MULTIPLE ENERGY HARVESTER TO POWER STANDALONE ELECTRICAL APPLIANCES
Field of Invention
 This invention relates to a method of and an apparatus for the harnessing of multiple renewable energy sources to produce electricity to power up standalone appliances.
 Low power renewable energy sources are ideal to power up standalone off-grid appliances such as street light, telecommunications stations, rural household, outdoor signboard and a series of other applications. Using only one source of renewable energy is usually limited to its daily as well as seasonal fluctuation and may not be able to provide adequate consistent power supply.
 One of the most common standalone applications is the street light. Street lights are essential to provide illumination and safety for road, park, square and public places in general. Illumination of different levels is required to meet different purposes. Tremendous number of street lights is used to light up roads, highways, and pavements that consume huge amount of power. Long power cables are laid to supply electricity to these street lights. Not withstanding the cost of these power cables, energy loss in the cable over long distance is enormous too. Many areas that require street lighting remained unlit because of the high initial capital cost and the running electricity bill. It is a challenge to find solutions to reduce the initial capital cost and the running cost of street lights. The most common alternative to conventional street light powered by the main utility grid is the photovoltaic (PV) street light or commonly known as solar street light. Solar street light uses photovoltaic panel to convert solar energy into electricity to charge a battery storage which in turn power the lamp. Besides envi¬ ronmental benefit, Solar street light has many other advantages such as reducing in¬ stallation cost due to the elimination of transmission cable. It has almost no running cost since it does not consume electricity from the utility grid. However, PV street lights are generally limited to low power lighting as the cost of PV is still rather high.
 Powering a street light or other standalone appliances such as signboard from a single renewable energy source by using photovoltaic alone is not sufficiently economical to light up high power lamps. Other renewable energy sources must be explored in order to make up the inadequacy. A survey of literatures shows that the common solution is to attach conventional wind turbine to the pole of the street light to supplement photovoltaic. Conventional horizontal axis wind turbines usually do not work well in non-laminar flow wind pattern which is typical in the environment where the street light is installed. Harnessing other sources of power for a standalone ap¬ plication besides photovoltaic and wind is almost non-existence.
 Hybrid renewable energy systems are not uncommon especially combining wind
power and solar photovoltaic. The two energy sources are usually managed by an in¬ telligent charge controller that regulate the two electric inputs to charge a common storage and supply to an appliance.
 JP2003042052, US4200904 and GB2344382 are inventions related to the use of both photovoltaic and wind to power street lights.
 JP2003042052 discloses a street light device comprises a vertical-axis wind power generator, and a solar panel both supplying power to a power accumulator to light up a lamp. The solar panel is disposed so that the wind hitting the solar panel is guided to blades of the vertical-axis wind turbine.
 US4200904 discloses a street light device comprises a conventional horizontal-axis wind turbine and solar panel with other control necessary to charge a battery and to power up a lamp. It is important to note that horizontal-wind turbine is not effective with non-laminar wind at low velocity.
 GB2344382 describes a street light with a vertical-axis wind turbine that is mounted around the pole of the street light to supply power to the lamps. Auxiliary power sources such as solar panel can be added on too.
 US 4359870, GB748700, US2003217551 and WO0042320 are inventions related to power generation by using solar thermal stack effect.
Description of Drawings
[1 1] Figure 1 An example of a multiple energy harvester for street lighting application.
 Figure 2 Plan view of a rectangle shaped solar thermal collection and air heating module.
 Figure 3 Side view of another possible solar thermal collection and air heating module design.
 Figure 4 Plan view of the round shape solar thermal collection and air heating module.
 Figure 5 An example of a multiple energy harvester for a telecommunication tower.
 Figure 6 An exemplary wind rotor to convert erratic wind to updraft.
 Figure 7 Block diagram of the electrical charging and storage system.
