WO2011011691A2

WO2011011691A2 - Solar energy gathering system, apparatus, and method

Info

Publication number: WO2011011691A2
Application number: PCT/US2010/043059
Authority: WO
Inventors: Frederick M. Morgan; Johan Vanwalsem; Noubar B. Afeyan; James R. Mcintire
Original assignee: Joule Unlimited Inc
Current assignee: Joule Unlimited Inc
Priority date: 2009-07-24
Filing date: 2010-07-23
Publication date: 2011-01-27
Anticipated expiration: 2012-01-24
Also published as: WO2011011691A3

Abstract

The present invention provides solar energy gathering systems, apparatuses and solar gathering methods that capture a greater portion of the energy of an incident spectrum of electromagnetic radiation, typically, solar radiation, than is captured in conventional photobioreactors while allowing for the prevention of deleterious effects caused by certain portions of the incident spectrum of solar radiation.

Description

SOLAR ENERGY GATHERING SYSTEM, APPARATUS, AND METHOD

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 61/228,414, filed on July 24, 2009. The entire teachings of the above application are incorporated herein by reference.

BACKGROUND OF THE INVENTION

As the world's energy demands increase and energy production from nonrenewable sources becomes more expensive, difficult, and harmful to the

environment, the desire to capture energy from the sun has correspondingly increased.

Photobioreactors employing sunlight have been described for the production of biofuels from microorganisms. Suitable microorganisms, typically, phototrophic microorganisms, are grown or propagated in these photobioreactors using solar energy for the production of biomass or the production of specific compounds. However, phototrophic microorganisms contain proteins optimized to absorb light at particular wavelengths, and therefore only effectively capture a fraction of the spectrum of electromagnetic radiation provided by the sun. Furthermore, portions of the spectrum, particularly ultraviolet radiation, are harmful to phototrophic microorganisms, and exposure of a culture of phototrophic microorganisms to infrared radiation can lead to elevated temperatures that are less than optimal, thereby necessitating heat mitigation problems.

There is, therefore, a need for systems, apparatuses and methods that capture a greater portion of the broad spectrum energy emitted by solar radiation while avoiding the deleterious effects of certain portions of the spectrum. SUMMARY OF THE INVENTION

One embodiment of the present invention is a solar energy gathering system. The solar energy gathering system includes a photobioreactor including an enclosed volume for containing a phototrophic microorganism, one or more light energy converting devices, and a solar concentrator that includes a first surface to receive a spectrum of solar radiation, a second surface to provide concentrated light, and a third surface that provides light which has passed through the solar concentrator. The one or more light energy converting devices are positioned to receive the concentrated light and the enclosed volume is positioned to receive the light that has passed through the solar concentrator.

Another embodiment is an apparatus including a light energy converting device and photobioreactor, each coupled to a solar concentrator. The solar concentrator is adapted to concentrate electromagnetic radiation of at least one wavelength towards the light energy converting device and to pass light through the solar concentrator onto the photobioreactor.

Another embodiment is a solar energy gathering method. The solar energy gathering method includes arranging a photobioreactor to receive a spectrum of solar radiation, concentrating a spectral part of the received spectrum of solar radiation towards a light energy converting device, passing through a spectral part of the received spectrum of electromagnetic radiation to an enclosed volume containing a phototrophic microorganism, and using electromagnetic radiation that passed through in photosynthesis in the phototrophic microorganism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a solar energy gathering device featuring a photobioreactor with an integrated solar concentrator and photovoltaic cell.

FIG. 2 is a perspective view of one embodiment of a solar concentrator suitable for use in the present invention. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0001] A description of preferred embodiments of the invention follows. While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details can be made therein without departing from the scope of the invention encompassed by the appended claims.

[0002] The following explanations of terms and methods are provided to better describe the present invention and to guide those of ordinary skill in the art in the practice of the present invention. As used herein, "comprising" means "including" and the singular forms "a" or "an" or "the" include plural references unless the context clearly dictates otherwise. For example, reference to "comprising a phototrophic microorganism" includes one or a plurality of such phototrophic microorganisms. The term "or" refers to a single element of stated alternative elements or a combination of two or more elements, unless the context clearly indicates otherwise.

[0003] Unless explained otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. The materials, methods, and examples are illustrative only and not intended to be limiting. Other features of the invention are apparent from the following detailed description and the claims.

