Patent Application
20240413784
The present invention relates to the technical field of optical systems, more specifically to the technical field of optomechanical systems and control systems thereof to regulate light transmission and electricity production as well as to control synchronization of one or more optomechanical systems. More precisely, the present invention relates to optomechanical systems and control systems thereof, which allow for high efficiency conversion of light energy of direct incident light or transmission of the diffuse incident light to match the requirements for growing conditions of plants underneath the optomechanical system. Such optomechanical systems can in particular be used in an advantageous way in the construction of solar panels with adjustable transparency for the field of agrivoltaics.
More and more, photovoltaic plants and agriculture are competing for land usage. Due to their relatively low energy conversion yield, both processes require very large open spaces with similar features such as decent amount of solar irradiance, relatively flat ground with minimal shading or obstacles, reasonable proximity with urban areas to alternatively produce electricity or grow food. Therefore, there is a strong incentive for an invention allowing both activities to take place on the same land.
Furthermore, there is an interest in producing renewable electricity locally which can be used in energy intensive agricultural processes. For instance, the energy can be used to power heating or cooling systems, pumps for irrigation, etc.
Additionally, reducing the amount of direct incident light on the crops in warmer climates can also decrease their irrigation needs. On a greenhouse, decreasing the irradiance can reduce or even remove the need for cooling systems.
Installing conventional silicon photovoltaics (PV) modules above crops or greenhouses is one solution. Conventional PV modules are very cheap and can be produced in mass. They are, however, completely opaque and therefore shade the plants placed below them if they are not sufficiently spaced. Nevertheless, spacing them apart is not very effective, as it results in a decrease of the electricity production, as well as in a non-homogeneous illumination of the crops, with shadows moving throughout the course of the day. In this manner, the land may be shared but the overall utilization of sunlight per unit area is not significantly increased.
Another solution is to use translucent solar cells, such as organic cells, which can provide high level of translucency, specifically high light transmission. However, these technologies typically achieve very low efficiencies—well below 10%—and suffer from stability issues when exposed to harsh environments.
Alternatively, the solar modules can be mounted on a rotating sun tracker, which are typically mounted in such a way to rotate the modules along either the east-west and/or the north-south axis. The amount of light impinging on the crops below the solar module can be adjusted by rotating the tracker in order to move the solar module shadow towards or away from the crops. The orientation control of the solar modules are known as solar tracking by means of a tracking system. This tracking system can effectively adjust the amount of light provided to the crops by either exposing the crops to full sunlight or to shadow. However, no intermediate illumination is provided. Moreover, in order to efficiently shade the crops below them, the trackers must typically have a wide angular range in particular at least +/−60°, which requires significant spacing between rows of trackers, as well as sufficient height to avoid impeding the agricultural work below by either men or machines. Due to their size and weight these systems are not compatible with greenhouse structures or rooftop installations. Additionally, due to the large spacing between rows of trackers, the crops are poorly protected from harsh weather events such as heavy rain and/or hail.
For the above reasons, there is a need for an optomechanical system and a tracking system, which allow for high efficiency conversion of light energy and adjustable light transmission to match the amount of daylight required by the plants beneath, wherein the tracking system moves only within a limited volume, in order to track the apparent movements of the sun while still ensuring compatibility with typical agronomic structures such as greenhouses, plastic tunnels or roof gardens.
Thus, the object of the present invention is to propose new optomechanical systems and tracking systems for converting and transmitting light energy, in which the above-mentioned drawbacks of the known systems are completely overcome or at least greatly diminished.
Objects of the present invention are in particular to propose an optomechanical system including at least one optical layer and one light collection layer with photovoltaic cells and a low-profile, low-deflection tracking system to control the collection and transmission of direct sunlight, thanks to which it is possible to control the amount of sunlight collected to produce electricity and the amount of sunlight transmitted to the crops beneath for photosynthesis in a finely regulated manner.
Specifically, the invention enables a precise control of light transmission to match the requirements of the crops growing underneath the installed optomechanical system. The precise control of light transmission through the optomechanical system can be adjusted continuously and instantaneously based on various types of manual inputs of an end-user, or automatically based on a schedule or a light control algorithm with various input parameters. Such parameters including—but not limited to—temperature, humidity, irradiance, daily light integral, electrical power, electrical current or voltage, can be used to finely adjust the balance between the amount of light energy used for power generation and the amount of light energy transmitted to the crops.
Furthermore, the invention enables to precisely control the amount of light converted into electricity at any time. By increasing the amount of light transmission for lighting, the amount of light focused on the photovoltaic cells is reduced. In order to advantageously balance the load of an electric grid, it is preferable to produce more energy at times of higher demands such as in the morning and in the evening. Another advantage of the energy production adjustment is that the produced energy can be injected into the electrical grid when energy prices are higher.
By providing a relatively low amplitude of movement, the optomechanical system is compatible with many types of agrivoltaic installations and setups. For example, the optomechanical system can replace plastic tunnels above line cultures such as berries, or it can be integrated directly into greenhouse roofing, or mounted onto rooftop structures to combine urban farming and energy conversion.
According to the present invention, these objects are achieved in particular through the subject-matters of the inventions described herewith. Further advantageous embodiments arise from the description. Features disclosed herein in different embodiments can also be combined easily by a person who is skilled in the art.
