U.S. patent application number 16/385685 was filed with the patent office on 2019-08-08 for photovoltaic plant.
The applicant listed for this patent is ARCHIMEDE RESEARCH S.R.L.. Invention is credited to CALOGERO GATTUSO, GIANLUCA TUMMINELLI, GAETANO TUZZOLINO.
Application Number | 20190245106 16/385685 |
Document ID | / |
Family ID | 50349784 |
Filed Date | 2019-08-08 |
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United States Patent
Application |
20190245106 |
Kind Code |
A1 |
TUMMINELLI; GIANLUCA ; et
al. |
August 8, 2019 |
PHOTOVOLTAIC PLANT
Abstract
A method for orienting an array of mobile reflection device of a
photovoltaic plant including a plurality of photovoltaic modules
arranged in arrays spaced with respect to each other is disclosed.
The photovoltaic modules of each array have a first assigned
inclination with respect to a reference direction. Each array of
photovoltaic modules is associated to an array of mobile reflection
devices set adjacent thereto, and at least one array of mobile
reflection devices is located in a space between successive arrays
of photovoltaic modules. The mobile reflection devices of each
array have a second assigned inclination with respect to a
reference direction. The arrays of photovoltaic modules and the
arrays of mobile reflection devices associated to one another
includes respective front surfaces set facing one another, and the
mobile reflection devices of each array are orientable by variation
of said second inclination in order to intercept the incident solar
radiation and reflect the latter towards the photovoltaic modules
of the associated array.
Inventors: |
TUMMINELLI; GIANLUCA;
(CALTANISSETTA, IT) ; TUZZOLINO; GAETANO;
(CALTANISSETTA, IT) ; GATTUSO; CALOGERO;
(CALTANISSETTA, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ARCHIMEDE RESEARCH S.R.L. |
CALTANISSETTA |
|
IT |
|
|
Family ID: |
50349784 |
Appl. No.: |
16/385685 |
Filed: |
April 16, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15113513 |
Jul 22, 2016 |
10263133 |
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PCT/IB2015/050513 |
Jan 23, 2015 |
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16385685 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02E 10/52 20130101;
H01L 31/0547 20141201; H01L 31/0475 20141201; H02S 20/10 20141201;
H02S 40/22 20141201 |
International
Class: |
H01L 31/054 20060101
H01L031/054; H01L 31/0475 20060101 H01L031/0475; H02S 40/22
20060101 H02S040/22; H02S 20/10 20060101 H02S020/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 23, 2014 |
IT |
TO2014A000050 |
Claims
1. A method for orienting an array of mobile reflection devices of
a photovoltaic plant, the photovoltaic plant including a plurality
of photovoltaic modules arranged in arrays spaced with respect to
each other, and wherein the photovoltaic modules of each array have
a first assigned inclination with respect to a reference direction,
wherein associated to each array of photovoltaic modules is an
array of mobile reflection devices set adjacent thereto, and
wherein at least one array of mobile reflection devices is located
in a space between successive arrays of photovoltaic modules;
wherein the mobile reflection devices of each array have a second
inclination with respect to a reference direction; wherein the
arrays of photovoltaic modules and the arrays of mobile reflection
devices associated to one another include respective front surfaces
set facing one another; and wherein the mobile reflection devices
of each array are orientable by variation of said second
inclination in order to intercept the incident solar radiation and
reflect the latter towards the photovoltaic modules of the
associated array, the method comprising: a first step of detection,
within the framework of a time interval having a predetermined
duration, the values of one or more physical quantities which are
representative of operative conditions of an installation site of
the photovoltaic plant, a second step of calculation, within the
framework of said time interval, of an inclination value of the
array of mobile reflection devices as a function of detected values
of said one or more physical quantities, a third step of comparison
of the calculated inclination value with a theoretical and
pre-calculated optimal inclination value, a fourth step of
correction of said pre-calculated theoretical optimal inclination
value with said calculated inclination value, wherein the first,
the second, the third and the fourth steps are repeated along a
sequence of time intervals having a predetermined duration.
2. The method according to claim 1, wherein said one or more
physical quantities include: i) incident solar radiation; ii)
string current; iii) height of the Sun, iv) direction and intensity
of the wind; and v) inclination of the structure.
3. The method of claim 1, wherein each array includes two
respective short sides parallel to one another and two respective
long sides parallel to one another and orthogonal to the
corresponding short sides, each array of mobile reflection devices
being set, with respect to the associated array of photovoltaic
modules, so that the respective long sides are substantially
parallel to one another and so that the long side of the array of
mobile reflection devices closer to the ground is immediately
adjacent to the long side of the array of photovoltaic modules
closer to the ground.
4. The method of claim 1, wherein each array of photovoltaic
modules and the array of associated mobile reflection devices are
set in a V shape.
5. The method of claim 1, wherein each array of mobile reflection
devices includes a plurality of mirrors installed on a frame
articulated with respect to a supporting structure that anchors and
fixes the array to the ground.
6. The method according to claim 5, wherein said plurality of
mirrors includes one of the following types: plane mirrors; and
convex mirrors.
7. The method of claim 5, wherein said frame is connected to said
supporting structure by means of an articulated joint integrating a
motor-reducer assembly operatively connected to an electronic
control unit, wherein said electronic control unit is configured
for driving said motor-reducer assembly so as to vary the
orientation of said mirrors.
8. The method of claim 5, wherein said frame is connected and
articulated to said supporting structure by means of a linear
actuator having a first end articulated to said frame about a first
axis and a second end articulated to said supporting structure
about a second axis, said frame being moreover articulated to the
associated array of photovoltaic modules at the respective long
sides of each array.
9. The method of claim 8, wherein said linear actuator is
operatively connected to an electronic control unit configured for
governing retraction or extraction of a stem of said linear
actuator so as to vary the orientation of said plane mirrors.
