3) BACKGROUND AND OBJECTS OF THE INVENTION:

Life in villages, without electricity, would almost come to a halt after sunset. The activities in the night are carried out in the dim, smoky glow of a kerosene lamp. And often, people have to strain their eyes using the light from a cooking fire. Children are required to study in the same light. As many as 100,000 Indian villages are not yet electrified - implying that they do not have a single electric bulb glowing in the night in those villages.

This scene would change if low-cost, energy-efficient lamps are available that are powered entirely by the sunlight which is an abundant natural resource. LED Solar Home lighting system is such a light source mainly targeted to address this type of rural home lighting application.

The objective of this invention is to develop a home lighting system that utilizes solar energy and LED light sources in conjunction with a battery and a charge controller unit to deliver good quality light for an adequate period of autonomy based on a design that is robust, simple to use and maintain.

4) PRIOR ART AND SHORTCOMINGS OBSERVED:

People in the underdeveloped areas lack electricity and use oil lamps for home lighting. Oil lamps are expensive, inefficient and are prone to the danger of fire accidents. Oil lamps release C02 and other harmful gases in to atmosphere and hence are not environment friendly. They are hazardous and cause environment pollution leading to breathing problems.

To overcome these draw backs of oil lamps in the rural environments, solar operated conventional lights (Incandescent bulbs, Fluorescent or CFLs) were introduced for home lighting applications. These lights suffer from the shortcomings of inefficiency, flickering, short-life due to frequent burnouts and associated maintenance costs.

The LED based Solar Home Lighting System is proposed to overcome the above said drawbacks and to offer an efficient and high intensity home lighting solution with long life to cater to the requirements of the rural households and pockets of closely knit communities. The LED based solar home lighting system gives high brightness with very low power consumption and as a result, requires very small solar panels and batteries compared to the other lighting systems.

5) SUMMARY OF THE INVENTION:

The LED based solar home lighting system of the present invention uses sunlight to power one or two high intensity LED lights that provide light up to 15 hours (autonomy) on a fully charged battery. The Home lighting system features a solar photovoltaic (SPV) module, a charge controller, a rechargeable battery and LED light sources.

The SPV module consists of a number of crystalline silicon solar cells (a semiconductor device which when exposed to sunlight produces DC electric power) that are interconnected in series combination and hermetically sealed with a toughened front glass cover. This module is used for charging the batteries simultaneously delivering power to the lighting system when sufficient sunlight is available.

The Charge Control Unit (CCU) consists of a charge controller and a rechargeable storage battery. The charge controller is a micro controller based DC/DC step down converter used by a solar power system to charge the battery and also deliver sufficient power to the LED light sources. The function of this controller is to extract maximum amount of power from a given solar module by forcing it to operate at its maximum power point, thereby ensuring that the electrical characteristics of the system are met for optimum performance and reliability. The controller also protects the battery from overcharge, deep discharge, reverse polarity and short circuit and thereby ensuring healthy battery condition; a Blocking diode is arranged in the charge controller between photovoltaic generating system and battery terminals to avoid the discharge of the battery (or reverse flow of the current from battery to SPV) through the module during the no-sunlight period.

The rechargeable storage battery stores the energy generated by SPV panel. The charge controller charges the sealed maintenance free (SMF) battery used for storage. 75% of the rated capacity of the battery should be between fully charged and load cut-off conditions. Whenever the load is to be supplied during a period of insufficient sunlight, storage elements such as batteries must be used. These are commonly used in both standby and charge- discharge applications. They are economical and reliable, especially the recently developed SMF batteries.

LEDs are used as Light Sources in the luminaires in the present invention. One luminaire of 9W or two of 5W each of 2ft tube lights can be used; the luminaire gives high intensity light with very low power consumption. Optionally other types of luminaires like bulbs can also be used with different wattages.

LED Solar Home Lighting System is provided with indicators, visible outside the system, to display operating status to the user. These include ON/OFF indication and state-of-charge indication. Other status conditions may be contemplated as options. ON/OFF indicator shall also have provision for dimming - reducing the brightness - to 50%.

LED Solar Home Lighting Systems are for use in the rural households where grid power is either not available or in shortage - for Indoor or Outdoor use under the roof, as they are not designed for severe weather conditions; however, same can be extended for street lighting applications with suitable IP rating.

Community lighting solutions employ multiple LED lights for a closely knit neighbourhood of a cluster of houses for lighting both inside and outside the homes to light the common areas with a single large power source.

LEDs offer several operational advantages as light sources:

1. Consistent Light output
2. High Brightness (Lumens / Watt)
3. Long Life - more than 50,000 hours
4. Virtually No Maintenance / No replacements
5. Eco-friendly - No Pollution

6) DESCRIPTION OF A PREFERRED EMBODIMENT AND METHOD:

The LED Solar Home Lighting System of the present invention is described with the help of the Fig 1.

The LED Soiar Home Lighting System consists of:

4. A Solar Photo Voltaic (SPV) Module
5. A Charge Controller Unit (CCU)
6. A storage battery
7. One or two Luminaires based on LED Light sources

The SPV Modulel converts the solar energy to DC power which is used to charge the rechargeable battery2(b) incorporated in CCU2, exercising all precautions to ensure a long life of the battery.

A Charge Controller 2(a) incorporated in the CCU charges the battery and delivers power to the LED light sources3. It also protects the battery from overcharge, deep discharge, reverse polarity and short circuit; a Blocking diode2(c) is arranged to protect the battery from reverse current flow from battery to SPV during non sunny hours.

Targeted Specifications

Table

Claim(s) We Claim:

1. A LED based Solar Home Lighting System consisting of the following:

 Solar Photo Voltaic (SPV) Module

 Charge Controller Unit / Storage Battery

 Luminaires in the form of 2ft tube lights with LED Light Sources

2. A LED based Solar Home Lighting System in claim 1 wherein the basic energy source is sun light and a charge controller is used to charge a sealed maintenance free battery from the solar panel and deliver sufficient power to the LED light sources.

3. A LED based Solar Home Lighting System in claim 1 wherein the lighting solution is essentially based on solar energy and hence is ideally suitable for rural environments where grid power is neither available nor accessible with ease.

4. A LED based Solar Home Lighting System in claim 1 wherein the controller is designed with features that protect the battery from overcharge, deep discharge, reverse polarity and short circuit and the electronic circuit from reverse current flow during charging.

5. A LED based Solar Home Lighting System in claim 1 wherein the luminaires employ high powered white LEDs as light sources with high brightness, low power consumption and long-life of more than 50,000 hours. The light sources are also glare-free and prevent eye strain.

6. A LED based Solar Home Lighting System in claim 1 wherein one 9W or two 5W luminaires of 2ft tube lights are supported. Optionally other models like bulbs with different wattages can also be used.

7. A LED based Solar Home Lighting System in claim 1 wherein it provides autonomy of up to 15hours of light on a fully charged battery in its basic configuration supporting one 5W luminaire. The autonomy is less when 2 luminaires of 5W or one luminaire of 9W are used.

8. A LED based Solar Home Lighting System in claim 1 wherein it is also easy to install and use with practically zero maintenance.

9. A LED based Solar Home Lighting System in claim 1 wherein the LED based luminaires also extend themselves to economical and low cost community lighting solutions for a closely knit pocket or cluster of a small number of houses in the rural environment with slightly increased sizes of panel and battery, and with additional common facilities like street lighting besides home lighting. This is expected to facilitate the Governments to electrify more rural and underdeveloped regions without the huge investments called for in generating and distributing the grid power to these remote locations.