Recycling is an important industrial process that can reduce energy usage, air and water pollution and save money. So, recycling should be considered in any kinds of materials that will be employed in industrial or home applications. Recycling is not successful for all mate‐ rials. Recycling of plastics, for example, is very problematic, but glass can successfully be re‐ cycled. Aluminium is the most successful material in recycling. Its recycling is much cost saving process as producing aluminium goods from recycled aluminium cost less than 10% of producing from bauxite ore. Low melting point is the main cause for cost-saving property of aluminium recycling [49]

## **2.5. Photovoltaic modules and corrosion**

The performance of solar fields and their power sale revenue are directly dependent on the reflectivity (for solar thermal) and solar panel absorptivity (for solar PV). Unfortunately the mirrors and panels are subjected to exposure to dust moisture and aerosols resulting in a significant drop in system efficiency [76].

Field data has shown that without any external cleaning, reflectivity dropped off with time at a rate of 0.45 percentage points per day and a loss of 16 percentage points in a month (figure 8). Currently the mirrors are cleaned using demineralized water by high pressure spray, deluge type cleaning methods, and fixing of piping spray systems. These methods, however, require demineralized water in the order of 0.23gallons/m2 of the area [77].

**Figure 8.** a): Schematic sample setup of the photoelectrochemical cells using nanocrystalline TiO2. The arrows indicate the direction of incident light [79]. (b): SEM micrographs of a sol-gel TiO2 layer with a thickness of 5 μm on an ITO glass substrate. (a) surface (magnification 15000). (b) cross section (magnification 9000) [79].

Due to high accumulation rate of dust large quantities of water are require. The washes un‐ fortunately recovered only 1-3% of the loss in reflectivity. Photovoltaic systems use semiconductor technology in dust and moisture laden region such as the east coast of Saudi Arabia. There is insufficient experience in dust laden and moisture laden region and the problem is very serious. It has been stated that the accumulation of dust on a PV panel caus‐ es a loss of 0.5% in PV efficiency. Currently commercially available films have a barrier property of water vapor transmission rate of 10-3g/m2 per day or one thousand gram square meter per day at 90%. The barrier oxide film therefore develops cracks and pinholes. The life of PV cell is drastically reduced in desert with expended span of humidity and suspended particles (SO2, NOX, Cl) [78].

The harsh environment has put a serious demand for fabrication of moisture resistant, cor‐ rosion resistant, water and dust repellent surface to prevent PV cells and module. This prob‐ lem needs three approaches,

**a.** A dry approach

As mentioned before, these calculations are based on the assumption that the proportion of used aluminium in solar systems will not increase. Considering the growth of aluminium usage in solar systems during the last years, however, clarifies that the solar industries pre‐ fer to use extruded aluminium instead of steel frames. Consequently, demands for alumini‐

According to the report of International Energy Agency published in 2010 [47], about 14GW energy are produced by photovoltaic solar system in the world. It also is predicted that the average capacity of this solar system will be 87GW in 2020, 225GW in 225 and 597GW in 2050. Based on this prediction, total amount of aluminium used in photovoltaic solar system will be 3, 7 and 19 million tons in 2020, 2030 and 2050, respectively. Consequently, 0.64% of total annual aluminium production will be used in PV systems in decade 2010-2020, which

Temperature is another important factor in efficiency of the photovoltaic solar systems. Re‐ searches have revealed that increasing temperature reduces the efficiency of PV solar cells. So, it is important to set a cooling system for PV cells, which provide an excellent opportuni‐

Another advantage of aluminium over other kinds of materials that encourages many com‐ panies in different fields, especially in solar power systems, to use this metal and its alloys is

Recycling is an important industrial process that can reduce energy usage, air and water pollution and save money. So, recycling should be considered in any kinds of materials that will be employed in industrial or home applications. Recycling is not successful for all mate‐ rials. Recycling of plastics, for example, is very problematic, but glass can successfully be re‐ cycled. Aluminium is the most successful material in recycling. Its recycling is much cost saving process as producing aluminium goods from recycled aluminium cost less than 10% of producing from bauxite ore. Low melting point is the main cause for cost-saving property

The performance of solar fields and their power sale revenue are directly dependent on the reflectivity (for solar thermal) and solar panel absorptivity (for solar PV). Unfortunately the mirrors and panels are subjected to exposure to dust moisture and aerosols resulting in a

Field data has shown that without any external cleaning, reflectivity dropped off with time at a rate of 0.45 percentage points per day and a loss of 16 percentage points in a month (figure 8). Currently the mirrors are cleaned using demineralized water by high pressure spray, deluge type cleaning methods, and fixing of piping spray systems. These methods,

of the area [77].

however, require demineralized water in the order of 0.23gallons/m2

will reach to 1.21% in decade 2020-2030 and 1.63% in period of 2030-2050.

ty for aluminium to extend its role in solar cells in near future [75].

successful and cheap recycling process for aluminium.

of aluminium recycling [49]

**2.5. Photovoltaic modules and corrosion**

significant drop in system efficiency [76].

um related to steel will increase in the course of time.

336 Aluminium Alloys - New Trends in Fabrication and Applications

**b.** A wet approach

## *2.5.1. The dry approach*

This approach is based on surface modification without using water. In certain cases the sur‐ face chemistry may be modified by applying low pressure compressed air and installing the system against the direction of winds, and creating conditions which do not allow the dust particles to settle down. Nanostructured surface could be created with ultra-fine grain size which may provide self-cleaning.

### *2.5.2. The Wet approach*

The wet approach would depend on fabricating hydrophobic films. One good example is provided by Titanium dioxide films for photovoltaic cells derived from a sol-gel process.[79]

Figure 8 describes the set-up of photo electrochemical cells using nano crystalline TiO2. A sol-gel process is used for spin coating. After being sensitized with a type the films are for transport of electrons in the photo electrochemical cells.

The particles having a size of ~ 100nm. In this process the heating process and application of TiO2 coating by spin coating technique needs to be controlled to produce high efficiency. The demand to produce dust and water repellent coatings is increasing because of its appli‐ cation in MEMS/NEMS and photovoltaic cells. However a considerable progress has been made in producing hydrophobic and dust repellent coating. The best symbol of hydropho‐ bicity is lotus leaf which exhibits water repellent and self-cleaning characteristic. A detail study of lotus leave shows two levels of structures a nano like hair structures with wax cov‐ ering the surface and micro scale mounds protruding from the surface figure 9 [80].

Attempts have been made to fabricate nano coatings with inherent self-cleaning properties. The lotus coating is microscopically thin and optically transparent. The coating sheds dust particles utilizing anti- contamination and self-cleaning properties. It is designed to preserve optimum long time performance. The coating can be applied to metal glass surface and ep‐ oxy composite substrates. In a desert there may be no rain, however, this technology needs to be complemented by dust management technologies which include, electro dynamic dust shields, thermal control systems and surface power systems. Tribo electric charging has been conducted under Mars surface conditions. The charging showed that large amounts of dust could be accumulated [81].

The super hydrophobicity or wettability is characterized by contact angle formed a liquid droplet and solid surface. A surface is consider hydrophobic if the water contact angle (WCA) is greater than 90ο and super hydrophobic if the WCA is between 150ο and 180ο . The contact angle hysteresis is the difference between the advancing angle (*ϕadv*) receding (*ϕrec*) contact angles. Roughening a surface enhances its water repellent property. The effect of surface roughness has been described by different theories [82].

**Figure 9.** a) Lotus leaves, which exhibit extraordinary water repellency on their upper side. (b) Scanning eletron micro‐ scopy(SEM) image of the upper leaf side prepared by glycerol substitution shows the hierarchical surface structure consisting of papillae,wax clusters and wax tubules. (c) Wax tubules on the upper leaf side. (d) Upper leaf side after critical point (CP) drying. The wax tubules are dissolved, thus the stomata are more visible. Tilt angle 150. (e) Leaf un‐

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339

derside(CP dried) shows convex cells without stomata [80].

