. 27% of the surface of the Earth is made of silicium and the reachability is good.

The very first commercial solar cells were used in space in 1958. The high manufacturing costs of those times were faced to even larger investments for use of nuclear power or fuel cells for the satellites. The solar cells were built up of two thin layers of silicium in crystalline form. During the 70's the same technique was introduced for production of electricity on ground level.




What is positive with the crystalline silicium cells is a relatively high degree of efficiency - the industrial manufactured cells have reached an efficiency of 20%. The negative side is the high cost for the semiconductor material even though it is very thin, only a tenth of a millimetre. The silicium material must also be extremely clean so it does not lower the grade of efficiency.

Today's modern crystalline silicium cells have with the available method of production and system solutions an energy cost of between 3 and 10 SEK/kWh why the competitive strength against electricity connected to the main system is minimal. The area of use has mainly been applications were other electricity is not available, for example: the archipelago, road signs, radio and telestations in the mountains and so on. Crystalline silicium cells have for long time been the only solar cells technique, and therefore a greater part of the worlds today 500 MW solar cells is made of crystalline silicium.

Amorphous silicium cells

The science direction towards cheaper solar cell electricity lead to a development of solar cells with lower consumption of material then the crystalline silicium cells. The first thin film cells, which were brought out in the 1980:s and were made of amorphous, totally unarranged in the opposite of the crystalline, silicium. The silicium atoms lie totally unstructured with a lower grade of efficiency as follows (approximately 9% is until now the maximum value). This fact is compensated by a considerable simpler, less raw material needed and therefore lower manufacturing cost.

In the end of the 80's it was considered that the amorphous silicium cells would be the technique of the future. The amorphous silicium cells did not endure sunlight, after just a few months of use, the grade of efficiency was lowered by 30%. Despite this, the cells are used in pocket calculators, but that is all.

CIS cells

A thin film cell that has a brighter future than the amorphous silicium cell is the

CIS cell, one of the newer products. It consists of a diode with an n-doped cadmium sulphide (CdS) and zinc oxide (ZnO) as the negative pole on top of the light absorbing CIS bed. Copper, indium and selenium (CuInSe2) makes the 2-3 micrometer thick film, that gave name to the cell. The diodes plus pole is created with a conductive layer of molybdenum behind the CIS layer.

The solar cell, which produces direct current, is made with window glass as the initial point, on top of that, a cover of molybdenum is placed.

As the amorphous silicium cells, the CIS cells do not demand very much manufacturing material for the energy transforming parts. This is a contributing cause in the interest of the cell seen from an economical perspective.

With mass production of the CIS cells, the price would be about 400 SEK per square meter according to calculations from the American energy department. The maximum grade of efficiency of a solar cell with the CIS technology in modules ready to be used is at 11%. That is much lower than the crystalline silicium cells.

The length of life for a CIS cell has not yet been able to determine, since its development has occurred mainly during the 90's. Some negative environmental influences have already been observed in the cadmium and the indium which are components in the CIS cell-a mass production would impoverish the assets of breakable indium. Besides, it is a known fact that the heavy metal cadmium has a negative influence on the nature.

Grštzel cells

The G-cell is yet another step closer to the nature. The Swiss chemist, Michael Grštzel, has began from the photosynthesis in the solar cell, its development began in 1990. In the G-cell there is an artificial, red colorant which absorbs the photoenergy. The colorant is seated on tiny particles of semiconductive titanium dioxide.

The voltage in the G-cell does not drop at a lower light intensity, in contrast to solar cells of diode type (CIS cells and silicium cells). Therefore it can soon be used in for example wristwatches.

As the G-cell still is in an early stage of development, the effects of long-term use have not been practically tested. Swiss scientists have recently showed that the colorant lasts for at least 15 years of exposure to sunlight. The electrolyte is another problem, when it must be resistant to both low and high temperatures when used outdoors. It also has to be non-polluting with regard to the solvent. The advantages with this kind of a technology are besides the flexibility also the relatively simple manufacturing process and the constantly increasing degree of efficiency (10% at maximum rate of sunlight), which still is considerable lower than the CIS cells'. The completed solar cells shall according to the Swiss scientists cost around 600 SEK per square meter.

Tandem cells

The efficiency of the solar cell is strongly reduced depending on that many wavelengths of light pass by the absorbing semiconductive material. One of the solutions to this problem is placing several solar cells on top of each other; the long wave radiation that can not be absorbed by one solar cell, can instead be utilized by a solar cell that is placed behind the first one.

This construction does not allow more than three cells together since further optical losses arise, mostly caused by reflection in the different surfaces, when several solar cells are put together into a tandem cell. The material cost increases naturally with the amount of layers used. The theoretical degree of efficiency is 40-45% and more than 30% has already been accomplished at practical experiments.

Galliumarsenid cells (GaAs)

Galliumarsenid cells can bear a high concentration, up to 2000 times of the direct sunlight. An efficiency of 23 percent has been reached, but these cells are much more expensive than silicium cells.

Cadmium sulphide/copper sulphide (CdS/CuS)

Cells made of cadmium sulphide/copper sulphide have much lower degrees of efficiency and much shorter length of life. They are though cheaper than silicium cells.

Photo galvanic cells

If one or both electrodes in an electrolytic solution is illuminated, an electric voltage will arise between the electrodes, and electric energy can be extracted. The electrolyte contains a colorant, which can absorb a certain part of the sunlight's spectrum, and some metal that can take up and emit electrical charge.

So far, only a fraction of the light can be used. The method is still on its basic research phase.

Photo electrolytic cells

If one of the electrodes in an electrolytic cell is made of a semiconductor, oxygen can be released near the semiconductor electrode when it is exposed to the sun. Electrons stream over to the other electrode where hydrogen gas is released. If the semiconductor material is made of titanium dioxide, a rate of 10% of the solar energy can be used. The method is still on its basic research phase.

How to use the solar cells

Once there are arrays of panels in the sun, we regulate the power and store it in large powerful batteries to be used later. Then we pass the direct current of electricity through a device called an inverter. The inverter changes the electricity to alternating current. Now there is regular electricity!

The car that never runs out of gas

Electric motor cars driven with solar energy are still a bad alternative to regular cars. All around the world car factories are competing about manufacturing the fastest car that only uses the beams from the sun to move forward. The solar car, as we can call the cars that are driven directly with solar energy, could be one of the future methods to decrease the pollution, especially in the cities. But perhaps it will be more realistic with cars driven with electricity from charging stations. It would be an option to have solar cells on the roof of the garage that collect and store the energy during the day and charge the car during the night. In the cities, solar cells can be placed on the tower blocks and sockets down on the street where the cars can be recharged.

The big problem is that electricity from solar cells is more expensive in proportion to other more common energy sources. The price on solar cells has began to sink, but economically seen it is only lucrative in special cases. For example there are solar cells on the roof of many Norwegian cabins in areas where it is very expansive to install electricity. But the more talk about solar cells, the more ideas will be tested and the inquiry will lower the prices of the solar cells.

The Solar car competition

Every third year there is a competition held between cars that are driven with help from solar cells as the only charging unit. The competition is held in Australia for obvious reasons, because the solar cells demand lots of sun to work as good as possible. The competitors are mostly not the best drivers and the vehicles that win are not necessarily the fastest ones. You have to be tactical and build a car that lasts, since what is most important for many of the competitors is to reach goal. Considering the source of energy, the sun, you have to say that "The World Solar Car Challenge" is the purest car race in the world.

The competition

The competition attracts competitors from all around the world, since it is not just a competition but also a technical adventure; a pretty undangerous way to stretch the limits and a way to open doors to the future. The fossil fuels that cars today are driven with, is calculated to end in a near future, so perhaps solar driven cars are the answer in a future without fossil fuels. In that way, the people that compete can be seen as pioneers. Solar cell cars are today just a dream, because we do not have sufficiently effective or cheap solar cells and accumulators.




The competition is about travelling the distance of 3 000 km on the shortest possible time. The race leaps between Darwin and Adelaide, which is one of the world's most arid areas. The organiser and founder of the competition, Hans Tholstrup, drove the distance with his " Quite Achiever" as early as 1982. The first competition was held in 1987 and the winner was General Motors with "The Sunraycer". They covered the distance in approximately 45 hours, similar to an average speed of 67 km/h.

Environmental influence

Solar cells belong in the highest grade to the renewable methods of producing electricity on - it will take billions of years before the sun has reached its end as an energy source. There are despite all the positive prognoses from scientists even some negative environmental effects, as an extensive use of solar cells would give rise to. The produce of entire solar cell systems demands a lot of energy and implies that no rare raw materials disappear because of the solar cell production. The manufacturing in this consideration does not part from remaining industry. Despite this, the solar modules' long service life and short energy payback time means that photovoltaic systems have a positive energy balance.

A recycling plant can process glass, silicon and aluminium, the main components of the solar modules.

