WO2009060390A1

WO2009060390A1 - Solar heating and tracking system

Info

Publication number: WO2009060390A1
Application number: PCT/IB2008/054607
Authority: WO
Inventors: Wilhelm Frederich Haupt
Original assignee: Wilhelm Frederich Haupt
Priority date: 2007-11-06
Filing date: 2008-11-05
Publication date: 2009-05-14

Abstract

A solar fluid heating system (10) comprises an assembly (11) comprising a trough shaped parabolic reflector (12) for solar energy. A heating vessel (14) for the fluid is rigidly connected to the reflector (12) to be located in a focal region of the reflector (12). The vessel (14) defines an inlet (18) for the fluid and an outlet (20) for the fluid therefrom. A first pivot mechanism (22) is located in a center of mass region of the assembly (11) between the reflector (12) and the vessel (14). The heating vessel (14) is housed in a translucent jacket (13) of a heat insulating material. The jacket (13) comprises a translucent tube (15) and an airgap (17) between the vessel (14) and the tube (15).

Description

Solar heating and tracking system INTRODUCTION AND BACKGROUND

This invention relates to a solar, fluid heating system and to associated apparatus.

Solar water heating systems for domestic use are known. The known systems are either too sophisticated and hence too expensive or not effective enough.

OBJECT OF THE INVENTION

Accordingly, it is an object of the present invention to provide a solar fluid heating system and associated apparatus with which the applicant believes the aforementioned disadvantages may at least be alleviated, or which the applicant believes would provide an alternative to the known systems.

SUMMARY OF THE tNVENTlON

According to the invention there is provided a solar fluid heating system comprising an assembly comprising a reflector for solar energy; a heating vessel for the fluid rigidly connected to the reflector to be located in a focal region of the reflector, the vessel defining an inlet for the fluid and an outlet for the fluid therefrom; and a first pivot mechanism located between the reflector and the vessel.

The reflector may be trough shaped having a main axis and the vessel may comprise an elongate conduit having a main axis extending parallel to the main axis of the reflector, the conduit may define the inlet towards one end thereof and the outlet towards an opposite end thereof.

The first pivot mechanism may provide a first pivot axis in a center of mass region of the assembly and extending parallel to the main axis of the trough and the main axis of the conduit.

The system may comprise a support structure for supporting the assembly on a surface, such as a roof-top. The support structure may comprise a second pivot mechanism to provide a second pivot axis for the assembly extending perpendicularly to the first pivot axis.

The support structure may comprise a first riser member mountable on the surface and connectable to the first pivot mechanism and a spaced second riser member mountable on the surface and connectable to the first pivot mechanism. The first and second risers may extend substantially parallel to one another, the first member may be connectable to the first pivot mechanism towards the first end of the conduit and the second riser member may be connectable to the first pivot mechanism towards the second end of the conduit.

The first riser member may be hollow and may serve as a feed pipe to the conduit and may be connected to the inlet by a first branch pipe. The second riser member may be hollow and may serve as a drain-pipe from the conduit and may be connected to the outlet by a second branch pipe.

The conduit may be housed in a jacket of a translucent and heat insulating material. The jacket may comprise a tube of a translucent material and an annular air gap between the conduit and the tube.

The system may comprise drive means, such as at least one electric motor, to drive the assembly to pivot about the first and/or second axes, in use, to follow and/or track the sun. The drive means may be energized by a rechargeable battery and the battery may be connected to a suitable power supply, such as solar panel. A battery charger may be connected between the power supply and the battery. The drive means may comprise a first electric motor for driving the assembly to pivot about the first axis and a second electric motor for driving the assembly to pivot about the second axis.

The drive means may be controlled by a signal source direction finder as hereinafter defined and/or described.

The system may comprise a main reservoir having an outlet and an inlet, the main reservoir and the heating vessel being connectable in a circuit with the outlet of the main reservoir being connectable to the inlet of the heating vessel and the outlet of the heating vessel being connectable to the inlet of the main reservoir.

The main reservoir may comprise a hot water geyser.

The system may comprise a water exchange pump connected in the circuit and configured to be controlled by a controller, a first temperature sensor may be located in or otherwise be associated with the main reservoir and a second temperature sensor may be located in or otherwise be associated with the heating vessel and may be connected to the controller, the controller being configured to cause the pump to pump fluid from the heating vessel to the main reservoir, when a temperature sensed by the second sensor is higher than a temperature sensed by the first sensor.

The invention further includes within its scope a signal source direction finder. The signal may be an audio, electromagnetic or other signal.

The signal may also be a photo signal, such as that emitted by the sun, and the direction finder may then be employed to find the direction of the sun and to track movement of the sun.

The direction finder may comprise at least first and second detectors for the signal and a shield for partially obscuring the detectors from the signal to be monitored.

