CROSS-REFERENCE TO RELATED APPLICATION

[001] This application claims the benefit of priority of Singapore patent application number 10202250534X filed 21 July 2022, the contents of which being hereby incorporated by reference in its entirety for all purposes.

TECHNICAL FIELD

[002] The invention relates to a light modulating device.

BACKGROUND

[003] While greenhouses may be designed to provide a conducive environment for plant growth all year round, in practice, there may be an excess amount of heat trapped in the interior during the day particularly in a hot weather environment, which may be detrimental to crop yields. This may particularly be the case for greenhouses in tropical climates, as they may trap excessive heat to result in excessive loss of moisture from plants.

[004] Even though solar shading through installation of passive solar films of the greenhouses may be carried out to counter this, such solar shading may not be desired during low light conditions or in a cold/cloudy weather, as considerable amount of light going into the greenhouses may be blocked. As such, the plants may not receive sufficient light for optimal growth.

[005] Furthermore, wide fluctuations in Photosynthetic Photon Flux Density (PPFD) from about 0 to about 2000 pmol/m ² /s may result due to weather changes. Most crops require a smaller range of 100 to 300 pmol/m ² /s to thrive optimally. This means that there is a substantial wastage of energy that is not utilized by the plants. [006] In light of the above, there exists a need for an improved light modulating device that addresses or at least alleviates one or more of the above-mentioned problems.

SUMMARY

[007] In a first aspect, there is provided a light modulating device. The light modulating device may comprise a first support comprising a first photovoltaic cell on a surface and a first light-reflector on an opposing surface, and a second support comprising a second photovoltaic cell on a surface and second light-reflector on an opposing surface. The first support and the second support may be pivotably coupled to each other along an edge portion of the respective support, and movable between a collapsed position in which the surfaces comprising the first photovoltaic cell and the second photovoltaic cell are opposed and inwardly facing and an extended position in which the surfaces comprising the first photovoltaic cell and the second photovoltaic cell lie substantially in the same plane, to modulate transmission of light.

[008] In a second aspect, an apparatus comprising light modulating device according to the first aspect is provided. The apparatus may be a window or a door.

[009] In a third aspect, a method of modulating light into a building using the light modulating device according to the first aspect is provided. The method may comprise positioning the light modulating device at a facade of the building which is adapted to allow light to pass through into the building.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily drawn to scale, emphasis instead generally being placed upon illustrating the principles of various embodiments. In the following description, various embodiments of the invention are described with reference to the following drawings.

[0011] FIG. 1 is a schematic diagram depicting front views of a light modulating device 100 according to an embodiment. In this embodiment, two supports 110 and 120 are present in the light modulating device 100. A first support 110 comprising a first photovoltaic cell 113 on a surface and a first light-reflector 111 on an opposing surface, and a second support 120 comprising a second photovoltaic cell 123 on a surface and second light-reflector 121 on an opposing surface may be present. The first support 110 and the second support 120 may be pivotably coupled to each other along an edge portion of the respective support. The first support 110 and the second support 120 may be movable between a collapsed position in which the surfaces comprising the first photovoltaic cell 113 and the second photovoltaic cell 123 are opposed and inwardly facing, such as that shown in (i), and an extended position in which the surfaces comprising the first photovoltaic cell 113 and the second photovoltaic cell 123 lie substantially in the same plane, such as that shown in (iii). At (i), angle 0 formed between the surfaces comprising the photovoltaic cell of the first support 110 and the second support 120 may be 0°, while at (iii), angle 0 formed between the surfaces comprising the photovoltaic cell of the first support 110 and the second support 120 may be 180°. The first support 110 and the second support 120 are movable between the two positions with angle 0 in the range from 0° to 180°, and may assume a position as shown in (ii), whereby angle 0 formed between the respective surface comprising the photovoltaic cell of the first support 110 and the second support 120 is 90°. Accordingly, (i) may depict a folded position of the light modulating device 100 with minimum blockage of light transmission by the light modulating device 100, and with light-reflectors 111 and 121 arranged at an exterior surface of the light modulating device 100, (ii) with the light modulating device 100 in a “V” configuration may depict the light modulating device 100 at half deployment, and (iii) may depict the light modulating device 100 at full deployment with maximum blockage of light transmission by the light modulating device 100.

