WO2012050485A1

WO2012050485A1 - Solar tracking sensor

Info

Publication number: WO2012050485A1
Application number: PCT/SE2010/000241
Authority: WO
Inventors: Andreas Johansson
Original assignee: Global Sun Engineering Sweden Ab
Priority date: 2010-10-12
Filing date: 2010-10-12
Publication date: 2012-04-19

Abstract

The present invention relates to a solar tracking sensor that comprises a number of solar cells (201; 301) on a solar panel. The invention also relates to a solar concentrator that comprises at least one solar panel with solar tracking sensor in accordance with the present invention. The solar tracking sensor is distinguished in that it orients a solar panel/solar concentrator in such a manner that it makes use of the sunlight in an optimal manner and as a consequence supplies maximum electrical power instead of directing the solar panel/solar concentrator toward the sun in accordance with a predetermined orientation. In distinction from earlier solar tracking sensors based on electrical power, no power loss has to take place, on account of a lower theoretical light intensity, the solar panel/solar concentrator can be re-oriented inside the solar tracking sensor in the production of electricity.

Description

SOLAR TRACKING SENSOR

Technical field of the invention

The present invention refers to a solar tracking sensor that comprises a number of solar cells on a solar panel. The invention also refers to a solar concentrator that comprises at least one solar tracking sensor on a solar panel in

accordance with the present invention.

State of the art

Solar concentrators comprise reflecting surfaces that concentrate the incident sunlight to solar panels in the solar concentrator, which panels in their turn comprise solar cells. These known solar concentrators also comprise a solar tracking function. For instance the solar tracking function uses a number of light sensors used to orient the solar concentrator toward the sun. The solar tracking function is in principle always encumbered by a certain error, i.e., the area of concentrated sunlight that the reflecting surfaces generate is not perfectly positioned relative to the solar panel. In order to compensate for this the reflecting surfaces generate an area with concentrated sunlight that is greater than the solar panel, i.e., the reflecting areas are "over-dimensioned" relative to the solar panel.

Solar cells can be coupled in parallel or in series. The series coupling is to be preferred since such an

arrangement provides lower currents in the system and higher voltage. Low currents create less losses in the lines and high voltage simplifies the transformation from direct current to alternating current.

If all solar cells in a solar panel are connected in series, each solar cell will produce the same power as the solar cell that produces the least. This brings it about that if a solar cell does not obtain full illumination, it will throttle the production of electricity in all solar cells.

A solar tracking sensor is known from US-7109461 that uses solar cells in a solar concentrator where a parabola concentrates sunlight on solar cells and as a consequence converts sunlight to electricity. This solar concentrator is roughly directed toward the sun with the aid of a known solar tracking arrangement. The solar concentrator also comprises a sensor in which the generated electrical power is measured on groups of solar cells and the latter are compared in pairs in order to direct the solar concentrator in such a manner that the maximum power is obtained. If a difference is detected in the generation of power between pairs, a reorientation of the solar concentrator takes place until the same generation of power is again attained in both groups of solar cells. This brings about a better solar tracking in which the maximum electrical power directs the orientation on the solar

concentrator instead of the light sensor that is fastened on the solar concentrator.

A solar panel is known from patent application number

0802552-0 with a combination of edge cells coupled in parallel and centre cells coupled in series. The connecting together of solar cells for which a patent is requested brings it about that an obliquely distributed light intensity in the image areas of the solar panel does not have a negative effect on the withdrawal of power from the solar panel.

Objects and features of the invention

A primary object of the present invention is to indicate a solar tracking sensor that uses solar cells on the edges of a solar panel, whereby the solar cells included in the solar panel are coupled together in such a manner that an obliquely distributed light intensity in the edge area of the solar panel does not have a negative effect on the withdrawal of power from the solar panel as the result of deficiencies in the functioning of the solar tracker. This is a considerable improvement compared with earlier technology in which a drop in electrical power had to take place before a compensation in the solar tracking takes place.

Therefore, the area of concentrated sunlight that the reflecting areas generate does not have to be "over- dimensioned" relative to the area of the solar panel. The above-described solar tracking sensor can be completed by a solar tracking arrangement of a known type for rough directing of the solar concentrator toward the sun for a more effective solar tracking.

At least the primary object of the present invention is realized by arrangements that have been given the features indicated in the following independent claims. Preferred embodiments of the invention are defined in the dependent claims .

Brief description of the drawings

Preferred embodiments of solar panels in accordance with the present invention will be described below with reference made to attached drawings, in which:

Fig. A shows a known solar panel with solar cells coupled in series ;

Fig. B-E show four groupings of solar cells in a known solar panel .

Fig. F shows the solar panel according to Fig. A, in which the continuous frame symbolises the area with full light intensity falling on the solar panel.

