Abstract:
A photo-bioreactor module adapted for stacking a plurality of such modules for producing algal bioproducts includes at least an upper and a lower light-transmitting member each having a plurality of openings. The upper and lower light-transmitting members are spaced apart from one another and at least one of the upper and lower light-transmitting members includes at least one light connection terminal for coupling in light from a light source and transmitting the light laterally. A plurality of photobioreactor conduits each extending from respective openings in the upper and lower light-transmitting member define algae containment interior spaces, wherein the plurality of photobioreactor conduits contact the upper and a lower light-transmitting members along areas of contact. The light transmitted laterally by the upper and lower light-transmitting members couples into the plurality of photobioreactor conduits along the areas of contact.

Description:
FIELD OF THE INVENTION 
     This disclosure generally relates to production of biofuels. More particularly, this disclosure relates to algae production and harvesting, which is suitable for the mass harvesting of algae bioproduct in sufficient quantities to produce algal fuel. 
     BACKGROUND 
     Fossil fuels, such as coal and gasoline, currently provide most of the energy needs of the world—including the United States. Moreover, the demand for fossil fuels has steadily increased over the years. At the time of the Oil Embargo of 1973, the U.S. net oil import rate was only one-third of total consumption, whereas today the U.S. net oil import rate approaches two-thirds of total consumption. With the U.S. oil consumption rate increasing by approximately 11 percent over the past ten years, and with crude oil spot prices have been recorded well over $140 per barrel, the U.S. economy is faced with a fuel bill approaching $700 billion over the next decade. 
     Because of the diminishing reserves and increasing costs of fossil fuels, as well as the damaging effects fossil fuels can have on the environment, alternative energy sources that are renewable and less damaging to the environment are currently being developed. Alternative energy sources generally include natural gas, wind energy, hydroelectric power, solar energy, hydrogen, nuclear energy and biofuels. 
     Although natural gas is a fossil fuel that burns cleaner than gasoline, it produces carbon dioxide—the primary greenhouse gas. Wind energy, one of the oldest and cleanest forms of energy, is unsightly and noisy. Hydroelectric power, an old and well-developed energy source, has a limited capacity for expansion. All energy (other than nuclear energy) is ultimately derived from solar energy, which can also be gathered directly using photoelectric cells. Hydrogen has proven to be a viable fuel source for vehicles, with the advent of fuel cells. However, use of hydrogen as an energy source poses problems with respect to its production, storage and distribution. Nuclear energy includes nuclear fission, which is very costly and generates toxic waste, and nuclear fusion, which is clean but has proven unworkable. 
     Biofuel is commonly defined as a solid, liquid or gas fuel derived from recently living organisms, including plants, animals and their byproducts. It is a renewable energy source based on the carbon cycle, unlike other natural resources such as petroleum, coal and nuclear fuels. Biofuels can be obtained from wood, single- and multi-cellular plant materials, animal excrement and bacteria. Ethanol is one type of biofuel that, combined with gasoline, is widely used in the transportation industry. Since biofuels can also be derived from plant oils, algae-derived biofuels have proven to be a promising alternative energy source. However, various obstacles have thwarted the large-scale manufacture and use of algal biofuels. 
     A primary obstacle inherent to conventional algal fuel production is the inability to produce and harvest algae in sufficient quantities to provide enough algal fuel to serve the energy needs of civilization. Utilizing existing methods, production of algal fuel in sufficient quantities would require growing algae in large production ponds or photo-bioreactors, each of which is limited by production and economic inefficiencies. It is estimated that approximately 200,000 hectares (approximately 450,000 acres or 780 square miles) of production pond surface area would be required to produce a quantity of algal biodiesel sufficient to replace the quantity of oil currently consumed each year in the United States. 
     Algae feedstock grown in open pond systems are subject to many systemic inefficiencies and challenges, some of which are also common to both open and closed system photobioreactor systems. Some of these challenges include the controllability of spectrum, intensity and duration of light cycles; temperature controls or seasonal temperature variations; contamination by hostile windborne particulate; and the cost of harvesting, transport, pre-treatment and storage, to name a few. These and other related challenges of conventional algae farming methods effectively limit the commercial viability of algal fuels. 
     Closed system photo-bioreactors, another conventional algal fuel production system, suffer from many of the same limitations, drawbacks and disadvantages, associated with open pond systems. For example, known closed photo-bioreactor systems preclude adequate control of light quantity, spectrum, duration and cycle. Additional issues include land area requirements, supporting and foundational structure requirements for large scale production applications, and harvesting inefficiencies. While closed system photo-bioreactors overcome, or substantially mitigate, many of the environmental and biological issues associated with open pond systems, they have not yet achieved an adequate level of efficiency required to produce algal biomass in quantities sufficient to reduce national dependence on foreign oil. 
     Accordingly, there is an unmet need for an algae bioproduct production and harvesting apparatus suitable for the mass production and harvesting of algae. What is needed is an apparatus that overcomes the aforementioned limitations, disadvantages and drawbacks, concomitant with open pond systems, closed-apparatus photo-bioreactors, and other known systems. It would be desirable to provide such an apparatus that enables greatly improved control over algae light exposure variables, including, for example, control over light cycle, light quantity, light spectrum and light duration. It would be further desirable to provide such an apparatus that also enables and facilitates precise monitoring and control of other variables that are known to affect algae growth rate, including, for example, algae temperature exposure, nutrient levels, and gas (e.g., O 2  and CO 2 ) levels. In order to address the aforementioned land requirement issues associated with existing open pond systems and closed system photo-bioreactors, it would be highly desirable to provide an apparatus having a structural configuration requiring a smaller footprint vis-à-vis existing systems. In short, it would be highly desirable to provide an apparatus that is low cost, easy to maintain, easy to reproduce, and that enables an operator to precisely control all aspects of the Calvin Cycle in order to maximize production and harvesting volume and efficiency, regardless of the desired strain of algae being grown. 
     SUMMARY OF THE INVENTION 
     This disclosure is generally directed to an algae production and harvesting apparatus that is suitable for the mass production and harvesting of algae bioproducts in sufficient quantities to produce algal fuel. The apparatus is vertically scalable and, accordingly, has the benefit of a small footprint vis-à-vis other known algae bioproduct production and harvesting systems and methods. The apparatus can provides the ability to control characteristics of temperature, light and other factors known to affect the rate of growth of algae, in order to maximize production efficiency. The apparatus generally incorporates relatively low-cost components arranged in a manner that facilitates efficient deployment and subsequent repair. The unique vertical arrangement disclosed herein takes advantage of natural fluid dynamics for supplementary apparatus structural support. 
     In one implementation, a vertically-stackable modular apparatus for algae bio-product production and harvesting comprises at least an upper and a lower light-transmitting member each having a plurality of openings, wherein the upper and lower light-transmitting members are spaced apart from one another and at least one of the upper and lower light-transmitting members includes at least one light connection terminal for coupling in light from a light source and transmitting the light laterally. A plurality of photobioreactor conduits extending from respective openings in the upper and the lower light-transmitting member each define algae containment interior spaces, wherein the plurality of photobioreactor conduits contact the upper and lower light-transmitting members along areas of contact. The light transmitted laterally by the upper and lower light-transmitting members couples into the plurality of photobioreactor conduits along the areas of contact. 
     In another aspect, the algae containment structure can comprise a light-transmitting unitary structure having a plurality of parallel linear channels extending through the unitary structure in such a manner that adjacent channels share a sidewall. Furthermore, each linear channel may be selected having a pre-determined uniform cross-sectional area for maximizing growth of a particular algae strain. 
     In another aspect, the algae containment structure can include a plurality of individual light-transmitting linear conduit members, each defining an interior conduit space. Each conduit member can be chosen having a uniform cross-sectional area for maximizing growth of a particular algae strain. 
     In another aspect, the linear channels and linear conduit members can have any of a number of different cross-sectional geometries, including, for example, circular, elliptical, triangular, rectangular and hexagonal. 
     In another aspect, the light transmitter can include a plurality of light transmitting strands communicating light from the light source to individual linear conduit members. 
     In another aspect, the light transmitter can include a horizontally-disposed light transmitting panel having a plurality of apertures for receiving the respective plurality of linear conduit elements therethrough, wherein the panel transmits light from the light source to the linear conduit members, and provides structural support for the conduit members. 
     In another aspect, the photo-bioreactor module can include a structural attachment mechanism for enabling secure vertical stacking of multiple photo-bioreactor modules, as well as an optional module lifting structure for facilitating vertical hoisting of an upper module from an underlying lower module. 
     In another aspect, a gasket can be provided interposed between stacked modules to ensure sealed communication between aligned interior spaces extending through the stacked modules. 
     In another aspect, a product collecting vessel can be provided in communication with the photobioreactor module for collecting algae biomass, excretions, and other algae derivative product. Optionally, a product transfer assembly, which may be in the form of conduits, can provide fluid communication between the photo-bioreactor module and the collecting vessel. 
     In another aspect, a processor may be disposed in fluid communication with the collecting vessel for processing the algae biomass, excretions, and other algae derivative product. 
     In another aspect, the apparatus includes known components enabling monitoring of, and control over, other factors known to affect algae growth rate, such as CO 2  concentration, O 2  levels, and nutrient levels, for example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Disclosed embodiments will hereinafter be described, in conjunction with the appended drawings, provided to illustrate and not to limit the appended claims, where like designations denote like elements, and in which: 
         FIG. 1  is a partial schematic side view of an illustrative embodiment of the algae production and harvesting apparatus; 
         FIG. 2  is a side view of an illustrative embodiment of the algae production and harvesting apparatus, with a collecting vessel provided beneath a photobioreactor module, and a product transfer assembly provided in fluid communication between the photobioreactor module and the collecting vessel; 
         FIG. 3  is a top view of multiple photobioreactor conduits, or tubes, in a photobioreactor module of an illustrative embodiment of the algae production and harvesting apparatus, more particularly illustrating an exemplary rectangular photobioreactor channel geometry; 
         FIG. 4  is a top view of multiple photobioreactor channels, in a photobioreactor module of an illustrative embodiment of the algae production and harvesting apparatus, more particularly illustrating an exemplary hexagonal photobioreactor channel geometry; 
         FIG. 5  is a top view of multiple photobioreactor channels, in a photobioreactor module of an illustrative embodiment of the algae production and harvesting apparatus, more particularly illustrating an exemplary circular photobioreactor channel geometry; 
         FIG. 6  is a side view of multiple stacked photobioreactor modules in implementation of an illustrative embodiment of the algae production and harvesting apparatus; 
         FIG. 7  is an exploded perspective view of a photobioreactor module of an illustrative embodiment of the algae production and harvesting apparatus; 
         FIG. 8  is a perspective view of multiple photobioreactor channels extending through light-transmitting module panels; 
         FIG. 9  is a top view of a photobioreactor module of an illustrative embodiment of the algae production and harvesting apparatus, in which the photobioreactor channels have a rectangular geometry; 
         FIG. 10  is an exploded view, partially in section, of a pair of stacked photobioreactor modules, illustrating a gasket interposed between the photobioreactor modules; 
         FIG. 11  is a sectional view of a pair of stacked photobioreactor modules, more particularly illustrating an exemplary manner of securing the upper photobioreactor module on the lower photobioreactor module by seating a module foot provided on the upper photobioreactor module in a module receptacle provided on the lower photobioreactor module; 
         FIG. 12  is a sectional view of an upper corner of an photobioreactor module, with a module lifting shackle (or lift plug) threaded into a module receptacle opening (not illustrated) provided in the uppermost photobioreactor module of the algae production and harvesting apparatus in place of a module receptacle; 
         FIG. 13  is a schematic diagram which illustrates inclusion of sensors for gas, fluid and light, respectively, in a photobioreactor module of an illustrative embodiment of the algae production and harvesting apparatus; 
         FIG. 14  is a side view of an illustrative embodiment of the algae production and harvesting apparatus, with a pair of sensors provided in a pair of photobioreactor tubes, respectively, in a photobioreactor module of the algae bioproduct harvesting apparatus; 
         FIG. 15  is a sectional view of a pair of stacked photobioreactor modules having a gasket interposed between the modules; 
         FIG. 16  is a perspective view of an illustrative gasket for providing sealing between the stacked photobioreactor modules; 
         FIG. 17  is a sectional view of an exemplary flow control device for controlling flow of algae product from each photobioreactor channel into the product transfer assembly; and 
         FIG. 18  is a top view of the exemplary flow control device illustrated in  FIG. 17 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following detailed description is merely exemplary in nature and is not intended to limit the described embodiments or the application and uses of the described embodiments. As used herein, the word “exemplary” or “illustrative” means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations provided to enable persons skilled in the art to practice the disclosure and are not intended to limit the scope of the appended claims. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following. 
     Referring to the drawings, an illustrative embodiment of the algae production and harvesting apparatus (hereinafter “apparatus”) is generally indicated by reference numeral  100  in  FIGS. 1 and 2 . The apparatus  100  may include at least one photobioreactor module  112 , which is adapted to contain and sustain the growth of algae  133  ( FIG. 8 ) as will be hereinafter further described. In some applications, multiple photobioreactor modules  112  may be stacked on top of each other to increase the algal growth capacity of the apparatus  100  without increasing its footprint. A collecting vessel (shown in  FIG. 1  as a “Collector”)  101  may be provided beneath the photobioreactor module or modules  112  to collect algal bioproducts (not illustrated) from algae  133  ( FIG. 8 ) growing in the photobioreactor module or modules  112 . The algal bioproducts can include any product of the algae  133  which may be used to produce algal fuel or other useful product. Algal bioproducts include, but are not limited to, algae, algae biomass, algae excretions and algae derivative products. A product processor  102  may communicate with the collecting vessel  101  to receive and process the algal bioproducts into algal fuel or other product. The product processor  102  may utilize conventional methods, which are known by those skilled in the art, to convert the algal bioproducts into algal fuel or other product. The product processor  102  may be a dryer, a press, a transesterfication processor, a refinement processor, a microwave processor or a sonic processor, for example and without limitation. Various processes may be employed to achieve the final desired product and the specific implementation for a particular product, as will be evident to one skilled in the art. 
     In some embodiments, a module support frame  108  may support the photobioreactor module(s)  112  over the collecting vessel  101 . The module support frame  108  may include multiple vertical corner frame members  109 , which support respective corners of the photobioreactor module(s)  112 , and multiple center frame members  110  (indicated in phantom in  FIG. 2 ), which support the center portion of the photobioreactor module(s)  112 . In some embodiments, a product transfer assembly  104  may be interposed between the photobioreactor module(s)  112  and the collecting vessel  101 , to facilitate drainage of algal bioproducts from the photobioreactor module(s)  112  into the collecting vessel  101 , as will be hereinafter further described. The product transfer assembly  104  may include multiple product transfer tubes  105  extending from the photobioreactor module(s)  112  to the collecting vessel  101 . Alternatively, product can be collected within plumbing connections of the array, and subsequently transmitted directly to the product processor  102 . 
     As illustrated in  FIG. 7 , each photobioreactor module  112  of the apparatus  100  may include a module frame  113 . At least one light-transmitting member  122 ,  126 ,  128  may be provided on the module frame  113 . Each light-transmitting member  122 ,  126 ,  128  comprises a light transmitting material such as polycarbonate, for example and without limitation. Polycarbonate is well known to be highly transparent to visible light and has better light transmission characteristics than many kinds of glass. Multiple openings  123  for photobioreactor conduits  132  may be provided in each light-transmitting member  122 ,  126  and  128 . An array of multiple photobioreactor conduits  132 , each of which is a transparent and light-transmitting material, such as polycarbonate, for example and without limitation, may extend through the respective openings  123  of each light-transmitting panel  122 ,  126  and  128 . Each opening  123  may correspond in shape and size to the cross-sectional configuration of each photobioreactor conduit  132 . Accordingly, each photobioreactor conduit  132  is disposed in light-receiving relationship with respect to each light-transmitting panel  122 ,  126  and  128 , along the surface area of contact between the photobioreactor conduit  132  and each light-transmitting member  122 ,  126  and  128 , for purposes that will be hereinafter described. The light-transmitting characteristics of each photobioreactor conduit  132  may facilitate transmission of light that is received from the light-transmitting panels  122 ,  126  and  128 , along substantially the entire length of the photobioreactor conduit  132 . Each photobioreactor conduit  132  is adapted to contain algae  133  ( FIG. 8 ) and may be geometrically shaped and configured to maximize exposure of the contained algae  133  to light, and to maximize internal distribution of the light throughout the photobioreactor conduit  132 . It should be noted that the spacing of the openings  123  in the light-transmitting members  122 ,  128  is for illustrative purposes. As will be evident, one aspect of the apparatus is to provide conduits in an extremely dense arrangement. Accordingly, the exterior surfaces of adjacent conduit walls can be in physical contact with another. Furthermore, while the apparatus is illustrated in  FIG. 7  as a plurality of individual conduits  132  extending through openings  123  in light transmitting members, this Disclosure contemplates the alternative fabrication of a unitary, or one-piece, module having a plurality of parallel linear channels extending through the unitary structure in such a manner that adjacent channels share a sidewall. In that case, each linear channel defines an interior channel space, which can be chosen having a pre-determined uniform cross-sectional area for maximizing growth of a particular algae strain. Such a one-piece module structure would replace the need for separate conduits  132  and light-transmitting members  122 ,  126  and  128 , as well as the need for an external support structure. 
     Returning to the exemplary embodiment, the module frame  113  of each photobioreactor module  112  may have any design or structure that is suitable for supporting at least one light-transmitting member  122 ,  126 ,  128 . As further illustrated in  FIG. 7 , in some embodiments the module frame  113  may have a generally cube-shaped configuration with four vertical corner supports  114 , and a pair of upper and lower horizontal transverse supports  115  connecting the adjacent corner supports  114  to each other. In some embodiments, a bottom light-transmitting member  122  may be provided on the lower transverse supports  115  of the module frame  113 . A top light-transmitting member  128  may be provided on the upper transverse supports  115 . One or more spaced-apart middle light-transmitting member  126  may be provided in the module frame  113  between the bottom light-transmitting member  122  and the top light-transmitting member  128 . Each photobioreactor conduit  132  may extend through aligned openings  123  provided in the bottom light-transmitting member  122 , the middle light-transmitting member  126  and the top light-transmitting member  128 , respectively. The bottom light-transmitting member  122 , the middle light-transmitting member  126  and the top light-transmitting member  128 , may be attached to the module frame  113  using adhesives, fasteners and/or any other suitable attachment technique known by those skilled in the art. 
     As illustrated in  FIG. 9 , in some embodiments, at least one center plate support  118  may extend through center support openings (not illustrated) provided in each of the light-transmitting member  122 ,  126  and  128 , for reinforcement. Each center plate support  118  may extend in generally parallel and adjacent relationship with respect to the photobioreactor conduits  132 . In some embodiments, four center plate supports  118  may extend through the center support openings in the light-transmitting member  122 ,  126  and  128 . 
     The photobioreactor conduits  132  of each photobioreactor module  112  may have any desired cross-sectional configuration. As illustrated in  FIG. 3 , in some embodiments each photobioreactor conduit  132  may have a generally rectangular cross-section. As illustrated in  FIG. 4 , in some embodiments each photobioreactor conduit  132  may have a generally hexagonal cross-section. As illustrated in  FIG. 5 , in some embodiments each photobioreactor conduit  132  may have a generally circular cross-section. Other cross-sectional geometries, such as triangular, pentagonal and octagonal, for example and without limitation, are possible. As illustrated in  FIG. 8 , in implementation of the apparatus  100 , which will be hereinafter described, algae  133  may be grown in each photobioreactor conduit  132  for the purpose of harvesting algal bioproducts (not illustrated) from the algae  133 . The particular cross-sectional geometry, and cross-sectional area, of each photobioreactor conduit  132  may depend upon such factors as the characteristics of the particular strain of algae  133  being grown in the algae growth conduits  132 , the range of environmental parameters required by any specific strain of algae for maximization of photosynthetic efficiency, variable exposure requirements to various light sources and spectrum, intensity of exposure, containment volume and the specific manufacturing methods used to fabricate the algae growth conduits  132 . 
     As illustrated in  FIGS. 1 and 2  of the drawings, a light source  134  shown as a light bulb (only for example) may be disposed in optical communication with each of the light-transmitting member  122 ,  126  and  128 . In some embodiments, fiber optic light transmission cables  135  may be disposed in optical communication with the light source  134 . Light tubing branches  136  may branch from each light transmission cable  135 . A light-transmitting connection terminal  137  may be used to connect light transmission cable branches  136  to the light transmitting members  122 ,  126  and  128 . The light source  134  can be natural light, artificial light, or a combination of both natural light and artificial light. Each light-transmitting member  122 ,  126  and  128  imparts structural rigidity to the photobioreactor module  112 , and provides a medium for transfer of light from the light source  134  to the photobioreactor conduits  132 . 
     As illustrated in  FIGS. 1 and 6  of the drawings, in some applications of the apparatus  100 , multiple photobioreactor modules  112  may be stacked on top of each other to selectively increase the algal growth capacity of the apparatus  100 . The stacked photobioreactor modules  112  may be stabilized on top of each other according to any suitable technique, as known by those skilled in the art. For example, as illustrated in  FIGS. 10-12 , in some embodiments multiple module receptacles  140 , each having a receptacle seat  142  ( FIG. 9 ), may be provided at respective corners of the top light-transmitting member  128  of each photobioreactor module  112 . Each module receptacle  140  may be fitted with multiple receptacle threads  141  to facilitate threaded insertion of each module receptacle  140  into a corresponding receptacle opening in the corresponding module frame (not illustrated) provided through the top light-transmitting panel  128 . Multiple module frame feet  144  may be provided, at respective corners, through the bottom light-transmitting member  122  of each photobioreactor module  112 . Each module foot  144  may be fitted with multiple foot threads  145  to facilitate threaded insertion of each module foot  144  into a corresponding foot opening (not illustrated) provided through the bottom light-transmitting member  122 . Accordingly, as illustrated in  FIG. 11 , the module feet  144  of an upper photobioreactor module  112  may be seated in the receptacle seats  142  ( FIG. 9 ) of the respective module receptacles  140 , to stabilize the upper photobioreactor module  112  on the lower photobioreactor module  112 . As illustrated in  FIG. 6 , it will be appreciated by those skilled in the art that any number of photobioreactor modules  112  may be stacked in the apparatus  100  to correspondingly increase the algae growing capacity of the apparatus  100 . Moreover, multiple apparatus  100 , each having multiple stacked photobioreactor modules  112 , may be provided in adjacent relationship to increase algae growth capacity while minimizing footprint space occupied by the apparatus  100 . 
     As illustrated in  FIG. 12 , in some embodiments a module lifting shackle  154  may be inserted into each module receptacle opening (not illustrated) provided through the top light-transmitting panel  128  of the uppermost photobioreactor module  112  in the apparatus  100 . Each module lifting shackle  154  may include threads  155  and a loop  156 . A cable (not illustrated) provided on a hoisting apparatus (not illustrated) may be fastened to the shackle loop  156  of each module lifting shackle  154 , to facilitate selective raising and lowering of the uppermost photobioreactor module  112 , with respect to the immediately underlying photobioreactor module  112  of the stack, by operation of the hoisting apparatus. 
     As illustrated in  FIGS. 10 ,  15  and  16 , in some embodiments, a gasket  148  may be interposed between the top light-transmitting member  128  of each photobioreactor module  112  and the bottom light-transmitting member  122  of the next highest photobioreactor module  112  in the stack. As illustrated in  FIG. 16 , each gasket  148  may include multiple conduit openings  149 , which establish fluid communication between the photobioreactor conduits  132  of the respective stacked photobioreactor modules  112 . In some embodiments, at least one center support opening  150  may be provided in the center portion of the gasket  148 , to accommodate the end of at least one of the center plate supports  118 . Corner openings  151  may be provided at the respective corners of each gasket  148 , to accommodate the module receptacles  140  on the lower photobioreactor module  112  and the module feet  144  on the upper photobioreactor module  112 . Accordingly, the gasket  148  may provide a fluid-tight seal between the photobioreactor conduits  132  of adjacent photobioreactor modules  112 . 