Summary of Invention
 According to an objective of the present invention, multiple sources of energy including solar induced stack effect, solar photovoltaic and wind energy are harnessed to produce electricity. The multiple energy sources are combined effectively to minimize system components, reduce cost and improve reliability. In the present invention, the solar induced stack effect and the wind power external to the pole interact to produce electricity either singly or jointly by the air movement in the pole to rotate the concentric wind generator. The wind rotor does not have its own generator but instead share with the stack effect through the concentric wind generator in the pole.
 An objective of the invention uses stack effect also known as buoyancy effect
through collecting solar thermal energy to heat up air to rise through a supporting pole to rotate a concentric wind generator housed within the pole. The rising hot air is con¬ centrated in the pole to create a strong updraft for turning the concentric wind generator and hence produces electricity. The hot air is produced by the solar thermal collectors mounted at the lower part nearer to the base of the supporting pole. When air is heated by the solar thermal collectors it become lighter and pass through the entrance aperture into the pole to produce an updraft. Electricity produced by the concentric wind generator is used to charge a battery and power up a load.
 Another objective of the invention is to harness energy from surrounding free flowing wind by a wind rotor. The purpose of the wind rotor is to convert erratic or laminar wind flow to an updraft in the pole. Vertical axis wind rotors such as the Savonius rotor are preferred as they are able to work under erratic wind and at low wind speed. The wind rotors have blades appropriately shaped such that their rotation will produce an updraft and draw air from the pole on which it is mounted. The updraft in the pole will turn the concentric wind generator to produce electricity. The updraft induced by the wind rotor can either work singly or enhance the rising hot air.
[21 ] Yet another objective of the invention is to harness solar energy by photovoltaic to convert radiation to electricity. The electricity produced by the photovoltaic panel and the concentric wind generator is regulated by a charge controller to charge a battery and supply power to the appliances.
Description of a specific embodiment
 The present invention is a method of and an apparatus for harnessing multiple energy sources from nature and convert them to electricity to power electrical lamps 10. The invention comprises a largely vertical supporting hollow pole 50, solar thermal collection and air heating module 30, concentric wind turbine generator 55, external wind rotor 60, photovoltaic panel 25, charge controller 19, battery 17 and the appliances 10 such as lamps.
 The solar thermal collection and air heating module 30 further comprises of solar radiation absorbing surfaces 31 and transparent covers 52. Air passages 80 are formed between the solar radiation absorbing surfaces 31 and the transparent covers 52. The solar radiation absorbing surfaces 31 are made of metal sheet with highly effective coating for absorbing radiation while minimizing emission. The solar radiation will be largely absorbed and the surfaces 31 will be heated up rapidly. The air surrounding the solar radiation absorbing surfaces 31 will be heated up due to thermal convection effect. The heated air is then guided by the transparent covers 52 and the solar radiation absorbing surfaces 31 and channel into the opening aperture 53 on the pole 50 to create an upward air movement 66 in the pole 50. Cold air then enters the solar thermal collection and air heating module 30 from the outside to replace the heated air that rose through the pole 50. Air heated by the underside of the solar radiation absorption surfaces 31 can also pass through the array of holes 35 to get to the opening
53 on the pole 50.
 Hot air is lighter in density than that of cold air and hence rises. As the temperature of the air gets higher, its density will be> lower and thus rises faster. The amount of upward air movement through the pole is proportional to the difference in air temperature between the air entrance and the exit of the pole. The upward air movement 66 is also dependent on the size of the solar collection and air heating module 31. The larger the collection surface 31 , more air will be heated up and hence increases the volume of air flow 66.
 Many different shapes and sizes of the solar collection and air heating module 30 are possible depending on the location where the invention will be used. For example, street light installed on the road side can take the form of rectangle shape that spreads out parallel to the road causing no obstruction to the flow of traffic. In the case of a park light or street light for open area, the solar collection and air heating module 30 can be circular spreading around the pole 50 resembling an umbrella.
