Solar receiver

Abstract

The invention relates to a rotor (1) for a solar receiver. The rotor comprises an inlet manifold (2) having an inlet, an outlet manifold (4) having an outlet, and a plurality of flow tubes (6). The inlet manifold (2) is spaced from the outlet manifold (4) along a first axis about which the rotor (1) can be rotated. The plurality of flow tubes (6) extend from the inlet manifold (2) to the outlet manifold (4) such that a fluid can flow from the inlet manifold (2) to the outlet manifold (4) through the flow tubes (6). At least one of the plurality of flow tubes (6) is a coiled flow tube and the, or each, coiled flow tube comprises an inlet tail (12) connected to the inlet manifold (2) and an outlet tail (14) connected to the outlet manifold (4).

Description

[0001] Solar Receiver

[0002] The present invention relates to devices for absorbing solar radiation and converting the absorbed solar radiation into thermal energy, the components of such devices, and methods for using the same. More particularly, the present invention relates to solar receivers and their rotors for use in the conversion of solar radiation to thermal energy in concentrated solar power applications.

[0003] Concentrated solar power applications may use a series of optical concentrators including mirrors and / or lenses to concentrate the sunlight incident on large surface areas onto a smaller area, for example from which the energy may be harnessed. In commercial applications, banks of optical concentrators may be positioned in proximity to a tower or mast supporting a solar receiver. The optical concentrators may be positioned such that they will reflect incident solar radiation towards a receiver on the tower which absorbs the energy. The optical concentrators may be fitted with a tracking system that allows them to adjust alignment relative to the position of the sun to ensure that the incident solar radiation continues to be directed towards the tower throughout the day. Power tower arrangements and parabolic trough / trench solar plants are known designs of concentrated solar power station.

[0004] Solar receivers may be designed to operate within specific ranges of solar radiation concentration factor. The solar radiation concentration factor, c, is defined as the thermal flux (W / m2) that is incident on surface of the receiver to be heated, divided by the corresponding thermal flux arriving at the system from the sun. This is sometimes known as the ‘insolation’. The concentration factor has a direct effect on the efficiency of the system and it is a sensible intent for a designer to try to maximise c. Existing concentrated solar power stations may operate at c values of around 20 to 100, with some Stirling dish designs achieving c values of up to 2000. Greater values of c represent increased energy density which in turn represents a greater potential energy resource that may be harnessed by the receiver. Increasing the c value of a concentrated solar system may induce higher temperatures in the receiver. The maximum value of c at which a receiver can operate is thus limited by the thermal tolerances of the receiver and its materials. For example, temperatures in excess of 1000°C may be achieved as the value of c increases. Structural components may also be put at risk by a high c value as structural steel may begin to melt at temperatures of around 1400°C. Receivers may also be at risk from the effects of thermal expansion and contraction upon components in situations where the energy incident upon the receiver is variable, or where the system cycles between active and inactive states. At high values of c, the energy flux may be very high and this can create large temperature gradients and extremely high temperatures within, and at the surface of, a solar receiver. Such high temperatures and temperature gradients could significantly limit the life of the receiving material. High c values may also introduce additional challenges such as diminishing absorption efficiency as c values increase, overheating of materials due to limitations upon the rate at which energy can be carried away from the absorbing surfaces of the system, and high thermal losses due to emissivity as the total energy of the system increases.

[0005] The present invention provides a rotor for a solar receiver, the rotor comprising: an inlet manifold having an inlet; an outlet manifold having an outlet; and a plurality of flow tubes; wherein the inlet manifold is spaced from the outlet manifold along a first axis about which the rotor is to be rotated, and the plurality of flow tubes extend from the inlet manifold to the outlet manifold such that a fluid can flow from the inlet manifold to the outlet manifold through the flow tubes; at least one of the plurality of flow tubes is a coiled flow tube and the, or each, coiled flow tube comprises an inlet tail connected to the inlet manifold and an outlet tail connected to the outlet manifold, the inlet tail and outlet tail are connected by at least one coil.

[0006] It has been found that the use of coiled flow tubes provides significant advantages for the construction and operation of rotors for solar receivers when compared with straight flow tubes. The surface area of each flow tube that can be exposed to solar radiation may be significantly greater than for a straight flow tube.

[0007] The number of coiled flow tubes needed to provide a pre-determined surface area onto which solar radiation can be directed may be lower than the number of straight flow tubes that would be required to provide an equivalent surface area. The reduction in the number of flow tubes required can simplify manufacturing as fewer connections need to be made during manufacture. A reduced number of flow tubes can also reduce the resistance to fluid flow between the inlet and outlet manifold which can make operation of the solar receiver more efficient.