[0004] In accordance with the present invention, an illustrative solar gathering system is shown in FIG. 1. The solar gathering system 100 includes an infrared filter 110, at least one solar concentrator 120, and a photobioreactor 140 having an enclosed volume. The enclosed volume of the photobioreactor 140 is the totality of all the channels 145. The photobioreactor 140 typically includes inlets and outlets for growth media and carbon sources (e.g., CO₂) (not shown). Typically, the photobioreactor 140 is enclosed by corrugated panels made by thermo forming plastic materials such as polypropylene, polyethylene, polyacrylate and / or polycarbonate sheets. One of skill in the art will recognize that the materials of construction are not limited to thermoforming processes nor to the polymers above, and it is within routine skill to select alternative manufacturing processes and / or materials of construction. The panels are transparent or at least translucent to at least one wavelength of light. The corrugation can be in various geometric configurations such as rectangular, trapezoidal, triangular, circular, etc,

[0005] The photobioreactor 140 encloses a volume containing phototrophic microorganisms, such as algae or cyanobacteria. In an even more typical embodiment, the photobioreactor 140 contains a plurality of rectangular channels 145 in fluid communication that provide structural support for the solar concentrator 120. Rectangular channels 145 are shown, but other shapes of channels are suitable. The infrared filter 110 reduces the amount of infrared radiation incident from the sun that penetrates to the photobioreactor 140, thereby reducing the need for heat mitigation to maintain the photobioreactor 140 at an operational temperature. The infrared filter 110 can be a filter that removes light of certain wavelengths or it can even be a semi-transparent infrared photovoltaic cell, as described more fully in "STRUCTURES AND APPARATUSES INCLUDING PHOTOVOLTAIC

CELLS," PCT International Publication Number WO 2005/101525 A2, filed on April 14, 2005 and published on October 27, 2005. The relative position of the infrared filter 110 and the solar concentrator 120 can be switched, such that the infrared filter 110 is between the solar concentrator and the photobioreactor 140.

[0006] A light energy converting device 150 is attached to and / or in optical communication with at least one side of the solar concentrator 120. The light energy converting device 150 can be, for example, a photovoltaic cell, a solar thermal electric device, or a solar thermal heating device. In the drawing shown, the light energy converting device 150 is on the right side, but it can be on the front, back, or left side, or it can be on multiple sides. Different types of light energy converting devices can be used on different sides of the solar concentrator. The solar concentrator 120 need not have multiple sides. For example, it can be circular in shape. The light energy converting device 150 need not be directly attached to the solar concentrator 120. There can be intervening materials, such as translucent objects or optical fibers that optically couple the solar concentrator 120 to the light energy converting device 150. Alternatively, there can simply be intervening air space. Typical embodiments can include more than one solar concentrator and more than one photovoltaic cell.

[0007] Another embodiment of a suitable solar concentrator is shown hi FIG. 2. The solar concentrator 200 includes a first surface 230 that receives electromagnetic radiation 235 from a source of radiation, typically the sun although it can be other sources of light, a second surface 240 to provide concentrated light 245, and a third surface 250 that provides light 255 which has passed through the solar concentrator 200. The first surface 230 need not be exposed to the air, but can have an additional surfaces or layers on top of it, such as a anti-scratch, anti-condensate, anti-dust, and other protective layers, as well as reflective and semi-transparent layers. In embodiments incorporating multiple solar concentrators, the third surface 250 of a first solar concentrator can directly abut the first surface 230 of a second solar concentrator. Alternatively, the two solar concentrators can be separated by protective films or layers, or simply a layer of air or other intervening gas. The first surface 230 need not directly receive the electromagnetic radiation. Radiation can be directed or reflected towards the first surface by, e.g., a mirror. The solar concentrator is positioned to receive the concentrated light from the light source. Generally, this means the solar concentrator is situated between the sun and the earth, and can include placement on top of buildings, along roadways, and generally any location where ambient sunlight is not obstructed.

[0008] The solar concentrator 200 includes a dye layer 210 and a waveguide layer 220. In a preferred embodiment, the waveguide 220 is a glass material, but it can be other materials with a high refractive index. Incoming electromagnetic radiation 235 is received by a first surface 230. The second surface 240 provides concentrated light 245 and the third surface 250 provides light 255 that has passed through the solar concentrator 200. The dye can be deposited onto the waveguide by various methods, including thermal evaporation or solution processing, or it can be sprayed on or painted on. [0009] A "spectrum of electromagnetic radiation" as used herein, refers to electromagnetic radiation of a plurality of wavelengths, typically including wavelengths in the infrared, visible and/or ultraviolet light. The electromagnetic radiation spectrum is provided by an electromagnetic radiation source that provides suitable energy within the ultraviolet, visible, and infrared, typically, the sun.

