AU2020273381A1

AU2020273381A1 - Solar concentration system

Info

Publication number: AU2020273381A1
Application number: AU2020273381A
Authority: AU
Inventors: Alex Geoffrey LEHMANN
Original assignee: Peritar Pty Ltd
Current assignee: Peritar Pty Ltd
Priority date: 2019-11-20
Filing date: 2020-11-20
Publication date: 2021-06-03

Abstract

A solar concentration system comprises a concentrating omni-directional fluid lens and a plurality of beam combiners optically coupled with respective optic fibre bundles for receiving, concentrating, and directing light reflected from a heliostat towards a 5 furnace. The system may comprise a surround field of heliostats, or a parabolic dish reflector. Heat may also be extracted from the lens fluid. - 46- 305516224 1/4 6 ~- 5 4 1 3 7 22 Figure 1 30530 304 306 301 2 4 Figure 2 s

Description

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SOLAR CONCENTRATION SYSTEM

1 Field of the Invention

This disclosure relates to a solar concentration system. More particularly, though not exclusively, the disclosure relates to a concentrating solar receiver comprising an omni-directional fluid lens for use with a surround field of heliostats or a parabolic dish reflector.

2 Background Renewable energy is becoming increasingly popular with growing concerns over the environmental impact of nuclear, fossil-fuel, and hydroelectric energy sources. The solar furnace has the potential to complement other renewable technologies in the transition to cleaner energy systems, with unique capabilities in the electricity generation, transport, and industrial process heat sectors. The ability to deliver highly concentrated sunlight in a controlled way is useful for a wide range of applications such as high temperature chemical processing and high concentration photovoltaics.

While some systems have been demonstrated at small scale, limited progress has been made in scaling the designs for industrial applications.

United States Patent No. 5,501,743, to Matthey Cherney, for example, discloses a solar power-generating system with limited solar concentration for domestic applications. The disclosed design utilises an optional parabolic reflector and an array of collecting lenses each focussed on an optical fibre bundle which guides solar energy to an electrical- and/or heat-generating stack.

United States Patent Publication No. 2011/0088684, to Raja Singh Tuli, discloses a solar concentrator intended for supplying energy to a single household. The disclosed beam-down design utilises a stationary Fresnel primary reflector, a movable secondary redirecting reflector, and a stationary remote radiation absorber. In one embodiment, the use of a fluid lens associated with the secondary redirecting reflector is disclosed to enable adjustment of the focal length of the light coming from the primary concentrating reflector.

United States Patent No. 8,705,917, to Jorge A Garza, discloses a solar energy device which may be used for remote lighting. The device comprises a number of light collectors each consisting of a transparent solid sphere of around four inches in diameter. Each light collector transmits incident sunlight and emits the light to a bundle of optical fibers, which transmit the light to another location for illumination.

The unsuitably of these and other such systems, and the lack of progress towards industrial-scale systems, is due to technical and economic barriers. Common issues include the high cost of production of large structures and issues with centralising energy collected from decentralised modular arrays (especially dishes). Conventional solar furnaces such as the horizontal furnace, or the beam-down solar tower concept, suffer from the requirement of needing extremely large and costly secondary reflectors to reach high power ranges. More generally, the issues of low numerical aperture for secondary optics means that the primary solar collectors are relatively small, limiting the total power collection capability and cost-effectiveness. Excess heat, and dissipation of that heat, can also be problematic at the high levels of concentration required for industrial applications. Another important factor that has limited uptake of solar furnace technology is the issue of integration of a suitable solar concentrator with the requirements of the furnace. The limitations of the concentrator optics make it inflexible when meeting energy requirements of furnace applications.

3 Object It is an object to provide one or more of a lens, a concentrating solar receiver, and/or a solar concentration system which overcomes or ameliorates one or more disadvantages of the prior art, or alternatively to at least provide the public or industry with a useful alternative.

4 Summary

In a first aspect, there is provided a solar concentration system comprising: a plurality of heliostats; a support tower extending upwardly above the plurality of heliostats; an omni-directional lens mounted to the tower to receive and focus light reflected from the plurality of heliostats; a plurality of beam combiners mounted to the lens and configured to receive focussed light from the lens; and a plurality of optic fibre bundles each comprising at least one optic fibre, each optic fibre bundle being coupled with one of the plurality of beam combiners and configured to receive concentrated light therefrom and direct it towards a furnace. Preferably the plurality of heliostats each comprise a concentrating heliostat such as a toroidal heliostat.

Preferably the lens is statically mounted in the tower.

Preferably the lens is configured to isolate the light received from the plurality of heliostats into bands of reduced numerical aperture.

Preferably the lens comprises a substantially spherical lens. Alternatively, the lens may comprise a fisheye lens.

Preferably the lens comprises a fluid lens, and more preferably a substantially rigid outer lens shell containing a lens fluid. Preferably the lens shell is transparent across one or more of the ultraviolet, visible and infrared wavelength ranges. Preferably the lens shell has high shock resistance and mechanical strength.

Preferably the lens shell comprises an antireflective and/or low emissivity coating.

Preferably the lens fluid has a refractive index selected so that the lens concentrates substantially all of the light received from each of the plurality of heliostats into one or more of the plurality of beam-combiners.

Preferably the lens fluid has a refractive index higher than that of a material of the outer shell.

Preferably the lens fluid has a refractive index of between 1.5 and 2.0, and more preferably between 1.82 and 1.95, in use.

Preferably the lens fluid comprises a molten salt, more preferably one or more of PbCl 2, KC, or NaCl.

Alternatively, the lens fluid may comprise an oil, more preferably a synthetic heat transfer fluid or a high refractive index immersion liquid.

Preferably the material of the lens shell comprises glass, fused silica, quartz, or a synthetically prepared variant of quartz.

Preferably the material of the lens shell has a refractive index between that of air and the lens fluid.

Preferably a diameter of the lens is approximately equal to the size of an image reflected upon the lens by one of the plurality of heliostats.

Preferably a back side of the lens comprises a plurality of integral back side lenses to refocus incident light into one of the plurality of beam combiners.

Preferably the plurality of back side lenses each comprise a concave depression in the interior surface of a back side of the lens shell. Alternatively, the plurality of back side lenses may comprise a convex protrusion from the interior surface of the back side of the lens shell.

Preferably the lens comprises a fluid inlet and a fluid outlet, and the system further comprises a heat exchanger coupled with the fluid inlet and fluid outlet by fluid transfer lines, for circulating the lens fluid and extracting heat therefrom.

Preferably the fluid transfer lines comprise a trace heater.

Preferably the lens fluid is selected to absorb a predetermined part of the spectrum of the light.

Preferably the lens fluid further comprises added particles with selected spectral absorption characteristics, more preferably particles selected to absorb a predetermined portion of the spectrum of the light.

Preferably the lens comprises a substantially spherical dome and a cap sealed together to define a cavity to contain the lens fluid. Preferably the plurality of back side lenses are provided in the cap. Preferably the fluid inlet and the fluid outlet are provided in or through the cap. Preferably the plurality of beam combiners are mounted to the cap.

Preferably each of the plurality of heliostats is mapped to a corresponding one of the plurality of beam combiners in a one-to-one configuration.

Alternatively, each of the plurality of heliostats is mapped to two or more of the plurality of beam combiners in a one-to-many configuration.

Alternatively, each of the plurality of heliostats is mapped to one of the plurality of beam combiners in a many-to-one configuration.

Alternatively, each of the plurality of heliostats is mapped to two or more of the plurality of beam combiners in a many-to-many configuration.

Preferably each of the plurality of beam combiners are arranged adjacent to a respective one of the plurality of back side lenses so as to receive light therefrom.

Preferably the plurality of beam combiners are arranged substantially radially about a portion of the lens.

Preferably distal ends of the plurality of optic fibre bundles are arranged substantially radially with respect to the furnace to concentrate emitted light from the plurality of optic fibre bundles on the furnace.

Preferably each of the plurality of optic fibre bundles comprises a plurality of optic fibres.

Preferably each of the plurality of optic fibres is fused to one of the plurality of beam combiners.

Preferably the plurality of beam combiners each have a polygonal cross-section, and more preferably a hexagonal cross-section.

Preferably the system further comprises the furnace. Preferably the furnace is mounted in the tower. Alternatively, the furnace may be provided adjacent the tower, or adjacent the system.

Preferably the furnace comprises a boiler, high concentration photovoltaic cells, a thermophotovoltaic system or thermochemical reaction chamber, gas turbine, heat exchanger, or any other apparatus requiring concentrated radiation.