[0008] A solar receiver may be part of a solar power station. The solar power station may direct solar radiation onto a part of the solar receiver, for example a heat absorber. The heat absorber may be static, but in this example the heat absorber is a rotor. A rotor is a heat absorber that rotates about an axis of rotation. If the rotor is not illuminated from all around the axis, different portions of the rotor can be exposed to solar radiation as the rotor rotates.

[0009] The inlet manifold can be any suitable shape and has an inlet to receive fluid from a source and distribute it to the flow tubes. The outlet manifold can be any suitable shape and is to receive fluid from the flow tubes and channel it to the outlet.

[0010] The inlet manifold and the outlet manifold are connected by a plurality of flow tubes and are spaced apart along the first axis. The inlet manifold and outlet manifold may be connected only by the plurality of flow tubes, or by additional components which may provide mechanical stability to the rotor. The manifold spacing may be any suitable value and will depend upon the size of the rotor, for example the spacing between the manifolds may be more than 0.5m, more than 0.75m or more than 1m. The spacing between the manifolds may be less the 5m, less than 3m, or less than 2m.

[0011] At least one of the plurality of flow tubes is a coiled flow tube. The coiled flow tube comprises three parts:

[0012] • an inlet tail connected to the inlet manifold;

[0013] • an outlet tail connected to the outlet manifold; and

[0014] • at least one coil.

[0015] The at least one coil is arranged between the inlet tail and the outlet tail and the inlet tail and outlet tail may be any suitable shape to couple the at least one coil to the inlet or outlet manifold. A coil is a loop of flow tube that extends around, and radially offset from an axis, for example a loop axis, which may be the coil axis, a loop may extend over 300° around the axis, or completely, 360°, around the axis. The radial offset from the axis may be substantially constant. The loop may extend along the axis as well as around the axis so that ends of the loop are offset along the axis. There may be a plurality of coils connecting the inlet tail and outlet tail. The plurality of coils of a coiled flow tube may all extend about the same axis, for example a coil axis. The plurality of coils may all extend around the axis in the same direction, or there may be a combination of directions. Having all the plurality of coils extend around the axis in the same direction makes the coils easier to manufacture. The plurality of coils of a coiled flow tube may differ in size or shape, or may all be substantially the same size and shape. If the coiled flow tube comprises a plurality of coils, the plurality of coils may form a helix extending around a coil axis. Each coil of a coiled flow tube may have same pitch, or angle, relative to a coil axis. Each coil may have the same diameter. Each coil may have the same radius of curvature.

[0016] The coiled flow tube may for formed from a tube having a substantially uniform circular cross section. The coiled flow tube may be formed by bending a straight tube around a mandrel, similar to forming a coil spring. This way of manufacturing a coiled flow tube can be caried out by a large number of manufacturing companies and thus the management of the supply chain might be simplified and the cost of manufacturing the rotor might be reduced. The outside diameters of the tube from which the coiled flow tube is formed could be between 10mm to 100mm. The wall thickness of the tube may be between 5-7% of the tube outside diameter. The diameter of the coil may be between 7 to 10 times the tube outside diameter. The coiled flow tubes may be made from a metal, for example a stainless steel.

[0017] The coil axis about which the coiled flow tube extends may extend in any direction. The coil axis may be a linear axis, or a curved axis, for example a circumferential axis. The coil axis may be substantially linear and may be substantially parallel with the first axis. Having the coil axis substantially linear and substantially parallel with the first axis may simplify the design and construction of the rotor.

[0018] The plurality of flow tubes may comprise a plurality of coiled flow tubes. The plurality of flow tubes may comprise a plurality of coiled flow tubes and a plurality of non-coiled flow tubes. The plurality of flow tubes may comprise only coiled flow tubes.

[0019] If there are a plurality of coiled flow tubes, the plurality of coiled flow tubes may be distributed substantially evenly around the first axis. The coil axis of each of the coiled flow tubes may be arranged at substantially the same distance from the first axis.

[0020] The plurality of coiled flow tubes may comprise at least one coiled flow tube coiled only in a first direction and at least one coiled flow tube coiled only in a second direction, the second direction being opposite to the first direction. One, or each, of the coiled flow tubes may include coils extending around an associated coil axis. Having pairs of coiled flow tubes which are coiled in opposite directions may result in a rotor which is less susceptible to deformation as the coiled flow tubes expand or contract while the rotor is heating or cooling.

