Also Called Photovoltaic Cell Or Photoelectric Cell

Published Date: 02 Nov 2017

Chapter 3

Is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect , Solar cell used to capture energy from sunlight also used to make solar modules And to generate useful power , There is more about the different types of solar cell ,The normal output voltage of a solar panel is usually 12 Volts, and they may be used singly or wired together into an array. The number and size required is determined by the available light and the amount of energy required. When solar cells absorb sunlight, free electrons and holes are created at positive/negative junctions. If the positive and negative junctions of solar cell are connected to DC electrical equipment, current is delivered to operate the electrical equipment[19].

Diode

A diode uses a semiconductor material, usually silicon, with two terminals attached. Diodes use their internal field to allow electric current to flow one way in a circuit and prevent it from flowing back.

Solar panels are comprised of PV cells in series. Each cell is an electricity generating unit. Remember that, just as in batteries, when cells are connected in series, the voltage is compounded. So a solar panel with 36 cells (each generating approximately .5 volts DC) in series is producing approximately 18 VDC for charging 12V batteries. If the battery bank is greater than 12V, several panels are wired in series to increase the panel voltage to match that of the battery. For instance, two panels in series would produce approximately 36 VDC for charging a 24V battery. If additional charging amperage is desired, two or more panel series strings are paralleled to increase the amperage output.

This example shows a typical series/parallel panel array configuration:

Each PV cell (this also applies to the entire panel) is either a power producer or a power consumer, depending on whether it is exposed to sunlight or not. Diodes used in a blocking capacity are installed between parallel panel strings and/or between the entire array and the battery. They prevent current from flowing back into shaded paralleled series strings or arrays that are acting as a power consumer, discharging all of the power produced by the other series strings and/or the power stored in the battery at night when the array is darkened.

Diodes utilized in a bypass capacity are installed within the series string. There is a certain amount of resistance inherent in the forward direction of the diode. The diode's internal resistance is greater than that of a PV cell (or panel) when exposed to sunlight. The current follows the path of least resistance and flows through each consecutive cell (or panel) in the string. When a cell (or panel) in the series string is shaded (and potentially consuming power) the resistance in that cell (or panel) increases tremendously, making the bypass diode the path of least resistance. The current follows the path of least resistance, shunting the power through the bypass diode and through an alternate circuit around that PV cell (or panel) to the next producing PV cell or panel in the string. The only voltage loss is that created by eliminating the cell (or panel) that

is inactive.

Types of Diodes

There are two types of diodes in conjunction with PV arrays, plates Baebas diodes and diodes ban. This is not in fact two different but use the same device for two different purposes are that it causes the function block, and to prevent backflow to the bottom of the unit when you install a series of diodes in series with a series of modules;. When you install diodes in parallel with the units, they function as bypass to allow current to pass around the shaded area of the module.

Solar Cell Works

When sunlight hits the surface of solar cells as charge carrier creates electrons and holes. And swept to the positive holes or P layer and electrons to the negative or layer. When the circuit is made, and the free electrons have to pass through the load to re-compile with the positive holes, and can be produced from the cells under the current lighting. The internal field produced by the junction separates some of the positive charges (holes) of the negative charges (electrons)[17].

 Associated with solar cells of individual together to make a module (called a panel or panel solar PV) to increase the current and associated modules in a wide range (called "the solar system" or "PV group '). There is a relationship between the solar panels in a variety of ways depending on current or voltage requirement; solar arrays are connected in a variety of ways:

• If the solar arrays are connected in parallel, the output current will increase. 

• If the solar arrays are connected in series, the output voltage will increase.

Blocking Diodes:

Diodes placed in series with cells or modules can perform another function that of blocking reverses leakage current backwards through the modules. There are two situations where blocking diodes can help prevent the phenomenon.

•Blocking reverse flow of current from the battery through the module at night:

In battery charging systems, the module potential drops to zero at night, and the battery could discharge all night backwards through the module. This would not be harmful to the module, but would result in loss of precious energy from the battery bank. Diodes placed in the circuit between the module and the battery can block any nighttime leakage flow.

