DESC:FIELD OF THE INVENTION
The present invention relates to a mirror panel assembly for a solar photovoltaic system. Particularly the invention relates to a mirror and panel assembly for a solar photovoltaic system for extracting maximum solar energy from the existing solar photovoltaic systems. Additionally the invention relates to a method of efficient energy extraction from existing solar photovoltaic systems. The present invention relates to incorporation of mirror arrays in the module inter row space of an existing PV array system at an optimal angle for enhanced extraction of solar power thus increasing the output energy of an existing solar photovoltaic system depending on seasonal variations.

BACKGROUND OF INVENTION
Solar power state of the art offers many advantages in the generation of electricity. It has zero raw fuel costs, unlimited supply and no environmental issues such as transport, storage, or pollution. Solar power is available everywhere, even on the moon. But to get the most out of a solar panel or solar array, it has to be pointed or “orientated” directly at the suns radiant energy because as we know, the more surface area that is exposed to direct sunlight, the more output the photovoltaic panel will produce. However, it should be noted that the PV panel is not fully utilised when the when the solar irradiance is low during early morning and late evening time zones between sun rise and sun set which need to be improved.
In the present literature, the existing photovoltaic solar panels which are made up of individual photovoltaic cells, are connected as Solar Photovoltaic Array, also known simply as a Solar Array. A photovoltaic array is therefore multiple solar panels electrically wired together to form a much larger PV installation (PV system) called an array, and in general the larger the total surface area of the array, the more solar electricity it will produce. Generally, any photovoltaic field system contains “n” number of arrays arranged in either series or parallel depending on output voltage and current requirement. Optimizing the output power of a photovoltaic panel improves the efficiency of a solar driven energy system. The maximum output power of a PV panel depends on atmospheric conditions, load profile and the tilt and orientation angles. In an experimental analysis, maximizing output power of a PV panel is obtained, based on existing equations of tilt and orientation angles derived from mathematical models and simulation packages. A data logger, DC-DC converter/maximum power point tracker, fixed load resistance and single PV panel is used. The PV panel is set to an orientation angle of 00 with tilt angles of 160, 260 and 360. So, the challenge in getting the maximum benefit of free solar power is to ensure that a photovoltaic solar panel or a complete PV array is correctly orientated and positioned with regard to the direct sunlight coming from the sun at all times of the day. As well as the “solar panel orientation”, the number of hours of sunlight in a day the solar panel receives as well as the intensity or brightness of the sunlight is also important.

If a solar photovoltaic system is designed, which is tilted or ground mounted with appropriate spacing between each row, then the system size is increased. Therefore, it is important to avoid accidental shading between modules of one row over other. The inter row-spacing of PV modules depends on factors like height difference (h) which in turn depends on tilt angle (?) of panel and module width (w).

Very few works are carried out in a smaller scale basis with an individual solar panel and mirror for less power rating. A Solar Home System (SHS) with two mirrors placed in each side of solar panel is proposed by Rizwanur Rahman et al. to direct the reflection of sun light towards the panel [1]. A single PV panel with mirror reflection and cooling mechanism is proposed by Rizwan Arshad et al. to increase in the solar efficiency [2], which is found to be minimal. A single PV panel placing mirrors on its four sides is designed by S. Julajaturasirarath et al. to increase sun light being reflected at an angle of 600 towards the panel [3]. In all the above work, the arrangement incorporating mirrors, cannot be used in a larger PV system such as solar parks with inter row spacing.

With regards to a system for efficient energy extraction from an existing solar photovoltaic system, there have been efforts to extract maximum energy through the existing arts disclosed.

US 8101849B2 titled “Tilt assembly for tracking solar collector assembly” to Amly & Sandler is disclosed. Here, a tilt assembly is used with a solar collector assembly of the type comprising a frame, supporting a solar collector, for movement about a tilt axis by pivoting a drive element between first and second orientations. The tilt assembly comprises a drive element coupler connected to the drive element and a driver, the driver comprising a drive frame, a drive arm and a drive arm driver. The drive arm is mounted to the drive frame for pivotal movement about a drive arm axis. Movement on the drive arm mimics movement of the drive element. Drive element couplers can extend in opposite directions from the outer portion of the drive arm, whereby the assembly can be used between adjacent solar collector assemblies in a row of solar collector assemblies.

