Solar panel

A solar panel or solar collector is a device intended to recover part of the energy of the solar Rayonnement to convert it into a form of energy usable by the man - electric or thermal.

One distinguishes primarily two types of solar panels:

the thermal solar panels, called thermal solar collectors , which convert the Lumière into Chaleur recovered and used in the form of warm water;
the photovoltaic solar panels, called photovoltaic modules , which convert the Lumière into electricity. The solar photovoltaic one is commonly called statement.

In both cases, the panels are usually flat, of a surface approaching the m ² more or less to facilitate and optimize the installation. The solar panels are the basic components of the majority of the equipment of production of solar energy.

The thermal solar panels are currently more profitable economically than the photovoltaic modules thanks to a high output bordering the 80% (see “thermal solar panel” on wikipédia and to visit the associated bond), however, recovered energy can generally be used only for the heating of the medical Warm water.

The interest to use photovoltaic solar panels appears quickly when it is known that a surface of 344 side km, could cover the totality of the world requirements in electricity: the output of a photovoltaic installation being estimated between 15 17% (in 2007 in Europe) is 160 kWh/an/m ² or 160 GWh/an/km ² with world needs estimated at 19.000 TWh (figure 2006).

Generally, it is considered that the totality of the surface of the correctly exposed and covered existing roofs of panels could be enough to satisfy the needs.

To estimate the potential of solar energy, it is enough to know that the totality of the solar energy received on the ground in a little less than one hour would make it possible, if it were recoverable entirely, to provide for the energy needs of humanity during one year.

Thermal solar panels

Photovoltaic solar panels

Influence sunning

On ground, average solar energy in full exposure received per m ² of panels exposed in full sun is of 1 kw, whereas in space the solar Constante is of 1,367 kW/m ². In spite of its name the solar constant is not really constant since the solar activity is not itself constant. The losses caused at the time of the crossing of the atmosphere by the light is such as the energy which arrives on the ground on ground is weaker and the average 1 of about kW/m ² at true midday. It is this value which is commonly retained for calculations. In laboratory to determine the output of a cell or a solar panel, an artificial solar energy source of 1 kw/m ² is also used. With final, the energy which arrives on the ground depends on the slope of the sun thus thickness of the atmosphere to cross and of its nebulosity.

Whereas this question can be studied more in detail on the site of the institute of solar energy (INNATE), the number of hours of equivalent full sun more particularly concerns the photovoltaic producer of electricity.

Before being equipped in photovoltaic panels, it is interesting to know what one can draw with the geographical place which concerns us. For that, the European Community put on line a free software which allows any citizen Union where that it is in the Community to know the sunning from which it will profit. After some tests to familiarize itself with this software, one discovers that in Liege one has 840 hours of sunning per annum, Hamburg 870, Colmar 940, Rouen 950, Munich 950, Arcachon 1100, Chamonix 1110, La Rochelle 1140, Agen 1150, Perpignan 1290, Eraklion Crête 1310, Madrid 1400, Cannes 1465, Seville 1470, Malta 1480, Faro Portugal 1550. These hours of sunning are hours are equivalent full sun . Indeed, a solar panel is only exceptionally exactly vis-a-vis the sun since the ground turns without stop and that the slope of the sun compared to the panel evolves/moves permanently. During one day without cloud the electric production of the panel varies also permanently according to the position of the sun and is never with its safe maximum with the short passage of full midday. The production in end-of-day is thus a sum of partial productions. In covered weather, therefore in the absence of sun, the ambient luminosity, whereas the sun is hidden, allows a very small electric production nevertheless, and these small added productions end up making kWh. At the end of the year starting from the total of the electric production one obtains the number of hours of equivalent full sun of the year which has nothing to do with the number of hours sunning to the direction weather.

The number of hours of sunning seen by the services weather or the climatologists is not of the same nature. Either there is sun or it is not. The chart of the sunning can be consulted here. It is noted that Rouen is located on the 1750 hour old line of sunning per annum, the 950 hours figure quite different of equivalent full sun of the producers of photovoltaic electricity Rouennais.

It would also be necessary to take account of the Albedo ground, i.e. of its capacity of reflection of the light. When an installation is surrounded of snow for example, therefore by a very reflexive environment, the production of an installation increases because it recovers a small portion of reflected light by snow around. But this variable is not easy to quantify and is, in fact, included in the number of hours of equivalent full sun.

Influence recent evolution of the outputs

In 1995, the outputs of the single-crystal panels were approximately 10%, into 2000 from approximately 12% and currently (2007) according to the manufacturers, from 15 to 17%. In 12 years, the growth of the outputs thus was of almost 60%.

To consider a production electric, it is thus necessary to know the sunning of the place but also the output of the panels. Once obtained the sunning of the place with the software of the European Community, it is enough to multiply it by the output of the panels to have the estimated annual electric production. Thus for Rouen with 950 H and of the panels of an output of 15%, one arrives to 1 kW/m ² X 950h/an X 0,15 = 142,5 kWh/an/m ². This production gets along at the exit of the panels, therefore does not take account of the losses in wire and during conversion into alternative electricity by the inverter.

