GB2115135A

GB2115135A - Thermal storage panel for storing solar energy

Info

Publication number: GB2115135A
Application number: GB08204392A
Authority: GB
Inventors: Giovanni Pellegrini; Jacques Mignot; Salvatore Sacco
Original assignee: European Atomic Energy Community Euratom
Current assignee: European Atomic Energy Community Euratom
Priority date: 1982-02-15
Filing date: 1982-02-15
Publication date: 1983-09-01

Abstract

The thermal storage panel is formed with sealed hollow hemispheres (2) containing as a storage medium (4) a substance which undergoes a reversible chemical reaction or a reversible phase transformation at a temperature substantially above room temperature. The panel may be constructed as a window blind or a folding shutter or a rigid shutter. <IMAGE>

Description

SPECIFICATION Window shutters and blinds for collection and storage of solar energy The present invention relates to apparatus, for example window shutters or window blinds, and a method, for absorption, storage and subsequent emission into a building of solar thermal energy.

It is well known that substantial heat losses occur from buildings due to heat transfer through windows down a temperature gradient between the inside and the outside of the building. Due to the low insulative properties of glass and the generally large area of the windows in a building, these heat losses are usually greater than those through the remaining fabric of the building. Heretofore, these heat losses have been reduced by the provision of double-glazing and by improving the insulative properties of window frames. To illustrate comparisons between the heat losses due to typical window and wall arrangements, Annex 1 shows the heat transfer coefficient (K) for three types of existing windows and for two types of wall construction.Annex 2 shows typical heat loss rates for a window having a surface area of 6.3 m2 for three different values of the heat transfer coefficient (K) of the window, the average temperature difference between the inside and the outside of the window being 1 2.5 C in each case.

It may be seen from the above data that improvements in window insulation are required in order to reduce heat losses from buildings and thereby to reduce heating costs. It is also known to have shutters or blinds at the outside or inside, respectively, of a window of a building in order to shut out sunlight during daylight hours, to reduce heat losses from the building through the window during the night and to provide improved privacy and security for occupants of the building.

It is also known that thermal energy from the sun can be stored in storage media such as, for example, water, sand, or rocks.

In such storage media the additional heat energy stored in the medium due to a rise in temperature of the medium corresponds to the rise in the specific heat of the medium, and as such the quantity of the additional heat energy stored is therefore dependent upon the specific heat capacity of the medium.

However, one aspect of this invention preferably uses a storage medium in which, within a particular temperature range, energy input due to a rise in temperature causes the medium to undergo a phase transformation. Accordingly, energy corresponding to both the increase in the rise in the specific heat of the medium due to the rise in temperature and the heat of transformation can be stored in the medium, which energy is dependent upon both the specific heat capacity of the medium and the specific heat of transformation.

This invention may alternatively employ media such as, for example, a salt mixture having "reciprocal salt pairs" for which a reversible chemical reaction occurs above a particular temperature such that a high quantity of heat relative to the specific heat of the mixture can be stored in the mixture if the temperature of the mixture is raised above the particular temperature. The heat of reaction absorbed by the mixture when so heated to a temperature above the particular temperature is added to the increase in specific heat of the mixture due to the rise in temperature. This results in a high specific heat storage capacity for the mixture.

On lowering the temperature of the mixture to a value below the particular temperature, the stored thermal energy in the mixture, constituted by the heat of reaction and the loss of specific heat of the mixture due to the fall in temperature is released.

The reversible chemical reaction occurring in a mixture of two salts having "reciprocal salt pairs" is of the type: XY + RS v RY + XS The salts stable below the particular reaction temperature are XY and RS. On raising the temperature of the mixture to a value greater than that of the particular temperature, an endo-thermic chemical reaction occurs, as shown, giving the products RY and XS. A reverse exothermic chemical reaction occurs on lowering the temperature of the mixture to a value lower than that of the particular temperature.

