A to design a simple solar battery charging

AProject Paper on Solar Battery ChargerAbstract- The main target of our project isto design a simple solar battery charging circuit where a photovoltaic (PV)panel is used to convert the solar energy into electrical energy and stored inthe rechargeable battery. The shunt regulator has also been used to prevent overcharging.

We have worked on the following circuit design.                     Fig.1: Solar   Battery  ChargerI.  INTRODUCTIONThe demand of energy inthe world is very high.

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The continuing expansion of human population andeconomic growth are the main reasons for such a huge demand of energy. Anon-renewable energy sources are being used since a long time to fulfill adaily necessity of energy consumption in the world. The fossil fuels such ascoal, natural gas, petrol are the key sources of non-renewable energy. The demandof fossil fuels is extremely high, but they are very limited in quantity.

Theyare not consistently accessible in the world. On other hand, there are manydisadvantages of using non-renewable energy. The fossil fuels are primarilycarbon based. The use of coal, oil and other natural gas produces huge quantityof carbon dioxide and carbon monoxide, and these are the main causes for globalwarming. They play a crucial role on destroying the ozon layer too.

The oxidesproduce from burning fossil fuels make a rain acidic which is very dangerousfor living creatures in the planet. To avoid the energy crises in future, thecreation and the implementation of other sustainable energy sources areseverely important and required. Sustainable energy is all about creating pureand renewable sources of energy. It does not use any sources that are based onfossil fuels. From few choices of sustainable energy, the solar energy isconsidered the most effective and ideal form of sustainable energy. It is oneof the most common thing in the sector of renewable energy. Thermal energy andthe electrical energy are the two types of energy where solar radiation isnormally converted into.

The energy in solar power is entirely obtained fromthe power of the sun. Solar energy is a boundless, renewable energy source. Solarenergy can be applied in many implementations like irrigation, ruralelectricity, and satellite communications. It is accessible to everybody in alllocations at impartially equal manner, whereas the fossil fuel sources areobtainable only at certain locations. The solar energy does not produce anyharmful rays, so it does not cause any damage on our ecosystem. In short, solarpower is an extensive and inexhaustible form of energy.Regarding our project,we have designed a solar battery charging circuit which is entirely relatedwith solar power energy.

The main purpose of our design is to charge arechargeable battery by using solar energy. In simple words, solar energy is converted into electrical energy andstored in a rechargeable battery. Battery can be again recharged, after the batterygets discharged.            Components used:-       17V40W Solar Panel-       Rechargeable12V Battery-       Resistors-       Zenerdiode-       Capacitor-       Comparator-       Darlingtonpair-       DiodeII. SOLAR PANELSolar Panels are toolsthat convert light into electricity.

The solar panel is used as a device of alarger photovoltaic system to produce and provide electricity for differentcommercial and residential use. One solar panel can only generate a limitedquantity of power, so majority of applications use multiple panels. It is acollection of solar cells. The solar cells are the fundamental building blockof solar panel. Solar cells are also called photovoltaic cells, which operateto create electricity straightly from sunlight.

The sun radiates a hugequantity of energy every second. The solar cells are composed of siliconsemiconductors which absorb sunlight and transformed it into electricity. Thesolar cell is located between n-type silicon and p-type silicon. The each cellis designed with a positive and a negative layer to create an electric field,just like in the battery. When sunlight hits solar cells, photons are absorbedin the cell, and their energy causes electrons to become free. The electronsmove towards the bottom of the cell, and exit through the connecting wire. Thisflow of electrons is considered as electricity.

By combining solar cells inphotovoltaic panels, the required amount of electricity can be produced toperform a specific job.The PV output power isrelied on solar irradiance and cell temperature. The following fig.

2 hasdisplayed that the low irradiance results to low power, and high temperatureresults in reducing in output power. The accuracy of the other components ofthe entire system and environmental situations are other aspects which thequantity of energy delivered by a PV module is dependent. Likewise, the rise insun power increase the output power of the solar cells, but simultaneously, theincrease of cell temperature impacts its electrical working capacitynegatively.   Fig.2:P-V characteristics of a PVIII.