[0012] FIG. 2 is a schematic diagram depicting front views of a light modulating device 200 according to an embodiment. In this embodiment, the first support 210 and 220 along with a further set of two supports are shown, i.e. four supports are present. A first support 210 may comprise a first photovoltaic cell 213 on a surface and a first light-reflector 211 on an opposing surface, and a second support 220 may comprise a second photovoltaic cell 223 on a surface and a second light-reflector 221 on an opposing surface. A third support may comprise a third photovoltaic cell 233 on a surface, and a fourth support may comprise a fourth photovoltaic cell 243 on a surface. The first support and the second support may be pivotably connected to each other along an edge portion of the respective support via the third support and the fourth support, which in turn are pivotably connected to each other. In other words, all the four supports may be pivotably connected to each other along a respective edge portion. The four supports are movable between a collapsed position in which the respective surface comprising the first photovoltaic cell 213, the second photovoltaic cell 223, the third photovoltaic cell 233, and the fourth photovoltaic cell 243 are opposed and inwardly facing, such as that shown in (i), and an extended position in which the respective surface comprising the first photovoltaic cell 213, the second photovoltaic cell 223, the third photovoltaic cell 233, and the fourth photovoltaic cell 243 lie substantially in the same plane, such as that shown in (iii). At (i), angle 0 formed between the surfaces comprising the photovoltaic cell of the first support 210 and the third support, and between the fourth support and the second support 220 may be 0°, while at (iii), the angle 0 may be 180°. The four supports are movable between the two positions with angle 0 in the range from 0° to 180°, and may assume a position as shown in (ii) whereby angle 0 formed between the respective surface comprising the photovoltaic cell of the first support 210 and the third support, and between the fourth support and the second support 220 is 90°. In other words, (i) may depict a folded position of the light modulating device 200 with minimum blockage of light transmission by the light modulating device 200 and with light-reflectors 211 and 221 arranged at an exterior surface of the light modulating device 200, (ii) with the light modulating device 200 in a “W” configuration may depict the light modulating device 200 at half deployment, and (iii) may depict the light modulating device 200 at full deployment with maximum blockage of light transmission by the light modulating device 200.

[0013] FIG. 3 is a schematic diagram depicting an array 350 of light modulating devices 300, 301, and 302 according to an embodiment, (i) shows a perspective view of an array of light modulating devices 300, 301, and 302 being arranged on a light transmitting surface 380 such as a window to a building or part of a greenhouse, while (ii) shows a front view of the array arranged on the light transmitting surface 380. Light modulating devices 300, 301, and 302 may be identical, each having four supports such as that shown in FIG. 2. Taking light modulating device 300, for example, the first support 310 and second support 320 may be pivotably connected to each other along an edge portion of the respective support via a set of two supports, which may in turn be pivotably connected to each other. In other words, all the four supports may be pivotably connected to each other along an edge portion. A first support 310 may comprise a first photovoltaic cell 313 on a surface and a first light-reflector 311 on an opposing surface, and a second support 320 may comprise a second photovoltaic cell 323 on a surface and a second light-reflector 321 on an opposing surface. A third support may comprise a third photovoltaic cell 333 on a surface, and a fourth support may comprise a fourth photovoltaic cell 343 on a surface. As shown in the figure, the four supports may be in a collapsed position in which the respective surface comprising the first photovoltaic cell 313, the second photovoltaic cell 323, the third photovoltaic cell 333, and the fourth photovoltaic cell 343 are opposed and inwardly facing. The collapsed position may depict a folded position of the light modulating devices 300, 301 and 302 with minimum blockage of light transmission by the array 350 comprising the light modulating devices 300, 301 and 302. Each light modulating device 300, 301 and 302 may be of the same length and have width x and height y. They may be spaced apart from each other by distance p. Distance p may depend on the height y of the light modulating device and number of supports comprised therein, and may be configured such that maximum light blockage or shade coverage may be obtained when the light modulating devices are in the extended positions. Depending on angle of incident light, for example, the incident light directed to light modulating devices 300, 301 and 302 may be sent directly into the light transmitting surface 380, or be reflected by the light-reflectors present on an external surface of the light modulating devices, such as that shown by the first light-reflector 311 and the second light-reflector 321, into the light transmitting surface 380. Presence of the light-reflectors may help to redirect any available light to the light transmitting surface 380, which may in turn be transmitted into the building, to maintain high light transmittance.

