Miniaturized Solar Home System for lighting purpose with Light Emitting Diodes: www.reein.org

Miniaturized Solar Home System for lighting purpose with Light Emitting Diodes

By A.N.M. Zobayer ( on NATIONAL SEMINAR ON RENEWABLE ENERGY )Date: March 24,2006

Miniaturized SHS for lighting purpose with LEDs

Contents:

• Introduction

• Research Development

• Research Finding

• Conclusion

Introduction

• This research is mainly focused on developing cheap Solar Home Lighting Systems accesible to the poor in rural areas.

• It offers a small Solar Home Lighting System based on :

i. Light Emission Diodes as lighting loads

ii. Motor cycle battery as storage medium

iii.A small PV module

iv.Simple charge controller

Small Solar Home Lighting System

• Lumens : A lamp produces a certain amount of light, This light measure in Lumens.

1 watt at 555nm=683 lumens

• Lux :This light falls on a surface with a density that is measured in lux or foot-candelas.

• Candela :1 candela (1 lm/sr) light source will produce 1 lumen per square foot at a distance of 1 foot, and 1 lumen per square meter at 1 meter.

• Illuminance :A person looking at the scene sees different areas of his visual field in terms of level of brightness, or luminance, measured in candelas per square meter.

Inverse Square Law

E = I/d²

Where:

E=irradiance

I=intensity

d=distence

Source:The Light Measurement Handbook

Intensity Measurement in Rural Areas

General LED Characteristics

• The directional sensitivity indicates a ratio of the LED luminous intensity relative to its axial luminous intensity(=100%) as viewed from a direction of angle of θ with respect to the light source

• The angle at which luminous intensity is exactly 50% of the axial luminous intensity is called a half-value angle θ½ .

Source: LED Technology, Toshiba

Technical data of different LED and CFL

source: Conrad

Life time of LED=100000 hours and CFL = 6000 hours

Luminary Construction

R = (VS - VLED) / ILED

Here

R= Resistance (Ohm)

VS = Supply voltage (volts)

VLED = LED voltage (volts)

ILED = LED current (Ampere)

Brightness Comparision of Different Luminary

LED-1

LED-2

CFL

LED-3

LED-4

Brightness Comparison CFL and Selected LED Luminary

Measurement of Lamps

Illuminance-distence curve

Battery

• The Primary functions of a storage Batteray:

1. Energy storage capacity and autonomy

2.Voltage and current Stabilization

3.Supply surge current

• Types of Battery:

1. Lead-Acid battery

i. Automobile Battery(Motorcycle Battery)/SLI Battery

ii. Industrial Battery

2.Nickel-Cadmium battery

• Lead Acid Battery:

Full discharge terminal voltage=1.9V

Full Charge terminal voltage = 2.4V

Motorcycle Battery : Small capacity automotive battery (6V-12V,5Ah-14Ah @C10).This type of lead-acid battery designed primarily for shallow cycle. Automotive battery provide up to two years of useful service life in small SHS.

Industrial Battery: This type of lead-acid battery designed for deep discharge cycle service.It has long life but too expensive for SHS. A partiular disadvantage with tubular type solar battery for small SHS is that they do not readily accept low rate of charge.

Source: [1]Solar Home System Manual for the design and modification of SHS components [2] A.D. Simmons “PV system design”

Battery Charge Controller

• Main function is to prevent batteries from being overcharged

• Many charge controllers have additional feature

-Deep discharge protection

-Different set points for different battery types(or use adjustable set point)

-Voltage and current indicator/meter

-Temperature compensation

Charge Controller set points for small SHS

• High voltage array disconnect voltage= 14.4 ±1 V

• Array reconnect

voltage= 13.5 ±1 V

• Load reconnect

voltage= 12.5 ±1 V

• Low voltage load

Disconnect

voltage= 11.5V-11.0V

Source: Batteries and charge controller in stand-Alone Photovoltace Systems, Sanida National Laboratories

Rahimafrooz Charge Controller

Comparison Different Charge Controller Set Points

What do we get out of a PV module

• PV Module output is affected by insolation and temperature.

• PV curve is best indicator of module performance

I-V & Power curve

Effects on I-V Curve by temperature and solar radiation

Crystalline vs Amorphous I-V Performance

Amorphous Solar cell

Crystalline Solar cell

System Sizing

System Design (Good weather)

	SHS-1 (CFL Lamp)	SHS-2 (LED lamp-2)
Systems Voltage 12 volts
Energy Consumption/day	6.38 Ah	1.1 Ah
Battery Capacity (DOD 50%)	12.76 Ah	2.2Ah
Total Number of battery	1(14Ah@C10)	1(5Ah@C10)
Total number of module	2 (@6Wp)	1 (@6Wp)

Source: Universal Technical Standard for solar Home Systems by Thermie B

System Design (Bad weather)

	SHS-1	SHS-2
Systems Voltage 12 volts and Days of autonomy 3
Energy Consumption/day	6.38 Ah	1.1 Ah
Battery Capacity (DOD 50%)	38.28 Ah	6.6Ah
Total Number of battery	1(50Ah@C20)	1(9Ah@C10)
Total number of module	1(@36Wp)	1 (@6Wp)