Throughout the world, there is growing concern about the generation of electricity from conventional sources. As a result of environmental concerns that have resulted in political pressures, conventional power generation by coal, gas, hydro and nuclear power stations is falling behind demand, since no new capacity is being built. The result is that consumers are facing power shortages and increasing electricity costs.

These power shortages have created greater interest in solar powered or solar assisted devices in order to reduce or eliminate reliance on grid electricity.

Street lamps are widespread and require a large investment in electrical distribution and infrastructure. They are essential for safety and security, yet impose large capital and maintenance costs and require-substantial amounts of electrical power from over-pressed grids.

In addition, there are many locations where it would be desirable to place a lamp in order to enhance safety and visibility but where there is no electrical power available from the grid or infrastructure. Examples are remote locations in developed countries or developing areas that require lighting but lack the electrical infrastructure to permit street and safety lighting.

In order to provide effective street lighting from ambient energy sources, a lamp must be capable of providing enough light output to meet lighting requirements and satisfy regulations. The lights must ideally be capable of obtaining enough battery charge from prevailing ambient sources to remain illuminated through the hours-of darkness, with a significant battery reserve.

The street lamps must be reliable and require minimal maintenance. Preferably, they should be capable of retrofit installation on existing poles or lamp standards.

The charging apparatus should be weatherproof and not inhibited by snow or ice.

The ambient charging arrangements must provide enough energy gain to sustain lamp operation through the desired cycle. The batteries employed must have the ability to be trickle charged and discharged through many operating cycles without failure.

The components must be non-hazardous and not susceptible to environmental degradation, such as galvanic corrosion. They must present no external hazards to humans or wildlife. They must be economically viable.

There has now been devised a form of lighting which satisfies some or all of the above-mentioned and/or other requirements.

According to the invention there is provided a lighting device comprising solar energy collecting means and wind energy collecting means operably linked to electrical energy storage means; lighting means arranged to be supplied with electrical energy by the energy storage means; and control means sensitive to the ambient light level and effective to cause electrical energy to be supplied to the lighting means when the ambient light level is below a predetermined threshold.

The solar energy collecting means most preferably comprises one or more connected solar cells. These solar cells are preferably capable of producing current in both bright sunlight and overcast conditions. They should be capable of withstanding ultraviolet light and high and low temperatures without breaking down.

The wind energy collecting means preferably includes a wind turbine coupled to a direct current generator of low inertia and low friction in order to contribute additional electrical energy to the storage means. The wind turbine and its housing should be sufficiently robust not to be damaged by high wind velocities.

Power produced by the wind turbine generator in excess of that which can safely be accepted by the storage means is preferably regulated by regulating means comprising a system of diodes, opposing motors or the like so that high wind speeds and high currents do not damage the storage means.

Electrical power generated by both the solar energy collecting means and the wind energy collected means is preferably conveyed by a common busbar to the regulating means and the storage means so that the combined output of the collecting means does not exceed the capacity of the storage means to safely absorb the energy.

Electrical power generated by the solar panels must not be allowed to flow from the busbar back into the wind turbine generator when it is inactive, thus turning it into a motor. Electrical power generated by the wind turbine must not be allowed to flow through the solar panels, thus creating internal resistance. These objectives may be achieved through diodes in the regulating means.

Excess power from the wind turbine collecting means may be dissipated as heat through a resistance grid in order to clear any accumulated snow and ice.

The storage means is most preferably an electrical battery of the lead acid, nickel metal hydride or lithium ion types, which do not have charge"memory"which inhibits their effectiveness over a large number of charge and discharge cycles.

The battery is preferably of a low maintenance or maintenance-free type, and does not require topping up with electrolytes or other chemicals over the expected life span. The capacity of the battery must exceed the maximum discharge rate and duration required by the lighting means over the required lighting cycle.

The control means is preferably based on circuits disclosed in International Patent Application WO 00/54233 in which the control means is in the form of an integrated circuit containing an oscillator. When the current supplied by the energy collecting means is above a predetermined threshold the oscillator is prevented from oscillating and supply of current to the lighting means is prevented, and when the current supplied to the control means is below the predetermined threshold the lighting means is actuated.