*Cosϕw* =*γCosϕy*

Where *ϕw* and *ϕy* are contact angle on the rough and smooth surface and γ is the roughness factor define as the ratio of solid-liquid area ASL to the projection on a flat plane Af .

*2.5.1. The dry approach*

*2.5.2. The Wet approach*

which may provide self-cleaning.

338 Aluminium Alloys - New Trends in Fabrication and Applications

dust could be accumulated [81].

*Cosϕw* =*γCosϕy*

transport of electrons in the photo electrochemical cells.

This approach is based on surface modification without using water. In certain cases the sur‐ face chemistry may be modified by applying low pressure compressed air and installing the system against the direction of winds, and creating conditions which do not allow the dust particles to settle down. Nanostructured surface could be created with ultra-fine grain size

The wet approach would depend on fabricating hydrophobic films. One good example is provided by Titanium dioxide films for photovoltaic cells derived from a sol-gel process.[79]

Figure 8 describes the set-up of photo electrochemical cells using nano crystalline TiO2. A sol-gel process is used for spin coating. After being sensitized with a type the films are for

The particles having a size of ~ 100nm. In this process the heating process and application of TiO2 coating by spin coating technique needs to be controlled to produce high efficiency. The demand to produce dust and water repellent coatings is increasing because of its appli‐ cation in MEMS/NEMS and photovoltaic cells. However a considerable progress has been made in producing hydrophobic and dust repellent coating. The best symbol of hydropho‐ bicity is lotus leaf which exhibits water repellent and self-cleaning characteristic. A detail study of lotus leave shows two levels of structures a nano like hair structures with wax cov‐

Attempts have been made to fabricate nano coatings with inherent self-cleaning properties. The lotus coating is microscopically thin and optically transparent. The coating sheds dust particles utilizing anti- contamination and self-cleaning properties. It is designed to preserve optimum long time performance. The coating can be applied to metal glass surface and ep‐ oxy composite substrates. In a desert there may be no rain, however, this technology needs to be complemented by dust management technologies which include, electro dynamic dust shields, thermal control systems and surface power systems. Tribo electric charging has been conducted under Mars surface conditions. The charging showed that large amounts of

The super hydrophobicity or wettability is characterized by contact angle formed a liquid droplet and solid surface. A surface is consider hydrophobic if the water contact angle

contact angle hysteresis is the difference between the advancing angle (*ϕadv*) receding (*ϕrec*) contact angles. Roughening a surface enhances its water repellent property. The effect of

Where *ϕw* and *ϕy* are contact angle on the rough and smooth surface and γ is the roughness

factor define as the ratio of solid-liquid area ASL to the projection on a flat plane Af

and 180ο

.

. The

(WCA) is greater than 90ο and super hydrophobic if the WCA is between 150ο

surface roughness has been described by different theories [82].

ering the surface and micro scale mounds protruding from the surface figure 9 [80].

**Figure 9.** a) Lotus leaves, which exhibit extraordinary water repellency on their upper side. (b) Scanning eletron micro‐ scopy(SEM) image of the upper leaf side prepared by glycerol substitution shows the hierarchical surface structure consisting of papillae,wax clusters and wax tubules. (c) Wax tubules on the upper leaf side. (d) Upper leaf side after critical point (CP) drying. The wax tubules are dissolved, thus the stomata are more visible. Tilt angle 150. (e) Leaf un‐ derside(CP dried) shows convex cells without stomata [80].

$$\gamma = \frac{A\_{SL}}{A\_f}$$

According to Wenzel, the space between protrusions is filled by liquid. Cassie and Baxter model [83] assumed that air trapped by asperities of hills on the surface and a composite interface is formed. The composite interface may form air pockets trapped in the cavity. The relationship between apparent contact angles Cβ and ideal contact angle is given by

PFPE film was applied by spin coating (3000 rpm). Curing was done for C9F20 at 80o

films have been formed by control of hydrolysis and condensation reaction.

**Sols Composition Catalyst pH surface bonds after etching**

A TEOS,MPS HCL 2 Si-O, Si-OH B TEOS,MPS HCL 6 Si-O, Si-OH C TEOS NH4OH 10 Si-O2, Si-OH

lane, hydro phobicity followed the order C, B and A.

are extensively reported in literature. Optically transparent super hydrophobic silica based

In a work under taken [89] three types of originally modified silica gels have prepared as

After mixing, the surface chemistry was modified with self assembles monolayers using chlorotrimethylsilane (CTMS) (CH3) (SiCl) and tetra fluorotetrahydroxydimethylchloro si‐

Substrate of soda lime glass coated with a thin layer of tin oxide was doped with fluorine (SnO2:T). The transparent conductive oxide (TCO) form, the contact for the solar cell layers de‐ posited on tin oxide. An ethylene vinyl acetate provides both electrical isolation between solar cells and binds the glass back sheet to the module. An extruded aluminum sheet provides structured mounting points and grounding points. Damp heat tests were applied to the mod‐ ules [90]. A voltage of +600V was applied to the output of one modules and -600V to the other module. The modules work placed in an environmental chamber. Module biased at -600V (amorphous silicon) visible damage occurred. Modules subjected in positive bias showed no or little damaged. The dependence of corrosion damage to polarity suggests the reaction of Na

 of the glass with fluorine. Humidity acts as an electrolyte for corrosion to take place. Virtual‐ ly no damage was observed under positive biased polarity. the positive biase only reacts with

Electrochemical corrosion is the result of transport of metal ions between the cell and module frame. under the influence of large cell frame voltage(100-500-V) cell frame voltage present in applications with high system voltages above or below the ground potential [90].The problem is being solved with microencapsulation with low conductivity and control of ionic conductiv‐ ity of encapsulated free surface and interface. The leakage current is highly dependent on ion‐ ic conductivity and moisture level. The transport of ionic elements is associated with corrosion of internal cell material by leakage of current from the cell string to the module exterior. Both

contaminants outside the glass surface and does not need the mobility of ion.

processes electro migration and ionic migration need to be controlled [91].

observed (fig 11). It was shown that water vapor enhance the leakage of current [89].

on subjecting the modules to -600v and 85% RH at 85,72 and 60 o

. Sol get process titanium coating have been produced and they

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PDMSVT and PFPE at 120o

**Table 3.** Types of Modified Silica Gel

+

shown in the Table 3.

C and

341

C/ leakage current were

*CosCβ* =*rf fCosϕf* + ( *f* −1)

Where rf indicates roughness factor of the wetted area and f is the area fraction of the pro‐ jected wet area. The product rf is called solid fraction of limit f reached to zero the macro‐ scopic contact angle Cβ approaches to 180o leading to a super hydrophobic behavior. If *ϕr* is high, the drop would be in a Cassie and Baxter and low it would be Wenzel region. Both regions are shown in figure 10 [84].

**Figure 10.** Irreversible Transition from the Cassie State to the Wenzel State by the Wicking Test [84].

Two methods are in used for fabrication of super hydrophobic surface; a) making a surface with low energy materials or making a rough surface and coating with low surface materials like tetrafluoroethylene (TEFLCN) or polydimethylsiloxanes (PDMS).

Modifications of a surface with low energy compounds the process such as plasma etching [85] laser etching [86] chemical etching [87] lithography [88] and sol get techniques have been used to produce super hydrophobic surfaces.

Wet coating techniques have been used with success to obtain super hydrophobic surfaces base the critical factor is the preparation of an optimal rough surfaces. Processes such as sand blasting and annealing have been used to obtain a rough surface with grain size in nano dimension [88].