US patent US 20030172922A1 to Haber titled “Solar panel tilt mechanism” disclosed a tilt mechanism associated with a solar panel assembly whereby effort required to tilt panel assemblies comprising the solar panel assembly is reduced or minimized by appropriate placement of first and second tilt axes with respect to the centre of mass and/or Centre of pressure of the panel assemblies due to wind. These arrays are suitable for use on mobile or static installations. The tilt mechanism is suited for harnessing wind energy if the panels are suitably shaped.

In all of the above cited arts, the person skilled in the art would understand that in all of the above conventional techniques disclosed, it is important to avoid accidental shading between the modules of one row over other. Also, if a PV system is designed, which is tilted or ground mounted with appropriate spacing between each row, then the system size increased.

Thus, those knowledgeable in the art would appreciate that in order to overcome the cited problems as they exist in the current art, an improved system for efficient energy extraction from an existing solar photovoltaic system needs to be developed.

Consequently there exists a utilised when the when the solar irradiance is low during early morning and late evening time zones between sun rise and sun set which need to be improved.

OBJECTS OF THE INVENTION
It is the primary object of the present invention to provide a system for efficient extraction of solar energy from solar photovoltaic systems.

It is another object of the present invention to provide a mirror and panel assembly for solar photovoltaic systems to extract maximum solar energy, by preventing shading between modules of one row over other.

It is yet another object of the present invention to provide a system for efficient solar energy extraction thereby reducing total payback period of the solar photovoltaic system.

SUMMARY OF THE INVENTION
One or more of the problems of the conventional prior art may be overcome by various embodiments of the present invention.

It is another aspect of the invention to provide a mirror and panel assembly for a solar photovoltaic system comprising of:
one or more solar panels; and
one or more mirrors aligned at an angle of the mirror,
wherein the solar panel is aligned at an tilt angle,
wherein the mirror is placed behind the solar panel at an optimal mirror angle;,
wherein the system is configured to prevent shading of one PV module over another, and
wherein the solar panel is aligned such that the angle of strike [Ip] of a reflected ray from the sun is sum of the sun elevation angle [E] and angle of tilt of the of the solar panel [?] deducted from twice the optimal angle of the mirror [d].

It is a another aspect of the invention to provide a mirror and panel assembly for a solar photovoltaic system, wherein the mirror is aligned at angle [d] to reflect solar rays towards the opposite panel, and extracts optimum solar energy when the elevation angle of the Sun is higher than the mirror angle [d].

It is a another aspect of the invention to provide a mirror and panel assembly for a solar photovoltaic system, wherein the system as claimed in claim 1, is executable for both tilted or ground mount photovoltaic system.

It is a another aspect of the invention to provide a mirror and panel assembly for a solar photovoltaic system, wherein angle of tilt of mirror [d] is the angle of the mirror with respect to the horizon in clockwise direction.

It is another aspect of the invention to provide a mirror and panel assembly for a solar photovoltaic system, wherein the mirror is aligned for the horizon to pass through the centre of the mirror.

It is another aspect of the invention to provide a mirror and panel assembly for a solar photovoltaic system, wherein coincidence of the reflected ray from the mirror with the horizon enables the mirror panel assembly to extract solar energy at all times of the year.

It is another aspect of the invention to provide a mirror and panel assembly for a solar photovoltaic system, wherein the angle of the mirror [d] is half the solar elevation angle [E] determined for a particular place.

It is yet another aspect of the invention to provide a mirror and panel assembly for a solar photovoltaic system, wherein the solar elevation angle is the average angle of solar elevation for all seasons for a given place.

It is another aspect of the invention to provide a mirror and panel assembly for a solar photovoltaic system, wherein the optimal angle is the averaged mirror angle [d] at solar noon in all four seasons.