The control means permit the regulation of the lighting means without employing photoresistors or other light sensing means that require constant current. In this way, the electrical requirements of the device are reduced, thereby increasing the viability of the lighting device dependent on ambient energy gain.

The lighting means preferably comprises a plurality of light emitting diodes (LEDs), typically having diameters in the range 6 to 25mm.

The invention preferably also reduces the electrical consumption of the lighting means by using the control circuits to cause the light emitting diodes to flash at a rate of slightly greater than 25 Hertz. The human eye perceives a flash rate higher than 25 Hertz as a steady light. The flashing is achieved by incorporating capacitors of known charge and discharge rate into the control means, so that when the control means are actuating the lighting means, the circuits are timing the duration and frequency of the currents provided to the lighting means. By this means, the electrical consumption of the lighting means is reduced, since the light emitting diodes are activated for only a fraction of the time perceived by the human eye. In this way, the ability of the ambient energy collecting means to match or exceed the energy required by the lighting means is improved.

The impression of steady light may also be enhanced by arranging the LEDs in two or'more groups which are caused to flash out-of-phase with each other.

The control means may monitor the ambient light level by sensing the output of the solar cells in the solar energy collecting means. When the output of the solar cells falls below a pre-determined value, indicating that ambient light levels have dropped to the point that it is desirable to activate the lighting means, the control circuits permit the storage means to discharge through the timing circuits to illuminate the lighting means. The light emitting diodes in the lamp then flash at a rate faster than can be perceived by the human eye and for a duration that gives the impression of a constant light source. In this way the control circuits ensure that the lighting means consumes the minimum of electricity from the storage means, consistent with the light output requirements.

The control means senses the return of output from the solar cells as light levels increase ; and prevent the discharge of the storage means to the lighting means.

In this way, the device responds to the return of daylight or the passing of dark storms or fog without recourse to timers, light sensitive diodes or central controls.

As an alternative to the control means sensing the output of the solar cells used to charge the storage means, a separate solar cell may be employed to sense the ambient light level.

The control means may incorporate a delay so that the lighting means are not activated by passing shadows, alighting birds, windblown litter etc. that may cover the solar cells for a short period.

Street lamps according to the invention may be fitted to existing poles, columns or standards that contain connections for mains electricity. The regulating means circuits may be adapted to permit connections to the mains through a battery charging device which could allow the battery to be charged if, in extreme conditions, the normal solar energy and wind energy collecting means do not provide enough power to sustain the lighting means. While not relying exclusively on ambient energy sources, such an embodiment will substantially

reduce the use and cost of mains electricity. This embodiment may have special application in northern regions where winter nights are very long.

The lighting device is preferably housed in a housing or shell, which is at least in part clear, a clear polycarbonate shell resistant to ultraviolet light. The upper surface must permit the passage of light to the solar panels. It is preferably cambered to permit rain and snow to fall off. The housing is preferably weatherproof and mechanically strong enough to withstand high winds. It is preferably aerodynamically designed to permit the wind turbine to rotate at high speeds during winds from any direction.

A number of light emitting diodes are preferably mounted on the underside, consistent with the desired lighting requirements. The light emitting diodes are preferably mounted in a secure, weatherproof panel. In one embodiment, a polycarbonate lens may be employed over the light emitting diodes to focus the light in desired patterns or for protective or aesthetic purposes.

The housing may incorporate a number of different mounting devices, to permit connection to a range of existing poles, columns or standards.

The invention will now be described in greater detail, by way of illustration only, with reference to the accompanying drawings, in which Figure 1 is a schematic side view of a lighting unit according to the invention; Figure 2 is a schematic sectional view of the lighting unit of Figure 1, showing the principal internal components; Figure 3 is a block diagram of the electronic circuitry of the unit; and Figure 4 shows the electronic circuitry in rather more detail.