10. A method for the variation of the concavity of an array of
mobile reflection devices of a photovoltaic plant including a
plurality of photovoltaic modules arranged in arrays spaced with
respect to each other, and wherein the photovoltaic modules of each
array have a first assigned inclination with respect to a reference
direction, wherein associated to each array of photovoltaic modules
is an array of mobile reflection devices set adjacent thereto, and
wherein at least one array of mobile reflection devices is located
in a space between successive arrays of photovoltaic modules;
wherein the mobile reflection devices of each array have a second
inclination with respect to a reference direction; wherein the
arrays of photovoltaic modules and the arrays of mobile reflection
devices associated to one another include respective front surfaces
set facing one another; and wherein each array of mobile reflection
devices includes a plurality of deformable mirrors installed on a
supporting frame having a fixed inclination with respect to the
ground, and wherein associated to each of said mobile mirrors is an
actuator assembly configured for causing a deformation thereof that
modifies a concavity thereof, the method comprising: detecting an
intensity of the solar radiation in correspondence of each of said
long sides of the associated array of photovoltaic modules; and
controlling a movement of said actuator assembly in order to
produce a variation of concavity of said mobile reflection devices
as a function of the detected intensity of the solar radiation,
wherein the step of controlling a movement of said actuator
assembly is reiterated until a concavity is identified such that
the values of intensity of the solar radiation in correspondence of
each of said long sides of the associated array of photovoltaic
modules are equal to maximum values for the respective long
side.
11. The method according to claim 10, wherein said step of
detecting the intensity of the solar radiation is carried out in a
continuous way.
12. The method according to claim 10, wherein the intensity of the
solar radiation at each of said long sides includes: a lower-limit
value equal to the value of intensity of the incident radiation in
correspondence of the respective long side; and an upper-limit
value, corresponding to the maximum value of intensity of the solar
radiation that can be detected at the respective long side in a
given condition of irradiation of the photovoltaic plant, said
upper-limit value being equal to the sum of the value of intensity
of the incident radiation at the respective long side and of the
maximum value of intensity of the reflected radiation that can be
detected at the respective long side,
13. The method of claim 10, wherein each actuator assembly includes
a linear actuator having a first end hinged to the supporting frame
and a second end hinged to a dorsal surface of the corresponding
deformable mirror.
14. The method of claim 13, wherein the second end of the linear
actuator is hinged at the geometrical centre of the dorsal surface
of the corresponding deformable mirror.
15. The method of claim 13, wherein each deformable mirror is
moreover fixed to said supporting frame by means of a plurality of
sliding hinges, wherein each sliding hinge is mobile in a direction
parallel to a short side of said array of mobile reflection
devices.
16. The method according to claim 10, wherein each deformable
mirror comprises a deformable sheet of reflecting material.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This U.S. Continuation Application claims priority to U.S.
National Phase Patent application Ser. No. 15/113,513, filed Jul.
22, 2016, which claims priority to International Patent Application
No. PCT/IB2015/050513, filed Jan. 23, 2015, which claims priority
to Italy Application No. TO2014A000050, filed Jan. 23, 2014, the
entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Technical Field
[0002] The present invention relates to photovoltaic plants.
2. Related Art
[0003] The technique of construction of photovoltaic plants
commonly adopted envisages installation of a plurality of arrays of
photovoltaic modules, each set with an assigned inclination with
respect to a reference direction (for example, the horizontal or
ground) so as to capture for the longest time possible solar
radiation in a normal or practically normal direction. There may be
envisaged solutions in which all the photovoltaic modules of one
and the same array have the same assigned inclination or else have
inclinations that differ to a varying extent in order to maximize
absorption of energy from solar radiation.
[0004] Installation of the photovoltaic modules with an assigned
inclination implies, however, that these are for the most part
detached from the ground, with consequent generation of shadows of
variable length according to the inclination of the solar rays.
This imposes the need to arrange the arrays of photovoltaic modules
envisaging wide free aisles between them in order to prevent the
photovoltaic modules of one array from projecting their own shadow
on the photovoltaic modules of the adjacent array, thus reducing
the efficiency thereof and hence the productivity of the plant.
[0005] If on the one hand this enables minimization of the
phenomenon of shading referred to above, on the other it entails a
considerable disadvantage in terms of exploitation of the ground.
In other words, pre-arrangement of wide free aisles between the
arrays of photovoltaic modules drastically reduces the fraction of
ground that can be used for installation of photovoltaic modules
with respect to the overall surface of the ground on which the
plant is installed, with evident economic disadvantages. In other
words, a considerable fraction of the ground--the fraction
constituted by the aisles between the arrays--is, in fact, not
exploited and is unproductive in so far as it only has the purpose
of receiving the shadows of the photovoltaic modules of an
array.
BRIEF SUMMARY OF THE INVENTION
[0006] The object of the invention is to solve the technical
problems mentioned previously. In particular, the object of the
invention is to provide a photovoltaic plant in which, albeit
maintaining the conventional structure formed by arrays set at a
distance so as to prevent problems of shading, the efficiency and
productivity are considerably increased as compared to known
photovoltaic plants.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The invention will now be described with reference to the
annexed figures, which are provided purely by way of non-limiting
example and in which:
[0008] FIG. 1 is an aerial view of a photovoltaic plant according
to the present invention;
[0009] FIG. 2 is a view according to the arrow II of FIG. 1;
[0010] FIG. 3 is a view similar to that of FIG. 2 but regarding a
further embodiment of the invention;
[0011] FIG. 4 is a view similar to that of FIGS. 2 and 3 but
regarding yet a further embodiment;
[0012] FIG. 5 is a view similar to that of FIGS. 2, 3, and 4, but
regarding yet a further embodiment; and
[0013] FIG. 5A is an enlarged view of the detail indicated by the
arrow V in FIG. 5; and
[0014] FIGS. 6A and 6B are enlarged views of a detail indicated by
the arrow VI in FIG. 5 and corresponding to two different operating
conditions.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0015] The object of the invention is achieved by a photovoltaic
plant having the features forming the subject of one or more of the
appended claims, which form an integral part of the technical
disclosure provided herein in relation to the invention.
