Patent Description:
Although the description specifically refers to photovoltaic panels or strings, or photovoltaic cells, the present invention can also be used to test other types of objects, not necessarily photovoltaic ones. The document <CIT> is a relevant prior art.

In the sector of producing photovoltaic panels, the need to test photovoltaic panels, strings or cells before they go to market is known. This is achieved by irradiating said panels for a certain period of time, even prolonged, up to whole days, with an artificial light that simulates the conditions of exposure to natural sunlight, in order to measure characteristic parameters such as the I-V curve, for example.

To perform this type of tests, a number of solar simulator apparatuses are known, which essentially comprise a containing structure inside which an irradiation chamber is made, provided with a LED lighting plane and a rest plane directly facing the lighting plane and on which the object to be tested is disposed, on each occasion.

The lighting plane has an irradiating surface consisting of a plurality of LED boards which are suitably powered and controlled, through corresponding control boards, to generate the artificial light. The individual LEDs of each board are capable of emitting beams of light at different wavelengths in order to determine an overall radiation as similar as possible to the natural solar spectrum.

One disadvantage of known simulator apparatuses is that the LED boards, once they have been switched on, generate a considerable thermal flow which, if not properly dissipated, leads to a rapid overheating of the LED boards and therefore to a compromise in the quality of the test, caused by the distortion of the emission wavelengths of the LEDs themselves.

The same phenomenon occurs for the object of the test, be it a photovoltaic panel, string or cell which, when illuminated by the radiation produced by the LEDs, generates current, and therefore heat which, if not adequately dissipated, causes it to gradually overheat, compromising the quality of the test.

This disadvantage proves to be particularly problematic especially in tests of a continuous and prolonged duration, for example of several days, for which thermal control, especially of the irradiating surface but also of the object subjected to lighting, is essential in order to obtain reliable results.

Document <CIT> identifies a passive type thermal control solution through the use of a finned dissipation surface associated with the irradiating surface. However, this solution does not guarantee sufficient cooling efficiency, especially in the case of tests of a prolonged duration, and does not solve the problem of overheating of the object being tested.

There is therefore the need to perfect a solar simulator apparatus that can overcome at least one of the disadvantages of the state of the art.

To do this, it is necessary to solve the technical problem of guaranteeing sufficient accuracy of tests on photovoltaic panels, strings or photovoltaic cells, especially when the tests are carried out in a continuous mode, that is, for a prolonged period of time, even for whole days, without ever deactivating the irradiating surface.

In particular, one purpose of the present invention is to provide a solar simulator apparatus in which the irradiating surface can remain active in continuous mode without loss of efficiency or quality of the artificial light produced.

Another purpose of the present invention is to provide a solar simulator apparatus that allows to reduce the overheating of the object being tested, thus maintaining it at an optimal temperature.

Another purpose of the present invention is to provide a solar simulator apparatus in which the light produced by the LEDs is conveyed onto the object being tested in an optimized manner.

Irrespective of the content of this description, the invention is solely to be understood as recited in the attached claims.

In accordance with the above purposes and to resolve the technical problem disclosed above in a new and original way, also achieving considerable advantages compared to the state of the prior art, a solar simulator apparatus according to the present invention, to perform a test on at least one object, such as a photovoltaic panel, cell or string, comprises:.

In accordance with one aspect of the present invention, the apparatus comprises a first liquid cooling unit dedicated to thermally controlling the lighting unit and provided with both a heat extraction device associated with the lighting unit, and also with a connected cooling device outside the containing structure.

By doing so, the solar simulator apparatus is able to work in continuous irradiation, even for several days, while maintaining the accuracy required by this type of test. In fact, liquid cooling allows the lighting unit to be kept at a controlled temperature, preventing the LEDs from overheating, which would affect their emissive capacity in the desired wavelength ranges.

In accordance with another aspect of the present invention, the lighting unit is formed by a flat matrix of LED boards and by corresponding control boards disposed aligned at a certain distance from the respective LED boards, with the heat extraction device interposed. The distance between the LED boards and the corresponding control boards allows to create a hollow space useful for optimizing the cooling of both groups of boards.

