WO2014009541A2

WO2014009541A2 - Solar panel array

Info

Publication number: WO2014009541A2
Application number: PCT/EP2013/064816
Authority: WO
Inventors: Andrew WATERFIELD
Original assignee: Hiptonics Limited
Priority date: 2012-07-13
Filing date: 2013-07-12
Publication date: 2014-01-16
Also published as: GB2503944A; GB2503964A; GB201212559D0; WO2014009541A3

Abstract

A solar panel system comprising a chassis which can turn on a circular track (ground or flat roof mounted) which itself supports a tilting frame holding solar panels. Light sensors and an anemometer provide information, via a control unit to electric motors which twist and tilt the frames so that the panels point at the brightest part of the sky, and to a safe position in high winds. At night the panel system moves to face east in preparation for the next dawn. The system makes maximum use of the available light so that a given area of solar panels is able to generate more electricity each day than a fixed array. It is of particular value in rural areas where the small local substations cannot accept more than a limited wattage, but can accept it all day.

Description

SOLAR PANEL ARRAY

The present invention relates to solar panels that generate electricity. The electricity can be for domestic use and/or for export to a grid system. Solar panels are usually fixedly located on roofs of buildings such as on flat roofs, pitched roofs or on stands in open spaces.

The best direction in which to point a fixed solar panel array to generate the greatest electrical energy depends upon the geographic location of the panel. For example, in Britain the optimum position is a south facing array tilted at between 35 and 40 degrees from the horizontal. This compromise position attempts to maximise electrical energy generation (a function of power and time) during the daylight hours of the year. However, it is only at midday in late March and late September that even this configuration will actually be pointed directly at the sun which is required to generate maximum power. Every day for most of the time it will be pointed too far to the left or right of the sun for maximum power, except at midday. Furthermore, in winter it will be too horizontal, and in summer too vertical to be pointed at the sun for maximum power. In late June it will be in shadow for the first two and a half hours after dawn, and the last two and a half hours before sunset. Similar issues will apply elsewhere in the world. The commonest size of a domestic solar panel array is less than 27 square metres in area, capable of producing a maximum of four kilowatts, if lucky enough to be pointing directly at the sun when the sun is shining in a clear sky. When the sun is shining, but the panels are in shadow, the panels can generate less than 100 watts. When the sky is cloudy, light arrives from the sky from all directions, but very little is reflected off the ground, so it is likely that the maximum power in cloudy conditions will be generated by solar panels facing vertically upwards. By way of example in the south of England, the sun does not shine for more than about 1200 hours of the 4380 hours the sun is above the horizon each year. Therefore, for 70% of daylight hours, more electricity would be generated by a solar panel facing vertically upwards than one on a pitched roof.

The panels of the present invention are useful for all weather conditions and throughout the hours of daylight, thereby generating considerably more electrical energy than a fixed array. The invention is applicable to arrays of any size although in particular it provides a nominal four kilowatt mobile solar panel array capable of increased power generation. The invention therefore provides a solar panel array that can always point at the sun when it is shining and can point towards the brightest part of the sky when it is cloudy. This enables the generation of more electrical energy, almost all day, almost every day, than is generated by a fixed array, without exceeding a certain power level determined by the size of the array.

The concept of a mobile array is known, using an equatorially mounted system similar to that used by astronomical telescopes, so that by gradually rotating the array once every 24 hours on a fixed axis parallel to the axis between the north and south poles of the earth, it can remain pointed at a fixed point in the sky during the day and night. Because the sun appears to change its position throughout the year, over the equator at midday in March and September, and over the tropics of Cancer and Capricorn in June and December respectively, another mechanism is then required to tilt the array at right angles to that fixed "polar" axis, either gradually or episodically, throughout the year, to take account of the height of the sun above the horizon with the varying seasons.

An equatorially mounted solar array will always point to where the sun is, but clouds may mean that that direction is not necessarily the brightest part of the sky, nor can it take account of severe weather conditions which might risk the integrity of the device and the safety of others.