[0016] In particular, the object of the invention is achieved by a
photovoltaic plant including a plurality of photovoltaic modules
arranged in arrays spaced with respect to each other, wherein the
photovoltaic modules of each array have a first assigned
inclination with respect to a reference direction,
[0017] the photovoltaic plant being characterized:
[0018] in that associated to each array of photovoltaic modules is
an array of mobile reflection devices set adjacent thereto, and
wherein at least one array of mobile reflection devices is located
in a space between successive arrays of photovoltaic modules;
[0019] in that the mobile reflection devices of each array have a
second inclination with respect to a reference direction;
[0020] in that the arrays of photovoltaic modules and the arrays of
mobile reflection devices associated to one another include
respective front surfaces set facing one another; and
[0021] in that the mobile reflection devices of each array are
orientable by variation of said second inclination in order to
intercept the incident solar radiation and reflect the latter
towards the photovoltaic modules of the associated array.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0022] In FIG. 1, the reference number 1 designates as a whole a
photovoltaic plant according to various preferred embodiments of
the invention.
[0023] The photovoltaic plant 1 includes a plurality of
photovoltaic modules PV arranged in arrays 2 set at a distance from
one another. The distance between the arrays is designated by the
reference IA in FIG. 1. Associated to each array 2 is a
corresponding array 4 of mobile reflection devices, each designated
by the reference RF, which is set adjacent thereto. The arrays 4
are located in the space between two adjacent arrays 2. There may
be the exception of some arrays 4 set in peripheral areas of the
photovoltaic plant 1 (as may be seen in the bottom portion of FIG.
1), but in the plant 1 according to the invention at least one
array 4 occupies the space between (two) successive arrays 2.
[0024] With reference to both FIGS. 1 and 2, each photovoltaic
module PV includes a plurality of sets of photovoltaic cells,
designated by the reference PC, joined together to constitute a
photovoltaic panel of a rectangular shape. Each array 2 is hence
constituted by a number of photovoltaic modules PV arranged side by
side and preferably aligned (coplanar) with respect to one another.
In this way, it is possible to identify, for the array 2, a pair of
short sides A2 parallel to one another and a pair of long sides B2
parallel to one another and orthogonal to the short sides A2.
[0025] The photovoltaic panel is surrounded by and received in a
perimetral frame 6 fixed to which, in particular to a dorsal
surface 10 thereof, is a supporting post 8. The post 8 fixes and
anchors the photovoltaic module PV to the ground G. Fixing of the
perimetral frame 6 to the post 8 is provided so as to obtain an
assigned inclination .alpha.1 (which is generally fixed) with
respect to a reference direction, for example a horizontal
direction (here the ground G is represented aligned to the
horizontal so that the inclination .alpha.1 may also--indifferently
in this case--be referred to the ground). The inclination .alpha.1
moreover coincides with the inclination of a front surface 12 of
the photovoltaic module PV, on which the photovoltaic cells PC are
arranged so as to intercept the solar radiation with an angle of
incidence falling within an optimal range of values. The angle
.alpha.1 is in general chosen in the range of values comprised
between 0.degree. and 90.degree..
[0026] Finally, it should be noted that the perimetral frame 6 of
each photovoltaic module PV (hence, basically, the photovoltaic
panel of the module PV) in turn includes two short sides parallel
to one another (of a length identical to the side A2, in so far as
they define in effect the latter) and two long sides B6 (appearing
in brackets alongside the reference PV), parallel to one another
and orthogonal to the short sides. Within each array 2 the
photovoltaic modules PV are arranged so that the respective long
sides B6 are substantially aligned to define the sides B2.
[0027] Each array 4 includes a plurality of plane mirrors that
define the reflection devices RF. It is hence to be noted that by
the term "mirror" is here meant in general an element provided with
a reflecting surface (or, at the limit, the reflecting surface
itself). This means that falling within this definition is a
plurality of different devices, all having in common the property
of reflecting light (in this case visible light). For this reason
the mirrors RF may be made, for example, of materials such as
silvered moulded glass (corresponding to the most conventional kind
of mirror), the so-called "super mirror" steel, chrome-plated
polymers, etc.
[0028] Each plane mirror RF includes a front reflecting surface 14
configured for reflecting solar light, and a dorsal surface 16,
where fixing to a supporting frame 18 is envisaged. Fixed to the
supporting frame 18 are one or more supporting posts 20 that anchor
and fix the supporting frame 18, i.e., the plane mirrors RF, to the
ground G.
[0029] In this connection, it should be noted that--in a way
similar to the array 2--it is possible to identify for the array 4
a pair of short sides A4 parallel to one another and a pair of long
sides B4 parallel to one another and orthogonal to the short sides
A4. In a preferred embodiment, the supporting frame 18 extends so
as to cover the entire length of the sides B4 (i.e., the entire
extension of the array 4) and the plane mirrors RF are hence
installed on the frame 18 side by side and substantially without
solution of continuity. In this case, also a number of supporting
posts 20 are provided coupled to the frame 18 given the
considerable length thereof, typically of the order of tens of
metres (17-20 m). The supporting post 20 is moreover just one of
the possible examples of supporting structures for the frame 18:
other embodiments may include, instead of the supporting post 20,
surface ballasts made of slightly reinforced concrete fixed to
which are supporting posts that are not mechanically driven into
the ground. This solution is typical of installations in rocky
terrains.
[0030] Moreover set at the interface between the support 20 and the
dorsal surface 18 is an articulated joint 22 by means of which the
plane mirrors RF are articulated with respect to the support 20
about a preferentially horizontal axis XRF. The system here
illustrated envisages a uniaxial articulated joint, but it is
possible, if the conformation of the ground were so to require, to
envisage multi-axial articulated joints so as to guarantee an
optimal positioning in any condition (further details will be
provided in what follows).
[0031] Each supporting post 20 is connected to the supporting frame
18 by means of an articulated joint 22. The latter enables
articulation of the frame 18 with respect to the post 20 about a
horizontal axis XRF entering the plane of the drawing. Moreover
possible are embodiments in which the plane mirrors RF are arranged
in sets installed on independent frames 18, and each provided with
its own supporting post (or posts) 20.