One can as say as with an output of 15%, the power provided by a panel of 1 m ² is of 1 kw X 0,15 = 150 W. What gives a power of 150 WC (Crete Watt).

It is to better do calculation oneself even rather than to trust with those which were done at another time and taken again here where to check the dires of a fitter there without the detail of the elements taken into account being specified or quite simply. The speed of the recent evolution of the outputs makes obsolete very quickly of calculations carried out a few years ago only. As it is foreseeable that this tendency will continue in the years which come, to make its own calculation thus seems an attitude to be preserved.

However one can also calculate directly starting from the kWc: in Rouen, 1 kWc produces 950 kWh roughly per annum (1 kw X 950 H of equivalent full sun). This last calculation is independent of the surface of the panels and their output, data already taken into account to arrive at the kWc. The kWc or kilowatt peak still named kWp or kilowatt peak is the maximum capacity provided by a as well as possible exposed installation (in theory 1 kW/m ²) and represents only one particular case, the solar exposure being variable. Name kWc or kWp employed in photovoltaic industry is sometimes regarded as an abusive name because the electric output is usually expressed in kw.

To arrive at a power of 1 kWc with panels of an output of 15%, it is necessary: 1.000 W/150 W = 6,66 m ² of panels (or presented differently: 150 W per m ² X 6,66 m ² = 1.000 W for the 6,66 m ²). The more the output of the panels increases, the more surface necessary to obtain a power of 1 kWc decreases.

To consider the surface of panels desirable, the study of the spending patterns on a case-by-case basis is necessary. All also depends on the end result which one wants to obtain. One can want to produce only part of his consumption or to go until compensating for totality. One can even want to exceed his consumption and to become retailer Net.

There exist various types of photovoltaic solar panels:

Panels with mono or polycrystalline silicon

1 m ² of photovoltaic cells delivers a power from approximately 100 to 200 W following the technique and the outputs (one finds in the trade of the panels with outputs going from simple to the double).

With the moderated latitudes, the energy collected (production obtained) by the photovoltaic Solar panels in one year is about 150 kWh for one square meter (the outputs have increased for a few years and one now finds panels of an output of 15% or more). It does not remain about it less than the photovoltaic one is still expensive in spite of a regular fall of the prices.

The basic material intended to manufacture the cells constitutive of the photovoltaic solar panels is the Silicium. The natural Silicium is not usable directly and it must undergo some treatments because it is insulator electrical and it must become a Semi driver. It should initially be removed from the impurities that it contains. Then, it is necessary to reintroduce to him some atoms of Phosphore and Bore. The " part; dopée" with phosphorus becomes silicon " of N" type; and the doped part with boron of " P" type; (see the article on the semiconductor ).

The junction of the 2 types of silicon P and NR gives a semi driver usable is in electronics for the manufacture of the diodes; transistors; integrated circuits and microprocessors (commonly called chips), is for the manufacture of the solar panels.

The suppliers of silicon used to manufacture the cells of the photovoltaic solar panels were up to now exclusively the silicon manufacturers of the electronics industry. This electronic Silicium is pure to 99,999999%, purity required by the aforementioned industry. Recently (during 2006), another source of Silicium is used in solar industry: the metallurgical Silicon pure with 98%. This type of Silicon thus named by its usual use in metallurgical industry, has the advantages of being less expensive than the precedent and of spending less energy for its manufacture. This new source of matter usable after having undergone a suitable treatment to become solar Silicon of intermediate quality between the two Silicon referred to above, will in the long term make it possible cause a drop in the prices of the cells and panels without deteriorating technicality of it. For the year 2006, for the first time, photovoltaic industry consumed more Silicium that the electronics industry.

In 2006, the growth of the worldwide production of solar panels was slowed down for lack of silicon production capacity. A strong growth of the request involved an imbalance of the market. This request 2 times higher than the offer created a silicon shortage. Silicon production capacities are in fast increase in the world, but despite everything, one expects for 2007 and can be still until 2009 so that the shortage perdure. Without this difficulty of provisioning, the development of solar photovoltaic would have been spectacular, but nobody among the actors of the die had envisaged this passion which originates in the raising of prices of fossil energies.

Silicon is produced in the form of named bars “ingots” of round or square section. These ingots are then sawn in fine plates put at square so necessary the 200 microns thickness which are called “wafers”. After a treatment to inject on the surface of boron and phosphorus and thus to obtain conducting semi silicon, the wafers “are metallized”: metal ribbons are encrusted on the surface and are connected to electric contactors which will make it possible the electrons to circulate and produce electricity. Once metallized the wafers became photovoltaic cells.

The assembly of a group of cells connected between them inside a framework tight with the bad weather forms a Solar panel single-crystal or polycrystalline.

In the actual position of the things, a single-crystal photovoltaic panel with the electronic Silicium must function two years “to refund” the energy which was necessary to its manufacture (see Wikipédia on the photovoltaic cells). With technological advances in progress this period is in reduction. The single-crystal cells passed from 300 microns from thickness to 200 and one now thinks of quickly reaching the 180 then 150 microns, decreasing the quantity of silicon and energy necessary, but also the prices.