[0014] FIG. 4A is a photograph showing a set-up of an array of two light modulating devices according to an embodiment. Each of the two light modulating devices are formed from four supports. The light modulating devices are in the collapsed position with mirrors on an exterior surface of the device. Surfaces comprising the photovoltaic cell of the respective support form an angle 0 of about 0° therebetween.

[0015] FIG. 4B is a photograph of the set-up of an array of two light modulating devices shown in FIG. 4A, in the half deployment position with surfaces comprising the photovoltaic cell of the respective support forming an angle 0 of about 90° therebetween.

[0016] FIG. 4C is a photograph of the set-up of an array of two light modulating devices shown in FIG. 4A, in the extended position with surfaces comprising the photovoltaic cell of the respective support forming an angle 0 of about 180° therebetween. The two light modulating devices may be arranged such that they do not overlap when in the extended position, such that maximum light blockage of underlying surface may be achieved.

DESCRIPTION

[0017] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practised. These embodiments are described in sufficient detail to enable those skilled in the art to practise the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the invention. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0018] Embodiments disclosed herein relate to a light modulating device, which may be in the form of a mechanical shutter system for dynamic solar shading. The mechanical shutter system may comprise slats on a louvre-like system. By controlling the angle in which the slats are deployed, light blockage area of the slats, translating into amount of light transmission to a surface, may be controlled. The slats may be pivotally connected to each other and may be movable from a collapsed position to an extended position.

[0019] In the collapsed position, the slats may be arranged in an orientation whereby surfaces of the slats functioning as light blockage areas substantially overlap or overlap fully, so as to minimize light blockage to underlying surface. In so doing, light transmission to the underlying surface may be maximized. Conversely, in the extended position, the slats may be arranged in an orientation whereby surfaces of the slats functioning as light blockage areas do not overlap, so as to maximize area of light blockage to underlying surface. In so doing, light transmission to the underlying surface may be minimized. [0020] Photovoltaic cells may be mounted on the slats. Accordingly, besides the light modulation mentioned above, photovoltaic cells present on the slats may double up as solar energy harvesters.

[0021] Furthermore, light-reflectors such as mirrors may be arranged on an exterior surface of the light modulating device, so as to deflect and/or redirect light from the light modulating device to the underlying surface.

[0022] With the above in mind, various embodiments refer in a first aspect to a light modulating device. As used herein, the term “light modulating device” refers to a means or apparatus for controlling light intensity. For example, the light modulating device may be used to control intensity of light by reducing or increasing light blockage or shade coverage, so as to increase or decrease amount of light that reaches an underlying surface, respectively.

[0023] The term “light blockage”, otherwise termed herein as “shade coverage”, refers to obstruction of light by the device to result in shadow or shade. In other words, high light blockage by the device may translate into high shade coverage by the device. Accordingly, increased light blockage or shade coverage by the device may mean that there is reduced light transmission through the device, whereas reduced light blockage or shade coverage by the device may mean that there is increased light transmission through the device.

[0024] The light modulating device may comprise a first support comprising a first photovoltaic cell on a surface and a first light-reflector on an opposing surface, and a second support comprising a second photovoltaic cell on a surface and second light-reflector on an opposing surface.

[0025] The term “photovoltaic cell” as used herein may refer to a light absorbing material which absorbs photons and generates electrons via a photoelectric effect. The photovoltaic cell may absorb light in any wavelength, such as wavelength in the range from about 380 nm to about 750 nm. The photovoltaic cell may, for example, be a solar cell. [0026] The photovoltaic cell may be in the form of a plurality of photovoltaic cells, which may be arranged into arrays or panels. In various embodiments, the photovoltaic cell is in the form of a photovoltaic panel.