•Blocking reverse flow down damaged modules from parallel modules during

the day:

Blocking diodes placed at the head of separate series wired strings in high voltage systems can perform yet another function during daylight conditions. If one string becomes severely shaded, or if there is a short circuit in one of the modules, the blocking diode prevents the other strings from loosing current backwards down the shaded or damaged string. The shaded or damaged string is "isolated" from the others, and more current is sent on to the load. In this configuration, the blocking diodes are sometimes called "isolation diodes".

By –Pass Diodes:

The cells shaded shaded cells forced to pass more current that the new short circuit current. The only way shaded cells can operate at the highest current of the current status is a short circuit to work in the region of the negative voltage that causes the net voltage. When the shaded PV module, and the shaded cells will not be able to produce up now, because the United Nations shadowed once. Since all cells are linked in series, must be the same amount of current flow through each cell. This shading effect also depends on how the shaded units. This is much worse to highlight a single cell from 75% to highlight the three cells of 25% each. The current era this gives a negative voltage negative force produced by the shaded cells. In other words, the shaded cells dissipate energy as heat and cause "hot spots". And the shaded cells with drag down the overall IV curve of the group of cells. The effect of this shading is also dependent on how the module is shaded. It is far worse to shade one cell 75% than to shade three cells 25% each. So if shading cannot be avoided, try to spread the shading over the most number of cells. One way to minimize the effect shading has on a single module in a series string, is to use by pass diodes in the junction box. Bypass diodes allow current to pass around shaded cells and thereby reduce the voltage losses through the module. When a module becomes shaded its bypass diode becomes "forward biased" and begins to conduct current through itself. All the current greater than the shaded cell’s new short circuit current is "bypassed" through the diode, thus reducing drastically the amount of local heating at the shaded area. Diode unit also carries a full shaded or group of cells to a small negative voltage of about -0.7 volts, limiting the decline in the output array, thus limiting the reduction in array output. They are most likely to be of benefit where an MPPT Controller or String Inverter involves panels connected in series to produce voltage well above that items minimum input voltage. Some solar panels are constructed with the cells divided into groups, each group having a built-in by-pass diode. Shading of part of a panel may be caused by a tree branch, debris, or snow[18].

Types of solar cell

Is treated with silicon or "doped" to generate an electric current. Usually consists of silicon solar cells, the same material used for transistors and integrated circuits..

So that is released when light strikes it electrons, and three basic types of solar

cells available.

Mono-crystalline cells are cut from a silicon ingot grown from a single large crystal of silicon whilst polycrystalline cells are cut from an ingot made up of many smaller crystals

The second type is the amorphous or thin-film solar cell,

The third type is Hybrid Silicon PV Module.

There are three major cell types that classified by its manufacturing technology and the semiconductor:

Crystalline Silicon PV Module:

Two types of crystalline silicon (c-Si) are used to produce PV module; single crystalline silicon or known as mono crystalline silicon and multi-crystalline silicon, also called polycrystalline silicon. The polycrystalline silicon PV module has lower conversion efficiency than single crystalline silicon PV module but both of them have high conversion efficiencies that average about 10-12%.

Crystalline solar cells are wired in series to produce solar panels. This is sufficient to charge a 12 Volt battery under most conditions. As each cell produces a voltage of between 0.5 and 0.6 Volts, 36 cells are needed to produce an open-circuit voltage of about 20 Volts.

There difference between mono and poly crystalline:

Both poly-crystalline and mono-crystalline solar panels are made from the same material, silicon. However the difference is that the poly-crystalline material is made up of millions or billions of small silicon crystals while the mono-crystalline material is actual just that, one large singe crystal of silicon.

 Single crystal silicon is more efficient at converting photons to electrons for electricity, the poly-silicon it's much less efficient because electrons are captured or generated less efficiently where the crystals of silicon touch.

Amorphous Silicon PV Module:

Amorphous silicon (A-C) and the PV module or thin-film silicon PV module absorbs light more effectively than crystalline silicon PV module, so make the weight. Suitable for any applications for high efficiency for low cost. Typical efficiency of amorphous silicon PV module around6%.