The production in ribbon is an innovation of “Evergreen Solar” a start up of Massachusetts born in 1994, with dimensions in Nasdaq and which produced 30 MW of solar cells with this technique in 2006. A film crosses a bath of Silicium melted and takes care on each one of its two faces of a layer of silicon. While cooling two ribbons of Silicium a thickness lower than 150 microns are formed. It is then enough to cut out with the laser these ribbons remotely regular to form squares of Silicium (wafers). This process has advantages: as of now the thickness of the cells is gone down in lower part 150 microns and there does not need more to saw the “ingots” from where economy thickness of the “kerfs”. There is thus a reduction in the quantity of Silicium necessary by suppression of the losses of sawing and a lower thickness of the wafers. For these two reasons the quantity of Silicium used is less and the time of electrical production by the panel to carry out the “refunding” of energy necessary to its manufacture is then gone down to 18 months. (source: Evergreen Solar). In his annual report with the shareholders of 2006, the 2nd world company of production of cells, the German company Q-concealments states to have begun it also the production in ribbon in a joint venture with Ervergreen Solar.

In his semi-annual report/ratio with the shareholders at the end of June 2007, this same company Q-concealments states to prepare with the production of single-crystal solar panels of an output of 21% and polycrystalline of 18% (numbered page 4), it envisages a silicon shortage until the end of 2009.

The polycrystalline solar panels still called multicristallins, are manufactured with a finer layer of Silicium from 15 to 50 microns according to the manufacturers. To save raw material, one uses a thin layer of Silicium, made up of a myriad of small crystals resulting from the falls and waste during work on single-crystal Silicium. This waste is placed in a crucible carried to a little more than 1.400 degrees to obtain an ingot Multicristallin. Doping and metallization as for the manufacture of the single-crystal Silicium follow.

The situation develops, rather than to start from a block of Monocristal expensive, one leaves now directly a source of solar Silicium of quality which one deposits on a support, the crystals are directed perpendicular to surface and not in a random way as in a true polycrystal. The thickness of the Silicium is then reduced towards the 10 to 30 microns. Processes were thus developed to manufacture crystals usable without passing by the ingots

In June 2007, the Mitsubishi manufacturer announced to be parvenu with an output of 18% with cells Polycristallines, that is to say the equivalent of the output of the current Japanese cells Monocristallines. Mitsubishi obtained this result mainly thanks to its research on the treatment of the surface of collecting of the light by reactive ion engraving which decreases the reflexivity of the light towards the atmosphere and consequently increases the quantity of absorptive light and transform in electricity. This new technological advance should allow the polycrystalline Solar panels to become more interesting than the single-crystal Panneaux. Until now they were less expensive but with outputs less (2006. The situation should thus develop clearly in their favor, if however their prices do not go up. The advantage of polycrystalline compared to the single-crystal one is that it produces only little cut scrap and that it requires less energy for its manufacture. For the moment (July 2007) the outputs of the polycrystalline solar panels sold in the trade rather have an output from 12 to 15%, it is at least what one finds in the catalog of Sharp the first global manufacturer (and). One thus sees well all the potential of commercial development of this technique in the immediate years to come and the manufacturers of polycrystalline Silicium invest in new production capacities (; and,).

In France, a project of factory baptized Silpro, dedicated to the manufacture of polycrystalline silicon is in hand and will see the day with Dignes the Baths in Provence.

One of the average employees to increase the productivity and to lower the prices of production is to manufacture cells increasingly larger and thus to decrease the number of handling. The cells passed from 125 × 125 mm in 2000 to 156 × 156 currently. In 2008 the German company Q-Concealments envisaged dimensions of 210 × 210 Misters.

Among the improvements in the course of the photovoltaic technique, one finds the addition on the surface of a film anti reflection (2005) which makes it possible to decrease the reference of luminous rays towards the atmosphere and thus to absorb most of luminous flow. Always in this way, a laboratory of Osaka treats the surface of the cells to obtain micro cavities intended to trap the light (2007).

Also, a team of the university of Sydney has makes a success of in May 2007 has to increase the output of part of the wavelengths of the light by depositing a money film on the surface of the cell. By heating it with 200 degrees the film is cracked in small units of 100 Nm on side. These money nanoparticules excites the plasmons of surface and increases the output of conversion of the light around the 1.200 Nm wavelength. The total output of the cell is some improved and would be changed to 24% instead of 17 to 18 with the current technique of doping to phosphorus and boron.

Reduction thickness of the lines of metallization, and by consequence, of the surface occupied by the " métallisation" of recovery of electricity belongs to the improvements in progress. Indeed more the metallized lines are fine, plus active surface increases at the same time as the output. Technique MWT (Metal Wrap Through) returns half of metallization on the back face decreasing by as much the metallization of the front face.