The cost

Solar energy costs somewhere around 8 SEK/kWh, while nuclear power only costs 0,13-0,18 SEK/kWh. In the future, with mass production, solar cells can become so cheap that they will be economically lucrative. To provide a PV power supply capable of meeting the demand from a typical domestic energy efficient house costs in the region of 200 000 SEK. Although this may seem quite high, it is not an unreasonable proportion of the cost of building a house.

Advantages
  • The pollution gets lesser
  • The dependence on imported fuel is lowered since the solar energy is an domestic kind of energy
  • The employment increases with domestic production
  • A well developed solar energy market can create export income
  • Solar panels have a long life time, minimum 25 years
  • Solar energy systems need very little maintenance

Disadvantages
  • The technique is to expensive to manufacture and install
  • Up in the Nordic countries there are to few sunny days to satisfy our entire need of energy, there will be problems during the nights and the winter
  • Solar cell panels require large surfaces
  • Storing electricity is very difficult. It has to be converted into other forms, that means losses

Conclusions

Although economically it is not yet a fully matured technology, photovoltaic technology is now on the threshold of a performance-to-cost capability that would permit it to make significant advances in many new market areas. With costs falling each year photovoltaic is already commercially mature in many remote applications, where it can compete with the higher installation costs of long links to the grid or expansive generation from diesel sets. Such applications already include health care in the developing world, telecommunications repeaters, cathodic protection of pipelines, and marine buoys.

Using solar energy, as a source of power is in the long run one of the few energy sources that can supply us with energy on today's level!

List of references


http://jaknet.jakgym.se/komvux/sindex.html
http://www.xpress.se/~gbgm0073/index.html
http://www.hj.se/~josv/energi.htm
http://hem1.passagen.se/aaked/solcell.htm 
http://www.thn.edu.stockholm.se/projekt/energi/solenergi/index.html
http://www.solardirect.com/pv/pv.htm
http://www.flasolar.com/photovol_main.htm 
door Frida Berntsson en Jasmina Huslanovic

Index

Inleiding
De zon
Hoe de foto-elektrische cel werkt
Hoe wordt een foto-elektrische cel gemaakt
Verschillende types van PV Cellen
Kristallijnen silicium cellen
Amorfe silicium cellen
CIS -cellen
Grštzel cellen
Tandemcellen
Galliumarsenid cellen
Cadmium sulfide / kopersulfide cellen
Fotogalvanische cellen
Foto-elektrolytische cellen
Hoe de zonnecellen te gebruiken

De auto die nooit uit gas loopt
De zonneautoconcurrentie
Milieu invloed
De kosten
Voordelen
Nadelen
Conclusie
Lijst van verwijzingen
Begrippen


Inleiding

Wij hebben besloten om over zonne-energie te schrijven, omdat zonne-energie de meest logische energiebron is voor het genereren van elektriciteit. Zowel in het heden als in in de toekomst. En uiteindelijk de enige oplossing blijkt te zijn voor onze toenemende vraag naar energie zonder roofbouw te plegen op ons leefmilieu. Zonne-energie is de oudste en meest efficiŽnte vorm van vernieuwbare energie. Het gebruik van zonne-energie is dus geen nieuw idee. De oude Inheemse Amerikaanse stammen bouwden hun huizen zodat zij het de zonlicht en de warmte gunstig konden gebruiken.

Maar voor niets gaat de zon op en daar kun je dus niets mee, want daar valt niets aan te verdienen. Dit is wel onze grootste economische denkfout. De steenkool, de olie, het aardgas en het uranium zijn goed te verhandelen maar raken uiteindelijk op. De zon daarentegen raakt niet uitgeput. De zonne-energie draagt niet bij tot verzuring en het greenhouse effect. En het vernietigt niet de ozonlaag.

Voor elk kilowattuur zonne-energie die wij omzetten in warmte of electro-energie, sparen wij een klein stuk van het milieu.

In 1839, experimenteerde de Franse fysicus Edmund Baqurel met een elektrolytische cel die van twee metaalplaten wordt gemaakt die in een geleidende oplossing worden geplaatst. Toen de cel aan licht werd blootgesteld vond hij dat de geproduceerde stroom zou kunnen worden verhoogd - het foto-elektrische effect werd ontdekt.

Vierendertig jaar later ontdekte de Britse wetenschapper Willoughby Smith dat het selenium voor licht gevoelig was. Hij vond dat de capaciteit van het selenium om elektriciteit te leiden steeg als het aan meer licht werd blootgesteld. Deze ontdekking inspireerde wetenschappers om verdere experimenten met dit zeldzame element uit te voeren.

Charles Fritts ontwikkelde de eerste op selenium gebaseerde zonnecel in 1880.



De echte doorbraak kwam in 1950:s toen de Laboratoria van de Klok ontdekten dat silicium - tweede - overvloedigste element ter wereld - was ook gevoelig voor licht en produceerde een wezenlijk voltage wanneer behandeld met bepaalde onzuiverheden. Tegen 1954, had de Klok een zonnecel gebruikend silicium als het basismateriaal ontwikkeld dat een efficiency van 6% bereikte. Het eerste industriŽle gebruik kwam spoedig daarna voor: het aandrijven van een verre post van de telefoonrepeater in landelijk GeorgiŽ.

In eind 1950:s, NASA installeerde een photovoltaic serie op de eerste satelliet van Amerika, ?Voorhoede …ťn?. De kosten voor dergelijke systemen zijn begrijpelijk vrij hoog , bereikend meer dan 800 SEK/watt. Voor verbindende toepassingen, waar de milieu en groottebeperkingen niet bijna streng zo zijn, zijn de veel goedkopere apparaten ontwikkeld. Vandaag, worden de satellieten gedreven met zonne-energie.



Het potentieel voor zonneelektriciteit is reusachtig. De zonnestraling die 2% van de wereldenwoestijnen raakt zou volstaan om alle fossiele brandstoffen ter wereld te vervangen, als de zonnecellen elektriciteit moeten veroorzaken die water in waterstof en zuurstof (elektrolyse van water) verdeelt en het waterstofgas wordt dan gebruikt als brandstof. Dit schijnt een zeer goed voorstel te zijn, maar wat aan het milieu zou gebeuren? Wat het effect - niemand zou zijn weet het. Het onderzoek wordt gedaan binnen een nieuwe technologie met dunne film zonnecellen, waar de hoge rangen van efficiency zijn bereikt. De zonnemacht kan ook voor het opwarmen van woningen en andere gebouwen worden gebruikt, maar wij hebben dit rapport bij het gebruiken van het voor elektriciteit geconcentreerd. Wij hebben het grootste deel van het materiaal op Internet gevonden, aangezien wij toegang tot het hadden, en het is een perfecte informatiebron. Bovendien, de informatie over Internet werd verzameld van boeken, zodat zou het het zelfde ding zoals gaand naar de bibliotheek geweest zijn. Eigenlijk, gingen wij naar de bibliotheek, maar de boeken die wij lang geleden geschreven=werden= hebben gevonden, zodat zij waren niet werkelijk huidig. Verzamelen wat wij van het Web nodig hadden scheen een goed alternatief te zijn!

De zon

De oppervlakte van de zon heeft een temperatuur van ongeveer 6000K en stuurt elektromagnetische straling, fotonen. De energie die de oppervlakte van de aarde bereikt is inbegrepen in het golflengtegebied 300-2500 NM. De ozonlaag op de hoogte van 20-40 km absorbeert de straling met golflengte onder 300 NM. De straling met golflengte hoger wordt dan 2500 NM geabsorbeerd door koolstofoxyde en waterdamp in de atmosfeer. De inhoud van exergy in zonne-energie is ongeveer 93% van de inhoud van energie, hoewel het niet ideaal gezien van een energiepunt van wiev is aangezien het grote oppervlakten neemt om de energie te verzamelen. De hoeveelheid diffuus licht stijgt met de hoeveelheid waterdamp, vrije druppels van water en andere deeltjes in de lucht. In Zweden, bereikt het deel van diffuus licht ongeveer 50% van de totale inkomende straling. In de zomer, is het bedrag van het diffuse licht 20%, in de winter is het 80%.