 Mounted within the pole 50 is a concentric wind generator 55 that looks like a typical ventilation fan but function in the reverse manner. It is mounted in alignment with the axis of the pole 50 to reduce unnecessary pressure loss. The concentric wind generator 55 is turned by the air movement 66 through the pole 50 to produce electricity. The amount of electricity generated is determined largely on the kinetic energy of the air movement. The upward moving air will exit the pole 50 from the top. The electricity generated is regulated by a charge controller 19 to charge a battery 17 or supply to the appliances 10. Other source of renewable energy such as the pho¬ tovoltaic 25 is also sent to the charge controller 19 to charge the battery 17.
 A vertical axis wind rotor 60 is mounted on the top of the pole 50 and is largely aligned with the vertical axis of the pole 50. The vertical axis wind rotor 60 is without an attached generator and it is used to convert wind to air movement 66 in the pole 50 and is capable of operating in erratic wind condition. The blades 61 of the vertical axis wind rotor 60 are shaped such that when it rotates it will create a suction force to draw air from the pole 50. It is important to shape the blades such that the suction is one di¬ rectional from the pole to the atmosphere and not from the atmosphere into the pole 50. The suction provided by the vertical axis wind rotor 60 enhances the upward air movement 66 through the pole 50 and turns the concentric wind generator 55 to generate electricity. Since the vertical axis wind rotor 60 does not have its own generator attached, its starting wind speed is much lower and its conversion efficiency from erratic wind to upward air movement through the pole 50 is reasonably high.
 It is evident up to this point that the solar thermal induced updraft 66 through the pole 50 and that from the vertical axis wind rotor 60 both share a single generator which is the concentric wind generator 55 mounted within the pole 50 instead of two individual generators resulting in cost saving and reduced system complexity. It is also important to note that by having only one generator means that the charge controller 19
is less complicated than having two separate generators.
 During the day with reasonable radiation, the solar thermal collection and air heating module 31 will function as it is designed to generate air movement 66 through the pole 50. If there is reasonable wind happening at the same time, then the vertical axis wind rotor 60 will help to generate more air flow through the pole 50 which in turn increases the electricity produced. During the night without solar radiation, the hot air movement will be gradually reduced and finally stopped. Similarly, photovoltaic 25 will not produce electricity below certain solar insolation. However, the vertical axis wind rotor 60 will continue to function whenever there are reasonable wind movements no matter day or night.
 An example of the vertical axis wind rotor 60 is a modified Savonius rotor with at least two blades and preferably three blades 61. The blades 61 are shaped with ap¬ propriate aerodynamic curvature and slanted to the direction where suction 66 effect will be induced. The principle of converting wind to suction is the reverse to that of the conventional blower where spinning blades create centrifugal force to draw air from its core to the peripheral. These blowers are commonly found in air conditioner fan coil units. The characteristic of the said vertical axis wind rotor 60 is such that it will only rotate in the same direction 65 regardless of the wind direction. This particular char¬ acteristic is important as the air is to be drawn upward 66 from the pole 50 and not the reverse.
 The pole 50 of the said invention is largely vertical and hollow inside and preferably smooth on its wall to reduce frictional loss in the air movement 66. It is also preferably slow in absorbing heat so that it will not heat up quickly especially towards the upper part of the pole. A light color paint or insulation can be used to reduce heat gain by the pole 50. A tall pole height is advantageous to the present invention as both wind power and stack effect will be increased with the increase in height.
 The potential applications of the invention are very wide ranging from street light, signboards, telecommunication relay stations, and others with inherently tall structures. For examples, the pole 50 can be easily mounted together a telecommunication pylon or tower such that the structural requirements of the pole is reduced and the con¬ struction made simpler. Yet another example is to construct the invention on the sunny side of a tall building. The solar radiation absorption and air heating module 30 is attached to the building wall and may be used as a roof for various other purposes.