[0021] The coiled flow tubes may be distributed around the first axis such that the coiling direction of the coils of the coiled flow tubes alternates around the first axis of the rotor. Similar to the above, having alternating coiling directions may result in a rotor that is less susceptible to deformation as the coiled flow tubes expand or contract while the rotor is heating or cooling.

[0022] With the exception of the direction of coiling all of the coiled flow tubes may be substantially identical with one another. For example, a coiled flow rube coiled in the first direction may be substantially identical to the coiled flow tubes coiled in the second direction with the exception of the coiling direction.

[0023] The, or each, coiled tube may comprise at least 5 coils, at least 7 coils, at least 10 coils. As mentioned above, each of the plurality of coils in a coiled flow tube may extend around a coil axis.

[0024] At least one coiled flow tube may include a plurality of coils and at least some of those coils may be spaced apart along a coil axis, which may be parallel to the first axis, to allow solar radiation to pass between the coils. The coils may be spaced by at least 0.2 cm, at least 0.5 cm, at least 1 cm, or least 2 cm. All the coils may be spaced apart by substantially the same amount as this facilitates manufacture, but it is possible that the coil spacing could vary along a coil axis, which the coils spaced further apart towards one or both ends of a coiled flow tube, or in a middle portion of a coiled flow tube. This may allow solar radiation to pass between the coils of one coiled flow tube to reach part of the inner surface of the coils of that coiled flow tube, to reach other coiled flow tubes that might be shaded by the coiled flow tube, or to reach other surfaces of the rotor, or a solar receiver which comprises the rotor.

[0025] The inlet tail and outlet tail of the, or each coiled flow tube may be connected by a plurality of coils which may extend around a coil axis. The inlet tail and outlet tail of the, or each, coiled tube may extend substantially straight such that the coil axis is offset from the first axis.

[0026] The outlet tail of the coiled flow tube may be directed towards the first axis within the outlet manifold. Within the outlet manifold the outlet tail of the flow tube may be directed towards the outlet from the outlet manifold. Within the outlet manifold the outlet tail may be directed away from external walls of the outlet manifold such that heated fluid exiting the coiled flow tube is not directed towards a surface from which significant heat loss may occur. The outlet tail may be directed away from external walls of the outlet manifold within 1cm, within 2cm, or within 5cm of an outlet from the outlet tail. The outlet manifold may comprise an outlet redirector and the outlet tail may be directed at the outlet redirector. The outlet redirector may comprise a surface to redirect flow entering the manifold through an outlet tail that impacts the surface towards the outlet. The surface of the outlet redirector may be any suitable shape and may be substantially continuous to provide the redirection function. The outlet redirector may be arranged on the first axis and the flow redirecting surface may extend around the first axis. Each outlet tail may have an associated outlet redirector, or one outlet redirector may be provided to redirect the flow from a plurality of, or all, outlet tails towards the outlet. The outlet redirector may comprise more than one redirecting surface. The outlet redirector may be substantially conical, or frustoconical, having a conical redirecting surface which narrows towards the outlet. The outlet redirector may be shaped like a horn, or a bell of a trumpet, which narrows towards the outlet.

[0027] The inlet tail of the, or each, coiled flow tube may be directed towards the first axis within the inlet manifold. Within the inlet manifold the inlet tail of the flow tube may be directed towards the inlet from the inlet manifold. This arrangement can facilitate fluid flow through the manifold from the inlet to the inlet tail.

[0028] The inlet manifold may comprise an inlet redirector and the inlet tail may be directed at the inlet redirector. The inlet redirector may comprise a surface to redirect flow entering the manifold through the inlet that impacts the surface towards an inlet tail. The surface of the inlet redirector may be any suitable shape and may be substantially continuous to provide the redirection function. The inlet redirector may be arranged on the first axis and the flow redirecting surface may extend around the first axis. Each inlet tail may have an associated inlet redirector, or one inlet redirector may be provided to redirect the flow from the inlet to a plurality of, or all, inlet tails. The inlet redirector may comprise more than one redirecting surface. The inlet redirector may be substantially conical, or frustoconical, having a conical redirecting surface which narrows towards the inlet. The outlet redirector may be shaped like a horn, or a bell of a trumpet, which narrows towards the inlet.

