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solar energy project
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Gone are the days when you would look up at the Sun and curse yourself for being out on a hot sunny day. Take pride; very soon you will be a walking energy station with people asking you to help them charge their batteries with your clothes!
This isn’t a scene out of a Sci-Fi movie. It is the simple application of solar cells. They are the only way we can convert sunlight into electricity directly and day by day they are getting better, smaller and cheaper.
Nothing can dare challenge the sun when it comes to radiating energy. Every hour the energy available from the sun is more than what human’s require for an entire year. Petrol, diesel and all these fossil fuels are nothing but sun’s energy concentrated over years and years. This makes them very efficient in terms of energy per unit of the fuel. So why not tap it directly?
Solar energy isn’t something new. People have used sun to dry and preserve things. Vedic literatures in India even state the use of flying machines which were powered using the sun. Come 21 st^ century, we have come a long way in developing solar cells which are the devices powering our future, converting sun’s energy into electricity.
Solar panels are simply solar cells lined up together in series and parallel so as get sufficient voltage and are p-n junction semiconductor devices with pure silicon wafer doped with ‘n’ type phosphorous on the top and ‘p’ type boron on the base. If the PV cell is placed in the sun, photons of light strike the electrons in the p-n junction and energize them, knocking them free of their atoms. These electrons are attracted to the positive charge in the n-type silicon and repelled by the negative charge in the p-type silicon. Connecting wires across the junction will have a current in them.
Solar cells have come a long way from bulky 6% efficient chunks to thin films with as much as 30% efficiency. They are selling like hot cakes today given their necessity and utility. And the reason being they are faithful good chaps unlike oil which will soon be more precious to us than diamonds and the black monster: coal which has polluted the air, hand in cuff with the other fossil fuels.
We need to understand solar panels so as to understand their applications. Today, we have mono- crystalline, polycrystalline and amorphous thin film panels. Mono-crystalline are so far the most efficient, given that they have the maximum silicon in a unit area so more current for the same number of photons. They are made out of a single silicon crystal as a continuous lattice. While for the polycrystalline panels, molten silicon is poured into molds and separate boundaries can be seen due to this. Lesser quantity of silicon in a unit area means lesser efficiency of production of electricity. Amorphous thin film panels are layers of silicon on a glass surface and are the least expensive. Hence, they are used in applications where you can do away with efficiency for lowering the costs.
Solar panels are really useful in broad daylight but we need energy when the Sun isn’t shining above our rooftops. That’s why we need solar chargers which will store energy in rechargeable batteries. This project aims to make a solar charger using a voltage regulator IC so as to charge a Lead Acid Battery with the constant output voltage obtained through this IC LM317( Details explained later). Today there are many more options like a SOLAR CHARGER IC LT3652. This is an IC with embedded MPPT (Maximum Power Point Tracking) algorithm. MPPT simply means the IC gets the maximum possible power from the solar panel by sampling its output and applying the proper load resistance. This small chip simplifies life given its ease of use and maximum efficiency is always ensured.
Source : Wikipedia
Even 15% efficient solar panels installed across the world’s wasetelands can produce enough clean energy to sustain mankind for a year.
Yet new technology is continuously being developed though solar energy generation is still in its infancy. The concept of SOLAR FARMING is new and catching up fast in investors. India is a tropical country and can soon become the Saudi Arabia of solar energy. With Concentrated Photo Voltaics (CPV : which increase efficiency by concentrating large amount of sunlight on the solar cells using mirrors) coming up in India, we are definitely headed towards a cleaner future.
This project aims to make a solar charger circuit using IC LM 317 which is an adjustable voltage regulator.
SOLAR PANEL, 5W, 17.5V,362X163X8MM Power Rating: 5W Power Voltage Max: 17.2V Current at P Max: 290mA Open Circuit Voltage: 21.4V Short Circuit Current: 320mA Solar Battery charger IC(LT3652) Battery: Li-ion(3.7V,1400mAh)
Adjustable Voltage Regulator so as to have constatnt voltage charging for the battery
Lead Acid Battery ; 6V, 5Ah
This solar charger then charges a Lead acid battery which in turn will power our solar lamp.
Note: Several options are available in solar charger circuits but I chose to have IC LM317 given the limitations in availability of the ICs as well as the learning involved in having an entire analog circuit as compared to just having a ready to use Solar charger IC.
Components Involved:
This is our power supply. It is responsible for charging the battery.
applications like our solar lamp, they are good enough. Care must be taken while handling acid
batteries.
Note: We conduct experiments step by step to understand how each component works and then assemble the circuit together.
1. TO study how solar panels behave to different intensities of light Conditions Open circuit voltage across the panel Covered with cardboard 0.263V Facing the desk 0.468V Covered with Paper 2.5V At the window(11am) 14.72V In the lab 7.62V At the desk 5.2V Using a torchlight at distance 15cm 11.22V At the terrace(2pm) 21.2V(maximum Voc=21.4V)
Observations : Solar panels are heavily dependent on the intensity and the nature of light falling on them to produce any kind of voltage. The output varies right from 0.2V to 21.2V.
Conclusions : Sunlight matters a lot. So to make the best out of a fixed solar panel, we need to have some kind of power tracking which will always allow the panel to produce a maximum power by impedance matching (external resistor across the cell).
2. To study the working of IC LM317(using power supply)
Conditions: R1=180Ohm, R2=500ohm
Vin Vref Vout Vin- Vout
Iref(mA) Iadj(uA)
6.85V 1.225 4.64V 2.12V 6.81 19 8.30V 1.225 4.657V 3.67V 6.815 53 10.59V 1.224 4.65V 4.65V 6.815 46. 12.16v 1.225 4.667V 4.667v 6.81 73 15.68V 1.225 4.68V 11.00V 6.81 99 23.67V 1.225 4.651V 18.19V 6.817 41
Using Solar panel
Conditions: R1=180Ohm, R2=500ohm
Vin Vref(V) Vout Iref(mA) Iadj(uA) 4.85V 1.225 4.64V 6.81 19 6.30V 1.225 4.657V 6.815 53
Vin(at the IC) Vout Vled+Vresistor 10.62V 7.40V 7.12V
With solar panel
7. To study the charging of batteries using the solar panel Setup: Battery is firstly discharged upto 5.99V and then charged using the solar panel. Readings are constantly measured after equal intervals of time. Two bulbs White And Yellow used to simulate sunlight.
I am interested in learning how to make easy, portable and ready to use devices which run on solar power. The scope of imagination is large as solar power can run anything on DC voltage. Specifically, I want to explore solar chargers in greater detail and understand how to increase efficiency of power generation (IC LM317 drops the precious 3V across it thus wasting energy). Another area of interest Is exploring different technologies available in making solar cells( Mono-crystalline, Polycrystalline, Thin Films) and be able to explain why their efficiency changes so much by understanding their crystal structures.