WO 201 1/043757 describes a two axis ground based solar tracking system for large scale solar collectors that tracks the sun's movement through the sky regardless of the season or time of day. The system is also said to be resistant to the effects of the wind. The system comprises a plurality of solar detectors mounted on a rotatable carrier which can be rotated to direct the detectors towards the sun and in which the angle of the detectors can be adjusted so that the detection face is orthogonal to the rays of the sun. The system that controls the movement of the entire tracking system is a memory provided with solar position data combined with data obtained from a GPS receiver. The present invention provides a solar panel system which generates electricity from light impacting the panel system and can alter its position in at least two axes automatically and the position of the panel is controlled by detecting the source of the light and optionally also by weather sensors. The panel system may be a single panel or an array of a plurality of panels. Where it is a plurality of panels it is preferred that the panels be mounted in a single tiltable frame and in a side by side configuration so they are parallel with the plane of the frame and one panel cannot prevent light impacting on another panel. The panel system is mounted on a circular carriage on which it can be rotated and the carriage does not have a central axis mounting to allow free tilt of the panel. The panel system is preferably mounted within a frame which can move on the carriage and is provided with wheels that can move on the circular track. It is preferred that the wheels are provided above and below the carriage to enhance the stability of the system. The panel system is also mounted in a manner that it can be tilted in the vertical plane for example by tilting the frame within which it is mounted and to place the edge of the panel close to the ground. This can be useful to reduce the impact of winds on the panel system. Additionally it allows the panel system to be rotated and titled to be in the optimum position for exposure to the maximum incidence of light and hence generate the maximum amount of power.

The panel system is provided with a light detector system conveniently mounted on the frame that contains the solar panel or panels. The light detector will determine the brightest part of the sky at any particular moment and it will send a signal that is interpreted to adjust the position of the panel to be facing the brightest part of the sky and thus generating the maximum amount of power. In a preferred embodiment the system is provided with two light detectors one of which is mounted to determine the inclination of the brightest part of the sky and the other to determine the horizontal direction of the brightest part of the sky. In this way the signals from the light detectors can be used to rotate the solar panel on its frame to face the direction of the brightest part of the sky and tilt the panel so it is orthogonal to the incidence of the radiation from the brightest part of the sky.

In a preferred embodiment the detector system comprises two sensors mounted on the tilting panel, towards the middle. In order that one sensor does not cast a shadow on the other, they are preferably a few centimetres apart. Conveniently, two small sensors such as small (about 2.5 by 2.5 cms) solar panels may be placed together edge on at right angles to each other to form a single sensor. The sensor is mounted in a fixed position on the array and therefore moves with it. One sensor is mounted with its edge parallel with the axis on which the panel tilts, and information from this sensor controls the tilt of the array. The other sensor is mounted at right angles to this, such that the edge is always perpendicular to the axis of the tilting panel, and controls the motor driving the chassis on the track. The control unit measures the input from these small panels working in pairs, and adjusts the position of the main array so that the power from each side of each of the two sensors is the same. The array is rotated and tilted respectively towards the panel of each pair which is producing the most power. When the power from each of the sensors is substantially the same, the light is arriving from the brightest part of the sky at the same angle on each (45 degrees) side of each sensor, and therefore the array is facing that same part of the sky, maximising output.

The system may be provided with a control system that receives signals from the light detector(s) (or sensors) and drives two motors as appropriate to rotate the system on the carriage and also to tilt the panel(s), typically by tilting the frame containing the panel, to face the brightest part of the sky.

In a further embodiment the panel system of the present invention is provided with safety mechanisms. For example, it may be provided with an anemometer that determines the prevailing wind speed and sends a signal to the control system which automatically returns the panel system to a horizontal position if the wind exceeds a certain predetermined speed that is considered to pose the risk of upturning the panel system. The control system can return the panel to its optimum position once the wind speed drops below the critical level. The panel system may also be provided with means for clearing snow, rain, hail or the like from the receiving surface of the panel and again this may be automatically operated by providing sensors which determine the presence of the snow, rain or hail. The snow, rain or hail may be wiped away or allowed to fall under gravity by tilting the array of panel(s). The control system can automatically tilt the panel system towards the vertical position when there is insufficient light either due to darkness or the panel being covered for instance by snow.