Referring first to Figure 1, a lighting unit according to the invention comprises a shell 1 moulded in clear, UV-resistant polycarbonate material. The shell 1 has a universal mounting 2 adapted for fitting to an existing lamp standard (not shown) and containing electrical connections arranged to connect to the mains electrical supply connections of the standard in the manner described below.

The upper part of the shell 1 is formed with a bulbous extension 3 with air inlet vents 4. As can be seen in Figure 2, the extension 3 houses a wind-driven fan 5 which is connected to generator 6 and control units 7.

A battery 8 is also housed within the shell 1, close to the mounting 2. The battery is preferably of the nickel metal hydride type, though a sealed lead acid or lithium ion battery may have similar performance in terms of storage of electrical energy.

The control unit 7 includes an overcharge protection circuit that serves to prevent the battery 8 from becoming over-saturated with electrical energy when production of such energy exceeds its consumption. For similar reasons, the fan 5 may be connected to means for dissipating excess energy as heat or other energy.

A circuit board 9 is housed within the shelf 1 at the end of the shell 1 remote from the mounting 2. The circuit board carries solar panels 12 disposed towards the clear roof of the shell 1.

The underside of the shelf 1 is closed by a base plate 10 within which are mounted a number of light emitting diodes (LEDs) 11 of diameter 20mm. As explained below, the LEDs 11 are connected in three groups which are illuminated sequentially.

The components of the electrical circuit are shown schematically in Figure 3 and in rather greater detail in Figure 4. Referring first to the former, the array of solar panels solar 12 and the wind-driven fan 5 are connected via the overcharge

protection circuit in the control unit 7 to the battery 8. The battery 8 is thus charged whenever light is incident on the solar panels 12 and/or the fan 5 is rotated by the wind.

The battery 8 is connected to the LEDs 11 via a control circuit 13 such that the LEDs 11 are illuminated when the ambient light level is below a predetermined threshold and are switched off when the ambient light level is above that threshold. The control circuit is based on circuits of the type disclosed in International Patent Application WO 00/54233.

In the event that the solar panels 13. and wind-driven fan 5 do not operate to supply sufficient energy, the unit can be supplied by mains electricity to automatically charge the battery 8. To this end the mounting 2 contains the necessary connections for connecting the circuitry to mains supply, and the circuitry includes a transformer, bridge rectifier and relay.

The operation of the circuit will now be described in greater detail. During daylight hours the solar array 11 provides electrical current to charge the battery.

This current is passed through a diode 18 and into the overcharge protection circuit. The current is then passed to the battery 8. Similarly the wind generator current is fed into a similar diode 19 and passed to the overcharge protection module. The resulting combination of electrical current allows an increased charge rate for the battery 8.

The wind generator output is also passed through a Zener diode 21 to a coil, which may be incorporated into a similar type generator 20, allowing automatic electromagnetic speed control of the generator thus preventing damage from excessive wind speeds.

The mains electrical system used to provide the power for the standard street light is connected to a suitable relay or integrated circuit 22, which is controlled by the electrical energy level in the battery 8. If the level of energy in the battery 8 is

low, the relay 22 is actuated via a Zener diode 23 allowing mains electricity to pass into a voltage reduction system 24 and the resulting current is passed into the overcharge protection circuit. This current is then passed to the battery 8.

The voltage reduction circuit 24 may consist of a proprietary unit or a custom designed circuit consisting of a transformer and bridge rectifier.

The current from the battery 8 is passed to the control circuit 15 which consists of a number of circuits (one for controlling each array of LEDs 11). These circuits are based on those disclosed in International Patent Application WO 00/54233.

These circuits are controlled by a solar cell 17 which allows current to flow through the said control circuits only in the near absence of light. This current is passed to the array of LEDs 11 allowing illumination.

The arrays of LEDs 11 each consist of one or more high efficiency LEDs connected in parallel. The three LEDs depicted in Figure 4 represent three groups of LEDs which are caused to flash out-of-phase with each other, so as to optimise the consumption of energy by the lighting unit and to create the impression of a steady light output.