GB2530791A

GB2530791A - Domestic heliostat

Info

Publication number: GB2530791A
Application number: GB1417469.2A
Authority: GB
Inventors: Diva Tommei; Daniele Tommei
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-10-03
Filing date: 2014-10-03
Publication date: 2016-04-06
Also published as: GB201417469D0

Abstract

A heliostat contained within a mechanical enclosure 100 that optimizes the heliostat for domestic applications such as domestic lighting. Protection from outside weather is achieved be the spherical shape of the enclosure which is transparent. A steering control sensor 8, a mechanical mirror-steering mechanism 5 and a steering control system 6 are preferably mounted at the rear side of a mirror 3. The mirror is moveable about two axes and the steering control sensor is preferably in wireless communication with the steering control system so as to accurately guide the movement of the mirror. The mirror may be a plane or curved mirror. The heliostat device is electrically self-powering preferably by means of photovoltaic cells 4a,4b.

Description

DOMESTIC HELIOSTAT

[0001] The present invention pertains to a heliostat protected by a mechanical enclosure that renders it optimised for domestic lighting use according to the preamble of claim 1.

FIELD OF THE INVENTION AND PRIOR ART

[0002] As is known, a heliostat is a device used to follow the Sun's route during the span of the day, usually to orient the light thereof towards a precise target thanks to the help of one or more mirrors.

[0003] Today heliostats are mostly used in industrial thermodynamic processes to increase the temperature of thermal devices on towers, by the simultaneous use of several heliostats pointing at the same target, which are indispensable to obtain the necessary temperatures for devices that convert heat into electricity.

[0004] However, other applications for heliostats may include light-redirection for domestic and city uses) in which the heliostat redirects sunlight towards an object, room) street) monument or piazza to illuminate, brighten and/or warm.

[0005] Most sunlight redirection systems in use today are expensive and require intensive and invasive installation procedures that could be obviated by the subtle use of heliostats.

[0006] However, if one wanted to use a heliostat as a domestic device sited outdoors in order for it to redirect sunlight indoors, the heliostat systems in use today would prove to be rather inadequate.

Most heliostats, in fact, focus on emphasizing and optimising the features that are fundamental in industrial applications, such as pointing accuracy, planarity of the mirror, stability and robustness of the mechanics. But other features become important when developing a heliostat for domestic applications, such as but not limited to compactness, portability, self-powered autonomy) lightness, low maintenance times, low-cost of the entire system and protection from outside weather.

[0007] In order to create a heliostat that is optimised for domestic use one needs to revisit the key components that make a heliostat and re-arrange them so that optimization of said domestic features are emphasized.

[0008] For example, patent US4283887 defines a bubble-like enclosure for a heliostat that is inflated by filling it with pressurised air. Whilst this patent clearly defines a means of protection of the heliostat contained within such an enclosure, it is in no way addressing any of the other features of compactness, portability) self-powered autonomy, lightness) low-maintenance time or low-cost. In fact, such a protective structure is intended for larger heliostats that need to be installed on the ground and are supported by a foundation in the form of a soil filled, plastic ring-bag mounted in the ground at the heliostat site.

[0009] Patent US7887188, while disclosing a heliostat comprised of a mirror that is placed in two hemispheres that are joined together, wherein the mirror contains a plurality of wheels that run on the inner surface of the sphere so as to move it and orient it towards the target, it manages to maximise the mirror size that can be fit inside the sphere but completely fails at providing an optically smooth surface for the inbound and outbound sunlight, where by inbound one means the sunlight from the sun to the mirror and by outbound the sunlight reflected from the mirror to the target. Such a hemisphere joint does not allow both inbound and outbound sunlight to enter or exit unhindered from the disclosed enclosure. More importantly, in operation the frictional contact between the wheels and the sphere's inner surface would inevitably start to leave marks on the inner surface and over time these would not only become unsightly, but would also negatively affect the optical performance of the heliostat.

SUMMARY AND OBJECTS OF THE INVENTION

The present invention provides a mechanical enclosure for a heliostat that renders it optimised for domestic lighting use in accordance with independent claim 1. Further preferable features of the invention are provided in the dependent claims.