[0027] A first light reflector may be comprised on a surface of the first support which is opposed to the surface comprising the first photovoltaic cell. By the term “opposing” or “opposed to”, this means that the surface comprising the first light reflector may be oriented in a direction opposite to the surface comprising the first photovoltaic cell. Likewise, a second light reflector may be comprised on a surface of the second support which is opposed to the surface comprising the second photovoltaic cell, meaning that the surface comprising the second light reflector may be oriented in a direction opposite to the surface comprising the second photovoltaic cell.

[0028] The term “light-reflector” as used herein refers to a material that is able to return a high percentage of light that is directed to it. For this purpose, reflective surfaces such as mirrors or highly polished metallic surfaces, which are able to return at least 50% of incident light, such as at least 60%, at least 70%, or at least 80%, may be considered herein as a lightreflector. Advantageously, the light-reflectors are able to reflect available light even at low light conditions.

[0029] In various embodiments, the first light-reflector and the second light-reflector may independently be a mirror, a metallic coating, or bright anodized aluminium. In some embodiments, the first light-reflector and the second light-reflector are mirrors.

[0030] The first support and the second support may be pivotably coupled to each other along an edge portion of the respective support. As used herein, the term “pivotably coupled” may refer to two objects being connected to each other in a manner that permits pivoting movement of the supports with respect to each other. Pivotably coupling of the first support to the second support may be carried out using a connector, such as a hinge, along an edge portion of the respective support. The respective support may be pivotably coupled along at least a part of, or all of the edge portion, of the respective support. The connection may be carried out such that the respective surface comprising the photovoltaic cell on the first support and second support are able to move towards or away from each other via movement about the pivotably coupled edge portion.

[0031] The first support and the second support may be movable between a collapsed position in which the surfaces comprising the first photovoltaic cell and the second photovoltaic cell are opposed and inwardly facing and an extended position in which the surfaces comprising the first photovoltaic cell and the second photovoltaic cell lie substantially in the same plane, to modulate transmission of light.

[0032] By the term “inwardly facing”, this may mean that the surfaces comprising the first photovoltaic cell and the second photovoltaic cell are facing towards a centre portion or middle portion of the light modulating device. The surfaces comprising the first photovoltaic cell and the second photovoltaic cell may be positioned within a centre portion, while being opposed and inwardly facing in the collapsed position, such that only the surfaces comprising the first light-reflector and the second-light reflector may be seen at an exterior of the light modulating device. In this configuration, the surfaces comprising the first photovoltaic cell and the second photovoltaic cell may be at least substantially overlapping or fully overlapping, which may mean that light blockage areas of the light modulating device is minimised, so as to allow maximum transmission of light to an underlying surface.

[0033] The first support and the second support may assume an extended position in which the surfaces comprising the first photovoltaic cell and the second photovoltaic cell lie substantially in the same plane. This may mean that the first support and the second support are able to open flat while being pivotably coupled at their respective edge portions, so that an angle of 180° may form between the surfaces comprising the first photovoltaic cell and the second photovoltaic cell. In this configuration, the surfaces comprising the first photovoltaic cell and the second photovoltaic cell may not be overlapping, which may mean that light blockage areas of the light modulating device may be maximised, so as to allow minimum transmission of light to an underlying surface.

[0034] In various embodiments, the first support and the second support are pivotably coupled to each other along an edge portion of the respective support via one or more sets of two supports, such as one set of two supports i.e. two supports, or two sets of two supports i.e. four supports, or three sets of two supports i.e. six supports, or four sets of two supports i.e. eight supports, and so on.

[0035] In various embodiments, each support of the one or more sets is pivotably coupled to another support of the one or more sets along an edge portion of the respective support to form a joined support, wherein opposing edge portions of the joined support are respectively pivotably coupled to the edge portion of the first support and the edge portion of the second support.

[0036] For example, in embodiments with a set of two supports, otherwise termed herein as a third support and a fourth support, an edge portion of the third support may be pivotably coupled to an edge portion of the fourth support to form a joined support. Opposing edge portions of the joined support may respectively be pivotably coupled to the edge portion of the first support and the edge portion of the second support. In so doing, a light modulating device comprising the first support, the second support, the third support and the fourth support which are pivotably connected to each other may be formed.