It is another aspect of the invention to provide a method for optimal energy extraction by an aligned mirror and panel assembly of a solar panel comprising of the steps:
determining the seasonal change in elevation angle (E) of solar rays at solar noon;
determining optimal mirror angle (d) for each season or yearly averaged optimal mirror angle;
Installing a mirror behind the panel placed at a tilt angle [?] of the array at an optimal angle of the mirror;
measuring solar voltage, current and power using design measurement circuit of the solar photovoltaic system;
monitoring and storing the solar power and energy data, with and without mirror in all days of the year, and
wherein the optimal angle of mirror [d] is half the solar elevation angle [E] determined for a particular place,
wherein the solar panel is aligned such that the angle of strike [Ip] of a reflected ray from the sun is a sum of the sun elevation angle [E] and angle of tilt of the PV module [?] deducted from twice the optimal angle of the mirror [d].

BRIEF DESCRIPTION OF THE DRAWINGS:
So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, may be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of the invention's scope as it may admit to other equally effective embodiments.
Figure 1: Illustrates the Proposed solar photovoltaic system with Mirror and Panel Assembly [100].
Figure 2: Illustrates the Sun Path Chart.
Figure. 3. Top view and side view of the proposed solar photovoltaic system with the mirror and panel assembly [100]
Figure 4 illustrates the schematic diagram optimal placement of mirror [102]
Figure 5 illustrates the Elevation angle [E] on earth on Spring/Autumn season
Figure 6 illustrates the Elevation angle [E] on earth on Summer solstice season.
Figure 7 illustrates the Elevation angle [E] on earth on Winter solstice season.
Figure 8 Sun light incident on panel [101] and mirror [102].
Figure 9 Strike triangle of Reflected ray on the PV Module.
Figure 10 Schematic of the proposed mirror panel assembly enabled solar photovoltaic system.
Figure 11 Solar Energy and irradiation data plot of Energy Vs Days of the Month (February 2018) depicting energy improvement.
Figure 12 illustrates Capacity Utilization Factor CUF (CUF) variation during February 2018.
Figure 13 illustrates the power (watts) measured on 26th February 2018.

DESCRIPTION FOR DRAWINGS WITH REFERENCE NUMERALS:
[100] Mirror and Panel assembly
[101] Solar panel
[102] Mirror
[200] Sun
[201] Tiruchirapalli, Tamilnadu, India, location
[211] Incident rays of the Sun
[212] Reflected rays of the Sun
[221] Left side view of the mirror panel assembly [100]
[223] Right side view of the mirror panel assembly [100]
[222] Top view of the mirror panel assembly [100]

DETAILED DESCRIPTION OF THE INVENTION
The embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be construed that the various embodiments of the invention, although different, are not necessarily mutually exclusive. Furthermore, a particular feature, structure or characteristic described herein in connection with one embodiment may be implemented within other embodiments without departing from the scope of the invention. The following description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims, appropriately interpreted, along with the full range of equivalents to which the claims are entitled.

The main embodiment of the invention is directed towards a mirror and panel assembly [100] for a solar photovoltaic system and method for efficient energy extraction from any conventional solar photovoltaic system. This system effectively extracts more energy (30% from the base case) thereby, reducing total payback period of the solar PV system.

This invention enables to increase the output energy of an existing solar photovoltaic system varying from 28% to 32% depending up on the sunlight in a day and seasonal variation. Generally, any photovoltaic field system contains ‘n’ number of arrays arranged in either series or parallel depending on the output voltage and current requirement. Usually module inter-row spacing for tilted or ground mounted solar photovoltaic system are provided by giving more importance to reduce the shadow of one row over other and reducing the floor area of the overall solar photovoltaic system. If a solar photovoltaic system system is designed, which is tilted or ground mounted with appropriate spacing between each row, then the system size is increased. Therefore, it is important to avoid accidental shading between modules of one row over other [4-5]. The inter row-spacing of PV modules of the solar panel [101] depends on factors like height difference (h) which in turn depends on tilt angle (?) of panel and module width(w) as shown in the Figure 1. Illustration of proposed solar photovoltaic system system.

