SOLAR RADIATION GUIDANCE DEVICE

Abstract

Solar radiation guidance device (1), particularly for a solar reactor system (100), comprising the following components: a solar concentrator (13), for collecting and concentrating electromagnetic radiation, a solar deflection device (10) comprising a funnel (2) with a funnel wall (2a) that comprises a specular reflective surface (2b) on an inside of the funnel (2) for reflecting solar and/or thermal radiation, wherein said funnel (2) further comprises an inlet aperture (3) and an exit aperture (4), wherein the inlet aperture (3) is comprised in an inlet plane (3a) and the exit aperture (4) is comprised in an exit plane (4a), and wherein said funnel (2) is arranged such that it collects the concentrated electromagnetic radiation from the solar concentrator (13), wherein the solar deflection device (10) is mounted to allow rotation around a rotation axis (A) perpendicular to the inlet plane (3a) of the inlet aperture (3) between at least two positions, such that for each position of the at least two positions of the solar deflection device (10) the collected electromagnetic radiation from the solar concentrator (13) is redirectable through the funnel (2) along a corresponding direction.

Claims

1. Solar radiation guidance device (1), particularly for a solar reactor system (100), comprising the following components: a solar concentrator (13), for collecting and concentrating electromagnetic radiation, particularly solar and/or thermal radiation, a solar deflection device (10) comprising a funnel (2) with a funnel wall (2a) that comprises a reflective surface (2b) on an inside of the funnel (2) for reflecting said radiation, wherein said funnel (2) further comprises an inlet aperture (3) and an exit aperture (4), wherein the inlet aperture (3) is comprised in an inlet plane (3a) and the exit aperture (4) is comprised in an exit plane (4a), and wherein said funnel (2) is arranged such that it collects the concentrated radiation from the solar concentrator (13), characterized in that the solar deflection device (10) is mounted to allow rotation around a rotation axis (A) perpendicular to the inlet plane (3a) of the inlet aperture (3) between at least two positions, such that for each position of the at least two positions of the solar deflection device (10) the collected radiation from the solar concentrator (13) is redirectable through the funnel (2) along a corresponding direction.

2. Solar radiation guidance device according to claim 1, wherein the solar deflection device (10) is further characterized by an essentially curved line (5) that extends from a center (3c) of the inlet aperture (3) to a center (4c) of the exit aperture (4), wherein for each plane (6a) that intersects said curved line (5) perpendicularly, the reflective surface (2b) of the funnel wall (2a) has a cross-section (6) along said plane (6a), wherein said cross-section (6) encloses an area and is centered around the curved line (5), wherein particularly said curved line (5) is essentially an arc line, particularly essentially a circular arc line or particularly essentially a non-parabolic line. a deflection angle (7) that is enclosed between said plane (6a) and the inlet plane (3a).

3. Solar radiation guidance device according to claim 1, wherein the area enclosed by the inlet aperture (3), the exit aperture (4) and/or the cross-section (6) has an oval, particularly a circular shape or elliptical shape.

4. Solar radiation guidance device according to claim 1, wherein the area of the inlet aperture (3) is larger than the area of the exit aperture (4).

5. Solar radiation guidance device according to claim 1, wherein the enclosed area of the cross-section (6), particularly the diameter (6d) of the cross-section (6), is a continuous function of said deflection angle (7) and wherein said function is a monotonic function, particularly a strictly monotonic function.

6. Solar radiation guidance device according to claim 1, wherein the function comprises a spline, particularly a linear, a quadratic or a cubic, particularly a natural cubic spline or wherein the function is a piecewise particularly natural cubic spline connecting a plurality of interpolation points, wherein particularly the size of the enclosed area of the inlet aperture (3), particularly the diameter (3d) of the inlet aperture (3), and the size of the enclosed area of the exit aperture, particularly the diameter (4d) of the exit aperture (4) are two of the plurality of interpolation points and wherein particularly a third interpolation point corresponds to the size of enclosed area of the cross-section (6), particularly to the diameter (6d) of the cross-section (6).