In accordance with another aspect of the present invention, the heat extraction device comprises a plurality of cooling plates provided with delivery and return channels to convey a cooling fluid, each of the cooling plates being parallel and independent from the others and associated with a respective row of LED boards and control boards, forming a repetitive modular structure with them. This configuration, in addition to optimizing the independent heat exchange of each row of LED and control boards, allows to constructively simplify the apparatus and to make its design scalability much quicker, in case it needs to be made with different sizes. In addition to this, both the assembly as well as the maintenance or replacement of individual components are simplified.

In accordance with another aspect of the present invention, on each cooling plate there are created a first multilayer interface, to which the LED boards are attached, and an opposing second multilayer interface, to which the corresponding control boards are attached by interposing support elements. The presence of specific multilayer interfaces allows to optimize the transmission of the heat emitted by the boards and exchanged with the cooling fluid.

In accordance with another aspect of the present invention, the apparatus comprises a second air cooling unit dedicated to cooling the object and provided with a central collector equipped with diffuser elements, with a suction device associated with the central collector at the lower part, the central collector and suction device being disposed in a lower zone of the operating space, and also with an air feeding circuit connected to the central collector and to an air conditioning device disposed outside the containing structure. The second cooling unit therefore allows to keep the temperature of the object controlled and managed while the test is performed.

In accordance with another aspect of the present invention, the rest plane is formed by a frame having a plurality of sustaining bars on each of which one or more support elements are mounted, able to be selectively positioned along a length of the sustaining bars. The presence of selectively positionable support elements allows to vary the size of the actual rest plane where the object to be tested is placed depending on the sizes of the latter.

In accordance with another aspect of the present invention, the support elements are provided with a conical end configured to define a resting point for the object. The punctual resting point that is thus created allows to minimize the thermal bridge between the object and the rest plane, and therefore to maximize test accuracy.

In accordance with another aspect of the present invention, the rest plane is disposed at a distance from the flat matrix of LED boards such as to optimize a distance between the latter and the object, such distance being comprised between approximately <NUM> and <NUM>, depending on different conditions. This distance allows to obtain an overall radiation as similar as possible to actual solar radiation, guarantee irradiation uniformity over the entire test area, guarantee the maximum accuracy of total spectral uniformity over the entire test area, and allow efficient thermal control.

In accordance with another aspect of the present invention, the containing structure is formed by a plurality of perimeter walls, on the external and internal surfaces of which there is applied a layer of matt black paint.

In accordance with another aspect of the present invention, the irradiation chamber is defined by a sub volume of the operating space comprised between the lateral perimeter walls, the lighting plane and the rest plane, wherein on the internal surfaces of the lateral perimeter walls there are installed mirrors facing the irradiation chamber. This also allows the "lateral" LED radiation to be efficiently conveyed toward the object being tested, instead of dispersing it to the outside.

We must clarify that the phraseology and terminology used in the present description, as well as the figures in the attached drawings also in relation as to how described, have the sole function of better illustrating and explaining the present invention, their purpose being to provide a non-limiting example of the invention itself, since the scope of protection is defined by the claims.

With reference to <FIG> and <FIG>, a solar simulator apparatus <NUM>, according to the present invention, hereafter apparatus <NUM>, comprises a containing structure <NUM>, advantageously of a box-shaped type, having an internal operating space <NUM> in which there is defined, in an upper zone, an irradiation chamber <NUM> equipped with a LED lighting unit <NUM>.

The containing structure <NUM> is formed by a plurality of perimeter walls <NUM> that define the operating space <NUM> and allow to insulate the irradiation chamber <NUM> with respect to the outside, in order to obtain the optimal conditions to carry out the test.

Optionally, one or more of the lateral walls <NUM> can be provided with ventilation apertures <NUM> in order to allow further evacuation of the heat produced within the operating space <NUM> during operation.

The apparatus <NUM> also comprises a horizontal rest plane <NUM> associated with the containing structure <NUM> and configured to support an object O, which can be chosen from a photovoltaic panel, or a photovoltaic string or cell, to be tested. <FIG> shows an example of a photovoltaic panel disposed on the rest plane <NUM>.

The rest plane <NUM> is selectively movable, relative to the containing structure <NUM>, between a loading/unloading position in which it is located outside the operating space <NUM> and ready to receive the object O, or return it at the end of the test, and a testing position (<FIG>) in which it is located inside the operating space <NUM>, facing the lighting unit <NUM> at the lower part.

The rest plane <NUM> is mounted on a slider <NUM> that allows it to be inserted into, and extracted from, the operating space <NUM> in a transverse direction T, through an aperture <NUM> with a rectangular section made in a lateral perimeter wall 20a of the containing structure <NUM>.