Hoe de photovoltaic cel werkt:

De zonne cellen worden gebruikt om elektriciteit uit de zonneschijn direct te veroorzaken. Het gemeenschappelijkste type van zonnecellen wordt gemaakt van silicium, of silicium aangezien het ook wordt geroepen. Wanneer de zonnecel aan licht wordt blootgesteld, wordt de voorzijde negatief en het positief geladen achtereind, beginnen de elektronen te wandelen en de elektriciteit wordt gecre?Žrd. De beste zonnecellen zetten 20% van de zonneschijn aan elektriciteit om. Binnen een individuele siliciumcel zijn er twee lagen van onzuiver silicium. …ťn kant wordt gesmeerd met een element dat neigt om een valentieshell elektron en andere met te verliezen die ťťn meer elektron vergt om zijn valentieshell, het borium van het fabrikantengebruik vaak te vullen en fosforachtig. Dit zet een situatie op waar ťťn kant positief neigt te zijn en negatieve andere. Waar zij worden genoemd de p/N-Verbinding samenkomen. Men heeft een tendens om een elektron en andere op te geven om een elektron aan te trekken. De lichte energie in de vorm van fotonen leidt tot een beweging van elektronen over de p/N-Verbinding. Elke ťťn van deze cellen wordt verbonden aan andere cellen in reeks en in parallel om een module te vormen. De modules worden dan gegroepeerd in series, wat tot een grote bron van macht leidt. Er zijn contacten aan beide kanten van de cel die met een batterij, een transformator of een andere eenheid kan worden verbonden die accumuleert of de gehaalde energie door:sturen. Het contact aan de kant, die de zon onder ogen ziet, wordt geconstrueerd zodat kan het zonlicht de halfgeleiderplaat bereiken, terwijl het achtereind van de cel vaak wall-to-wall contactplaat bevat. Wegens de contacten en het behandelende glas, krijgt de anders dunne pV-Cellen een handelbare dikte.

Hoe te om een photovoltaic cel te maken:



De hoogste laag in een pV-Cel moet twee belangrijke eisen vervullen; het moet door zoveel mogelijk zonlicht laten en ook de pV-Cel beschermen tegen wordt blootgesteld aan de bediende van het weer. Zo veel van de zonne-energie zoals mogelijk moet door de hoogste laag aan de pV-Cel zelf overgaan. Elke beschermende laag, die zonne-energie absorbeert, vermindert het effect van de pV-Cel. De hoogste laag moet daarom van glas worden gemaakt dat laag percentage van ijzer bevat. Etanvinylacetat, EVA, is een plastic materiaal met goed geleidingsvermogen en vrij hoog smeltpunt. EVA is het materiaal, dat wordt gebruikt om het beschermende glas vast te maken aan de pV-Cel en ook de pV-Cel te verbinden aan het materiaal op het achtereind van de cel. Een plastic materiaal of een metaalplaat, bijvoorbeeld aluminium, worden gebruikt als grondplaat. De metaal contacten worden vastgemaakt aan de de pV-Cel bovenleer en bodemkant. Het hogere contact op de pV-Cel is daarom in bijlage aan het lagere contact op de volgende cel. Deze wordt de pV-Cel module geplaatst tussen twee lagen van het plastiek van EVA. Daarna is de glasplaat die op bovenkant en de grondplaat onder de module wordt geplaatst. Deze sandwich van verscheidene materialen wordt geplaatst in een hete luchtledige kamer waar alle luchtbellen worden verwijderd; het plastiek smelt en verzegelt de ruimten tussen het glas, de pV-Cel en de grondplaat. Als de luchtbellen niet worden verwijderd alvorens de zonnecel wordt verzegeld, zullen zij zich zeker in de warmte van de zon uitbreiden en zullen daardoor de volledige functie van de photovoltaic cel vernietigen.

Verschillende types van pV-Cellen:

Er zijn veel verschillende soorten pV-Cellen. Hieronder hebben wij van enkelen van hen een lijst gemaakt, komen nieuwe degenen constant als resultaat van onderzoek. De efficiency en de prijs variŽren van model aan model.

Kristallijne siliciumcellen

De cellen van Silicium zijn de zonnecellen die vandaag het gemeenschappelijkste type zijn en in de toekomst het huidigst wegens de grote hoeveelheid silicium zal zijn. 27% van de oppervlakte van de Aarde wordt gemaakt van silicium en reachability is goed.
De allereerste commerciŽle zonnecellen werden gebruikt in ruimte in 1958. De allereerste commerciŽle zonnecellen werden gebruikt in ruimte in 1958. De hoge productiekosten van die tijden werden onder ogen gezien aan nog grotere investeringen voor gebruik van kernmacht of brandstofcellen voor de satellieten.

De zonnecellen werden opgebouwd van twee dunne lagen van silicium in kristallijne vorm. Tijdens de jaren '70 werd de zelfde techniek geÔntroduceerde voor productie van elektriciteit op grondniveau.

Wat met de kristallijne siliciumcellen positief is is een vrij hoge graad van efficiency - de industriŽle vervaardigde cellen hebben een efficiency van 20% bereikt. De negatieve kant is de hoge kosten voor het halfgeleider materiaal alhoewel het, slechts een tiende van een millimeter zeer dun is. Het silicium materiaal moet ook uiterst schoon zijn zodat vermindert het niet de rang van efficiency.

De moderne kristallijne siliciumcellen van vandaag hebben met de beschikbare methode van productie en systeemoplossingen energiekosten van tussen 3 en 10 SEK/kWh waarom het concurrentievermogen tegen elektriciteit die met het belangrijkste systeem wordt verbonden minimaal is. Het gebied van gebruik is hoofdzakelijk toepassingen was andere elektriciteit is niet beschikbaar, bijvoorbeeld geweest: de archipel, de wegtekens, de radio en telestations in de bergen etc. De kristallijne siliciumcellen zijn voor oud de enige zonnecellentechniek geweest, en daarom wordt een groter deel van de werelden de zonne cellen van vandaag 500 mw gemaakt van kristallijne silicium.

Amorfe siliciumcellen

De wetenschapsrichting naar goedkopere zonnecelelektriciteit leidt tot een ontwikkeling van zonnecellen met lagere consumptie van materiaal toen de kristallijne siliciumcellen. De eerste dunne filmcellen, die in 1980 werden uitgebracht:s werd en gemaakt van amorf, unarranged totaal in het tegengestelde van kristallijn, silicium. De siliciumatomen liggen totaal ongestructureerd als volgt met een lagere rang van efficiency (ongeveer 9% is tot nu toe de maximum waarde). Dit feit wordt gecompenseerd door een aanzienlijke eenvoudigere, minder nodig grondstof en daarom lagere productiekosten.

In het eind van de jaren '80 overwoog men dat de amorfe siliciumcellen de techniek van de toekomst zouden zijn. De amorfe siliciumcellen verdroegen geen zonlicht, na enkel een paar maanden van gebruik, werd de rang van efficiency verminderd door 30%. Ondanks dit, worden de cellen gebruikt in zakcalculators, maar dat is allen.

De cellen van de CIS

Copper indium diselenide, een dunne filmcel die een rooskleurigere toekomst dan de amorfe siliciumcel heeft is Cel van de CIS , ťťn van de nieuwere producten. Het bestaat uit een diode met een n-gesmeerd cadmiumsulfide (CdS) en zinkoxyde (ZnO) als negatieve pool bovenop het lichte absorberende bed van de CIS . Het koper, het indium en het selenium (CuInSe2) maken tot 2-3 micrometer dikke film, die naam aan de cel gaf. De dioden plus pool wordt gecre?Žrd met een geleidende laag van molybdeen achter de laag van de CIS . De zonnecel, die gelijkstroom veroorzaakt, wordt gemaakt met vensterglas aangezien het aanvankelijke punt, bovenop dat, een dekking van molybdeen wordt geplaatst. Als amorfe siliciumcellen, eisen de cellen van de CIS zeer productie geen materiaal voor de energie die delen omzet. Dit is een bijdragende oorzaak in het belang van de cel die vanuit een economisch perspectief wordt gezien. Met massaproductie van de cellen van de CIS , zou de prijs ongeveer 400 SEK per vierkante meter volgens berekeningen vanaf de Amerikaanse energieafdeling zijn. De maximumrang van efficiency van een zonnecel met de technologie van de CIS in modules klaar om worden gebruikt bedraagt 11%. Dat is veel lager dan de kristallijne silicium cellen. De lengte van het leven voor een cel van de CIS heeft nog niet kunnen bepalen, aangezien zijn ontwikkeling hoofdzakelijk tijdens de jaren '90 is voorgekomen. Sommige negatieve milieu invloeden zijn reeds waargenomen in het cadmium en het indium dat is zou componenten in de de massaproductie van de CIS cell-a de activa van breekbaar indium verarmen. Bovendien, het is een bekend feit dat het zwaar metaalcadmium een negatieve invloed op de aard heeft.

De cellen van Grštzel

De g-Cel is nog een andere stap dichter aan de aard. De Zwitserse chemicus, Michael Grštzel, heeft begon van de fotosynthese in de zonnecel, begon zijn ontwikkeling in 1990. In de g-Cel is er een kunstmatige, rode kleurstof die photoenergy absorbeert. De kleurstof is gezet op uiterst kleine deeltjes van semiconductive titaniumdioxyde. Het voltage in de g-Cel daalt niet bij een lagere lichtintensiteit, in contrast aan zonnecellen van diodetype (de cellen van de CIS en siliciumcellen). Daarom kan het spoedig worden gebruikt in bijvoorbeeld wristwatches. Aangezien de g-Cel nog in een vroeg stadium van ontwikkeling is, zijn de gevolgen van gebruik op lange termijn niet praktisch getest. De Zwitserse wetenschappers hebben onlangs aangetoond dat de kleurstof minstens 15 jaar van blootstelling aan zonlicht duurt. De elektrolyt is een ander probleem, wanneer het tegen zowel lage als hoge temperaturen bestand moet zijn wanneer in openlucht gebruikt. Het moet ook non-polluting zijn met achting aan het oplosmiddel. De voordelen met dit soort een technologie zijn ook naast de flexibiliteit het vrij eenvoudige productieproces en de constant stijgende graad van efficiency (10% aan maximumtarief van zonlicht), die nog aanzienlijke lager is dan de cellen van de CIS . De voltooide zonnecellen zullen volgens de Zwitserse wetenschappers kosten rond 600 SEK per vierkante meter.