[0029] The inlet manifold may be connected to the outlet manifold by a connector. This may facilitate load transfer between the inlet and outlet manifolds and may reduce stress on the flow tubes. The use of a connector may also help to maintain alignment between the inlet manifold and outlet manifold. The connector may be fabricated from any suitable material. The connector may provide structural support and I or load transfer and may also act as a conductor along which heat may pass from the outlet manifold to the inlet manifold. The material from which the connector is formed may be a metal, for example a steel, as this provides reasonable structural properties.

[0030] There may be a plurality of connectors or one connector. The connector may extend along the first axis. The connector may be substantially hollow, for example in the form of a tube or pipe. The connector may be a substantially cylindrical. The connector may comprise a perforated tube. The perforated tube may include a plurality of perforations such that a wall of the tube is in the form of a lattice. The perforations in, or lattice structure of, the connector may limit, in use, heat transfer from the outlet manifold to the inlet manifold to no more than 200W in some examples. Some heat transfer from the outlet manifold to the inlet manifold via the connector may be helpful in pre-heating the working fluid before it passes through the flow tubes.

[0031] The connector may be substantially surrounded by a shield. The shield may act as an insulator to prevent the connector from overheating and I or potentially being damaged. The shield may comprise a material, such as a ceramic, which can be heated by solar radiation and re-radiate said heat to heat the flow tubes or other regions of a solar receiver comprising such a rotor.

[0032] The invention extends to a solar receiver comprising a shroud and a rotor, the rotor being substantially as described above and being arranged for rotation about the first axis within the shroud, the shroud having a side wall extending around the first axis such that is substantially surrounds the rotor, the shroud including an aperture through which solar radiation can be directed to heat a portion of the plurality the flow tubes of the rotor.

[0033] The side wall of the shroud may be any suitable shape, for example the side wall may be substantially cylindrical about a shroud axis. The shroud axis may be substantially co-axial with the first axis such that the rotor is arranged centrally within the shroud. The shroud axis may be offset from the first axis such that the rotor is arranged offset within the shroud.

[0034] The first axis may be arranged at an angle of between 0° and 90° from vertical such that the aperture is directed at an angle of between 0° and 90° below the horizontal. By directing the aperture at an angle of between 0° and 45° below the horizontal heated air may be less likely to escape such that a pocket of heated air is trapped within the shroud. This may enhance the efficiency of the solar receiver. It should be noted that vertical in this context means the direction in which Earth’s gravity acts, and horizontal is a direction perpendicular to that. The invention extends to a solar power station comprising a rotor, a solar concentrator, a working fluid driver and a load, the rotor being substantially as described above, the solar concentrator comprising optical elements to redirect and concentrate solar energy incident thereon onto a portion of the plurality of flow tubes of the rotor as the rotor rotates, the working fluid driver able to: cause a working fluid to flow through the rotor as it rotates such that the working fluid flows from the inlet manifold to the outlet manifold through the plurality of flow tubes such that the working fluid can be heated by the concentrated solar radiation to create a heated working fluid; cause a heated working fluid to flow to the load where the heated working fluid is cooled.

[0035] The working fluid driver may comprise one or more pumps or fans able to cause fluid to flow. The solar power station may comprise a motor or other drive means to cause the rotor to rotate about the first axis.

[0036] The solar concentrator may provide a concentration, c value, of over 500, over 1000, over 1500, over 2000, over 3000, or over 5000. The solar concentrator may comprise one or more heliostats.

[0037] The load can be any apparatus in which the working fluid is cooled for a purpose. For example, the load may be a heat exchanger, generator, heater, kiln or reactor. There may be more than one load. If more than one load is used, the loads may be arranged in parallel, or in sequence.

[0038] The rotor may be housed in a shroud to form a solar receiver. The solar receiver may be as described above.

[0039] The invention will now be described by way of example only with reference to the following figures in which:

[0040] Figure 1 shows a rotor for a solar receiver;

[0041] Figure 2 shows a coiled flow tube;

[0042] Figure 3 shows a top view of the rotor of Figure 1 ;

[0043] Figure 4 shows a side view of the rotor for Figure 1 ;

[0044] Figure 5 shows a cross section along the line A-A of Figure 4;

[0045] Figure 6 shows a solar receiver comprising a shroud and a rotor;

[0046] Figure 7 shows a different rotor for a solar receiver;

[0047] Figure 8 shows a top view of the rotor of Figure 7;

[0048] Figure 9 shows a different coiled flow tube;

[0049] Figure 10 shows a side view of the rotor for Figure 7;

[0050] Figure 11 shows a cross section along the line A-A of Figure 10;

[0051] Figure 12 shows a detail of the outlet manifold of Figure 11;

[0052] Figure 13 shows a detail of the inlet manifold of Figure 12;

[0053] Figure 14 shows a different solar receiver comprising a shroud and a rotor;

[0054] Figure 15 shows a schematic of a solar power station; and

[0055] Figure 16 shows a detailed view of a solar receiver in a solar power station. Figures 1 to 5 show a rotor 1 for a solar receiver (not shown in these figures). Figure 1 shows a perspective view of the rotor 1 for a solar receiver. The rotor 1 comprises an inlet manifold 2, an outlet manifold 4, and a plurality of flow tubes 6.