Optionally, the aperture <NUM> can be provided with a wider section zone suitable to allow the insertion of a support kit to be mounted on the rest plane <NUM>, dedicated to tests on photovoltaic strings and cells, which have much smaller sizes than those of a panel.

When the rest plane <NUM> is in the testing position, it delimits the irradiation chamber <NUM> at the lower part, which is therefore defined by the volume of space comprised between the lateral perimeter walls <NUM>, the lighting unit <NUM> and the rest plane <NUM> on which the object O is disposed. When the rest plane <NUM> is in the testing position, the irradiation chamber <NUM> is completely defined and insulated with respect to the outside.

According to one aspect of the invention, the apparatus <NUM> comprises a first liquid cooling unit <NUM> dedicated to the thermal control, that is, the cooling, of the lighting unit <NUM>.

With particular reference to <FIG> and <FIG>, the first cooling unit <NUM> is provided with both a modular heat extraction device <NUM> disposed in contact with the lighting unit <NUM> and provided with channels, or conduits, <NUM> (<FIG>) for the confined conveyance of a cooling liquid, and also with a connected cooling device <NUM> (schematized in <FIG>) disposed outside the operating space <NUM>, that is, the containing structure <NUM>, and configured to receive the cooling liquid, condition its temperature in a managed manner, and send it back to the heat extraction device <NUM>.

According to some embodiments, the lighting unit <NUM> is formed by a flat matrix of LED boards <NUM>, each provided with its own LEDs <NUM> capable of emitting light beams on different wavelengths, and defining overall a lighting plane <NUM> that delimits the irradiation chamber <NUM> at the upper part. Corresponding control boards <NUM> are disposed aligned and facing at a certain distance from the respective LED boards <NUM>, defining with them a hollow space which, as will be explained below, is dedicated to the installation of the heat extraction device <NUM>.

The configuration of the lighting unit <NUM> with the lighting plane <NUM> distanced from the control boards <NUM> advantageously allows to limit the overheating of the LED boards <NUM> and, as will be explained below, to also facilitate and optimize the heat exchange operated by the heat extraction device <NUM>.

The heat extraction device <NUM> is disposed between the lighting plane <NUM> and the control boards <NUM>, and comprises a plurality of cooling plates <NUM> inside which the cooling liquid is made to flow, and each one is associated with a single row of LED boards <NUM> and control boards <NUM>.

The cooling plates <NUM> are essentially defined by an extruded profile in metal material, preferably aluminum.

The cooling plates <NUM> are parallel to each other and independent, and each one of them is associated with a respective row of LED boards <NUM> and control boards <NUM>.

The individual cooling plates <NUM> are mounted on respective racks <NUM> connected to each other and attached to the perimeter walls <NUM> of the containing structure <NUM>.

In other words, as can be seen in <FIG>, a repetitive and modular structure is created, consisting of a rack <NUM> on which a corresponding cooling plate <NUM> is mounted, in which a row of LED boards <NUM> and an opposing row of respective control boards <NUM> are attached on the cooling plate <NUM>.

The cooling therefore occurs through heat exchange between the boards <NUM>, <NUM> and the cooling liquid flowing inside the cooling plates <NUM>, which heats up by absorbing heat and removing it from the boards <NUM>, <NUM>. The cooling liquid is then regenerated, cooling it by means of the cooling device <NUM>, and continuously reintroduced into the cooling plates <NUM> at a delivery temperature of around <NUM>, with a volumetric flow rate of about <NUM> liters/min and a pressure of about <NUM>-<NUM> bar.

With reference to <FIG> and <FIG>, each cooling plate <NUM> is provided with at least two channels <NUM>, of which a first channel, or delivery channel (or return channel, in an alternative configuration), 18a and a second channel, or return channel (or delivery channel, in an alternative configuration), 18b, which terminate in correspondence with two opposing ends 28a, 28b of the cooling plate <NUM>, where there are respective inlet <NUM> and outlet <NUM> connectors screwed to a ring nut <NUM>.

Between the first channel 18a and the second channel 18b there is a hollow space, which in the example of <FIG> is configured as a further channel 18c, having the function of laterally distancing the first and second channel 18a, 18b, preventing an unwanted thermal exchange between the two flows of cooling liquid flowing inside them.

