Solar Textiles || Solar Cells || Manufacturing || Applications

Vaibhav Raut

Department of Textile Technology

Shri Vaishnav Vidhyapeeth Vishwavidhayalaya Indore, Madhya Pradesh, India

Abstract

Solar fabric is fabric made by the flexible, fiber-optic solar cell that can be woven into clothes.These fibers are thinner than human hair, flexible, and yet they produce electricity, just like a normal solar cell.The research team started with optical fibers made from glass — and then, using high-pressure chemical vapor deposition, injected n-, i-, and p-type silicon into the fiber, turning it into a solar cell. Functionally, these silicon-doped fiber-optic threads are very uch identical to conventional solar cells, generating electricity from the photovoltaic effect. Most of the solar cell present in  the market is crafted out of 2D, planar amorphous silicon on a rigid/brittle glass substrate, though, these fiber-optic solar cells have a 3D cross-section and retain the glass fiber’s intrinsic flexibility. The major advantage is their three-dimensional cross-section, they can absorb sunlight from any direction. Benefit of solar fabric are it Provides lighting and electrical generation, Light production can be varied, Low manufacturing cost, Low operating cost, Lightweight and flexible .Commercial Applications of solar fabric are Solar lighting, Solar powered devices, Energy conversion and utilization, Commercial buildings and Space missions. Information about solar cell technology its application in textiles is elaborated in the article.

Introduction:

Textile fabrics nowadays possess a multitude of applications. Along with the major use in apparels,they have wide uses in technical applications ,ranging from conventional bulk bags to sophisticated medical implants. Moreover, the miniaturization of electronic devices over the past twenty years or so has expanded textile applications still further. There is extensive interest in the incorporation of sensors into wearable fabrics: for example, for medical, military, sports and leisure applications. In this paper, we explore the innovative use of textiles as supports for electricity-generating photovoltaic (PV) solar cells, contrasting the different approaches that seek to use the performance of a fabric without compromising the operation of the solar cells. The simplest approach, of bonding solar cells to a fabric, is less effective in retaining the textile properties than it is in maintaining the solar cell performance. Solar PV is one of the alternative sustainable energy sources that make up increasing amounts of electrical demand in many countries. In 2015, PV provided 1.2% of global electricity demand. However, the most compelling direct source of energy, and one that will provide an “endless” supply, is the sun. The sun provides the whole Earth with ample of  energy in one hour than the world’s population uses in one year. To overcome these drawbacks, attention has increasingly been turned to the construction of lighter, flexible cells, which can withstand harsh environments, maintain durability and involve lower materials use and reduced cost in their construction. An extensive commercial range of photovoltaic cells now exists that has been applied to thin plastic or metal films. These films are much lighter and generally cost less to produce. The role of textile fabrics as substrates for solar cells is increasing and demanding sector.

Why Solar cells in Textiles?

• Manufacturing of flexible solar cells is possible.
• Due to the efficient quality of solar cell which can be easily combined with textiles.
• EAT(Electricity any time)
• Infinite scope of application.
• Inexhaustible source of energy.
• Cost free resource.
• Eco friendly.
• Purest form of power.
• Replacement option to the fossil fuels in near future.
• Available on every part of earth

Photovoltaic Cells and Fabrics:

In order to understand the restrictions of adding solar cells to a fabric, it is necessary to appreciate how solar cells convert solar radiation into electrical energy by a planar architecture of semiconducting and conducting materials. Variations of this basic device have been developed to enhance PV performance whilst reducing production costs, and to enable thinner semiconducting layers to perform the same function as more conventional crystalline wafers. The section describes these solar cell types and is followed by a section on the options for textile constructions. There is then an account of how textiles may be made electrically conducting so as to form the base layer of a solar cell.

Types of Solar Cells:

• Inorganic photovoltaic semicoductors
• Organic photovoltaic semiconductors

Manufacturing of inorganic solar cell fibers.

Inorganic photovoltaic semiconductors is the one adaptation of their strategy was the incorporation directly onto a fabric of a polymer PV on a polyester substrate. Another adaptation was notably more complex. It initially comprised the lamination of a thin layer of polyethylene onto a fabric and then, after plasma treatments of the layer, the application of a PEDOT electrode.