In a further embodiment the control system can reposition the solar array at nightfall so that it is automatically facing the rising sun at daybreak. This may be accomplished by means of the light detectors previously described or by the provision of a clock within the control system. In a further embodiment the system generates power for export to a grid system and it can involve an inverter if the grid system is based on alternating current. The cessation of the operation of the inverter can also be used to provide a signal that power generation from the panel system has fallen below a certain level and the array should be tilted vertically ready for the sunrise the following day.

The panel system of the present invention may be transportable and the carriage may be provided with wheels to enable ready transport. The system of the present invention may be powered by mains electricity or by a battery system. It is preferred to use a battery system and preferably one that is charged by the electricity generated by the solar panel or panels. The use of such a battery system allows the panel system of the present invention to be used in different locations and enhances transportability. The system may be provided with means that allow the choice of being powered by battery or mains electricity. The present invention is therefore an array which can tilt and rotate automatically, so that at all times during the day, when it is safe to do so, it is pointing at the brightest part of the sky. When the sun is shining, it will be pointing directly at the sun. When the sun sets, it can automatically rotate to face east to be ready for the next dawn. When the wind is too strong for it to be pointed towards the brightest part of the sky, or face east at night ready for the next dawn, it can tilt to a horizontal position to minimise the risk of damage to the structure or danger to others. It can revert to the default position of facing east at night, or the brightest part of the sky when light, when the strong wind has abated. If covered with snow during the day it would automatically tilt to the vertical, believing it to be night time, tipping the snow off. The invention is illustrated but in no way limited by reference to the accompanying figures in which

Figure 1 shows the device viewed from directly above. Figure 2 shows the device face on to a vertically tilted frame carrying the solar panels. Figure 3 is end of view of the titled frame carrying the solar panels. Figure 4 is a schematic diagram of the control system.

Figure 5 shows a single sensor comprising two light sensitive surfaces at right angles to each other.

In Figures 2 and 3 the numerals designate the same features as are designated in Figure 1 .

Figure 1 shows solar panel array (1 ) within a chassis frame (2) is mounted on a circular monorail track (3) which conveniently is about 9 metres in diameter. The track may be just above ground level supported by struts attached horizontally to the inside of the track (not shown). The track allows wheels (not shown) to run on the upper and lower edges of the track. The array can be sited on fairly level ground on a concrete ring sunk into the ground, or on the fairly flat roof of a building. A motor (4) is provided for tilting the array. For example, a four kilowatt array of sixteen, 1 metre by 1 .6 metres, 250 watt panels is mounted on a flat frame about four metres high and 6.4 metres wide. Two small directional light receptor units (10) and (1 1 ) are mounted at right angles to each other on the solar panels, one mounted to determine the inclination of the brightest part of the sky, and one the horizontal direction of the brightest part of the sky.

Figure 2 shows that the frame (2) can tilt on a horizontal axis through the middle of the frame. A geared 12 volt motor (4) attached to the chassis, under automatic control, tilts the frame to the position determined by the control unit. The chassis holding the horizontal axle consists of two vertical triangular constructs (5) and (6), one on each side of the horizontal axis of the frame. One of these constructs carries the geared motor (4) controlling the tilt of the frame. It also carries, at a level above the top of vertically tilted frame, an anemometer (7).

Figure 3 shows the array with the panels (1 ) tilted towards the light. The two triangular constructs are linked together at the bottom with two horizontal struts, thus forming an oblong. This oblong is mounted on the circular track at its corners (8) and (9) with wheels above and below the track in a similar way to the attachment of a roller-coaster to its track, so that it cannot lift off, and is therefore able to withstand reasonable cross winds. A geared 12 volt motor (not shown) is attached to one of the wheels so that the chassis can be rotated on the circular track (3) to a position determined by the control unit.

In the embodiment illustrated the 12 volt supply to the movement motors comes from a 12 volt "car" battery, which is charged during daylight hours by a trickle charger attached to the inverter supplying the grid from the panel array with 240 volts at 50 Hz. This battery could also be used to power an electric fence if it is necessary to keep farm animals or pets away from an array mounted on open ground.

Figure 4 shows a small control unit (12) that controls the two 12 volt motors with input from the two light receptors (10) and (1 1 ) monitoring the direction of the brightest part of the sky, the anemometer (7) and information about the output from the inverter, so that it knows when it is too dark to export power to the 240 volt grid, and too windy to be other than horizontal.