[0032] The articulated joint 22 is moved via a motor-reducer
assembly integrated therein and operatively connected to an
electronic control unit for its actuation. In this way, it is
possible to govern a (controlled) oscillation movement of the frame
18 (and hence of the mirrors RF) about the axis XRF, whereby the
mirrors RF are moved with respect to the ground G.
[0033] This means that, if .alpha.2 is the angle of inclination
between the front surface 14 of the mirrors RF and a reference
direction here assumed as coinciding with the horizontal (and, for
what has been said previously, with the ground G), the angle
.alpha.2 has a variable amplitude that can be controlled by means
of the motor-reducer assembly integrated in the articulated joint
22.
[0034] In this embodiment, the articulated joint 22 is basically
positioned in the median position between the long sides B4;
however, embodiments are possible with axis of rotation off-centre
and located at one of the long sides B4.
[0035] Each array 4 is set, with respect to the array 2 to which it
is associated, so that the long sides B4 and B2 are substantially
parallel to one another. Moreover, the long side B4 closer to the
ground G is immediately adjacent to the long side B2 closer to the
ground G.
[0036] It should be noted that, as a result of the inclination
assigned to the photovoltaic modules PV and to the mirrors RF,
there always exists in each array 2, 4 a difference of geometrical
height of the respective long sides B2, B4 with respect to the
ground G: the side B2 (or B4) of each array 2 (or 4) closer to the
ground will hence be the one having a smaller geometrical height
(i.e., a smaller distance) from the ground and is designated, in
brackets, by the reference B2L (or B4L). Logically, the side B2 (or
B4) further away from the ground will be the one at a greater
geometrical height/distance from the ground itself, and is
designated; in brackets, by the reference B2H (or B4H).
[0037] In other words, whatever the variation imposed on the angle
.alpha.2, it must fall in a range such that the front surface 14 of
the mirrors RF is at least partially in view of the front surface
12 of the photovoltaic modules PV, defining (see in this connection
the view of FIG. 2) a substantially V-shaped geometry of the
ensemble constituted by an array 2 and an array 4 associated
thereto. The reasons for this will emerge more clearly in what
follows.
[0038] Operation of the photovoltaic plant 1 is described
hereinafter.
[0039] With reference to FIG. 2, the incident solar
radiation--designated by the reference ISR--strikes the
photovoltaic plant 1 impinging both upon the photovoltaic modules
PV and upon the mobile reflection devices RF. When the incident
solar radiation ISR strikes the mirrors RF, these reflect it
towards the photovoltaic modules PV. The reflected radiation is
designated by the reference RSR. This renders evident the reason
why the front surfaces 14 and 12 must face one another: this is
necessary so that the reflected solar radiation RSR will strike the
photovoltaic cells on the front surface 12 of the photovoltaic
modules PV.
[0040] If this were not so, reflection of the solar radiation
obtained with the mirrors RF would impinge totally or in part on
areas different from the front surface 12, where no useful effect
would be produced.
[0041] Moreover stored in the electronic control unit that controls
the articulated joint 22 is an algorithm conceived for computing
and selecting the values of the angle .alpha.2 so as to optimize
the angle of incidence of the reflected solar radiation RSR on the
photovoltaic modules PV (i.e., on the solar panels that constitute
them).
[0042] The algorithm moreover operates having as input variables
the date (i.e., it takes into account the period of the year) and
time of day, as well as statistical information on the angles of
incidence of the solar radiation with respect to the horizon in the
geographical region where the plant 1 is installed. In greater
detail, the articulated joint 22 is controlled by an algorithm that
performs a double check. The stored value of the angle .alpha.2,
which represents a pre-calculated optimal theoretical value of
inclination for each month, day, and time, is compared, within each
characteristic time interval tstep of the control algorithm (which
hence develops over a sequence of intervals of duration tstep),
with a value calculated as a function of the following input
variables:
[0043] i) intensity of the incident solar radiation;
[0044] ii) string current;
[0045] iii) height of the Sun;
[0046] iv) direction and intensity of the wind;
[0047] v) inclination of the structure (in particular this is the
absolute inclination of the structure with respect to the vertical
in the time interval t.sub.step in which the system reads the
variables; except for a constant value determined by the morphology
of the ground, the inclination will be equal to .alpha.2).
[0048] There then exists the possibility of correcting the pre-set
value of .alpha.2 with the value determined via the algorithm for
control of the articulated joint 22 in the case where the operating
conditions of the plant impose such a choice. It is in any case
envisaged to program the control algorithms based on a greater or
smaller number of variables (in the limit only one of the ones
above listed) as a function of the characteristics of the
installation site.
[0049] In particular, if statistically it is shown that one or more
of the aforementioned variables have a practically constant
evolution in time in a given site of installation of the
photovoltaic plant, it is possible to simplify the algorithm
eliminating the functional dependence upon the aforesaid one or
more variables.
[0050] Instead, if the five variables listed above are not
sufficient to constitute a computing model that is able to describe
fully the variability of the conditions that regard a certain
installation site, it is possible to add further variables or
replace one or more of the variables i)-v) with one or more
variables that describe in a better way evolution of the system in
which the photovoltaic plant 1 operates.
[0051] In this way, there is defined a method for orientation of
the array 4 of mobile reflection devices that comprises: [0052] a
first step of detection, within the framework of a time interval
having a predetermined duration tstep, of the values of one or more
physical quantities which are representative of operative
conditions of an installation site of the photovoltaic plant,
[0053] a second step of calculation, within the framework of the
time interval tstep, of an inclination value .alpha.2 of the array
4 as a function of the detected value of the one or more aforesaid
physical quantities, [0054] a third step of comparison of the
calculated inclination value .alpha.2 with a theoretical and
pre-calculated optimal inclination value, [0055] a fourth step of
correction of the pre-calculated theoretical optimal inclination
value with the calculated inclination value .alpha.2,
[0056] wherein the first, the second, the third and the fourth
steps are repeated along a sequence of time intervals having a
predetermined duration tstep.