In a first aspect, the objects of the present invention are achieved by an optomechanical system for converting light energy, specifically to convert or transmit the light energy of a direct component of incident light such as sunlight while transmitting a diffuse component of the incident light through the optomechanical system and means to regulate light transmission and electricity production. The optomechanical system to regulate light transmission and electricity production, in particular in the field of agriculture, comprising
Of course, the optomechanical system of the invention also comprises a static structure, anchored to the ground, to which the optical arrangement and/or the light collection arrangement is attached. This static structure serves as a basis for physically supporting the optomechanical system and its components.
Thanks to the present invention, it is possible to efficiently convert light energy of the direct component of the incident light such as sunlight into electricity while transmitting at least a part of the diffuse component of the incident light through the optomechanical system. The combination of an optical layer designed to concentrate at least part of incident light onto respective light collection elements and a low-profile and low-deflection tracking system to control the collection and the transmission results in an effective optomechanical system.
The energy generation due to light collection by the photovoltaic cells depends on the amount of incident light which changes over the day depending on the movement of the sun relative to the optomechanical system. The tracking system of the optomechanical system can be used to move either the optical arrangement or the light collection arrangement in order to modulate and control the amount of light energy converted by the photovoltaic cells and the amount of light transmitted through the system. In particular, with the tracking system configured as a single-axis or a dual-axis tracking system, it is possible to place the photovoltaic cells always at the most favourable position relative to the optical elements of the optical arrangement to maximize the production of energy.
It is important to understand that the centralized tracking system can be used as well to maximize the amount of transmitted light through the optomechanical system and therefore to maximize the amount of light impinging on the plants placed below the optomechanical system in order to favour their growth. In particular, the centralized tracking system can be used to move the optical arrangement and the light collection arrangement relatively in order to intentionally misalign the optical layers relative to the light collection layers, and to transmit a greater amount of light than the sole amount of the diffuse component of the incident light to the plants. This is favourable when the plants need more irradiance than that of the diffuse sunlight alone over the day. In particular, when the sun is low, this option is advantageous. Balancing the amounts of the two possibilities to use the sunlight provides the mentioned advantages. Therefore, the centralized tracking system is programmable to follow not only the movements of the sun throughout the sky but to adjust the amount of electricity production and light transmission. More generally, the optomechanical system can provide a programmable centralized tracking system configured to misalign the optical arrangement relative to the light collection arrangement at any time during the day, e.g. based on manual inputs or feedback of one or more sensors. Specifically, the optomechanical system according to the present invention provides precise control of the amount of transmitted light to match requirements of the plants or crops growing underneath.
Advantageously, the amount of transmitted light can be adjusted almost instantaneously by an end-user or automatically based on various feedbacks and/or parameters. These parameters are for example a daily light integral requirement of the crops or plants, an irradiance level above or below the optomechanical system, an ambient temperature, relative humidity and/or any combination thereof. These parameters can be used as input parameters to a light control algorithm usable for the automatic control of the amount of transmitted light.
In a preferred embodiment of the present invention, the at least one guiding element is configured to guide the movement of the optical arrangement or the light collection arrangement along a circular or a quasi-circular trajectory, such as a paraboloid trajectory, while suppressing any relative rotation between the optical arrangement and the light collection arrangement. A curved displacement trajectory can be advantageous to increase the efficiency and/or angular acceptance of the optomechanical system.
In a preferred embodiment of the present invention, the guiding elements are capable of guiding the movement of the optical arrangement relative to the light collection arrangement and capable of supressing relative rotations between the optical layer arrangement and/or the light collection arrangement. More specifically, the at least one guiding element can be designed as a double low-friction hinge for a single-axis movement, and/or as double universal joint and/or as double ball-joint for a dual-axis movement. By limiting the degrees of freedom of the translated elements, e.g. the optical arrangement and/or the light collection arrangement, the relative position of the optical arrangement and the light collection arrangement can be accurately adjusted by the tracking system and more specifically rotations can be avoided or minimized. This is important since any minimal rotational movement between any pair of optical layer and light collection layer decreases the output power and light transmission capability of the system.
Alternatively, the at least one guiding element can be designed as a flexible guiding element. Guiding based on mechanical deformation is advantageous for mechanical systems requiring high reliability and long lifetime. Furthermore, the precision of flexible guiding elements in carrying out small displacements without involving friction or wear qualify them for the optomechanical system.
The low-friction hinges can be foreseen as integral parts of the optical arrangement with the plurality of optical layers. In a preferred embodiment, the at least one guiding element is attached directly to the optical arrangement or the light collection arrangement, in particular between an optical layer and a light collection layer. The direct mechanical link provided by these guiding elements ensures an accurate positioning of the two layers relative to each other. The positioning of any pair of layers ensures that at least one photovoltaic cell lies in a focal point or spot location of a corresponding optical element of the optical layer independently of the angle of incidence of the direct incident light. The hinges can be directly attached to the optical arrangement or the light collection arrangement for example as being accommodated and held through holes machined in one of the arrangements ensuring an accurate positioning. In an embodiment, the at least one guiding element can be designed as a rail and can be configured to guide the movement of the optical arrangement or the light collection arrangement along a trajectory in a plane. Such a configuration is advantageous in that it allows for a precise movement without using a lot of force.