The first and second detectors may be connected to a processor for processing first and second output signals from the respective detectors and utilizing a differential signal to provide an output signal.

The solar signal source direction finder may comprise a detector arrangement comprising a substrate; any number of photodetectors located in respective sections on the substrate defined by mutually perpendicular walls extending perpendicularly from the substrate; and a roof on the walls extending parallel to the substrate. In a preferred embodiment of this aspect of the invention, a solar signal source direction finder comprises a detector arrangement comprising a substrate; first, second, third and fourth photodetectors located in respective quadrants on the substrate defined by first and second mutually perpendicular walls extending perpendicularly from the substrate; and a roof on the walls extending parallel to the substrate.

A further photodetector may be provided on a surface of the roof facing away from the substrate.

The photodetectors may be connected to the processor and the processor in use may execute a program to generate the output signal for controlling at least a first motor to drive the aforementioned assembly about the first pivot axis to follow the sun as it moves from east to west, and preferably also a second motor to drive the aforementioned assembly about the second pivot axis to follow north- south deviations of the sun.

Also included within the scope of the present invention is a method of finding the direction of a source of impinging energy and a method of tracking movement of the source, as herein defined and/or described. BRIEF DESCRIPTION OF THE ACCOMPANYING DIAGRAMS

The invention will now further be described, by way of example only, with reference to the accompanying diagrams wherein: figure 1 is a diagrammatic perspective view of part of a solar, fluid heating system according to the invention in the form of solar water heating system; figure 2 is a block diagram of part of the system in figure 1 connected into a conventional domestic water heating circuit; figure 3 is a diagrammatic perspective view of a sensor arrangement of a signal source direction finder apparatus in the form of a solar signal direction finder and which may form part of the system in figure 1 or figure 2; and figure 4 is a block diagram of the signal source direction finder apparatus.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION A solar fluid heating system according to the invention in the form of a solar water heating system is generally designated by the reference numeral 10 in figure 1 . The system 10 comprises an assembly 1 1 comprising a parabolic, trough shaped reflector 12 having a mirrσr-like polished operative surface, to focus impinging soiar energy in a focus region, and a heating vessel 14 in the form of an elongate conduit located in the focus region and which is rigidly connected to the reflector by spacing struts 16. Towards a first end thereof, the conduit defines an inlet 18 for water and towards a second end thereof, the conduit defines an outlet 20 for water therefrom. The conduit may have any suitable cross sectional profile, such as circular, square or rectangular. The conduit may have a matt black outer finish and a heat reflecting finish on the inside thereof. The conduit 14 may be housed in a jacket 1 3 of a translucent, preferably transparent, but heat insulating material. The jacket 13 may comprise a tube 15 of polycarbonate or a material being sold under the trade name "plexiglas". An annular air-gap 17 may be provided between the tube 1 5 and the conduit 14. The assembly further comprises a first pivot mechanism 22 to enable movement of the assembly 1 1 about a first pivot axis 24, which is parallel to a main axis of the reflector and a main axis of the conduit.

The system 10 further comprises a support structure 26 for mounting the assembly on a surface, such as a roof of a building, for example. The support structure comprises a first tubular riser 28, which is mountabie on the roof and connected to the pivot mechanism 22 towards the first end of the conduit. The support further comprises a second spaced tubular riser 30, which is mountabie on the roof and connected to the pivot mechanism 22 towards the second end of the conduit. The first riser 28 serves as a feed pipe to the conduit 14 and is connected by a first branch pipe 32 to the inlet 18. The second riser 30 serves as a drain-pipe from the conduit and is connected to the outlet 20 by a second branch pipe 34.

The system 10 may further comprise a second pivot mechanism (not shown) enabling the assembly 1 1 to pivot about a second pivot axis, which is perpendicular to the first pivot axis 24.

Cold water entering via feed pipe 28 and inlet 18 is heated by the focussed solar energy in the conduit 14 and caused to be drained through the outlet 20 and a drain-pipe 30.

Referring to figure 2, the system 10 may be connected into a water heating circuit 40, such as a domestic water heating circuit, comprising a main reservoir in the form of a geyser 42. An outlet 44 for cold water from the geyser is connected via riser 28 and first branch pipe 32 to the inlet 18 of the conduit 14. The outlet 20 of the conduit is connected via second branch pipe 34 and drain-pipe 30 to an inlet 46 of the geyser. These connections form a circular flow path providing for water flowing anti-clockwise in figure 2. A pump 48 is provided anywhere in the circular flow path between outlet 44 and inlet 46. The pump is controlled by a controller 50, which is connected to a first temperature sensor 52 in the geyser and a second temperature sensor 54 in the conduit 14. The controller 50 is configured to cause water exchange between the geyser and the conduit. Typically, when the temperature at sensor 54 is higher than the temperature at sensor 52, the pump is caused to pump water from the conduit 14 to the geyser 42.