In a second aspect, there is provided an omni-directional lens for use in a concentrating solar system comprising a plurality of heliostats, the lens comprising a substantially rigid outer lens shell containing, or configured to contain, a lens fluid, wherein the lens is configured to isolate incident light from the plurality of heliostats into bands of reduced numerical aperture, and concentrate the light towards a corresponding plurality of focal regions at or near a back side of the lens, in use.

Preferably the lens shell comprises a plurality of integral back side lenses.

Preferably the plurality of integral back side lenses comprises a plurality of concave depressions in an interior surface of a back side of the lens shell.

Alternatively, the plurality of integral back side lenses comprises a plurality of convex protrusions from an interior surface of the back side of the lens shell.

Preferably the lens shell comprises a fluid inlet and a fluid outlet.

Preferably the lens comprises a substantially spherical lens.

Preferably the spherical lens comprises a substantially spherical dome and a cap which may be sealed together to define a cavity to contain the lens fluid.

Preferably the plurality of integral back side lenses are provided in the cap.

Alternatively, the lens may comprise a fisheye lens.

Preferably the lens has a diameter substantially equal to the size of an image reflected upon the lens by one of the plurality of heliostats, in use.

Preferably the lens shell is transparent or translucent across one or more of the ultraviolet, visible and infrared wavelength ranges.

Preferably the lens comprises the lens fluid.

Preferably the lens comprises the lens fluid, and the lens fluid has a refractive index of between 1.5 and 2.0.

Preferably the lens fluid comprises a molten salt selected from one or more of PbCl 2

, KCI, or NaCl.

Alternatively, the lens fluid may comprise an oil selected from a synthetic heat transfer fluid or a high refractive index immersion liquid.

Preferably the lens fluid is selected to absorb a predetermined part of a solar spectrum.

Preferably the lens fluid further comprises added particles with selected spectral absorption characteristics.

Preferably the lens comprises an antireflective and/or low emissivity coating.

In a third aspect, there is provided an omni-directional lens for use in a concentrating solar system, wherein the lens is substantially spherical.

In a fourth aspect, there is provided an omni-directional lens for use in a concentrating solar system, wherein the lens comprises a substantially rigid lens shell defining a plurality of substantially enclosed chambers, at least one of the plurality of enclosed chambers comprising a fluid-containing chamber containing, or configured to contain, a lens fluid.

Preferably the lens comprises a fisheye lens.

Preferably the fluid-containing chamber(s) comprise a fluid inlet and a fluid outlet.

Preferably the lens, in use, is configured to isolate incident light from a plurality of heliostats of the concentrating solar system into bands of reduced numerical aperture, and concentrate the light towards a corresponding plurality of focal regions at or near a back side of the lens.

Alternatively, the lens may be configured to be mounted to, and receive light from, a parabolic dish reflector.

Preferably the lens shell comprises a plurality of integral back side lenses.

Preferably the lens further comprises the lens fluid, and the lens fluid comprises a molten salt selected from one or more of PbCl 2, KC, or NaCl, or an oil selected from a synthetic heat transfer fluid or a high refractive index immersion liquid.

Preferably the lens comprises an antireflective and/or low emissivity coating

In a fifth aspect, there is provided a lens for use in a concentrating solar system, wherein the lens comprises a substantially spherical outer shell configured to contain a lens fluid, and the outer shell comprises a plurality of back side lenses.

In a sixth aspect, there is provided a fluid lens system for a solar concentration system, comprising: a substantially transparent rigid outer shell comprising an inlet and an outlet, the outer shell defining at least one chamber containing, or configured to contain, a translucent or substantially transparent lens fluid, the outer shell and the lens fluid together forming a lens for receiving and concentrating at least a portion of a spectrum of incident light; and a heat exchange system fluidly coupled with the inlet and the outlet, and configured to, in use, circulate the lens fluid and extract heat from the lens fluid.

Preferably the lens comprises an omni-directional lens configured to isolate incident light from a plurality of heliostats of the solar concentration system into bands of reduced numerical aperture, and concentrate the incident light towards a corresponding plurality of focal regions at or near a back side of the omni-directional lens for delivery to a furnace, in use.

Alternatively, the lens may be configured to be mounted to, and receive light from, a parabolic dish reflector

Preferably the fluid lens system further comprises the lens fluid.

Preferably the lens fluid comprises a molten salt selected from one or more of PbCl 2 ,

KC, or NaCl, or an oil selected from a synthetic heat transfer fluid or a high refractive index immersion liquid.

Preferably the lens fluid is selected to absorb a predetermined part of the solar spectrum.

Preferably the lens shell is substantially transparent across one or more of the ultraviolet, visible and infrared wavelength ranges.

Preferably the heat exchange system comprises a heat exchanger and a pump fluidly coupled with the inlet and the outlet by fluid transfer lines.

Preferably the heat exchange system further comprises a hot fluid storage tank and a cold fluid storage tank fluidly coupled with the heat exchanger.

Preferably the fluid transfer lines comprise trace heaters.

In a seventh aspect, there is provided a solar receiver for use in a concentrating solar system, the receiver comprising: an omni-directional lens configured to receive and concentrate reflected light; a plurality of beam combiners arranged to receive concentrated light from the lens; and a plurality of optic fibre bundles, each comprising one or more optic fibres, each of the optic fibre bundles configured to receive and redirect the concentrated light from one of the plurality of beam combiners.

Preferably the omni-directional lens comprises a substantially rigid shell containing, or configured to contain, a lens fluid, and the lens is configured to isolate incident light from a plurality of heliostats of the solar concentration system into bands of reduced numerical aperture, and concentrate the light towards a corresponding plurality of focal regions at or near a back side of the lens, in use.

Preferably the plurality of beam combiners are mounted to the lens at or substantially adjacent a respective one of the plurality of focal regions.

Preferably the omni-directional lens comprises a plurality of integral back side lenses and each of the plurality of beam combiners are mounted to the lens adjacent a respective one of the plurality of back side lenses.

Preferably a proximal end of each of the plurality of optic fibre bundles is fused to a respective one of the plurality of beam combiners.

Preferably the plurality of beam combiners each have a substantially hexagonal cross section.

In an eighth aspect, there is provided a solar receiver for use in a concentrating solar system, the receiver comprising: a static omni-directional lens; a plurality of beam combiners optically coupled with the lens; and a plurality of optic fibre bundles, each comprising one or more optic fibres, each of the optic fibre bundles optically coupled with one of the plurality of beam combiners, wherein the receiver, when elevated above a surround field of heliostats of the concentrating solar system in use, is configured to provide a substantially linear optical axis from each heliostat, through the lens, to one of the plurality of beam combiners, and the plurality of optic fibre bundles may be arranged to direct at least a portion of light incident on the lens to a furnace.

Preferably the lens comprises a substantially rigid shell containing, or configured to contain, a lens fluid, and the lens is configured to isolate incident light from a plurality of heliostats of the solar concentration system into bands of reduced numerical aperture, and concentrate the light towards a corresponding plurality of focal regions at or near a back side of the lens, in use.

Preferably the solar receiver further comprises a heat extraction system to circulate the lens fluid and extract heat therefrom.

Preferably the lens comprises a plurality of integral back side lenses and each of the plurality of beam combiners are mounted to the lens adjacent a respective one of the plurality of backside lenses.

In a ninth aspect, there is provided a solar receiver for use in a concentrating solar system comprising a plurality of heliostats, the receiver comprising: an omni-directional lens configured to, in use, receive incident light from the plurality of heliostats and focus it towards a corresponding plurality of focal regions; a plurality of beam combiners arranged about a portion of the lens at or substantially adjacent the plurality of focal regions so as to, in use, receive the incident light from the plurality of heliostats via the lens; and a plurality of optic fibre bundles, each comprising one or more optic fibres, each of the optic fibre bundles optically coupled with one of the plurality of beam combiners, wherein, in use, the lens, the plurality of beam combiners, and the plurality of optic fibre bundles form a plurality of parallel optical systems with the plurality of heliostats.

Preferably the omni-directional lens comprises a fluid lens containing, or configured to contain, a lens fluid, and the solar receiver further comprises a heat exchange system configured to circulate the lens fluid and extract heat therefrom.

In a tenth aspect, there is a provided a concentrating solar receiver comprising the lens of any one of the second to fifth aspects or the fluid lens system of the sixth aspect, a plurality of beam combiners optically coupled with the lens, and a plurality of optic fibre bundles optically coupled with the plurality of beam combiners.