7. Solar radiation guidance device according to claim 1, wherein the inlet aperture (3) and the exit aperture (4) enclose a deflection angle (7) of 45.

8. Solar reactor system (100) comprising a solar radiation guidance device (1) according to claim 1, wherein the solar reactor system (100) further comprises at least two chambers (11, 12) that are associated to the at least two positions of the solar radiation guidance device (1), wherein each chamber (11, 12) comprises an inlet opening for receiving electromagnetic, particularly solar and/or thermal radiation and wherein each chamber (11, 12) is arranged such that by rotation of the solar deflection device (10) about the rotation axis, the exit aperture (4) of the solar deflection device (10) is alignable with the inlet opening of each chamber (11, 12) such that the collected radiation is directable through the inlet opening of each chamber (11, 12).

9. Method for deflecting electromagnetic radiation, particularly solar and/or thermal radiation with a solar radiation guidance device (1) according to claim 1, comprising the steps of: providing radiation, particularly solar and/or thermal radiation to the solar concentrator (13), such that the solar concentrator (13) collects at least a fraction of the radiation, providing the collected radiation to the inlet aperture (3) of the funnel (2) of the solar deflection device (10), rotating the solar deflection device (10) alternately to the at least two positions, such that for each position the collected radiation is redirected along said corresponding direction.

10. Method according to claim 9, wherein for each position of the solar deflection device (10) the collected radiation is redirected in a corresponding chamber (11, 12) of at least two chambers (11, 12).

11. Method according to claim 10, wherein by providing radiation by rotating the solar deflection device (10) alternatingly between the at least two positions, a thermochemical reaction, particularly a reversible thermochemical reaction, is driven, such that an endothermic transformation is taking place in the corresponding chamber (12) to which the radiation is redirected, and that an exothermic transformation is taking place in at least one of the other chambers (11) of the at least two chambers (11, 12).

12. Method according to claim 10, wherein by providing radiation by rotating the solar deflection device (10) alternatingly between the at least two positions, a thermal energy charging-discharging process is driven, such that heating or melting of material is taking place in the corresponding chamber (12) to which the radiation is redirected, and that cooling or solidification of material is taking place in at least one of the other chambers (11) of the at least two chambers (11, 12).

13. Method according to claim 11, wherein a first compound and a second compound are provided for the thermochemical reaction, particularly reversible thermochemical reaction, within the at least two chambers (11, 12), wherein the first compound is reduced to the second compound, particularly thermally reduced, when the particularly solar and/or thermal radiation is redirected in the corresponding chamber (12) and/or wherein the second compound is oxidized to the first compound, particularly thermally oxidized, when the radiation is redirected in another chamber (11) of the at least two the chambers (11, 12).

14. Method according to claim 13, wherein the first compound comprises at least one of: a metal oxide, a metal-based oxide, a doped-oxide and/or a perovskite-type oxide.

15. Method according to claim 13, wherein a third compound is provided with the second compound and wherein said third compound is reduced when the second compound is oxidized, wherein said third compound is particularly water and/or carbon dioxide.

16. Method for deflecting electromagnetic radiation, particularly solar and/or thermal radiation with a solar reactor system (100) according to claim 8, comprising the steps of: providing radiation, particularly solar and/or thermal radiation to the solar concentrator (13), such that the solar concentrator (13) collects at least a fraction of the radiation, providing the collected radiation to the inlet aperture (3) of the funnel (2) of the solar deflection device (10), rotating the solar deflection device (10) alternately to the at least two positions, such that for each position the collected radiation is redirected along said corresponding direction.

17. Method according to claim 16, wherein for each position of the solar deflection device (10) the collected radiation is redirected in a corresponding chamber (11, 12) of the at least two chambers (11, 12).