In Figure 1, i - angle of incidence, r- angle of reflection, d- inter row spacing, N- normal to mirror, w- width of the panel, d- Mirror angle, h- height difference, r- angle of reflection, d- inter row spacing, E- sun elevation angle, ?- Tilt angle of panel. Also, in Figure 2, ?-Azimuth angle.

Further, the inter row space is decided based on the time duration to eliminate shadow of one row over the other. The first step for calculating the inter-row spacing is to generate a sun path chart as illustrated in Figure 2, at the installation site. If site specific latitude and longitude are given as input, the University of Oregon’s Solar Radiation Monitoring Laboratory (SRML) provides an online program (solardat.uoregon.edu/SoftwareTools.html) for generating sun path chart (Figure 2). A case study on solar photovoltaic system is investigated with the following data Table 1.

Table 1: Case study Specifications
Place Thiruchirappalli-15, Tamil Nadu, India
Latitude 10.7542° N
Longitude 78.8198° E
Time Span 8 am - 4 pm (December 21)
Panel details
Pmax 75W
Voc 21.50V
Isc 4.92 A
Vmp 17.10V
Imp 4.39A
Max System Voltage 600V DC
Model Number USP75
Number of modules 6
Number of cells in each module 36
Number of Parallel connection 1
Number of Series connection 3 (3S1P)
Total Capacity 0.3 kW
Panel width (w) 1215 mm
Tilt angle of panel (?) 11o
Sun elevation angle (E) 23o
Height Difference ( )
231.83 mm
Inter row spacing (d=h/tan(E)) 546.16 mm
Mirror Details
Reflection coefficient (Plane mirror) 0.97 [8,9]
Mirror angle (d) 40o

Theory for optimal placement of mirror between two horizontal rows of SPV
Panel.
The proposed setup for the panel and mirror assembly with different views is shown in Figure 3, for the top view [222], left side view [221] and right side view [223] of the mirror and panel assembly [100] of an embodiment of the present invention. Figure 4 illustrates the optimal placement of the mirror.

Let the mirror angle with respect to horizon and measured in clockwise direction be d. For the system to work throughout the year, let the ray reflected from the mirror coincide with the horizon. The horizon passes through the middle of the mirror.
So, Angle AOX is the angle of inclination of the mirror.


Elevation angle of the sun is E,
E = 2d {as illustrated in Figure 4}
Calculation of Elevation Angle (E)
The elevation angles at which the sun’s rays reach the surface of the Earth in Tiruchirappalli at solar noon at the times of an equinox or a solstice (Spring/Autumn) is shown in (Figure 4). Thus, the most direct angle at which the Sun’s rays strike the ground in Tiruchirappalli is at about 79° on the days of a vernal and autumnal equinox. Similarly, the elevation angle for all season can be found out. It is evident that, on any day of the year, the most direct angle of solar radiation at a given location occurs at solar noon. In the northern hemisphere, the angle of solar elevation at noon is given in (2)
a = 90° – (? – SA) (2)
where, SA is sun declination angle.
Similarly, the formula for solar elevation at noon for points in the southern hemisphere is given in (3)
a = 90° + (? – SA) (3)

At solar noon, the range of angles at which the sun strikes the ground at Tiruchirappalli, varies from a minimum of 55.5° at the winter solstice to a maximum of 102.5° at the time of the summer solstice.

