GB2315120A

GB2315120A - Photovoltaic powered light

Info

Publication number: GB2315120A
Application number: GB9614498A
Authority: GB
Inventors: Mark Sutton-Vane
Original assignee: SUTTON VANE MARK
Current assignee: SUTTON VANE MARK
Priority date: 1996-07-10
Filing date: 1996-07-10
Publication date: 1998-01-21
Also published as: GB9614498D0

Abstract

A self contained photovoltaic powered light unit has a photovoltaic panel, an electrical storage system, a light source and a number of electronic control devices all housed in a case with a transparent top which allows both the entry of daylight and sunlight and the exit of light from the light source. During the hours of daylight the photovoltaic panel automatically charges the electrical storage system under the regulation of the control devices. At night the storage system automatically provides power for the light source. The storage system has sufficient capacity to compensate for the seasonal variations in the length of day and night. The unit is suitable for setting into paving slabs.

Description

PHOTOVOLTAIC POWERED LIGHT This invention relates to a photovoltaic powered light.

Photovoltaic powered lights are a well known technology. One form of this technology is a self contained unit which typically consists of a photovoltaic panel, a rechargeable battery and a lamp all mounted in a casing. Additionally there is usually a mechanism for turning the lamp on at dusk and off at dawn. The battery stores the electrical energy made by the photovoltaic panel during the day for use by the lamp during the following night.

Such self contained photovoltaic powered lights suffer from a number of limitations.

For example in those parts of the world where there is a seasonal variation in the amount of day light available there is often not enough day light in a short and dim winter day to power the light during a long winter night.

According to the present invention there is provided a combination of a photovoltaic panel and a rechargeable battery which has sufficient capacity to generate and store enough power in the summer to not only run the lamp in the summer nights but also to make up the deficit of power in the winter days so as to run the lamp in the longer winter nights. A number of electronic devices are used to achieve this: Devices are used to manage the flow of electricity into and out of the battery to prevent damage to the battery by for example over-charging or deep discharging or "memory" effects or other problems of the chosen type of battery. A day light level detecting device is used to control the lamp so that the lamp turns on and off at certain adjustable levels of dusk and dawn. An adjustable timing device is incorporated which prevents the lamp running for more than an adjustably predetermined length of time. This timing device can be used to turn the lamp off before the end of long nights to help conserve power.

Additionally this timing device acts as a fail safe in case the day light level detecting device gets accidentally covered by for example fallen leaves which might cause the lamp to be turned on for an excessively long period. All the devices mentioned above together with the lamp, the battery and the photovoltaic panel are housed in a casing to produce a self contained light.

The daylight level detecting device may use some form of discrete light level sensing component alternatively the level of the output of the photovoltaic panel may be used.

In one form of the invention the generating and storage capacity of the system is such that power generated in a particularly bright summer and not used in the following winter can be stored for use in later years.

In the above description the word lamp should be taken to mean one or more light emitting devices of any type or combination of types, for example light emitting diodes, filament lamps, fluorescent lamps or other continuous or intermittent devices.

The lamp or lamps might contain their own timing, triggering or control circuits.

In the above description the word battery should be taken to mean either one battery or a number of batteries connected together. The batteries could be lead acid or nickel cadmium or nickel metal hydride or other types or a combination of types to give the required charging and discharging characteristics. A storage management system might be incorporated so some batteries are used for some types of storage and other batteries for other types of storage, thus by way of example, some batteries might handle daily levels of charge and discharge while others might handle annual levels of charge and discharge.

In the above description the words photovoltaic panel should be taken to mean either one or a number of photovoltaic devices.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows in perspective, the self contained photovoltaic powered light set into, by way of example, paving slabs.

Figure 2 shows a section of the self contained photovoltaic powered light set into, by way of example, paving slabs.

Referring to the drawings the case of the light consists of a glass top 1 sealed onto an inner case 2 which is in turn removably positioned in an outer container 3.

Drain/gassing holes are provided in the bottom of the outer container. Beneath the glass top is a sealed compartment 4 which houses the lamp, the photovoltaic panel and the day light level detector. In the lower compartment 5 is a lead-acid battery. This lower compartment is not sealed so as to allow battery gassing if necessary. The various electronic components that control the charging of the battery and the running of the lamp are in either the upper or lower compartment as necessary. Seals which may be formed of silicone, rubber or similar substances are provided at various joints, some of the seals have to be cut to remove the inner case from the outer container.

In another embodiment of the invention the battery does not gas so the inner case has only one compartment which is sealed.

Claims

1. A self contained photovoltaic powered light source which has sufficient electrical storage capacity and a number of control devices to enable the light source to operate for the desired amount of time independently of short term or seasonal variations in the amount of daylight or sunlight available and which is mounted within a casing whose configuration allows through the top both the entry of daylight or sunlight and the exit of light from the internal light source.

2. A self contained photovoltaic powered light source as claimed in claim 1 wherein there is a device which limits the amount of time that the electrical storage device provides power to the light source in order to limit the consumption of stored electrical power.

3. A self contained photovoltaic powered light source as claimed in claim 1 wherein there is sufficient electrical storage capacity to store the excess electricity generated in the summer months for use during the winter months.

4. A self contained photovoltaic powered light source as claimed in claim 1 where there is sufficient photovoltaic power generating capacity to supply both the light source and the devices that control the light sources and the electrical storage system.

5. A self contained photovoltaic powered light source as claimed in claim 1 wherein there is if advantageous to the electrical storage system a device which prevents the electrical storage system from being overcharged.

6. A self contained photovoltaic powered light source as claimed in claim 1 wherein there is if advantageous to the electrical storage system a device which prevents the electrical storage system from discharging to such a level that it is damaged.

7. A self contained photovoltaic powered light source as claimed in claim 1 wherein there is a device that turns the light source on when the level of daylight or sunlight falls below a predetermined level if the other control devices allow this.

8. A self contained photovoltaic powered light source as claimed in claim 1 wherein there is a device that turns the light source off when the level of daylight or sunlight rises above a predetermined level.

9. A self contained photovoltaic powered light source as claimed in claim 1 wherein there is a device which prevents the stored electrical power from wastefully discharging back through the photovoltaic system or other components when the photovoltaic system is not generating sufficient energy to charge the electrical storage device.

1 0.A self contained photovoltaic powered light source as herein described and illustrated in the accompanying drawings.