The technology is often seen in amorphous solar panels, small calculators or garden lamps, and had formed a committee of one piece and the individual cells are not visible, such as other species. They are made by the deposit of a thin layer of silicon on a sheet of insulating material such as steel.

The efficiency of amorphous solar panels is not high, such as those made from individual solar cells; despite this, it has improved in recent years to the point that can be seen as a viable alternative to panels to make crystalline cells tram.

Both great advantage lies in the relatively low cost per watt of generating capacity. And can be offset, however, by the intensity of less powerful, there is a need for more panels to produce energy is the same so more space is required.

Hybrid Silicon PV Module:

A mixture of crystalline silicon and one is surrounded by thin layers of amorphous silicon provides excellent sensitivity to low light levels or indirect light. The Hybrid silicon PV module has the highest level of conversion efficiency about 17%.

The advantage use of Solar Cell

Solar cell or photovoltaic cell produces clean non-polluting source of energy with electricity that is environmentally friendly.

It reduces the range of greenhouse gases such as carbon monoxide, sulfur dioxide, nitrogen, and hydrocarbons ..., etc..

It uses a fuel other than sunlight, and gives those who do not waste, do not burn, and no part to move when they operate.

With the attribute units, and therefore can be any size as required.

It is easy to install and transport.

Applications of solar cell

Home lighting system of internal and external, electrical equipment, and electric door opener, security system, a ventilator, water pump, water filtration and emergency light, etc..

Communication air navigational aids, air warning light illuminated, the lighthouse, beacon navigation aid, and a sign of land or rail transit signal, and lighting in the streets and emergency phone, etc..

Station telecommunications bis microwave, and telecommunication equipment, wireless and mobile communication equipment (eg radio communications for military service and training) and weather monitoring stations, etc..Water pumping Consumption, public utility, livestock watering, agriculture, gardening and farming, mining and irrigation, etc.

Agriculture Water pumping, agricultural products fumigator, thrashing machines and water sprayer, etc.   

Lighting a bus stop lighting system, telephone booth lighting, lighting panel, and parking lot lighting, interior and exterior lighting and street lighting, etc..

Battery charging system, emergency power system, battery charge status of the village in the rural areas and supply of energy for domestic use and lighting in a remote area, etc..

Livestock water pumping system, oxygen, and fill the fish and insects trapped lighting, etc..Health center Refrigerator and cool box for keeping medicines and vaccines and medical equipment, etc.

Space Satellite, international space station and spacecraft, etc.

Hill, a remote area, island, forest and remote area networks that facilities are not available, etc..

The power stored

The amount of power generated by solar cells is determined by the amount of light falling on them, which is in turn determined by the weather and time of day. In the majority of cases some form of energy storage will be necessary.

In a Grid-connected system,

the solar array is connected to the mains. Any surplus power is sold to the electricity company, and power is bought back from them when it is needed.

In a Stand-alone system,

however, this is not possible. In this type of system the usual choice for energy storage is the lead-acid battery. The number and type of batteries is dependent on the amount of energy storage needed.

Solar Power Batteries

In stand-alone systems the power generated by the solar panels is usually used to charge a lead-acid battery. Other types of battery such as nickel-cadmium batteries may be used, but the advantages of the lead-acid battery ensure that it is still the most popular choice. A battery is composed of individual cells; each cell in a lead-acid battery produces a voltage of about 2 Volts DC, so a 12 Volt battery needs 6 cells. The capacity of a battery is measured in Ampere-hours or Amp-hours (Ah).

For solar applications a battery needs to be capable of being discharged hundreds or even thousands of times. This type of battery is known as a deep-cycle battery, and some of the many different types are:

Practical usage in Project

The chose of the solar panel and the chargeable battery depends on the following:

How Much Power can you store?

Battery capacity is measured in Amp Hours (egg 17AH). You need to convert this to Watt Hours by multiplying the AH figure by the battery voltage (egg 12V).

For a 17AH, 12V battery the Watt Hours figure is 17 x 12 = 204WH

This means the battery could supply 204W for 1 hour, or 102W for 2 hours i.e. the more energy you take, the faster the battery discharges.

How much energy will your appliance(s) use over a period of time?

