Building a simple solar powered outdoor light

[navino87]

Requirement : To light a 20 - 25 watt DC 12v lamp for 7 hours a day

Hello friends.. I just wanna make a simple solar powered outdoor light for my farm house where there is a frequent power cut. The temperature is generally very high in my place Today the temperature here is 109 degree.. Iam a complete newbie when it comes to this project. I have read an guide by Jeffrey Yago from the following page :http://www.backwoodshome.com/articles2/yago92.html.

From this above guide, i came to an understanding that it requires 4 main components to go ahead with this project. 1. solar array 2. charge controller 3. a battery 4. DC Lamp.

Think we will be having 10 to 11 hours of full-equivalent sunlight.. So, now i will be needing a say a 75 watt solar panel. So, for 75 watt panel with 10 hours of equivalent sunlight, what is the capacity of the battery should i look for?? Would a 26Ah battery do the job for me?? Also, please give me a fair idea about which lamp i should go for.. Guess, i should look for some efficient 12v lamp as the battery voltage is 12v And i dont wanna spend on inverter.

Here goes the calculation part :

Solar array having a 75-watt nameplate rating could generate 750-watt hours (75 watt x 10 hours) of power during a very sunny day. A 15-watt fluorescent lamp would operate 50 hours on this energy (750 watt-hour/15 watts), assuming no efficiency losses.

To Power a 15-watt fluorescent fixture an average of 7 hours each night. (15 watts x 7 hours)/ 12 volts = 8.75 amp-hour/day
Loss during both the battery charging and battery discharging process, and additional efficiency losses for the fluorescent ballast, charge controller, and wiring, adding at least 30 percent more to our initial calculation. (8.75 amp-hour) + (2.6) = 11.35 amp-hour/day

Bellow is the specification of the 75 Watt panel that iam planning to source :

[QUOTE]ELECTRICAL CHARACTERISTICS : SS-75
Nominal Power (Pm) in Watts : 75
Open Circuit Voltage (Voc) in Volts : 21.0
Short Circuit Current (Isc) in Amps : 4.76
Voltage at Maximum Power (Vmp) in Volts : 17.0
Current at Maximum Power (Imp) In Amps : 4.41
Maximum System Voltage : 1000V

PHYSICAL PARAMETERS
Solar Cells per Module (Units) : 36 Length X Width X Thickness (LXWXT)
in mm : 900X675X35 In Inches : 35.4X26.6X1.4
Weight in Kg : 7.95
Mounting Holes Pitch(Y) in mm : 450.00 In Inches : 17.7
Mounting Holes Pitch(X) in mm : 629 In Inches : 24.8
Area in Sq. Meter : 0.61 In Sq. Feet : 6.66
Junction Box : IP 65

OTHER CHARACTERISTICS
Type of cell : Mono / Multi crystalline Silicone
Front Face : Tempered Glass (Low Iron)
Encapsulate : EVA (Ethylene Vinyl Acetate)
Frame : Anodized Aluminium
Junction Box : Weather Proof Nylon 6
Temp. Coefficient : Voltage: -0.123 V/

[Wy_White_Wolf]

....Think we will be having 10 to 11 hours of full-equivalent sunlight...

Sorry but sunlight and solar insolation are 2 different things. No place on earth averages 10 hours of solar insolation daily. Plus with off grid you need to calculate for the worst case, which will be winter for your location. So let us know your location (or nearest large city) and we can start doing some meaningful calculations to help you.

WWW

[navino87]

Sorry but sunlight and solar insolation are 2 different things. No place on earth averages 10 hours of solar insolation daily. Plus with off grid you need to calculate for the worst case, which will be winter for your location. So let us know your location (or nearest large city) and we can start doing some meaningful calculations to help you.