The present invention pertains to a domestic heliostat that encompasses all the characteristics of a domestic object in one compact device, those characteristics being portability, light-weight, self-powering, wireless, good looks, and resistance to outdoor weather. It is also designed to have a low cost of manufacture.

According to an example embodiment, a domestic heliostat includes: a steerable mirror, a mechanical mirror-steering mechanism, a steering control-system, a steering-control sensor, all contained within a mechanical enclosure wherein said mechanical enclosure has a break-line or joint about which said enclosure may be separated, characterised in that: at least one portion of the mechanical enclosure is substantially spherical in shape and such portion is made of optically transparent material; the trajectory of the joint that divides the mechanical enclosure in two parts is optimised to allow the insertion of the largest possible mirror inside the mechanical enclosure so as to maximise the solar energy and illumination reflected on the target and this optimization is saddle shaped or elliptical; the steerable mirror is substantially circular in order to maximize the reflective area that will fit inside the mechanical enclosure, which is substantially spherical in shape, and said steerable mirror has a radius that is smaller than the inner radius of the spherical portion of the mechanical enclosure; the steerable mirror is rotatably mounted about two axes that intersect at or near the geometric spherical centre of the substantially spherical portion of the mechanical enclosure; the steerable mirror is also mounted such that its reflective surface over a substantial portion of its steerable rotatable position range, faces said substantially spherical portion of enclosure made of optically transparent material; the steering-control sensor is fixed to the inner surface of the mechanical enclosure; and the heliostat is electrically self-powered.

So, in one aspect of the present invention a mechanical enclosure for a heliostat is characterised in that: the spherical portion of the mechanical enclosure of said heliostat is greater in solid angular extent than a hemisphere and preferably greater in solid angular extent than five fourths of a hemisphere; the joint trajectory that divides the mechanical enclosure in two parts additionally allows the insertion of a mechanical mirror-steering mechanism and steering control-system into said enclosure and said joint trajectory is elliptical, or is saddle shaped and it does not intersect the portion of the mechanical enclosure which is substantially spherical in shape and is made of optically transparent material; moreover, said joint trajectory is chosen such as to leave as great an area as possible, and possibly all, of the substantially spherical portion of transparent enclosure unbroken.

The electrical self-power that powers the mirror steering mechanism and control system of the heliostat is provided by one or more first photovoltaic cells, wherein the first photovoltaic cell(s) are located within the mechanical enclosure, which is provided with a transparent window where the first photovoltaic cell(s) are positioned so as to be visible through the transparent window. This window may be partly or wholly provided by the substantially spherical portion of the mechanical enclosure that is made of optically transparent material. These first photovoltaic cell(s) are mounted co-moving with the steerable mirror such that their optically sensitive surface(s) face substantially in the same direction as the reflective surface of the steerable mirror.

The steering-control sensor is fixed to the inner surface of the mechanical enclosure and is positioned such as to minimise its obstruction to the passage of light from the Sun to the heliostat's target, and preferably below the horizontal midline plane of said mechanical enclosure. The steering-control sensor may be powered by the first photovoltaic cells, but is preferably self-powered independently of the heliostat's electrical self-power, and is preferably self-powered by one or more second photovoltaic cells co-mounted with the steering-control sensor. These second photovoltaic cell(s) are mounted such that their optically sensitive surface(s) face towards the centre of the steerable mirror or towards the zenith. The steering-control sensor preferably communicates with the steering control-system wirelessly via an infra-red (IR) link or a radio link, although it may also be directly wired to it.

The mechanical mirror-steering mechanism and the steering control-system are both mechanically mounted on the rear (non-reflective side) of the steerable mirror and are substantially hidden from sight of external viewers by the non-transparent sections of the heliostat's mechanical enclosure and/or by the steerable mirror. The mechanical mirror-steering mechanism is preferably attached to the mechanical enclosure at substantially one position only on a non-transparent portion of the mechanical enclosure.