The power consumption of appliances is given in Watts (egg 21" fluorescent light, 13W). To calculate the energy you will use over time, just multiply the power consumption by the hours of use. The 13W light fitting, on for 2 hours, will take 13 x 2 = 26WH from the battery. Repeat this for all the appliances you wish to use, and then add the results to establish total consumption.

How much energy can a Solar panel generate over a period of time?

The power generation rating of a Solar panel is also given in Watts (eg 10W). To calculate the energy it can supply to the battery, multiply Watts by the hours exposed to sunshine, then multiply the result by 0.85 (this factor allows for natural system losses).

For the Solar 10W panel in 4 hours* of sunshine, 10 x 4 x 0.85 = 34WH. This is the amount of energy the Solar panel can supply to the battery.

If the project prototype is assumed to be a computer with its monitor the following calculated values is assumed to select both of the solar panel and battery

Power consumed in one hour =1500W

Power in one day =1500x24=36000WH

Total Power Needed: 36000Wh

The battery that the prototype need: 3000Ah of Battery Power

And the needed Solar Panel(s):882Watt (assuming 4 hrs sunlight)

So the required information is calculated from the market the battery and the solar panel will be selected depending on the life time, maintenance and the price.

Chapter 4

TCP/IP Protocols

4.1 Introduction

Two major technologies are driving the information society of the late 90s: cellular telephony and the Internet. While both developments have taken place independent of each other in the past, manufacturers and operators of cellular networks are showing increasing interest in combining both technologies to provide wide-area cellular Internet access. Today it is already commonplace to see users "dial-in" to the Internet via widearea cellular by connecting their laptops and palmtops to a mobile phone. In the near future, integrated devices will become available turning mobile phones running the TCP/IP stack or likewise palmtops equipped with cellular radios into regular Internet hosts. We believe that in the future a considerable fraction of the overall number of Internet hosts will be wireless devices. In this paper we specifically look at GSM (Global System for Mobile communications), today undoubtedly the most successful digital cellular telephony system. While significant work is currently being put into providing higher bandwidths in GSM other challenges have yet not been addressed. Two problems that exist when using GSM as the access network tithe Internet and that are not related to bandwidth are highlighted. We reveal the extremely high latency of the GSM link which through a series of measurements was determined to have a magnitude comparable to satellite links.

Today, but none of these services low bandwidth (<600 bit / s) really qualify as subjects for TCP / IP, in part because they do not provide constant communication on both sides. However, you can use to access the Internet through gateways to support interactive applications which are based on the exchange of small amounts of data. Wireless internet is the most powerful access technology to be available in a wide area in almost every country in the world by the turn of the millennium is GPRS (General Packet Radio Service).

GPRS is a packet data service, which was to become a unified network in GSM. The main advantages to users of GPRS is that they are always on the line, and can determine the bandwidth dynamically also disproportionately on up and - and falling pay-per-transmitted / received data size. Benefits to operators of GSM GPRS display a highly efficient and cost-effective use of shadow radio and network resources. You can find more details on GPRS in.

Function of Protocol in Network Communication

Technology independent Protocols

Many diverse types of devices can communicate using the same sets of

This is because protocols specify network functionality, not the underlying technology to support this

Internet Protocol Suite is a set of Internet protocols that are used in the Internet and other similar networks. It is commonly known as TCP/IP, because of its most important protocols: Transmission Control Protocol (TCP) and Internet Protocol (IP), which were the first networking protocols defined in this standard. Modern IP networking represents a synthesis of several developments that began to evolve in the 1960s and 1970s, namely the precursors of the Internet and local area networks, which emerged during the 1980s, together with the advent of the World Wide Web in the early 1990s.

Internet Protocol (IP)

(IP) The Internet Protocol: is the network protocol layer (layer 3) includes information and to address some of the information that enables the control to route packets. Been documented intellectual property in RFC 791 and is the primary network layer protocol in the Internet protocol suite. Along with the Transmission Control Protocol (TCP), and IP represents the heart of the Internet Protocol. Intellectual property and two primary responsibilities providing connectionless, best-effort delivery of datagram's through an internetwork. Providing fragmentation and reassembly of datagram's to support data links with different maximum-transmission unit (MTU) sizes

The Internet protocol suite has four abstraction layers, each with its own protocols. From lowest to highest, the layers are:

The link layer contains communication technologies for a local network.