18. Method according to claim 17, wherein by providing radiation by rotating the solar deflection device (10) alternatingly between the at least two positions, a thermochemical reaction, particularly a reversible thermochemical reaction, is driven, such that an endothermic transformation is taking place in the corresponding chamber (12) to which the radiation is redirected, and that an exothermic transformation is taking place in at least one of the other chambers (11) of the at least two chambers (11, 12).

19. Method according to claim 17, wherein by providing radiation by rotating the solar deflection device (10) alternatingly between the at least two positions, a thermal energy charging-discharging process is driven, such that heating or melting of material is taking place in the corresponding chamber (12) to which the radiation is redirected, and that cooling or solidification of material is taking place in at least one of the other chambers (11) of the at least two chambers (11, 12).

20. Method according to claim 18, wherein a first compound and a second compound are provided for the thermochemical reaction, particularly reversible thermochemical reaction, within the at least two chambers (11, 12), wherein the first compound is reduced to the second compound, particularly thermally reduced, when the particularly solar and/or thermal radiation is redirected in the corresponding chamber (12) and/or wherein the second compound is oxidized to the first compound, particularly thermally oxidized, when the radiation is redirected in another chamber (11) of the at least two the chambers (11, 12).

Description

[0074] Further features and advantages of the invention shall be described by means of a detailed description of embodiments with reference to the figures. It is shown in:

[0075] FIG. 1 a schematic view of a device according to the invention;

[0076] FIG. 2 a schematic three-dimensional view of a device according to the invention;

[0077] FIG. 3 a schematic view of a solar reactor system according to the invention;

[0078] FIG. 4 a schematic view of a solar reactor system according to the invention; and

[0079] FIG. 5 a diagram of the chamber temperature versus time.

[0080] In FIG. 1 and FIG. 2 a solar deflection device 10 is shown schematically that is arranged at a focal plane F of a solar concentrator 13 and rotatably arranged along the optical axis A of said solar concentrator 13 (FIG. 1). The solar deflection device 10 comprises an inlet aperture 3 and an exit aperture 4, wherein the diameter 3d of the inlet aperture 3 is larger than the diameter 4d of the exit aperture 4. The center 4c of the exit aperture 4 is laterally shifted with respect to the center 3c of the inlet aperture 3. This shift is called the eccentricity e.sub.c. The solar deflection device comprises a funnel 2 with a funnel wall 2a, that has a reflective inside 2b for reflecting incident radiation. The plane 3a that comprises the inlet aperture 3 and the plane 4a that comprises the exit aperture 4 enclose an angle 8.

[0081] The solar deflection device 10 is rotatably mounted and can be rotated around the optical axis A and adopt a first and a second position.

[0082] In FIG. 1 two chambers 11, 12 are shown that are arranged such that when the solar deflection device 10 is rotated to the first position, incident radiation is reflected such by the reflective surface 2b of the funnel 2 that it is redirected in the first chamber 11 and that when the solar deflection device 10 is rotated to the second position, incident radiation is reflected by the reflective surface 2b of the funnel 2 such that it is redirected in the second chamber 12.

[0083] In FIG. 2 a cross-section 6 through the reflective surface 2b of the funnel 2 is shown. The cross-section 6 is comprised in a plane 6a, that encloses a deflection angle 7 with the inlet plane 3a. The funnel 2, more particularly the reflective surface 2b of the funnel 2 extends along a curved line 5 that extends from the center 3c of the inlet aperture 3 to the center 4c of the exit aperture 4. The cross-section 6, particularly for any deflection angle 7 that lies between zero degree and the angle 8 between the inlet and exit plane 3a, 4a, is intersected perpendicularly from said curved line 5; that means, that the tangent n at the point of intersection of the curved line with the cross-section 6 is orthogonal to the plane 6a. The cross-section 6 is particularly circular with a diameter 6d that is particularly larger than the diameter 4d of the exit aperture 4 and smaller than the diameter 3d of the inlet aperture 3.