In another preferred embodiment of the invention, the light collection layer is indirectly attached to a corresponding optical layer by means of the guiding elements and an intermediate frame element. In this embodiment the optomechanical system comprises a frame, wherein multiple optical layers and/or multiple light collection layers are attached together by the frame or attachment element, and wherein the at least one guiding element is connected to the frame or attachment element on one end, and to the optical arrangement or the light collection arrangement on the other end. The frame can be seen as a platform which would hold the elements of the optomechanical system together and may serve as an interface between the optomechanical system and the tracking system. The dimensions of the frame could be selected so that it would not bend under the weight of the tracking system and the optical layers, but would also supply a larger part for attachment of the tracking system and/or guiding elements.
In yet another embodiment of the present invention, the centralized tracking system is configured as a single axis or a dual-axis tracking system to which the optomechanical system is attached. Therefore, the tracking system is provided to displace the optical arrangement, the light collection arrangement, or the frame along at least one axis, preferably along two axes through tracking means.
Advantageously, the centralized tracking system further comprises at least one actuator and a control system such that the optical arrangement or the light collection arrangement or even the frame can be moved in one or more degrees of freedom in a translational movement. Higher degrees of freedom in translation allows for increasing the accuracy and sensitivity of the optomechanical system, so that energy generation or light transmission can be optimized.
In one preferred embodiment of the present invention, the centralized tracking system comprises at least one elongated rod as a translation element connected to one or more of the optical layers or the light collection layers, such that the movement of the rod results in a relative translation between the optical arrangement and the light collection layers, for example either by pushing or pulling, or via a rack and pinion system. In this embodiment, double ball joint elements can be used as connecting elements. In this manner, the translation of the rod is translated into a quasi-circular trajectory of the elements of the optomechanical systems. At least one actuator creates a translation of the elongated rod either by directly pushing or pulling on it, or via a rack and pinion system which translates the rotation of the actuator into a translation of the rod. The at least one actuator is controllable by a control system to adjust the relative position of the optical arrangement and the light collection arrangement, in order to finely control the amount of light harvested by the light collection arrangement to produce electricity and the amount of light transmitted through the light arrangement to the crops. The at least one elongated rod can in particular run along at least one axis below the light collection arrangement.
In another embodiment of the present invention, the centralized tracking system is designed as a cable and pulley system, such that pulling the cable in either direction results in a relative translation between the optical arrangement and the light collection arrangement. The cable and pulley system can be connected by at least one connecting element to each optical layer of the optical arrangement or each light collection layer of the light collection arrangement. The translational movement is guided on a trajectory set by the guiding elements. In a further preferred embodiment of the present invention, the cable and pulley system is actuated by at least one actuator which is configured to wind and unwind the cable to produce a translation movement in either directions.
In another embodiment of the present invention, the centralized tracking system is configured as a pulley and belt system. The pulley and belt system can be connected by at least one connecting element to the optical arrangement or the light collection arrangement such that moving the belt in either direction results in a relative translation between the optical arrangement and the light collection arrangement. The pulley and belt system is configured to transfer movement from a rotating pulley to the belt such that the translation of the optical arrangement or the light collection arrangement is provided. The pulley and belt system can be adapted to the requirements of the optomechanical system, in particular by choosing a suitable pulley diameter and/or a suitable belt length in relation to the force required to actuate the system and the required stroke on each axis.
In another preferred embodiment of the present invention, the centralized tracking system is configured as a rod assembly system with at least one rotation axis activated by at least one actuator and at least one connecting rod, preferably a plurality of connecting rods, arranged to connect the rotation axis with the optical arrangement or with the light collection arrangement. By rotating the rotation axis in either direction, the rotation thereof is transformed into a translation between the optical arrangement and the light collection arrangement due to the connecting rod. The rotation of the rotation axis can be activated and controlled by the at least one actuator arranged at one end of the rotation axis.
In certain embodiments of the present invention, at least one actuator is configured to control the relative translation movement of the optical arrangement with a plurality of optical layers or the light collection arrangement with a plurality of light collection layers including the elongate photovoltaic cells. The at least one actuator may be an electro-mechanical actuator, an electro-static actuator, a piezo-electrical actuator, a sick-slip actuator, or a pneumatic actuator.
According to an aspect of the present invention, the optomechanical system comprises multiple modules including each an optical layer and a correspondent light collection layer forming the optical arrangement and the light collection arrangement which are moved relative to each other by the centralized tracking system with one actuator. The movement of the multiple modules must be synchronized to ensure a precise positioning of each light collection layer with reference to its corresponding optical layer and vice versa.
In one preferred embodiment of the present invention, wherein the multiple modules are connected by connecting elements to the translation elements such as a common cable, belt or rod of the centralized tracking system actuated by one single actuator, the connecting elements configured to automatically detach from the centralized tracking system above a certain level of force or at a predefined position, for instance when they reach a mechanical stop. In this embodiment the connecting elements can be designed as a hinge incorporating a clamping mechanism that unclamps automatically from the common cable, belt or rod when the modules reach a predefined position or a predefined level of force. For example, when the tracking means are pulled continuously by the at least one actuator in one direction, the clamping mechanism of each module opens at a defined inclined position of the connecting element, such that each module, in particular each pair of optical layer and light collection layer, has the same predefined position. Each module stuck in the predefined position until the at least one actuator reverses the movement of the translation elements. Thanks to this system multiple modules of the optomechanical system connected together by the tracking means such as a common cable, belt, or rod, can take the same position in a synchronized manner. This embodiment is advantageous to ensure a coordinated movement and accurate positioning of all modules connected to the centralized tracking system.
