TITLE
A Control System for Controlling a Street Light
TECHNOLOGICAL FIELD
Embodiments of the present invention relate to a control system for controlling a street light. In particular, they relate to a control system for controlling a street light where the street light is powered by a photovoltaic power source.
BACKGROUND
Lights which are powered by photovoltaic power sources are known. Such lights may be connected to photovoltaic power sources which can convert incident solar power into electrical energy.
Such lights might not be suitable to provide lighting such as street lights or belisha beacons as these may require minimum light levels to be provided.
For example, UK traffic sign manufacturing standards such as BS8442 require minimum light levels to be provided. This may be problematic if insufficient power is provided by the photovoltaic power source. For example at night time and during overcast or foggy weather conditions the photovoltaic power source might not be able to generate enough power to keep the light on at the required level of brightness.
BRIEF SUMMARY
According to various, but not necessarily all, examples of the disclosure there may be provided a control system for controlling a street light, the control system comprising; at least one photovoltaic power source; storage means for storing energy from the photovoltaic power source; a light configured to receive power from the at least one photovoltaic power source and the storage means, wherein the light has an off mode and a plurality of on modes where the plurality of on modes have different brightness levels; at least one ambient light detector configured to monitor changes in the ambient light over a time interval; at least one controller configured to receive an input from the ambient light detector, and in response to the received input control the brightness level of the light by controlling the mode of the light.
In some examples the control system may be configured such that if the photovoltaic power source is generating more power than is needed by the light to maintain the brightness level power is provided from the photovoltaic power source to the storage means.
In some examples the control system may be configured such that if the photovoltaic power source is not generating enough power for the light to maintain the brightness level power is provided from the storage means to the light.
In some examples the light may comprise a light emitting diode. The light may comprise a plurality of light emitting diodes.
In some examples the light may be configured to flash on and off. In some examples the light detector may be configured to detect the ambient light during time intervals when the light has flashed off. In some examples the control system may be configured to control a belisha beacon.
In some examples the control system may be configured to be connected to street furniture.
In some examples the control system may be configured to be operable without any other power source.
According to various, but not necessarily all, examples of the disclosure there may be provided a method of controlling a street light, the method comprising; configuring a light to receive power from a photovoltaic power source and a storage means wherein the light has an off mode and a plurality of on modes where the plurality of on modes have different brightness levels; monitoring the ambient light over a time interval; controlling the brightness of the light by controlling the mode of the light in response to the monitoring of the ambient light.
BRIEF DESCRIPTION
For a better understanding of the invention, reference will now be made by way of example only to the accompanying drawings in which: Fig. 1 illustrates an example control system; and Fig. 2 illustrates an example method.
DETAILED DESCRIPTION
The Figures illustrate a control system 1 for controlling a street light, the control system 1 comprising; at least one photovoltaic power source 5; storage means 7 for storing energy from the photovoltaic power source 5; a light 9 configured to receive power from the photovoltaic power source 5 and the storage means 7, wherein the light 9 has an off mode and a plurality of on modes where the plurality of on modes have different brightness levels; at least one ambient light detector 11 configured to monitor changes in the ambient light over a time interval; at least one controller 3 configured to receive an input from the ambient light detector 11, and in response to the received input control the brightness level of the light 9 by controlling the mode of the light.
Fig. 1 schematically illustrates an example control system 1 which may be used to control a light 9 such as a street light. In some examples the light 9 could be used to illuminate streets and roads. In some examples such as a street light the light 9 may need to be turned on when the ambient light falls below a certain level but may be turned off when the ambient light is a above a certain level. In some examples the light 9 may comprise a warning light.
In some examples such as a belisha beacon or warning light the light may need to be made brighter during bright daylight. In such examples the light may be on and/or flashing all of the time but the brightness of the light may be varied as the ambient light levels vary.
It may be necessary for the street light to be operable all day. In some examples the light may require power at all times. This may be problematic if using a power source such as a photovoltaic power source 5.
The example control system 1 comprises a controller 3, a photovoltaic power source 5, storage means 7, a light 9 and an ambient light detector 11. The components of the system 1 may be provided as a single unit. The single unit may be connected to, or otherwise mounted on, street furniture such as a lamp post.
The controller 3 may comprise means for controlling the system 1. The controller 3 may be configured to send inputs to and receive inputs from the photovoltaic power source 5, the storage means 7, the light 9 and the ambient light detector 11. The controller 3 may be configured to control each of the components of the system 1.
In some examples the controller 3 may comprise one or more processors and one or more memories. The memories may be configured to store computer program instructions which may be accessed by the one or more processors to enable the one or more processors to control the system 1 or to control components of the system.
In some examples more than one controller 3 may be provided. For example, a first controller may be provided, as described above, and a second controller may also be provided. The second controller may be configured to detect the output of the photovoltaic power source 5. The second controller may be configured to detect whether it is day or night and provide an appropriate control signal to the first controller 3. In some examples the second controller could also control the level of charging of the photovoltaic power source 5.
The photovoltaic power source 5 may comprise any means which may be configured to convert solar energy into electrical power. In some examples the photovoltaic power source 5 may comprise one or more panels comprising photovoltaic semiconductors. The photovoltaic semiconductors may be configured to create an electric current from incident solar energy.
The storage means 7 may be configured to store electrical energy. The electrical energy which is stored by the storage means 7 may comprise energy obtained from the photovoltaic power source 5. In some examples the storage means 7 may comprise a battery which may be charged by the photovoltaic power source 5.