In a study on making a super hydro surface on aluminum samples were mechanically pol‐ ished to obtain a rough surface in the range of 0.05 to 1.5μm. The surface was modified by treating polydimethyl siloxane vinylterminated (PDMSVT) with 1 weight % Curing agent as cross linked perfluoroethylene (PFPE).

PFPE film was applied by spin coating (3000 rpm). Curing was done for C9F20 at 80o C and PDMSVT and PFPE at 120o . Sol get process titanium coating have been produced and they are extensively reported in literature. Optically transparent super hydrophobic silica based films have been formed by control of hydrolysis and condensation reaction.

In a work under taken [89] three types of originally modified silica gels have prepared as shown in the Table 3.

**Table 3.** Types of Modified Silica Gel

*γ* = *ASL Af*

Where rf

*CosCβ* =*rf fCosϕf* + ( *f* −1)

jected wet area. The product rf

regions are shown in figure 10 [84].

scopic contact angle Cβ approaches to 180o

340 Aluminium Alloys - New Trends in Fabrication and Applications

According to Wenzel, the space between protrusions is filled by liquid. Cassie and Baxter model [83] assumed that air trapped by asperities of hills on the surface and a composite interface is formed. The composite interface may form air pockets trapped in the cavity. The

high, the drop would be in a Cassie and Baxter and low it would be Wenzel region. Both

indicates roughness factor of the wetted area and f is the area fraction of the pro‐

is called solid fraction of limit f reached to zero the macro‐

leading to a super hydrophobic behavior. If *ϕr* is

relationship between apparent contact angles Cβ and ideal contact angle is given by

**Figure 10.** Irreversible Transition from the Cassie State to the Wenzel State by the Wicking Test [84].

like tetrafluoroethylene (TEFLCN) or polydimethylsiloxanes (PDMS).

been used to produce super hydrophobic surfaces.

cross linked perfluoroethylene (PFPE).

nano dimension [88].

Two methods are in used for fabrication of super hydrophobic surface; a) making a surface with low energy materials or making a rough surface and coating with low surface materials

Modifications of a surface with low energy compounds the process such as plasma etching [85] laser etching [86] chemical etching [87] lithography [88] and sol get techniques have

Wet coating techniques have been used with success to obtain super hydrophobic surfaces base the critical factor is the preparation of an optimal rough surfaces. Processes such as sand blasting and annealing have been used to obtain a rough surface with grain size in

In a study on making a super hydro surface on aluminum samples were mechanically pol‐ ished to obtain a rough surface in the range of 0.05 to 1.5μm. The surface was modified by treating polydimethyl siloxane vinylterminated (PDMSVT) with 1 weight % Curing agent as After mixing, the surface chemistry was modified with self assembles monolayers using chlorotrimethylsilane (CTMS) (CH3) (SiCl) and tetra fluorotetrahydroxydimethylchloro si‐ lane, hydro phobicity followed the order C, B and A.

Substrate of soda lime glass coated with a thin layer of tin oxide was doped with fluorine (SnO2:T). The transparent conductive oxide (TCO) form, the contact for the solar cell layers de‐ posited on tin oxide. An ethylene vinyl acetate provides both electrical isolation between solar cells and binds the glass back sheet to the module. An extruded aluminum sheet provides structured mounting points and grounding points. Damp heat tests were applied to the mod‐ ules [90]. A voltage of +600V was applied to the output of one modules and -600V to the other module. The modules work placed in an environmental chamber. Module biased at -600V (amorphous silicon) visible damage occurred. Modules subjected in positive bias showed no or little damaged. The dependence of corrosion damage to polarity suggests the reaction of Na + of the glass with fluorine. Humidity acts as an electrolyte for corrosion to take place. Virtual‐ ly no damage was observed under positive biased polarity. the positive biase only reacts with contaminants outside the glass surface and does not need the mobility of ion.

on subjecting the modules to -600v and 85% RH at 85,72 and 60 o C/ leakage current were observed (fig 11). It was shown that water vapor enhance the leakage of current [89].

Electrochemical corrosion is the result of transport of metal ions between the cell and module frame. under the influence of large cell frame voltage(100-500-V) cell frame voltage present in applications with high system voltages above or below the ground potential [90].The problem is being solved with microencapsulation with low conductivity and control of ionic conductiv‐ ity of encapsulated free surface and interface. The leakage current is highly dependent on ion‐ ic conductivity and moisture level. The transport of ionic elements is associated with corrosion of internal cell material by leakage of current from the cell string to the module exterior. Both processes electro migration and ionic migration need to be controlled [91].

Numerous experiments have been conducted on module, fabricated on the oxide coated glass and operated at voltages and elevated temperatures in a humid climate. The phenom‐ ena of electrochemical corrosion appeared to be in all cases related to humidity. Experi‐ ments conducted BP Solar a-Si/a- SiGe tendem module fabricated on tin-oxide coated glass and encapsulated with another sheet of glass with EVA, showed that sodium reacted with water to form sodium hydroxide and hydrogen and highly alkaline solution PH>9 such that sodium hydroxide will dissolves Silicate glass rapidly at temperature (≥ 100°C).

**Material Thickness(mm) WVTR(g/m2d)**

ed polymer. The peel strength for different back sheets is shown in Table 5.

**Material t=0 t=1week t=2weeks**

Uncoated PET 1-1.7 ― ~ 0.8 NREL coated PET 7-8 7.10 6.5-6.8 TPE ― ― ~4.0

These back sheets can be used as a substitute for glass if they resist the ingress of moisture and transport of current. The treated polymer has a dramatic improvement over the untreat‐

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343

**Figure 11.** A cross section of a PV module constructed with an SnO2:F transparent conducting oxide(TCO) layer depos‐ ited on a glass superstrate. The active semiconducting layers are deposited over the tin oxide, and the entire package is encapsulated with ethylene vinyl acetate (EVA) between another sheet of glass. Not shown are the laser scribes that form the individual solar cells connected in series. Five possible current paths between the frame and the TCO are illus‐ trated (1) along the surface and through the bulk of the glass superstrate, (2) along the glass superstrate-EVA inter‐ face, (3) through the EVA bulk,(4) along the glass backsheet-EVA interface and through the EVA bulk, and (5) along

the surface and through the bulk of the glass backsheet, and through the EVA bulk [95].

NREL coated PET 0.18 0.1-0.2 Tedlar / PET/ EVA (TPE) 0.2 3.0 PET 0.1 3.4 EVA 0.4-0.5 27-33

**Table 4.** WVTR for Polymer laminates at 37.8o and 85% Relative humidity

Tedlar/ Al/Tedlar C 0.1

**Table 5.** Peeling Strengths

In addition, the generation of hydrogen bonds near the interface may lead to a weakening of interfacial bonds because of reduction of tin-oxide. The relative durability of Zinc Oxide ap‐ peared to be due to the fact that Zinc oxide is not reduced [92].

A common observation in all investigations shows that corrosion can be minimized by use of low alkali or high resistivity glass, by increasing the adhesion of the transparent conduct‐ ing oxide to the glass surface or using zinc oxide rather than tin-oxide as a transparent con‐ ductive contact. The use of anti-reflection coated (ARC) glass is being used in an increasing percentage of PV modules due to expected high power energy output. The use of ARC glass declined because of the inability of the coating to maintain performance over long period of time. Recent progress made has given some confidence to the consumers to use it again. Several defect such as coating degradation, soiling and optical degradation have been ob‐ served. Recent progress in ARC glasses has been shown by ARC glass is developed by the sun power. It has been shown that a well-designed ARC coating protected the glass from humidity and sand blasting, whereas the uncoated glass showed chippings. More than three years of field data showed that the energy gain from ARC significantly exceeded by 3.5 to 5% over uncoated glass which is the consequence of the improved coating gains in diffuse and off angle lights, due to effect of refractive index and light scattering within the coating. The sun power modules are slowly emerging in the market.