In an eleventh aspect, there is provided a concentrating solar system comprising a plurality of heliostats, the lens of any one of the second to fifth aspects or the fluid lens system of the sixth aspect optically coupled with the plurality of heliostats, a plurality of beam combiners optically coupled with the lens, a plurality of optic fibre bundles optically coupled with the plurality of beam combiners, and a furnace for receiving and applying concentrated radiation from the plurality of optic fibre bundles.

In a twelfth aspect, there is provided a concentrating solar system comprising a plurality of heliostats and the concentrating solar receiver of any one of the seventh to tenth aspects.

In a thirteenth aspect, there is provided a solar concentration system comprising a parabolic dish reflector, an omni-directional lens mounted at or substantially adjacent a focus of the parabolic dish reflector, a plurality of beam combiners arranged to receive concentrated light from the parabolic dish reflector via the omni-directional lens, and a respective plurality of optic fibre bundles each optically coupled with one of the plurality of beam combiners to receive the concentrated light therefrom and guide it towards a target.

Preferably the omni-directional lens comprises a fluid lens with an inlet and an outlet, and the solar concentration system comprises a heat exchange system fluidly coupled with the inlet and the outlet to circulate a lens fluid and extract heat therefrom, in use.

Further aspects will become apparent from the following description.

5 Brief Description of the Drawings

A number of embodiments will now be described by way of example with reference to the drawings in which: Fig. 1 is a diagram of a first embodiment of a concentrating solar system. Fig. 2 is a schematic diagram of a spherical fluid lens according to a first embodiment; Fig. 3 is a further diagram of a spherical fluid lens according to the first embodiment; Figs. 4A, 4B and 4C are diagrams of a spherical dome and two alternative caps of the lens according to the first embodiment; Fig. 5 is a diagram of a receiver comprising a lens according to a second embodiment, and a heat exchange system according to a first embodiment; and Fig. 6 is diagram of a receiver comprising the lens according to the first embodiment, and a heat exchange system according to a second embodiment. Fig. 7 is a diagrammatic representation of spectral splitting in a spherical lens according to the first lens embodiment.

6 Detailed Description of the Drawings

6.1 Surround field embodiment

Referring first to Fig. 1, there is shown a diagrammatic representation of a concentrating solar system 1 according to a first embodiment. In broad terms, the system 1 generally comprises a plurality of concentrating heliostats 2, a lens 3, beam combiners 4, optic fibre bundles 5, furnace 6, and support tower 7. The combination of the lens 3, beam combiners 4, and optic fibre bundles 5 are collectively referred to herein as the receiver. The system further comprises a heat exchange system 8 (not shown in Fig. 1).

In use, the heliostats 2 actively track the movement of the sun throughout the day, reflecting light to the lens 3 which is statically mounted in an elevated position on the support tower 7. The lens 3 focuses that radiation towards the beam combiners 4, which transfer the concentrated light to the optic fibre bundles 5, from where the radiation can be directed to a furnace 6 for generation of steam and/or electricity, or use in other thermal processes.

Details of each of these main components of the system 1 are set out further below.

6.1.1 Heliostat Non-imaging optics and target-aligned tracking mechanisms may be used for improved solar concentration ratios. A preferred form of heliostat 2 is a concentrating heliostat, which concentrates reflected light and thereby reduces the required dimensions of the receiver.

An example of a suitable concentrating heliostat is the toroidal heliostat disclosed in International Patent Publication No. WO 2012/139169 assigned to Heliosystems Pty Ltd, the content of which is incorporated herein in its entirety, or the toroidal heliostats available from Heliosystems Pty Ltd of New South Wales, Australia under the PATHTM brand. Such heliostats are capable of optimising the power delivery profile or shape of the reflected image throughout the day by passively adjusting the apparent sagittal and/or tangential focal lengths of the heliostat's reflector. However, other forms of heliostat such as spherical or planar heliostats may alternatively be used in the system 1.

For reasons which will become apparent from the following description, the heliostats 2 may be arrayed in a surround field about the receiver. That is, the receiver of system 1, when elevated above a field of heliostats 2 arrayed generally at ground level, is capable of receiving and concentrating reflected light from substantially 360° about the tower 7 (when viewed from above).

6.1.2 Lens The lens 3 is preferably an omni-directional concentrating fluid lens.

The term "omni-directional" as used herein refers to the directional symmetry of the lens, whereby light is focussed in a similar manner (entrance aperture, effective focal length, spot size and/or aberrations) regardless of its direction of arrival at the lens surface. While the path of light through the lens will be different for each directional mode, the omni-directional lens is able to form a similar degree of focus, regardless of the direction of arrival of light (within a predetermined envelope). The term "omni directional" is not intended to require complete geometric symmetry, nor does it necessarily require light to be incident from all directions. The omni-directional lens 3 is thus a wide-angle lens with a relatively high acceptance angle. By contrast, a uni directional lens is optimised to focus light from a single direction (or band of directions about an axis), and has substantially different optical properties when light is incident from other angles.

The omni-directional lens 3 receives and focuses light received within a specific envelope of directions that describe the heliostat field, as seen from the perspective of the receiver. That is, the lens 3 when elevated above ground level is capable of receiving convergent light reflected generally upwardly towards the lens 3 from a surround field of heliostats (i.e. arrayed generally at ground level substantially 360 about the lens 3 when viewed from above), and focussing it towards one or more of the provided beam combiners.

The omni-directional concentrating lens 3 converges light to a focal region (a focal point, focal plane or focal surface) which may be chosen to occur inside or outside of the lens bulk as required by the application. The omni-directional lens may be non imaging (i.e., there is no requirement to form an image of the impinging light), and its geometry is preferably optimised such that a maximal concentration of light is achieved in the focal region.

As will become apparent from the following description, the omni-directional lens 3 permits the directional modes of light arriving from the heliostat field to be isolated into bands of reduced numerical aperture, and separately directed to specific optic fibre bundles 5. In other words, the lens 3 independently focusses incident light from the heliostats 2 towards a plurality of different areas on or near the back side of the lens 3. The different areas may be spatially distinct or overlapping, as described in further detail below.

The omni-directional lens 3 need not be completely symmetrical, nor manufactured from the same materials throughout. It need not be manufactured from a single lens element and could incorporate multiple lens elements to achieve the net effect of concentration of heliostat light as will be described in further detail with respect to other example embodiments, below.

6.1.2.1 Spherical fluid lens In a first embodiment, omni-directionality may be achieved by way of a substantially spherical lens 300, also known as a ball lens, as shown schematically by way of example in Fig. 2.

Because the lens 300 is substantially spherical, the optical axis from any one of the heliostats 2, through the lens 300, to a respective beam combiner 4 is substantially linear. The use of an array of heliostats 2, as well as an array of associated beam combiners 4 creates a set of parallel optical systems that all utilise the same fluid lens 300. This permits the receiver to be implemented in a surround heliostat field configuration, whereby heliostats covering a wide land area surrounding the tower 7 may all concentrate sunlight to the same central receiver point. The omni-directional lens thereby maximises the potential heliostat collection area relative to the surface area of the receiver itself, providing higher concentration ratios at lower cost.

The lens 300 preferably comprises a substantially spherical lens shell 301 containing a lens fluid 302. The lens shell 301 may have a plurality of integral back side lenses 303 formed on an inside surface of the back side of the lens 300 to refocus light into a beam combiner 4. Each of the back side lenses 303 corresponds to one of a plurality of beam combiners 4, which in turn collimate the light to accommodate the low numerical aperture of the optic fibre bundles 5.

The lens shell 301 is preferably made, at least in part, from a rigid, durable, and substantially transparent material such as glass, fused silica, quartz, or a synthetically prepared variant of quartz such as that available under the brand name VycorMT from Corning, Inc. of Corning, NY. The refractive index of such materials is generally around 1.5. A lens shell material having a lower refractive index than the lens fluid will give the receiver a type of 'anti-reflection' property. However, selection of the material for a particular design of lens shell 301 will be based primarily on the desired properties of: i) High transparency across visible and infrared wavelengths; ii) Structural strength and ability to safely contain the lens fluid; and iii) High resistance to thermal shock (crack resistance).

The diameter of the spherical lens shell 301 depends on both thermal and optical optimisation of the system, but is preferably similar to the size of an image of light arriving from a single concentrating heliostat.

The outer surface of the lens 301 may be further treated with antireflection coatings to maximise the amount of light captured from the heliostat field. Thermal losses due to radiation from the hot lens may be reduced with low emissivity coatings that reduce radiative emission in the far infrared spectrum.