WWW

Country : India
State : Tamil Nadu
City : Vellore

http://www.timeanddate.com/worldclock/astronomy.html?n=1789

TY

[navino87]

Feel iam more optimistic abt the 10 hrs of full-equivalent sunlight .. Guess there will be atleast 7 - 8hrs of full-equivalent sunlight at my place.. Now below is the revised calculation..

Solar array having a 75-watt name plate rating could generate 525-watt hours (75 watt x 7 hours) of power during a very sunny day. A 15-watt fluorescent lamp would operate 35 hours on this energy (525 watt-hour/15 watts), assuming no efficiency losses.

To Power a 15-watt fluorescent fixture an average of 7 hours each night. (15 watts x 7 hours)/ 12 volts = 8.75 amp-hour/day
Loss during both the battery charging and battery discharging process, and additional efficiency losses for the fluorescent ballast, charge controller, and wiring, adding at least 30 percent more to our initial calculation. (8.75 amp-hour) + (2.6) = 11.35 amp-hour/day

[Mike90250]

You should use PV watts http://www.nrel.gov/rredc/pvwatts/ ver 1. to locate a city in India near you, that has historical data, for insolation. Run your planned system as a 1KW (as small as PV watts goes) and then when finished, divide your results down to the size panel you select.

6 hours of usable sun is excellent , 5 is outstanding. Don't forgot about the losses if you don't have a tracking array, your panel will only be aligned correctly for about 15 minutes a day. The PV watts calculator takes all that into account for you.

[navino87]

Thanks for the help mike.. In the PVWATTS, I have selected "IND Madras" under asia. Now could you please help me with inputting other details like DC Rating (kW), DC to AC Derate Factor, Array Type. I will be going for the Fixed type panel fixing. could you please enlighten me with the process of installing panels and other things for this project??

[Wy_White_Wolf]

Closest I came up with is Madurai, India.

It has an Isolation value of 4.15 hours for the month of November.

http://www.gaisma.com/en/location/madurai.html

Madurai, India - Solar energy and surface meteorology
Variable J F M A M J J A S O N D
Insolation, kWh/m

[navino87]

The output from PVWATTS :

"Station Identification"
"City:","Madras"
"State:","IND"
"Lat (deg N):", 13.00
"Long (deg W):", 80.18
"Elev (m): ", 16
"Weather Data:","IWEC"

"PV System Specifications"
"DC Rating:"," 0.8 kW"
"DC to AC Derate Factor:"," 0.770"
"AC Rating:"," 0.6 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 13.0"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:"," 1.8 rupee/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value (rupee)"
1, 5.55, 88, 1.62
2, 6.40, 91, 1.67
3, 6.68, 104, 1.91
4, 6.71, 100, 1.84
5, 6.12, 94, 1.73
6, 5.36, 80, 1.47
7, 4.71, 74, 1.36
8, 4.91, 76, 1.40
9, 5.46, 82, 1.51
10, 5.08, 80, 1.47
11, 4.54, 71, 1.31
12, 4.65, 75, 1.38
"Year", 5.51, 1014, 18.66

[navino87]

Thanks everyone ..

Ordered following and expecting it to be delivered in a week time.

Solar Panel 75Watt $111.11
Phocos Charge Controller CML20A 12/24v, 20A $28.14
Phocos CFL Lamps 15Watt $6.48
Battery 26Ah $48.14

Will update once i receive everything

As per this wiring diagram, I need to add fuses to wires leading to positive of battery and lamp. Could some1 help me with this? How to do this??

TY

[Mike90250]

Thanks everyone ..

Ordered following and expecting it to be delivered in a week time.

Solar Panel 75Watt $111.11
Phocos Charge Controller CML20A 12/24v, 20A $28.14
Phocos CFL Lamps 15Watt $6.48
Battery 26Ah $48.14

Will update once i receive everything

As per this wiring diagram, I need to add fuses to wires leading to positive of battery and lamp. Could some1 help me with this? How to do this??