Tandem Cellen

De efficiency van de zonnecel wordt sterk verminderd afhankelijk van dat vele golflengten van lichte pas door het absorberende semiconductive materiaal. …ťn van de oplossingen voor dit probleem plaatst verscheidene zonnecellen bovenop elkaar; de lange golfstraling die niet door ťťn zonnecel kan worden geabsorbeerd, kan in plaats daarvan door een zonnecel worden gebruikt die achter eerste wordt geplaatst. Deze bouw staat samen meer dan drie cellen niet toe aangezien de verdere optische verliezen zich voordoen, meestal veroorzaakt door bezinning in de verschillende oppervlakten, wanneer verscheidene zonnecellen in een cel achter elkaar worden samengebracht. De materiŽle kosten stijgen natuurlijk met de hoeveelheid gebruikte lagen. De theoretische graad van efficiency is 40-45% en meer dan 30% is reeds verwezenlijkt bij praktische experimenten.

De cellen van Galliumarsenid (GaAs)

De cellen van Galliumarsenid kunnen een hoge concentratie, tot 2000 keer van het directe zonlicht dragen. Een efficiency van 23 percenten is bereikt, maar deze cellen zijn duurder dan siliciumcellen.

Het sulfide van het cadmium/kopersulfide (CdS/CuS)

De cellen die van cadmiumsulfide/kopersulfide hebben worden gemaakt veel lagere graden van efficiency en veel kortere lengte van het leven. Zij zijn hoewel goedkoper dan siliciumcellen.

De galvanische cellen van de foto

Als ťťn of beide elektroden in een elektrolytische oplossing verlicht is, zal een elektrisch voltage zich tussen de elektroden voordoen, en de stroom kan worden gehaald. De elektrolyt bevat een kleurstof, die een bepaald deel van het spectrum van het zonlicht kunnen absorberen, en ťťn of ander metaal die elektrolast opnemen en kunnen uitzenden.

Tot dusver, slechts kan een fractie van het licht worden gebruikt. De methode is nog op zijn basisonderzoeksfase.

De elektrolytische cellen van de foto

Als ťťn van de elektroden in een elektrolytische cel van een halfgeleider wordt gemaakt, kan de zuurstof dichtbij de halfgeleiderelektrode worden vrijgegeven wanneer het aan de zon wordt blootgesteld. De stroom van elektronen over aan de andere elektrode waar het waterstofgas wordt vrijgegeven. Als het halfgeleidermateriaal van titaniumdioxyde wordt gemaakt, kan een tarief van 10% van de zonne-energie worden gebruikt. De methode is nog op zijn basis onderzoeksfase.

Hoe te om de zonnecellen te gebruiken

Zodra er series van panelen in de zon zijn, regelen wij de macht en slaan het in grote krachtige batterijen op later te gebruiken. Dan gaan wij de gelijkstroom van elektriciteit door een apparaat genoemd over een omschakelaar. De omschakelaar verandert de elektriciteit in wisselstroom. Nu is er regelmatige elektriciteit!

De auto die nooit uit brandstof loopt

De elektrische auto's die met zonne-energie worden gedreven zijn nog een slecht alternatief aan regelmatige auto's. Rondom de fabrieken van de wereldauto concurreren over de productie van de snelste auto die slechts de stralen van de zon gebruikt zich vooruit te bewegen.

De zonneauto, aangezien wij de auto's kunnen roepen die direct met zonne-energie worden gedreven, zou ťťn van de toekomstige methodes kunnen zijn om de verontreiniging, vooral in de steden te verminderen. Maar misschien zal het realistischer met auto's zijn die met elektriciteit van het laden posten worden gedreven. Het zou een optie zijn om zonnecellen op het dak van de garage te hebben die verzamelen en de energie tijdens de dag opslaan en de auto tijdens de nacht laden. In de steden, kunnen de zonnecellen op de de torenblokken en contactdozen neer op de straat worden geplaatst waar de auto's kunnen aanvulling.

Het grote probleem is dat de elektriciteit van zonnecellen duurder is in aandeel tot andere gemeenschappelijkere energiebronnen.

De prijs op zonnecellen heeft begon te dalen, maar economisch gezien is het slechts winstgevend in speciale gevallen. Bijvoorbeeld zijn er zonnecellen op het dak van vele Noorse cabines op gebieden waar het zeer expansief is om elektriciteit te installeren. Maar de meer bespreking over zonne cellen, de meer ideeŽn zal worden getest en het onderzoek zal de prijzen van de zonnecellen verminderen.

De zonneautoconcurrentie

Elk derde jaar is er de concurrentie die tussen auto's wordt gehouden die met hulp van zonnecellen als enige het laden eenheid worden gedreven. De concurrentie wordt gehouden in AustraliŽ om duidelijke redenen, omdat de zonnecellen veel zon eisen om zo goed mogelijk te werken. De concurrenten zijn meestal niet de beste bestuurders en de voertuigen die winnen zijn niet noodzakelijk de snelste. U moet tactisch zijn en een auto bouwen die, duurt sinds wat voor veel van de concurrenten is het belangrijkst is doel te bereiken. Overwegend de energiebron, moet de zon, u zeggen dat de ? Uitdaging van de Auto van de Wereld Zonne? het zuiverste autoras in de wereld is.

De concurrentie

De concurrentie trekt concurrenten van rondom de wereld aan, aangezien het niet alleen de concurrentie maar ook een technisch avontuur is; een vrij undangerous manier om de grenzen uit te rekken en een manier om deuren voor de toekomst te openen. De fossiele brandstoffen de auto's vandaag worden gedreven waarmee, is berekend aan eind in een nabije toekomst, zodat misschien zijn de zonne gedreven auto's het antwoord in een toekomst zonder fossiele brandstoffen. Op die manier, de mensen die concurreren kunnen als pioniers worden gezien. De zonne celauto's zijn vandaag enkel een droom, omdat wij voldoende efficiŽnt niet hebben of goedkope zonnecellen en accumulatoren.



De concurrentie is over het reizen van de afstand van 3 000 km op de kortste mogelijke tijd. Het ras springt tussen Darwin en Adelaide, die ťťn van de dorste gebieden van de wereld is. De organisator en de stichter van de concurrentie, Hans Tholstrup, dreven vrij de afstand met zijn ?Uitvoerder? zodra 1982. De eerste concurrentie werd gehouden in 1987 en de winnaar was General Motors met ? Sunraycer ". Zij behandelden de afstand in ongeveer 45 uren, gelijkend op een gemiddelde snelheid van 67 km/h.

Milieu invloed

De zonne cellen behoren in de hoogste rang tot de vernieuwbare methodes om elektriciteit te veroorzaken - het zal miljarden jaren vergen alvorens de zon zijn eind als energiebron heeft bereikt. Er zijn ondanks alle positieve prognoses van wetenschappers zelfs sommige negatieve milieugevolgen, aangezien een uitgebreid gebruik van zonnecellen zou leiden tot. De opbrengst van volledige zonnecelsystemen eist heel wat energie en impliceert dat geen zeldzame grondstoffen wegens de zonne celproductie verdwijnen. De productie in deze overweging scheidt niet van het blijven de industrie. Ondanks dit, betekenen het lange de dienstleven van de zonnemodules en de korte tijd van de energieterugbetaling dat photovoltaic systemen een positieve energiebalans hebben. Een recyclingsinstallatie kan glas, silicium en aluminium, de belangrijkste componenten van de zonnemodules verwerken.

De kosten

De zonne-energie kost ergens rond 8 SEK/kWh, terwijl de kernmacht slechts 0.13-0.18 SEK/kWh kost. In de toekomst, met massaproductie, kunnen de zonnecellen zo goedkoop worden dat zij economisch winstgevend zullen zijn. Om een PV machtslevering te verstrekken geschikt om de vraag van kosten van een de typische binnenlandse energie efficiŽnte huis in het gebied van 200 000 SEK te ontmoeten. Hoewel dit vrij hoog kan schijnen, is het geen onredelijk deel van de kosten om een huis te bouwen.