The steering control mechanism is remotely controllable from outside of the mechanical enclosure preferably without a wired link, via a radio link, an infra-red (IR) link, or an acoustic link that is preferably ultrasonic.

The mechanical enclosure is substantially rigid, is substantially sealed from the external environment and is preferably hermetically sealed, is preferably provided with desiccator means such as silica gel, and is made of material(s) that are substantially shatter-proof and are preferably plastics materials, e.g. methacrylate polymers or polycarbonate. The overall size of the mechanical enclosure is optimised for domestic lighting use; the largest dimension of the mechanical enclosure is preferably not less than 20cm and preferably not more than 100cm, and more preferably not more than 60cm.

All of the components internal to the mechanical enclosure are preferably chosen to be of lighter construction than would be required to withstand normal outdoor wind loading in the absence of the enclosure, and the thickness of the steerable mirror is preferably chosen to be substantially less than the minimum thickness of the mirror that would be required to avoid substantial bending were the mirror to be exposed directly to normal outdoor wind loading. Also, the mechanical mirror-steering-mechanism is chosen to have substantially smaller holding torque than would otherwise be required were said steerable mirror to be exposed directly to normal outdoor wind loading. In this way, much lighter and cheaper components may be used to build a well functioning heliostat by minimising their strength or torque specifications through shielding of the components from wind loading by the mechanical enclosure.

The external shape of the mechanical enclosure is such as to provide low wind-loading torque on the mechanical enclosure when exposed to winds coming from any horizontal direction; the external shape of the mechanical enclosure is preferably an ellipsoid with one axis in the vertical direction or more preferably is a spheroid or sphere. The material of the transparent portion of the mechanical enclosure is thin enough to prevent significant refraction errors of pointing and is not more than 10mm thick, and preferably not more than 5mm thick) and more preferably not more than 2mm thick; also, the material of the transparent section of the mechanical enclosure is sufficiently optically smooth to prevent optical aberrations from significantly degrading the heliostat pointing precision and is preferably optically smooth to at least lOum, and more preferably to 5um, and even more preferably equal to or better than lum Finally, the steerable mirror can be a plane mirror) a concave mirror or a convex mirror.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIEMENT

[0010] By referring to Fig 1 a domestic heliostat in a mechanical enclosure according to the present invention is designated as a whole with the reference number 100.

[0011] Fig 1 shows a sideways view of the domestic heliostat's mechanical enclosure 100 as a whole, which is composed of a substantially spherical and transparent front hard shell 1, and a not necessarily spherical and preferably not transparent rear shell 2 joined together by a joint or break-line 9 in the shape of a saddle in this particular embodiment. Fig 2a-c show lateral views of the inside of the rear shell 2. Fig 3a, 3b show different views of the front transparent hard shell 1.

[0012] Fig 1 shows a steering control sensorS sited on the inside of the front hard shell 1, and that the rear shell 2 rests on a not necessarily flat stand 7 and supports internally a rigid circular steering mirror 3 with two attached photovoltaic cells 4a and 4b; a mechanical mirror-steering mechanism 5 and a steering control system 6 can also be seen mounted to the rear of the mirror.

[0013] Fig 2a shows an inside view of rear shell 2 of mechanical enclosure 100 comprising the steering mirror 3, a not necessarily spherical housing 10 where mechanical mirror-steering mechanisms and steering control system 6 (not shown) are housed, and the stand 7. Fig Zb shows a rear view of the rear shell 2 of mechanical enclosure 100 comprising the steering mirror 3, the housing 10 and the stand 7. Fig 2c shows an upper view of the rear shell 2 comprising the steering mirror 3, the housing 10 and the stand 7. In each figure 2 the saddle shaped break-line 9 defines the perimeter of rear shell 2.

