US20040261786A1

US20040261786A1 - Solar energy conversion system

Info

Publication number: US20040261786A1
Application number: US10/499,383
Authority: US
Inventors: Wayne Kirk
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-12-17
Filing date: 2002-12-17
Publication date: 2004-12-30
Also published as: AUPR956801A0; WO2003052330A1

Abstract

A solar energy conversion system comprising: a solar radiation reflector having a plurality of elongate reflective members that are fixed in position relative to each other, said solar radiation reflector being mounted for rotation about a single axis; a rotation device operatively connected to said radiation reflector for rotating said radiation reflector about said single axis; at least one solar radiation transducer located at a position coincident with at least one focal area of the plurality of angled reflective members of said solar radiation reflector; and a solar tracking unit for tracking the relative movement of the sun relative to the earth; said solar tracking unit causing said rotation device to rotate said solar radiation device toward the sun.

Description

FIELD OF THE INVENTION

This invention relates to a solar energy conversion system. In particular, the invention relates to solar energy conversion to electrical power and will therefore be described in this context. However, should be appreciated that the solar energy conversion system may be used to convert solar energy to other forms of energy.

BACKGROUND OF THE INVENTION

Solar energy conversion systems have been recognized as one of the most environment friend forms for the generation of electrical power. However, there has been great difficulty in producing solar energy conversion systems that are both cost effective and conversion efficient.

Most solar energy conversion systems, such as those described in International Patent Application No. WO 97/49956, include a parabolic reflector for the reflection for sunlight. The parabolic reflector comprises a curved surface that reflects all incident solar radiation, which is parallel to a principal axis of the reflector, to a single focal point. This concentrates the solar radiation for conversion to electrical power. A photovoltaic cell is located at the focal point to convert the concentrated solar radiation to electrical power.

A tracking mechanism is used to move the reflector in accordance with the relative movement of the earth to the sun so that all incident solar radiation remains parallel to a principal axis of the reflector. This ensures that that the photovoltaic cell is always at the focal point to maximize energy conversion during daylight hours.

One disadvantage of the above system is the parabolic reflector is must be moved about at least two axes to keep the photovoltaic cell at the focal point of the reflector. The movement of the reflector, is therefore, relatively complex. Subsequently, the tracking mechanism is difficult and costly to produce. Further, the cost of producing parabolic reflectors is relative expensive due to the need to for specialized machinery. Still further, a series of parabolic reflectors are required to cover large areas.

OBJECT OF THE INVENTION

It is an object of the invention to overcome or alleviate one or more of the above disadvantages or provide the consumer with a useful or commercial choice.

It is preferred object of the invention to provide a solar radiation reflector, which is simple in construction and is not required to be parabolic in shape.

SUMMARY OF THE INVENTION

In one form, though not necessarily the only or broadest form, the invention resides in a solar energy conversion system comprising:

a solar radiation reflector having a plurality of elongate reflective members that are fixed in position relative to each other, said solar radiation reflector being mounted for rotation about a single axis;

a rotation device operatively connected to said radiation reflector for rotating said radiation reflector about said single axis;

at least one solar radiation transducer located at a position coincident with at least one focal area of the plurality of angled reflective members of said solar radiation reflector; and

a solar tracking unit for tracking the relative movement of the sun relative to the earth; said solar tracking unit causing said rotation device to rotate said solar radiation device toward the sun;

In a preferred form of the invention, the solar radiation reflector is secured to a base having a pair of upward extending mounting members.

Preferably the axis of rotation is in one plane only.

The plurality of angled reflective members is preferably arranged so that at least one edge of each angled reflective member is in a common plane.

Each of the elongate reflective members may have a reflective surface that is planar or curved.

Preferably, the solar energy conversion system comprises two solar radiation transducers.

The angled reflective members preferably reflect incident solar radiation to at least two areas of focus coincident with said solar radiation transducers.

The solar radiation transducers maybe mounted on to respective said upward mounting members. A longitudinal axis of the solar radiation reflector may be substantially parallel with the mounted solar radiation transducers.

The rotation device preferably includes a rotatable shaft supported by the base for rotation about said axis.

Preferably the rotation device also includes a drive mechanisms for providing motive force to rotate said solar radiation reflector. The drive mechanism may be a d.c. motor.