In Annex 3 is shown the energy storage capacity of each of three typical energy storage media, and, by way of comparison, the energy storage capacity of water is shown also, assuming in each case a temperature difference between the temperatures of the initial and the final states of the storage medium.

It will be seen that the energy storage capacity of the reciprocal salt pair corresponding to (Ba(OH)2. 8H20 + 2KNO3) is considerably greater than that of any one of the other examples.

For the successful use of media which undergo a phase transformation upon change of temperature in a solar energy storage system, the phase transformation preferably occurs at a temperature which is within the temperature range of utilisation of a solar energy collector, typically a temperature range substantially above normal room temperature, for example 30"C to 80"C. In addition the media should be capable of maintaining their thermal and physical properties upon repeated thermal cycling within the temperature range of operation. However, some salt hydrates and other energy storage media have been found to degrade upon repeated thermal cycling due to the loss of water of crystallization or due to segregation phenomena which are due to differences in density of the separate components of the material.

The present invention relates to apparatus and a method of reducing and/or compensating for energy losses, for example through windows in buildings, by the use of shutters or blinds which are capable of absorbing and storing solar thermal energy, or other incident energy, during the day and of emitting the stored thermal energy into the building during the evening and the night.

The present invention accordingly provides a thermal storage panel capable of storing thermal energy in response to solar irradiation and including as a storage medium a substance which undergoes a reversible chemical reaction or a reversible phase transformation at a temperature substantially above room temperature.

The present invention further provides a thermal energy storage panel comprising a supporting member and a thermoplastic sheet, the sheet being formed with a multiplicity of blisters containing an energy storage medium, which energy storage medium undergoes a reversible chemical reaction or a reversible phase transformation at a temperature substantially above room temperature.

The present invention further provides apparatus for absorption, storage and subsequent emission into a building of solar thermal energy, the apparatus comprising one or more members arranged at a side of the building, each member including an energy storage medium, which energy storage medium undergoes a reversible chemical reaction or a reversible phase transformation at a temperature substantially above room temperature and is incorporated in the member, and being movable from a first position at which first position the member can absorb and store incident solarthermal energy, to a second position, at which second position the member can emit the stored thermal energy into the building.

Embodiments of the present invention will now be described by way of example with reference to and as illustrated in the accompanying drawings, in which: Figures la and it show a plane and a transverse section orthogonal to the plane of a sheet for incorporation of a storage medium according to an embodiment of the present invention; Figure2 shows a blind arrangement arranged for energy emission into a building according to an embodiment of the present invention; Figures 2a, 2b and 2e show th ree arrangements of the storage medium of the blind arrangement of Figure 2; Figure 3 shows the blind arrangement of Figure 2 arranged for solar thermal energy absorption and storage; Figure 4 shows an arrangement for a window shutter according to an embodiment of the present invention;; Figures 5a, 5b, 5c and 5d show an arrangement for a window shutter according to an embodiment of the present invention; Figure 6 shows an arrangement for a storage element according to an embodiment of the present invention.

According to an embodiment of the present invention a heat storage medium is incorporated in a member such as a window shutter, window blind or other storage element disposed at the side of a building, the medium having a substantial heat storage capacity over a temperature range which is likely to be experienced by the medium in operation. The medium is incorporated on or in the structural material constituting the respective shutter, blind or storage element. The type of storage medium and the amount of storage medium employed is dependent upon the heat storage capacity of the medium and the operating conditions to which the medium is likely to be subjected. In Annex 4 is shown by way of example, typical storage media and typical energy storage capacities of storage media, which may be used for storage of solar thermal energy in the temperature range encountered by solar collectors.Each of the storage media in Annex 4 undergoes some type of phase transformation which, as described hereinbefore, may greatly increase the total energy storage capacity of the medium when raised above a particular transformation temperature, and the transformation temperature for each medium in Appendix 4 is shown.

The energy storage medium used in the present invention can be a mixture of two salts, the mixture having reciprocal salt pairs as herein before defined, a hydrated salt, an organic compound, a salt solution or a mixture of salt solutions.