[0056] The inlet manifold 2 is spaced from the outlet manifold 4 along a first axis 8 about which the rotor 1 can be rotated when in use. The plurality of flow tubes 6 extend from the inlet manifold 2 to the outlet manifold 4 such that a fluid can flow from the inlet manifold 2 to the outlet manifold 4 through the plurality of flow tubes 6.

[0057] In this solar receiver 1 the plurality of flow tubes 6 comprise eight coiled flow tubes 10. A coiled flow tube 10 will be described in more detail in connection with Figure 3.

[0058] Figure 2 shows a single coiled flow tube 10 for use in the rotor 1 of Figure 1. The coiled flow tube 10 comprises an inlet tail 12 and an outlet tail 14 and a plurality of coils 16 which extend around a coil axis 18. In this example there are fifteen coils 16 around the coil axis 18, but this can vary depending upon the intended length of the coiled flow tube 10.

[0059] The coiled flow tube 10 is fabricated from an elongate cylindrical hollow pipe which is bent into a helical coiled form with the inlet and outlet tails 12,14 extending from the plurality of coils 16. It will be understood that there are many ways in a coiled flow tube 10 can be fabricated.

[0060] In this example the inlet tail 12 is directed substantially parallel with, and offset from, the coil axis 18. The outlet tail 14 is directed away from the coil axis 18.

[0061] The coils 16 are wrapped around the coil axis 18 at a pitch angle and this determines the gaps between adjacent coils 16 which affects the optical porosity of the coiled flow tube 10. The pitch angle of the coils 16 of the coiled flow tube 10 is a parameter that can be adjusted to modify the optical porosity of the coiled flow tube 10 by altering the spacing between the coils of the coiled flow tube.

[0062] The coiled flow tube 10 is coiled in a clockwise direction. A coiled flow tube 10 could be coiled in an opposite direction, in this case in an anticlockwise direction.

[0063] Figure 3 shows a view of rotor 1 of Figure 1 from above. The plurality of coiled flow tubes 10 are offset from and distributed substantially evenly around the first axis 8, and the coil axis 18 of each of the coiled flow tubes 10 is arranged substantially parallel with the first axis 8. The eight coiled flow tubes 10 are provided in four pairs, with each pair comprising a coiled flow tube 10 coiled in a clockwise direction and a coiled flow tube 10 coiled in an anticlockwise direction. The coiled flow tubes 10 are distributed around the first axis 8 in a sequence of alternating coiling directions, although other patterns are possible. In this way a rotor is created that has a rotational symmetry of four, which is equal to the number of coiled flow tubes 6 divided by two. If all the coiled flow tubes were coiled in the same direction, the rotational symmetry could be equal to the number of coiled flow tubes.

[0064] Figure 4 shows a side view of the rotor 1 of Figure 1 and Figure 5 shows a cross section view though the rotor 1 along the line A-A in Figure 4 and in Figure 5 the internal structure of the inlet manifold 2 and outlet manifold 4 can be seen.

[0065] The inlet manifold 2 includes an inlet 20 which is arranged on, and directed along, the first axis 8 away from the plurality of flow tubes 6. The inlet manifold 2 comprises an inlet chamber 22 fluidly coupled to the inlet 20 and the inlet tails 12 of the coiled flow tubes 10 so that fluid entering the inlet 20 can pass through the inlet chamber 22 within the inlet manifold 2 and be divided between the inlet tails 12 of the coiled flow tubes 10.

[0066] The outlet manifold 4 includes an outlet 24 which is arranged on, and directed along, the first axis 8 away from plurality of flow tubes 6. The outlet manifold 4 comprises an outlet chamber 26 fluidly coupled to the outlet 24 and the outlet tails 14 of the coiled flow tubes 10 so that fluid entering the outlet chamber 26 from the outlet tails 14 of the coiled flow tubes 10 can be combined and pass through the outlet 24. The outlet 24 leads to an outlet tube 42 which extends along the first axis 8 away from plurality of flow tubes 6 to allow fluid connection to the outlet 24 from a distance from the outlet manifold 4.

