WO2015051804A1

WO2015051804A1 - A solar cell system and a method of initializing and operating such system

Info

Publication number: WO2015051804A1
Application number: PCT/DK2014/050321
Authority: WO
Inventors: Victor Timm Fagerlund JACOBSEN
Original assignee: Jacobsen Victor Timm Fagerlund
Priority date: 2013-10-11
Filing date: 2014-10-08
Publication date: 2015-04-16
Also published as: EP3055625A1

Abstract

The present invention concerns a solar cell system comprising at least one solar panel comprising one or more solar cells; control means comprising data processing means; at least one chassis arranged to support the at least one solar panel and one or more drive means to adjust the position of said at least one solar panel by position data from the control means, and means for outputting energy from the at least one solar panel; wherein the control means receives geographical position data and time data from a GPS sensor to calculate the position data for the at least one solar panel.

Description

A Solar Cell System and a Method of Initializing and Operating such System

The present invention relates to a solar cell system, a method of initializing a solar cell system comprising at least one angularly adjustable solar panel and a method of operating a solar cell system comprising at least one solar panel.

WO 2010/098973 discloses a solar energy system with a tracker controller. An algorithm stored in the controller calculates the configuration for the solar energy systems based on solar movement; shade patterns generated by the surrounding structures, and measured output of the energy systems.

WO 2008/003023 discloses a solar array tracker controller having a processor connected to drive motors in a solar panel. It is programmable and includes a software program which includes an algorithm that determines the location of the sun relative to the local data input into the processor. The local input data may be provided by a GPS sensor.

A solar cell (also called a photovoltaic cell) is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect. It is a form of photoelectric cell (in that its electrical characteristics, e.g. current, voltage, or resistance, vary when light is incident upon it) which, when exposed to light, can generate and support an electric current without being attached to any external voltage source. Assemblies of photovoltaic cells are used to make solar modules which generate electrical power from sunlight. Multiple cells in an integrated group, all oriented in one plane, constitute a solar photovoltaic panel or "solar photovoltaic module", as distinguished from a "solar thermal module" or "solar hot water panel". The electrical energy generated from solar modules, referred to as solar power, is an example of solar energy. A group of connected solar modules (such as prior to installation on a pole-mounted tracker system) is called an "array".

In order to maximize the electrical power generated by the solar cells, tracking systems, such as the examples from WO 2010/098973 and WO 2008/003023, are provided to follow the sun to attempt to achieve the best disposure of the solar cells relative to the sun light. These systems must be mounted with great accuracy and the tracking must be adjusted very precisely in order to achieve a reasonable tracking of the sun. Although this is achieved to a certain degree, it is an object of the present invention to provide an improved solar cell system.

This object is achieved by a solar cell system comprising at least one solar panel comprising one or more solar cells; control means comprising data processing means; at least one chassis arranged to support the at least one solar panel and one or more drive means to adjust the position of said at least one solar panel by position data from the control means, and means for outputting energy from the at least one solar panel; wherein the control means receives geographical position data and time data from a GPS sensor to calculate the position data for the at least one solar panel.

In the present disclosure, the term a solar panel includes either one single solar cell or an assembly of a number of connected solar cells.

By a solar cell system according to the invention there is provided a very precise tracking system which allows the system to "self-calibrate" after the system has been installed at a given site. The precision may be achieved by using the time signal which is received together with the GPS signal whereby an algorithm can accurately calculate the sun position relative to the location of the solar cell system. Moreover, the system according to the present invention may also adjust and optimize the solar panel position relative to the sun in relation to different factors, including maximum electrical power output but also maximising the service life for the solar panels, etc. Accordingly, the invention also provides the following second and third aspects:

According to a second aspect of the invention, there is provided a method of initializing a solar cell system comprising at least one angularly adjustable solar panel, comprising the steps of: - determining the geographical position and actual time after having placed the solar cell system at a given location; - calculating an optimized angular position of the at least one solar panel; and then - activating one or more drive means for positioning said at least one solar panel in said optimized position. According to a third aspect of the invention, there is provided a method of operating a solar cell system comprising at least one solar panel, said method comprising the steps of: - receiving GPS data; - calculating the position of the sun relative to the solar cell system; - determining the vertical and horizontal angular position of the sun; - adjusting the position of the at least one solar panel by determining the optimized position of one or more drive means connected to at least one solar panel.