The lens fluid 302 in this first embodiment of the lens is preferably substantially transparent to the solar spectrum, but in other embodiments (as described in further detail below) may have a translucency selected so as to absorb a proportion of the solar spectrum as heat as illustrated diagrammatically in Fig. 3. In some embodiments, around 80% of total energy incident on the lens may be absorbed as heat in the lens fluid.

The lens fluid 302 is preferably selected to provide an optimal refractive index that maximises the throughput of energy into the optic fibre bundles 5. The refractive index of the lens fluid 302 will preferably be higher than that of the lens shell 301. Suitable fluids for the lens fluid 302 may include, without limitation, molten salts such as PbCl 2, KC, NaCl, or mixtures thereof. In one embodiment, for example, the lens fluid 302 may comprise a mixture of 27 Mole % KCI in PbCl 2, providing a refractive index between 1.89 and 1.84 in the visible wavelengths across the temperature range of 445°C to 635°C. Adjustments to the refractive index are possible by varying the composition of the salt mixture.

Alternatively, the lens fluid 302 may comprise oils such as synthetic heat transfer fluids commonly used in concentrating solar collectors, or immersion liquids such as those based on antimony tribromide salt dissolved in diiodomethane.

Selection of an appropriate lens fluid 302 will be based primarily on the desired properties of: i) sufficiently high refractive index to focus light to the back of the lens 300; and ii) sufficient translucency or transparency to transmit a desired proportion of light to the back side of the lens 300.

The selection of lens fluid material, lens shell material, and fluid temperature must be considered in combination and optimised to meet the optical requirements of the receiver.

Figure 2 shows a simplified schematic cross-section of the omni-directional spherical lens 300, and an approximation of the rays 304 of light from a single distant heliostat 2. As illustrated, the lens shell 301 and lens fluid 302 are designed such that light striking the front side (in use, a lower spherical dome portion) of the spherical lens 300 is refracted towards the principal optical axis and concentrated at or near the rear of the spherical lens 300.

The relatively high refractive index of the lens fluid 302 concentrates the substantially parallel beams of light striking the front side of the lens at or near the back side of the lens 300. Preferably, the system is designed so that the maximum amount of light striking the backside of the lens is transmitted via the beam combiners into the optic fibre bundles.

The higher refractive index of the lens fluid 302, relative to the lens shell 301, results in a rudimentary gradient index lens configuration which improves the concentration of the light, as well as reducing front-surface reflection losses. The refractive index of fluids generally reduces with increasing temperature, so a temperature gradient increasing toward the outer surface of the lens 300 (i.e. hotter lens fluid 302 near the lens shell 301) will enhance this effect.

After the light rays 304 pass through the lens fluid 302, their direction is preferably corrected with the aid of a small integral back side lens 303 formed on the inside surface of the back side of the lens shell 301, to refocus and maximise the light directed into the beam combiner 4. A single back side lens 303 is preferably provided for each beam combiner 4. In the illustrated embodiments, the back side lens 303 is formed as a small concave depression or "dimple" on the inside surface of the lens shell 301. Alternatively, the back side lens 303 may be a convex protrusion from the interior surface of the lens shell 301, projecting into the cavity of the lens shell 301. This may require use of a higher refractive index fluid for optimum performance. In yet other embodiments, the back side lenses 303 may be omitted at the expense of reduced efficiency.

The precise specifications of the lens 300, including the optimum refractive index of the lens fluid 302, diameter and thickness of the lens shell 301, and shape of the back side lens 303 are dependent on a number of factors including the size of the incident heliostat images, the wavelength and temperature dependence of the refractive index of the lens fluid 302, the incident spectrum and the desired spectrum striking the optic fibre bundles 5 (less absorption in the lens 300), the operating temperature of the lens 300 and lens fluid 302, optical properties of the material of the lens shell 301, and physical dimensions and numerical aperture of the beam combiner 4 and optic fibre bundles 5.

The spherical lens 300 of the first embodiment further comprises a fluid inlet 305 and a fluid outlet 306, which are shown in Figs. 2 and 3.

By means of the fluid inlet 305 and fluid outlet 306, the lens fluid 302 can be circulated by way of convection and/or a pump. This permits temperature regulation of the lens fluid, heat extraction from the fluid and/or thermal energy storage, drainage of the cavity defined by the lens shell 301, and improved distribution of heat within the lens shell 301. Drainage of the cavity may be desired for maintenance purposes, or to avoid fluid 'freeze' in the event of extended periods without sufficient solar heating. Improved heat distribution may be desired to minimise localised boiling and hot spots of the lens fluid 302 within the lens shell 301.

Hot lens fluid 302 may be extracted from the fluid outlet 306, stored and/or cooled by a heat exchange system, and recirculated into the lens shell 301 through the fluid inlet 305, as described in further detail below.

Figure 2 also schematically illustrates the "mapping" between a number of heliostats 2 and a number of beam combiners 4, and the substantially linear optical axis from each heliostat 2, through the spherical lens 3, to the respective beam combiner 4.

The lens shell 301 may be manufactured in multiple parts to facilitate ease of production, assembly, testing, and maintenance.

Figures 4A and 4B illustrate, by way of example, the construction of a spherical lens shell 301 according to the first embodiment. The lens shell 301 is preferably constructed from two pieces: a substantially spherical dome 307 which forms the majority of the sphere, as shown in Fig. 4A; and a cap 310 which forms the remainder of the sphere, as shown in Fig. 4B.

Referring to Fig. 4A, the spherical dome 307 forms the front side of the lens 300 which is oriented towards the heliostats 2 in use (i.e. forming the lower portion of the lens 300 when mounted in the support tower 7). The spherical dome 307 may alternatively be described as a truncated sphere or cauldron-like shape, in that it is a hollow partial sphere providing a circular interface 308. The spherical dome 307 in this embodiment is rotationally symmetric.

The spherical dome 307 in this embodiment comprises an 18 mm thick shell, with an outer diameter of 800 mm, although in other embodiments these dimensions may vary dependent on the design of the overall system. For example, and without limitation, the diameter may be within the range of 600 to 1,000 mm, preferably 700 to 900 mm, and more preferably 750 to 850 mm. About the circular interface 308 is provided an outwardly-extending flange 309.

Referring to Fig. 4B, the cap 310 is a complementary shape to the spherical dome 307, such that the dome 307 and cap 310 together form a substantial sphere. The cap 310 similarly has an outwardly-extending flange 311 for mounting to flange 309 of the spherical dome 307.

In use, the cap 310 forms the back side of the lens 300 which is oriented away from the heliostats 2 (i.e. forming an upper portion of the lens 300 when mounted in the support tower 7).

As shown in Fig. 4B, the cap 310 preferably comprises the integral back side lenses 303 formed on an internal surface thereof. The cap 310 is further provided with the plurality of beam combiners 4 which extend radially from the outer surface thereof adjacent a respective back side lens 303. The arrangement of back side lenses 303 and beam combiners 4 in this embodiment are such that individual heliostats 2 in the solar field are mapped to individual beam combiners 4 in a one-to-one configuration, as described in further detail below.

In an alternative embodiment of the cap as shown in Fig 4C, the array of back side lenses 303 and beam combiners 4 are provided in a higher density, and the space between the backside lenses 303 is minimised for improved light capture. Contributing to this is the hexagonal shape of the back side lenses 303 which allows adjacent back side lenses to abut each other in a honeycomb-like pattern with little, if any, wasted space therebetween, and the hexagonal cross-section of the beam combiners 4. In this embodiment, heliostats 2 mapped to the beam combiners 4 in a one-to-many or many-to-many configuration, as described in further detail below, so that light from individual heliostats 2 is distributed over a number of beam combiners 4, and extracted via the optic fibre bundles 5.

Referring to the embodiments of both Figs. 4B and 4C, the cap 310 is further provided with the fluid inlet 305 and the fluid outlet 306.

The cap 310 may be manufactured from an alternative material, such as a metal, that readily incorporates the beam combiners 4, fluid inlet 305, and fluid outlet 306. Any light which does not enter the beam combiners 4 is preferably reflected by the cap 310 back into the lens fluid 302 where it can be absorbed as heat.

The spherical dome 307 and cap 310 are preferably sealed together into one unit using a gasket or sealant suitable for the chosen lens fluid 302 at the interface between the respective flanges 309, 311. The entire lens shell 301 may be mounted via fixtures to the support tower for correct positioning and restraint, and filled with a suitable lens fluid 302.

The fluid inlet 305 and fluid outlet 306 are configured to promote laminar flow of hot lens fluid 302 inside the lens shell 301, for effective recirculation and minimisation of the chance of localised boiling and hot spots, without unduly affecting the optics. For example, inertia of the fluid exiting the fluid inlet 305 may be used to establish a recirculation mode within the lens 300.