[0037] As another example, in embodiments with two sets of four supports, otherwise termed herein as a third support, a fourth support, a fifth support and a sixth support, an edge portion of the third support may be pivotably coupled to an edge portion of the fourth support, an opposing edge portion of the fourth support may be pivotably coupled to an edge portion of the fifth support, an opposing edge portion of the fifth support may be pivotably coupled to an edge portion of the sixth support, to form a joined support. Opposing edge portions of the joined support may respectively be pivotably coupled to the edge portion of the first support and the edge portion of the second support. In so doing, a light modulating device comprising the first support, the second support, the third support, the fourth support, the fifth support and the sixth support which are pivotably connected to each other may be formed.

[0038] Each support of the one or more sets may comprise a photovoltaic cell on a surface, wherein in the collapsed position, the surface of each support comprising the photovoltaic cells is opposed and inwardly facing and in the extended position the surface of each support comprising the photovoltaic cells lies substantially in the same plane to the surfaces comprising the first photovoltaic cell and the second photovoltaic cell, to modulate transmission of light. Examples of suitable photovoltaic cells that may be used have already been discussed above.

[0039] As mentioned above, the surfaces comprising the first photovoltaic cell and the second photovoltaic cell may be opposed and inwardly facing in the collapsed position, meaning that they may be facing towards a centre portion or middle portion of the light modulating device, such that only the first light-reflector and the second-light reflector may be seen at an exterior of the light modulating device. In embodiments comprising further sets of two supports, the surface of each support comprising the photovoltaic cells may similarly be positioned within a centre portion and/or facing towards a centre portion of the light modulating device, such that only the surfaces comprising the first light-reflector and the second-light reflector may be seen at an exterior of the light modulating device.

[0040] Likewise, for embodiments comprising further sets of two supports in the extended position, the surface of each support comprising the photovoltaic cells may lie substantially in the same plane to the surfaces comprising the first photovoltaic cell and the second photovoltaic cell, which may mean that the respective supports are able to open flat while being pivotably coupled at their respective edge portions, so that an angle of 180° may form between the respective surfaces comprising the photovoltaic cell.

[0041] In various embodiments, the surface comprising the photovoltaic cell is arranged to form an angle in the range of 0° to 180° to a neighbouring surface comprising the photovoltaic cell. For example, the angle formed may be about 0° or about 180°, or be in the range of 45° to 180°, 90° to 180°, 135° to 180°, 0° to 135°, 0° to 90°, 0° to 45°, or 45° to 135°.

[0042] The respective support may be of substantially the same size comprise, and/or be formed of any suitable material that is able to support, or withstand mounting of, the photovoltaic cell and the light-reflector. Non-limiting examples may include wood, plastic, and metal.

[0043] In various embodiments, the photovoltaic cell may be in the form of a photovoltaic panel, such that a back portion of the photovoltaic panel may form the support for mounting of or supporting the light-reflector. In other words, the light modulating device may be formed of a first photovoltaic panel with a first light-reflector arranged on a back surface of the first photovoltaic panel, and a second photovoltaic panel with a second light-reflector arranged on a back surface of the second photovoltaic panel. The first photovoltaic panel and the second photovoltaic panel may be pivotably coupled to each other along an edge portion of the respective photovoltaic panel, and movable between a collapsed position in which the first photovoltaic panel and the second photovoltaic panel are opposed and inwardly facing, and with the first light-reflector and the second light-reflector at an exterior of the light modulating device, and an extended position in which the first photovoltaic panel and the second photovoltaic panel lie substantially in the same plane, to modulate transmission of light. [0044] To facilitate control of the supports in response to ambient light conditions, the light modulating device may further comprise a motor operable to control movement of each support between the collapsed position and the extended position for light modulation. Advantageously, the light modulating device disclosed herein may be self-powered through use of energy harnessed from the photovoltaic cells.

[0045] A photo-detector operable to determine amount of photo flux present to derive settings for configuring the light modulating device may additionally, or alternatively, be comprised in the light modulating device. For example, the photo-detector may be used to derive settings for an end user to manually control the position of each support in the light modulating device for light modulation. The photo-detector may alternatively be used to control the motor operable to control movement of each support between the collapsed position and the extended position for light modulation.