The solar tracking unit preferably includes two solar radiation converters mounted on a pair of the angled reflective members that have opposing orientations. The solar radiation converters may be electrically connected to a decision circuit. The solar radiation converters provide an input for determining the amount of incident radiation upon each of the angled reflective members at any point in time. The decision circuit may comprise voltage comparators for comparing the voltage potentials of the two solar radiation converters.

The decision circuit preferably causes said drive mechanism to rotate the reflector when the measured voltage potentials of the two solar radiation converters are not balanced thereby indicating uneven solar radiation being received at the respective solar radiation converters.

Preferably, the solar radiation converters are two small photovoltaic cells which are matched or linearised so that their voltage outputs are equal for the same amount of incident light.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will be described, by way of example only, with reference to the accompany drawings in which: [0025]
FIG. 1 is an illustrative embodiment of the solar energy conversion system in accordance with invention. [0026]
FIG. 2 is a schematic of the solar tracking unit of the solar energy conversion system. [0027]
FIG. 3 is a schematic of a decision circuit of the solar tracking unit of FIG. 2. [0028]
FIGS. 4 and 5 are illustrative embodiments of the operation of the solar energy conversion system.[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a solar [0030] energy conversion system 10 including a base 20 to which is secured a plurality of mounting members 30 and a solar radiation reflector 40.
The [0031] solar radiation reflector 40 comprises a number of planar reflective members 41 and 42 that are joined to each other. Each planar reflective member 41 is joined to an adjacent planar reflective member 42 along an edge. This forms a radiation reflector 40 having a corrugated shape as shown. A process of extrusion, using either plastics or metallic or glass or any other suitable material, is used to produce the corrugated shape of the solar radiation reflector 40.
The [0032] reflective members 41 and 42 each have different inclinations. Hence, when each reflective member is provided with the same direction of incident solar radiation, the reflected solar radiation is reflected at a different angle from each of the reflective members 41 and 42.
The [0033] mounting members 30 are used to mount solar radiation transducers 31 and 32. The transducers 41 and 42 are mounted to the mounting members 30 such that when incident solar radiation hits the reflective members, 41 or 42, the reflected solar radiation is concentrated at either transducer 31 or 32. That is, a focal area of the plurality of reflective members 41 or 42 is coincident with the respective transducers 31 or 32.
The selection of the angles for the [0034] reflective members 41 and 42 depend on the position of the solar radiation transducers 1 and 32. Various angles may be chosen for the reflective members 41 and 42 and these may be determined depending on where the solar radiation transducers 31 and 32 are mounted on mounting members 30. A person skilled in the art would not have any difficulty in experimenting with numerous angles to achieve the most optimum and desired result. Furthermore, the planar surface of each of the angled reflective members 41 or 42 provides a simpler construction than the parabolic concentrators used in prior art systems.
A [0035] rotation device 60 is operatively connected to the base 20 for rotating the solar radiation reflector 40 about a single axis X. The rotation device 6 includes a rotatable shaft (not shown) attached to the base 20 and extends longitudinally with respect to the solar radiation reflector 40 thereby providing rotation of the solar radiation reflector and solar radiation transducer 41 and 42 about the axis X. The rotation device 60 is operated by a drive mechanism (not shown) having a dc motor 150 as shown in FIG. 3.
Referring now to FIGS. 2 and 3, there is shown a [0036] solar tracking unit 70 and the decision circuit 100 which together provide the necessary electrical input for causing the rotation of the reflector 40.
The [0037] solar tracking unit 70 comprises two solar radiation converters 8 and 9 mounted on the reflector 40. The two converters 80 and 90 are electrically connected to the decision circuit 100. The radiation converters 80 and 90 are small photovoltaic cells that have been matched or linearised so that their voltage outputs are equal for the same amount of incident solar radiation. This is achieved by straight manufacturing or the outputs may be tuned or conditioned and amplified by electronic or physical means such as masking or doping.
The [0038] photovoltaic cells 80 and 90 are located on a central pair of angled reflective members 41 and 42 that forms an isosceles triangle with the base 20. The photovoltaic cells 80 and 90 are mounted the pair of angled reflective members that have opposing orientations. Therefore the photovoltaic cells 80 and 90 enable to determine the amount of incident radiation upon each of the angled reflective members of radiation reflector 40 at any point in time.
The [0039] decision circuit 100 is comprised of comparators 110 and 120, and relays 130 and 140 that control the operation of the dc motor 150 that is used to rotate the reflector.
In the desired alignment of the energy conversion system, as shown in FIG. 2, the angle of the [0040] incident radiation 160 on the photovoltaic cells 80 and 90 are equal and therefore the area and amount of solar radiation collected will be the same. The voltage outputs for the photovoltaic cells 80 and 90 are therefore the same and hence, comparators 110 and 120 are inactive and no power is supplied to the dc motor 150.
FIG. 4 illustrates the situation where the earth rotates and the incident [0041] solar radiation 160 on photovoltaic cells 80 and 90 are no longer equal. Consequently, the area and amount of solar radiation will be greater on photovoltaic cell 80 than on photovoltaic cell 90. Hence, the output voltage on photovoltaic cell 8 will be greater than photovoltaic cell 90. This will cause comparator 110 in FIG. 3 to activate relay 130 which will then activate the dc motor 150 and provide an anti clockwise motion until equilibrium is achieved as shown in FIG. 2.
FIG. 5 illustrates the situation before sunrise or after cloud cover where the angles of the incident [0042] solar radiation 160 are different on photovoltaic cell 80 and photovoltaic cell 90. As a result, the amount and area of incident radiation collected on photovoltaic cell 90 will be greater than on photovoltaic cell 80, and therefore the output voltage on cell 90 will be greater than cell 80. Consequently, this will cause comparator 120 to activate relay 140 and cause dc motor 150 to operate in a clockwise direction until equilibrium is achieved as shown in FIG. 2.
In operation therefore, incident [0043] solar radiation 160 is reflected off the angled reflective members 41 toward transducers 31 whilst incident solar radiation 160 is reflected off the angled reflective members 42 toward transducers 32. The direction of the incident solar radiation relative to the reflective members 41 and 42 is maintained at a constant direction using the solar tracking unit. Therefore, the solar radiation reflector 40 provides the optimum amount of reflected solar radiation to the respective transducers 31 and 32.
An advantage of the present invention is it only requires rotation of the [0044] reflector 40 in one axis to track incident solar radiation whist providing the optimum amount of reflected solar radiation. Further, the reflector 40 can be produced cost effectively and simply.
It is envisaged that multiple or a single focal area and multiple or a single solar radiation transducer(s) may be used to produce other embodiments of the invention. [0045]
It should be appreciated that the solar radiation transducers may include photovoltaic cells for generating electricity connected to a power grid or alternatively they could house other means for energy conversion. [0046]
It should also be appreciated that various other changes and/or modifications may be made to the embodiment described without departing from the spirit or scope of the invention. [0047]