The connecting element can be configured in different ways to provide a clamping mechanism or clutch mechanism. In one preferred embodiment of the present invention, the clamping mechanism is configured such to open the connection or attachment to the common cable once a certain position is reached.
In another alternative embodiment of the connecting element a blocking system is provided to block the movement of the connecting element at a predefined position of the module, at which point the common cable, belt, or rod starts slipping in the clutch means. To reduce or control friction between the clutch means and the common cable, belt, or rod materials of the common cable, belt, or rod on one hand and of the clutch surfaces of the clutch mechanism on the other hand must be chosen carefully.
In another embodiment, the at least one connecting element comprises a release mechanism such that the at least one connection element can be detached from the translation element at a pre-defined position and/or at a pre-defined angle. In this aspect, the at least one connecting element comprises a release mechanism such that the at least one connection element can be detached from the translation element above a certain level of force
According to another embodiment of the present invention, the synchronization of multiple optomechanical systems can be provided by a discrete link in which each of the multiple modules of the optomechanical system can only latch onto at a specific position.
In another preferred embodiment of the present invention, the centralized tracking system of the optomechanical system comprises a control system to pilot the movement of the tracking system in order to adjust the amount of direct light focused on photovoltaic cells and the amount of direct light transmitted through the optomechanical system. In other words, the control system allows to adjust the amount of light energy used for energy production and for lighting. This adjustment can be performed in a semi-manual manner, by inputting target values into a user-interface, or in a fully automated manner, based on various input parameters such as sun position models, weather forecasts, predefined schedules or sensor inputs.
In a further embodiment of the present invention, the control system further comprises a feedback loop to monitor the power output of a string of modules, based on at least one sensor such as a current sensor. Based on this feedback loop, the control system can optimize the relative position of the optical arrangement and the light collection arrangement to either maximize or minimize electrical power output or to achieve any intermediate electrical power output value.
In a further embodiment of the present invention, the optomechanical system of the invention further comprises a feedback control loop to monitor the position of the multiple modules, wherein the feedback control loop is for example an optical sensor or other type of sensors. The one or more sensors can report information on the absolute position and/or of the relative position of the tracking means, the optical arrangement or the light collection arrangement or a combination thereof.
In yet another embodiment of the present invention, the centralized tracking system of the optomechanical system comprises the control system to control movement of the tracking system such to adjust the amount of the direct component of incident light focused on photovoltaic cells and the amount of the direct component of incident light transmitted through the optomechanical system or in particular the amounts of light energy used for energy generation and for lighting. The control system can be configured as a passive or active control system. Active means that the tracking system uses sensors or predetermined data to find the current position of the sun and actively orient the optomechanical system. Therefore, the control system could be programmable based on manual inputs through a user interface or other correspondent elements and/or based on external inputs such as feedbacks based on a variety of parameters such as weather forecast, or meteorological models, pre-defined schedules or based on values detected by at least one sensor. Preferably more than one sensor is provided whereby the sensors are configured to measure parameters which can be entered to the control system as external inputs or can be extracted from a memory unit. These parameters may be derived from sensors such as light sensors, temperature sensors, humidity sensors and/or wind speed sensors or a combination thereof. Through these parameters, the control system is capable to adjust the transmission of light through the optomechanical system to fulfil the requirements of the plants growing beneath the optomechanical system. Hence, the centralized tracking system is piloted by a control system, either by direct end-user inputs through a human-machine interface, or indirectly based on an algorithm relying on external inputs collected through an interface or loaded from a memory.
In another embodiment of the present invention, the feedback loop of the control system includes one or more sensors providing feedback on environmental variables and crop growth conditions, such as light sensors, humidity sensors, sap flow sensors and/or wind speed sensors, or a combination thereof. This is advantageous to ensure that the optomechanical system can adjust light transmission to achieve optimal growth conditions for the crops cultivated below.
In another aspect of the present invention, the optomechanical system is configured to be integrated into a so-called Venlo-type greenhouse roofing and/or to be mounted onto a rooftop structure. Preferably, the optomechanical system is dimensioned, in particular its width and length, to match standard pitches between two Venlo-type greenhouse chapels. The thickness of the optical arrangement is also adjusted to match glass plane thicknesses compatible with standard clamping systems of such greenhouses. One optomechanical system can be integrated on one or both sides of each chapel of the Venlo-type greenhouse roofing. In this embodiment of the present invention, water condensation can be collected by gutters on both ends of the optomechanical systems to ensure that water will not drip on crops below the optomechanical systems. This embodiment is advantageous to reduce the costs and/or complexity of the supporting structure by using off-the-shelf components, mass-produced components, which are already optimized and validated for this usage.