The system 10 preferably comprises apparatus for finding the source of an impinging signal, in this case the sun, and for tracking the sun as it moves from east to west during a day and also seasonally deviates in northern and southerly directions.

Referring to figures 3 and 4, the apparatus 56 comprises a sensor arrangement 58 comprising a substrate 60. As shown in figure 3, the substrate is divided into four quadrants by first and second opaque mutually perpendicular walls 62 and 64. On top of the walls there is provided an opaque roof 66. The walls and roof form a partial shield for impinging light on first, second, third and fourth photodetectors 68.1 to 68.4 located in the first to fourth quadrants respectively. A fifth υn-obscured photodetector 68,5 is mounted on the roof 66 on a face thereof facing away from the substrate. The first to fifth photodetectors are connected to a controller 70 and the controller comprises a processor executing a program configured to control a first motor 72 to drive the arrangement 1 1 to pivot about the first pivot axis 24, to follow the sun as it moves from east to west and a second motor 74 to drive the arrangement 1 1 about the second pivot axis, to track seasonal north-south deviations of the sun. The photodetectors are electronically biased to have their outputs all vary alike, but to be sufficiently sensitive to variations in illumination.

In use, the sensor arrangement 58 is mounted on the aforementioned pivotal arrangement 1 1 , shown in figure 1 , so that photodetector 68.1 serves as a north-east detector, photodetector 68.2 serves as a southeast detector, photodetector 68.3 serves as a south-west detector and photodetector 68.4 serves as a north-west detector. Photodetectors 68.1 and 68.2 hence are an eastern pair of detectors and photodetectors 68.3 and 68.4, are a western pair of detectors. Should a perpendicular axis of the reflector 1 2 and hence a center axis of the detector arrangement 58 be pointing at the centre of the sun, all four detectors would be obscured from the sun and will only detect reflected light from the sides and light refracted around the edges of the roof. The intensity of this incident light will be considerably less than that of direct sunlight. Should the perpendicular axis of the parabola not be pointing at the centre of the sun, one or more detectors will become even more obscured, while the others will be subjected to direct incident sunlight. To correct this situation, it is necessary to activate motor 72 to pivot the assembly 1 1 in a westerly rotational direction (with critical damping) if the aggregate incident energy detected by the western detector pair is higher than that of the eastern pair and vice versa. The other motor 74 is activated to pivot the assembly 1 1 in a northerly rotational direction if the aggregate incident energy detected by the northern detector pair is higher than that of the southern pair and vice versa.

If the output of the south-western detector matches that of the northeastern one (within system parameter bounds) and the output of the south-eastern detector similarly matches that of the north-eastern one, the detectors are in equilibrium. If the sun is at that moment in fact visible from the assembly 1 1 and not obscured by cloud cover, nightfall or other phenomena, the assembly 1 1 should be trained substantially on the sun. To verify the presence of the sun, the fifth 68.5 and un-obscured photodetector is added.

The aforementioned program executing on the processor is configured on wake up (reset) of the microprocessor, to determine the extremes of the movement of the assembly 1 1 in both directions, detecting and recording it and setting future movement limits. While doing so, the processor also determines the visibility and likely position of the sun in the east-west direction by, at numerous points along movement of the assembly, calculating the difference in returned signal between the un- obscured photodetector 68.5 and the aggregate of the obscured detectors. The position where this difference is both large enough {determined by prior experimentation with the detector/bias configuration) and at a maximum, is the position from where the sun can be acquired using the method of moving towards the obscured detector with the highest output. The controller positions the motor 72 at that position and starts an acquiring algorithm. If no such position can be determined with the prevailing sun conditions, the process is repeated at regular (say quarter hourly) intervals, until it is possible to acquire the sun. Once the sun is acquired, the microprocessor utilizes a prediction lookup table to predict the east-west position of the sun relative to the assembly 1 1 for the next twenty-four hours, using the basic fact that, if the sun completes more or less one revolution per day, so should the assembly 1 1 . The microprocessor may devise its own notion of real time from the position where it first acquires the sun relative to the assembly's limits of movement. The assembly then re-acquires the sun every, say, thirty seconds, the microprocessor recording data relating to the position and stores the data in an interpolation lookup-table in its memory accordingly. If the sun is not visible, the assembly follows the sun as predicted by position data in the last updated lookup table.

The lookup table is not only maintained for a twenty-four hour cycle, but a resultant most refined version of a day's table is compared with the equivalent one of the previous day to determine the ruling daily variation, quite independently of the cause of the deviation (which will be the seasonal deviations and other aberrations). The determined daily variation and the determined timing error because of imprecise electronics are applied to the aforementioned look-up prediction table every morning and refined throughout the day. When the assembly reaches the daily pivot extreme, the motor 72 causes the assembly to return to a position from where to resume.