The storage means 7 may be connected to the photovoltaic power source 5 so that the electrical energy can be transferred from the photovoltaic power source 5 to the storage means 7. The storage means 7 and the photovoltaic power source 5 may be controlled by the controller 3 so that the controller can control when power is transferred from the photovoltaic power source 5 to the storage means 7.
The light 9 may comprise any means which may be configured to convert electrical energy into light. In some examples the light 9 may comprise a light emitting diode (LED). In some examples the light 9 may comprise a plurality of LEDs. The LEDs may have low power consumption. The size and number of LEDs may be selected to meet the light levels required. In some examples the LEDs may be selected to meet official light safety standards.
The light 9 may have a plurality of different operational modes. The light 9 may have an off mode in which it is turned off so that no light is generated.
When the light 9 is in the off mode the power generated by the photovoltaic power source 5 is not needed by the light 9 and so it may be provided to the storage means 7. The controller 3 may control the system 1 so that when the light 9 is in the off mode the power is provided to the storage means 7.
The operational modes of the light 9 may also comprise a plurality of on modes. Each of the on modes may have a different brightness level. This may enable the same light 9 to provide different brightness of light as is required. The controller 3 may control the brightness of light which is provided by controlling which of the operational modes of the light is selected.
The different on modes of the light 9 may require different amounts of power to generate the required brightness level. For example the brightest on mode may require more power than a duller on mode or the off mode. In such examples if the photovoltaic power source 5 is not generating enough power then the light 9 may obtain additional power from the storage means 7. This may be the case if it is night time, or during cloudy or foggy weather conditions which have low levels of solar power but still require a light to be provided.
If the photovoltaic power source 5 is generating more power than is required then the excess power may be provided to the storage means 7. This may be the case if it is day time, or during sunny weather conditions which have high levels of solar power and might not require a very bright light or do not require any additional light at all.
In some examples the light 9 may be configured to flash on and off. For example the system 1 may be configured to provide a warning light such as a belisha beacon which may be required to flash on and off. The warning light may be configured to flash on and off all of the time. In some examples the warning light may be configured to flash on and off at predefined times.
The ambient light detector 11 may comprise any means which may be configured to detect the ambient light levels around the system 1 and provide the controller 3 with an input signal indicative of the detected ambient light levels. The ambient light detector 11 may comprise one or more photosensors or other suitable means which may be configured to convert incident light to an electrical signal.
In examples where the light 9 may be configured to flash on and off the ambient light detector 11 may be synchronised with the flashing of the light 9 so that the ambient light is detected when the light 9 has flashed off. This may avoid the light generated by the light 9 from affecting the measurements obtained by the light detector 11.
Fig. 2 schematically illustrates an example method which may be implemented using the control system of Fig. 1 and as described above.
The method comprises, at block 21, configuring the light 9 to receive power from the photovoltaic power source 5 and the storage means 7. The controller 3 may control the system so that the light 9 can receive power from just the photovoltaic power source 5 or from just the storage means 7 or from a combination of the photovoltaic power source 5 and the storage means 7 as may be required.
At block 23 the ambient light detector 11 monitors the ambient light around the system 1. The ambient light detector 11 may monitor the ambient light for an extended time interval. For example the ambient light detector 11 may monitor the ambient light for a period of ten minutes. This may avoid the system responding to a temporary change in the light level such as a passing cloud or other object temporarily obstructing the incident sunlight.
At block 25 the controller 3 controls the brightness of the light 9. The controller 3 may control the brightness of the light 9 by controlling which of the plurality of on states is selected. For example if it is determined that the ambient light is very bright then the light 9 may be turned on or configured in the highest brightness setting. If it is determined that the ambient light level is low then the light 9 may be configured in a lower brightness setting.
The one or more controllers 3 may also control the power which is provided to the light 9 by the photovoltaic power source Sand the storage means 7. The one or more controllers 3 may be configured to determine how much power is being generated by the photovoltaic power source 5. If this energy is sufficient then all the power supplied to the light 9 may be provided directly from the photovoltaic power source 5. If this energy is not sufficient then additional power may be provided to the light 9 from the storage means 7.
In some instances the photovoltaic power source 5 may be generating more power than is needed by the light 9. In such instances the controller 3 may control the photovoltaic power source 5 to provide the surplus power to the storage means 7. This may be used to save the power so that it can be used at a time when the photovoltaic power source 5 is not generating sufficient power for the light 9.
The examples of the invention described above provide for a street light or a warning light such as a belisha beacon which may be used to provided the required light levels even when a photovoltaic power source 5 is not generating sufficient power. This may be achieved by storing the excess power generated by the photovoltaic power source 5 in the energy storage means 7 and then accessing the stored energy when required. This may also be achieved by controlling the brightness of the light 9 in response to the ambient light detected so that the minimum possible brightness level is provided at all time. This makes the system 1 more efficient as it reduces the amount of power used by the system.
The system 1 may be provided as a single unit. This may enable the system 1 to be added to current street furniture.
The system 1 may be configured to operate without any additional power source. This may mean that there is no requirement to connect the system 1 to a mains power supply. This may make the system 1 easier to install as it removes the need to dig up the ground to connect a street light to a power supply. This may also enable a street light to be operable with zero carbon emissions.
The blocks illustrated in the Fig. 2 may represent steps in a method and/or sections of code in a computer program. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the blocks may be varied.
Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.
Features described in the preceding description may be used in combinations other than the combinations explicitly described.
Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.
Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.
Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.
I/we claim: