Patent Publication Number: US-2016242372-A1

Title: Photosynthetically active lighting under plant leaves

Description:
BACKGROUND 
     Plants use photosynthesis to convert light energy into chemical energy that allows plants to grow. More particularly, photosynthesis uses light energy to synthesize carbohydrate molecules, such as sugars, from carbon dioxide and water. Plants in nature receive light from the sun and use the sunlight in photosynthesis. Hydroponic systems have been developed that allow growing of plants indoors without sunlight and traditionally use lighting systems above plants to provide light for photosynthesis. 
     SUMMARY 
     In accordance with an aspect of the invention, a hydroponic system provides photosynthetic light intensities from below a plant, e.g., underneath the leaves of the plant, to accelerate the photosynthesis process in plants. The under-leaf light can be used with lighting from above the plant, e.g., sunlight or artificial lighting directed onto the tops of leaves, to increase the total plant area exposed to light suitable for photosynthesis. The under-leaf lighting also provides a compact hydroponic system since the lighting can be mounted on structures that hold the roots of plants. Gas lines may be provided with the under-leaf lighting, for example, to provide ventilation, air flow, or carbon dioxide that when combined with the additional light may increase the total photosynthesis in the plant. 
     In one configuration, a hydroponic system uses customized LED panels to supply light from beneath the leaves of plants during the growth cycle of the plants. An under-leaf lighting system may include a first set of LED panels mounted on a configuration tray or other structure that holds the root system of one or more plants, and the first set of LED panels may be positioned to direct light at the undersides of the leaves of the one or more plants. The LED panels may be laminated to improve water resistance, and the laminated structure may be glued or otherwise affixed using any number of methods to a planting fixture. An optional above-plant lighting system may include a second set of LED panels that may be mounted above the one or more plants and may be positioned to direct light onto the tops of the leaves of the one or more plants. Lighting from both above and beneath the plant leaf may increase photosynthesis without using an excessive light intensity that might damage the upper surfaces of plants may be able to handle. If other plant growth criterion such as nutrients and carbon dioxide are provided to a growing plant, increasing the area of plant surface exposed to light for photosynthesis may encourage and promote healthy plant growth. 
     In accordance with a further aspect of the invention, under-leaf lighting can be provided with or even integrated into a gas line or tube connected to a system that vents or supplies gas and other vapors including carbon dioxide under the leaves of plants. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows a hydroponic system having net pots mounted on a configuration tray. 
         FIG. 1B  shows an implementation of the system of  FIG. 1A  after addition of under-leaf lighting and gas lines. 
         FIG. 2  shows an implementation of a hydroponic system with under-leaf lighting and above-plant lighting. 
     
    
    
     The drawings illustrate examples for the purpose of explanation and are not of the invention itself. Use of the same reference symbols in different figures indicates similar or identical items. 
     DETAILED DESCRIPTION 
     A system for growing plants can provide lighting to both the top side and bottom side of the plant, e.g., above-plant lighting and under-leaf lighting. The under-leaf or above-plant lighting may be artificial and may provide lighting having a duty cycle, an intensity and frequency spectrum selected to optimize photosynthesis and the plant&#39;s growth. The system may thus provide better growth than natural environments since under-leaf lighting does not normally occur in nature. The system may also provide better growth than artificial environments that only provide lighting from the top down onto plants. 
     In an enclosed hydroponic growth system, plants may be positioned in net pots contained in a configuration tray panel, and under-leaf light can be implemented in or mounted on a configuration tray.  FIG. 1A , for example, shows a hydroponic system  100  that may include a reservoir  110  and a configuration tray  120 . Configuration tray  120  acts as a top or cover for reservoir  110  and contains one or more plant fixtures  122 , e.g., net pots. Configuration tray  120  may be replaceable or reconfigurable to change the number, size, or spacing of plant fixtures  122 , for example, to accommodate plants having a different size or different rooting needs. Each plant fixtures  122  provides a structure capable of holding a plant, particularly the roots of a plant, during growth and may be, for example, a basket-type device through which the roots of the plant extend down towards the bottom of reservoir  110 . The stalk and leaves of a plant in a plant fixture  122  generally extend above tray  120 . Reservoir  110  may contain water or an aqueous nutrient solution. In some hydroponic applications, reservoir  110  contains the aqueous nutrient solution at a level that at least partially submerges the roots of plants that fixtures  122  hold. In an aeroponic use, reservoir  110  may contain a low level of water or solution but provides an enclosed volume for the roots to occupy. For example, reservoir  110  may contain a level of nutrient solution below the deepest roots of the plants, which hang from net pots and are surrounded by air, and hydroponic system  100  may supply the nutrient solution to misters that apply droplets of nutrient solution to the plants&#39; roots. 
     System  100  may further contain a control system, a wireless communication system, and various canisters, pumps, and other systems for storing and mixing nutrients for growing plants. More generally,  FIG. 1A  only illustrates an example implementation of hydroponic system  100 . Other implementations may include any known hydroponic system or sub-systems, may be constructed using conventional designs and techniques, and may be improved as described herein through addition of under-leaf lighting. 
       FIG. 1B , for example, shows system  100  with under-leaf lighting mounted on configuration tray  120 . The under-leaf lighting may particularly include LED strips  130  positioned along lines between rows or columns of pot centers  122 . The number of strips  130  can vary with implementation. Each strip  130  may include a set or collection of LEDs selected or tuned in spectrum or frequency for plant growth and more specifically tuned in spectrum for lighting the underside of the leaves of one or more plants. Further, in a programmable configuration, each strip  130  may contain LEDs of different types, e.g., different frequencies of peak emissions, and a control system (not shown), e.g., a computer executing a program, can control the LEDs to provide under-leaf lighting with a spectral distribution, a period or duration, and an intensity tailored for the underside of leaves or other portions of the specific plant or plants being illuminated. LEDs may be a beneficial source of light in strips  130  because LEDs may be selected to produce the correct spectrum and intensity for photosynthesis and because LEDs produce less heat than most other light sources. Still other light sources could alternatively be used. Reflectors, mirrors, or light deflectors on tray  120  may be employed, but under-leaf lighting that directs light directly onto the underside of leaves may be more energy efficient. 
     LED strips  130  may be mounted on configuration tray  120  through a process of lamination or other waterproofing processes to make strips impervious to water or other contaminates, which may be provided to the plants at the net pots  122 . For example, an aeroponic system may apply a mist or spray of water or nutrient solution to the plant roots in net pots  122 , and LED strips  130  may be constructed for use where mist or spray might contact LED strips  130 . The lamination of the LEDs and wiring of strips  130  may be integrated as part of configuration tray  120 . For example, a manufacturing process may place LEDs and wiring on support structure of tray  120 , and a clear layer or protective membrane may be affixed, e.g., glued or fused onto the support structure. The membrane may be fully water and contamination proof to protect LEDs and wiring from moisture or corrosive solution. In the illustrated configuration, under-leaf gas lines or tubes  135  may be affixed with the LEDs under, atop, or adjacent to the membrane attached to tray  120 . In one implementation, gas tubes  135  may include vent holes and may supply carbon-dioxide or other gases, e.g., form a tank (not shown) or supply of air containing carbon dioxide or other gases. In another implementation, gas tubes  135  may include an inflatable tube or bladder made of a fabric or other porous material, so that when gas tubes  135  are inflated with a supply gas such as air or carbon dioxide, gas tubes  135  leak the supply gas under the leaves of plants being grown. Alternatively, gas tubes  135  may vent or draw gas or air away from under the plants, or a gas or air flow may be supplied or drawn through openings associated with net pots  122 . 
     Gas tubes  135  in one implementation are small tubes that are laminated onto configuration tray  120  and made waterproof. Carbon-dioxide gas or air flow injected through gas tubes  135  may then be introduced to the underside or the “normally shaded” side of the plants, or air flow may be provided to the underside of the leaves by drawing gas from under the plants through gas tube  135 . The underside of plants commonly suffers from CO 2  and light deprivation, and therefore may not grow as well as the upper portions of the plants. Supplying light and CO 2  to the underside may thus be beneficial to many types of plants. 