The fluid inlet 305 is preferably configured such that it is possible to extract the majority of the fluid from the lens 300, leaving the cavity substantially empty. In one embodiment, as shown in Fig. 4B for example, this may be achieved by manipulation of the fluid conduit within the lens, by rotation or twist, to bring the conduit near to the bottom of the lens. When the lens is in use, however, the conduit it positioned so as to avoid or minimise any impact upon the optics. In the illustrated embodiment, the fluid inlet 305 comprises an elongate conduit extending into the lens shell 301. The elongate conduit comprises a substantially arcuate proximal portion 305a with a shape and diameter which substantially matches that of the inside surface of the cap 310, and a distal portion 305b configured to extend into the spherical dome 307. Distal portion 305b may also be substantially arcuate, and may extend in a direction substantially perpendicular to a plane in which the proximal portion 305a lies. The arcuate proximal portion 305a may extend from a first point at which the conduit of the fluid inlet 305 passes through the cap 310, and through an arc of approximately 1800 to a second position on an opposing side of the cap 310. The conduit of the fluid inlet 305 may pass through an aperture in the cap 310, and be rotatable within the aperture to permit manipulation of the distal portion 305b.

The fluid inlet 305 and fluid outlet 306 are coupled to fluid transfer lines (not shown) which are preferably provided with trace heaters to avoid fluid 'freeze.' The system 1 may further be provided with a thermal burner and heating cycle in addition to the solar receiver such that the lens fluid 302 may be independently heated in the case of low insolation.

6.1.2.2 Non-spherical lens In other embodiments, the omni-directional lens may comprise a non-spherical lens which otherwise may be similar in construction to the spherical lens described above. The non-spherical lens will be more challenging to optimise, but may have advantages in correcting for temperature gradients in the lens fluid, or compensating for a less than-ideal lens fluid refractive index with an elongation around the beam combiners.

6.1.2.3 Multi-chamber lens In yet other embodiments, an omni-directional lens may contain two or more separate chambers and/or lens fluids. This has particular advantages for lower refractive index fluids. It may also be advantageous for higher power systems where the optical path depth through the lens fluid must be reduced in order to moderate the optical attenuation within the lens, and increase the light intensity arriving at the optic fibre bundles.

A second example embodiment of an omni-directional lens 3 is illustrated in Fig. 5, in which the lens comprises a fisheye lens 320. The fisheye lens 320 preferably comprises a rigid, transparent lens shell 321 defining a number of chambers which may be filled with a lens fluid or remain empty. In this example embodiment, the lens comprises first chamber 322 and a second chamber 323. The first chamber 322 contains a lens fluid, while the second chamber 323 remains empty. As in the first embodiment, light arriving from the heliostat field is focussed onto back side lenses, beam combiners, and guided in optic fibre bundles 5 to a furnace 6.

Although the fisheye lens 320 does not have the linear optical axis of the spherical lens, it similarly isolates incident light from a plurality of heliostats into bands of reduced numerical aperture, and focusses it towards a plurality of focal points at or near a back side of the lens 320.

A range of similar designs are possible including the provision for materially different lens fluids placed in the various receiver chambers in order to enhance the focus and/or spectrum of light delivered to the optic fibre bundles 5. Recirculation of lens fluid may be utilised for extraction of heat and maintenance of lens fluid temperatures as required.

Figure 5 also illustrates the optional heat exchange system 8, described in further detail below.

6.1.2.4 Multiple lens elements In yet other embodiments, the omnidirectional lens may comprise a plurality of lens elements achieving the net effect of concentrating incident light from a plurality of heliostats onto optic fibre apertures.

6.1.3 Beam combiners Each beam combiner 4, alternatively known as a truncated cone concentrator, hyperbolic concentrator, total internal reflection taper, or dielectric taper, is attached to the outside of the lens 3.

In the case of spherical lens 300, for example, each of the plurality of beam combiners 4 extends radially from an outer surface of the back side of the lens shell 301, adjacent to a respective one of the plurality of back side lenses 303. The beam combiners 4 may have a polygonal, in particular a hexagonal, cross-section for higher packing density (compared to a circular conical beam combiner, for example), and better matching to hexagonal core optic fibre bundles.

Each beam combiner 4 may use non-imaging optics to further concentrate light received from the lens 3 while accommodating the low numerical aperture of the optic fibre bundles 5. They may be designed for total-internal-reflection optics using a transparent material such as that used in the optic fibre core, or alternatively the material of the lens shell.

The heliostats 2 may be "mapped" (i.e. optically coupled, via the lens) to the beam combiners 4 in one (or more) of a number of different configurations, namely:

• One-to-one, in which each heliostat 2 is mapped to a single beam combiner 4, and each beam combiner 4 is mapped to a single heliostat 2. • One-to-many, in which each heliostat 2 is mapped to two or more beam combiners 4, and each beam combiner 4 is mapped to a single heliostat 2. * Many-to-one, in which each heliostat 2 is mapped to a single beam combiner 4, and each beam combiner 4 is mapped to two or more heliostats 2. • Many-to-many, in which each heliostat 2 is mapped to two or more beam combiners 4, and each beam combiner 4 is mapped to two or more heliostats 2.

Using a larger number of beam combiners 4 better captures off-axis/skew rays, at the cost of a more expensive receiver. A one-to-one or one-to-many configuration may be preferred in smaller scale systems, while a many-to-one or many-to-many configuration may be more favourable for larger systems. It will be appreciated that the ratio of the number of heliostats 2 to beam combiners 4 may vary depending upon the design and configuration of the overall system.

Light that doesn't enter a beam combiner 4 can be optionally either absorbed into the lens shell 301 or reflected back into the lens fluid 302. That way most of it will be converted to heat in the lens fluid 302, which can be extracted and applied using a heat exchanger as described in further detail below.

6.1.4 Optic fibre bundles The optic fibre bundles 5 are mounted onto the termination of the beam combiners 4 in order to accept concentrated sunlight therefrom. Each optic fibre bundle 5 may consist of one or more optic fibres, each promoting transmission of light via total internal reflection. Fibres may be solid core, or hollow core, may be fused or separate, and may be clad or unclad. Fibres need not be of circular cross section. For example, bundles of close-packed hexagonal fibres in unclad form offer high numerical aperture, efficient transmission of highly concentrated broadband radiation, and flexibility. The core of each optic fibre in the optic fibre bundles 5 may be fused with the material of the beam combiner 4 in order to minimise interface reflection losses and the resulting thermal load.

Each optically-coupled heliostat group, combiner, and optic fibre bundle may be considered as substantially separate "parallel" optical systems sharing a common lens. Due to the omni-directional nature of the lens 3, the system 1 meets the requirement that the numerical aperture for each separate parallel optical system should be small, without constraining the shape of the heliostat field.

The optic fibre bundles 5 may be then collected together and routed towards a nearby furnace where the concentrated light is applied for work. The use of optic fibre bundles 5 to direct the concentrated light provides considerable geometric flexibility in the overall design of the system 1, avoiding the limitations of secondary reflectors. The geometric flexibility of the optic fibre bundles 5 permit the "parallel" optical systems to be combined. The distal ends of the bundle of optic fibres 5 may be arranged to further concentrate the light at the furnace by aligning the optic fibre bundles 5 radially with the furnace, potentially eliminating the need for further complex optics.

6.1.5 Furnace The furnace 6 is the target for the concentrated light and applies it for work. The term "furnace" is accordingly intended to encompass any apparatus capable of applying concentrated light for work. This may include at least a boiler, high concentration photovoltaic cells, thermophotovoltaic system, thermochemical reaction chamber, gas turbine, or heat exchanger.

The furnace 6 may be mounted, in part or in whole, on the support tower 7. Alternatively, the optic fibre bundles 5 provide the geometric flexibility to route the light elsewhere, such as to a nearby furnace adjacent the tower or the system, or to a nearby factory designed or converted to apply concentrated light.

Preferably the furnace also utilises secondary heat extracted from a lens fluid heat exchange system in order to increase yields or improve efficiency, as described in further detail below.

6.1.6 Support tower The support tower serves to elevate the receiver above the field of heliostats so that it can receive reflected light from each of the heliostats throughout the day, ideally with no (or at least minimal) obstruction from adjacent heliostats or the support tower itself.

One advantage of the omni-directional lens described above is that it is suitable for use with a surround field of heliostats, whereby the support tower is provided substantially centrally within the field of heliostats. However, the tower may alternatively be provided off-centre, or entirely to one side of the heliostats. This may be due to local site constraints, heliostat field optimisation outputs, to enable eventual scaling of the installation to a surround field, for example, or due to use of an alternative directional receiver, for example.