According to an advantageous embodiment of the invention, the drive means comprises means for adjusting lateral and/or vertical position of at least one solar panel, and/or means for adjusting angular tilt of said at least one solar panel in at least one dimension, preferably two directions, such as adjusting the angular position around a vertical and a horizontal axis.

Preferably, the control means comprises means for determining an optimized position of the at least one solar panel, and means for outputting a position data signal corresponding to the optimized position. Furthermore, the data processing means determines the optimized position based on one or more of the following data: actual time; geographical position of the system; GPS data; inclination; geographical orientation of the system (i.e. a compass direction). Hereby, the system may be automatically supplied with the necessary data to initiate itself and adjust the solar panels to an optimized position.

The control means may preferably also be provided with data input and output ports, such as USB ports or the like, for providing data communication facilities with the system.

The data processing means may further be provided with one or more of data concerning: weather; status of solar panels; restrictions on output from the solar panels; relative position of the solar panels; and/or lifetime of one or more of the solar panels. This allows for optimizing the life time of the components of the solar cell system and thereby making the solar cell system more cost-effective. The solar cells need cooling in order to perform at their best. However, there is a maximum load which the solar cells should be exposed to. By a system according to this embodiment of the invention it is realised that by measuring the load on the cells the control means can also ensure that the solar cells do not exceed their load limit, e.g. by "back-tracking" or switching the system to a stand-by mode or adjusting the solar panel to a shadow- mode.

In order to make the system more efficient and minimizing the power consumption, the system may advantageously comprise different modes including an active mode, a stand-by mode, a low power mode and/or positioning/initialization mode.

The system according to the invention advantageously comprises one or more detectors and/or receivers taken from the group of: a GPS receiver; a light sensor; an inclination sensor, such as a gyroscope; a geographical orientation sensor, such as an electronic compass. This allows for providing a system suitable for mobile installations as e.g. a geographical orientation sensor makes the system able to directionally position itself and therefore does not require a reference orientation at the point of installation. Likewise, a gyroscope or similar inclination sensor would allow for an optimised use of a system according to the invention on mobile installations in an undulated terrain or at sea.

By the invention it is also realised that selected parts may be operated only under predetermined conditions. These predetermined conditions may be to ensure a minimum and/or maximum output energy and/or prolongation of the service life time of individual components, for instance that the solar panels are adjusted to achieve an optimized lifetime of said solar panels.

In an embodiment of the invention, the solar cell system is a stand-alone system, preferably having a plurality of solar panels operated together. The solar cell system may advantageously be provided with an omni-directional solar panel unit for providing initial electrically power for the start-up of the solar cell system. Such an auxiliary power source can ensure that the system can be started up in circumstances where the main solar panels cannot generate the necessary power, e.g. if the weather is cloudy or other weather conditions have caused the system to stop with the solar panels in a position where there is no exposure to the sun.

The solar cell system may be part of a larger energy structure comprising one or more solar cell systems, such as an array of solar cell systems. In particular, the solar cell system may form at least a part of a building structure. The invention will in the following be described in more detail with reference to the accompanying drawings, in which:

Fig. 1 is a schematic diagram of a solar cell control system according to an embodiment of the invention;

Fig. 2 is a flow chart for the start-up initialization of a solar cell system according to the invention;

Fig. 3 is a flow chart illustrating the function loop when running the solar cell system according to the invention;

Fig. 4 is a schematic perspective view of a solar cell system according to an embodiment of the invention;

Fig. 5 is a schematic perspective view of a solar cell system according to a second embodiment of the invention;

Fig. 6 is a schematic side view of this second embodiment;

Fig. 7 is a schematic side view of a third embodiment of a solar cell system according to the invention;

Fig. 8 is a schematic perspective view of a fourth embodiment of a solar cell system according to the invention; and

Fig. 9 is a diagram showing the power output of solar cell systems in different configurations over a year.

An embodiment of the invention is shown in the schematic diagrams in figures 1 to 3. With particular reference to fig. 1 , the system is provided as a module 10. The module 10 generally operates autonomously. A display of LED (not shown) may be provided for communication of status and the like. The module comprises a GPS (Global

Positioning System) receiver 12 and a RISC microcontroller 14 for system control and conversion of GPS signals for positioning of the sun.

The module further comprises motor position control 15 and drivers for controlling two DC motors 20.