[0010] Suitable light energy converting devices convert energy in the form of electromagnetic radiation into other forms of energy. Examples include

photovoltaic cells including thin-film solar cells, organic solar cells, solar thermal electric systems, and solar thermal heating systems.

[0011] As used herein, "concentrating" a spectrum of electromagnetic radiation refers to guiding the electromagnetic radiation towards one or more locations while changing the spectral power distribution of the electromagnetic radiation such that the number of photons per unit area and unit time increases for at least one wavelength of the spectrum of electromagnetic radiation. For example,

electromagnetic radiation can be guided to a second surface of a solar concentrator by total internal reflection within the solar concentrator. Typically, the solar concentrator comprises a waveguide of a material of high refractive index that guides the electromagnetic radiation. Suitable waveguides and the physical processes involved are described in Michael J. Currie et al., High-Efficiency Organic Solar Concentrators for Photovoltaics, 321 Sci. 226 (2008), and an apparatus suitable for concentrating light in such manner is depicted in FIG. 2. The result is light having a higher concentration along a plane perpendicular to the direction of travel than the incident light of the same wavelength.

[0012] As used herein, "concentrated light" refers to a spectrum of electromagnetic radiation that has been concentrated. Suitable solar concentrators allow a portion of a spectrum of solar radiation to pass through the solar concentrator to be provided or emitted by a third surface of the solar concentrator. An example of a solar concentrator suitable for use in this apparatus is FIG. 2. The dye layer can include at least one dye, such as 4-(dicyanomethylene)-2-/-6wfy/-6-(l, 1,7,7- tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) or platinum

tetraphenyltetrabenzoporphyrin [Pt(TPBP)]. The dye layer is not limited to these two dyes, and can include other dyes known in the art. The dye is doped into a host medium, such as tris(8-hydroxyquinoline) aluminum (AIQ₃). The host material is not limited to Al Q₃, but can include other host materials known in the art. The dyes can be phosphors or fluorophors. Alternatively, the solar concentrator could make use of quantum dots, such as those provided by QD Vision, Inc. of Watertown, MA.

[0013] Photobioreactor: A photobioreactor apparatus, bioreactor or reactor is used interchangeably to describe an apparatus, device or system that supports a biologically active environment. For instance, a bioreactor can be a vessel wherein a chemical process involving photosynthesis in organisms is carried out or

biochemically active substances are derived from such organisms. Such bioreactors can support activities for either aerobic or anaerobic organisms. These bioreactors are commonly cylindrical, ranging in size from liters to cubic meters, and are often made of stainless steel. Bioreactors that are adapted to allow use of light energy in the cultivation or organisms are typically referred to as photobioreactors and commonly employ transparent materials such as glass or plastic to allow light to enter the interior of the bioreactor. On the basis of mode of operation, a bioreactor can be classified as batch, fed batch or continuous (e.g. continuous stirred-tank reactor model). An example of a bioreactor is the chemostat, which maintains a substantially static chemical environment. Organisms growing in photobioreactors can be suspended or immobilized. Various inventive embodiments are directed to photobioreactor apparatus designs and to methods and systems utilizing

photobioreactor apparatus in a solar biofactory as is described throughout.

Photobioreactor apparatuses suitable for the present invention are closed bioreactors, as contrasted with open bioreactors, such as a pond or other open body of water, open tanks, open channels, etc. Typically, the photobioreactors have a plurality of channels in fluid communication. Also, typically, the photobioreactor have planar exteriors or panels, but they can be curved as well. Further suitable photobioreactors are disclosed in "SOLAR BIOFACTORY, PHOTOBIOREACTORS, SYSTEMS AND METHODS FOR PRODUCING PRODUCTS," U.S. Provisional Patent Application No. 61/201,548, filed on December 11, 2008, which is attached hereto as Exhibit A.

[0014] As used herein, "photosynthetically active" refers to microorganisms that are capable of physiochemical absorption of light. [0015] "Physiochemical absorption" and "physiochemical processes" refer to the processes occurring in photosynthetic organisms involving absorption of a photon by an atom or molecule and promotion to an excited electronic state that further promotes chemical reactivity.