The internet layer connects local networks, thus establishing the internet.

The transport layer handles host-to-host communication.

The application layer contains all protocols defined specifically for the functioning of the vast array of data communications services. This layer handles application-based interaction on a process-to-process level between communicating Internet hosts

The TCP/IP model (Transmission Control Protocol/Internet Protocol)

TCP/IP is based on a four-layer reference model. All protocols that belong to the TCP/IP protocol suite are located in the top three layers of this model.

DOD model since it was designed for the department of defense, or the internet protocol. It has the following layers, as shown in the following illustration.

TCP/IP model corresponds to one or more layers of the seven-layer Open Systems Interconnection

(OSI) reference model proposed by the International Standards Organization (ISO).

 The four layer TCP/IP protocol. Each layer has a set of data that it generates:

1. Link layer is compatible with the hardware, including device driver and interface card. Link layer has data packets associated with it depending on the type of network being used such as ARCnet, Token Ring or Ethernet. In our case, (Ethernet.)

2. The network layer manages the movement of packets around the network and includes IP, ICMP, and IGMP.

It is responsible for making sure that packages reach their destinations, and if they don't, reporting errors.

3. The transport layer is the mechanism used to Gelatin computers to exchange data with respect to software. The two types of protocols that are the transport mechanisms are TCP and UDP. And I will talk about TCP and UDP in this document.

4. The application layer refers to networking protocols that are used Vidam various services such as FTP, Telnet, BOOTP, etc. Note here to avoid confusion, that the application layer refers generally to protocols such as FTP, Telnet, ping, and other programs designed for the purpose of specific and governed by a specific set of protocols specified by the RFC (request for comment).

However, the program can that I may write a definition of the structure of their data send between the client and the server program as long as the program we are working on both the client and server machine understand our protocol.

For example when our program opens a socket to another machine, it is using TCP protocol, but the data you send depends on how o structure it.

The types of services performed and protocols used at each layer within the TCP/IP model are described in more detail in the following table:

Describe TCP/IP Mode

Application Layer (process-to-process):

This is within the scope of applications that create user data and communicate this data to other applications or processes, or other in the same host. An often called partner contacts his peers. This is where the "highest level" protocols such as SMTP, FTP, SSH, HTTP, etc. that work.

Transport Layer (host-to-host):

The transport layer is a networking system between network hosts two, either on the local network or on remote networks separated by routers. In terms of flow control and error correction, and communication protocols exist, such as TCP. This layer deals with opening and maintaining communication between hosts on the Internet.

Internet Layer (internetworking):

The Internet layer has a mission for the exchange of packet data across the border in the network. And therefore also referred to as the class that define the Internet, but it defines and sets the Internet. In this layer defines the addressing and routing structures used in the TCP / IP protocol suite. Primary protocol in this area is the protocol Alanturntalve identifies IP addresses. Function in the guidance is to transfer data packets to the router contains the following IP connection to the network closer to the point of final data.

Link Layer:

This class specifies methods of communication within the scope of the link local network, which hosts to communicate without interference routers. This class describes the protocols used to describe the structure of the LAN interfaces to affect the transfer of data blocks on the web to the next layer neighbor hosts. (cf. the OSI Data

Link Layer).

Practical usage in project

In the project there is a network between the screens and the control room. The used protocol will be the TCP/IP protocol. This protocol uses the IP as an address for both the control room and any screen of the screens. so for any of the screen to talk with control unit it must know the IP of the control room and also for the control room to talk with any of the screen it must know the IP of that screen. To do this the IP address for both of the control room and the screen must be static but this statics IPs cost more than the Dynamic IPs. The idea was that the IP address for the control room will be static and the that is for every screen will be dynamic, there will be a folder for every screen on the control room server and the screen know the IP of the control room so it is easy for it to get the required videos and instructions from this server and also it is easy for the control room to replay for that screen by extracting the IP address of the source screen from the received Packet.