[0067] The outlet tails 14 are directed into the outlet manifold 4 towards the first axis 8. The outlet tails 14 are directed away from proximal external walls of the manifold 4. This means that the potential heat loss from the manifold 4 can be reduced. By contrast, the inlet tails 12 are directed substantially parallel with the first axis 8 into the inlet manifold 2.

[0068] Figure 6 shows a solar receiver 28 comprising a shroud 30 and a rotor 1. The rotor 1 is as shown in Figure 1 and is arranged for rotation about the first axis 8 within the shroud 30. In this case it is the flow tubes 10 that are within the shroud 30. The inlet 20 and outlet 24 are located such that they are accessible from outside of the shroud 30 through an opening, or extend through an opening in the shroud 30. One or both of the inlet and outlet 20,24 may be located within the shroud 30, and may be accessible through an opening in the shroud 30.

[0069] The shroud 30 has a side wall 32 that extends around the first axis 8 such that is surrounds the flow tubes 10 of the rotor 1. The shroud has a cap 34 and a base 36 which together enclose a shroud volume 38. The side wall 32 of the shroud 30 includes an aperture 40 through which solar radiation can be directed to heat a portion of the flow tubes 10 of the rotor 1.

[0070] Figures 7 to 13 show a different rotor 101 for a solar receiver 128. The rotor 101 comprises similar components to the rotor 1 and like features will be labelled with the same reference numerals incremented by 100. Figure 8 shows that the plurality of flow tubes 106 of the rotor 101 comprises ten coiled flow tubes 110.

[0071] Figure 8 shows a view from above of the rotor 101 and it can be seen that, as with the rotor 1 , the plurality of flow tubes 106 are distributed evenly around the first axis 108. The coiled flow tubes 110 are distributed around the first axis 108 in a sequence of alternating coiling directions, although other patterns are possible. In this case the rotor 101 has a rotational symmetry of five.

[0072] Figure 9 shows a coiled flow tube 110 from the rotor 101. The coiled flow tube 110 comprises eight coils 116. The pitch of the coils 116 is higher than the pitch of the coils 16 so that the coils 116 are separated slightly more than the coils of Figure 2 which increases the optical porosity of the coiled flow tube 110, allowing solar radiation incident on the rotor 101 to pass between the coils 116 of the coiled flow tubes 106 and illuminate regions of the rotor 101 that might otherwise be in shadow. The inlet and outlet tails 112,114 are both directed away from the coil axis 118.

[0073] Figure 10 shows a side view of the rotor 101 and Figure 11 shows a cross section view though the rotor 101 along the line A-A in Figure 10 and in Figure 11 the internal structure of the inlet manifold 102 and outlet manifold 104 can be seen.

[0074] The inlet manifold 102 includes an inlet 120 which is arranged on, and directed along, the first axis 108 away from the plurality of flow tubes 106. The inlet manifold 102 comprises an inlet chamber 122 fluidly coupled to the inlet 120 and the inlet tails 112 of the coiled flow tubes 110 so that fluid entering the inlet 120 can pass through the inlet chamber 122 within the inlet manifold 102 and be divided between the inlet tails 112 of the coiled flow tubes 110. The inlet manifold 102 include an inlet redirector 44 (shown in more detail in Figure 13).

[0075] The outlet manifold 104 includes an outlet 124 which is arranged on, and directed along, the first axis 108 away from plurality of flow tubes 106. The outlet manifold 104 comprises an outlet chamber 126 fluidly coupled to the outlet 124 and the outlet tails 114 of the coiled flow tubes 110 so that fluid entering the outlet chamber 126 from the outlet tails 114 of the coiled flow tubes 10 can be combined and pass through the outlet 124. The outlet 124 is directed along the first axis 8 away from plurality of flow tubes 6. The outlet manifold 104 include an outlet redirector 46 (shown in more detail in Figure 12).

[0076] Figures 12 and 13 shows details views of the outlet redirector 46 and the inlet redirector 44 installed in the rotor 101. The outlet redirector 46 comprises a surface 48 to direct flow entering the outlet manifold 104 through an outlet tail 114 towards the outlet 124. In this example the outlet redirector 46 is conical. The inlet redirector 44 comprises a surface 50 which is angled to redirect flow entering the inlet manifold 102 through the inlet 120 towards an outlet tail 114. In this example the inlet redirector 44 is conical.