The elevation angle for all season is shown in Table 2 and graphical representation of calculation of elevation angle in all season is illustrated in Figure 5 to figure 7.
Table 2: Elevation angle at noon for all season
Si No. Season Angle of the sun rays with respect to equatorial reference - Sun declination angle Elevation angle at noon (E)
1 Summer 23.50 N 90+23.5 – 11 = 102.50
2 Spring/Autumn 00 90-11 = 790
3 Winter 23.50 S 90-23.5-11 = 55.50
Average 790

The elevation angle is determined at location Tiruchirapalli, Tamilnadu, India. The location is indicated by [201]. Incident rays of the sun in figures 5 to 7 represented as [211] and the reflected rays are repsented as [212].
To keep the system operational throughout the year, Take the elevation angle as average of all four season, i.e. Eopt =790
Eopt = 2dopt
=> dopt = Eopt /2
=> dopt = 79 /2 = 39.5 ˜ 400
Hence the optimal angle of the mirror is 400 .

Theory for Expression of Angle of Strike of Reflected ray on the panel.
Figure 8 shows the sun rays falling on the proposed system in both panel [101] and mirror [102]. Let the angle of strike of sun rays on the panel is Ip. Considering the triangle generated due to reflection rays’ panel and horizontal plane as in Figure 9. The different angles in this triangle are

of Strike of Reflected ray on the SPV Module, Ip
of Tilt of SPV Module, ?
of Tilt of Mirror, d
of Reflected ray wrt Mirror, E-d {Angle of Incident is equal to Angle of Reflection}
Let X
Now,

,
(4)
Also,

(5)
Solving equation (1) and (2)
and
Ip = 2d -180 + E +?

If the Azimuth angle (?) is between 270 to 0 and 0 to 900, the expression E become 180 – E, because in the Solar Data, elevation angle (E) is always between 0 to 900.

So, in this case the Expression for Ip is
Ip = 2d -E +?. In short
(6)

Another preferred embodiment of the present invention provides a method for
efficient energy extraction from an existing solar photovoltaic system using the mirror and panel assembly of the present invention [100] comprising the step of:
Analyzing the seasonal change in elevation angle (E ) of solar rays at solar noon;
Determining the optimal mirror angle ( dopt) for each season or yearly averaged optimal mirror angle; Install two identical 3S1P solar PV array configuration;
Installing a mirror [102] at optimal angle near to one of the array;
Design measurement circuit for measuring solar voltage, current and power using
Installing a mirror at behind the panel placed at a tilt angle [?] of the array at an optimal angle of the mirror;
measuring solar voltage, current and power using design measurement circuit of the solar photovoltaic system;
Continuously monitor and save the solar power and energy data, with and without mirror using Ni DAQ and LabVIEW software;
Tabulating the solar power and energy in all days in a month;

Analyzing the results and calculate the solar energy improvement in each day in a month and found out average solar energy improvement in a month.
The method according to A, wherein the step of estimating the optimal angle of mirror placement is based on
E = 2d {from the Figure 4), Where d -Mirror Angle with respect to horizon and measured in clockwise direction
E- Solar elevation angle
Optimal angle is the averaged mirror angle at solar noon in all four season which is found to be dopt = 79 /2 = 39.5 ˜ 400