According to some embodiments, the feed and extraction of the cooling liquid occur through the inlet <NUM> and outlet <NUM> connectors present in correspondence with a first end 28a of the cooling plate <NUM>, while on the other side the two channels 18a, 18b are fluidically connected to each other through a recirculation pipe <NUM> (<FIG>) connected to the inlet <NUM> and outlet <NUM> connectors present in correspondence with an opposing second end 28b of the cooling plate <NUM>. Therefore, the cooling liquid travels a delivery and return segment in opposing directions according to a U-shaped path.

The inlet <NUM> and outlet <NUM> connectors of the cooling plates <NUM> from which the feed and extraction of the cooling liquid occur are all fluidically connected, through a special circuit, to the cooling device <NUM> (<FIG>).

It is clear that the symmetry of the cooling plates <NUM>, given by the presence of the inlet <NUM> and outlet <NUM> connectors on both their ends 28a, 28b, also allows to create different feed/extraction paths of the cooling liquid.

With reference to <FIG>, on each cooling plate <NUM> there are created a first multilayer interface <NUM>, to which the LED boards <NUM> are attached, and an opposing second multilayer interface <NUM>, to which the corresponding control boards <NUM> are attached by means of the interposition of support elements, or spacers, <NUM>.

The first interface <NUM> is attached to the wall of the cooling plate <NUM> and comprises a sandwich consisting of a layer of thermal paste, an attachment plate for the LED boards <NUM> and a mat made of thermal material that constitutes the outermost layer to which the LED boards <NUM> are attached.

The second interface <NUM> is attached to the wall of the cooling plate <NUM> which is opposite the one that has the first interface <NUM>, and comprises a layer of thermal paste on which there is attached an attachment plate for the control boards <NUM>, a further layer of thermal paste on which the support elements <NUM> are attached, and a mat made of thermal material that constitutes the outermost layer to which the control boards <NUM> are attached.

Such a configuration of the first cooling unit <NUM> advantageously allows to achieve an optimized thermal control of both groups of LED <NUM> and control <NUM> boards, since the heat exchange is dual and differentiated on two distinct and dedicated interface surfaces <NUM>, <NUM>. In particular, the thermal control on the LED boards <NUM> guarantees that, at steady state, the LED boards <NUM> never exceed a threshold temperature that would affect their correct operation.

According to some embodiments, which can be combined with the embodiments described above, with reference to <FIG>, the apparatus <NUM> comprises a second air cooling unit <NUM>, dedicated to cooling the object O during the execution of the test.

The second cooling unit <NUM> is provided with a central collector <NUM> equipped with diffuser elements <NUM> which is disposed in a lower, or bottom, zone of the operating space <NUM>, an air feeding circuit <NUM> connected to the central collector <NUM> and to an air conditioning device <NUM> disposed outside the containing structure <NUM>, and a suction device <NUM> associated with the central collector <NUM> at the lower part to convey a return air flow outward.

The central collector <NUM> is disposed below the rest plane <NUM>, when the latter is in the testing position, so as to convey a flow of delivery air at a controlled and adjustable temperature toward a lower surface of the object O disposed on the rest plane <NUM>.

In other words, the object O disposed on the rest plane <NUM> faces the lighting unit <NUM> with its upper surface and the central collector <NUM> with its opposing lower surface, net of the contact points required to support it.

The central collector <NUM> is substantially configured as a parallelepiped-shaped conduit with closed ends, provided with an upper wall 37a where the diffuser elements <NUM> are installed and two opposing lateral walls 37b where one or more air inlet pipes <NUM>, forming part of the feeding circuit <NUM>, are connected.

In an example embodiment, the central collector <NUM> is served by <NUM> air inlet pipes <NUM>, two for each longer lateral wall 37b, and is provided with a certain number of diffuser elements <NUM> equally spaced apart over the length of the central collector <NUM>.

According to some embodiments, both the central collector <NUM> as well as the air inlet pipes <NUM> of the feeding circuit <NUM> can be insulated in order to prevent heating of the incoming air flow that has to be directed toward the object O.

The delivery air flow, arriving from the air conditioning device <NUM> with an approximate temperature of around <NUM>, enters through the air inlet pipes <NUM> into the central collector <NUM> and exits in a directed manner from the diffuser elements <NUM> toward the object O which, continuously and at steady state, is able to remain at an optimal temperature of about <NUM>. The return air flow is then drawn in by the suction device <NUM> and conveyed outward in order to be reprocessed by means of the external conditioning device <NUM> and reintroduced into the air feeding circuit <NUM>.