If the greenhouse is mostly orientated in north-south direction, optomechanical systems can be integrated on both roof sections, in particular on the east and west facing roof sections. This is advantageous to achieve a very high ratio of optomechanical system per meter square of ground and therefore to maximize energy generation and control of light transmission.
If the greenhouse is mostly orientated along an east-west axis, the optomechanical systems are preferably integrated on the south-facing roof sections, while the north-facing roof sections may be covered with conventional greenhouse glass panes. This is advantageous to maximize the energy generation since the optomechanical systems are oriented towards the sun. In a further embodiment, where the greenhouse is mostly orientated along an east-west axis and located in an area with high levels of irradiance (such as the south of Europe or north of Africa), the glass panes on the north-facing roof section can be advantageously replaced by static photovoltaic modules with a predefined density of photovoltaic cells (or predefined transparency level), in order to increase the energy generation per meter square of ground and reduce the amount of light transmission. In a preferred embodiment, the density of photovoltaic cells or the transparency level of the static photovoltaic modules is close to 50%.
Each light collection layer of the light collection arrangement of the optomechanical system comprises elongate photovoltaic cells arranged in substantially parallel rows. The stripes are spaced from each other by gaps or spaces providing translucent regions for transmitting light for the photosynthesis of plants or crops growing beneath the optomechanical system. In a preferred embodiment of the present invention, each light collection layer of the light collection arrangement includes a plurality of elongate photovoltaic cells arranged in a bi-dimensional array of substantial parallel rows whereby each elongate photovoltaic cell has a ratio between length and width greater than 4:1.
In yet another embodiment of the present invention, the gaps between parallel rows of the arranged elongate photovoltaic cells are at least 30% of the width of the elongate photovoltaic cell.
In a further embodiment of the present invention, the solar cells or photovoltaic cells of each light collection layer are interconnected by connection lines such as ribbons, bus bars, or etched conductive sheets provided on the light collection layer. This arrangement of solar cells and connection lines forms a conductive circuit onto which the solar cells are interconnected. Thanks to a combination of series and parallel connections of the multiple elongate photovoltaic cells forming an arrangement on each light collection layer, the voltage and current output of the optomechanical system can be optimized.
In a preferred embodiment of the present invention, the connection lines are arranged along the length of the elongate photovoltaic cells to minimize shading between rows of the arrangement of the elongate photovoltaic cells and therefore optimize light transmission to the plants growing underneath the optomechanical system.
Furthermore, the connection lines may be provided at the back side of the elongate photovoltaic cells to minimize shading on the front side of the solar cells and therefore to optimize light collection and electricity production.
In another embodiment of the present invention, the connection lines are made out of transparent conductive material, such as a transparent conductive oxide. This is advantageous to guarantee that the light absorbed by the connection lines is minimal to ensure that the maximum of light not captured by the light collection elements is transmitted through the optomechanical system. The light collection elements of the light collection arrangement can be of different types. For example, each light collection element may be designed as single junction solar cells, such as poly- or mono-crystalline silicon cells. These can be for instance common types of mono-silicone solar cells with a good performance-to-cost ratio such as Passivated Emitter and Rear Cell (PERC) or Passivated Emitter or Rear Totally Diffused (PERT) cells, thin-film solar cells such as Copper Indium Gallium Selenide (CIGS), Cadmium Telluride (CdTe) or amorphous silicon, which are mass produced at very low cost, or more recent technologies such as Tunnel Oxide Passivated Contact (TOPCON). The solar cells can also be made from alternative materials such as perovskite solar cells or perovskite-silicon tandem solar cells. Multijunction solar cells based on III-V materials such as Gallium-Arsenide (GaAs) can also be used advantageously to achieve higher efficiencies and power densities.
In another embodiment of the present invention, the light collection elements are rear contact cells such as interdigitated back contact (IBC) solar cells. These types of solar cells are advantageous because they minimize shading on the front side of the light collection element and therefore increase the light conversion efficiency of the light conversion arrangement.
In another preferred embodiment of the present invention, the light collection elements are bifacial solar cells able to collect the light reflected from the ground to maximize the electricity production. In this embodiment, the ground in-between the crops may be covered with reflective material such as white plastic sheets in order to increase the reflection of sunlight and maximize the energy impinging on the back side of the light collection arrangement.
According to an embodiment of the present invention, the light collection layer may include bypass diodes arranged in parallel to the one or multiple rows of photovoltaic cells. Bypass diodes can minimize electrical loss and cell damage due to partial shading of the light collection layer. Furthermore, the light collection layer may include blocking diodes at one end of each row of photovoltaic cells in order to minimize electric losses and cell damage due to partial shading of the light collection layer.
In yet another embodiment of the present invention, the light collection layer may include a transparent front plane oriented towards the optical layer, an encapsulation layer comprising the elongate photovoltaic cells arranged in rows substantially spaced by gaps, and a transparent backplane. Therefore, the photovoltaic cells can be sandwiched between the front plane configured as a first protective layer and the backplane configured as a second protective layer. Thanks to the encapsulation, the photovoltaic cells can be protected from stress and contaminants such as humidity and dust.