[0057] It should be noted that, notwithstanding the fact that the
value of angle .alpha.2 is updated periodically via the calculation
carried out by the algorithm referred to above, having in any case
an optimal theoretical value of the angle .alpha.2 pre-calculated
and stored affords multiple advantages:
[0058] a) it accelerates the processes of search for the maximum,
i.e., for the highest energy efficiency of the plant: the value
stored constitutes a starting value around which the value of angle
.alpha.2 that corresponds to the condition of highest desired
efficiency will probably (but not necessarily--consider, for
example, variable operating conditions or operating conditions
different from the expected ones) fall;
[0059] b) on days with marked variability of weather conditions, it
prevents the system from encountering difficulties on account of
the imbalance between the time constants typical of the search for
the optimal value of .alpha.2 and the time intervals in which a
variation of the boundary conditions occurs, which will be
decidedly shorter than the aforesaid time constants; and
[0060] c) in the event of failure of one or more sensors, it
prevents faulty positioning of the reflection devices of the array
4, which may project shadows on the modules FV.
[0061] It should moreover be noted that the duration tstep can be
assumed as fixed or variable as a function of the conditions of the
installation site itself.
[0062] The variables i) to v) (but this applies in general,
whatever the number of variables that intervene in the algorithm)
are detected via corresponding sensors. The ensemble of the sensors
used for detection of the physical quantities associated to the
above variables constitutes a modular sensor system with which the
photovoltaic plant 1 is equipped. The number of the aforesaid
sensor systems varies in a way directly proportional to the
irregularity of the ground in which the plant is installed. In
other words, in the case of a perfectly plane terrain, the sensor
system equips a single array 4 of reflection devices, since the
value of .alpha.2--whether it is pre-calculated or calculated via
the algorithm described--may be deemed applicable to all the arrays
4. In the case where the ground is markedly irregular, application
of a uniform value of .alpha.2 is not generally an option that can
be pursued, and it is consequently necessary to equip all the
arrays 4 with a dedicated sensor system (or else it is possible to
divide the arrays 4 into sets according to their location on
portions of ground having locally uniform characteristics and equip
with the sensor system just one array 4 in each set).
[0063] The control unit is hence configured for sending an
actuation signal to the motor-reducer assembly integrated in the
articulated joint 22 so as to set the value of .alpha.2 calculated
via the aforesaid algorithm. This of course can be repeated for any
number of iterations each time there is an updating, by the
algorithm, of the angle .alpha.2 as time passes. In this way, the
orientation of the array 4 of mirrors RF is varied with the aim of
maximizing the amount of energy of the reflected radiation RSR
transferred to the solar panels of the modules PV of the array 2.
The angle .alpha.2 typically falls in the range 0.degree. and
90.degree.. The choice of the values in this range, as will be
appreciated, is always and in any case linked to the morphology of
the terrain.
[0064] Finally, in some cases, in particular where the morphology
of the terrain on which the photovoltaic plant 1 is installed is
exceptionally irregular, the inventors have noted that it is
convenient--at the limit--to do without the sensors, allowing the
system to follow just the pre-stored data for the angle
.alpha.2.
[0065] It is hence evident how, albeit maintaining the same basic
setting of the photovoltaic plants of a known type (wide aisles
between the arrays 2 that prevent mutual shading), the photovoltaic
plant 1 makes it possible to obtain considerable increase in
productivity as compared to photovoltaic plants of a known type in
so far as the solar radiation that in known plants would impinge on
non-productive areas--i.e., the aisles between the arrays 2--in
this case impinges upon the mobile reflection devices, which are
set precisely in the aisles between the arrays 2.
[0066] In this way, albeit minimizing the effects of mutual shading
by maintaining the arrays 2 of photovoltaic modules PV at a due
distance, the unexploited fraction of the ground on which the
photovoltaic plant 1 is installed is reduced thanks to the
association of an array 4 of mobile reflection devices to each
array 2 of photovoltaic modules, thus recovering a considerable
amount of energy that would otherwise be dispersed.
[0067] Of course, the embodiments and the details of construction
may vary widely with respect to what is described and illustrated
herein, without thereby departing from the scope of the present
invention, as defined by the annexed claims.
[0068] For instance, it is possible to envisage embodiments in
which according, for example, to the need for installation in lots
of land having a profile that to a certain extent is irregular, the
articulated joint 22 is of a multi-axial (for example, biaxial)
type so as to enable an optimal orientation of the mirrors RF with
respect to the solar panels of the array 2.
[0069] In this connection, reference may be made to FIG. 3, where a
further embodiment of a photovoltaic plant according to the
invention is designated by the reference number 1'. The components
that are identical or substantially similar to those already
described are designated by the same references. For this reason,
the description already developed as regards the plant 1 also
applies to the plant 1', except for the portions thereof that are
manifestly incompatible.
[0070] The photovoltaic plant 1' differs from the plant 1 basically
in the scheme of constraint and in the modalities of orientation of
the structure of the array 4 of mobile reflection devices, which
are here designated by the reference number 4' and are once again
located in the space comprised between arrays 2 of successive
photovoltaic modules (where this is possible--in general, the plant
1' comprises at least one array 4' located between successive
arrays 2).
[0071] In particular, the frame 18 of the array 4', which supports
the reflection devices RF, is articulated to the associated array 2
of photovoltaic modules at the respective long sides B2, B4 of each
of the arrays 2, 4'. The reference X4' designates the axis of
articulation between the two arrays 2, 4'.
[0072] The frame 18 is connected to a supporting structure 20',
which anchors and fixes the array 4' to the ground, by means of a
linear actuator AC. In particular, the linear actuator AC includes
a first end articulated at a hinge 22' (that replaces the
articulated joint 22) about an axis XRF'. A second end of the
linear actuator AC is, instead, articulated to the post 20' about
an axis XAC by means of a hinge 24'. Preferably (as in the example
of the figures), the axis XAC is located in the proximity of the
ground at the exposed end of the post 20'. The axes X4', XRF' and
XAC are all parallel to one another.