     In addition to facilitating the control of light- and temperature-related factors, disclosed apparatus allows for the control of other elements affecting the rate of growth of the algae, such as CO 2  concentration, O 2  levels, and nutrient levels. As illustrated in  FIG. 13  of the drawings, gas  160 , fluid  161 , light  162  and other substances or elements, may be provided as required for sustenance and growth of the algae  133  in each of the photobioreactor conduits  132  of each photobioreactor module  112 . As described above, tThe light  162  may be natural light, artificial light or a combination thereof, provided by the light source  134  ( FIG. 1 ). The gas  160 , fluid  161 , and other elements required for sustenance and growth of the algae  133  may be provided in a growth medium (not illustrated) in which the algae  133  are suspended in each photobioreactor conduit  132 . In some embodiments, each photobioreactor module  112  may include sensors (which are designated schematically as “SENSOR A,” “SENSOR B” and “SENSOR C,” in  FIG. 13 ) adapted to sense various parameters of the gas  160 , fluid  161 , light  162 , or other substances or elements required for sustenance and growth of the algae  133 . For example, in  FIG. 13 , SENSOR A may be a gas sensor  164  that senses the presence, concentration and/or other parameters, of an algae-sustaining gas  160  in the photobioreactor conduits  132 ; SENSOR B may be a fluid sensor  165  that senses the presence, quantity and/or other parameters, of a fluid  161  in the photobioreactor conduits  132 ; and SENSOR C may be a light sensor  166  that senses the presence, spectrum and/or other parameters, of light  162  to which the algae  133  is exposed. The gas sensor  164 , the fluid sensor  165  and/or the light sensor  166 , may be adapted to determine the permissible ranges of concentrations or quantities of the gas  160 , the fluid  161  and/or other substances or elements, and the spectrum, intensity, source and destination within the apparatus  100 , of the light  162 , to facilitate changes to the concentrations, quantities and other parameters, in order to ensure optimum growth of the algae  133  in the photobioreactor conduits  132 . As illustrated in  FIG. 14 , the gas sensor  164 , the fluid sensor  165 , the light sensor  166  ( FIG. 13 ) and any additional sensors, may be provided in one or more of the photobioreactor conduits  132  of each photobioreactor module  112 . Carbon molecules, growth medium and other substances that may be necessary for sustenance and growth of the algae  133 , may be supplied to the algae  133  by various processes, including, but not limited to, an atmospheric or environmental scrubber, compressed concentrate and industrial emissions. In some embodiments, a coolant (not illustrated) may be provided in each photobioreactor conduit  132  to assist in control of internal environmental temperatures. 
     As illustrated in  FIGS. 17 and 18  of the drawings, in some embodiments a flow control device  170  may be provided in each photobioreactor conduit  132  to retain algae  133  therein while enabling algal bioproducts (not illustrated) to flow under the influence of gravity from each photobioreactor conduit  132  and into the respective product transfer tubes  105  of the product transfer assembly  104 . The flow control device  170  may include a device rim  171 , which is attached to the photobioreactor conduit  132  according to the knowledge of those skilled in the art. Multiple, flexible device flaps  172  may extend inwardly from the device rim  171 . A vacuum pump (not illustrated) may be disposed in communication with the product transfer tubes  105  of the product transfer assembly  104 . Accordingly, upon application of reduced pressure to each photobioreactor conduit  132  via actuation of the vacuum pump, the device flaps  172  may be deflected from the closed, planar configuration (indicated by the solid lines in  FIG. 17 ), to the downwardly extending configuration (indicated by the phantom lines in  FIG. 17 ). Therefore, algal bioproducts (not illustrated) may be drawn from the photobioreactor conduits  132 , through the downwardly-deflected device flaps  172  of the flow control device  170 , and into the respective product transfer tubes  105  of the product transfer assembly  104 . 
     In typical application, the apparatus  100  may be used to produce and harvest algal bioproducts (not illustrated) such as algae biomass, algae excretions, and algae derivative products, for example and without limitation. The algal bioproducts may be used to produce algal fuel or other useful product. Accordingly, as illustrated in  FIG. 8 , algae  133  may be placed in each of the photobioreactor conduits  132  of each photobioreactor module  112 . The algae  133  may be suspended in an algal growth medium (not illustrated) containing the gases  160  and fluids  161  ( FIG. 13 ) and any other chemicals, substances and nutrients, that may be necessary for sustenance and growth of the algae  133 . The interior of the photobioreactor conduits  132  may be accessed through the respective openings  123  ( FIG. 7 ) provided in the top light-transmitting panel  128  of the photobioreactor module  112 . Depending upon the production requirements of the algal bioproducts to be harvested from algae  133 , a selected number of the photobioreactor modules  112  may be stacked on top of each other, for example, in the manner that was heretofore described with respect to  FIGS. 10 and 11 . Moreover, as illustrated in  FIG. 6 , multiple apparatus  100  each having a selected number of stacked photobioreactor modules  112 , may be placed in generally adjacent relationship with respect to each other, to further increase the algal growth capacity of the apparatus  100 . 