The GPS (Global Positioning System) receiver

The purpose of the GPS receiver 12 is to collect information about the geographical position of the system and the actual time. Advantageously, this data is received in a standard NMEA protocol. Preferably, the GPS receiver 12 also supports other protocols, such as WAAS and EGNOS, and has a sensitivity of 148dBm or less and is adapted to receive 66 channels simultaneously. In the example referred to in figs. 1-3, there is received a NMEA standard sentence RMC (Recommended Minimum Configuration). This sentence contains:

- longitude and latitude with a precision of 0,00001 decimal degrees, and

- time in seconds, minutes, hours, date, month and year. The GPS receiver 12 in the example referred to in figs. 1-3 communicates with the controller 14 via USART 9600 Baud. There is also sent a PPS (puls-per-second) signal to the controller 14.

The Controller

In the example the controller is a microchip 16 bit RISC processor with 32 kbyte PROM, USART interface PWM module, and some A/D and D/A converters. The controller 14 operates on 64 MHz in active mode, and can change into a low-power mode via sleep instruction, to a lower working frequency of 32 kHz. The controller is the central unit for the solar cell system control and manages all the operations. The controller may optionally be provided with data communication ports, such as one or more USB ports for input and/or output of data.

In operation, there is received a NMEA signal from the GPS receiver 12 via USART for validation. After calculation of the position, the positioning is performed via four PWM channels to the drivers of the motors 20 and there is received feedback either via A/D conversion of a potentiometer feedback or there is a count from one or more optical or read sensors. This receipt of GPS data, validation, calculation and/or positioning is signalled on a display area (not shown) on the module, for instance by flashing one or more (preferably three) LEDs.

The motor position control

The motor position control 15 is a sub-unit of the controller 14. The motor control can be configured according to two functional needs. As an example of the motor position control, there may be mounted two L2722 op-amp. drivers that can power and drive the motors 20 up to 12V DC 1000mA, in a discrete H-bro; or there can be mounted two MC33666 Motorola MOSFET H-bro circuits which makes it possible to supply the motors 20 with up to 36V DC 4000mA. It is realised that the MC33666 configuration furthermore makes it possible to receive feedback on the power consumption, detection of over load as well as thermal off switch.

Program functions With reference to fig. 2, the system according to the invention is self-initialising or self- calibrating. This function may operate in the following manner:

After the main power for the solar cell system is switched on, a normal reset functions and port initialisations are carried out. The module signalises via a display (such as an LED display) that the reset, initialisation of ports, initialisation of motor driver units and the activation of the GPS module is done.

Thereafter, the controller awaits the first PPS signal from the GPS receiver for an indication that the GPS receiver has received a signal. This status may be displayed via the LEDs or the like. Then the system awaits the first RMC sentence. All subsequent RMC sentences are validated for invalid parameters and when a predetermined number RMC sentences have been received and approved in an unbroken sequence (for instance 20 RMC sentences), the RMC sentences are sorted after latitude and longitude and a further average calculation on position is made based on 5 to 15 of the RMC sentences. The most deviating positions are then disregarded whereby there is ensured a very high degree of accuracy in the position. The position is then "locked" as a variable and afterwards the system can disregard the position signals of the GPS receiver. Depending on the configuration the two motors, such as horizontal and vertical motor, are driven to the reference position calculated by the controller.

With reference to fig. 3, the function loop is described. When the system is initialised or calibrated, the solar cell system is ready for operation. This involves that the system executes the function loop. The loop is run at a predetermined interval, such as every one second. This involves calculating the position of the sun based on the RMC sentence. The time (seconds, minutes and hours) is converted into decimal days and the distance to "Julia Day" (i.e. 1 January 2000, 12:00:00) is calculated in decimal days. This distance is compared with the normal equation of time. Included in the calculations are data about the elliptical orbit of the earth and the variations in the rotational speed of the earth. This is converted from the geographical position into celestial coordinates and the distance to the meridian and equator is determined in degrees and decimal degrees. The horizontal and vertical position of the sun is then calculated in celestial degrees and decimal degrees and the deviations and converted into geographical directions. For this calculation the algorithm includes information concerning the diameter of the earth versus the distance to the sun and the final elevation angle (90-zenith angle) and the orientation in degrees where North is 0° if the system is used on the northern hemisphere and 0° is south when the system is used on the southern hemisphere.