Metal electro migration is a big concern in electronic industry along with corrosion, module and discoloration. The metal migration reduces the service life of module. SAFlex PS-41 is the first module to be produced to suppress electro migration by exploring the activity of embedded encapsulation which prevents electro migration when in contact with metals such as silver, copper and nickel. The first encapsulant Saflex PS41 is specifically designed to protect against metal diffusion from solar cell stacks, adhesive and bus ribbons [93].

Whereas enough evidence has been shown how the adverse effects of humidity vapor pres‐ sure and current leakages on the glass substrate the back sheet materials in ARC also play a pivotal role. In recent year high moisture barrier and high resistivity coatings on polyethy‐ lene terepthalate (PET) have been fabricated for application in PV module back sheet appli‐ cation. It is necessary for the back sheet completely insulating to prevent a conduction path from the back contact to the grounded metal frame. To prevent the penetration of moisture and create low water vapor transmission rates WVTR, g/m2 , d., cost effective coatings have been created on inexpensive polymers such as polyethylene terepthalate (PET) and biaxial oriented polypropylene (BOPP). Table 4 shows the thickness and transmission rates of vari‐ ous coatings applied PET [94].

**Table 4.** WVTR for Polymer laminates at 37.8o and 85% Relative humidity

These back sheets can be used as a substitute for glass if they resist the ingress of moisture and transport of current. The treated polymer has a dramatic improvement over the untreat‐ ed polymer. The peel strength for different back sheets is shown in Table 5.

**Table 5.** Peeling Strengths

Numerous experiments have been conducted on module, fabricated on the oxide coated glass and operated at voltages and elevated temperatures in a humid climate. The phenom‐ ena of electrochemical corrosion appeared to be in all cases related to humidity. Experi‐ ments conducted BP Solar a-Si/a- SiGe tendem module fabricated on tin-oxide coated glass and encapsulated with another sheet of glass with EVA, showed that sodium reacted with water to form sodium hydroxide and hydrogen and highly alkaline solution PH>9 such that

In addition, the generation of hydrogen bonds near the interface may lead to a weakening of interfacial bonds because of reduction of tin-oxide. The relative durability of Zinc Oxide ap‐

A common observation in all investigations shows that corrosion can be minimized by use of low alkali or high resistivity glass, by increasing the adhesion of the transparent conduct‐ ing oxide to the glass surface or using zinc oxide rather than tin-oxide as a transparent con‐ ductive contact. The use of anti-reflection coated (ARC) glass is being used in an increasing percentage of PV modules due to expected high power energy output. The use of ARC glass declined because of the inability of the coating to maintain performance over long period of time. Recent progress made has given some confidence to the consumers to use it again. Several defect such as coating degradation, soiling and optical degradation have been ob‐ served. Recent progress in ARC glasses has been shown by ARC glass is developed by the sun power. It has been shown that a well-designed ARC coating protected the glass from humidity and sand blasting, whereas the uncoated glass showed chippings. More than three years of field data showed that the energy gain from ARC significantly exceeded by 3.5 to 5% over uncoated glass which is the consequence of the improved coating gains in diffuse and off angle lights, due to effect of refractive index and light scattering within the coating.

Metal electro migration is a big concern in electronic industry along with corrosion, module and discoloration. The metal migration reduces the service life of module. SAFlex PS-41 is the first module to be produced to suppress electro migration by exploring the activity of embedded encapsulation which prevents electro migration when in contact with metals such as silver, copper and nickel. The first encapsulant Saflex PS41 is specifically designed to

Whereas enough evidence has been shown how the adverse effects of humidity vapor pres‐ sure and current leakages on the glass substrate the back sheet materials in ARC also play a pivotal role. In recent year high moisture barrier and high resistivity coatings on polyethy‐ lene terepthalate (PET) have been fabricated for application in PV module back sheet appli‐ cation. It is necessary for the back sheet completely insulating to prevent a conduction path from the back contact to the grounded metal frame. To prevent the penetration of moisture

been created on inexpensive polymers such as polyethylene terepthalate (PET) and biaxial oriented polypropylene (BOPP). Table 4 shows the thickness and transmission rates of vari‐

, d., cost effective coatings have

protect against metal diffusion from solar cell stacks, adhesive and bus ribbons [93].

sodium hydroxide will dissolves Silicate glass rapidly at temperature (≥ 100°C).

peared to be due to the fact that Zinc oxide is not reduced [92].

342 Aluminium Alloys - New Trends in Fabrication and Applications

The sun power modules are slowly emerging in the market.

and create low water vapor transmission rates WVTR, g/m2

ous coatings applied PET [94].

**Figure 11.** A cross section of a PV module constructed with an SnO2:F transparent conducting oxide(TCO) layer depos‐ ited on a glass superstrate. The active semiconducting layers are deposited over the tin oxide, and the entire package is encapsulated with ethylene vinyl acetate (EVA) between another sheet of glass. Not shown are the laser scribes that form the individual solar cells connected in series. Five possible current paths between the frame and the TCO are illus‐ trated (1) along the surface and through the bulk of the glass superstrate, (2) along the glass superstrate-EVA inter‐ face, (3) through the EVA bulk,(4) along the glass backsheet-EVA interface and through the EVA bulk, and (5) along the surface and through the bulk of the glass backsheet, and through the EVA bulk [95].

The above coating shows good adhesion, weather ability and low water vapor transmission rates. These coatings have a good adhesion to EVA after UV or damp heat exposure. The amount of water vapor that diffuses into EVA controls the stability of glass EVA surface. It may that glass/ EVA interface favors condensation reactions and the hydrolysis reactions are difficult to achieve. The exact mechanism is not known, however it is confirmed by research studies that humidity and leakage current play a very predominant role in degradation of PV modules. The important pathways are showing figure 11 [95].

**2.6. Importance of dust**

tal factors as shown in figure 13 [96].

figure 12 [96].

Dust is a term which is applied to solid particle with less than 500μm. The main sources of dust are; dust laden winds, volcanic eruptions etc. It also includes micro pollens, microfiber, which are scatter with atmosphere. The factors influence the dust settlements are shown in

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345

Dust promotes dust. It settles in region of low vapor pressure induced by the high pressure movements on inclined /vertical surface. The PV system is affected by several environmen‐

**Figure 13.** Alterable and unalterable factors determining maximum PV system yield [96].

In a study H-V induces leakage current from eight modules, a pair from each module type of C-Si, Pc-Si. (Bulk Si) and tendem junction and multi-junction a-Si were monitored for eight years. It was observed that the leakage currents from C-Si Pc-Si module were thermal‐ ly activated and the activation energy varied with RH ranging from 0.86-1.0ev at high RH to 0.8ev as low RH. The leakage currents for a-si modules were much lower than bulk Si mod‐ ules by a factor of 10 to100 times. After operation of HV tests for 24 hrs a day the loss rates were 0.0% year for pL –s, 0.1% year for c-s, (positive polarity) between 0% as 0.05% year for ja-si module. The bulk of the modules degraded compared to modules not biases at HV. For thin film modules the losses were insignificant. The detail of modules discussed as shown in Table 6 [94].