Voordelen

De verontreiniging krijgt minste
De afhankelijkheid van ingevoerde brandstof wordt verminderd aangezien de zonne-energie een binnenlands soort energie is
De werkgelegenheidsstijgingen met binnenlandse productie
Een goed ontwikkelde zonne-energiemarkt kan de uitvoer tot inkomen leiden
De zonne panelen hebben een tijd met lange levensuur, minimum 25 jaar
De zonne-energiesystemen vergen zeer weinig onderhoud

Nadelen

De techniek is aan duur te vervaardigen en te installeren
Op in de Noordse landen er aan weinig zonnige dagen zijn om onze volledige behoefte van energie tevreden te stellen, zal er problemen tijdens de nachten en de winter zijn
De zonne celpanelen vereisen grote oppervlakten
Opslaan van elektriciteit is zeer moeilijk.
Het moet in andere vormen worden omgezet, die verliezen betekent

Conclusies

Hoewel economisch het nog niet een volledig gerijpte technologie is, is photovoltaic technologie nu op de drempel van een prestaties-aan-kosten vermogen dat het zou toelaten om significante vooruitgang op vele nieuwe marktgebieden te maken.

Met kosten die is elk photovoltaic jaar reeds commercieel rijp in vele verre toepassingen vallen, waar het met de hogere installatiekosten van lange verbindingen aan het net of de expansieve generatie van diesel reeksen kan concurreren. Dergelijke toepassingen omvatten reeds gezondheidszorg in de ontwikkelende wereld, telecommunicatierepeaters, kathodische bescherming van pijpleidingen, en mariene boeien.

Het gebruiken van zonne-energie, als bron van macht is uiteindelijk ťťn van de weinig energiebronnen die ons van energie op het niveau van vandaag kunnen voorzien!

Lijst van verwijzingen

www.geocities.Com/CapitolHill/3409/02_0022.htm
www.jaknet.jakgym.se/komvux/sindex.HTML
www.xpress.se/~gbgm0073/index.HTML
www.icomm.ca/~ee/folkkampanjen/fakta6.HTML
www.hj.se/~josv/energi.htm
www.hem1.passagen.se/aaked/solcell.htm
www.skolor.Lund.se/lerback/it/NoSo/alternativa.HTML
www.thn.edu.Stockholm.se/projekt/energi/solenergi/index.HTML
www.alt-energie.Com/catalogus/howsolarworks.HTML
www.solardirect.com/pv/pv.htm
www.flasolar.Com/photovol_main.htm
www.solarex.Com/solarfaq.htm
www.users.cybercity.dk/~lk5160/ukframes1.htm
www.nrel.regering/research/pv/tapsun.HTML



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De prijs op zonnecellen heeft begon te dalen, maar economisch gezien is het slechts winstgevend in speciale gevallen. Bijvoorbeeld zijn er zonnecellen op het dak van vele Noorse cabines op gebieden waar het zeer expansief is om elektriciteit te installeren. Maar de meer bespreking over zonne cellen, de meer ideeŽn zal worden getest en het onderzoek zal de prijzen van de zonnecellen verminderen.

De zonneautoconcurrentie

Elk derde jaar is er de concurrentie die tussen auto's wordt gehouden die met hulp van zonnecellen als enige het laden eenheid worden gedreven. De concurrentie wordt gehouden in AustraliŽ om duidelijke redenen, omdat de zonnecellen veel zon eisen om zo goed mogelijk te werken. De concurrenten zijn meestal niet de beste bestuurders en de voertuigen die winnen zijn niet noodzakelijk de snelste. U moet tactisch zijn en een auto bouwen die, duurt sinds wat voor veel van de concurrenten is het belangrijkst is doel te bereiken. Overwegend de energiebron, moet de zon, u zeggen dat de ?Uitdaging van de Auto van de Wereld Zonne? het zuiverste autoras in de wereld is.

De concurrentie

De concurrentie trekt concurrenten van rondom de wereld aan, aangezien het niet alleen de concurrentie maar ook een technisch avontuur is; een vrij undangerous manier om de grenzen uit te rekken en een manier om deuren voor de toekomst te openen. De fossiele brandstoffen de auto's vandaag worden gedreven waarmee, is berekend aan eind in een nabije toekomst, zodat misschien zijn de zonne gedreven auto's het antwoord in een toekomst zonder fossiele brandstoffen. Op die manier, de mensen die concurreren kunnen als pioniers worden gezien. De zonne celauto's zijn vandaag enkel een droom, omdat wij voldoende efficiŽnt niet hebben of goedkope zonnecellen en accumulatoren. De concurrentie is over het reizen van de afstand van 3 000 km op de kortste mogelijke tijd.

Het ras springt tussen Darwin en Adelaide, die ťťn van de dorste gebieden van de wereld is. De organisator en de stichter van de concurrentie, Hans Tholstrup, dreven vrij de afstand met zijn ?Uitvoerder? zodra 1982. De eerste concurrentie werd gehouden in 1987 en de winnaar was General Motors met ? Sunraycer ". Zij behandelden de afstand in ongeveer 45 uren, gelijkend op een gemiddelde snelheid van 67 km/h.

Milieu invloed

De zonne cellen behoren in de hoogste rang tot de vernieuwbare methodes om elektriciteit te veroorzaken - het zal miljarden jaren vergen alvorens de zon zijn eind als energiebron heeft bereikt. Er zijn ondanks alle positieve prognoses van wetenschappers zelfs sommige negatieve milieugevolgen, aangezien een uitgebreid gebruik van zonnecellen zou leiden tot. De opbrengst van volledige zonnecelsystemen eist heel wat energie en impliceert dat geen zeldzame grondstoffen wegens de zonne celproductie verdwijnen. De productie in deze overweging scheidt niet van het blijven de industrie. Ondanks dit, betekenen het lange de dienstleven van de zonnemodules en de korte tijd van de energieterugbetaling dat photovoltaic systemen een positieve energiebalans hebben. Een recyclingsinstallatie kan glas, silicium en aluminium, de belangrijkste componenten van de zonnemodules verwerken.

De kosten

De zonne-energie kost ergens rond 8 SEK/kWh, terwijl de kernmacht slechts 0.13-0.18 SEK/kWh kost. In de toekomst, met massaproductie, kunnen de zonnecellen zo goedkoop worden dat zij economisch winstgevend zullen zijn. Om een PV machtslevering te verstrekken geschikt om de vraag van kosten van een de typische binnenlandse energie efficiŽnte huis in het gebied van 200 000 SEK te ontmoeten. Hoewel dit vrij hoog kan schijnen, is het geen onredelijk deel van de kosten om een huis te bouwen.

Voordelen

De verontreiniging krijgt minste De afhankelijkheid van ingevoerde brandstof wordt verminderd aangezien de zonne-energie een binnenlands soort energie is De werkgelegenheidsstijgingen met binnenlandse productie Een goed ontwikkelde zonne-energiemarkt kan de uitvoer tot inkomen leiden De zonne panelen hebben een tijd met lange levensuur, minimum 25 jaar De zonne-energiesystemen vergen zeer weinig onderhoud

Nadelen

De techniek is aan duur te vervaardigen en te installeren Op in de Noordse landen er aan weinig zonnige dagen zijn om onze volledige behoefte van energie tevreden te stellen, zal er problemen tijdens de nachten en de winter zijn De zonne celpanelen vereisen grote oppervlakten Opslaan van elektriciteit is zeer moeilijk. Het moet in andere vormen worden omgezet, die verliezen betekent

Conclusies

Hoewel economisch het nog niet een volledig gerijpte technologie is, is photovoltaic technologie nu op de drempel van een prestaties-aan-kosten vermogen dat het zou toelaten om significante vooruitgang op vele nieuwe marktgebieden te maken.

End of Translation

Because of the refraction and spreading of the sunlight in the atmosphere all the solar radiation that reaches the surface of the earth is not parallel, some of it turns into diffuse light. The amount of diffuse light increases with the amount of water vapour, free drips of water and other particles in the air. In Sweden, the part of diffuse light reaches approximately 50% of the total incoming radiation. In the summer, the amount of the diffuse light is 20%, in the winter it is 80%.

How the photovoltaic cell works:

Solar cells are used to produce electricity directly out of the sunshine. The most common type of solar cells are made of silicium, or silicon as it also is called. When the solar cell is exposed to light, the front becomes negatively and the backside positively charged, the electrons start to wander and electricity is created. The best solar cells transform 20% of the sunshine to electricity. Within an individual silicon cell there are two layers of impure silicon. One side is doped with an element that tends to lose a valence shell electron and the other with one that needs one more electron to fill its valence shell, manufacturers often use boron and phosphorous. This sets up a situation where one side tends to be positive and the other negative. Where they meet is called the P/N-junction. One has a tendency to give up an electron and the other one to attract an electron. Light energy in the form of photons creates a movement of electrons across the P/N-junction. Each one of these cells is connected with other cells in series and in parallel to form a module. Modules are then grouped into arrays, which creates a large source of power. There are contacts on both sides of the cell that can be connected to a battery, a transformer or any other unit that accumulates or forwards the extracted energy. The contact on the side, which faces the sun, is constructed so the sunlight can reach the semiconductor plate, while the backside of the cell often contains wall-to-wall contact plate. Because of the contacts and the covering glass, the otherwise thin PV-cells gets a manageable thickness.