The front plane and/or the backplane can be made of tempered or chemically hardened glass for its rigidity and resistance to shocks. Alternatively, the front plane can also be made of tempered or chemically hardened glass, while the backplane is made of a sheet of polymer. Another alternative is that both the front plane and the backplane are made of polymer sheets to reduce weight and to create a more lightweight optomechanical system. Furthermore, the front plane and/or the backplane may include an anti-reflective coating to increase light collection by the photovoltaic cells and light transmission through the backplane of each light collection layer by minimizing the extent of reflection at the transitions between air to optical layer and vice versa.
In another embodiment of the present invention, the light collection layer may include a photoluminescent layer arranged at the front plane or at the backplane of the photovoltaic cells. Thanks to the photoluminescent layer the spectrum of light transmitted by the optomechanical system can be changed. This is advantageous in agriculture applications in order to transmit light with a spectrum optimized for the plants growing beneath and redirecting at least part of the light impinging on the gaps between the photovoltaic cells towards the solar cells to improve the light collection efficiency. Preferably, the photoluminescent layer is designed to substantially redirect green-shifted light of the incident light onto the light collection elements, which is not used for photosynthesis of the plants growing beneath the optomechanical system, and to transmit blue-shifted light below 450 nm or red-shifted light above 650 nm.
In one embodiment of the present invention, each optical layer of the optical arrangement comprises at least one type of optical elements either of reflective or more preferably of refractive type such as lenses including plano-convex, plano-concave, bi-convex or bi-concave, meniscus type and aspheric curvature having polynomial shape. Furthermore, the refractive optical layer may include single or bifacial Fresnel lenses. This allows for efficient concentration of the direct sunlight onto the light collection elements. Thanks to higher concentration through the optical elements, the efficiency of electricity production of the optomechanical system increases and due to smaller light collection elements, the surface of the light collection layer able to transmit diffuse light is larger, which improve the growing conditions of the crops placed below the system.
Each optical layer can be made of rolled glass, which offers high rigidity and low-cost, compression-molded acrylate (PMMA) or polycarbonate (PC), and/or casting of a silicone layer onto a glass substrate, which provide simple patterning and forming of the optical elements. Furthermore, the optical layers may include a single- or double-sided anti-reflective coating to increase electricity production of the light collection layer and to improve light transmission.
The present invention also relates to a method for adjusting an optomechanical system according to the first aspect of the invention to adjust the amount of light energy used for energy production and lighting wherein the centralized tracking system of the optomechanical system comprises a control system, the method comprising using inputs of several sensors by the control system to pilot the movement of the tracking system in order to achieve an optimal ratio between light transmission and energy production.
In one embodiment of the method, the control system comprises a feedback loop comprising a current sensor, the method comprises using the feedback loop to optimize the relative position of the optical arrangement and the light collection arrangement to maximize, minimize or achieve any intermediate power output value.
In particular, the feedback loop comprises at least one irradiance sensor and at least one temperature sensor located close to the crops beneath the optomechanical system, the method comprising using the feedback loop to adjust light transmission to achieve a predefined daily light integral, and/or ensuring that irradiance and temperature limits are not exceeded.
In a second aspect, the present invention relates to an optomechanical system for light regulation on plants and electricity production, comprising
The tracking mechanism of the optomechanical system can be used to move the arrangement of the at least one translucent solar module by rotating around the rotating axis which can be arranged either on one side of the arrangement or in the middle. Thanks to that the tilt angle of the arrangement and therefore of the optomechanical system relative to the ground can be changed in particular during the day.
As used herewith, the tilt angle defines the angle between the translucent solar modules of the optomechanical system and a horizontal plane such as the ground. In particular, the tilt angle can be selected from −90° to 90°, −80° to 80°, −70° to 70°, −60° to 60°, −50° to 50°, −40° to 40°, −30° to 30°, −20° to 20°, and/or −10° to 10°. Preferably, the tilt angle is selected from −30° to 30°.
In one embodiment, the tracking mechanism comprises a single-axis tracker configured to orient the optomechanical system for adjusting the amount of light transmission, the amount of electricity production and/or the space between the ground and the optomechanical system. In this aspect of the invention, the tracking mechanism comprising a single-axis tracker with the rotating axis enables positioning of the optomechanical system to maximize energy production and/or to adjust the transmission of light to fulfil the requirements for the crops and plants growing underneath the optomechanical system and/or put the optomechanical system in a vertical position to increase the space for agricultural machines.
In another embodiment, the tracking mechanism is piloted by a control system, either by direct end-user inputs through a human-machine interface, or indirectly based on an algorithm relying on external inputs collected through an interface or loaded from a memory.
In the present invention, the control system controls the movement of the tracking system such to adjust the amount of the direct component of incident light focused on photovoltaic cells and the amount of the direct component of incident light transmitted through the optomechanical system or in particular the amounts of light energy used for energy generation and for lighting. The control system can be configured as a manual control system based on direct end-user inputs and/or as an active control system based on a feedback loop wherein the input is instantaneous and reliable. An active control system means that the tracking system uses sensors or predetermined data for example to find the current position of the sun and actively orient the optomechanical system. Therefore, the control system could be programmable based on manual inputs through a user interface or other correspondent elements and/or based on external inputs such as feedbacks based on a variety of parameters such as weather forecast, or meteorological models, pre-defined schedules or based on values detected by at least one sensor.