**Table 6.** Construction and size of PV Modules Tested

**Figure 12.** Factors influencing the dust settlement [96].

## **2.6. Importance of dust**

The above coating shows good adhesion, weather ability and low water vapor transmission rates. These coatings have a good adhesion to EVA after UV or damp heat exposure. The amount of water vapor that diffuses into EVA controls the stability of glass EVA surface. It may that glass/ EVA interface favors condensation reactions and the hydrolysis reactions are difficult to achieve. The exact mechanism is not known, however it is confirmed by research studies that humidity and leakage current play a very predominant role in degradation of

In a study H-V induces leakage current from eight modules, a pair from each module type of C-Si, Pc-Si. (Bulk Si) and tendem junction and multi-junction a-Si were monitored for eight years. It was observed that the leakage currents from C-Si Pc-Si module were thermal‐ ly activated and the activation energy varied with RH ranging from 0.86-1.0ev at high RH to 0.8ev as low RH. The leakage currents for a-si modules were much lower than bulk Si mod‐ ules by a factor of 10 to100 times. After operation of HV tests for 24 hrs a day the loss rates were 0.0% year for pL –s, 0.1% year for c-s, (positive polarity) between 0% as 0.05% year for ja-si module. The bulk of the modules degraded compared to modules not biases at HV. For thin film modules the losses were insignificant. The detail of modules discussed as shown in

**Module type Structure front to back Area (m2) Perimeter (m) Mounls**

C-Si Glass/ C- Si cells/ Tedar 0.60 3.4 All edges frames Pe-Si Glass/ Pc- Si cells/ Tedar 0.52 3.1 All edges frames 2 Ja-Si Glass/ TCO/a- Si /Al/ glass 0.76 3.7 Rear Brackets 3Ja- Si Flouro polymer/TCO/a-Si/ SS 0.45 3.3 All edges frames

PV modules. The important pathways are showing figure 11 [95].

344 Aluminium Alloys - New Trends in Fabrication and Applications

Table 6 [94].

**Table 6.** Construction and size of PV Modules Tested

**Figure 12.** Factors influencing the dust settlement [96].

Dust is a term which is applied to solid particle with less than 500μm. The main sources of dust are; dust laden winds, volcanic eruptions etc. It also includes micro pollens, microfiber, which are scatter with atmosphere. The factors influence the dust settlements are shown in figure 12 [96].

Dust promotes dust. It settles in region of low vapor pressure induced by the high pressure movements on inclined /vertical surface. The PV system is affected by several environmen‐ tal factors as shown in figure 13 [96].

**Figure 13.** Alterable and unalterable factors determining maximum PV system yield [96].

Amongst all the environmental factors; removal of dust is the most complex factors in PV module. As reported in the literature degradation of 26-40% in the efficiency of thermal pan‐ els are photovoltaic cell was reported for installation in Saudi Arabia which is prevalent with dessert wind [97].

lar wax crystals and nano hairs with nano pores. The two layered hierarchical surface is cov‐ ered by low energy compounds with very low surface energy like PDMS, fluorocarbons and other low energy compounds. Such a two level surface can be created by chemical etching or laser etching to make it a rough surface where the average grain size is in nano region. Sandblasting and short penning or cavitation shotless penning can also be used to make a two level surface. Work on stainless steel has shown the effectiveness of this process. Nano‐ structured films of TiO2 were produced by mixing tetra-n-butyltitanate,ethylacetoacetate

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347

**Figure 15.** Comparison of wetting behavior on symmetric and asymmetric nanostructured surfaces. a, Axially symmetric liquid spreading of a 1μl droplet of deionized water with 0.002% by volume of surfactants (Triton X-100) deposited on typical vertical nanopillars with diameters of 500 nm, spacings of 3.5 μm and heights of 10 μm(inset).b, Unidirectional liq‐

show the characteristics of a spreading droplet at one instant in time. The scale bars in the insets are 10 μm [102].

deflection angle(inset). The images

uid spreading of a droplet on the same dimension nanostructures as a, but with a 120

and ethanol by sol gel technique [100].

The impact of the dust on the reflection of glass in shown figure. Despite few developments in surface technology such as lotus surfaces of work in program with NASA, cleaning by wet method is still predominant.

Future exploration on moon would require mitigating the difficulties posed by Lunor rego‐ lith includes dust. NASA is tasked with the development of mitigation strategies of lunar dust. What has been achieved so far is the development of an Electrodynamics dust shield to minimize dust accumulation, a technique which also could be used to remove dust from PVC modules. The dust removal is achieved by applying a multiphase travelling electric field to the electrode that are embedded in the surface to lift and transport charged and un‐ charged particles off the surface. Following is a brief description of the electrodynamics dust shield technology being developed by NASA. A schematic of three phase Electrodynamics dust shield is shown in figure 14 [98].

**Figure 14.** Schematic diagram of a three-phase Electrodynamic Dust Shield [98].

It consists of a series of a parallel electrodes connected to a multiphase AC source that gen‐ erates a propagating electrodynamics wave. The wave transports the dust particle to a speci‐ fied location. An electric field is generated by the signal output. The strength of electric field varies proportional to the potential difference between electrodes which is controlled by phase shift. The uniform field carries the charged particle [99].

NASA developed transparent 20cm diameter EDS Indium tin oxide (ITO) electrodes on a polyethylene (PET) film. For testing three electrodes of copper 20cm X 25cm for EDS were constructed and two of them were coated with a lotus film. A lotus coating is a two layer system containing microfills (protrusions) ~2.0 mm, and micro valleys containing epicuticu‐ lar wax crystals and nano hairs with nano pores. The two layered hierarchical surface is cov‐ ered by low energy compounds with very low surface energy like PDMS, fluorocarbons and other low energy compounds. Such a two level surface can be created by chemical etching or laser etching to make it a rough surface where the average grain size is in nano region. Sandblasting and short penning or cavitation shotless penning can also be used to make a two level surface. Work on stainless steel has shown the effectiveness of this process. Nano‐ structured films of TiO2 were produced by mixing tetra-n-butyltitanate,ethylacetoacetate and ethanol by sol gel technique [100].

Amongst all the environmental factors; removal of dust is the most complex factors in PV module. As reported in the literature degradation of 26-40% in the efficiency of thermal pan‐ els are photovoltaic cell was reported for installation in Saudi Arabia which is prevalent

The impact of the dust on the reflection of glass in shown figure. Despite few developments in surface technology such as lotus surfaces of work in program with NASA, cleaning by

Future exploration on moon would require mitigating the difficulties posed by Lunor rego‐ lith includes dust. NASA is tasked with the development of mitigation strategies of lunar dust. What has been achieved so far is the development of an Electrodynamics dust shield to minimize dust accumulation, a technique which also could be used to remove dust from PVC modules. The dust removal is achieved by applying a multiphase travelling electric field to the electrode that are embedded in the surface to lift and transport charged and un‐ charged particles off the surface. Following is a brief description of the electrodynamics dust shield technology being developed by NASA. A schematic of three phase Electrodynamics

with dessert wind [97].

wet method is still predominant.

346 Aluminium Alloys - New Trends in Fabrication and Applications

dust shield is shown in figure 14 [98].

**Figure 14.** Schematic diagram of a three-phase Electrodynamic Dust Shield [98].

phase shift. The uniform field carries the charged particle [99].

It consists of a series of a parallel electrodes connected to a multiphase AC source that gen‐ erates a propagating electrodynamics wave. The wave transports the dust particle to a speci‐ fied location. An electric field is generated by the signal output. The strength of electric field varies proportional to the potential difference between electrodes which is controlled by

NASA developed transparent 20cm diameter EDS Indium tin oxide (ITO) electrodes on a polyethylene (PET) film. For testing three electrodes of copper 20cm X 25cm for EDS were constructed and two of them were coated with a lotus film.  Comparison of wetting behavior on symmetric and asymmetric nanostructured surfaces. a, Axially symmetric liquid spreading of a 1μl droplet of deionized water with 0.002% by volume of surfactants (Triton X-100) deposited on typical vertical nanopillars with diameters of 500 nm, spacings of 3.5 μm and heights of 10 μm(inset).b, Unidirectional liq‐ uid spreading of a droplet on the same dimension nanostructures as a, but with a 120 deflection angle(inset). The images show the characteristics of a spreading droplet at one instant in time. The scale bars in the insets are 10 μm [102].