How to make a photovoltaic cell:

The top layer in a PV-cell must fulfil two important demands; it must let through as much sunlight as possible and also protect the PV-cell from being exposed to the clerk of the weather. As much of the solar energy as possible must pass through the top layer to the PV-cell itself. Each protective layer, which absorbs solar energy, reduces the effect of the PV-cell. The top layer must therefore be made of glass containing low percentage of iron. Etanvinylacetat, EVA, is a plastic material with good conductivity and relatively high melting point. EVA is the material, which is used to attach the protective glass to the PV-cell and also to attach the PV-cell to the material on the backside of the cell. A plastic material or a metal plate, for example aluminium, is used as a bottom plate. Metallic contacts are fastened on the PV-cell's upper and bottom side. The upper contact on the PV-cell is therefore attached to the lower contact on the next cell. This PV-cell module is placed between two layers of EVA plastic. Thereafter is the glass plate placed on top and the bottom plate below the module. This sandwich of several materials is placed in a hot vacuum chamber where all air bubbles are removed; the plastic melts and seals the spaces between the glass, the PV-cell and the bottom plate. If the air bubbles are not removed before the solar cell is sealed, they will surely expand in the warmth of the sun and thereby destroy the entire function of the photovoltaic cell.

Different types of PV-cells:

There are lots of different kinds of PV-cells. Below we have listed a few of them, new ones are constantly coming as a result of research. The efficiency and the price varies from model to model.

Crystalline silicium cells

Silicium cells are the solar cells that are the most common type today and in the future will be the most current because of the large amount of silicium. 27% of the surface of the Earth is made of silicium and the reachability is good. The very first commercial solar cells were used in space in 1958. The high manufacturing costs of those times were faced to even larger investments for use of nuclear power or fuel cells for the satellites. The solar cells were built up of two thin layers of silicium in crystalline form. During the 70's the same technique was introduced for production of electricity on ground level.
What is positive with the crystalline silicium cells is a relatively high degree of efficiency - the industrial manufactured cells have reached an efficiency of 20%. The negative side is the high cost for the semiconductor material even though it is very thin, only a tenth of a millimetre. The silicium material must also be extremely clean so it does not lower the grade of efficiency.
Today's modern crystalline silicium cells have with the avai
lable method of production and system solutions an energy cost of between 3 and 10 SEK/kWh why the competitive strength against electricity connected to the main system is minimal. The area of use has mainly been applications were other electricity is not available, for example: the archipelago, road signs, radio and telestations in the mountains and so on. Crystalline silicium cells have for long time been the only solar cells technique, and therefore a greater part of the worlds today 500 MW solar cells is made of crystalline silicium.

Amorphous silicium cells

The science direction towards cheaper solar cell electricity lead to a development of solar cells with lower consumption of material then the crystalline silicium cells. The first thin film cells, which were brought out in the 1980:s and were made of amorphous, totally unarranged in the opposite of the crystalline, silicium. The silicium atoms lie totally unstructured with a lower grade of efficiency as follows (approximately 9% is until now the maximum value). This fact is compensated by a considerable simpler, less raw material needed and therefore lower manufacturing cost. In the end of the 80's it was considered that the amorphous silicium cells would be the technique of the future. The amorphous silicium cells did not endure sunlight, after just a few months of use, the grade of efficiency was lowered by 30%. Despite this, the cells are used in pocket calculators, but that is all.

CIS cells

A thin film cell that has a brighter future than the amorphous silicium cell is the CIS cell, one of the newer products. It consists of a diode with an n-doped cadmium sulphide (CdS) and zinc oxide (ZnO) as the negative pole on top of the light absorbing CIS bed. Copper, indium and selenium (CuInSe2) makes the 2-3 micrometer thick film, that gave name to the cell. The diodes plus pole is created with a conductive layer of molybdenum behind the CIS layer. The solar cell, which produces direct current, is made with window glass as the initial point, on top of that, a cover of molybdenum is placed. As the amorphous silicium cells, the CIS cells do not demand very much manufacturing material for the energy transforming parts. This is a contributing cause in the interest of the cell seen from an economical perspective. With mass production of the CIS cells, the price would be about 400 SEK per square meter according to calculations from the American energy department. The maximum grade of efficiency of a solar cell with the CIS technology in modules ready to be used is at 11%. That is much lower than the crystalline silicium cells. The length of life for a CIS cell has not yet been able to determine, since its development has occurred mainly during the 90's. Some negative environmental influences have already been observed in the cadmium and the indium which are components in the CIS cell-a mass production would impoverish the assets of breakable indium. Besides, it is a known fact that the heavy metal cadmium has a negative influence on the nature.

Grštzel cells

The G-cell is yet another step closer to the nature. The Swiss chemist, Michael Grštzel, has began from the photosynthesis in the solar cell, its development began in 1990. In the G-cell there is an artificial, red colorant which absorbs the photoenergy. The colorant is seated on tiny particles of semiconductive titanium dioxide. The voltage in the G-cell does not drop at a lower light intensity, in contrast to solar cells of diode type (CIS cells and silicium cells). Therefore it can soon be used in for example wristwatches. As the G-cell still is in an early stage of development, the effects of long-term use have not been practically tested. Swiss scientists have recently showed that the colorant lasts for at least 15 years of exposure to sunlight. The electrolyte is another problem, when it must be resistant to both low and high temperatures when used outdoors. It also has to be non-polluting with regard to the solvent. The advantages with this kind of a technology are besides the flexibility also the relatively simple manufacturing process and the constantly increasing degree of efficiency (10% at maximum rate of sunlight), which still is considerable lower than the CIS cells'. The completed solar cells shall according to the Swiss scientists cost around 600 SEK per square meter.

Tandem cells

The efficiency of the solar cell is strongly reduced depending on that many wavelengths of light pass by the absorbing semiconductive material. One of the solutions to this problem is placing several solar cells on top of each other; the long wave radiation that can not be absorbed by one solar cell, can instead be utilized by a solar cell that is placed behind the first one. This construction does not allow more than three cells together since further optical losses arise, mostly caused by reflection in the different surfaces, when several solar cells are put together into a tandem cell. The material cost increases naturally with the amount of layers used. The theoretical degree of efficiency is 40-45% and more than 30% has already been accomplished at practical experiments.

Galliumarsenid cells (GaAs)

Galliumarsenid cells can bear a high concentration, up to 2000 times of the direct sunlight. An efficiency of 23 percent has been reached, but these cells are much more expensive than silicium cells.

Cadmium sulphide/copper sulphide (CdS/CuS)

Cells made of cadmium sulphide/copper sulphide have much lower degrees of efficiency and much shorter length of life. They are though cheaper than silicium cells.

Photo galvanic cells

If one or both electrodes in an electrolytic solution is illuminated, an electric voltage will arise between the electrodes, and electric energy can be extracted. The electrolyte contains a colorant, which can absorb a certain part of the sunlight's spectrum, and some metal that can take up and emit electrical charge. So far, only a fraction of the light can be used. The method is still on its basic research phase.

Photo electrolytic cells

If one of the electrodes in an electrolytic cell is made of a semiconductor, oxygen can be released near the semiconductor electrode when it is exposed to the sun. Electrons stream over to the other electrode where hydrogen gas is released. If the semiconductor material is made of titanium dioxide, a rate of 10% of the solar energy can be used. The method is still on its basic research phase.

How to use the solar cells

Once there are arrays of panels in the sun, we regulate the power and store it in large powerful batteries to be used later. Then we pass the direct current of electricity through a device called an inverter. The inverter changes the electricity to alternating current. Now there is regular electricity!

The car that never runs out of gas

Electric motor cars driven with solar energy are still a bad alternative to regular cars. All around the world car factories are competing about manufacturing the fastest car that only uses the beams from the sun to move forward. The solar car, as we can call the cars that are driven directly with solar energy, could be one of the future methods to decrease the pollution, especially in the cities. But perhaps it will be more realistic with cars driven with electricity from charging stations. It would be an option to have solar cells on the roof of the garage that collect and store the energy during the day and charge the car during the night. In the cities, solar cells can be placed on the tower blocks and sockets down on the street where the cars can be recharged. The big problem is that electricity from solar cells is more expensive in proportion to other more common energy sources. The price on solar cells has began to sink, but economically seen it is only lucrative in special cases. For example there are solar cells on the roof of many Norwegian cabins in areas where it is very expansive to install electricity. But the more talk about solar cells, the more ideas will be tested and the inquiry will lower the prices of the solar cells.

The Solar car competition

Every third year there is a competition held between cars that are driven with help from solar cells as the only charging unit. The competition is held in Australia for obvious reasons, because the solar cells demand lots of sun to work as good as possible. The competitors are mostly not the best drivers and the vehicles that win are not necessarily the fastest ones. You have to be tactical and build a car that lasts, since what is most important for many of the competitors is to reach goal. Considering the source of energy, the sun, you have to say that "The World Solar Car Challenge" is the purest car race in the world.