[0073] In this way, there is defined a three-hinge mechanism, which
includes two fixed hinges with axes XAC and X4' and a mobile hinge
with axis XRF'. The angle .alpha.2 is modulated (on the basis of
the criteria and the algorithm described) via variation of the
position of the axis XRF' in space. This is possible by controlling
a retraction or extraction of the stem of the actuator AC, which
results in a decrease or an increase of the distance between the
axes XAC and XRF' (the distance between the axes XRF' and X4' is
constant) and a consequent variation of position of the supporting
structure that carries the reflection devices XRF. This is also
accompanied by a variation of position of the actuator XAC, which
is possible thanks to the double articulated joint thereof. In a
way similar to what has been described for the plant 1, whatever
the variation imposed on the angle .alpha.2, it must fall in a
range such that the front surface 14 of the mirrors RF is at least
partially in view of the front surface 12 of the photovoltaic
modules PV, defining (FIG. 3) a substantially V-shaped geometry of
the ensemble constituted by an array 2 and an array 4' associated
thereto.
[0074] For this purpose, the actuator AC is operatively connected
to an electronic control unit in which the algorithm of calculation
of the angle .alpha.2 is implemented.
[0075] The actuator AC is preferably of the electromechanical type,
which can be controlled more easily and is such as to require
pre-arrangement less auxiliary equipment as compared to a hydraulic
or pneumatic actuator (which, instead, require a dedicated circuit
on which a control must in turn be implemented that will enable
modulation of the angle .alpha.2). This, however, does not rule out
the possibility of envisaging in some variants pneumatic or
hydraulic actuation.
[0076] The photovoltaic plant 1', and in particular the system for
fixing the array 4' to the ground and to the array 2, are expressly
conceived for installation on markedly irregular terrain, where it
would be disadvantageous to apply the structure of the plant 1.
[0077] Reference may now be made to FIG. 4, which illustrates a
further advantageous embodiment of a photovoltaic plant according
to the invention designated by the reference number 1'', and
basically configured as a variant of the plant 1 illustrated in
FIGS. 1 and 2. Components that are identical to those previously
described are designated by the same references, and all the
considerations already set forth in relation to the plants 1, 1'
apply--where not manifestly incompatible--also to the plant 1''.
The plant 1'' is substantially similar to the plant 1, except for
the mobile reflection devices, designated by the reference RF'',
which include a plurality of convex mirrors having a front
reflecting surface 14'' that has a curvature along a directrix
parallel to the short sides A4 and orthogonal to the long sides B4
(see in this connection the side view of FIG. 4). The radius of
curvature of the surface 14, designated by R'' in FIG. 4, has
different values, calculated each time, that are a function of the
distance of the reflecting surface from the array of modules and
from the orography of the terrain where the plant is installed.
[0078] Also in this case, the front reflecting surface 14'' of the
array 4 faces the front surface 12 of the array 2, bestowing on the
two arrays 2, 4 an arrangement with a substantially V-shaped
geometry.
[0079] Concerning operation, the incident solar radiation ISR
impinges on the reflecting surface 14'', which reflects the solar
rays in a substantially divergent beam that defines the reflected
solar radiation RSR.
[0080] The shape of the mirrors RF makes it possible to obtain a
dual advantage:
[0081] i) in the first place, the ranges of regulation of the
system (i.e., the ranges of variation of the angle .alpha.2) may be
extended in so far as the divergence of the beam of the reflected
solar radiation RSR enables the latter to impinge upon an area of
larger extent than that of the photovoltaic modules; in other
words--as compared to what happens in the case of the plant 2--the
photovoltaic modules of the array 2 will in any case be impinged
upon by the radiation RSR for a more extensive fraction of the
solar path without this requiring any correction of the angle
.alpha.2; and
[0082] ii) the times of partial shadow, which especially in winter
months, when the Sun is very low above the horizon, penalize the
performance of the system, are eliminated.
[0083] It should moreover be borne in mind that it is possible to
envisage embodiments in which convex mirrors RF'' are used in the
plant 1' (illustrated in FIG. 3) instead of the plane mirrors RF,
with advantages similar to the ones just described.
[0084] Finally, with reference to FIG. 5, as well as to FIGS.
6A-6B, yet a further embodiment of a photovoltaic plant according
to the invention is designated by the reference number 1'''. The
components that are identical to those previously described are
designated by the same references, and all the considerations
already set forth in relation to the plants 1, 1', 1'' apply--where
they are not manifestly incompatible--also to the plant 1'''. The
plant 1''' is substantially similar to the plant 1, except for the
array of mobile reflection devices, here designated by the
reference 4'''.
[0085] In particular, the array 4''' differs from what has so far
been described and illustrated as regards the mobile reflection
devices (here designated by the reference RF''') and as regards the
supporting frame (here designated by the reference 18'''). In this
embodiment, unlike the others, the reflection devices RF''' are
obtained using deformable sheets of reflecting material, for
example, thin panels of metal material (like sheet metal).
Alternatively, the reflection devices RF''' are obtained using
sheets of reflecting plastic material. The devices RF''' will hence
be referred to in the ensuing description by the term "deformable
mirrors" (for the meaning of "mirror", reference may be made to the
foregoing description).
[0086] Moreover, the frame 18''' bearing the reflection devices
RF''' is fixed and without articulations with respect to the ground
(unlike the case of the photovoltaic plants 1, 1', 1''). In this
connection, the frame 18''' has a static inclination designated by
the reference .alpha.18''' with respect to the horizontal.
[0087] Each deformable mirror RF''' includes a front reflecting
surface 14''' configured for reflecting the sunlight, and a dorsal
surface 16''', where fixing to the supporting frame 18''' is
obtained by an actuator assembly ACT and a plurality of sliding
hinges SH. In this embodiment, the supporting frame 18''' includes
two rows of supporting posts 20''' that anchor and fix the
supporting frame 18''' and the plane mirrors RF''' to the ground
G.
[0088] In this connection, it should be noted that also for the
array 4''' with deformable mirrors RF''' it is possible to identify
a pair of short sides A4''' parallel to one another and a pair of
long sides B4''' parallel to one another and orthogonal to the
short sides A4'''.