Figure 5 shows one of the two light receptors comprising two light sensitive sections mounted at right angles to each other to provide a single detector (10) and (1 1 ). Electrical connections for the power generated by the panels are similar to those for a fixed array, currently used for domestic installations.

The system of the present invention can have widespread use. It will be of particular interest in rural areas where it is rather more likely that a flat area of ground without significant shading from surrounding structures can be found. It is somewhat less likely to upset the local planning office in rural areas. The system of the invention can be installed on buildings such as agricultural buildings with low pitched roofs. Any excess electricity generated can be fed into a national grid system, the Feed in Tariff may be at reduced rates for larger arrays, in general it is more cost effective and therefore more profitable if the array is close to the maximum size for a particular band of tariff. However, the properties with land around them suitable a use of a system of the present invention are also those most likely to be served by a small substation, incapable of accepting to the grid more than a limited wattage. The system of the present invention is therefore particularly useful in such circumstances as it can be limited to a maximum output of four kilowatts.

The significant increase in electricity generation with the device of the present invention will more than offset the cost of the system, maximising income from the Feed in Tariff, and contribute greatly to the efforts to realise increasing the proportion of sustainable electricity generation. It could become the standard system to replace fixed arrays on the ground, or on flat roofs. As it will usually be ground or flat roof mounted, it will be easier to install, thereby reducing the capital outlay involved.

Claims

1 . A solar panel system for the generation of electricity from light which is mounted upon a single circular track on wheels, wherein there is no central axis support for the circular track.

2. A solar panel system according to claim 1 in which the wheels are both above and below the track.

3. A solar panel according to claim 1 or claim 2, provided with an anemometer and a wind direction sensor which provides information whereby the panel automatically adopts a safe position in adverse weather conditions.

4. A solar panel according to claim 3 that will adopt a horizontal position when the local wind speed reaches a critical predetermined level.

5. A solar panel according to previous claims that will adopt a vertical position when there is insufficient light available to the panel to generate useful power.

6. A solar panel according to any of the preceding claims which requires no external sources of information regarding weather in the area or the position of the sun.

7. A solar panel system comprising a plurality of panels capable of generating up to 4 kilowatts of electrical power wherein the panels are edge to edge and all in the same plane.

8. A solar panel system comprising two pairs of sensors one pair orientated to provide information regarding the horizontal direction of the brightest part of the sky to the control of the wheels on the circular track, and the other pair orientated to provide information regarding the inclination of the brightest part of the sky to the control of the tilting of the panel on its horizontal axis.

9. A solar panel according to claim 8 in which the faces of each sensor are at right angles to each other.

10. A solar panel according to claim 8 or claim 9 in which the sensors consist of two faces comprising small solar panels whereby each face generates electricity whereby the output of one face may be integrated with the output of the other face to provide net output from the two positive terminals when one face is generating more power than the other.

1 1 . A solar panel according to claim 10 wherein when there is net power generated by the two faces, the array is commanded to move in the direction that reduces the net power output.

12. A solar panel according to claim 1 1 in which the array is commanded to move until the net output is zero

13. A solar panel system according to any of claims 8 to 12 wherein the sensors are mounted near to the centre of the array, or at the edges of the array and each sensor is split so that one face faces forwards at 45 degrees to the plane of the array and the other faces at right angles to the face of the other, also facing forwards at 45 degrees to the plane of the array.

14. A solar panel system according to any of claims 8 to 13 including a feedback mechanism from the sensors to provide commands to the panel to move until the panel is optimally orientated for maximum power output.

15. A solar panel system according to any of claims 8 to 14 where the sensors provide real time information as the panel moves, or the orientation for maximum output moves, so that the device may be orientated to the optimum position at all times by electrical feedback mechanism that requires no computer calculations.

16. A solar panel according to any of the preceding claims which is moved by motors powered by a battery system.

17. A solar panel system according to claim 16 wherein the battery is charged by the solar array when it is generating power.

18. The use of a solar panel according to any of the preceding claims for supplying power to electrical fencing to maintain security against grazing animals.