[0077] Figure 14 shows a solar receiver 128 comprising a shroud 130 and a rotor 101. The rotor 101 is as shown in Figure 7 and is arranged for rotation about the first axis 108 within the shroud 130. In this case it is the flow tubes 110 that are within the shroud 130. The inlet 120 and outlet 124 are located such that they are accessible from outside of the shroud 130. One or both of the inlet 120 and outlet 124 may be located within the shroud 130, but may be accessible through an opening in the shroud 130.

[0078] Figure 15 shows a solar power station 52 comprising solar receiver 54, a solar concentrator 56, a working fluid driver 58, and a load 60. The solar receiver 54 comprises a rotor 64 which rotates within a shroud 66. The solar concentrator 56 in this example comprises a plurality of heliostat mirrors 68 which concentrate, reflect and direct solar radiation through an aperture 70 of the shroud 66 onto a portion of the rotor 64 therein. The solar concentrator concentrates the solar radiation by a factor of at least 1000. The rotor 64 is as described above and the portion of the rotor 64 onto which the solar concentrator 56 directs solar radiation comprises the flow tubes which are periodically illuminated as the rotor 64 rotates in the shroud.

[0079] In this example the working fluid driver 58 comprises one or more pumps and / or fans and, in use the working fluid driver 58 causes fluid to flow through the rotor 64 as it rotates. The working fluid may be air and, as it passes through the rotor 64 it passes through flow tubes. The flow tubes are periodically exposed to the solar radiation from the solar concentrator 56 and heat up. The heat passes from the flow tubes of the rotor 64 to the working fluid and creates a heated working fluid. The rotor 64 rotates so that some flow tubes are directly exposed to the concentrated solar radiation from the solar concentrator 56 and are heating up, which other flow tubes are not directly exposed to the concentrated solar radiation from the solar concentrator 56 and are cooled by the flow of working fluid therethrough.

[0080] The heated working fluid flows from the outlet of the rotor 64 through a load 60 where the working fluid is cooled to do work. The work may be to heat a kiln, oven, or other volume. The work may be to heat a transfer fluid to transfer heat elsewhere. The work may be to generate electricity by spinning a generator, for example by boiling water, or another fluid, to cause a turbine attached to the generator to spin. The working fluid may flow through one or more further loads, in this case there is one further load 62. The loads 60, 62 may be, for example, heat exchangers, generators, heaters, kilns or reactors. In this Figure the loads 60,62 are shown arranged in series, but loads may be arranged in parallel, or a combination of series and parallel.

[0081] The working fluid may be held within a closed circuit, so the cooled working fluid passes back through the working fluid driver 58 and is returned to the rotor 64. Some, or all, of the working fluid may be discharged and replaced with new working fluid.

[0082] Figure 16 shows a detailed view of a solar receiver 70 in a solar power station, for example the power station 52 of Figure 15. may be the same as the solar receiver 28 of Figure 6 or solar receiver 128 of Figure 14. The solar receiver 70 comprises a shroud 72 and a rotor 74 which rotates about a first axis 76. The shroud 72 comprises an aperture 78 which is directed towards the solar concentrator 56. The first axis 76 about which the rotor 74 rotates is arranged at an angle 80 of 30° to a vertical axis 82 such that the aperture 78 is directed at an angle 84 of 30° below a horizontal axis 86. As noted above the rotor may be arranged between 0° to 90° from the vertical.

Claims

Claims1. A rotor for a solar receiver, the rotor comprising: an inlet manifold having an inlet; an outlet manifold having an outlet; and a plurality of flow tubes; wherein the inlet manifold is spaced from the outlet manifold along a first axis about which the rotor is to be rotated, and the plurality of flow tubes extend from the inlet manifold to the outlet manifold such that a fluid can flow from the inlet manifold to the outlet manifold through the flow tubes; at least one of the plurality of flow tubes is a coiled flow tube and the, or each, coiled flow tube comprises an inlet tail connected to the inlet manifold and an outlet tail connected to the outlet manifold, the inlet tail and outlet tail are connected by at least one coil.

2. A rotor as claimed in claim 1 , in which the inlet tail and outlet tail are connected by a plurality of coils.

3. A rotor as claimed in claim 2, in which the plurality of coils of the, or each, coiled flow tube extend around a coil axis of the coiled flow tube.