Panels with solar concentration

The Spectrolab company held the world records of the best output of conversion ever measured on a photovoltaic cell with 40,7% (announces in December 2006, homologation before an organization of American state in January 2007). This value was measured on a cell known as “multi-junction”, which consists of a stacking of several photovoltaic cells converting various parts of the solar spectrum: the cell top converts the energy photons, that of the medium converts the fairly energy photons, while the cell of bottom converts the big wavelengths, corresponding to the energy photons. This technology makes it possible to optimize the absorption of solar flow by the cell, and thus to increase its output of conversion significantly.

These cells consist of Gallium, of Gallium arsenide and Germanium. The multi-layer manufactoring process employed here quite simply takes again the technique of manufacture of the integrated circuits and the microprocessors controlled and optimized for a long time in addition.

Because of its raised cost price, this type of cell will be marketed in solar panels with concentration. Thus the quantity of cells will be decreased to the extreme since the solar concentration will be about 500. Commonly it is said that this cell will function with “500 suns”. In the same way the quantity of energy necessary to the manufacturing process strongly will drop since the quantity of cell will be decreased by the same factor as the solar concentration. The cost price of these panels, according to the advertisements which were made at the end of 2006, should be also directed with the fall.

The university of Delaware in July 2007 has just beaten the world records of the best output but this time with a solar system of concentration associated with a light decomposition of the light. What makes it possible to arrive to an output of 42,8% with 3 juxtaposed cells which convert into electricity each one a color. The concentration is less important: 20.

Europe which develops the project “full spectrum” in collaboration with the ECA for its part obtained an output of 35,2% in December 2006 with a technique which aims also to exploit more broad band of the spectrum of the light.

However, one should not confuse these results and advertisements records with the possibilities offered by an industrial production of mass which is rather at the level from the 30% of output with these systems with concentration announced with marketing for 2007 - 2008 in the United States and in Germany.

The German company Solar tce AG also developed a system with concentration. The current concentration of these panels is of 700, the objective of the company is now in the long term to arrive to a concentration of 10.000. It has another immediate objective: to arrive to an output of the panels (and not of the silicon cells which composes it) of 36%. Objective which still hides another for a more remote future of them: an output of its cells (and not of its panels) of 50%. None of these objective was quantified to term cost. She affirms that sleep and already with what exists she can lower the costs by 50% (last line).

Another American company, Soliant Energy, based in Pasadena California, also announce the production of solar panels with concentration for the end 2007. The solar concentrators will be this linear and noncircular time. There too the announced prices are directed largely with the fall compared to the existing techniques. Solient will work in partnership with MIT, to manage to improve the industrial techniques of production of these panels with concentration.

In the same way, the company Britannique Microsharp works with the development of solar panels with concentration with concentrators of a few microns (50 X 30 microns). The objective there is too to arrive to a significant decrease of the prices of this type of solar panels.

An American start up " solaria corporation" from California, subsidiary of Q-concealments will begin the production from solar panels with weak concentration (X 3) in 2008 (semi-annual report/ratio June 2007 of Q-concealments numbered page 5).

Another start up " sunflower" will put on the market in 2008 or 2009 of the cells at concentration which follow the sun in azimuth and height in an autonomous way. The solar concentration will be of 800 and the output of the cells used of 35%.

Panels with thin layers without silicon

Another technique makes it possible to do without silicon: a thin metal layer of 5 microns deposited on ordinary glass or a flexible support converts the light into electricity with an output slightly lower than that of the Silicium. Several alternatives exist: the CIS (Copper Indium Selenium), the DSCIG (DiSéléniure de Cuivre Indium Gallium), the DSSC (containing dioxide of Titanium), TeCd or CdTe (Tellurium of Cadmium) and others still. Many investments are in hand (2006 and 2007) in the United States (NanoSolar) and in Germany (where the journalists do not hesitate to speak about environment of gold rush).

An American start up, heliovolt, installed in Austin in Texas, will build a factory which will be operational in 2008 to produce cells IGC (copper, indium, gallium, sélénide) of an output of 11% in industrial production to start and which should reach between 13 and 15% in 2017. This type of cell in version " laboratoire" an output of 19,5% obtained: .

A concern however: raw material resources. These novel methods use rare metals as the Indium whose worldwide production is of 25 tons per annum and the price of April 2007 of 1000 dollars kg; the Tellurium whose worldwide production is of 250 tons per annum; the Gallium of a production of 55 tons per annum; the Germanium of a production of 90 tons the year. Although the quantities of these raw materials necessary to the manufacture of the solar cells are infinitesimal, a world massive development of the photovoltaic solar panels in thin layers without silicon would not fail to encounter this limited physical availability.

For the Indium, the technological institute of Tokyo developed a " colle" or " ciment" containing Alumina which replaces the Indium (March 2007). This alternative is ecological, cheap and its production could be much more important than that of the Indium him even. The success here consists in replacing the indium atoms by molecules which produce an equivalent result.

The usual production of Indium, Germanium and Gallium is done, inter alia, starting from the flue gases of the oil and the coal which contain some. The reprocessing of combustion gases of the powerplants to coal, necessary and of topicality due to climate change and production of gas to Greenhouse effect, being called to develop, the extraction of Indium, Germanium and Gallium could belong to the treatment of combustion gases of coal and thus develop well beyond what it is in the current location.