RECHARGEABLE BATTERYFor our design, we haveused 12V rechargeable battery. The battery is composed up of voltaic cells.Batteries are very significant of any productive solar panel system. The energycreated by the sun and solar panels are stored in the batteries. It can be saidthat in the absence of batteries, the system becomes totally ineffective.

Regarding a battery selection for our design, deep cycle battery has beenpicked over shallow cycle battery. Deep cycle battery has designed to supply astable amount of current for a long duration of time phase where as shallowcycle battery supply a very big amount of current for a very short duration oftime. Moreover, it can be said that a shallow cycle battery has a lot ofcurrent available but at the same time it has a large amount of voltage drop.Rechargeable type battery has its electrochemical reactions electricallyreversible where as a non-rechargeable type battery generates electricity usingan electrochemical reaction. Lead-acid batteries are most often used for smallPV charging system, and the main reason for this is because of their capacityto supply a substantial amount of current. The different phases of charginglead-acid batteries is very important because it limits how much current we cansend to the battery at different times.

Our system only excess voltage fromreaching the battery, and does not regulate the amount of current sent to thebattery. The fig.3 below demonstrates a different charging phases of alead-acid battery. The constant-current charge, topping charge, and float chargeare three main charging stages of lead acid batteries. Moreover, differentchemical compositions might need more complex charging phases.Fig.

3:Charge stages of a lead cycle batteryIV.RESISTORA resistor is anelectronic device that controls or regulates the flow of electrical current ina circuit. The current travelling via a resistor is directly proportion to thevoltage across the resistor’s terminals. If a resistance is high in a circuit,then it can be determined that the flow of current is small for a given voltage,where as if the resistance in low, then the flow of current is high for a givencircuit. The resistivity of resistor is affected by the temperature of aresistor. If the resistor gets heated, then it is going to be more resistanceto current flow. Resistor is also used to add a required voltage for an active device.

V. COMPARATORComparator circuits arecommonly operational amplifier based. They compare two or multiple inputs andsignal an output to let it know about which input is either greater or smaller.The outcome of this comparison is denoted by the output voltage. They usuallycompare voltage or current levels as inputs. While comparing the inputs, if oneis higher than the other one, then the comparator circuit output stays in onecondition, but when the inputs state are reversed, then the output of thecomparator switches.

The comparator can also be used for identifying if anarbitrary varying input signal hits reference level or a defined thresholdlevel. The different components such as diodes, op-amps can be used toconstruct the comparator. Moreover, the comparators can be spotted in variouselectronic implementations which may be used to drive logic circuit.  The comparators are extensively being used inautomatic switching devices, environment monitoring devices, analog to digitalconverters.   Basically, in both accepting and outputtingcase op-amp deals with analog signal, but the comparator only produces outputas digital signal.            Inour circuit, comparator is used to bias the Darlington pair amplifier when thesolar panel outputs excessive voltage. The potentiometer is used to controlwhen the amplifier turns on, which sets the maximum charging voltage for thebattery. In the following LT spice model, the use and implementation ofcomparator in our circuit has been shown.

Fig.4:Comparator in LT spice modelThe following fig.5 has demonstrated the performanceof comparator in our circuit. Looking at this figure, it can be said that whenV+ is greater than or equal to V-, the op-amp turns on, and here it isrepresented by the pink and teal spikes.          Fig.5:Comparator performanceVI.DARLINGTON PAIRThe Darlington pair isa very essential circuit configuration for various electronic circuitsimplementation. It gives numerous benefits that other structures of transistorcircuits are not capable to provide, and this is the main reason of its used invarious sectors of electronics scheme.

In many implementation and application,a single transistor might not be able to transfer enough current needed by theload, which means the amount of input current accessible to switch on thetransistors is very less, so in this case, Darlington pair can be veryeffective to use because it consists of two transistors but behaves as a singletransistor with a very high current gain. It provides very high input impedancefor overall circuit. Darlington is also called Super Alpha Pair.            Inthe following LT spice model, the functioning and implementation of DarlingtonPair in our circuit has been shown.Fig.