The secret lies in preparing a tailored morphology of the surface. The surface can be tex‐ tured for hydrophobicity (water repelling). The surface exhibit micro convexity with clusters of nanoparticles (99,100). Such surface can trap a large amount of air which has the ability to induce large wet contact angles for hydrophobicity (1700 ).Water drops on such surfaces be‐ come detached, rolls down and carries the dust with them. However in arid regions, there is hardly any rainfall for this phenomena to occur. Super hydrophobic surfaces can be pre‐ pared on metals, glasses and plastics. Similarly a hydrophobic surface can be prepared by depositing films of TiO2 by hydrolysis of titanium aloxides and hydrolysis of TEOT (Triethy‐ lorthotitanate). These films are hydrophilic (water repelling) and also remove contaminants and microbes by the photocatalytic reaction induced by TiO2 particles. Hydrolysis and con‐ densation of titanium aloxide yield Ti-O based network.

ponent of the field and the travelling wave component as mentioned earlier carries the dust to the screen. Single phase excitation lifts the particles. This process becomes more effective

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349

Another force to be considered is dielectrophoretic force. It is experienced by charged or un‐ charged particles in any AC or DC field (E). Because the particles +q and – q are charged and separated by a distance, a dipole moment (qd) is formed. Because of induced dipole mo‐ ment these particles experience dielectrophoretic force. The applied voltage creates a gradi‐ ent in the electric field. The divergence of electric field applies a dielectrophoretic force Fd and a torque T. This force causes the movement of neutral particles on the surface and indu‐ ces electrostatic charging by triboelectrification. This acquired charge would induce to the columbic force of repulsion to lift the particles. In summary, columbic and dielectrophoretic forces move the dust particles to the surface and hence the particles acquire charge. These

This mechanism applies also to conducting particles deposited on the shield. The charge q is

The energy requires for dust removal is only a small fracture of the energy output of the

The electrode grid uses indium tin oxide or carbon nanotubes. Figure 11 shows transparent EDS coatings in glass.The role of aluminium has become very predominant in solar power system. The solar power system has been divided in four distinct groups, parabolic trough,

By applying a three phase voltage 90% of the dust is removed in about two minutes.

. Particle is the vicinity of electrodes acquire electrostatic charge and they

is > force of adhesion (FAdhe‐

when a three phase voltage is applied.

**Figure 16.** Hybrid coating for Photovoltaic solar arrays [103]

charge particles are repelled by electrostatic forces.

are repelled when the force of repulsion FRepulsion =9 E0= E0 r2

proportional to E2

modulesc [104].

sion).The particle would be lifted.

The above surface obtained is hydrophilic. It is also possible to control the direction of flow of water (uni-directional) on asymmetric nanostructured surface by allowing the liquid to flow in one direction and pin on other direction which can be very helpful for various geo‐ metries of photovoltaic modules [101]. Figure 15 shows a comparison of wetting behavior on symmetric and asymmetric nanostructure surface [102].

The lotus coatings being worked out by NASA is developed on the principle described above.

The lotus surface developed is expected to mitigate dust without use of water as in the case of hydrophobic surface. The lotus coating two level would shed particles utilizing anti con‐ tamination and self cleaning properties which would minimize dust accumulation. Such coatings based on the structure of lotus flower such as hydrophobic coatings on glass and plastics would have the capability to repell dust. NASA is developing both hydrophobic and hydrophilic coatings which are next generation coatings to minimize dust on solar cells and thermal radiation. Self cleaning and anti-contamination systems being developed have also the capability to kill bacteria, chemical agents, pathogens and environmental pollutants. In future the super hydrophobic coatings would play a leading role not only in lunar envi‐ ronment but also in solar cells and most importantly in space exploration. The hybrid coat‐ ing for photovoltaic solar arrays are shown in figure 16 [103].

In order to understand the working of EDS, it is important to understand the forces which are responsible for lifting the sands.Two types of forces are applied by the electrodynamic field; a: Electrostatic force and b): di electrophorelectric force.

Most airborne dust particles acquire an electrostatic charge during their detachment process. Each sand particle is subjected to a sinusoidal excitation voltage generated by the electric field. A charge particle experienced two forces of repulsion, one tangential and other normal to the contact angle. The lift force for the particle is provided by centrifugal force which is induced by the curvilinear motion of the particle. Another particle charged with –q will be subjected to repulsive force and it would levitate of the lifting force is larger than the adhe‐ sion force due to the cumulative effects of lifshitz –vander walls forces, electrostatic forces and capillary forces. There is hardly any capillary force in the desert region. On energizing of three phase voltage,the charged particles are lifted from the surface by the vertical com‐ ponent of the field and the travelling wave component as mentioned earlier carries the dust to the screen. Single phase excitation lifts the particles. This process becomes more effective when a three phase voltage is applied.

**Figure 16.** Hybrid coating for Photovoltaic solar arrays [103]

The secret lies in preparing a tailored morphology of the surface. The surface can be tex‐ tured for hydrophobicity (water repelling). The surface exhibit micro convexity with clusters of nanoparticles (99,100). Such surface can trap a large amount of air which has the ability to

come detached, rolls down and carries the dust with them. However in arid regions, there is hardly any rainfall for this phenomena to occur. Super hydrophobic surfaces can be pre‐ pared on metals, glasses and plastics. Similarly a hydrophobic surface can be prepared by depositing films of TiO2 by hydrolysis of titanium aloxides and hydrolysis of TEOT (Triethy‐ lorthotitanate). These films are hydrophilic (water repelling) and also remove contaminants and microbes by the photocatalytic reaction induced by TiO2 particles. Hydrolysis and con‐

The above surface obtained is hydrophilic. It is also possible to control the direction of flow of water (uni-directional) on asymmetric nanostructured surface by allowing the liquid to flow in one direction and pin on other direction which can be very helpful for various geo‐ metries of photovoltaic modules [101]. Figure 15 shows a comparison of wetting behavior on

The lotus coatings being worked out by NASA is developed on the principle described

The lotus surface developed is expected to mitigate dust without use of water as in the case of hydrophobic surface. The lotus coating two level would shed particles utilizing anti con‐ tamination and self cleaning properties which would minimize dust accumulation. Such coatings based on the structure of lotus flower such as hydrophobic coatings on glass and plastics would have the capability to repell dust. NASA is developing both hydrophobic and hydrophilic coatings which are next generation coatings to minimize dust on solar cells and thermal radiation. Self cleaning and anti-contamination systems being developed have also the capability to kill bacteria, chemical agents, pathogens and environmental pollutants. In future the super hydrophobic coatings would play a leading role not only in lunar envi‐ ronment but also in solar cells and most importantly in space exploration. The hybrid coat‐

In order to understand the working of EDS, it is important to understand the forces which are responsible for lifting the sands.Two types of forces are applied by the electrodynamic

Most airborne dust particles acquire an electrostatic charge during their detachment process. Each sand particle is subjected to a sinusoidal excitation voltage generated by the electric field. A charge particle experienced two forces of repulsion, one tangential and other normal to the contact angle. The lift force for the particle is provided by centrifugal force which is induced by the curvilinear motion of the particle. Another particle charged with –q will be subjected to repulsive force and it would levitate of the lifting force is larger than the adhe‐ sion force due to the cumulative effects of lifshitz –vander walls forces, electrostatic forces and capillary forces. There is hardly any capillary force in the desert region. On energizing of three phase voltage,the charged particles are lifted from the surface by the vertical com‐

).Water drops on such surfaces be‐

induce large wet contact angles for hydrophobicity (1700

348 Aluminium Alloys - New Trends in Fabrication and Applications

densation of titanium aloxide yield Ti-O based network.

symmetric and asymmetric nanostructure surface [102].

ing for photovoltaic solar arrays are shown in figure 16 [103].

field; a: Electrostatic force and b): di electrophorelectric force.

above.