It is then determined if the sun is visible over the horizon and if not (which means it is night) it is determined how long time there is to sunrise and the system is then turned into low power mode until the sunrise occurs. The two resulting angles are converted to a reference for either the analogue comparator if a potentiometer feedback is used, or the number of pulses from 0 (zero) if tacho is used.

The motors are turned into position and a new RMC sentence is awaited whereafter the function loop is repeated.

In figure 4, a schematic perspective illustration of a solar cell system with a solar panel according to an embodiment of the invention is shown. A solar panel 46 comprising an array of solar cells are arranged on a planar surface. The panel 46 is angularly positionable able around a horizontal axis 44 and a vertical axis 42. The panel 46 is pivotably mounted on a frame 48 via a semi-circular sub-frame 47 and the frame 48 is rotatably mounted on a console 40.

In the console 40 the controller 14 may be accommodated and the motors 20 may be suitably positioned for angular positioning of the solar panel 46 about the horizontal axis 44 and the vertical axis 42, respectively. The controller may receive GPS signals from a separate GPS receiver 12 as shown in fig. 4, but the console could alternatively also accommodate the GPS receiver 12.

With reference to figures 5 and 6, a second embodiment of the solar cell system is shown in which the solar panel 46 is pivotally arranged in a frame 48. This frame 48 is them mounted onto a console 40, which has a rotatable top part 40a and a fixed lower part 40b. The frame 48 is mounted to the top part 40a which can be rotated by a drive means 47, such as an electrical motor and a gearing arrangement. As shown in fig. 6, an actuator 49 may be provided between the lower portion of the frame 48 and the lower side of the solar panel 46. By activating this linear actuator 49, the solar panel 46 may be tilted relative to the frame 48.

An example of a more simple embodiment of the invention is shown in fig. 7. Fig. 7 is a schematic side view of a Venetian blind for an external building cover, such as a window or the like. Each of the lamellae 52 are covered with a solar panel on the exterior side. The lamellae 52 are pivotably mounted on a frame 50 and pivotably connected to a push-/pull rod 56. This rod 56 may be raised or lowered by a console 54, which accommodates the controller 14 of the solar cell system according to the invention. In this embodiment, only one motor is used and the sun tracking is only done with respect to one angular position.

In figure 8 another embodiment of the invention is shown. In figure 8 the solar cell system includes a solar panel 46, which is pivotably mounted in a frame 48 which in turn is mounted on a console 40, such as shown in fig. 4. The controller 14 and the GPS receiver 12 may be provided externally or internally in the console 40. According to this embodiment of fig. 8, the solar cell system is advantageously provided with an omni-directional solar panel unit 60 for providing initial electrically power for the start-up of the solar cell system. Such an auxiliary power source 60 can ensure that the system can be started up in circumstances where the main solar panels 46 cannot generate the necessary power, e.g. if the weather is cloudy or other weather conditions have caused the system to stop with the solar panels in a position where there is no exposure to the sun. As indicated in fig. 1 , this omni-directional unit 60 may also include a wind sensor 61 in order to provide the controller module 10 with wind data on the site where the solar cell system is positioned and is to be activated. Other additional units may also be provided as indicated by dotted lines in figures 1 and 2. Additional data, e.g. from an electrical compass 16 and/or a gyroscope 18, may facilitate the "self-calibration" or start-up of the solar cell system on a new and to the system unknown location. Such additional data allows for providing a system suitable for mobile installations as a geographical orientation sensor, such as a compass 16, makes the system able to directionally position itself automatically and therefore does not require an external reference orientation at the point of installation. Likewise, a gyroscope or similar inclination sensor would allow for an optimised use of a system according to the invention on mobile installations in an undulated terrain or even at sea.

Other additional units may also be provided, such as a light sensor 17 for providing data concerning the sun light level where the solar cell system is positioned. A shadow function 19 could also be provided to ensure that there is not one or more of the solar panels covering each other by a shadow. Furthermore, the controller module 10 could also be provided with a unit for service lift optimization of the components in the solar cell system.

By the invention, it is realised that other external sensor units may be provided for supplying the system with other kinds of additional data. Examples could be a wind sensor or a light sensor.

By the invention, it is realised that the solar cell system may have a variety of utilities. As a stand-alone unit, the solar cell system can be provided for fixed installations as well as for mobile installations. It is also realised that a number of solar panels each individually controlled may also be provided in accordance with the invention.

In figure 9 is shown a graphical comparison of the output between different solar panel systems over a year on the northern hemisphere. The output is expressed in kwh per square meter per day on the vertical axis and the time of year along the horizontal axis starting and ending with June 21.