[0084] The curved line 5 furthermore intersects in the center 6c of the cross-section 6. In FIG. 2 the curved line 5 is a circular arc line with a radius R.sub.c.

[0085] In FIGS. 3 and 4 two views of a solar reactor system 100 are shown. The solar reactor system 100 comprises a first 11 and a second 12 chamber and the funnel 2 of the solar guidance device 1 is shown, wherein the solar guidance device 1 comprises the solar deflection device 10. A solar concentrator 13 is arranged such that it guides collected solar radiation to the inlet aperture 3 of the funnel 2 under a half acceptance angle 9. The funnel is arranged at the focal plane F of the solar concentrator 13. The funnel is mounted rotatably in the solar reactor system 100, such that it can adopt a first and a second position. The rotation might be facilitated by a motor 14 (FIG. 4). When the funnel 2 adopts the first position, incident solar radiation from the solar concentrator 13 is guided along a corresponding direction in the first chamber 11. When the funnel 2 adopts the second position, incident solar radiation from the solar concentrator 13 is guided along another corresponding direction in the second chamber 12.

[0086] By rotating the funnel 2 alternately between the first and the second position, energy provided by the solar radiation is delivered to the corresponding chamber 11, 12. This energy can be used to drive a chemical or a physical process.

[0087] FIG. 5 shows a diagram of the course of the temperature inside the first 11 and second 12 chamber, when the solar reactor system 100 is driven according to the invention. The temperature profile 111 corresponds to the temperature inside the first chamber 11 and the temperature profile 112 corresponds to the temperature inside the second chamber 12. Furthermore the temperature profiles 211, 212 measured on the shell of the first and second chamber 11, 12 are shown. It can be seen that particularly a time interval for the cycling of the funnel 2 is advantageous that extends until the temperature profile 111, 112 is flattening with time, i.e. the temperature increase 21 at the end of the interval is less than particularly 10% of the initial temperature increase 20. In this embodiment a temporal interval of several minutes, for example 18 minutes is preferred.

EXAMPLE

[0088] A Tailored Toroid Concentrator (TTC) is used as a solar deflection device 10 for a solar guidance device 1.

[0089] Such a TTC concentrates and redirects radiation and might be used for directing concentrated radiation particularly from a single stationary source particularly to a plurality of apertures of a multiple-cavity receiver, for example an array of cavities, each with an individual aperture.

[0090] The TTC is a tailored concentrator based on a torus with geometry modified to achieve ideal concentration at maximum optical efficiency. The TTC particularly comprises all or some of the following features: [0091] radiation is collected by a circular inlet aperture 3 of radius r.sub.i, within a nominal half acceptance angle 9 (in formulas also referred to as ), and redirected to a particularly circular exit aperture 4 with a radius r.sub.o or with a diameter 4d that is smaller than the radius r.sub.i or diameter 3d of the inlet aperture 3 respectively, [0092] the exit aperture 4 is tilted by a rotation angle of , wherein said rotation angle corresponds to the largest deflection angle 7, and wherein the exit aperture 4 is furthermore laterally displaced by an eccentricity e.sub.c, with respect to the inlet aperture 3, [0093] the eccentricity e.sub.c and rotation angle may be chosen to achieve the required separation and inclination of the plurality of cavity apertures, [0094] the geometric concentration C=A.sub.i/A.sub.o equals the theoretical limit of 1/sin.sup.2() imposed by the three-dimensional conservation of tendue, [0095] the TTC features low average number of reflections, thus minimizing power loses due to finite reflectivity of mirror surfaces, [0096] the optical efficiency through the TTC may approach that of conventional non-imaging concentrators which only concentrate and do not redirect radiation, [0097] the geometry of the TTC is defined by a curved line 5 that is particularly a circular arc centerline in the two-dimensional cross-section through the plane of symmetry of the TTC, [0098] the geometric concentration C can be reduced from the theoretical limit by slightly increasing the exit aperture diameter 4d, leading to an increase in optical efficiency, [0099] the three dimensional geometry is formed by a series of circular cross-sections 6 cut at a deflection angle 7 (in formulas also referred to as ) with respect to the inlet aperture 3, [0100] the normal of each circular cross-section 6 is tangent to the centerline 5 at the point of intersection, [0101] the diameter 6d or radius (r()) of each circular cross-section 6 is defined by a function S, particularly a taper function S, with r=S(), where S is particularly an interpolant of linear, quadratic, or cubic form, [0102] the mirror profiles may be tailored by changing the taper function S to maximize optical efficiency, [0103] the inner R.sub.i and outer radii R.sub.o of the solar deflection device 10 are chosen to meet the required eccentricity e.sub.c and rotation angle 8 (also referred to as ).