The competition

The competition attracts competitors from all around the world, since it is not just a competition but also a technical adventure; a pretty undangerous way to stretch the limits and a way to open doors to the future. The fossil fuels that cars today are driven with, is calculated to end in a near future, so perhaps solar driven cars are the answer in a future without fossil fuels. In that way, the people that compete can be seen as pioneers. Solar cell cars are today just a dream, because we do not have sufficiently effective or cheap solar cells and accumulators. The competition is about travelling the distance of 3 000 km on the shortest possible time. The race leaps between Darwin and Adelaide, which is one of the world's most arid areas. The organiser and founder of the competition, Hans Tholstrup, drove the distance with his " Quite Achiever" as early as 1982. The first competition was held in 1987 and the winner was General Motors with "The Sunraycer". They covered the distance in approximately 45 hours, similar to an average speed of 67 km/h.

Environmental influence

Solar cells belong in the highest grade to the renewable methods of producing electricity on - it will take billions of years before the sun has reached its end as an energy source. There are despite all the positive prognoses from scientists even some negative environmental effects, as an extensive use of solar cells would give rise to. The produce of entire solar cell systems demands a lot of energy and implies that no rare raw materials disappear because of the solar cell production. The manufacturing in this consideration does not part from remaining industry. Despite this, the solar modules' long service life and short energy payback time means that photovoltaic systems have a positive energy balance. A recycling plant can process glass, silicon and aluminium, the main components of the solar modules.

The cost

Solar energy costs somewhere around 8 SEK/kWh, while nuclear power only costs 0,13-0,18 SEK/kWh. In the future, with mass production, solar cells can become so cheap that they will be economically lucrative. To provide a PV power supply capable of meeting the demand from a typical domestic energy efficient house costs in the region of 200 000 SEK. Although this may seem quite high, it is not an unreasonable proportion of the cost of building a house.

Advantages

The pollution gets lesser The dependence on imported fuel is lowered since the solar energy is an domestic kind of energy The employment increases with domestic production A well developed solar energy market can create export income Solar panels have a long life time, minimum 25 years Solar energy systems need very little maintenance

Disadvantages

The technique is to expensive to manufacture and install Up in the Nordic countries there are to few sunny days to satisfy our entire need of energy, there will be problems during the nights and the winter Solar cell panels require large surfaces Storing electricity is very difficult. It has to be converted into other forms, that means losses

Conclusions

Although economically it is not yet a fully matured technology, photovoltaic technology is now on the threshold of a performance-to-cost capability that would permit it to make significant advances in many new market areas. With costs falling each year photovoltaic is already commercially mature in many remote applications, where it can compete with the higher installation costs of long links to the grid or expansive generation from diesel sets. Such applications already include health care in the developing world, telecommunications repeaters, cathodic protection of pipelines, and marine buoys. Using solar energy, as a source of power is in the long run one of the few energy sources that can supply us with energy on today's level!

List of references

http://www.geocities.com/CapitolHill/3409/02_0022.htm
http://www.jaknet.jakgym.se/komvux/sindex.html
http://www.xpress.se/~gbgm0073/index.html
http://www.icomm.ca/~ee/folkkampanjen/fakta6.html
http://www.hj.se/~josv/energi.htm
http://www.hem1.passagen.se/aaked/solcell.htm
http://www.skolor.lund.se/lerback/it/NoSo/alternativa.html
http://www.thn.edu.stockholm.se/projekt/energi/solenergi/index.html
http://www.alt-energy.com/catalog/howsolarworks.html
http://www.solardirect.com/pv/pv.htm
http://www.flasolar.com/photovol_main.htm
http://www.solarex.com/solarfaq.htm
http://www.users.cybercity.dk/~lk5160/ukframes1.htm

End of Translation

Because of the refraction and spreading of the sunlight in the atmosphere all the solar radiation that reaches the surface of the earth is not parallel, some of it turns into diffuse light. The amount of diffuse light increases with the amount of water vapour, free drips of water and other particles in the air. In Sweden, the part of diffuse light reaches approximately 50% of the total incoming radiation. In the summer, the amount of the diffuse light is 20%, in the winter it is 80%.

How the photovoltaic cell works:

Solar cells are used to produce electricity directly out of the sunshine. The most common type of solar cells are made of silicium, or silicon as it also is called. When the solar cell is exposed to light, the front becomes negatively and the backside positively charged, the electrons start to wander and electricity is created. The best solar cells transform 20% of the sunshine to electricity. Within an individual silicon cell there are two layers of impure silicon. One side is doped with an element that tends to lose a valence shell electron and the other with one that needs one more electron to fill its valence shell, manufacturers often use boron and phosphorous. This sets up a situation where one side tends to be positive and the other negative. Where they meet is called the P/N-junction. One has a tendency to give up an electron and the other one to attract an electron. Light energy in the form of photons creates a movement of electrons across the P/N-junction. Each one of these cells is connected with other cells in series and in parallel to form a module. Modules are then grouped into arrays, which creates a large source of power. There are contacts on both sides of the cell that can be connected to a battery, a transformer or any other unit that accumulates or forwards the extracted energy. The contact on the side, which faces the sun, is constructed so the sunlight can reach the semiconductor plate, while the backside of the cell often contains wall-to-wall contact plate. Because of the contacts and the covering glass, the otherwise thin PV-cells gets a manageable thickness.

How to make a photovoltaic cell:

The top layer in a PV-cell must fulfil two important demands; it must let through as much sunlight as possible and also protect the PV-cell from being exposed to the clerk of the weather. As much of the solar energy as possible must pass through the top layer to the PV-cell itself. Each protective layer, which absorbs solar energy, reduces the effect of the PV-cell. The top layer must therefore be made of glass containing low percentage of iron. Etanvinylacetat, EVA, is a plastic material with good conductivity and relatively high melting point. EVA is the material, which is used to attach the protective glass to the PV-cell and also to attach the PV-cell to the material on the backside of the cell. A plastic material or a metal plate, for example aluminium, is used as a bottom plate. Metallic contacts are fastened on the PV-cell's upper and bottom side. The upper contact on the PV-cell is therefore attached to the lower contact on the next cell. This PV-cell module is placed between two layers of EVA plastic. Thereafter is the glass plate placed on top and the bottom plate below the module. This sandwich of several materials is placed in a hot vacuum chamber where all air bubbles are removed; the plastic melts and seals the spaces between the glass, the PV-cell and the bottom plate. If the air bubbles are not removed before the solar cell is sealed, they will surely expand in the warmth of the sun and thereby destroy the entire function of the photovoltaic cell.

Different types of PV-cells:

There are lots of different kinds of PV-cells. Below we have listed a few of them, new ones are constantly coming as a result of research. The efficiency and the price varies from model to model.

Crystalline silicium cells

Silicium cells are the solar cells that are the most common type today and in the future will be the most current because of the large amount of silicium. 27% of the surface of the Earth is made of silicium and the reachability is good. The very first commercial solar cells were used in space in 1958. The high manufacturing costs of those times were faced to even larger investments for use of nuclear power or fuel cells for the satellites. The solar cells were built up of two thin layers of silicium in crystalline form. During the 70's the same technique was introduced for production of electricity on ground level. What is positive with the crystalline silicium cells is a relatively high degree of efficiency - the industrial manufactured cells have reached an efficiency of 20%. The negative side is the high cost for the semiconductor material even though it is very thin, only a tenth of a millimetre. The silicium material must also be extremely clean so it does not lower the grade of efficiency. Today's modern crystalline silicium cells have with the available method of production and system solutions an energy cost of between 3 and 10 SEK/kWh why the competitive strength against electricity connected to the main system is minimal. The area of use has mainly been applications were other electricity is not available, for example: the archipelago, road signs, radio and telestations in the mountains and so on. Crystalline silicium cells have for long time been the only solar cells technique, and therefore a greater part of the worlds today 500 MW solar cells is made of crystalline silicium. Amorphous silicium cells The science direction towards cheaper solar cell electricity lead to a development of solar cells with lower consumption of material then the crystalline silicium cells. The first thin film cells, which were brought out in the 1980:s and were made of amorphous, totally unarranged in the opposite of the crystalline, silicium. The silicium atoms lie totally unstructured with a lower grade of efficiency as follows (approximately 9% is until now the maximum value). This fact is compensated by a considerable simpler, less raw material needed and therefore lower manufacturing cost. In the end of the 80's it was considered that the amorphous silicium cells would be the technique of the future. The amorphous silicium cells did not endure sunlight, after just a few months of use, the grade of efficiency was lowered by 30%. Despite this, the cells are used in pocket calculators, but that is all.