[0014] In Fig land 2 joint or break-line 9 allows this particular embodiment to maximise the optically smooth area of transparent cover 1 available in front of the steering mirror 3 by retaining a saddle shape that at the same time is able to maximise the size of the steering mirror 3 that may be fitted within it. With this particular joint or break-line shape (or trajectory) 9, the front transparent hard shell 1 of mechanical enclosure 100 is extended enough so as to allow the unobstructed entrance of sunlight through the front hard shell 1 towards the steering mirror 3 and the exit via reflection of sunlight from the steering mirror 3 through the front hard shell 1 towards the target (not shown), over a very wide range of mirror steered positions. In situations in which the steering mirror is laterally rotated to its maximum -such as at sunrise and sunset in the most densely occupied regions of the northern hemisphere -the steering mirror 3 will have a clear view of the sky through the transparent front hard shell 1, unhindered by the joint or break-line 9 that must necessarily be present (somewhere) in order for the steering mirror 3 to be fitted inside the mechanical enclosure 100 during manufacture and for maintenance.

[0015] Fig 3a shows a side view of the transparent front hard shell 1 of the mechanical enclosure 100, whereby the joint or break-line 9 is rendered obvious and part of the internal surface of the front hard shell 1 can be seen as well. Fig 3b shows a rotated side view of the front hard shell 1 of the mechanical enclosure 100, whereby the joint or break-line 9 is rendered obvious and again part of the internal surface of the front hard shell 1 can be seen.

[0016] In Fig 1 the steering control sensor S is sited on the front hard shell tin front of steering mirror 3so as to receive the reflected sunlight from the steering mirror 3 (outbound light) and hide as little as possible of the steering mirror 3 reflective surface from the target. Steering control sensor S is in this particular embodiment is wirelessly connected to steering control system 6 through a pulsed-IR system (not shown) and powered by separate co-located photovoltaic cell(s) (not shown).

[0017] In Fig 1 the mechanical mirror-steering mechanism S contains all the gears and motors (not shown) that move the steerable mirror 3 and the steering control-system 6 contains all the electronics that dictate the movement of the steerable mirror 3 through the mechanical mirror-steering mechanism S. The steering control system 6 is wirelessly connected to the steering control sensorS so as to accurately guide the movement of the steering mirror 3.

[0018] In Fig land 2 the circular steerable mirror 3 is mounted on two axes around which it is rotatably mounted, that intersect at or near the geometric spherical centre of the front hard shell 1.

This allows the steering mirror to be able to rotate freely without impacting the front hard shell 1, or the rear sheIl2, or the stand 7. Housing 10, the mechanical mirror-steering mechanism sand the steering control system 6, are connected to the mechanical enclosure 100 through a single point of contact that lies on one of the two axes of rotation.

[0019] In Fig 1, two photovoltaic cells 4a and 4b that accumulate the power for the steering control system 6 to move the steerable mirror 3 through the mechanical mirror-steering mechanism 5, are fixed to the surface of the steerable mirror 3, or onto an outer frame around the mirror that extends beyond the perimeter of the mirror's reflective surface,. This location allows the photovoltaic cells 4a and 4b to always move jointly with the steerable mirror 3, which avoids shadowing of the steerable mirror 3 by the photovoltaic cells and, at the same time, enables the photovoltaic cells to always be oriented towards the sun, because the steering mirror 3 is oriented (partially, and not usually directly) towards the sun automatically by the steering control system.

[0020] In Fig land 2 the mechanical enclosure 100 includes the stand 7, which can have different shapes according to its installation, such as a fIat foot for desk mounting, or a railing clasp for mounting on a balcony.

S

[0021] In Fig 3a and 3b the trajectory of joint or break-line 9 that divides in two the mechanical enclosure 100 is saddle shaped so as to minimise the optical aberrations experienced by the sunlight coming into and going out of after being reflected off of the steering mirror 3, the mechanical enclosure 100, whilst maximising the size of the steerable mirror 3 and thus the solar energy and illumination delivered to the target.