In one embodiment, the control system comprises a feedback loop comprising at least one sensor. The sensors are configured to measure parameters which can be entered to the control system as external inputs or can be extracted from a memory unit. These parameters may be derived from sensors such as current sensors, optical sensors, irradiance sensors, temperature sensors, humidity sensors and/or wind speed sensors or a combination thereof.
In one embodiment, external inputs can be selected from a group including feedback of sensors, feedback of weather forecasts or meteorological models and/or pre-defined schedules. Through the feedback from these parameters, the control system is capable to adjust the transmission of light through the optomechanical system to fulfil the requirements of the plants growing beneath the optomechanical system.
In one embodiment, the optomechanical system comprises a feedback loop comprising at least one sensor that can be selected from a list including current sensors, optical sensors, irradiance sensors, temperature sensors, humidity sensors, sap sensors, wind speed sensors, or a combination thereof.
In the present invention, each optical layer is laminated on top of a corresponding light collection layer forming a translucent solar module.
Furthermore, each light collection layer of the light collection arrangement of the optomechanical system comprises elongate photovoltaic cells arranged in substantially parallel rows. The stripes are spaced from each other by gaps or spaces providing translucent regions for transmitting light for the photosynthesis of plants or crops growing beneath the optomechanical system.
In one embodiment, each light collection layer of the light collection arrangement includes a plurality of elongate photovoltaic cells arranged in a bidimensional array of parallel rows whereby each elongate photovoltaic cell has a ratio between length and width greater than 4:1.
In another embodiment, the gaps between the rows are at least 30% of the width of the elongate photovoltaic cells.
In another embodiment, the elongate photovoltaic cells arranged in rows substantially spaced by gaps are interconnected by connection lines such as ribbons, bus bars or etched conductive sheets forming a conductive circuit and forming a combination of series and parallel connections.
This arrangement of solar cells and connection lines forms a conductive circuit onto which the solar cells are interconnected. Thanks to a combination of series and parallel connections of the multiple elongate photovoltaic cells forming an arrangement on each light collection layer, the voltage and current output of the optomechanical system can be optimized.
In a preferred embodiment of the present invention, the connection lines are arranged along the length of the elongate photovoltaic cells to minimize shading between rows of the arrangement of the elongate photovoltaic cells and therefore optimize light transmission to the plants growing underneath the optomechanical system.
Furthermore, the connection lines may be provided at the back side of the elongate photovoltaic cells to minimize shading on the front side of the solar cells and therefore to optimize light collection and electricity production.
In another embodiment of the present invention, the connection lines are made out of transparent conductive material, such as a transparent conductive oxide. This is advantageous to guarantee that the light absorbed by the connection lines is minimal to ensure that the maximum of light not captured by the elongate photovoltaic cells is transmitted through the optomechanical system. The elongate photovoltaic cells of the light collection arrangement can be of different types. For example, each elongate photovoltaic cells may be designed as single junction solar cells, such as poly- or mono-crystalline silicon cells. These can be for instance common types of mono-silicone solar cells with a good performance-to-cost ratio such as Passivated Emitter and Rear Cell (PERC) or Passivated Emitter or Rear Totally Diffused (PERT) cells, thin-film solar cells such as Copper Indium Gallium Selenide (CIGS), Cadmium Telluride (CdTe) or amorphous silicon, which are mass produced at very low cost, or more recent technologies such as Tunnel Oxide Passivated Contact (TOPCON). The solar cells can also be made from alternative materials such as perovskite solar cells or perovskite-silicon tandem solar cells. Multijunction solar cells based on III-V materials such as Gallium-Arsenide (GaAs) can also be used advantageously to achieve higher efficiencies and power densities.
In another embodiment, each light collection layer includes a transparent front plane oriented towards the optical layer, an encapsulation layer comprising the elongate photovoltaic cells arranged in rows substantially spaced by gaps and a transparent backplane. Preferably, each light collection layer includes a photoluminescent layer at the front plane and/or at the backplane to substantially redirect incident light impinging on the gaps between the multiple elongate photovoltaic cells. More preferably, the photoluminescent layer is designed to redirect light in the green wavelength of the sunlight and transmit light of the rest of the spectrum of sunlight.
In another embodiment, each optical layer comprises optical elements of a refractive type such as lenses including plano-convex, plano-concave, bi-convex, bi-concave, single facial Fresnel lenses or bifacial Fresnel lenses. This allows for efficient concentration of the direct sunlight onto the light collection elements, the elongate photovoltaic cells. Thanks to higher concentration through the optical elements, the efficiency of electricity production of the optomechanical system increases and due to smaller light collection elements, the surface of the light collection layer able to transmit diffuse light is larger, which improve the growing conditions of the crops placed below the system.
In another embodiment, each optical layer is made of rolled glass, compression-molded acrylate (PMMA), polycarbonate (PC) and/or casting of a silicone layer onto a glass substrate.
In another embodiment, each optical layer comprises a single-sided or double-sided anti-reflective coating.
The present invention also relates to a method for adjusting an optomechanical system according to the second aspect of the invention to adjust the amount of light energy used for energy production and lighting, the tracking mechanism of the optomechanical system comprising a control system, the method comprises using inputs of a feedback loop comprising one or more sensors by the control system to pilot the movement of the tracking mechanism in order to achieve an optimal ratio between light transmission and energy production.