Fig. G shows the solar panel according to Fig. A; however, the area with full light intensity is shifted relative to the position according to Fig. F. Fig. 1 shows a solar panel with edge cells coupled in

parallel, where an area with full light intensity does not cover the entire solar panel; and Fig. 2 shows a solar panel with edge cells coupled in

parallel, where an area with full light intensity does not cover the entire solar panel and is shifted relative to the position according to Fig. 1. Fig. 3 shows a first embodiment of the solar tracking system in accordance with the present invention.

Fig. 4 shows a second embodiment of the solar tracking

system in accordance with the present invention.

Detailed description of preferred embodiments of the invention

Fig. 1 shows a solar panel comprising series-coupled solar cells J. The electrical power in the upper grouping of solar cells K in Fig. B is compared with the electrical power in the lower grouping of solar cells L in Fig. C. The solar

concentrator is then re-oriented so that the same power is obtained from both groupings.

The electrical power in the left grouping of solar cells M in Fig. D is compared with the electrical power in the right grouping of solar cells N in Fig. E. The solar concentrator is then re-oriented so that the same power is obtained from both groupings.

Fig. F shows a solar panel according to Fig. A in which the upper group of solar cells K according to Fig. B and the lower group of solar cells L according to Fig. C are visible. The continuous frame Rl symbolizes the area on which the incident light has full intensity.

Fig. G shows how the frame R2 is shifted relative to the frame Rl according to Fig. F. Only 20% of the area of the upper edge cells is located inside the frame R2. This brings it about that the upper edge cells produce only 20% of

electrical power compared with the fully illuminated cells inside the frame R2. Since all cells are series-coupled, therefore, all cells will only produce 20% of their maximum electrical power.

Fig. 1 and 2 show how the special parallel coupling of edge cells 3 functions when the area with full light intensity does not cover all solar cells on the solar panel. The area with the light intensity is symbolized by the continuous frame R3, respectively R4. Fig. 1 shows two edge cells 3 coupled in parallel, whereby half the area of these two edge cells 3 is located inside the continuous frame R3. Since these two edge cells 3 are coupled in parallel, they can be considered as one solar cell with an area that is the sum of the two half areas, i.e., one solar cell/edge cell with an area that corresponds to the area of a centre cell 1.

Fig. 2 shows how the frame R4 is shifted relative to the position of frame R3 according to Fig. 1. Only 20% of the left edge cell 3 is located inside the frame R4 whereas 80% of the right edge cell 3 is located inside the frame R4. Due to the fact that the edge cells 3 are coupled in parallel, the sum of the areas of edge cells 3 that are located inside the frame R4 are considered as one solar cell/edge cell with an area corresponding to one centre cell 1.

Since the edge cells 3 coupled in parallel have a combined area that corresponds to the area of the series- coupled centre cells 1, both the illumination instances shown in Fig. 1 and 2 for the solar panel bring it about that both the edge cells 3 and the centre cells 1 produce full power.

Fig. 3 shows two edge cells 201 and the electrical power in the left edge cell is compared with the electrical power in the right edge cell. The solar concentrator is then reoriented so that the same power is obtained from both

groupings. No power loss happens as long as the solar

tracking error remains within a certain margin of error that is controled by the cell width of the edge cells. The edge strip housing the edge cells 3 has the width Bl and there is the following relationship 0<B1<0 , 1B/H between the width Bl of the edge strip and width B or height H of the solar panel.

Fig. 4 shows two parallel-coupled groups of mutually series-coupled edge cells consisting of four edge cells each 301. By measuring the power on these groups and compensating the solar tracking so that the power becomes the same for both of the edge cell groups, a power-controled solar tracking is obtained without any power loss as long as the solar tracking error remains within a certain margin of error that is

controlled by the cell width of the edge cells. The edge strip that houses the edge cells 3 has the width Bl and there is the following relationship 0<B1<0, 1B/H between the width Bl of the edge strip and width B or height H of the solar panel.

Conceivable modifications of the invention

Every pair of parallel-coupled edge cells can have any arbitrary form. The only requirement is that the illuminated partial area of two parallel-coupled edge cells corresponds to the illuminated area of one centre cell. This means that different lengths in the side direction and the height

direction of the edge cells can be used for varying the margin of error in the apparatus. E.g., there can be cells that are long in the side direction and narrow in the height direction if it is desired to have a greater margin in the side

direction. This also applies to groups of edge cells coupled in parallel in pairs.

Claims

Claim

1. A solar tracking system for controlling and orienting a solar concentrator relative to the sun,

c h a r a c t e r i z e d in that the solar concentrator comprises a solar panel that comprises a number of solar cells, which solar cells (3) are located along the

circumference of the solar panel and are called edge cells, one or several edge cells on an edge part are coupled in parallel with one or several edge cells on the opposite edge part, the parallel-coupled groups of edge cells and centre cells (1) located inside the edge cells are series-coupled, edge cells as well as centre cells are used to generate electricity, and the edge cells are also used to generate control signals for solar tracking in at least one direction