[0046] In some embodiments, the photo-detector is operable to derive settings for configuring the light modulating device to provide a Photosynthetic Photon Flux Density (PPFD) value within a range of about 50 to 500 pmol/m ² /s, such as about 80 to 400 pmol/m ² /s, or about 100 to 300 pmol/m ² /s. This may be useful when applying the light modulating device to greenhouses for achieving optimal plant growth conditions. As mentioned above, wide fluctuations in Photosynthetic Photon Flux Density (PPFD) from about 0 to about 2000 pmol/m ² /s may result due to weather changes. Since most crops require a smaller range of 100 to 300 pmol/m ² /s to thrive optimally, this means that there is a substantial wastage of energy that is not utilized by the plants. By modulating light transmittance in a wide range of about 15% to 100%, excess unused energy can be harnessed without compromising optimal PPFD for the plants. In this regard, it has been demonstrated using a light modulating device according to embodiments disclosed herein that light transmittance may be modulated in a range of about 0% to 96%, which demonstrates its potential use for harnessing excess unused energy while not compromising optimal PPFD for the plants.

[0047] Various embodiments refer in a second aspect to an apparatus comprising the light modulating device according to the first aspect. The apparatus may, for example, be a window or a door.

[0048] Depending on the size of the apparatus, a plurality of the light modulating devices may be arranged, so that the plurality of the light modulating devices may, in the extended position, work in tandem with one another to cover at least most or substantially all of an underlying surface intended for by the apparatus. In so doing, control of light transmission to the underlying surface may be achieved.

[0049] Various embodiments refer in a further aspect to a method of modulating light into a building using the light modulating device according to the first aspect.

[0050] The method may comprise positioning the light modulating device at a facade of the building which is adapted to allow light to pass through into the building. Such a facade may include, but not limited to, an opening, a window or a door.

[0051] In various embodiments, the building is a greenhouse. Advantageously, a plurality of the light modulating devices may be arranged on a side of a greenhouse, such as in a checkerboard arrangement, to modulate light into the greenhouse. Other application areas may include modulating light for indoor farms, shelters, and residential and commercial buildings for indoor comfort.

[0052] In order that the invention may be readily understood and put into practical effect, particular embodiments will now be described by way of the following non-limiting examples.

EXAMPLES [0053] A light modulating device in the form of a dynamic photovoltaic mirror shutter which is able to optimize light entry and increase modulation range while harvesting solar energy is disclosed herein.

[0054] The photovoltaic mirror shutter for optical modulation may be in the form of a mechanical shutter system for dynamic solar shading, comprising photovoltaic cells mounted on horizontal slats of a louvre-esque system, which allows light transmission to be modulated by controlling the angle in which the slats are deployed in accordance to solar irradiation intensity. The shutter may be designed to represent a louvre-esque system, with its slats bunched up in sets of 2 or 4. They may collapse together as vertical slats (perpendicular to substrate), allowing light transmission. They may be deployed as horizontal slats (parallel to substrate), blocking light transmission. Mirrors may be mounted on both sides of each set of slats to redirect any available light indoors when needed. Besides optical modulation, photovoltaic cells may be present on the slats to double up as solar harvesters.

[0055] A prototype mechanical shutter with a “W” or “V” -shaped configuration, mounted with photovoltaic modules and mirror films, is demonstrated herein to be capable of realizing higher transmittance contrast ratio and efficient solar energy harvesting in a simple method without the use of any solar tracking system.

[0056] Advantageously, the light modulating device disclosed herein is able to achieve dynamic solar shading control, which may be adaptive to climate changes. Furthermore, photovoltaic cells or solar modules may be installed on the light modulating device to harness unused photon flux. The light modulating device disclosed herein may be self-powered through use of the harnessed solar energy. Modulation range from 0% to 96% may be achieved from a light modulating device disclosed herein for all incident light.