     The light source  134  ( FIG. 1 ) may be operated to transmit light  162  ( FIG. 13 ) into each photobioreactor conduit  132  of each photobioreactor module  112  through the light transmission cables  135 , the light tubing branches  136  and the light-transmitting members  122 ,  126  and  128 , respectively. The light  162  is transmitted from each light-transmitting member  122 ,  126  and  128 , into each photobioreactor conduit  132 , at the contact surfaces between the light-transmitting member  122 ,  126  and  128 , and each corresponding photobioreactor conduit  132 . Accordingly, the algae  133  are sustained by gases  160 , fluids  161 , light  162 , and nutrients and substances disposed in the growth medium inside each photobioreactor conduit  132 . The gas sensor  164 , the fluid sensor  165 , the light sensor  166  ( FIG. 13 ) and any additional sensors (not illustrated), may indicate the ranges of various parameters of the gas  160 , fluid  161 , light  162 , and other substances to which the algae  133  are exposed in each photobioreactor conduit  132 . The types and quantities of gas  160 , fluid  161 , light  162  and other substances may be adjusted to maintain those elements within the ranges for optimum sustenance and growth of the algae  133  in the photobioreactor conduits  132 . 
     As a result of their growth and metabolism, the algae  133  produce algal bioproducts (not illustrated), which may include, but are not limited to, algae biomass, algae excretions and algae derivative products. The algal bioproducts which are produced by the algae  133  may drain from the photobioreactor conduits  132  of each photobioreactor module  112 , through the product transfer tubes  105  of the product transfer assembly  104 , into the collecting vessel  101  of the apparatus  100 . In some embodiments, a vacuum pump (not illustrated) may be operated to draw the algal bioproducts from each photobioreactor conduit  132 , through the product transfer tubes  105  of the product transfer assembly  104 , into the collecting vessel  101 . The algal bioproducts may then be pumped, transported, dropped or otherwise moved, from the collecting vessel  101  into the product processor  102 . The product processor  102  may transform the algal bioproducts into algal fuel or other product. In applications in which multiple photobioreactor modules  112  are stacked on the product transfer assembly  104  of the apparatus  100 , the gasket  148  ( FIGS. 10 ,  15  and  16 ) is interposed between the photobioreactor modules  112  provides a fluid-tight seal between the photobioreactor conduits  132  of the respective photobioreactor modules  112 . Photobioreactor modules  112  may be selectively removed from, or added to, the apparatus  100  by attaching the module lift plugs  154  ( FIG. 12 ) to the top light-transmitting panel  128  of each added or removed photobioreactor module  112 , in lieu of the module receptacles  140  ( FIG. 11 ), and extending a cable (not illustrated) attached to a hoisting apparatus (not illustrated) through the plug loop  156  of each module lift plug  154 . The hoisting apparatus may then be operated to lift the uppermost photobioreactor module  112  from the apparatus  100 , or to lower an additional photobioreactor module  112  onto the uppermost photobioreactor module  112  of the apparatus  100 . 
     Since many modifications, variations, and changes in detail can be made to the described embodiments herein, it is intended that all matters in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. Thus, the scope of this Disclosure should be determined by the appended claims and their legal equivalence. By way of example, although not shown in the exemplary embodiments, alternative conduit arrangements, such as the incorporation of concentrically arranged conduits, is contemplated. Furthermore, while the exemplary embodiments described and depicted herein detail the withdrawal, or harvesting, of algal material from the bottom of the module, it will be apparent to those skilled in the art that algal material could just as easily be harvested from the top of the modules via installation of, for example, collector tubes and manifold devices.