In one embodiment, the control system comprising a feedback loop comprising a current sensor, the method comprises using the feedback loop to optimize the position of the translucent solar module to maximize, minimize or achieve any intermediate power output value. The feedback loop of the control system can monitor the power output of a string of modules, based on at least one sensor such as a current sensor.
In another embodiment, the feedback loop comprises or further comprises one or more sensors providing feedback on environmental variables and crop growth conditions, such as irradiance sensors, temperature sensors, light sensors, humidity sensors, sap flow sensors and/or wind speed sensors, or a combination thereof. This is advantageous to ensure that the optomechanical system can adjust light transmission to achieve optimal growth conditions for the crops cultivated below.
In another embodiment, the control system comprises or further comprises a feedback loop comprising at least one irradiance sensor and at least one temperature sensor located close to the crops beneath the optomechanical system, the method comprises using the feedback loop to adjust light transmission to achieve a predefined daily light integral, and/or ensuring that irradiance and temperature limits are not exceeded.
In another embodiment of the present invention, the control system comprises a feedback loop to monitor the position of the multiple modules, wherein the feedback loop comprises for example an optical sensor or other type of sensors. The one or more sensors can report information on the absolute position and/or of the relative position of the tracking means, the translucent solar modules or a combination thereof.
The foregoing and other objects, features and advantages of the present invention are apparent from the following detailed description taken in combination with the accompanying drawings in which:
The optical layer 11 is configured to focus the direct component of incident light 101, whereby the optical layer 11 can comprise multiple optical elements 12 of refractive or reflective type, such as lenses or reflectors. Furthermore, the optical layer 11 can comprise a single-sided or a double-sided antireflective coating to improve light transmission.
As depicted in
Furthermore, a control system 40 monitors the output of one or more sensor 42 and pilots the tracking system 60 in order to adjust the light transmission through the optomechanical system 1, based on a pre-defined algorithm or direct user inputs. The one or more sensor 42 can be for instance environmental sensors such as-but not limited to-irradiance sensors, temperature sensors, humidity sensors, or a combination thereof, providing feedback on the growth conditions of the plants cultivated below the optomechanical system 1. The one or more sensor 42 can also include current sensors, voltage sensors or power sensors, providing feedback on the electrical output of one or several light collection layers 21 of the light collection arrangement 20. The control system 40 monitors the sensor outputs and send commands to the tracking system 60 through an analog or digital bus (for instance LIN, CAN, etc.). The control system typically includes a micro-controller 41 in order to process sensor outputs and send commands to the tracking system 60. User inputs to the control system can be provided by means of a local or web-based interface (not shown here).
As illustrated in
As illustrated in
In this third embodiment of the optomechanical system 1, the guiding element 50 is not directly arranged between the optical layer 11 and the light collection layer 21. The guiding element 50 is attached to an intermediate frame element 31 arranged or formed on the frame 30 to indirectly attach the light collection layer 21 to the corresponding layer 11 of one module 2 of the optomechanical system 1.
In
With an east-west axis orientation of the greenhouse roofing, optomechanical systems 1 may be provided both on the east-facing roof section and on the west-facing roof section. This integration of optomechanical systems 1 on both east-facing and west-facing roof sections results in very high ratio of optomechanical system per meter square of ground, and therefore maximizes the energy production and light transmission through the optomechanical systems 1.
In a further preferred embodiment, each module 2 of the optomechanical system 1 is adapted in dimension to match the standard pitch between two Venlo-type greenhouse chapels such that on each side of the chapel one optomechanical system 1 can be integrated per roof section. This arrangement ensures that water condensation can be collected by the gutters on both ends of the optomechanical systems 1 and will not drip on crops below. Furthermore, edges of the optical layer 11 of the optical arrangement 10 including thickness and profile are designed to be compatible with conventional Venlo-type greenhouse clamping profiles. The good compatibility and easy integration of optomechanical systems 1 according to the present invention reduce costs and complexity of the supporting structure by using off-the-shelf components which are already proved in action.
Furthermore, the tracking system 60 of the optomechanical system 1 can be attached directly on the greenhouse supporting structure in an easy manner.
On
As illustrated on
Furthermore, the control system 40 monitors the output of one or more sensors 42 and pilots the tracking mechanism 60 in order to adjust the light transmission through the optomechanical system 200, based on a pre-defined algorithm and/or direct user inputs. The one or more sensors 42 can be for instance environmental sensors such as-but not limited to-irradiance sensors, temperature sensors, humidity sensors, or a combination thereof, providing feedback on the growth conditions of the plants cultivated below the optomechanical system 200. The one or more sensors 42 can also include current sensors, voltage sensors or power sensors, providing feedback on the electrical output of one or several light collection layers 222 of the light collection arrangement comprising elongate photovoltaic cells 22. The control system 40 monitors the sensor outputs and send commands to the tracking mechanism 60 through an analog or digital bus (for instance LIN, CAN, etc.). The control system typically includes a micro-controller 41 in order to process sensor outputs and send commands to the tracking mechanism 60. User inputs to the control system can be provided by means of a local or web-based interface (not shown here).
| Number | Date | Country | Kind |
|---|---|---|---|
| 21206307.7 | Nov 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/080577 | 11/2/2022 | WO |