6:Darlington Pair Amplifier in LT spiceWhen the DarlingtonPair is biased through the R_Driver resistor by the comparator, the amplifieris powered on. As the voltage from the comparator increases, the Beta value ofthis amplifier sky rockets, and this causes a massive current rush through theburn-off resistor. The burn-off resistor is exclusively used to dissipate anyexcess power to battery through heat generation. The following fig.7 hasdemonstrated the performance of Darlington Pair in our circuit.

From thefigure, it can be concluded that, in our circuit, the Darlington Pair amplifiesthe base current by nearly 7,000 times during peak power consumption.   Fig.7:Darlington Pair performanceVII.MATH EQUATION            Avery few equations were used to verify the circuit.Ohm’s law: V=I*RPower: P=I*RVoltage Divider: = * / Transistor amplification:= (?+1) * Op-Amp Gain:=  / ( -)Power Transmission Efficiency:  /  Here,  is the power going to the battery.

VIII.RESULT            Regardingour model, the voltage source with a resistor does not exactly reflect theconstant current supplied by a solar panel; therefore the results are notperfectly accurate. Moreover, using sine wave for this model is fairlyirregular.

In reality, it looks more like a square wave. When adding whitenoise, it really did not reproduce noise in the field. Overall, the powerefficiency was at a maximum of 70%, which explains that 80% of the power hasreached the battery directly.            Forsome reason, the battery voltage in Fig.8 always stayed above 2V, even when thesupplied voltage was less than this. This leads to the asymptotes in Fig.

9 forthe conversion ratio.  Fig.8: Solar panel voltage, charger voltage and chargecurrent over time.  Fig.9: Poweroutput of solar panel and power input of battery over time. Power conversionratio over time also shown.

IX.CONCLUSIONSolar battery chargerdoes not need any external electrical sources to get battery recharged, so itcan be said that this design has a benefit of freedom of movement. To chargethe battery at constant voltage, solar charger requires voltage regulator. Onthe other hand, the voltage supplied by a solar panel can be variedconsiderably depending with the time, climate situation, and irradiation fromthe sun. The solar cells are the back bone of any electric circuit. For ourcircuit, solar panels are used as a power supply and supply into a voltageregulator in order to have a constant voltage charging for the battery.

Batteries are the most effective way to store solar energy. Consequently, solarcharger circuits target at charging batteries rather than driving components.When the battery gets fully charged, it is very important to cut off charging.This can be handled by using a zener diode. It switches on if there is acut-off voltage and supplies the current via the transistor. The solar batterycharger is one of the best examples of solar powered devices. The batteries canbe recharged and reused by using solar power. By implementing this design, thenon-renewable energy source can be conserved.

This design can be taken as oneof the good example for how without spoiling the environment, the naturalenergy sources can be used for the energy needs. The most vital thing to benoticed is that by utilizing the solar power, the rate of consumption ofnonrenewable sources can be instantly minimized. Moreover, the solar energy isgetting more powerful as a renewable source because of its many beneficial features.The solar energy needs collectors and different equipment to convert solarenergy into electrical energy, but it is always free and renewable.

The solarenergy is sustainable source. The source of sustainable energy provides thenecessity of present generation without harming the capacity of upcominggenerations to meet their requirements. In simple word, solar energy isreferred as sustainable energy source because it can never be over consumed.

Thesolar energy is considered as an everlasting source of renewable energy whereas sources of fossil fuels are limited in quantity. After working on ourproject, we have learned to explain the connection between the direction ofelectrons flowing via a battery and the change in the battery’s voltage. Thetechnological improvements are steadily being done in the device and configurationof solar power components, so as a result, the solar cells in the panel isbecoming more effective and powerful at converting solar energy into electricalenergy. In future, more exceptional technological renovation could happen, andmore effectiveness and benefits could be achieved from solar power energy.   


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