A further advantage of the omni-directional lens described above, when used in combination with heliostats, is that it may be mounted statically in the tower. That is, the heliostats track the movement of the sun so that there is no need for the lens to be moveably mounted.

The furnace may optionally also be mounted in the tower, substantially adjacent the receiver to reduce the length of the optic fibres and resulting losses. Alternatively, the use of optic fibres enables the concentrated light to be redirected to a nearby furnace outside the field of heliostats. This may be particularly advantageous in the case of a system built to supply an existing facility converted to run on concentrated light.

6.1.7 Heat exchange system Figures 5 and 6 illustrate embodiments of the heat exchange system 8 for extracting heat from the fluid lens 3. The heat exchange system 8 comprises fluid transfer lines 801 fluidly coupling the fluid inlet 305 and fluid outlet 306 of the lens with a heat exchanger 802 and a recirculation pump 803.

In the embodiment of Fig. 5, the heat exchange system 8 may serve either or both of two purposes. Firstly, it minimises the chance of localised boiling and hotspots within the lens shell 321 by pumping out the hot lens fluid, extracting heat within the heat exchanger 802, and recirculating the cooled fluid back to the lens. Secondly, thermal energy extracted from the lens fluid 322 by the heat exchanger 802 may be used in secondary processes. For example, thermal energy extracted from the lens fluid 322 may be applied to generate electricity which may be distributed into an electricity grid network, or to pre-heat or pre-cool (via an absorption chiller) materials used in the furnace.

The second embodiment of a heat exchange system 8 as shown in Fig. 6 is largely identical to that of Fig. 5, aside from the addition of a thermally insulated hot fluid storage tank 804, cold fluid storage tank 805 and a second pump 803. Lens fluid 302 may be drawn from a 'Cold' storage tank, circulated through the lens and returned to a 'Hot' storage tank. The energy may be extracted with the use of heat exchangers between the fluid storage tanks, and used for a range of processes such as steam generation, electricity production and other thermal processes. Thermal energy stored in lens fluid 302 may be extracted and applied during hours of low insolation, extending the hours of operation of the system, or during times of peak demand. The heat exchanger 8 in this embodiment may also serve the further purpose of allowing the lens 3 to be easily emptied of lens fluid 302 for maintenance, and providing for thermal energy storage.

The lens fluid 302 serves the dual purpose of refraction and concentration of sunlight, as well as removal of heat.

6.1.7.1 Spectral splitting A further development of the heat extraction concept is spectral splitting as illustrated in Fig. 7, whereby translucent lens fluid 302 is selected such that it selectively absorbs a portion of the solar spectrum as heat to be extracted by the heat exchange system 8, while other parts of the spectrum are transmitted to the furnace as concentrated light. This may be achieved by selection of an appropriate lens fluid, and/or by addition of additives or particles (such as engineered nanoparticles with specific spectral absorption) to the lens fluid, to modify the transmission/absorption properties of the lens 3 and tune which wavelengths 312 of sunlight are converted to heat within the lens, and which wavelengths 313 pass through to the beam combiners 4.

Preferably, the lens fluid 302 is tuned to preferentially absorb predetermined parts of the solar spectrum. For example, the lens fluid may absorb those wavelengths which are least effectively transported by the beam combiner 4 or optic fibre bundles 5, or wavelengths that are otherwise not required by the process powered by the system 1.

The lens fluid 302 is thermally isolated from the furnace, so each system may be independently optimised for maximal efficiency. For example, in the case where the sunlight is directed onto high concentration photovoltaic cells, then the photovoltaic cell temperature is not limited by the lens fluid temperature as in conventional photovoltaic thermal (PV-T) systems.

An advantage of the static fluid lenses described above, particularly when spectral splitting is used, is that heliostats facing the lens from different directions will direct their light along substantially different paths through the lens, distributing the energy throughout the lens fluid 302.

6.2 Parabolic dish embodiment

In an alternative embodiment of a solar concentration system, the system may comprise a single parabolic dish reflector with an omni-directional lens provided at its focal point. The system is otherwise similar to the solar concentration system described above. In particular, the omni-directional lens may comprise a spherical fluid lens, non-spherical lens, multi-chamber lens, or multiple lens elements. A plurality of beam combiners receive concentrated light from the parabolic dish via the lens, and direct it into a respective plurality of optic fibre bundles which may be used to channel the concentrated light towards a furnace.

Use of the omni-directional lens with a parabolic dish may permit the aperture of the dish to be extended beyond the standard limitations.

In the preferred embodiment, the lens comprises a fluid lens with an inlet, an outlet, and a heat exchange system. The lens fluid may be selected to absorb a portion of the solar spectrum to allow for spectral splitting as described above.

Although various solar concentration systems have been described above by way of example and with reference to possible embodiments thereof, it is to be understood that modifications or improvements may be made thereto without departing from the scope of the invention. The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

Furthermore, where reference has been made to specific components or integers of the invention having known equivalents, then such equivalents are herein incorporated as if individually set forth.

From the foregoing it will be seen that a concentrating solar lens, receiver, and system are provided which are suitable for use with a high power solar furnace. In various embodiments, one or more of the following advantages may be provided. The lens may be mounted statically in a surround field of heliostats, avoiding the need for movably mounting the lens to track the sun. The system may be readily scaled up by increasing the size of the heliostat field, increasing the primary collector area with relatively little (if any) change to the receiver required. The omni-directional lens and beam combiners overcome the low numerical aperture of the optic fibres, and reduce the number of optic fibres required. The furnace reactor vessel design is not overly constrained by the design of the solar collector optics. Energy is delivered in the form of concentrated radiation emitted from the optical fibre tips. This can enable high temperatures processes unattainable through conductive or convective heating methods. High temperature reactions can be heated in free space inside a concentrated radiation beam without the need for high temperature crucibles. Concentrated radiation can be used for heating a wide range of materials in solid, liquid or gas phase, including insulating materials and reactions sensitive to electrical currents or voltages. Use of optic fibres as a light guide provides flexibility in the design of the system, without the need for large and costly secondary reflectors. The solar energy may be delivered into a vacuum chamber via the optical fibres, enabling thermochemical processes under vacuum. Additional optical concentration may be achieved by focussing bundles of optical fibres together onto a single location, eliminating the need for complex optics while enhancing concentration ratios. The light may be directed to a furnace mounted in the support tower, or to a nearby facility outside the heliostat field. Spectral splitting may be used for secondary energy generation processes, and thermal isolation from the furnace permits each system to be optimised independently.

Unless the context clearly requires otherwise, throughout the description, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense that is to say, in the sense of "including, but not limited to," as opposed to an exclusive or exhaustive sense.