Example of an Embodiment of a TTC

[0104] The construction of such a tailored toroidal concentrator particularly begins in the x-z plane with a curved line 5, particularly a circular arc centerline covering a rotation angle and radius R.sub.c centered at the origin as shown in FIG. 2. The inlet aperture 3 extends along the inlet plane 3a along the x-y-axis. The circular inlet aperture 4 with a radius r.sub.i that is smaller than the radius of the circular arc centerline R.sub.c, is centered at the start of said curved line 5 (defining a deflection angle of =0), laying in the x-y plane. The center-to-center eccentricity e.sub.c of the TTC is given by e.sub.c=R.sub.c(1cos()). Each deflection angle 7 in the range between 0 defines a cross-section 6 that is comprised in a plane 6a that intersects the inlet plane 3a enclosing said deflection angle 7 and that is perpendicular to said curved line 5 at the point of intersection with the curved line 5. The circular exit aperture 4 with a radius r.sub.o that is smaller than the radius of the inlet aperture r.sub.i, r.sub.o<r.sub.i, <r.sub.c, is centered at the end =) of the curved line 5 through a plane whose normal is tangent to the end of the curved line 5. The exit aperture radius r.sub.o is nominally chosen as r.sub.i=r.sub.o sin(), corresponding to the theoretical limit of geometric concentration C for partially collimated incident radiation of the nominal half acceptance angle . Selecting a slightly larger exit aperture radius r.sub.o may be beneficial in improving optical efficiency, with a slight reduction from the theoretical maximum geometric concentration C.

[0105] The reflective surface 2b of the TTC is defined by a series of circular cross-sections 6 from the inlet to exit aperture 3 on planes 6a whose normals n are tangent to the curved line 5 at the intersection point where the respective plane 6a intersects the curved line: The taper of the solar deflection device 10 is the function S describing the radius r of each circular cross section 6 as a function of the deflection angle 7 (also referred to as ). The complete parametric equations of the surface in three dimensions, for an origin placed at the center of the curved line 5, with x-z as the symmetry plane of the TTC, are:

r=S()

x=(r cos()+R.sub.c) cos()

y=(r cos()+R.sub.c) sin()

z=r sin()

for 0, and 0<2. The resulting shape is a surface ranging from the circular inlet aperture 3 to the circular exit aperture 4 through the circular cross-sections 6 of radius r=S().

[0106] Various taper functions S are possible, but generally interpolating functions are used. Depending on the number of interpolation points (also termed knots) used in addition to the endpoints (=0, r.sub.i) and (=, r.sub.o), different interpolation functions (also termed interpolants) may be used. The simplest interpolant is (with zero additional knots) the linear interpolant r()=r.sub.i(r.sub.ir.sub.o)/. An additional interpolation point may be defined at the waist of the device 10 at a deflection angle .sub.w (given a nominal value of ) and radius r.sub.w. It is then possible to define a piecewise linear spline, a parabola (quadratic), or piecewise cubic spline through the three knots. For .sub.w=, a value of r.sub.w=(r.sub.i+r.sub.o) produces a linear interpolant for a spline of any degree. The waist control point can be tailored to maximize the optical transfer efficiency of the TTC. Additional knots provide additional degrees of freedom to tailor the TTC.