Advantages of the Invention:
The advantage of the proposed system is that, with low capital cost and without disturbing the existing configuration of the solar array, the extraction of power from the sun is increased with shorter payback period. This invention will improve the energy extraction from the plant, which will in turn increase the utilization of plant effectively.
The foregoing is considered as an illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described.
WORKING EXAMPLE:
This work is performed to investigate the effect of optimal placement of plane mirror on the performance of an existing photovoltaic system and the main parameters affecting the amount of electrical energy output compared to the traditional normal fixed photovoltaic systems, without using any MPPT (Maximum Power Point Tracking) algorithm. The choice of optimal tilt angle (?) for a mirror is fundamental choice to its efficient operation because incorrectly positioning the mirror in the inter row space of solar array may not reflect the sun rays in the panel which will leads to an unnecessary loss in potential power. For this analysis, two identical traditional fixed 3S1P solar array configuration with and without mirror have been considered. The proposed invention is analyzed using the per minute data collected over all 28 days of February 2018 using NI DAQ and LabVIEW 2013. The daily cumulative electrical energy produced by the normal and proposed systems have been quantified separately for each day and the corresponding solar energy improvement have been compared to those of traditional fixed photovoltaic systems. An optimal mirror angle (dopt) of 300 is found by using solar data collected in January 2018.This is because January is close to Winter solstice. The energy improvement for all days of February 2018 is found as shown in Figure 11 in terms of % Energy Improvement on all days of February in 2018. It is found that the proposed system will improve around 30% of solar energy with respect to normal solar photovoltaic system. The gain amounts are varying between 28 to 32% depending on clearness and the seasonal variation of days. The results show there is a significant improvement in utilization of solar plant (17.7 %) with mirror placement (refer Figure 12). The improvement in solar power output (refer Figure 13) and hence energy will further increase when MPPT is incorporated in the experimental setup. Since the proposed system is made of low-cost plane mirrors which are easily available in market, the capital cost is very less. In addition to this, the proposed invention does not disturb the existing configuration of the solar array which increases the extraction of power from the sun with shorter payback period. ,CLAIMS:WE CLAIM:
1. A mirror and panel assembly [100] for a solar photovoltaic system comprising of:
one or more solar panels [101]; and
one or more mirrors [102] aligned at an angle of the mirror [d],
wherein the solar panel is aligned at an tilt angle [?],
wherein the mirror [102] is placed behind the solar panel at an optimal mirror angle [d],
characterized in that the system is configured to prevent shading of one PV module over another, and
wherein the solar panel [101] is aligned such that the angle of strike [Ip] of a reflected ray from the sun is sum of the sun elevation angle [E] and angle of tilt of the solar panel [?] deducted from twice the optimal angle of the mirror [d].

2. The mirror and panel assembly [100] for a solar photovoltaic system as claimed in claim 1, wherein the mirror is aligned at angle [d] to reflect solar rays towards the opposite panel, and extracts optimum solar energy when the elevation angle of the Sun is higher than the mirror angle [d].

3. The mirror and panel assembly [100] for a solar photovoltaic system as claimed in claim 1, wherein the system as claimed in claim 1, is executable for both tilted or ground mount photovoltaic system.
4. The mirror and panel assembly [100] for a solar photovoltaic system as claimed in claim 1, wherein angle of tilt of mirror [d] is the angle of the mirror with respect to the horizon in clockwise direction.

5. The mirror and panel assembly [100] for a solar photovoltaic system as claimed in claim 1, wherein the mirror is aligned for the horizon to pass through the centre of the mirror.

6. The mirror and panel assembly [100] for a solar photovoltaic system as claimed in claim 1, wherein coincidence of the reflected ray from the mirror with the horizon enables the mirror panel assembly to extract solar energy at all times of the year.

7. The mirror and panel assembly [100] for a solar photovoltaic system as claimed in claim 1, wherein the angle of the mirror [d] is half the solar elevation angle [E] determined for a particular place.

8. The mirror and panel assembly [100] for a solar photovoltaic system as claimed in claim 1, wherein the solar elevation angle is the average angle of solar elevation for all seasons for a given place.

9. The mirror and panel assembly [100] for a solar photovoltaic system as claimed in claim 1, wherein the optimal angle is the averaged mirror angle [d] at solar noon in all four seasons.

10. A method for optimal energy extraction by an aligned mirror and panel assembly [100] of a solar panel comprising of the steps:
determining the seasonal change in elevation angle (E) of solar rays at solar noon;
determining optimal mirror angle (d) for each season or yearly averaged optimal mirror angle;
Installing a mirror at behind the panel placed at a tilt angle [?] of the array at an optimal angle of the mirror;
measuring solar voltage, current and power using design measurement circuit of the solar photovoltaic system; and
monitoring and storing the solar power and energy data, with and without mirror in all days of the year,
wherein the optimal angle of mirror [d] is half the solar elevation angle [E] determined for a particular place, and
wherein the solar panel is aligned such that the angle of strike [Ip] of a reflected ray from the sun is a sum of the sun elevation angle [E] and angle of tilt of the solar panel [?] deducted from twice the optimal angle of the mirror [d].