[0089] Each array 4''' is set, with respect to the associated array
2, so that the respective long sides B4''', B2 are substantially
parallel to one another and so that the long side B4''' of the
array 4''' closer to the ground G is immediately adjacent to the
long side B2 of the array 2 closer to the ground G (the side B2L),
so that each array 2 and the array 4''' of associated mobile
reflection devices are set in a V shape.
[0090] In a preferred embodiment, the supporting frame 18'''
extends so as to cover the entire length of the sides B4''' (i.e.,
the entire extension of the array 4'''), and the deformable mirrors
RF''' are then installed on the frame 18''' set side by side and
substantially without solution of continuity. In this case, also a
number of supporting posts 20''' are provided in the direction of
the length of the array 4''' given the considerable development
thereof, which is typically of the order of tens of metres (17-20
m).
[0091] The actuator assembly ACT includes a linear actuator
(electromechanical actuator, pneumatic actuator, or hydraulic
actuator according to the need) having a stem mobile along a
longitudinal axis XACT of the actuator ACT. The actuator ACT is
governed by means of a control system, the operating logic of which
will be described in the ensuing paragraphs.
[0092] The actuator assembly ACT includes a first end hinged to the
frame 18''' and a second end hinged to the dorsal surface 16''' of
the corresponding deformable mirror RF''', and in particular hinged
at the geometrical centre of the surface itself.
[0093] In an undeformed configuration (i.e., in a completely plane
configuration) each mirror RF''' has all the normals to the
reflecting surface 14''' oriented parallel to one another and
describing the angle .alpha.18''' with respect to the vertical.
[0094] The orientation of the mirrors RF''' is varied thanks to the
deformability of the mirrors themselves. In particular, each
actuator assembly ACT is able to vary the distance of the dorsal
surface 16''' from the supporting frame 18''': given that it acts
at the geometrical centre of the deformable mirror RF''', the
result is that of a variation of concavity of the mirror RF'''
itself.
[0095] The variation of orientation lies in the fact that to each
variation of concavity of the deformable mirrors RF''' there
corresponds a variation of the orientation of the normals to the
surface 14'''. Reference may be made for this purpose to FIGS. 6A
and 6B, which illustrate two different positions of the actuator
ACT corresponding to two different curvatures imparted on the layer
RF''' and, consequently, to two different orientations of the
normals to the surface 14'''.
[0096] By way of example, three straight lines normal to the
surface 14''' have been drawn (in the figure, for convenience, the
corresponding vectors are represented) choosing three points
representing the surface: the geometrical centre and two points
around it. The three normals are designated by the references n1
(normal in the geometrical centre), and n2 and n3 (normals in
lateral points with respect to the geometrical centre), and for
each of them the angle described with respect to the vertical,
respectively .alpha.n1, .alpha.n2, .alpha.n3, is indicated. The
normals n1, n2, n3 in effect define the straight lines normal to
the planes tangential to the surface 14''' in the points indicated
above.
[0097] In the condition illustrated in FIG. 6A, which corresponds
to a situation where the concavity of the deformable mirror RF'''
is very marked, the angles .alpha.n2, .alpha.n3 assume greater
values than the angle .alpha.n1, which, given that it is at the
geometrical centre (as well as on the straight line of action of
the actuator assembly ACT), always equal remains to the value
.alpha.18'''. The amplitude of the angles described by the normals
to the surface 14''' with respect to the vertical in general
increases proceeding from the centre towards the periphery of the
deformable mirror RF'''.
[0098] In the condition illustrated in FIG. 6B, the concavity is
less marked as compared to the condition of FIG. 6A (it will be
appreciated that the distance between the surface 16''' and the
frame 18''' is smaller), and the normals n2 and n3 consequently
describe angles .beta.n2, .beta.n3 smaller than the angles
.alpha.n2, .alpha.n3, but in any case wider than the angle
.beta.n1, which is always equal to .alpha.18'''. The distribution
of the amplitudes of the angles described by the normals to the
planes tangential in each point to the surface 14''' is the same as
the one already described above.
[0099] The deformations imposed on each deformable mirror RF''' by
the actuator assembly ACT are moreover such as to result in a
displacement of the ends each deformable mirror RF''' in the
direction of the short side A4. This displacement is allowed thanks
to the sliding hinges SH, which are fixed at the four vertices of
each deformable mirror RF''' (which has a quadrangular shape) and
along the sides of the mirror RF''' parallel to the long sides
B4''', so as to ensure that the curvature imparted on the
deformable mirrors RF''' by the actuator assembly ACT belongs to a
single plane (the plane of the drawing, in the example illustrated
in the figures). Moreover, the hinges SH are mounted on the frame
18''' so that they slide in a direction parallel to the short sides
A4''' of the array 4''' by means of rails fixed to the frame 18'''
and set parallel to the short sides A4'''.
[0100] Preferably, the hinges SH are provided on brackets of a
length equal to that of the sides B4''' set on the same sides,
where these brackets are mobile along the rails parallel to the
short sides A4''' (the rails can of course be set also on the sides
A4''' themselves).
[0101] Once again preferably, the cross section chosen for the
aforesaid brackets is square. In any case, the cross section of the
brackets may also have a different shape, according to the
requirements.
[0102] Variation of the concavity of the deformable mirrors RF''',
with consequent reconfiguration of the normals to the planes
tangential to the surface 14''', enables modulation of the
amplitude of the reflected beam of light RSR so that the latter
strikes the surface of the photovoltaic modules PV whatever the
angle of incidence of the solar radiation ISR. In addition, there
exists the possibility of driving in a differentiated way the sets
of actuators ACT of each array 4''', hence varying the concavity of
the mirrors RF''' in a way equally differentiated along the array
4'''.
[0103] As regards the method of regulation of the concavity of the
deformable mirrors RF''', the control system that drives the
actuator ACT includes .alpha.n algorithm that envisages imposing
successive variations searching for the optimal value of stroke of
the actuator ACT, i.e., a value of stroke of the mobile element of
the actuator ACT that imparts on the mirrors RF''' a concavity such
that the entire capturing surface of the modules FV will be
impinged upon by the reflected radiation RSR.