In the long term, it will be necessary to design and develop substitute products with all these too rare raw materials. There is one of the research topics here to be able to return the photovoltaic Solaire largely widespread and banal.

These rare matters when they result from recycling are often of less quality what affects their economic value and the profitability even of recycling. The recycling of these materials should be a major concern, and should be the economic strategy object of long run. There too it is a question of a subject of research to be developed for the safety of the future. Moreover, it could be a branch of industry of before guard and creator of employment.

On the other hand the doping of the Silicon, the Phosphorus and the Boron, are produced in sufficient quantities to supply the die of solar traditional with the Silicium, which is thus not, in the immediate future, threatened in his existence by the techniques of the thin layers without silicon for this reason, as opposed to what one can read or hear here or there.

Panels with thin layers with silicon

the amorphous cells, the microcrystalline cells, and the cells tandem include/understand known as micromorphes.

The cells with silicon Amorphe (silicon not crystallized and in an amorphous state) use a technique of layers much thinner than for the panels with the polycrystalline Silicium. But their vacuum manufacture and their low output do not make of it an alternative interesting for the moment. The amorphous cells have a thickness from 0,3 to 0,5 microns and an output of 6% or a little more. They absorb the photons of high energy a wavelength lower than 600 Nm of the green and blue colors.

The evolution towards the miniaturization of the crystals of the polycrystalline cells has leads to microcrystalline cells which have a thickness from 1 to 2 microns. The minicristaux ones encrusted in an amorphous matrix form a microcrystalline cell which absorb the luminous rays of 600 Nm and more, reds and will infra red with an output from 6 to 7%.

To Japan, solar panels produced starting from thin layers of a new type soon will be marketed (May 2007). It is about an amorphous combination of Silicium (If - has or has - If) and of silicon Microcristallin (µc - If). The constitutive cells are qualified cells tandem. This technique known as Micromorphe (contraction of 2 preceding names) would strongly decrease the dependence with the Silicium while making it possible not to have recourse to the rare matters. The setting out of tandem of amorphous and microcrystalline cells to form a micromorphe unit makes it possible to collect a broader spectrum of light and to obtain an output higher than 10%. With this type of cell, the output of conversion at the time of the weak sunnings is improved. The 2 amorphous and microcrystalline cells are put optically in series by successive deposits on a support. In Japan, this novel method is regarded as the new generation of panels in thin layers and the Mitsubishi company decided to install this type this panels on all the roofs of its production centres. In Switzerland the Oerlikon company considers that in 2020, the market of the panels with cells tandem will be of 30% of the totality of the photovoltaic market and it also begins marketing from it as of this year 2007. In its email with the shareholders of September 2007, the German company er Ground comes to announce its intention to stop the marketing of the amorphous cells to replace it by cells tandem, and this, since 2008.

The combination of various materials and various doping agents opens a vast choice with research to improve this technique in the future.

In October 2007, a start up Californienne, Inovalight, announced the development of a novel method of manufacture which would make it possible to divide the cost price of the solar panels of half. Moreover the output would be of 22% for this novel method with thin layers with silicon. Marketing would start in 2009.

The obstacle with the development: the storage of energy

The development of solar photovoltaic originated in the electrification of the sites isolated and not connected to the network, but also the mobile food of material. This need made it possible the incipient die to make year after year of progress in terms of cost price of produced kWh and output of the panels.

The solar electrical production is prone to the risks of the sunning and is not regular. The period of manufactures do not coincide at the periods of consumption and the night the production is null but not the needs. In the sites isolated and off-line to the network, one stores energy in batteries for stage this disadvantage. But it is an additional and considerable investment in term of cost and maintenance. In this particular case, the overcost is acceptable compared to price which it would have been necessary to put in the installation of an electric new line.

The current development of solar photovoltaic, is not justified any more by the needs for the sites isolated except in some countries like India. The current motivation is due to the foreseeable exhaustion of nonrenewable energies like oil, gas, coal, or the nuclear energy containing uranium or of thorium. Recently, mediatization helping, we start to become aware of it.

The world energy statistics of 2006 give a little more than 12% of renewable energies on the total of all the power consumptions. If we must be private nonrenewable energies, the world would have at its disposal only 12% of the energy which we currently spend. It would be a disaster. The economy would crumble and our lifestyles with, at least. That we are of agreement or not, gradually, the limited reserves of nonrenewable energies will end up becoming exhausted entirely and there will remain only renewable energies alone, it is a matter of time.

It is thus advisable to implement several policies: to save energy, to increase the Energy efficiency, to promote and develop quickly energies of replacement, commonly called “new renewable energies” (thus out the hydroelectricity and wood), of which the solar photovoltaic one forms part.