TY

Splicing and making wire connections, while not complicated, is a precise art, you need to get an electrician friend to help you. It's somewhat like your first try at car repair, I'll fix my brakes.
Help for this learning process can't be given over the internet. MANY fools have made misleading you-tube videos of how to do things, and many are just bad. I don't want your project to go up in smoke.

What is troubling me, is that you have ordered parts, and I don't think you have done proper calculations, your battery seems quite small.

A 12V, 26ah battery, only has 156wh of useable storage, which could give you up to 10 hours of 1, 15W light.

Most batteries that small are sealed GEL batteries, which are not generally good for deep cycle use, and it may not accept the rate of charge the 75W panel give it. Let's hope that the battery is a AGM type.

[navino87]

Thanks mike.. Well, since the battery is available locally, i haven't got it yet.. Just bargained for the price.. The rest I have ordered online.. So, I could go with a higher rated battery if you insist. Please help me with selecting the right battery for this setup..

TY

[Sunking]

Thanks everyone ..

Ordered following and expecting it to be delivered in a week time.

Solar Panel 75Watt $111.11
Phocos Charge Controller CML20A 12/24v, 20A $28.14
Phocos CFL Lamps 15Watt $6.48
Battery 26Ah $48.14

Will update once i receive everything

As per this wiring diagram, I need to add fuses to wires leading to positive of battery and lamp. Could some1 help me with this? How to do this??

TY

Well how long do you want to operate this 15 watt light?

Did I hear 10 hours? 15 watts x 10 hours = 150 watt hours. That battery is completely incapable of doing th ejob and will be destroyed by a 75 watt panel. Minimum battery size is 12 volts @ 70 AH. Anything less and you will destroy your battery in a very short time.

[Mike90250]

Along with Sunkings comment about battery, you need a PV panel, that can recharge the battery in one day, generally only 5 good hours of sunlight. Because of losses, you need to harvest 300 wh of power, to replace the 150wh you use. 300wh / 5 hours = 60 w panel would just barely make it, a 100w panel would be much better.

I also suspect your 75W panel @ only $111 - generally the smaller panels cost a fair bit more per watt.

[navino87]

@ sunking : Thanks bro.. Will ask for the 70Ah battery locally.. What type of battery should i look for? will any 70Ah battery do the job? bcoz iam already running outta budget as i ordered the rest of the component..

@Mike90250 : Thanks mike.. I have ordered the panel directly from the manufacturer. And it is already on the way to my place. Here is the specification of the panel :
[QUOTE]
ELECTRICAL CHARACTERISTICS : SS-75
Nominal Power (Pm) in Watts : 75
Open Circuit Voltage (Voc) in Volts : 21.0
Short Circuit Current (Isc) in Amps : 4.76
Voltage at Maximum Power (Vmp) in Volts : 17.0
Current at Maximum Power (Imp) In Amps : 4.41
Maximum System Voltage : 1000V

PHYSICAL PARAMETERS
Solar Cells per Module (Units) : 36 Length X Width X Thickness (LXWXT)
in mm : 900X675X35 In Inches : 35.4X26.6X1.4
Weight in Kg : 7.95
Mounting Holes Pitch(Y) in mm : 450.00 In Inches : 17.7
Mounting Holes Pitch(X) in mm : 629 In Inches : 24.8
Area in Sq. Meter : 0.61 In Sq. Feet : 6.66
Junction Box : IP 65

OTHER CHARACTERISTICS
Type of cell : Mono / Multi crystalline Silicone
Front Face : Tempered Glass (Low Iron)
Encapsulate : EVA (Ethylene Vinyl Acetate)
Frame : Anodized Aluminium
Junction Box : Weather Proof Nylon 6
Temp. Coefficient : Voltage: -0.123 V/

[Mike90250]

Type of cell : Mono / Multi crystalline Silicone

Silicone = adhesive

Silicon = PV cell. So, I'm not sure what you are actually getting ! Who is the Mfg ??