Claims

1 . A solar fluid heating system comprising an assembly comprising a reflector for solar energy; a heating vessel for the fluid rigidly connected to the reflector to be located in a focal region of the reflector, the vessel defining an inlet for the fluid and an outlet for the fluid therefrom; and a first pivot mechanism located between the reflector and the vessel.

2. A system as claimed in claim 1 wherein the reflector is trough shaped having a main axis, the vessel comprises an elongate conduit having a main axis extending parallel to the main axis of the reflector, and wherein the conduit defines the inlet towards one end thereof and the outlet towards an opposite end thereof.

3. A system as claimed in any one of claims 1 and 2 wherein the first pivot mechanism provides a first pivot axis in a center of mass region of the assembly and extending parallel to the main axis of the trough and the main axis of the conduit.

4. A system as claimed in any one of claims 1 to 3 comprising a support structure for supporting the assembly on a surface.

5. A system as claimed in claim 4 wherein the support structure comprises a second pivot mechanism, to provide a second pivot axis for the assembly extending perpendicularly to the first pivot axis.

6. A system as claimed in claim 4 or claim 5 wherein the support structure comprises a first riser member moυntable on the surface and connectable to the first pivot mechanism and a spaced second riser member mountable on the surface and connectable to the first pivot mechanism.

7. A system as claimed in claim 6 wherein the first and second risers extend substantially parallel to one another, the first riser member being connectable to the first pivot mechanism towards the first end of the conduit and the second riser member being connectable to the first pivot mechanism towards the second end of the conduit.

8. A system as claimed in claim 6 or claim 7 wherein the first riser member is hoflow, serves as a feed pipe to the conduit and is connected to the inlet by a first branch pipe.

9. A system as claimed in claim 7 or claim 8 wherein the second riser member is hollow, serves as a drain-pipe from the conduit and is connected to the outlet by a second branch pipe.

10. A system as claimed in any one of the preceding claims wherein the conduit is housed in a jacket of a translucent and heat insulating material.

1 1 . A system as claimed in claim 1 1 wherein the jacket comprises a tube of a translucent material and an annular air gap between the conduit and the tube.

1 2. A system as claimed in any one of claims 1 to 1 1 comprising a main reservoir having an outlet and an inlet, the main reservoir and the heating vessel being connectable in a circuit with the outlet of the main reservoir being connectable to the inlet of the heating vessel and the outlet of the heating vessel being connectable to the inlet of the main reservoir.

13. A system as claimed in claim 12 wherein the main reservoir comprises a hot water geyser.

14. A system as claimed in claim 1 1 or claim 1 2 comprising a water exchange pump connected in the circuit and configured to be controlled by a controller, wherein a first temperature sensor associated with the main reservoir and a second temperature sensor associated with the heating vessel are connected to the controller, and wherein the controller is configured to cause the pump to pump fluid from the heating vessel to the main reservoir, when a temperature sensed by the second sensor is higher than a temperature sensed by the first sensor.

1 5. A system as claimed in any one of claims 1 to 14 comprising drive means for driving the assembly to pivot about the first axis.

16. A system as claimed in claim 1 5 wherein the drive means is configured to drive the assembly to pivot about the second axis.

17. A system as claimed in claim 15 or claim 16 wherein the drive means is controlled by the controller and wherein the controller is connected to a solar signal source direction finder, the controller being configured to use an output signal of the direction finder to cause the drive means to drive the assembly to track and/or follow the sun.

18. A system as claimed in claim 1 7 wherein the direction finder comprises at least first and second detectors for the signal and a shield for partially obscuring the detectors from the signal to be monitored.

19. A system as claimed in claim 18 wherein the direction finder comprises a detector arrangement comprising a substrate; first, second, third and fourth photodetectors located in respective quadrants on the substrate defined by first and second mutually perpendicular opaque walls extending perpendicularly from the substrate; and an opaque roof on the walls.

20. A system as cfaimed in claim 19 wherein a fifth photodetector is provided on a surface of the roof facing away from the substrate.

21. A system as claimed in claim 20 or claim 21 wherein the photodetectors are connected to the controller, wherein the controller comprises a processor configured in use to execute a program to generate an output signal for controffing the drive means to drive the aforementioned assembly about the first pivot axis to follow the sun as it moves from east to west.

22. A solar signal direction finder comprising a detector arrangement comprising a substrate; first, second, third and fourth photodetectors located in respective quadrants on the substrate defined by first and second mutually perpendicular opaque walls extending perpendicularly from the substrate; and an opaque roof on the walls.