Another force to be considered is dielectrophoretic force. It is experienced by charged or un‐ charged particles in any AC or DC field (E). Because the particles +q and – q are charged and separated by a distance, a dipole moment (qd) is formed. Because of induced dipole mo‐ ment these particles experience dielectrophoretic force. The applied voltage creates a gradi‐ ent in the electric field. The divergence of electric field applies a dielectrophoretic force Fd and a torque T. This force causes the movement of neutral particles on the surface and indu‐ ces electrostatic charging by triboelectrification. This acquired charge would induce to the columbic force of repulsion to lift the particles. In summary, columbic and dielectrophoretic forces move the dust particles to the surface and hence the particles acquire charge. These charge particles are repelled by electrostatic forces.

This mechanism applies also to conducting particles deposited on the shield. The charge q is proportional to E2 . Particle is the vicinity of electrodes acquire electrostatic charge and they are repelled when the force of repulsion FRepulsion =9 E0= E0 r2 is > force of adhesion (FAdhe‐ sion).The particle would be lifted.

By applying a three phase voltage 90% of the dust is removed in about two minutes.

The energy requires for dust removal is only a small fracture of the energy output of the modulesc [104].

The electrode grid uses indium tin oxide or carbon nanotubes. Figure 11 shows transparent EDS coatings in glass.The role of aluminium has become very predominant in solar power system. The solar power system has been divided in four distinct groups, parabolic trough, parabolic dish, linear fersenel and solar tower. Aluminium is one of the most important ma‐ terial utilized in solar absorbing due to the capability of its anodic layer formed on its sur‐ face by the process of anodization. Eutectic binary aluminiumm alloys such as Al-0 wt% Ni, Al-33 wt% Cu and Al-7.5wt% Ca have been successfully used as absorber(low reflection and high absorption).The mechanical and thermal ability of aluminium alloys and regeneration of surface is etching enhances their properties in solar power system.

maximum resistance to HV operation. In HV operation, all modules degrade at rates higher than the modules not biased on HV. Films on PET showed promising properties as a back sheet replacement for glass. These coatings exhibit excellent moisture resistance properties and a good cohesion after exposure to damp heat. The corrosion effect can be minimized by increasing adhesion of transparent oxide by using Zinc oxide in place of Tin oxide and by

Aluminium Alloys in Solar Power − Benefits and Limitations

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351

Dust is still haunting the scientists and engineers working on solar and space equipment. It is of vital importance to solar panels and equipment used in space exploration. A substantial amount of research has been done on electrodynamics system to remove dust. This is cou‐ ples with creating a lotus surface (two level) hierarchical surface (nano/micro hybrid) to cre‐ ate self cleaning properties for removal of dust by mimicking the surface of a lotus flower. Various paints containing self cleaning agents have also been designed to remove dust. The wet chemistry route creating a superhydrophobic surface is an outstanding achievement but it cannot be applied in dessert conditions. Intensive work is undertaken by NASA to create dust shields. It appear that new techniques would be developed to mitigate the degradation

I am highly indebted to Ms. Zahra Khan (Comsats) and Ms. Tayyaba Abid (Comsats) for their dedicated help in preparing the manuscript of the chapter for the book. The above col‐ leagues have put in a very dedicated work in all technical aspects related to the formatting

4 Department of Materials Engineering, University of British Columbia, Vancuver, B.C, Can‐

5 Department of Electrical Engineering, Lahore College For Women University, Lahore,

, Zaki Ahmad1,2 and Intesar Ahmad5

using low acetate and high resistivity glass.

**Acknowledgements**

**Author details**

ada

Pakistan

processing and editing of this script.

Amir Farzaneh3\*, Maysam Mohammadi4

1 KFUPM. Dhahran, Saudi Arabia

\*Address all correspondence to<EMAIL_ADDRESS>
2 Dept Of Chemical Engineering, Comsats Lahore, Pakistan

3 Dept of Materials Engineering, University of Tabriz, Tabriz, Iran

of PV modules and the use of aluminum would continue to rise.

Aluminium extrusion provides a clear economic advantage in the product of solar applica‐ tion. White steel costs less than aluminum on a dollar per pound basis, the lower weight of aluminium (1/3rd of steel) allow far more material to be used at a lower cost.

Because of its recyclability,light weight, high strength and high corrosion resistance,it has become a preferred material. By using aluminium Alcoa is saving on costs of solar pond and transportation.

Hydro in Germany is making mirrors for concentrated solar power as well as absorber sheets for solar thermal application. This company launches the first tailored Hybridlife so‐ lar aluminium alloy for concentrated solar power and launched high select coatings for solar thermal systems. Hydro serves its customer in solar thermal concentrated solar power and photovoltaic for all area of solar energy product.

Ali Baba has manufactured 1 KW, 2 KW, 3 KW and 10 KW solar power systems,aluminium based with a life span of 25 years.(AliBaba.com). Light technology is a leading and provides standard aluminium profile for mounting systems for solar energy.

Pacific power management (PPM) has announced the installation of a 800 KW power plant for Sierra Aluminium Company. It contains 4,480 Mistzubish Electric,180 watts modules and 2 satcons 5oo Kw invertors. It generates 1.4m Kwh per year.

It would reduce Sierra carbon footprint by 48% and supply power to 28,000 homes over a 25 year period.

The use of solar mirrors could reduce the cost by 20%. For a 50 megawatt power plant, a saving of 20 million euros could be made.

## **2.7. Conclusion**

Aluminum is playing a predominant role in solar power system because of its technical ca‐ pability,ease of fabrication and ease of transport use, recyclability and resistant to corrosion. The promising future of aluminium in solar power is reflected by the projections on market growth from 210 mm2 to 11 bmm2 . By 2050, the amount could reach 39 mtons from the exist‐ ing 17 mtons. The major attributes are large energy area for collection, solar directed instal‐ lation and dynamic development. However there are several technical problems associated with solar power such as the ingress of moisture causing corrosion and leakage of current causing deterioration of modules. The water vapours ingresses through the edges and in‐ creases the conductivity of the front glass surface and also the magnitude of leaking current. In the four types of modules a). C-Si, b). PC-Si, c). 2J a-Si (Glass/TCO/a-Si/Al/Glass) and 3 Ja-Si (Fluropolymer/TCO/a-Si/stainless steel), the two modules containing a-Si showed the maximum resistance to HV operation. In HV operation, all modules degrade at rates higher than the modules not biased on HV. Films on PET showed promising properties as a back sheet replacement for glass. These coatings exhibit excellent moisture resistance properties and a good cohesion after exposure to damp heat. The corrosion effect can be minimized by increasing adhesion of transparent oxide by using Zinc oxide in place of Tin oxide and by using low acetate and high resistivity glass.

Dust is still haunting the scientists and engineers working on solar and space equipment. It is of vital importance to solar panels and equipment used in space exploration. A substantial amount of research has been done on electrodynamics system to remove dust. This is cou‐ ples with creating a lotus surface (two level) hierarchical surface (nano/micro hybrid) to cre‐ ate self cleaning properties for removal of dust by mimicking the surface of a lotus flower. Various paints containing self cleaning agents have also been designed to remove dust. The wet chemistry route creating a superhydrophobic surface is an outstanding achievement but it cannot be applied in dessert conditions. Intensive work is undertaken by NASA to create dust shields. It appear that new techniques would be developed to mitigate the degradation of PV modules and the use of aluminum would continue to rise.