     Under-leaf lighting systems, e.g., LED strips  130 , provide the lighting upwards to the underneath surfaces of plants, and under-leaf gas supply systems supply gas such as CO 2  from beneath the leaves of plants. The terminology “under-leaf” plant surfaces is used herein to include any underneath surfaces and not to be limited to leaves or plants having leaves. Such under-leaf lighting or gas supply may be used with conventional lighting or gas supply above the plants in net pots  122 . For example, hydroponic system  100  may be exposed to artificial overhead lighting or natural sunlight, e.g., direct or through skylights or windows predominantly onto the top surfaces of plants. 
     An enclosed hydroponic system may however provide both under-leaf lighting and above-plant lighting.  FIG. 2  shows a hydroponic system  200  including both under-leaf lighting and above-plant lighting. As shown in  FIG. 2 , an above-plant portion  210  of hydroponic system  200  may include lighting equipment  212 , an air circulation system  216 , and a temperature control system  218 . As shown in  FIG. 2 , some or all of above-plant systems  210  may be mounted on an actuated platform  220  that is normally above plants that may be rooted in net pots  122 . As shown in  FIG. 2 , above-plant lighting  212  directs light predominantly onto top surfaces of the plants, e.g., the top surfaces of leaves, and under-leaf lighting  130  directs light predominantly onto under surfaces of the plants, e.g., the bottom surfaces of leaves. Hydroponic system  200  can similarly provide both under-leaf gas tubes  135  for under-leaf gas supply or air circulation and above-plant system  216  for gas supply or air circulation, so that carbon-dioxide or other growth stimulating gases can be better supplied or flow from above and below plants. 
     A control system  220 , which may be a programmable controller or electronic computing system, can collect measurements from sensors  230 , communicate with other devices through a network (not shown), and control the subsystems of hydroponic system  200 . In particular, sensors  230  may sense operating parameters of hydroponic system  200  such as atmospheric temperatures and compositions, the level, temperature, and composition of nutrient solution in reservoir  110 , the levels of supply canisters (not shown) for gases and liquid plant nutrients, and the operating conditions of pumps, fans, and other subsystems of hydroponic system  200 . Based on such measurements from sensors  230  and on user commands or the programming of control system  220 , control system  220  may particularly control the intensity and spectrum of light from lighting systems  130  and  212  and the duty cycles, i.e., times or durations during which lighting systems  130  and  212  supply light. Control system  220  may further coordinate operations of subsystems such as lighting systems  130  and  212 , gas lines  135 , exhaust  216 , heating or cooling systems  218 , for example, to optimize plant growth. 
     A plant growth system that provides under-leaf lighting or gas supply may provide several benefits. In particular, plants can receive the correct light and carbon dioxide for photosynthesis on more of the plant&#39;s surface area because both top leaf surfaces and under-leaf surfaces may receive sufficient lighting and carbon-dioxide for photosynthesis. This may increase photosynthetic activities of the plant, encouraging growth and promoting plant health. Further, lower or inner plant leaves may still receive under-leaf lighting even when the leaves are shaded by the upper or outer leaves of the plant or shaded by other plants when multiple plants are grown in the same hydroponic system. The shaded leaves may thus receive more light than “normal” and may tend to grow larger and better. Shaded leaves, which might otherwise act as sinks of energy produced in the photosynthesis process, become sources of energy for plant growth. By introducing Photosynthetically Active Radiation (PAR) lighting or Photosynthetically Useable Radiation (PUR) lighting to lower leaves, there is a photosynthesis process in these leaves, allowing a sourcing in the photosynthetic process. Such lighting may lead to a better crop yield or plant growth. 
     Under-leaf lighting may also reduce the need to supplement lighting with reflector walls. Reflector walls may introduce heat bouncing off their surfaces and onto plants, block CO 2  flow to the plants, or restrict air flow from otherwise cooling the plants. 
     Although particular implementations have been disclosed, these implementations are only examples and should not be taken as limitations. Various adaptations and combinations of features of the implementations disclosed are within the scope of the following claims.