PV cell fabrication uses a mix of techniques known to the semiconductor and textile industries. First, the fabric is cleaned and then lightly calendared to render the surface continuous without melting the whole thickness. The lower PV contact is formed of two layers: A liquid coated conducting polymer, PEDOT: PSS, and a vacuum evaporated metal, aluminum. The polymer coating is insufficiently conducting to form an effective PV electrode, but its flexibility enables it to bridge any micro cracks that develop in the more brittle aluminum as the device is twisted or stretched. The process is followed by the photoactive, triple amorphous silicon layers (N-type, undoped, and P-type) laid down by low pressure, RF PECVD from silane with phosphine or diborane, at 200 ^◦C or slightly less. The upper contact is a conventional sputtered TCO that also acts as a first encapsulating coat

Technological specifications

• The starting point has to be consideration of the application and its power demand: is it possible to supply this by PV alone, or will batteries also be required? Integrating thin batteries into a PV textile has been proposed, with some loss of fabric handle and drape, and is possible for low power demands, such as for sensors or portable electronic items.
• Further attention should be given to the choice of materials (both environmental and economic issues) and to the thermal limitations of the fabric (process energy cost and processing stability).
• In addition, the application will have its own requirements for operating conditions and perhaps for washing or cleaning if the fabric is to form part of clothing or furnishings.
• It is evident that the surface character of the fabric will necessarily be altered by the incorporation of PV cells, and indeed the deposited PV cells are liable to be highly susceptible to external conditions. For this reason, the PV fabric surface has to be suitably protected, depending on the application for which it is destined.
• For an outside use such as tents, the robust resin coating that is used on tent fabrics will also have to protect the PV cells on it.
• For an indoor application, such as curtains, where conditions are expected to be more clement, the protective layer can be thin, so that drape, in particular, is not compromised.
• Though the surface character will be altered, the factors comprising the bulk properties of the fabric should be affected as little as possible. These factors include fiber composition, yarn construction, fabric construction, and, particularly in the case of nonwovens, porous nature. It is clear too that the construction and properties of the products made from PV fabrics should also be unaffected.
• There will be further specifications, for some specific applications. An obvious example is that clothing should retain its comfort and aesthetic appeal.
• It should also be remembered that the performance of conventional PV cells and panels is specified at “standard operating conditions” (STD): 1 kW·m⁻², AM1.5 spectrum, 25 ^◦C. For novel applications, it may have a much lower light intensity and from an artificial source instead of the sun.
• There might be extensive and changeable shadowing for flexible PV whose shape is continuously changing with movement.

Organic photovoltaic semiconductors

• Rigid substrates such as glass (for conventional).
• Flexible substance like polypropylene fiber (for modern)
• Transparent conductive bottom electrode eg. Indium Tim oxide (ITO)
• Poly (PEDOT:PSS)
• An organic protective layer.
• Metal electrode.

Manufacturing of inorganic solar cell fibers.

• In all of these types of cells, the basic principle is the same: Generation of electrical energy from radiant energy by two dissimilar materials in electrical contact, without chemical reaction, mechanical motion, or requiring thermal energy.
• Illumination falling on a PN junction cell produces pairs of positive and negative charges which are then separated by the in-built electrical field that arises at the junction between P-type and N-type semiconductors.
• This junction field is a consequence of adding minute amounts of selected impurities into each side of the junction, which then causes a potential energy barrier to be set up across the junction: negative electrons will tend to move from P-type to N-type, and positive “holes” will tend to move in the other direction.
• The combination of this flow of charges (an electrical current) and the potential barrier (“voltage”) provides electrical energy that may be fed into a connected load.

Ongoing developments:

Silicon p-i-n fibers (inorganic photo voltaic)

• Fabricated by HPCVD (High pressure chemical vapors deposition) i.e. fabrication of
• semiconductor via drawing.
• We can exploit meters long p-i-n junction it will be necessary to develop long, parallel in-fiber wire electrodes configured to reduce the space
• By this we can also use inorganic materials to build solar textile e.g. silicon

Dye synthesized solar cells (DSC):

• Mostly the substrates which are used are Silica and Plastic optical fibers 
• Fiber converts light modes propagating in the modified cladding into electrical signal.
• The light here is absorbed by the dye.
• Manufacturing process make nanostructure dye-sensitized solar cell (DSC) a potential alternative to the traditional silicon and thin film of PV devices.

APPLICATIONS:

Apparels: 

• Embedded solar cell Shirts ,
• Embedded solar cell jackets
• Embedded solar cell trousers
• Fabrics could be woven using organic solar cell fibers.

General application

• Soldier uniforms and marine fabrics.
• Tents for campers and trekkers.
• Replacement for solar panels as they are huge and heavy.

Reference:

• Solar cell textile by. Raj Kumar. R.Shinkar. 
• Solar cells –new aspects and solutions by prof. Leonid.
• Flexible thin –solar cell technology by market publishers.
• Fust flexible, fiber optic solar cell that can be woven into clothes by Sebastian Anthony.
• Technology opportunity: optical fiber for solar cell by tael kovo (NASA).