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

Claims

7 Claims

What we claim is: 1. A solar concentration system comprising: a plurality of heliostats; a support tower extending upwardly above the plurality of heliostats; an omni-directional lens mounted to the tower to receive and focus light reflected from the plurality of heliostats; a plurality of beam combiners mounted to the lens and configured to receive light from the lens; and a plurality of optic fibre bundles each comprising at least one optic fibre, each optic fibre bundle being coupled with one of the plurality of beam combiners and configured to receive the light therefrom and direct it towards a furnace.
2. The solar concentration system according to claim 1, wherein the plurality of heliostats each comprise a concentrating heliostat.
3. The solar concentration system according to claim 2, wherein the lens is configured to isolate the light received from the plurality of heliostats into bands of reduced numerical aperture.
4. The solar concentration system according to any one of claims 1-3, wherein the lens comprises a substantially spherical lens.
5. The solar concentration system according to any one of claims 1-3, wherein the lens comprises a fisheye lens.
6. The solar concentration system according to any one of claims 1-5, wherein a diameter of the lens is approximately equal to the size of an image reflected upon the lens by one of the plurality of heliostats.
7. The solar concentration system according to any one of claims 1-6, wherein the lens comprises a fluid lens.
8. The solar concentration system according to claim 7, wherein the lens comprises a substantially rigid outer lens shell containing a lens fluid.
9. The solar concentration system according to claim 8, wherein the lens shell is transparent or translucent across one or more of the ultraviolet, visible and infrared wavelength ranges.
10. The solar concentration system according to any one of claims 8-10, wherein the lens shell comprises an antireflective and/or low emissivity coating.
11. The solar concentration system according to any one of claims 8-11, wherein the lens fluid has a refractive index selected so that the lens concentrates substantially all of the light received from each of the plurality of heliostats into one or more of the plurality of beam-combiners.
12. The solar concentration system according to any one of claims 8-12, wherein the lens fluid has a refractive index higher than that of a material of the lens shell.
13. The solar concentration system according to any one of claims 8-12, wherein the lens fluid has a refractive index of between 1.5 and 2.0.
14. The solar concentration system according to claim 14, wherein the lens fluid has a refractive index of between 1.82 and 1.95.
15. The solar concentration system according to any one of claims 8-15, wherein the lens fluid comprises a molten salt.
16. The solar concentration system according to claim 16, wherein the lens fluid comprises one or more of PbCl 2, KCI, or NaCl.
17. The solar concentration system according to any one of claims 8-14, wherein the lens fluid comprises an oil.
18. The solar concentration system according to claim 17, wherein the lens fluid comprises a synthetic heat transfer fluid or a high refractive index immersion liquid.
19. The solar concentration system according to any one of claims 8-18, wherein the lens shell comprises glass, fused silica, quartz, or a synthetically prepared variant of quartz.
20. The solar concentration system according to any one of claims 8-19, wherein the material of the lens shell has a refractive index between that of air and the lens fluid.
21. The solar concentration system according to any one of claims 7-20, wherein the lens comprises a plurality of integral back side lenses which each refocus incident light into one of the plurality of beam combiners.
22. The solar concentration system according to claim 21, wherein the plurality of back side lenses comprises a plurality of concave depressions in an interior surface of a back side of the lens.
23. The solar concentration system according to claim 21, wherein the plurality of back side lenses comprises a plurality of convex protrusions from an interior surface of the back side of the lens.
24. The solar concentration system according to any one of claims 7-23, wherein the lens comprises a fluid inlet and a fluid outlet.
25. The solar concentration system according to claim 24, wherein the system further comprises a heat exchanger coupled with the fluid inlet and fluid outlet by fluid transfer lines, for circulating the lens fluid and extracting heat therefrom.
26. The solar concentration system according to claim 25, wherein the system further comprises means for applying thermal energy extracted from the lens fluid by the heat exchanger.
27. The solar concentration system according to one of claims 25 or 26, wherein the fluid transfer lines comprise a trace heater.
28. The solar concentration system according to claim 8, or any one of claims 9-27 when directly or indirectly dependent from claim 8, wherein the lens fluid is selected to absorb a predetermined part of the spectrum.
29. The solar concentration system according to claim 28, wherein the lens fluid comprises added particles with selected spectral absorption characteristics.
30. The solar concentration system according to claim 29, wherein the particles are selected to absorb a predetermined portion of the spectrum of the light.
31. The solar concentration system according to claim 4, or any one of claims 6-30 when directly or indirectly dependent from claim 4, wherein the lens comprises a substantially spherical dome and a cap sealed together to define a cavity to contain the lens fluid.
32. The solar concentration system according to claim 31 when directly or indirectly dependent from any one of claims 21-23, wherein the plurality of back side lenses are provided in the cap.
33. The solar concentration system according to claim 31 or claim 32 when directly or indirectly dependent from any one of claims 24-27, wherein the fluid inlet and the fluid outlet are provided in or through the cap.
34. The solar concentration system according to any one of claims 31-33, wherein the plurality of beam combiners are mounted to the cap.
35. The solar concentration system according to any one of claims 1 to 34, wherein each of the plurality of heliostats is mapped to a corresponding one of the plurality of beam combiners in a one-to-one configuration.
36. The solar concentration system according to any one of claims 1-34, wherein each of the plurality of heliostats is mapped to two or more of the plurality of beam combiners in a one-to-many configuration.
37. The solar concentration system according to any one of claims 1-34, wherein each of the plurality of heliostats is mapped to one of the plurality of beam combiners in a many-to-one configuration.
38. The solar concentration system according to any one of claims 1-34, wherein each of the plurality of heliostats is mapped to two or more of the plurality of beam combiners in a many-to-many configuration.
39. The solar concentration system according to claim 21, or any one of claims 22 38 when directly or indirectly dependent from claim 21, wherein each of the plurality of beam combiners are arranged adjacent to a respective one of the plurality of back side lenses so as to receive light therefrom.
40. The solar concentration system according any one of claims 1-39 wherein the plurality of beam combiners are arranged substantially radially about a portion ofthelens.
41. The solar concentration system according to any one of claims 1-40, wherein distal ends of the plurality of optic fibre bundles are arranged substantially radially with respect to the furnace to concentrate emitted light from the plurality of optic fibre bundles on the furnace.
42. The solar concentration system according to any one of claims 1-41, wherein each of the plurality of optic fibre bundles comprises a plurality of optic fibres.
43. The solar concentration system according to any one of claims 1-42, wherein a proximal end of each of the plurality of optic fibre bundles is fused to a respective one of the plurality of beam combiners.
44. The solar concentration system according to any one of claims 1-43, wherein the plurality of beam combiners each have a substantially hexagonal cross section.
45. The solar concentration system according to any one of claims 1-44, wherein the furnace comprises a boiler, high concentration photovoltaic cells, a thermophotovoltaic system, a thermochemical reaction chamber, a gas turbine, or a heat exchanger.
46. An omni-directional lens for use in a concentrating solar system comprising a plurality of heliostats, the lens comprising a substantially rigid outer lens shell containing, or configured to contain, a lens fluid, wherein the lens is configured to isolate incident light from the plurality of heliostats into bands of reduced numerical aperture, and concentrate the light towards a corresponding plurality of focal regions at or near a back side of the lens, in use.
47. The omni-directional lens according to claim 46, wherein the lens shell comprises a plurality of integral back side lenses.
48. The omni-directional lens according to claim 47, wherein the plurality of integral back side lenses comprises a plurality of concave depressions in an interior surface of a back side of the lens shell.
49. The omni-directional lens according to claim 47, wherein the plurality of integral back side lenses comprises a plurality of convex protrusions from an interior surface of the back side of the lens shell.
50. The omni-directional lens according to any one of claims 46 to 49, wherein the lens shell comprises a fluid inlet and a fluid outlet.
51. The omni-directional lens according to any one of claims 46-50, wherein the lens comprises a substantially spherical lens.
52. The omni-directional lens according to claim 51, wherein the spherical lens comprises a substantially spherical dome and a cap which may be sealed together to define a cavity to contain the lens fluid.
53. The omni-directional lens according to claim 52, when directly or indirectly dependent from claim 47, wherein the plurality of integral back side lenses are provided in the cap.
54. The omni-directional lens according to any one of claims 46-50, wherein the lens comprises a fisheye lens.
55. The omni-directional lens according to any one of claims 46-54, wherein the lens has a diameter substantially equal to the size of an image reflected upon the lens by one of the plurality of heliostats, in use.
56. The omni-directional lens according to any one of claims 46-54, wherein the lens shell is transparent or translucent across one or more of the ultraviolet, visible and infrared wavelength ranges.
57. The omni-directional lens according to any one of claims 46-56, further comprising the lens fluid.
58. The omni-directional lens according to claim 57, wherein the lens comprises the lens fluid, and the lens fluid has a refractive index of between 1.5 and 2.0.
59. The omni-directional lens according to claim 57 or claim 58, wherein the lens fluid comprises a molten salt selected from one or more of PbCl 2, KC, or NaCl.
60. The omni-directional lens according to claim 57 or claim 58, wherein the lens fluid comprises an oil selected from a synthetic heat transfer fluid or a high refractive index immersion liquid.
61. The omni-directional lens according to any one of claims 57-60, wherein the lens fluid is selected to absorb a predetermined part of a solar spectrum.