Certain countries already launched out in development programs of the renewable energies. It is the case of Denmark. The statistics of the installed capacities working out of wind mills in Denmark are the following ones: 2001 = 2,4 GW; 2002 = 2,8 GW; 2003 = 3,1 GW; 2004 = 3,1 GW; 2005 = 3,1 GW; 2006 = 3,1 GW. (many a site give statistics on energy, Eurobserver, BP, Enerdata or the IEA by ex). One sees according to these figures, that as from 2003 the Danish program was stopped. The Danish experiment shows that the direct injection (without storage of energy) in the electrical communication could not develop beyond 18% approximately consumption of the country. The Danish wind electrical production was into 2003 of 6,5 TWh on a total of consumption of 37 TWh. What gave 18% of electricity in direct injection on the network. One cannot retain this figure strictly, since the wind electrical production, at power installed given, varies one year on the other according to the conditions weather and the consumption of Denmark appreciably increases year after year. 18% are thus an indicative figure, but nevertheless significant.

With the experiment, outward journey beyond this figure poses large problems of management of the network. To go Denmark further lacked a storage system of electricity in mass, good market and nonaggressive for the environment.

It is thus well it not resolution of the storage of the electricity which stopped the Danish program in 2003. As for the wind one, the electrical production by solar panels will butt against this problem of storage in the long term. And it be found a solution well should since the progressive disappearance of nonrenewable energies will carry out us to produce 100% of our energy in renewable form, or else us will not be able to have electrical energy permanently (i.e. 24/24).

Germany has an active development program of wind and the solar photovoltaic one at the same time. This country became the 1st world one in these 2 dies. Whereas the renewable electrical production was of 8,5% of its electric production in 2003, the forecast for 2007 is of 14%. It is seen well that for this country also the problem of the storage of electricity soon will become crucial.

The tracks evoked in Germany to store electricity are the following ones: Technique of the “ pumping ” which consists to pump the water which runs downstream from the hydroelectric stoppings and to drive back it upstream, therefore to go up water in the stoppings, by pumps, so that Ci passes by again one later on 2nd time in the turbines. The Germans think of developing this technique with wind mills whereas in France it is practiced with the nuclear plants, of night during the falls of consumption. This technique already used with the nuclear power because of the lack of agreement between the production and consumption (STEP of Large-House of 1.800 MW, therefore of a power of 2 nuclear reactors) could be also used with wind electricity for the same reason. The production of compressed air by wind mills instead of producing electricity. In the nacelle of the wind mill instead of installing an electric generator, the installation of a compressor of air makes it possible to produce then to store compressed air which one can use later on to actuate an electric generator. A project is under development in the North Sea. The production of hydrogen with electricity would make it possible to store energy in the form of hydrogen for a use according to the needs. All the wind energy which could be stored will release the networks of as many undesirable fluctuations of power to be able to continue to develop the production of solar photovoltaic in direct injection. Thus it is noted that certain solutions with the storage of electrical energy are common to the development of wind and of solar photovoltaic the .

The storage of electrical energy in batteries of the type VRB starts to be employed in Japan and in Australia. This Canadian technique makes it possible to store great quantities of electricity, but does not answer yet the criterion of low cost price. It is in study to be used in installations solar photovoltaic to make them autonomous.

None of these solutions evoked here is for the moment really satisfactory in term of cost and final cost price of kWh. On the other hand, on the purely technical level the last experience feedback on an attempt aiming at the 100% of renewable electrical production of origin , initiated in 2006 at the request of Mrs. Merkel, shows that it is possible to reach that point. What could in the long term make it possible to make Germany completely independent in energy. One can directly consult on this subject either the report/ratio in German, or in reading a French report here: .

In France, we do not have absolutely these problems nor these questions, the photovoltaic electrical production in isolated site is still higher than the production of the installations in direct injection on the network. Even if in 2007 the situation is in the course of quick change.

The batteries of storage follow a continuous technological change and progress is important.

Whereas the lead-acid batteries have a capacity of 30 Wh per kg, other types developed:

nickel - cadnium (Ni-Cd) 50 Wh per kg
1st die lithium (Ni - MH) 75 Wh per kg
lead 2nd generation (2006) 75 Wh per kg *système streaked: sodium - nickel chloride 85 Wh/kg
1st die lithium - ion of 1992 (Li - Ion) 90 Wh per kg
sodium - suffers (Na S) 107 Wh/polymeric kg
lithium (Li - Po) 120 Wh per kg
lithium - ion 2nd generation (2000) 150 Wh per kg
zinc - agent (2007) 200 Wh per kg * manganese - lithium - ion; also called lithium - manganese (2007) 300 Wh per kg * lithium - suffers from 2007 (Li - S) 300 Wh/kg
lithium - vanadium + of 300 Wh /kg (but how much exactly? ) presented by Subaru in 2007: * vanadium redox or VRB (1998): no theoretical limit of storage capacity, but with a technical limit in the current location of 100 MWh,

currently they are used for the storage of great capacities in the wind one and are being studied for photovoltaic residences of private individuals by a German company of solar photovoltaic.

powder of ceramics - aluminum (EEstor in the United States): They should be used initially for the electric cars, then later for the storage of energy applied to wind and the solar one.
condensing - lithium - ion (FHI): in test in Japan.