It will be seen that energy storage media comprising reciprocal salt pairs have substantial values of energy storage capacity compared with other storage media.

In accordance with the present invention, energy storage media employed are preferably those, such as mixtures of reciprocal pairs, which have substantial values of energy storage capacity.

According to the present invention, degradation of the storage medium upon repeated thermal cycling, as identified hereinbefore, is substantially eliminated due to the incorporation of the storage medium in a member in a large number of small voids, pores or cellular cavities, these being provided by the structure of the member. The presence of the medium in small volumes in this way substantially reduces the possibility of segregation phenomena and also substantially prevents the loss of water of crystallization of the medium due to the fact that each individual void, pore or cellular cavity is sealed by a surface of the member. This arrangement not only substantially eliminates problems due to degradation of the medium, but also provides a very large surface area to the storage medium in the member, thus ensuring efficient heat transfer between individual volumes of the storage medium in the member.

Examples of preferred arrangements for the storage medium in the member and of materials for the member according to the present invention are set forth hereinbelow.

The storage medium may for example be incorporated between aluminium sheets which have a honeycomb structure thereinbetween, thereby defining a plurality of closely adjacent cavities between the sheets. The aluminium may, if required, be coated with a resin which protects the aluminium from corrosion by the storage medium.

Alternatively, aramid paper may be used instead of aluminium sheets.

Alternatively, a honeycomb sandwich structure having hexagonal cellular units may be employed for incorporation of the storage medium.

Alternatively, thermoformed organic polymer sheets composed of, for example, polypropylene or polyethylene may be employed for incorporation of the storage medium, the storage medium being present in small volume "blisters" between two layers of the plastic sheets.

To provide improved thermal efficiency of the storage medium arrangement in the member according to preferred embodiments of the present invention, the surface of the member which is exposed to solar radiation during absorption and storage of solar energy is coated with a paint which enhances energy absorption, whereas the opposite surface of the member is composed of or covered with a sheet of an organic polymer having good thermal insulative properties so as to enhance the thermal insulation of that surface of the member so as to reduce heat loss from the building through the member during the night.

Figures 1 a and 1 b show an example of a thermoformed organic polymer sheet 1 for incorporation of the storage medium. The sheet 1 has, disposed on one of its surfaces in a closed-packed configuration, a number of hollow hemispheres 2, as shown. Preferably, the hemispheres 2 are formed in a second single polymer sheet 3, and when sheets 1 and 3 are placed together, sealed individual hemispheres 2 are present at the surface of the sheet 1. The storage medium 4 is incorporated into each hemisphere 2. The side of sheet 1 having increased surface area due to the presence of hemispheres 2 of its surface is the side which is exposed to solar radiation.

The storage medium 4 may, in another embodiment of the present invention, be contained in cellular units in a honeycomb structure.

In these and other arrangements for the incorporation of the storage medium 4 into a member in a number of individual small volume units, the volume of each unit and the overall arrangement of the units for the storage medium 4 is selected so as to substantially prevent degradation of the storage medium 4 and to ensure good thermal exchange between the units.

Figure 2 shows an arrangement for a window blind according to an embodiment of the present invention.

A window blind 10 comprises laths 11 which can be arranged vertically in a window, each of which laths 11 is rotatable about its longitudinal axis, as shown.

Preferably, rotation of laths 11 occurs simultaneously and laths 11 are rotatable about 360". Each lath 11 comprises a member 12 on a surface of which member 12 is disposed a number of individual units 13 as shown, each of which units 13 contains a storage medium 4 for the storage of solar thermal energy.

As shown in Figures 2a, 2b and 2c, the individual units 13 disposed at the surface of member 12 may be of varying shape. The storage medium 4 is disposed in the enclosed volume 14, 15 or 16 respectively between the surface of member 12 and the surface 17, 18 or 19 respectively, of the unit 13. The volume of each unit 13 is such that degradation of the storage medium 4 does not substantially occur. Preferably, the plane surface of each member 12 is covered by an insulative layer 20.