## **Acknowledgements**

parabolic dish, linear fersenel and solar tower. Aluminium is one of the most important ma‐ terial utilized in solar absorbing due to the capability of its anodic layer formed on its sur‐ face by the process of anodization. Eutectic binary aluminiumm alloys such as Al-0 wt% Ni, Al-33 wt% Cu and Al-7.5wt% Ca have been successfully used as absorber(low reflection and high absorption).The mechanical and thermal ability of aluminium alloys and regeneration

Aluminium extrusion provides a clear economic advantage in the product of solar applica‐ tion. White steel costs less than aluminum on a dollar per pound basis, the lower weight of

Because of its recyclability,light weight, high strength and high corrosion resistance,it has become a preferred material. By using aluminium Alcoa is saving on costs of solar pond and

Hydro in Germany is making mirrors for concentrated solar power as well as absorber sheets for solar thermal application. This company launches the first tailored Hybridlife so‐ lar aluminium alloy for concentrated solar power and launched high select coatings for solar thermal systems. Hydro serves its customer in solar thermal concentrated solar power and

Ali Baba has manufactured 1 KW, 2 KW, 3 KW and 10 KW solar power systems,aluminium based with a life span of 25 years.(AliBaba.com). Light technology is a leading and provides

Pacific power management (PPM) has announced the installation of a 800 KW power plant for Sierra Aluminium Company. It contains 4,480 Mistzubish Electric,180 watts modules

It would reduce Sierra carbon footprint by 48% and supply power to 28,000 homes over a 25

The use of solar mirrors could reduce the cost by 20%. For a 50 megawatt power plant, a

Aluminum is playing a predominant role in solar power system because of its technical ca‐ pability,ease of fabrication and ease of transport use, recyclability and resistant to corrosion. The promising future of aluminium in solar power is reflected by the projections on market

ing 17 mtons. The major attributes are large energy area for collection, solar directed instal‐ lation and dynamic development. However there are several technical problems associated with solar power such as the ingress of moisture causing corrosion and leakage of current causing deterioration of modules. The water vapours ingresses through the edges and in‐ creases the conductivity of the front glass surface and also the magnitude of leaking current. In the four types of modules a). C-Si, b). PC-Si, c). 2J a-Si (Glass/TCO/a-Si/Al/Glass) and 3 Ja-Si (Fluropolymer/TCO/a-Si/stainless steel), the two modules containing a-Si showed the

. By 2050, the amount could reach 39 mtons from the exist‐

of surface is etching enhances their properties in solar power system.

standard aluminium profile for mounting systems for solar energy.

and 2 satcons 5oo Kw invertors. It generates 1.4m Kwh per year.

to 11 bmm2

photovoltaic for all area of solar energy product.

350 Aluminium Alloys - New Trends in Fabrication and Applications

saving of 20 million euros could be made.

transportation.

year period.

**2.7. Conclusion**

growth from 210 mm2

aluminium (1/3rd of steel) allow far more material to be used at a lower cost.

I am highly indebted to Ms. Zahra Khan (Comsats) and Ms. Tayyaba Abid (Comsats) for their dedicated help in preparing the manuscript of the chapter for the book. The above col‐ leagues have put in a very dedicated work in all technical aspects related to the formatting processing and editing of this script.

## **Author details**

Amir Farzaneh3\*, Maysam Mohammadi4 , Zaki Ahmad1,2 and Intesar Ahmad5

\*Address all correspondence to<EMAIL_ADDRESS>
1 KFUPM. Dhahran, Saudi Arabia

2 Dept Of Chemical Engineering, Comsats Lahore, Pakistan

3 Dept of Materials Engineering, University of Tabriz, Tabriz, Iran

4 Department of Materials Engineering, University of British Columbia, Vancuver, B.C, Can‐ ada

5 Department of Electrical Engineering, Lahore College For Women University, Lahore, Pakistan

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http://dx.doi.org/10.5772/54721

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## *Edited by Zaki Ahmad*

Aluminium alloys have undergone a dramatic transformation in areas of extrusion, machining, welding, heat treatment, structural changes, created by ultra fine particles and enhanced corrosion resistance. Hence, these alloys have made rapid gains in European automotive and space industry. These developments have been described by experts in the book with new data and attractive graphics. The effect of processing parameters, including welding and deep rolling on their performance have been highlighted to alleviate the concerns of manufacturers and designers for new applications. The novel role of aluminum alloys in photovoltaic cells and concentrated solar power has been comprehensively described in the context of corrosion and the aggressive environment to which they may be exposed. The book is designed to serve as a guide for future innovations and new developments in aluminium alloys.

Aluminium Alloys - New Trends in Fabrication and Applications

Aluminium Alloys

New Trends in Fabrication and Applications

*Edited by Zaki Ahmad*

Photo by Rost-9D / iStock


**6. Conclusions and perspectives**

The study of baculoviruses is a traditional field in virology. In particular, genetic engineering of AcMNPV emerged in the 1980s, and several systems for various purposes have been developed. However, although genetic engineering of baculoviruses seems to be a thoroughly explored area, much work is still required to fully exploit the advantages of the system.

**Author details**

Argentina

**References**

Santiago Haase, Leticia Ferrelli, Matías Luis Pidre and Víctor Romanowski

Instituto de Biotecnología y Biología Molecular, Universidad Nacional de la Plata, Conicet,

Genetic Engineering of Baculoviruses http://dx.doi.org/10.5772/56976 101

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(1963), Academic Press, New York.

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200.

Vectors and cells with many advantageous characteristics have been developed; yet, it would be tantalizing to assemble all these features in a single system. As mentioned before, the addition of an IRES to the transfer vector to couple the recombinant ORF to an essential BV ORF enhanced the genetic stability of the recombinant virus providing sustained recombinant protein expression. However, this feature is still not commercially available and is not compatible with many commercial systems. Other alternatives that have been explored and may be assembled in new generation systems include: selection by rescue of a lethal gene deletion, deletion of baculovirus chitinase and cathepsin, expression of chaperones and other folding proteins and expression of mammalian glycosylation pathway proteins.

The use of transgenic cell lines for expression of recombinant proteins is a convenient alter‐ native to baculovirus infection, since the protein is not expressed in an infection context. Selection systems for the generation of transgenic insect cell lines may be optimized. Systems based on site‐specific recombination would increase the rate of transgenic cell generation, thus simplifying clonal cell isolation. Negative selection systems should be explored as well. Additionally, the development of inducible expression systems would be very convenient, since they are convenient for expression of proteins that affect cell physiology.

The improvement of baculovirus bioinsecticides by means of genetic engineering is a chal‐ lenging subject. Genetic stability of recombinant baculovirus is an issue, and it is addressed by strategies such as the addition of an IRES (as mentioned before) and by deleting small regions with high recombination rates. Many genes from various sources are being tested for their ability to increase baculovirus biopesticidal propierties, although small RNA‐mediated silencing will probably emerge as an important alternative to foreign gene expression ap‐ proach. Host range modification is even more challenging. To address this question a system‐ atic study could start by replacing each of the baculovirus genes with related baculovirus homologs in search of functional complementation. Other various approaches may be envisaged. Also, bioinformatics studies in search of genes subjected to positive pressure are valuable to provide candidates of host‐specific interaction genes. These bioinformatics studies should be updated with the recently sequenced baculovirus genomes. The use of baculovirus to transduce mammalian cell lines and mammalian organism bring baculovirus in the gene therapy and vaccine fields. One of the most challenging objectives in this area is the program‐ ming of viral particles to target specific tissues or cell types. In this direction, the replacement of the baculovirus fusion protein by other fusion proteins have shown to modify baculovirus BV tropism, and the development of targeted baculovirus is crucial for exploiting their potential as gene therapy vectors.

From this overview of the field, it is clear that there is room for many strategies and approaches to improve the various applications of genetically engineered baculoviruses.