62. The omni-directional lens according to any one of claims 57-61, wherein the lens fluid further comprises added particles with selected spectral absorption characteristics.
63. The omni-directional lens according to any one of claims 46-62, wherein the lens comprises an antireflective and/or low emissivity coating.
64. An omni-directional lens for use in a concentrating solar system, wherein the lens comprises a substantially rigid lens shell defining a plurality of substantially enclosed chambers, at least one of the plurality of enclosed chambers comprising a fluid-containing chamber containing, or configured to contain, a lens fluid.
65. The omni-directional lens according to claim 64, wherein the lens comprises a fisheye lens.
66. The omni-directional lens according to claim 64 or claim 65, wherein the fluid containing chamber(s) comprise a fluid inlet and a fluid outlet.
67. The omni-directional lens according to any one of claims 64-66, wherein the lens, in use, is configured to isolate incident light from a plurality of heliostats of the concentrating solar system into bands of reduced numerical aperture, and concentrate the light towards a corresponding plurality of focal regions at or near a back side of the lens.
68. The omni-directional lens according to any one of claim 64-66, wherein the lens is configured to be mounted to, and receive light from, a parabolic dish reflector.
69. The omni-directional lens according to any one of claims 64-68, wherein the lens shell comprises a plurality of integral back side lenses.
70. The omni-directional lens according to any one of claims 64-69, wherein the lens shell is transparent or translucent across one or more of the ultraviolet, visible and infrared wavelength ranges.
71. The omni-directional lens according to any one of claims 64-70, wherein the lens further comprises the lens fluid, and the lens fluid comprises a molten salt selected from one or more of PbCl 2, KC, or NaCl, or an oil selected from a synthetic heat transfer fluid or a high refractive index immersion liquid.
72. The omni-directional lens according to claim 71, wherein the lens fluid is selected to absorb a predetermined part of a solar spectrum.
73. The omni-directional lens according to claim 71 or claim 72, wherein the lens fluid further comprises added particles with selected spectral absorption characteristics.
74. The omni-directional lens according to any one of claims 64-73, wherein the lens comprises an antireflective and/or low emissivity coating.
75. A fluid lens system for a solar concentration system, comprising: a translucent or transparent rigid outer shell comprising an inlet and an outlet, the outer shell defining at least one chamber containing, or configured to contain, a translucent or transparent lens fluid, the outer shell and the lens fluid together forming a lens for receiving and concentrating at least a portion of a spectrum of incident light; and a heat exchange system fluidly coupled with the inlet and the outlet, and configured to, in use, circulate the lens fluid and extract heat from the lens fluid.
76. The fluid lens system according to claim 75, wherein the lens comprises an omni-directional lens configured to isolate incident light from a plurality of heliostats of the solar concentration system into bands of reduced numerical aperture, and concentrate the incident light towards a corresponding plurality of focal regions at or near a back side of the omni-directional lens for delivery to a furnace, in use.
77. The fluid lens system according to claim 75, wherein the lens is configured to be mounted to, and receive light from, a parabolic dish reflector.
78. The fluid lens system according to any one of claims 75-77, further comprising the lens fluid.
79. The fluid lens system according to claim 78, wherein the lens fluid comprises a molten salt selected from one or more of PbCl 2, KCI, or NaCl, or an oil selected from a synthetic heat transfer fluid or a high refractive index immersion liquid.
80. The fluid lens system according to claim 78 or claim 79, wherein the lens fluid is selected to absorb a predetermined part of a solar spectrum.
81. The fluid lens system according to any one of claims 78-80, wherein the lens fluid further comprises added particles with selected spectral absorption characteristics.
82. The fluid lens system according to any one of claims 75-81, wherein the lens shell is substantially transparent across one or more of the ultraviolet, visible and infrared wavelength ranges.
83. The fluid lens system according to any one of claims 75-82, wherein the heat exchange system comprises a heat exchanger and a pump fluidly coupled with the inlet and the outlet by fluid transfer lines.
84. The fluid lens system according to claim 83, wherein the heat exchange system further comprises a hot fluid storage tank and a cold fluid storage tank fluidly coupled with the heat exchanger.
85. The fluid lens system according to claim 83 or claim 84, wherein the fluid transfer lines comprise trace heaters.
86. A solar receiver for use in a solar concentration system, the receiver comprising: an omni-directional lens configured to receive and concentrate reflected light; a plurality of beam combiners arranged to receive concentrated light from the lens; and a plurality of optic fibre bundles each comprising one or more optic fibres, each of the optic fibre bundles configured to receive and redirect the concentrated light from one of the plurality of beam combiners.
87. The solar receiver according to claim 86, wherein the omni-directional lens comprises a substantially rigid shell containing, or configured to contain, a lens fluid.
88. The solar receiver according to claim 86 or claim 87, wherein the lens is configured to isolate incident light from a plurality of heliostats of the solar concentration system into bands of reduced numerical aperture, and concentrate the light towards a corresponding plurality of focal regions at or near a back side of the lens, in use.
89.The solar receiver according to claim 88, wherein the plurality of beam combiners are mounted to the lens at or substantially adjacent a respective one of the plurality of focal regions.
90. The solar receiver according to claim 86 or claim 87, wherein the omni directional lens is mounted to, or configured for mounting to, a parabolic dish reflector.
91. The solar receiver according to any one of claims 86 to 90, wherein the omni directional lens comprises a plurality of integral back side lenses and each of the plurality of beam combiners are mounted to the lens adjacent a respective one of the plurality of back side lenses.
92. The solar receiver according to any one of claims 86 to 91, wherein a proximal end of each of the plurality of optic fibre bundles is fused to a respective one of the plurality of beam combiners.
93. The solar receiver according to any one of claims 86 to 92, wherein the plurality of beam combiners each have a substantially hexagonal cross-section.
94. A solar receiver for use in a concentrating solar system, the receiver comprising: an omni-directional lens; a plurality of beam combiners optically coupled with the lens; and a plurality of optic fibre bundles each comprising one or more optic fibres, each of the optic fibre bundles optically coupled with one of the plurality of beam combiners, wherein the receiver, when elevated above a surround field of heliostats of the concentrating solar system in use, is configured to provide a substantially linear optical axis from each heliostat, through the lens, to one or more of the plurality of beam combiners, and the plurality of optic fibre bundles may be arranged, in use, to direct at least a portion of light incident on the lens to a furnace.
95. The solar receiver of claim 94, wherein the lens comprises a substantially rigid shell containing, or configured to contain, a lens fluid, and the lens is configured to isolate incident light from a plurality of heliostats of the solar concentration system into bands of reduced numerical aperture, and concentrate the light towards a corresponding plurality of focal regions at or near a back side of the lens, in use.
96. The solar receiver according to claim 95, further comprising a heat extraction system to circulate the lens fluid and extract heat therefrom.
97. The solar receiver according to claim 95 or claim 96, wherein the plurality of beam combiners are mounted to the lens at or substantially adjacent a respective one of the plurality of focal regions.
98. The solar receiver according to any one of claims 94 to 97, wherein the lens comprises a plurality of integral back side lenses and each of the plurality of beam combiners are mounted to the lens adjacent a respective one of the plurality of backside lenses.
99. A solar receiver for use in a concentrating solar system comprising a plurality of heliostats, the receiver comprising: an omni-directional lens configured to, in use, receive incident light from the plurality of heliostats and focus it towards a corresponding plurality of focal regions; a plurality of beam combiners arranged about a portion of the lens at or substantially adjacent the plurality of focal regions so as to, in use, receive the incident light from the plurality of heliostats via the lens; and a plurality of optic fibre bundles each comprising one or more optic fibres, each of the optic fibre bundles optically coupled with a respective one of the plurality of beam combiners, wherein, in use, the lens, the plurality of beam combiners, and the plurality of optic fibre bundles form a plurality of parallel optical systems with the plurality of heliostats.
100. The solar receiver according to claim 99, wherein the omni-directional lens comprises a fluid lens containing, or configured to contain, a lens fluid, the solar receiver further comprises a heat exchange system configured to circulate the lens fluid and extract heat therefrom.
101. A concentrating solar receiver comprising the lens of any one of claims 46-74 or the fluid lens system of any one of claims 75-85, a plurality of beam combiners optically coupled with the lens, and a plurality of optic fibre bundles optically coupled with the plurality of beam combiners.
102. A concentrating solar system comprising at least one concentrating reflector, the lens of any one of claims 46-74 or the fluid lens system of any one of claims 75-85 optically coupled with the at least one concentrating reflector, a plurality of beam combiners each optically coupled with one or more of the at least one concentrating reflector via the lens, a plurality of optic fibre bundles optically coupled with the plurality of beam combiners, and a furnace for receiving and applying concentrated solar radiation from the plurality of optic fibre bundles.
103. A solar concentration system comprising a plurality of heliostats and the solar receiver of any one of claims 86-101 to receive reflected light from the plurality of heliostats.
104. A solar concentration system comprising a parabolic dish reflector, an omni-directional lens mounted at or substantially adjacent a focus of the parabolic dish reflector, a plurality of beam combiners arranged to receive concentrated light from the parabolic dish reflector via the omni-directional lens, and a respective plurality of optic fibre bundles each optically coupled with one of the plurality of beam combiners to receive the concentrated light therefrom and guide it towards a target.
105. The solar concentration system of claim 104, wherein the omni directional lens comprises a fluid lens with an inlet and an outlet, and the solar concentration system comprises a heat exchange system fluidly coupled with the fluid lens to circulate a lens fluid and extract heat therefrom.