[0107] Due to its high degree of smoothness, the cubic spline is a preferred interpolant for the taper function S. For one additional interpolation point at the waist, a natural cubic spline S() may be fitted through knots I(0, r.sub.i), W(.sub.w, r.sub.w) and O(.sub.o, r.sub.o). The 3-point spline has two segments: the first segment ranges from the inlet to the waist, and second segment ranges from the waist to the exit, with second derivatives set to zero at the two ends (natural spline), and first and second derivatives matched at W. The interpolant for the j.sup.th segment has the form:

S.sub.j()=a.sub.j+b.sub.jt.sub.j+c.sub.jt.sub.j.sup.2+d.sub.jt.sub.j.sup.3

where t.sub.j=t.sub.1=/.sub.w for the first segment, and t.sub.j=t.sub.2=(.sub.w)/(.sub.w) for the second segment. The coefficients of the interpolant are:

a.sub.2=r.sub.i

a.sub.2=r.sub.w

b.sub.1=0.25(5r.sub.i+6r.sub.wr.sub.o)

b.sub.2=0.5(r.sub.i+r.sub.o)

c.sub.1=0

c.sub.2=0.75(r.sub.i2r.sub.w+r.sub.o)

d.sub.1=0.25(r.sub.i2r.sub.w+r.sub.o)

d.sub.2=0.25(r.sub.i+2r.sub.wr.sub.o)

[0108] One way to design such a TTC is to choose the inlet (and/or exit) aperture for maximum concentration C=1/sin.sup.2(), and subsequently tailor the waist radius r.sub.w at half the rotation angle to yield the highest optical efficiency.

[0109] The particularly highest optical efficiency can be estimated for example by a computer simulation.

Geometry Specification

[0110] Three different geometric constructions with an increasing number of degrees-of-freedom were investigated. In all cases, the three dimensional geometry was obtained by lofting from the circular inlet aperture to the circular outlet aperture along the specified guide curves.

Baseline

[0111] The baseline design consists of a circular centerline 5 with a radius which governs the position of the inlet and outlet aperture 3, 4. The cross-section through the reflective surface is represented by two curved lines (i.e. the guide profiles), particularly circular arc lines. The design has no degrees of freedom to be used as optimization parameters.

Spline 1

[0112] The Spline 1 design utilizes the height and eccentricity e.sub.c to position the inlet and outlet apertures 3, 4. The two guide profilesthat are the cross-sectional lines of the funnel representing the funnel wallare natural cubic splines passing through the inlet and outlet aperture 3, 4 edges wherein the guide profile's shape is controlled by a knot placed between a beginning and an end of the guide line, particularly at the waist of the solar deflection device 1. There are three degrees of freedom which may be used as optimization parameters. The optimization parameters are particularly given by the radius from one of the guide profiles at a particular deflection angle, the radius of the funnel at a particular deflection angle and the height of the funnel.

Spline 2

[0113] The Spline 2 design is similar to the Spline 1 design, but the placement of the knots is not restricted to be collinear with the origin. The two guide profiles on the inside and outside of the deflection device may be chosen independently. There are five degrees of freedom which may be used as optimization parameters. The optimization parameters are particularly given by [0114] the radius of the line in the x-z plane from the origin to the interior knot of the inner guide profile, [0115] the same but for the outer guide profile, [0116] a first deflection angle of the line in the x-z plane from the origin to the interior knot of the inner guide profile, [0117] the same but for the outer guide profile , and [0118] the height of the solar deflection device.

[0119] Optimization was performed to maximize optical efficiency for a reflectivity of 95% at the nominal acceptance angle using 10.sup.5 rays. The alternate engine in LightTools was used with an exit criterion of less than a 10-5% improvement on the objective function. However, it is likely that the noise floor of the MC simulation provides a less strict exit criterion.