[0104] In particular, the algorithm carries out a search for the
operating point--i.e., the aforesaid optimal stroke of the actuator
ACT--proceeding by small increments and decrements of the stroke of
the actuator, corresponding to small increments and decrements of
the value of the concavity. In other words, movements of the
actuator ACT in opposite directions are controlled by
extraction-retraction of a stem or slider as a function of the type
of (linear) actuator ACT used.
[0105] The amplitude of each actuation may be such as to cancel the
effects of the immediately preceding actuation or actuations--for
example, in the case where it is found that actuation in one
direction does not lead to .alpha.n optimal operating condition--or
else may have a value lower or much lower than that of the
immediately preceding actuation--for example, in the case where the
operating conditions are close to the optimal conditions, and only
minor adjustments are necessary with respect to the condition
reached after .alpha.n actuation of larger extent (or after a
series of successive actuations in the same direction of a smaller
extent, even imparted in a continuous way).
[0106] The iterative process proceeds until the optimal value of
concavity is identified (corresponding to the optimal value of
stroke).
[0107] In order to implement this method, a continuous measurement
is made of the value of radiation in the proximity of the long side
B2 of the capturing surface (i.e., the surface 12 of the modules
PV), thereby meaning both the higher side (B2H) and the lower side
(B2L).
[0108] By so doing, thanks to the successive iterations, the value
of concavity will be identified such as to enable the peripheral
reflected rays RSR (those with angle of reflection of a larger
value) to fall in the proximity of (in the limit, in a point
corresponding to) the upper and lower limits of the capturing
surface (surface 12 of the modules PV), i.e., in the proximity of
(in the limit, in a point corresponding to) the long sides B2H and
B2L.
[0109] The algorithm operates on the basis of a reference value of
intensity of radiation, which corresponds to the value of the
intensity of the radiation incident on the surface of the modules
PV in the absence of a reflection system, i.e., in the absence of
radiation reflected by the array 4. This radiation corresponds to
the fraction of radiation ISR that in any case impinges upon the
photovoltaic modules PV
[0110] The method of variation of the concavity envisages
simultaneous detection of the intensities of the "basic" radiation
(ISR) and of the "optimized" radiation (incident radiation ISR and
reflected radiation RSR) at each of the two long sides B2H,
B2L.
[0111] During search for the operating point (i.e., for the optimal
concavity of the deformable mirror RF'''/optimal stroke of the
actuator ACT) there are detected the increments and decrements of
the sum of the intensities of the "basic" radiation (namely, the
incident radiation ISR alone, which would impinge in any case upon
the modules PV) and the reflected radiation RSR both along the high
side B2H and along the low side B2L.
[0112] The value of the above sum (which corresponds to the
intensity detected along the sides B2H and B2L) varies between two
limit values; namely, [0113] a lower-limit value, equal to the
value of intensity of the "basic" radiation, hence the value of
intensity of the incident radiation ISR at the respective long side
B2H, B2L; [0114] an upper-limit value, which corresponds to the
maximum value of intensity of the solar radiation that can be
detected (and is detected) at the respective long side B2H, B2L in
the current condition of irradiation of the photovoltaic plant (in
general in a given condition of irradiation); the upper-limit value
hence comprises, in addition to the value of intensity of the
"basic" radiation (ISR) at the respective long side B2H, B2L, the
maximum value of intensity of the reflected radiation RSR that can
be detected at the respective long side B2H, B2L; this maximum
value is in general specific for each side B2H, B2L and may differ
according to the different height of the sides B2H, B2L; in certain
conditions, however, the difference between the two maximum values
(one for the side B2H and one for the side B2L) may be so small
that it is possible to assume .alpha.n identical maximum value for
both of the sides, thus simplifying and optimizing the
calculation.
[0115] The system that drives the actuator ACT and receives the
signals from the sensors that detect the intensity of the solar
radiation along the sides B2H, B2L, by virtue of what has been
described above, will see .alpha.n increase in the value of the sum
of intensities of the "basic" radiation (ISR) and of the reflected
radiation (RSR). Driving of the actuator ACT is stopped when the
value of the sum returns to the base value (in other words when the
extra contribution of radiation present in the sum, due to the
radiation RSR, is seen to vanish). It is clear that, according to
the direction of actuation of the actuator ACT, there will be a
"high-to-low" or "low-to-high" sequence in the zeroing of the extra
contribution of radiation present in the sum.
[0116] In either case, the system will act on the actuator ACT so
as to bring the concavity of the deformable mirror RF''' to the
value that restores the extra contribution (due to the radiation
RSR) at both sides, automatically ensuring that this contribution
is as high as possible.
[0117] In summary, a method for variation of the concavity of the
array 4''' is thus implemented, comprising the steps of: [0118]
detecting the intensity of the solar radiation (both the incident
radiation ISR and the reflected radiation RSR, if present) at each
of the two long sides B2H, B2L of the associated array 2 of
photovoltaic modules PV; and [0119] governing a movement of the
actuator assembly ACT in order to produce a variation of concavity
of the mobile reflection devices RF''' as a function of the
detected intensity of the solar radiation,
[0120] wherein the step of governing a movement of the actuator
assembly ACT is iterated until a concavity is identified such that
the values of intensity of the solar radiation at each of the two
long sides B2H, B2L are equal to maximum values for the respective
side B2H, B2L.
[0121] This is substantially equivalent to associating the optimal
operating point of the array 4''' (hence, the optimal concavity of
the deformable mirrors RF''' and the optimal stroke of the actuator
ACT) to a condition where the peripheral rays of the reflected
solar radiation RSR are in the proximity of the long sides B2H, B2L
of the associated array 2 of photovoltaic modules PV.
[0122] Obviously, many modifications and variations of the present
invention are possible in light of the above teachings. It is,
therefore, to be understood that the invention may be practiced
otherwise than as specifically described while still being within
the scope of the invention. cm What is claimed is:
* * * * *