[0057] As compared to solar tracking systems for active control of the position of solar panels to improve energy harvesting efficiency, present device is simpler and cheaper to fabricate. [0058] As compared to mechanical shutter systems, whereby realization of mechanical dynamic shading with high transmittance contrast ratio, simple design and energy efficient control is a challenge due to blockage of a certain percentage of light even when the shutter is at its fully opened state resulting from presence of the slats’ shadows, present device is able to harness solar energy more efficiency and impart better transmittance contrast (between the fully closed and opened states).

[0059] In various embodiments, a mechanical photovoltaic (PV) mirror shutter system mounted on collapsible slats is disclosed. The shutter is able to provide shading to plants during particularly hot days, energy from the sun can also be harvested to power other auxiliary requirements in the greenhouse such as watering and artificial lighting. Presence of integrated mirror films complementarily help to redirect any available light into the greenhouse during cloudy days.

[0060] The PV mirror shutter may comprise of slats which are bunched together in a louvrelike system in sets of 2 (FIG. 1) or 4 (FIG. 2). Each set may be mounted at regular intervals. In each set, the slats may be collapsible in a “W” (for the 4-slats set) or “V” (for the 2- slats set)-shaped configuration. Each slat may accommodate one PV module. Mirror films may be integrated on opposite ends of each set of slats. The slats may be bunched together vertically during lowlight/cloudy conditions as shown in FIG. 3, and 0 = 0° in FIG 1 and FIG. 2. In this configuration, the mirrors on each opposite end of each set of slats may redirect all available light into the greenhouse, regardless of the direction of incident light (FIG. 3), which ensures the indoor receiving ample PPFD for plant growth. The PV modules may not be able to harvest any solar energy in this folded state. Once conditions get sunnier and excess solar radiation is detected, the slats may open up, exposing the PV modules to light incidence (e.g. 0 = 90° in FIG. 1 and FIG. 2). However, in this partial deployment state, the mirrors may be facing downwards, away from light incidence. The mirrors may become passive components, with their role in light redirection rendered inactive. Conversely, the PV modules may be transformed from its inactive role to being actively harvesting solar energy, regardless of direction of light incidence. In its full deployment state (0 = 180° in FIG. 1 and FIG. 2), all PV modules may be parallel to the horizontal plane with maximum exposure to the sun, enabling maximum power output from the PV modules and minimising light entry indoors.

[0061] Movement of the slats may be controlled by a motor, which may drive the linkages and gears. The PV mirror shutter may also be complemented by a photo- detector, which may determine position of the slats by detecting the amount of pre-determined photon flux suitable for specific plant growth.

[0062] A PV mirror shutter prototype was fabricated, comprising 2 sets of 4 PV modules (FIG. 4A to FIG. 4C), which is analogous to FIG. 3. Each PV module had an area of 5 x 20 cm ² and thickness of 2 mm, and the whole prototype had an active area of 40 x 20 cm ² .

[0063] FIG. 4A shows the positions of the PV modules lined up almost vertically to allow light entry. Upon increasing light intensity, the slats opened up to block incoming irradiation, while improving solar harvesting, as depicted in FIG. 4B. The PV modules run at maximum capacity when the slats were open fully and light entry was at its minimum, as portrayed in FIG. 4C

[0064] Each PV module had a P _ma x of 1.3 W, as measured under AM1.5G illumination at 100 mW/cm ² . The average figures of merit of a single solar module are summarised in TABLE 1.

[0065] TABLE 1: Figures of merit for a single PV module [0066] Measurements at several angles, pertaining to the degree of opening/closing of the PV modules, were taken as well, and the PV output and transmittance values are tabulated in

TABLE 2

[0067] TABLE 2 : Tabulated results of the PV mirror shutter prototype with vertical incident sunlight (0 = 90 °). The transmittance of the various angles was estimated based on the shadow cast by the PV mirror shutter.

* The derived transmittance of 96% was a maximum value based on the assumption that the thickness of each PV module is 2 mm.