Three solar panel systems are compared, and the curves represent the three electrical power output over a year, where the curve marked "F2 is a fixed solar panel system, the curve marked "A" is an adjusted solar panel system and the curve marked "T" is a sun tracking solar panel system. It is clear from the power outputs of the three systems that the constant tracking of the sun where it is ensured that the solar cells are constantly positioned at their most optimised position relative to the sun provides a significantly higher output in particular during the summer months.

Claims

1. A solar cell system comprising:

at least one solar panel comprising one or more solar cells;

control means comprising data processing means;

at least one chassis arranged to support the at least one solar panel and one or more drive means to adjust the position of said at least one solar panel by position data from the control means, and

means for outputting energy from the at least one solar panel; wherein

the control means receives geographical position data and time data from a GPS sensor to calculate the position data for the at least one solar panel.

2. A solar cell system according to claim 1 , wherein the drive means comprises means for adjusting lateral and/or vertical position of at least one solar panel, and/or means for adjusting angular tilt of said at least one solar panel in at least one dimension, preferably two directions, such as adjusting the angular position around a vertical and a horizontal axis.

3. A solar cell system according to any of the proceeding claims, wherein the control means comprises means for determining an optimized position of the at least one solar panel, and means for outputting a position data signal corresponding to the optimized position.

4. A solar cell system according to any of the preceding claims, wherein the data processing means determines the optimized position based on one or more of the following data:

actual time;

geographical position of the system;

- GPS data;

- inclination;

geographical orientation of the system.

5. A solar cell system according to claim 4, wherein the data processing means further is provided with one or more of data concerning:

- weather; status of solar panels;

restrictions on output from the solar panels;

relative position of the solar panels; and/or

lifetime of one or more of the solar panels.

6. A solar cell system according to any of the proceeding claims, said system comprising different modes including an active mode, a stand-by mode, a low power mode and/or positioning/initialization mode.

7. A solar cell system according to any of the proceeding claims, said system comprising one or more detectors and/or receivers taken from the group of:

a GPS receiver;

a light sensor;

an inclination sensor, such as a gyroscope;

- a geographical orientation sensor, such as an electronic compass.

8. A solar cell system according to any of the proceeding claims, wherein selected parts are operated only under predetermined conditions.

9. A solar cell system according to claim 8, wherein the predetermined conditions ensure a minimum and/or maximum output energy.

10. A solar cell system according to any of the proceeding claims, wherein the solar panels are adjusted to achieve an optimized lifetime of said solar panels.

1 1. A solar cell system according to any of the proceeding claims, wherein the solar cell system is a stand-alone system, preferably having a plurality of solar panels operated together.

12. A solar cell system according to any of the proceeding claims, wherein the solar cell system is part of a larger energy structure comprising one or more solar cell systems, such as an array of solar cell systems according to any of claims 1-1 1.

13. A solar cell system according to any of the proceeding claims, wherein the solar cell system forms at least a part of a building structure.

14. A solar cell system according to any of the preceding claims, wherein the solar cell system is provided with an omni-directional solar panel unit for providing initial electrically power for the start-up of the solar cell system.

15. A method of initializing a solar cell system comprising at least one angularly adjustable solar panel, comprising the steps of:

- determining the geographical position and actual time after having placed the solar cell system at a given location;

- calculating an optimized angular position of the at least one solar panel; and then - activating one or more drive means for positioning said at least one solar panel in said optimized position.

16. A method according to claim 15, whereby the method of initializing of the solar cell system is electrically powered by the electrical output of an omni-directional solar panel unit.

17. A method according to claim 15 or 16, whereby additional position-related data, such as directional input from a compass and/or inclination data from a gyroscope, are also provided when calculating the optimized angular position of the at least one solar panel.

18. A method of operating a solar cell system comprising at least one solar panel, said method comprising the steps of:

- receiving GPS data;

- calculating the position of the sun relative to the solar cell system;

- determining the vertical and horizontal angular position of the sun;

- adjusting the position of the at least one solar panel by determining the optimized position of one or more drive means connected to at least one solar panel.

19. A method according to claim 18, whereby the solar cell system has been initialized by performing a method according to any of claims 15 to 17.

20. A method according to any of claims 15 to 19, whereby the solar cell system is a system according to any of the claims 1 to 14.