Claims

1. A solar energy conversion system comprising:

a solar radiation reflector having a plurality of elongate planar reflective members that are fixed in position relative to each other, said solar radiation reflector being mounted for rotation about a single axis;

at least two solar radiation transducers located at positions coincident with at least two focal areas of said plurality of angled reflective members of said solar radiation reflector; and

2. The solar energy conversion system of claim 1 wherein at least one reflective member is joined to an adjacent reflective member to form a corrugated reflector.

3. The solar energy conversion system of claim 1 wherein said reflective members reflect incident solar radiation to at least two focal areas coincident with said solar radiation transducers.

4. The solar energy conversion system of claim 1 wherein the rotation device includes a rotatable shaft that is rotated by a drive mechanism.

5. The solar energy conversion system of claim 4 wherein the drive mechanism is a dc motor.

6. The solar energy conversion system of claim 1 wherein the solar tracking unit includes two solar radiation converters mounted on a pair of the angled reflective members that have opposing orientations.

7. The solar energy conversion system of claim 6 wherein the solar radiation converters are electrically connected to a decision circuit.

8. The solar energy conversion system of claim 7 wherein the solar radiation converters provide an input for determining the amount of incident radiation upon each of the angled reflective members.

9. The solar energy conversion system of claim 7 wherein the decision circuit comprises voltage comparators for comparing the voltage potentials of the two solar radiation converters.

10. The solar energy conversion system of claim 9 wherein the decision circuit causes said rotation device to rotate the reflector when the measured voltage potentials of the two solar radiation converters are not balanced.

11. The solar energy conversion system of claim 7 wherein each of said solar radiation converters are two small photovoltaic cells.