4. A rotor as claimed in claim 3, in which the coil axis is substantially parallel with the first axis.

5. A rotor as claimed in any preceding claim, in which the plurality of flow tubes comprises a plurality of coiled flow tubes, optionally wherein each of the plurality of flow tubes is a coiled flow tube.

6. A rotor as claimed in claim 5, in which the plurality of coiled flow tubes are distributed substantially evenly around the first axis.

7. A rotor as claimed in any of claims 5 to 6, in which the plurality of coiled flow tubes comprises: at least one coiled flow tube coiled only in a first direction around an associated coil axis; and at least one coiled flow tube coiled only in a second direction around an associated coil axis, the second direction being opposite to the first direction.

8. A rotor as claimed in claim 7, in which the coiled flow tubes are distributed around the first axis such that the coiling direction of the coiled flow tubes alternates around the rotor and optionally wherein, with the exception of the direction of coiling, the coiled flow tubes coiled in the first direction are substantially identical to the coiled flow tubes coiled in the second direction.

9. A rotor as claimed any preceding claim, in which the, or each, coiled tube comprises at least 5 coils extending around the coil axis.

10. A rotor as claimed in any preceding claim, in which the inlet tail and outlet tail of at least one coiled flow tube are connected by a plurality of coils, and the plurality of coils are in the form of a helix.

11. A rotor as claimed in any preceding claim, in which the inlet tail and outlet tail of at least one flow tube are connected by a plurality of coils and the plurality of coils of at least one coiled flow tube are spaced to allow solar radiation to pass between the coils.

12. A rotor as claimed in any preceding claim, in which the inlet tail and outlet tail of the, or each coiled flow tube are connected by a plurality of coils which extend around a coil axis, and in which the inlet tail and outlet tail of the, or each, coiled tube extends substantially straight such that the coil axis is offset from the first axis.

13. A rotor as claimed in any preceding claim, in which the outlet tail of the coiled flow tube is directed towards the first axis within the outlet manifold.

14. A rotor as claimed in any preceding claim, in which the outlet manifold comprises an outlet redirector, the outlet redirector comprising a surface to direct flow entering the manifold through an outlet tail towards the outlet, optionally wherein the outlet redirector is conical.

15. A rotor as claimed in any preceding claim, in which the inlet tail of the coiled flow tube is directed towards the first axis.

16. A rotor as claimed in any preceding claim, in which the inlet manifold comprises an inlet redirector, the inlet redirector comprising a surface to direct flow entering the manifold through the inlet towards an inlet tail, optionally wherein the inlet redirector is conical.

17. A rotor as claimed in any preceding claim, in which the inlet manifold is connected to the outlet manifold by a connector which extends along the first axis, optionally wherein the connector comprises a perforated tube.

18. A rotor as claimed in claim 17, in which the connector is substantially surrounded by a shield.

19. A solar receiver comprising a shroud and a rotor, the rotor being substantially as claimed in any preceding claim and being arranged for rotation about the first axis within the shroud, the shroud having a side wall extending around the first axis such that is substantially surrounds the rotor, the shroud including an aperture through which solar radiation can be directed to heat a portion of the plurality the flow tubes of the rotor.

20. A solar receiver as claimed in claim 19, in which the side wall is substantially cylindrical about a shroud axis which is substantially co-axial with the first axis.

21. A solar receiver as claimed in claim 19 or claim 20, in which the first axis is arranged at an angle of between 0° and 90° from vertical such that the aperture is directed at an angle of between 0° and 90° below the horizontal.

22. A solar power station comprising a rotor, a solar concentrator and a working fluid driver and a load, the rotor being as claimed in any of claims 1 to 18, the solar concentrator comprising optical elements to redirect and concentrate solar energy incident thereon onto a portion of the plurality of flow tubes of the rotor as the rotor rotates, the working fluid driver able to: cause a working fluid to flow through the rotor as it rotates such that the working fluid flows from the inlet manifold to the outlet manifold through the plurality of flow tubes such that the working fluid can be heated by the concentrated solar radiation to create a heated working fluid; cause a heated working fluid to flow to the load where the heated working fluid is cooled.

23. A solar power station as claimed in claim 22, in which the solar concentrator provides a concentration of over 2000 and optionally the solar concentrator comprises one or more heliostats.

24. A solar power station as claimed in any of claims 22 to 23, in which the load comprises a heat exchanger, generator, heater, kiln or reactor.

25. A solar power station as claimed in any of claims 22 to 24, in which the rotor is housed in a shroud to form a solar receiver, the solar receiver being as claimed in any of claims 19 to 21.

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