CIS cells

A thin film cell that has a brighter future than the amorphous silicium cell is the CIS cell, one of the newer products. It consists of a diode with an n-doped cadmium sulphide (CdS) and zinc oxide (ZnO) as the negative pole on top of the light absorbing CIS bed. Copper, indium and selenium (CuInSe2) makes the 2-3 micrometer thick film, that gave name to the cell. The diodes plus pole is created with a conductive layer of molybdenum behind the CIS layer. The solar cell, which produces direct current, is made with window glass as the initial point, on top of that, a cover of molybdenum is placed. As the amorphous silicium cells, the CIS cells do not demand very much manufacturing material for the energy transforming parts. This is a contributing cause in the interest of the cell seen from an economical perspective. With mass production of the CIS cells, the price would be about 400 SEK per square meter according to calculations from the American energy department. The maximum grade of efficiency of a solar cell with the CIS technology in modules ready to be used is at 11%. That is much lower than the crystalline silicium cells. The length of life for a CIS cell has not yet been able to determine, since its development has occurred mainly during the 90's. Some negative environmental influences have already been observed in the cadmium and the indium which are components in the CIS cell-a mass production would impoverish the assets of breakable indium. Besides, it is a known fact that the heavy metal cadmium has a negative influence on the nature.

Grštzel cells

The G-cell is yet another step closer to the nature. The Swiss chemist, Michael Grštzel, has began from the photosynthesis in the solar cell, its development began in 1990. In the G-cell there is an artificial, red colorant which absorbs the photoenergy. The colorant is seated on tiny particles of semiconductive titanium dioxide. The voltage in the G-cell does not drop at a lower light intensity, in contrast to solar cells of diode type (CIS cells and silicium cells). Therefore it can soon be used in for example wristwatches. As the G-cell still is in an early stage of development, the effects of long-term use have not been practically tested. Swiss scientists have recently showed that the colorant lasts for at least 15 years of exposure to sunlight. The electrolyte is another problem, when it must be resistant to both low and high temperatures when used outdoors. It also has to be non-polluting with regard to the solvent. The advantages with this kind of a technology are besides the flexibility also the relatively simple manufacturing process and the constantly increasing degree of efficiency (10% at maximum rate of sunlight), which still is considerable lower than the CIS cells'. The completed solar cells shall according to the Swiss scientists cost around 600 SEK per square meter.

Tandem cells

The efficiency of the solar cell is strongly reduced depending on that many wavelengths of light pass by the absorbing semiconductive material. One of the solutions to this problem is placing several solar cells on top of each other; the long wave radiation that can not be absorbed by one solar cell, can instead be utilized by a solar cell that is placed behind the first one. This construction does not allow more than three cells together since further optical losses arise, mostly caused by reflection in the different surfaces, when several solar cells are put together into a tandem cell. The material cost increases naturally with the amount of layers used. The theoretical degree of efficiency is 40-45% and more than 30% has already been accomplished at practical experiments.

Galliumarsenid cells (GaAs)

Galliumarsenid cells can bear a high concentration, up to 2000 times of the direct sunlight. An efficiency of 23 percent has been reached, but these cells are much more expensive than silicium cells. Cadmium sulphide/copper sulphide (CdS/CuS) Cells made of cadmium sulphide/copper sulphide have much lower degrees of efficiency and much shorter length of life. They are though cheaper than silicium cells.

Photo galvanic cells

If one or both electrodes in an electrolytic solution is illuminated, an electric voltage will arise between the electrodes, and electric energy can be extracted. The electrolyte contains a colorant, which can absorb a certain part of the sunlight's spectrum, and some metal that can take up and emit electrical charge. So far, only a fraction of the light can be used. The method is still on its basic research phase.

Photo electrolytic cells

If one of the electrodes in an electrolytic cell is made of a semiconductor, oxygen can be released near the semiconductor electrode when it is exposed to the sun. Electrons stream over to the other electrode where hydrogen gas is released. If the semiconductor material is made of titanium dioxide, a rate of 10% of the solar energy can be used. The method is still on its basic research phase.

How to use the solar cells

Once there are arrays of panels in the sun, we regulate the power and store it in large powerful batteries to be used later. Then we pass the direct current of electricity through a device called an inverter. The inverter changes the electricity to alternating current. Now there is regular electricity!

The car that never runs out of gas

Electric motor cars driven with solar energy are still a bad alternative to regular cars. All around the world car factories are competing about manufacturing the fastest car that only uses the beams from the sun to move forward. The solar car, as we can call the cars that are driven directly with solar energy, could be one of the future methods to decrease the pollution, especially in the cities. But perhaps it will be more realistic with cars driven with electricity from charging stations. It would be an option to have solar cells on the roof of the garage that collect and store the energy during the day and charge the car during the night. In the cities, solar cells can be placed on the tower blocks and sockets down on the street where the cars can be recharged. The big problem is that electricity from solar cells is more expensive in proportion to other more common energy sources. The price on solar cells has began to sink, but economically seen it is only lucrative in special cases. For example there are solar cells on the roof of many Norwegian cabins in areas where it is very expansive to install electricity. But the more talk about solar cells, the more ideas will be tested and the inquiry will lower the prices of the solar cells.

The Solar car competition

Every third year there is a competition held between cars that are driven with help from solar cells as the only charging unit. The competition is held in Australia for obvious reasons, because the solar cells demand lots of sun to work as good as possible. The competitors are mostly not the best drivers and the vehicles that win are not necessarily the fastest ones. You have to be tactical and build a car that lasts, since what is most important for many of the competitors is to reach goal. Considering the source of energy, the sun, you have to say that "The World Solar Car Challenge" is the purest car race in the world.

The competition

The competition attracts competitors from all around the world, since it is not just a competition but also a technical adventure; a pretty undangerous way to stretch the limits and a way to open doors to the future. The fossil fuels that cars today are driven with, is calculated to end in a near future, so perhaps solar driven cars are the answer in a future without fossil fuels. In that way, the people that compete can be seen as pioneers. Solar cell cars are today just a dream, because we do not have sufficiently effective or cheap solar cells and accumulators. The competition is about travelling the distance of 3 000 km on the shortest possible time. The race leaps between Darwin and Adelaide, which is one of the world's most arid areas. The organiser and founder of the competition, Hans Tholstrup, drove the distance with his " Quite Achiever" as early as 1982. The first competition was held in 1987 and the winner was General Motors with "The Sunraycer". They covered the distance in approximately 45 hours, similar to an average speed of 67 km/h.

Environmental influence

Solar cells belong in the highest grade to the renewable methods of producing electricity on - it will take billions of years before the sun has reached its end as an energy source. There are despite all the positive prognoses from scientists even some negative environmental effects, as an extensive use of solar cells would give rise to. The produce of entire solar cell systems demands a lot of energy and implies that no rare raw materials disappear because of the solar cell production. The manufacturing in this consideration does not part from remaining industry. Despite this, the solar modules' long service life and short energy payback time means that photovoltaic systems have a positive energy balance. A recycling plant can process glass, silicon and aluminium, the main components of the solar modules.

The cost

Solar energy costs somewhere around 8 SEK/kWh, while nuclear power only costs 0,13-0,18 SEK/kWh. In the future, with mass production, solar cells can become so cheap that they will be economically lucrative. To provide a PV power supply capable of meeting the demand from a typical domestic energy efficient house costs in the region of 200 000 SEK. Although this may seem quite high, it is not an unreasonable proportion of the cost of building a house.

Advantages

The pollution gets lesser The dependence on imported fuel is lowered since the solar energy is an domestic kind of energy The employment increases with domestic production A well developed solar energy market can create export income Solar panels have a long life time, minimum 25 years Solar energy systems need very little maintenance

Disadvantages

The technique is to expensive to manufacture and install Up in the Nordic countries there are to few sunny days to satisfy our entire need of energy, there will be problems during the nights and the winter Solar cell panels require large surfaces Storing electricity is very difficult. It has to be converted into other forms, that means losses

Conclusions

Although economically it is not yet a fully matured technology, photovoltaic technology is now on the threshold of a performance-to-cost capability that would permit it to make significant advances in many new market areas. With costs falling each year photovoltaic is already commercially mature in many remote applications, where it can compete with the higher installation costs of long links to the grid or expansive generation from diesel sets. Such applications already include health care in the developing world, telecommunications repeaters, cathodic protection of pipelines, and marine buoys. Using solar energy, as a source of power is in the long run one of the few energy sources that can supply us with energy on today's level!

List of references

http://www.geocities.com/CapitolHill/3409/02_0022.htm
http://www.jaknet.jakgym.se/komvux/sindex.html
http://www.xpress.se/~gbgm0073/index.html
http://www.icomm.ca/~ee/folkkampanjen/fakta6.html
http://www.hj.se/~josv/energi.htm
http://www.hem1.passagen.se/aaked/solcell.htm
http://www.skolor.lund.se/lerback/it/NoSo/alternativa.html
http://www.thn.edu.stockholm.se/projekt/energi/solenergi/index.html
http://www.alt-energy.com/catalog/howsolarworks.html
http://www.solardirect.com/pv/pv.htm
http://www.flasolar.com/photovol_main.htm
http://www.solarex.com/solarfaq.htm
http://www.users.cybercity.dk/~lk5160/ukframes1.htm 




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