Working installed capacities photovoltaic

Various cumulated powers installed at the end of 2006:

world 6.700 MW
Europe 3.418 MW
Germany 3.063 MW
Japan 1.750 MW
the United States 610 MW
Spain 118 MW
France 32 MW

The world forecast for 2007 is of 9.000 MW

principal companies of the sector

- silicon producers

REC, Norway (but head office in the United States). 1st world with 6.500 T in 2006 and 13.000 T envisaged in 2007. Also manufacture cells, wafers and panels.
Wacker, Germany. 2nd world producer with 5.600 T in 2006 and 10.000 T envisaged in 2008.
Hemlock, the USA. 3rd world with 3.600 T in 2006 and 7.500 T envisaged in 2008.
but also: Crystallox, Scanwafer, statement silicon, Hoku materials, Sichuan Xinguang, Luyang Zhonhui, Emei, Sharp, Technip, Orkla, Ferroatlantica, Metallurgija, Hycore… etc

- producers of cells

Sharp, Japan. 1st world producer with 600 MW in 2006 and 710 envisaged in 2007
Q concealments, Germany. 2nd world producer with 420 MW in 2006 and 540 MW envisaged in 2007.
but also: Suntech power, Schott, Isofoton, ErSol, DelSolar, Photowatt, Photovoltec, Sunways, Topray Solar, Nanjing statement-tech, REC, KIS Co, Solland, Solartec Sro… etc

- photovoltaic producers of solar panels

Sharp, Japan. 1st world producer with 600 MW in 2006 and 710 MW envisaged in 2007 (produced silicon, the cells and the panels).
Suntech Power, China. 2nd world with 270 MW in 2006 and 330 MW envisaged in 2007. Manufacture also cells.
but also: BP solar, Trina Solar, Yingli Solar, Sanyo, Deutshe solar, Kyocera, First Solar, Mitsubishi, Motech, SolarWorld, Shell Solar, Aleo Solar, Solarwatt, Scheuten Solar, Sunpower corp, Solar Fabrik, Tenesol, Evergreen Solar, Honda Soltec, Kaneka, Scancell, Shenzen Topray, Ningbo Solar, And Dynamics, General Electric, Solterra, Shanghai Solar, Sunset, Solon… etc

Prices

The cost price of photovoltaic kWh decreases on average by 5% per annum for a long time thanks to the technical innovations. But in the 2006 and 2007 tendency was stopped by a rise on bottom of silicon shortage, allowing to the producers silicon to re-examine their selling prices largely with the rise. This shortage should still last between 1 to 2 years according to the various opinions of the actors of the die and should be only one provisional interruption of the bearish tendency.

The forecasts of prices given by various companies of the sector all are largely directed with the fall, thus, the American start up heliovolt announces for 2010 a price of kWh of 15 cts of dollar, therefore of 11 cts of euro:

Thanks to the various technical evolutions, the average quantity of silicon necessary to the manufacture of 1 kWc, all confused techniques, was in reduction of approximately 1 kg per annum these last years. Until now, each time the production of panels doubled, the cost prices decreased by 20%. One thus sees well that the policies of incentive by subsidies installation by various countries make it possible this die more quickly to become profitable. For the new installations of each year, Germany, the world leader on the surface installed, decreases the price of repurchase of photovoltaic kWh to follow the fall of the cost prices of these new installations; contractual tariffs of the installations of the previous years remaining unchanged in addition. The development assistances of this die by a price of repurchase “helped” by the state, thus decrease year after year per m ² installed; what allows, constant budget, to subsidize each year a surface installed increasingly larger.

Among the elements which influence the cost price of the kWc installed, one finds: size of the installation (an installation of 10 kWc will cost less by kWc posed than an installation of 3 kWc); installation integrated into the roof or in overtaxation (the overtaxation costs less, but it is necessary to be certain state of the roof, because if it is necessary to intervene later on on the roof located under the panels, it will be necessary to deposit and put back the solar panels to repair the roof); the quality of the frame and the roof (a roof not perfectly plane will raise more difficulties during the installation integrated or not); the installation on the ground on supports adapted for this purpose will make it possible to obtain a still lower price. In France it is integration in roof which makes it possible to obtain the best resale price to the network. To calculate the cost price of produced kWh, one divides the price of the installation by his production over 25 years.

Production of panels CIS with begun at the beginning of 2007. With this technique the semi material conducting reactive with the light decreases spectacularly in thickness since it passes from 200 or 150 microns to 5 microns (in research one is gone down to 1,25 micron). When the industrial process of deposit of such a thin layer is improved by the experiment and the training, it is provided that the cost price of the photovoltaic solar panels will be able to drop by a factor 3 or 4. Right now (March 2007) the cost price of the kWc posed is in fall from 30 to 40% compared to the technique of the panels to the Silicium. Whereas the selling price of kWh is of 33 cts, the cost price of same kWh is estimated at 15 cts in the solar power station of Held up (), while the price with the meter is of 19 cts in Germany. In addition, and for comparison, an Israeli project of solar power station of another type, envisages a cost price of kWh of 12,5 cts, but with a much better sunning.