According to some embodiments, which can be combined with all the embodiments described above, with reference to <FIG> and <FIG>, the rest plane <NUM> is formed by a frame <NUM> comprising a plurality of sustaining bars <NUM> parallel to each other. The sustaining bars <NUM> are connected to two opposing head bars <NUM> (<FIG>).

One or more support elements <NUM>, configured to define a resting point for the object O, are preferably mounted on each sustaining bar <NUM>.

The support elements <NUM> are selectively positionable, by making them slide, along the sustaining bars <NUM> to define a rest plane with a sufficient size to stably sustain the object O. In this way, it is possible to easily and quickly adjust the disposition of the support elements <NUM> so as to adequately support panels and, by means of a suitable kit, also strings or cells with a variable shape not known a priori.

The support elements <NUM> are provided with a conical end 46a able to minimize the thermal bridge between the object O and the rest plane <NUM>, and thus maximize the test accuracy.

The support elements <NUM> are made of matt black polymeric material with low thermal conductivity.

According to some embodiments, which can be combined with all the embodiments described above, the rest plane <NUM> is located at a distance H from the lighting plane <NUM> such as to optimize the distance between the latter and the object O to be irradiated, so as to have an overall radiation as similar as possible to actual solar radiation, and at the same time allow efficient thermal control.

The distance H is comprised between about <NUM> and about <NUM>.

According to some embodiments, which can be combined with all the embodiments described above, a layer of matt black paint is applied to the external and internal surfaces of the perimeter walls <NUM> of the containing structure <NUM>.

In particular, the layer of matt black paint on the internal surfaces has the function of minimizing radiation reflection, and is applied on all the surfaces where reflection is unwanted, and instead maximum absorption and emissivity is desired. Instead, the layer of matt black paint on the external surfaces allows to maximize the emissivity toward the outside, thus allowing a greater dissipation of the heat generated inside, as well as a more accurate infrared thermography, which yields more precise temperature values by scanning surfaces with high emissivity values.

According to some embodiments, which can be combined with all the embodiments described above, with reference to <FIG>, <FIG> and <FIG>, mirrors <NUM> are installed on the lateral surfaces of the irradiation chamber <NUM> to efficiently convey the light radiations emitted by the LEDs <NUM> toward the object O, which would otherwise be dispersed in the lateral direction.

According to some embodiments, each mirror <NUM> can be provided with a curved border 47a to guarantee maximum continuity of reflection in correspondence with the edges, as in <FIG>.

An optional mirror can be installed orthogonally to the rest plane <NUM> so as to cover the zone with the wider section which is suitable to allow the insertion of a support kit dedicated to tests on photovoltaic strings and cells, which have much smaller sizes than those of a panel.

The apparatus <NUM> is also equipped with a control unit operatively connected to the lighting unit <NUM>, the first cooling unit <NUM> and the second cooling unit <NUM>, and overall manageable via a user interface. The control unit can also be operatively connected to optional instrumentation such as, for example, brightness, temperature or other sensors disposed inside the irradiation chamber <NUM>.

It is clear that modifications and/or additions of parts may be made to the apparatus <NUM> as described heretofore, without departing from the field and scope of the present invention, as defined by the claims.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art will be able to achieve other equivalent forms of solar simulator apparatus, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

Claim 1:
Solar simulator apparatus (<NUM>), to perform a test on at least one object (O), such as a photovoltaic panel, cell or string, said apparatus comprising:
- a containing structure (<NUM>) having an operating space (<NUM>) defining an irradiation chamber (<NUM>) equipped with an LED lighting unit (<NUM>),
- a rest plane (<NUM>) for said object (O), associated with said containing structure (<NUM>), said rest plane (<NUM>) being able to be selectively positioned facing said lighting unit (<NUM>),
characterized in that it comprises a first liquid cooling unit (<NUM>) to thermally control said lighting unit (<NUM>), wherein said cooling unit (<NUM>) is provided with both a modular heat extraction device (<NUM>) disposed in contact with said lighting unit (<NUM>) and provided with channels, or conduits, (<NUM>) for the confined conveyance of a cooling liquid, and also with a connected cooling device (<NUM>) outside said containing structure (<NUM>), configured to receive the cooling liquid, condition its temperature and send it back to the heat extraction device (<NUM>).