Claims

CLAIMSl.A heliostat comprising a steerable mirror, a mechanical mirror-steering mechanism, a steering control-system, a steering-control sensor, all contained within a mechanical enclosure wherein said mechanical enclosure has a break-line or joint about which said enclosure may be separated, characterised in that: at least one portion of the mechanical enclosure is substantially spherical in shape; said substantially spherical portion of enclosure is made of optically transparent material; the trajectory of said joint along the surface of said enclosure is optimised to allow insertion of the largest possible mirror into said portion of the mechanical enclosure which is substantially spherical in shape; said steerable mirror is substantially circular with radius smaller than the inner radius of said spherical portion of enclosure; said steerable mirror is rotatably mounted about two axes; said two axes intersect at or near the geometric spherical centre of said substantially spherical portion of enclosure; said steerable mirror is mounted such that its reflective surface over a substantial portion of its steerable rotatable position range, faces said substantially spherical portion of enclosure made of optically transparent material; said steering-control sensor is fixed to the inner surface of the mechanical enclosure; said heliostat is electrically self-powered.
2. A heliostat as in Claim 1 wherein said substantially spherical portion of enclosure is greater in solid angular extent than a hemisphere.
3. A heliostat as in Claim 1 wherein said substantially spherical portion of enclosure is greater in solid angular extent than five fourths of a hemisphere.
4. A heliostat as in Claims 1 through 3 wherein said joint trajectory additionally allows insertion of said mechanical mirror-steering mechanism and steering control-system into said enclosure.
5. A heliostat as in Claims 1 through 4 wherein said joint trajectory is elliptical, or is saddle shaped.
6. A heliostat as in Claims 1 through 5 wherein said joint trajectory does not intersect said one portion of the mechanical enclosure which is substantially spherical in shape and which is made of optically transparent material.
7. A heliostat as in Claims 1 through 6 wherein said joint trajectory is chosen such as to leave as great an area as possible, and possibly all, of said substantially spherical portion of transparent enclosure unbroken.
8. A heliostat as in any of the previous Claims) wherein said electrical self-power is provided by one or more first photovoltaic cells.
9. A heliostat as in Claim 8 wherein said first photovoltaic cell(s) are located within said mechanical enclosure.
10. A heliostat as in Claim 9 wherein said mechanical enclosure is provided with a transparent window and said first photovoltaic cell(s) arc positioned within said mechanical enclosure such as to be visible through said window.
11. A heliostat as in Claim 10 wherein said transparent window is partly or wholly provided by said substantially spherical portion of enclosure made of optically transparent material.
12. A heliostat as in any of Claims 9 through 11 wherein said first photovoltaic cell(s) are mounted co-moving with said steerable mirror.
13. A heliostat as in claim 12 wherein said first photovoltaic cell(s) are mounted such that their optically sensitive surface(s) face substantially in the same direction as the reflective surface of said steerable mirror.
14. A heliostat as in any of the previous Claims wherein said steering-control sensor fixed to the inner surface of said mechanical enclosure is positioned such as to minimise its obstruction to the passage of light from the Sun to the heliostat's target.
15. A heliostat as in Claim 14 wherein said steering-control sensor is positioned below the horizontal midline plane of said mechanical enclosure.
16. A heliostat as in any of the previous Claims wherein said steering-control sensor is self-powered independently of said heliostat electrical self-power.
17. A heliostat as in Claim 16 wherein said steering-control sensor is self-powered by one or more second photovoltaic cells co-mounted with said steering-control sensor.
18. A heliostat as in Claim 17 wherein said second photovoltaic cell(s) are mounted such that their optically sensitive surface(s) face towards the centre of said steerable mirror
19. A heliostat as in Claim 17 wherein said second photovoltaic cell(s) are mounted such that their optically sensitive surface(s) face towards the zenith.
20. A heliostat as in any of Claims 16 through 19 wherein said steering-control sensor communicates wirelessly with said steering control-system.
21. A heliostat as in Claim 20 wherein said wireless communication is via an infra-red (IR) link.
22. A heliostat as in Claim 20 wherein said wireless communication is via a radio link.
23. A heliostat as in any of the previous Claims wherein said mechanical mirror-steering mechanism and said steering control-system are both mechanically mounted on the rear (non-reflective side) of said steerable mirror.