The prices of manufacture of these panels CIS at the exit machine being destined for strongly dropping in the few years which come, it seems well that this novel method is intended to hustle the established order. Indeed the German private individuals profiting in addition from subsidies will be able to produce with their installations of roof of electricity at a low price with that of their meter. The elements allowing a spectacular takeoff of solar photovoltaic seem joined together well in Germany.

In Japan, the subsidies will be removed soon. With a price of kWh to the meter from 22 to 25 cts according to the cases, the photovoltaic individual one is already competitive since less expensive than the price with the meter. The sale in large surface of do-it-yourself, of solar panels at very competitive prices also allows a car extremely interesting installation.

In France, on the one hand the prices of the solar installations are much higher than in Germany (page 19) and on the other hand the price of kWh to the meter is definitely lower thanks to many assumptions of responsibility by the state, at various levels, of the nuclear die, the conditions of a true starting of the solar die are thus less favorable. However the estimates by projection made by the ECA concerning the prices of the WC (Crete Watt) at the exit of factory arrive at 1,6 cts in 2010, which would carry, taking into account marketing and of the price of the installation, photovoltaic kWh with 13 - 14 cts approximately at that time, and this, without subsidy. By these projections towards the future, one guesses that the photovoltaic one will end up being essential and largely developing, not only by concern ecological or environmental, but quite simply because it should end up becoming the least expensive energy source.

The cost of photovoltaic can be calculated differently according to certain opinions, of which that the INNATE ones. The investment taking place at the beginning, it is necessary to carry out a calculation of actualization ata rate of X %, by ex 3% (from which it would be advisable to deduce the taxation). Indeed all occurs as if the current were paid then the money advances some is depreciated with time. For example, for the power station of Held up, the investment is of 130 million euros, at the end of 20 years, by holding account that the money loses 3% of its value per annum, 130 million euros 2007 will correspond to a cost of 260 million euros of 2027 with this date 800 million kWh will have been produced, that is to say approximately 30 cts of euros per kWh. However, this last way of calculating does not hold account owing to the fact that in the 20 years which follow the investment, the cost of kWh also will increase him and follow at least inflation and certainly much more being given the energy problems to come. In fact nobody can envisage which will be the final profitability of a financial placement, quite simply because nobody can predict neither the world future economic nor the cost to come from the energy, of which in particular the price of kWh to the meter in 20 years. In addition, this type of calculation could be applied to other forms of energy like the nuclear power, but curiously it is never done. One can thus wonder which is the motivation hidden behind this approach.

Research and development

- An international team of researchers directed by Junko Yano and Vittal Yachandra of Lawrence Berkeley National Laboratory to California east managed to detail the molecule which allows the photolysis of water during photosynthesis. The hope is of being able to synthesize it, which would make it possible to control the production of hydrogen by the sun. In this case, one could consider solar installations in roof of two types:

of the photovoltaic panels producing of electricity;
of the solar panels producing of the hydrogen which could then provide electricity when the sun is absent.

Such an installation of solar hybrid should approach us individual energy autonomy by the solar one if this research succeeds.

- Another step consists in transforming the frequencies of part of the spectrum of the light. The wavelengths of the green, not very energy, would be transformed into energy wavelengths of blue thus making it possible to increase the final output of the cells.

- A research team of the university of Sydney synthesized molecules of the type Chlorophylle which are able to transform the light into electricity. These molecules made up of a hundred porphyrins imitate the natural systems of photosynthesis. Conversion light/electricity is more effective with molecules of a size of half the wavelength of the absorptive light. Porphyrin consists of 4 pennies units of Pyrrole joined on the carbon atoms by 2 hydrogen bridges and 2 others of nitrogen/hydrogen. The pyrrole is of formula C4 NR H5. The constitutive atoms are thus carbon, nitrogen, hydrogen; current, spread matters and very good market.

- American research of Wake Forest University, led to cells: organics to leave silicon, coaxial and nonplane to increase the solar exposure some is the orientation of the sun, with reflection starting from the heart to make pass 2 times the light in the active part. These cells of laboratory have an output of 6% and are qualified ITO (Indium Chock Oxide: indium, tin, oxide)

- Other research on the cells in thin layers CIS (Copper Indium Sulphurizes this time), tries an assembly multi-layer to increase the outputs.

- A research team of Rice University of Houston the USA, succeeded in synthesizing a new type of Semi driver which is a promising candidate with the manufacture of the solar panels. She synthesized tétrapodes containing Séléniure of cadmium smaller than of the alive cells thanks to the nanotechnologies. The output of the chemical reaction is of 90%. This new Semi driver containing these tétrapodes could revolutionize the design of the solar cells. But there is far between these discoveries and experiments of laboratory and a concrete industrial application.

- A university of Trondheim in Norway, states to work on cells of 3rd generation which should have a theoretical yield of 60% and of 40% in practice.

- Research on the coproduction of heat and electricity or Thermophotovoltaïque (TPV) is always in hand.

- Researchers of Illinois announced in September 2007 to have found a film of nanoparticules allowing to recover the ultra-violets and to improve conversion of the reds, thus allowing an increase in the output of the cells.

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