[0016] As used herein, "excreting ethanol" refers to generation of ethanol by phototrophic organisms through biosynthetic pathways.

[0017] "Directly" and "direct exposure" refer to the incident light from the sun or other suitable light source. Incident light that is not at least received by the first surface directly exposes the photobioreactor.

[0018] Different microorganisms optimally capture light at different wavelengths, as described more fully in "STRUCTURES AND APPARATUSES INCLUDING PHOTOVOLTAIC CELLS," PCT International Publication Number WO

2005/101525 A2, filed on April 14, 2005 and published on October 27, 2005.

Further, different light energy capturing devices optimally capture light at different wavelengths. Therefore, typically the solar concentrator is adapted to emit light from a third surface suitable for, and preferably optimized for, a chosen phototrophic microorganism while being adapted to emit light from a second surface suitable for, and preferably optimized for, a chosen light energy converting device. The light emitted and captured can be ultraviolet, visible and/or infrared. Adapting and optimizing the solar concentrator requires selecting the appropriate dye or dyes from those dyes that are well known in the art.

[0019] "Biofuel" refers to any fuel that derives from a biological source, including one or more hydrocarbons, one or more alcohols, one or more fatty esters or a mixture thereof. Typically, ethanol or other liquid hydrocarbon fuels can be produced.

[0020] "Phototrophs" or "photo autotrophs" are organisms that carry out photosynthesis such as, eukaryotic plants, algae, protists and prokaryotic

cyanobacteria, green-sulfur bacteria, green non- sulfur bacteria, purple sulfur bacteria, and purple non- sulfur bacteria. Phototrophs include natural and engineered organisms that carry out photosynthesis and hyperlight capturing organisms. [0021] As used herein, "organisms" encompasses autotrophs, phototrophs, heterotrophs, engineered light capturing organisms and at the cellular level, e.g., unicellular and multicellular.

[0022] A "bio synthetic pathway" or "metabolic pathway" refers to a set of anabolic or catabolic biochemical reactions for converting (transmuting) one chemical species into another. For example, a hydrocarbon biosynthetic pathway refers to the set of biochemical reactions that convert inputs and/or metabolites to hydrocarbon product-like intermediates and then to hydrocarbons or hydrocarbon products.

Anabolic pathways involve constructing a larger molecule from smaller molecules, a process requiring energy. Catabolic pathways involve breaking down of larger molecules, often releasing energy.

[0023] As used herein, "light" generally refers to sunlight but can be solar or from artificial sources including incandescent lights, LEDs, fiber optics, metal halide, neon, halogen and fluorescent lights and solar light,

[0024] The term "PAR" is short for photosynthetically active radiation and is measured in μE/m²/s.

[0025] Throughout this specification and claims, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0026] The solar energy gathering system 100 requires electricity for its operation. Electricity is required for, e.g., pumps and systems that introduce CO₂ and that circulate the media in which the phototrophic organisms are growing, as well as fans or other temperature regulation means. In one embodiment, a significant portion, preferably, all of the electricity required for the solar energy gathering system 100 is provided by the one or more light energy converting devices 150 and / or an energy storage system or device. An energy storage system includes a rechargeable battery system that can be charged during daylight by the one or more light energy converting devices 150 and used to power the solar energy gathering system 100 during the night time. In some embodiments, the solar energy gathering system 100 is self-contained and does not require external sources of electricity. In some embodiments, the solar energy gathering system 100 can be operated in remote areas where it is not connected to the utility grid, for example in the desert.

[0027] In one embodiment, the solar energy gathering system 100 is situated nearby to a power plant or other utility or manufacturing plant that that generates CO₂. Coupling the solar energy gathering system to the flue gas outputs of utility plants can help reduce the CO₂ emissions into the atmosphere.

[0028] Some embodiments reduce the amount of infrared radiation reaching the photobioreactor thereby mitigating, partly or entirely, the difficulty in maintaining photobioreactors within an optimal temperature range. Maintaining thermal homeostasis requires energy, typically to cool the system during the day and heat the system at night, and therefore effectively decreases the net energy captured. Further, in some embodiments, conversion of ultraviolet radiation into lower energy radiation mitigates, partly or entirely, the deleterious effects of UV radiation damage to cells in the photobioreactor. Simultaneous reduction of UV and IR radiation substantially facilitates the growth of phototrophic microorganisms. In addition, even distribution of light within the photobioreactor can be achieved. Accordingly, the solar energy gathering systems can provide optimal growth effect of phototrophic

microorganisms. As a result, various adaptations of the solar gathering system can increase the photosynthetic rate of the phototroph, increase the growth rate of the phototroph and/or increase the product yield from the phototroph.

[0029] The integrated photobioreactor design is simple to install and maintain, providing for reduced operating and maintenance costs. The present invention allows for efficient capture of solar energy requiring little to no solar tracking. The ability to derive electrical energy can permit installation and operation in remote locations that are not otherwise connected to stable electricity sources. A space- efficient design permits easier packing, shipping, and installation. Furthermore, a space-efficient design increases the amount of energy captured from the sun over a given surface area.

[0030] By passing solar light through a solar concentrator, the present invention simultaneously alters the spectrum of electromagnetic radiation, guides a portion of the spectrum towards a light energy converting devices, and permits other portions of the spectrum to impinge upon the photobioreactor. Guiding a portion of the altered spectrum towards the light energy converting devices effectively

concentrates the portions of the incident spectrum thereby requires a smaller surface area of light energy converting devices and achieving cost savings.

[0031] The present invention does not require mirrors tracking the movement of the sun across the sky, although such mirrors can also be incorporated. A mirror-less design simplifies installation and minimizes operational and maintenance costs. The present invention also does not require the use of fiber optic cables that optically couple the solar radiation to the photobioreactor, although the use of fiber optic cables is possible.

[0032] In a further embodiment of the present invention multiple solar energy converting systems/devices as described above can be connected such that they in fluid communication, for example in a serial or parallel manner, or both. For example, the photobioreactor inlets and outlets can be coupled such that the outlet of one system is the inlet of another system.

[0033] In another embodiment, the systems or devices of the preceding paragraph are used for gathering solar energy, while the absorption and conversion of input CO₂ is optimized by employing sweep gas, for example, filtered air. One of ordinary skill in the art will recognize that it is a matter of routine skill to

incorporate multiple aspects of the various embodiments together. For example, the integrated photobioreactor, light energy converting devices, and solar concentrator with a planar first surface can direct a suitable spectrum towards the second surface and a suitable spectrum towards the third surface. The spectrums are suitable to the devices or apparatuses that receive the spectrum at that surface, e.g., the light energy converting device at the second surface and the photobioreactor at the third surface. The light energy converting device can be a photovoltaic cell, and the suitable spectrum is optimized for electricity generation by that particular photovoltaic cell. Similarly, the photobioreactor can contain microorganisms that excrete ethanol or various other carbon-based products of interest (PCT/US2009/035937), and the spectrum is suitable for photo synthetic activity in the micro or ganims. The solar concentrator can absorb light of a first wavelength, preferably in the ultraviolet region, and emit light of a second wavelength, wherein the second wavelength is longer than the first wavelength. Furthermore, the electricity generated by the photovoltaic cell can power the photobioreactor.

[0034] Additionally, the second surface is sized to optimize electricity generation by decreasing the surface area of the second surface relative to first surface, thus concentrating at least one wavelength towards the photovoltaic cell. Furthermore, the solar concentrator reduces exposure of the microorganisms within the photobioreactor to ultraviolet light while permitting photosynthetically useful light to pass through the solar concentrator, thus reducing the deleterious effects of ultraviolet light on microorganisms. The use of an infrared filter or semi-transparent infrared photovoltaic cell can also reduce the amount of infrared radiation reaching the photobioreactor volume. Infrared light heats the photobioreactor, thus requiring additional energy expenditures to maintain the photobioreactor within an optimal range.

[0035] The photobioreactor designs can be used with many different solar concentrator designs as well. For example, the selection of the particular dye or quantum dot is independent of the type of photobioreactor. Any aspects of the embodiments can also be combined with the use of reflective mirrors, though this is not necessary for operation. One of ordinary skill in the art will recognize that many routine changes can be made to the embodiments that incorporate the essential teachings of the present invention.

[0036] Although discussed with respect to solar radiation, a person of ordinary skill in the art will recognize that this device is not limited to solar radiation, and that other sources of light can be used. For example, light could be provided during the night by energy generated and stored from daytime operation of the light energy capturing device. Alternatively, non-solar sources of light could be used entirely to permit continuous 24-hour operation.

[0037] In various preferred embodiments, the energy required to operate a solar energy gathering system or apparatus can be generated on site, for example, using the solar energy gathering system or apparatus, that is, the system or apparatus is self-contained. Preferably, the self-contained solar energy gathering system or apparatus provides the energy needed to run the various components such as pumps, fans, cooling systems, frames for positioning, product separation mechanisms, monitors (pH, temperature, pressure, light, turbulence, mixing etc.) or any such apparatus utilizing electricity. One of the key advantages of a self-contained solar energy gathering system or apparatus is the flexible location and placement of the system without being hindered by the fixed location of the power source.

[0038] Alternative embodiments include instances where the solar energy gathering system is connected to the grid, e.g., a source of electricity. In cases where excess electricity generated, it can be transferred and stored on the grid.

[0039] In further embodiments of the present invention, the solar energy gathering systems as described herein, further comprise a light energy converting device on top or above the solar concentrator (on part or on the entire solar concentrator) such that solar energy is received by the light energy converting device before it is concentrated. The solar concentrator receives (on part or on the entire solar concentrator surface) a spectrum of radiation that has passed through the light energy converting device. Typically, the light energy converting device would be one or more photovoltaic cells (connected in a panel) including, for example, thin- film solar cells and organic solar cells. Preferably, the light energy converting device is substantially transparent with regard to the spectrum of radiation that is suited for concentration with the solar concentrator and with regard to

photosynthetically active radiation required to culture one or more phototrophic microorganism in the photobioreactor.

[0040] The relevant teachings of all patents, published patent applications and literature references cited herein are incorporated by reference in their entirety.

Claims

CLAIMS What is claimed is:

1. A solar energy gathering system comprising:

(a) a photobioreactor including an enclosed volume for containing a phototrophic microorganism;

(b) one or more light energy converting devices; and

(c) a solar concentrator comprising a first surface to receive a spectrum of solar radiation, a second surface to provide concentrated light, and a third surface that provides light which has passed through the solar concentrator; wherein the one or more light energy converting devices are positioned to receive the concentrated light and the enclosed volume is positioned to receive the light that has passed through the solar concentrator.

2. The system of claim 1, wherein the solar energy gathering system requires electricity for its operation and a significant portion of the electricity is generated by the one or more light energy converting devices.

3. The system of claim 1 , wherein the first surface is planar,

4. The system of claim 1, wherein the photobioreactor, the one or more light energy converting devices and the solar concentrator are part of an integrated system.

5. The system of claim 1, wherein the position of the first surface relative to the enclosed volume is fixed.

6. The system of claim 1, wherein the one or more light energy converting devices are adapted to generate electricity in the presence of a first spectrum of electromagnetic radiation, the phototrophic microorganism performs photosynthesis hi the presence of a second spectrum of electromagnetic radiation, the first and second spectrum are different, the spectrum of the concentrated light at least overlaps with the first spectrum of the

electromagnetic radiation and the spectrum of the light that has passed through the solar concentrator at least overlaps with the second spectrum of the electromagnetic radiation.

7. The system of claim 6, wherein the first and second spectrum have

substantially no overlap, the spectrum of the concentrated light substantially entirely overlaps with the first spectrum of the electromagnetic radiation and the spectrum of the light that has passed through the solar concentrator substantially entirely overlaps with the second spectrum of the

electromagnetic radiation.

8. The system of claim 1, wherein the area of the first surface is sized to

prevent, partly or completely, the spectrum of solar radiation to reach the enclosed volume, and the second surface area is sized to optimize generation of electricity by the one or more light energy converting devices.

9. The system of claim 1 , wherein the solar concentrator is adapted (i) to

reduce, partly or completely, direct exposure of the enclosed volume to infrared light, (ii) to increase the intensity per surface area of the second surface, of light suitable for energy generation by the one or more light energy converting devices, and (iii) to optimize photosynthetic activity in phototrophic microorganisms exposed to light provided by the third surface.

10. The system of claim 1 , wherein the light provided by the third surface

comprises light of one or more wavelengths suitable to optimize

photosynthesis in the phototrophic microorganism.

11. The system of claim 10, wherein the light provided by the third surface

comprises significantly less ultraviolet light than the ultraviolet light received by the first surface.

12. The system of claim 11 , wherein the light provided by the third surface comprises significantly less infrared light than the infrared light received by the first surface.

13. The system of claim 1 , wherein the solar concentrator partially encloses the enclosed volume.

14. The system of claim 1, wherein at least part of the third surface of the solar concentrator is at least part of an inner surface of the enclosed volume.

15. The system of claim 1 , wherein the enclosed volume comprises a plurality of channels, the channels being in fluid communication.

16. The system of claim 1 , wherein the channels are shaped and arranged to increase surface area available to incident light.

17. The system of any one of claims 1-16, wherein the solar concentrator

comprises a thin-film layer coupled to a top surface of a planar waveguide, the thin-film layer providing the first surface, the bottom surface of the flat- sheet waveguide providing the third surface, and the second surface being provided by a side surface of the solar concentrator.

18. The system of any one of claims 1-17, wherein the enclosed volume contains phototrophic microorganisms.

19. An apparatus comprising a light energy converting device and

photobioreactor, each coupled to a solar concentrator, wherein the solar concentrator is adapted (i) to concentrate electromagnetic radiation of at least one wavelength towards the light energy converting device and (ii) to pass visible light through the solar concentrator onto the photobioreactor.

20. The apparatus of claim 19 wherein the solar concentrator absorbs light of a first wavelength and emits light of a second wavelength.

21. The apparatus of claim 20, wherein the second wavelength is longer than the fust wavelength.

22. The apparatus of claim 21, wherein the first wavelength is within the UV spectral range,

23. The apparatus of claim 22, wherein the second wavelength is within the visible spectral range.

24. The apparatus of any one of claim 19 to 23, wherein the light energy

converting device receives the light of the second wavelength,

25. The apparatus of any one of claims 19-24, wherein the concentration of light at the second wavelength is greater than the concentration of light at the first wavelength.

26. The apparatus of claim 19, wherein the visible light that passes through the solar concentrator onto the photobioreactor is photo synthetically active.

27. The apparatus of any one of claims 19-26, wherein the solar concentrator comprises a thin-film layer coupled to a wave guide.

28. The apparatus of claim 27, wherein the thin film layer comprises an organic dye doped into a host material,

29. The apparatus of any one of claims 19-28, wherein the light energy

converting device is optically coupled to a second surface of the solar concentrator, the second surface providing concentrated light.

30. A solar energy gathering method comprising: (a) arranging a photobioreactor to receive a spectrum of solar radiation;

(b) concentrating a spectral part of the received spectrum of solar

radiation towards a light energy converting device;

(c) passing through a spectral part of the received spectrum of solar radiation to an enclosed volume containing a phototrophic microorganism, the enclosed volume being part of the photobioreactor; (d) using electromagnetic radiation that passed through in step (c) in photosynthesis in the phototrophic microorganism,

31. The method of claim 30, wherein steps (b) and (c) are performed without reflecting electromagnetic radiation on an external surface.

32. The method of claim 30, wherein step (b) comprises shifting light of at least one wavelength towards longer wavelength.

33. The method of claim 30, wherein step (b) comprises shifting light of at least one wavelength in the ultraviolet range to a wavelength in the visible range that is suitable for photovoltaic energy generation.

34. The method of claim 33, further comprising filtering, partly or completely, infrared light from the spectrum of electromagnetic radiation received in step (a).

35. The method of claim 30, further comprising (e) generating electricity with the light energy converting device.

36. The method of claim 33, further comprising (f) using electricity generated by the light energy converting device to provide a significant portion of the electricity required in operating the photobiore actor ,

37. The method of claim 30, wherein the spectrum of electromagnetic radiation in step (a) is received by a first surface of a solar concentrator, and the method further comprises maintaining the position of the first surface during the day.

38. The apparatus of any one of claims 19-29, wherein the apparatus is

optimized to require a minimal amount of utility grid electricity.

39. The apparatus of any one of claims 19-29, wherein the apparatus is self- contained.

40. The apparatus of any one of claims 19-29, wherein the apparatus is adapted to generate a fuel or chemical.

41. The apparatus of claim 40, wherein the apparatus is adapted to generate an alcohol or hydrocarbon.

42. The system of any one of claims 1-18, wherein the system is optimized to require a minimal amount of utility grid electricity.

43. The system of any one of claims 1-18, wherein the system is self-contained.

44. The system of any one of claims 1-18, wherein the system is adapted to

generate a fuel or chemical.

45. The system of claim 44, wherein the system is adapted to generate an alcohol or hydrocarbon.