24. A heliostat as in any of the previous Claims wherein said mechanical mirror-steering mechanism is attached to said mechanical enclosure at substantially one position only.
25. A heliostat as in Claim 24 wherein said substantially one mechanical attachment position on said enclosure is situated on a non-transparent portion of said enclosure.
26. A heliostat as in any of the previous Claims wherein said mechanical mirror-steering mechanism and said steering control-system are substantially hidden from sight of external viewers by the non-transparent sections of said enclosure and/or by said steerable mirror.
27. A heliostat as in any of the previous claims wherein said steering control mechanism is remotely controllable from outside said enclosure without a wired link.
28. A heliostat as in Claim 27 wherein said wireless remote control is via a radio link.
29. A heliostat as in Claim 27 wherein said wireless remote control is via an infra-red (IR) link.
30. A heliostat as in Claim 27 wherein said wireless remote control is via an acoustic link.
31. A heliostat as in Claim 30 wherein said wireless acoustic link is ultrasonic.
32. A heliostat as in any of the previous Claims wherein said mechanical enclosure is substantially sealed from the external environment.
33. A heliostat as in Claim 32 wherein said seal is hermetic.
34. A heliostat as in either of Claims 32 or 33 wherein desiccator means are provided within said mechanical enclosure.
35. A heliostat as in Claim 34 wherein said desiccator means are silica gel.
36. A heliostat as in any of the previous Claims wherein said mechanical enclosure is substantially made of material(s) that are substantially shatter-proof.
37. A heliostat as in any previous Claims wherein said mechanical enclosure is substantially made of plastics materials.
38. A heliostat as in Claim 37 wherein said plastics materials include methacrylate polymers.
39. A heliostat as in Claim 37 or Claim 38 wherein said plastics materials include polycarbonate.
40. A heliostat as in any previous Claim wherein the overall size of the mechanical enclosure is optimised for domestic lighting use.
41. A heliostat as in any of the previous Claims wherein the largest dimension of the mechanical enclosure is not less than 20cm and not more than 100cm, and preferably not more than 60cm.
42. A heliostat as in any of the previous Claims wherein the mechanical enclosure is substantially rigid.
43. A heliostat as in any of the previous Claims wherein the mechanical strengths of any or all of the components internal to said mechanical enclosure are chosen to be smaller than required to withstand normal outdoor wind loading in the absence of said enclosure.
44. A heliostat as in Claim 43 wherein the thickness of said steerable mirror is chosen to be substantially less than the minimum thickness of mirror required to avoid substantial bending were the mirror to be exposed directly to normal outdoor wind loading.
45. A heliostat as in Claim 43 wherein said mechanical mirror-steering mechanism is chosen to have substantially smaller holding torque than would otherwise be required were said steerable mirror to be exposed directly to normal outdoor wind loading.
46. A heliostat as in any of the previous claims wherein the external shape of said mechanical enclosure is such as to provide low wind-loading torque on said enclosure when exposed to winds coming from any horizontal direction.
47. A heliostat as in any of the previous claims wherein the external shape of said mechanical enclosure is an ellipsoid with one axis in the vertical direction.
48. A heliostat as in any of the previous claims wherein the external shape of said mechanical enclosure is a spheroid or sphere.
49. A heliostat as in any of the previous Claims wherein the material of the transparent section of said mechanical enclosure is thin enough to prevent significant refraction errors of pointing.
50. A heliostat as in Claim 49 wherein the thickness of material of the transparent section of said mechanical enclosure is not more than 10mm, and preferably not more than 5mm, and more preferably not more than 2mm.
51. A heliostat as in any of the previous Claims wherein the material of the transparent section of said mechanical enclosure is sufficiently optically smooth to prevent optical aberrations from significantly degrading the heliostat pointing precision.
52. A heliostat as in Claim 51 wherein the material of the transparent portion of said mechanical enclosure is optically smooth to at least lOum, and preferably Sum, and more preferably better than lum.
53. A heliostat as in any of the previous Claims wherein said steerable mirror is a plane mirror.
54. A heliostat as in any of Claims 1 through 52 wherein said steerable mirror is a concave mirror.
55. A heliostat as in any of Claims 1 through 52 wherein said steerable mirror is a convex mirror.