[0068] A 0 = 0° position represented the PV modules totally folded in a vertical arrangement. A full deployment of the PV modules was represented by a 0 = 180° position. As demonstrated, an increasing angle blocked an increasing amount of light illumination. Correspondingly, the Pmax increased as well, with a highest power output of 10.4 W (or 130 W/m ² considering the active area) from the prototype at the fully deployed state. At a 0 = 0° position, the mirror films were exposed to incoming sunlight ( < 90° or 0 > 90° in FIG. 3), which help to redirect the sunlight indoors. This may aid in maximising light transmission and minimising shadowing effects on the indoor plants. TABLE 3 compares the calculated transmittances of two fully folded (0 = 0°) PV shutters (with and without mirrors) at different light incident angles. The transmittance (T) was estimated based on the shadow cast by the PV shutter. [0069] TABLE 3 : Calculated theoretical maximum transmittances (T _ma x) of two fully folded/opened (0 = 0°) PV shutters (with and without mirrors) at different light incident angles 0, and theoretical minimum (Tmin) transmittance (0 = 180°). The transmittance at various light incident angles 0 were estimated based on the shadow cast by the PV shutter.

* For simplicity, it was assumed that reflectance of the mirrors is 100 %.

[0070] As seen from TABLE 3, at a sunlight incident angle 0 of 90°, 60°, 45° and 30°, the transmittance of the shutter without mirrors had a decreasing trend of 96.0 %, 81.6 %, 71.0 % and 52.7%, respectively. However, with presence of the mirrors, a transmittance of 96.0 % was maintained for all conditions. The transmittance of the two shutters at 0 = 180° was 0 %.

Therefore, as demonstrated, the light modulating device disclosed herein is able to achieve a much higher transmission contrast ratio, while establishing efficient solar energy harvesting for power generation and energy efficient dynamic solar shading.

[0071] In various embodiments disclosed herein, a mechanical shutter structure, comprising PV modules and mirrors mounted as slats, that forms a louvre-like or louvre-esque system is provided. The louvre-esque system may allow for optical modulation to control the amount of light intensity and heat entering indoors. The louvre-esque structure system may allow for optical modulation to control the amount of light intensity and heat entering indoors via mounted mirrors. The louvre-esque system that may be used to adjust an appropriate amount of PPFD entering indoors for plant growth. The louvre-esque system may be able to harvest solar energy efficiently when needed, regardless of the sun’s position. [0072] The PV modules may be configured in a “W” or “V” -shaped arrangement, with the integration of mirrors on opposite ends of each set of slats. A set of 4 (or 2) PV modules may be comprised to fold/unfold into an “W” (or “V”)-shaped shutter, with mirrors mounted on opposite ends. Mirrors may redirect available light to maximise light entry at low light conditions. The shutter may optimize light entry suitable for specific plant growth, while PV modules may harness solar energy as a secondary function. In a deployed state, bidirectional nature of the PV modules may allow solar energy harvesting regardless of the position of the sun. The PV mirror shutter may not cover the entire greenhouse. They may be placed in optimum positions (such as a checkerboard arrangement) so that there is ample sunlight reaching the crops in the greenhouse while the slats are fully deployed.

[0073] Further advantages may include adjustable PPFD; dynamic switching of transmittance with very high contrast ratio; redirection of light using mirrors to maximize transmission without the need for a solar tracker.

[0074] By “comprising” it is meant including, but not limited to, whatever follows the word “comprising”. Thus, use of the term “comprising” indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present.

[0075] By “consisting of’ is meant including, and limited to, whatever follows the phrase “consisting of’. Thus, the phrase “consisting of’ indicates that the listed elements are required or mandatory, and that no other elements may be present.

[0076] The inventions illustratively described herein may suitably be practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed herein. Thus, for example, the terms “comprising”, “including”, “containing”, etc. shall be read expansively and without limitation. Additionally, the terms and expressions employed herein have been used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the inventions embodied therein herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention.

[0077] By “about” in relation to a given numerical value, such as for temperature and period of time, it is meant to include numerical values within 10% of the specified value.

[0078] The invention has been described broadly and generically herein. Each of the narrower species and sub-generic groupings falling within the generic disclosure also form part of the invention. This includes the generic description of the invention with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

[0079] Other embodiments are within the following claims and non- limiting examples. In addition, where features or aspects of the invention are described in terms of Markush groups, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group.