In Figure 3, the laths 11 of the window blind 10 are shown in a position such that they collect and store solar energy during daylight hours. The laths 11 are rotated such that the external surfaces of the units 13 containing the storage medium 4, which units 13 are disposed on a surface of each lath 11, are substantially facing the incident solar radiation such that optimal solar energy absorption occurs. In such a position, the storage medium 4 in each unit 13 collects and stores solar thermal energy.

In Figure 2, the laths 11 of window blind 10 have been rotated such that the surfaces of the units 13 face into the building at a period when there is no sunlight. The thermal energy in each unit 13 is discharged from each unit 13 into the building.

Figure 4 shows a folding shutter according to an embodiment of the present invention. The shutter 30 consists of a number of slats 31, which slats 31 are preferably rectangular in shape and arranged horizontally as shown with each slat 31 being hinged to an adjacent slat 31 so as to allow free rotational movement between adjacent slats 31 about an axis disposed longitudinal of and between the slats 31. The surface 32 of each slat 31, which surface 32 faces externally of the building, preferably has units 13 with storage medium 4 incorporated into each unit 13, with the arrangement of the units 13 being similar to that shown in Figure 2.

The shutter 30 may, as shown, be rolled up into or rolled out of a cabinet 33 by way of for example manual rotation of handle 34. The slats 31 are rotated about a cylindrical member 35, the longitudinal axis of which cylindrical member 35 is parallel to the longitudinal axis of slats 31. The arrangement is such that during the hours of sunlight, slats 31 of shutter 30 are rolled down out of cabinet 33 in order that the storage medium 4 incorporated into the slats 31 absorbs and stores solar thermal energy, as shown. During the hours of darkness, shutter 30 is rolled up into cabinet 33, such that thermal energy is discharged from shutter 30 inside cabinet 33, which caninet 33 acts as a heater.Preferably the arrangement is such that shutter 30 may be inclined at an angle which angle may be variable to the side of the building so as to give optimal efficiency for solar energy absorption of the shutter 30.

It will be seen that during the hours of sunlight, shutter 30 acts as a conventional shutter and restricts the entry of sunlight into the building.

Figures 5a, 5b, 5e and 5d show a shutter 40 according to a further embodiment of the present invention.

Shutter 40 is of a shape such that it fits closely into a window recess. As shown in Figure 5a one surface 41 of shutter 40 appears similar to that of a conventional shutter, and surface 41 is intended to face externally of the building when the shutter 40 is closed so as to cover the window during the hours of darkness. Shutter 40 is rotatable, when arranged on the building, between pins 42,43 about a vertical axis longitudinal to and along one vertical side of shutter 40.

As shown in Figure 5b, a second surface 45 of shutter 40 has disposed, on a rectangular area inside that of shutter 40 an array 4a of individual slats 46. The slats 46 have an external surface 47 beneath which surface 47 is incorporated a storage medium 4, each slat 46 being associated with a particular volume of storage medium 4 sealed beneath its respective surface 47, the arrangement being such that incident solar radiation on slats 47 causes the storage medium 4 in slats 47 to absorb and store solar thermal energy. The array 49 of slats 46 can be rotated about a horizontal axis 48 as shown in Figure Sc such that inclination of the array 49 to the vertical can be selected so as to optimize the rate of solar energy absorption by the storage medium 4. A member 51 may be employed to retain array 49 at a particular angle of inclination.The array 49 can also be rotated about a vertical axis 50, as shown in Figure 5d, similarly for optimization of the rate of solar energy absorption.

Figure 6 shows a storage element arrangement in a building according to a further embodiment of the present invention. The storage element arrangement 60 is preferably arranged beneath a window 59 of the building and consists of a number of slats 61, which slats 61 are preferably rectangular in shape and are arranged horizontally as shown, with each slat 61 being hinged to an adjacent slat 61 so as to allow free rotational movement between adjacent slats 61 about an axis disposed longitudinal of and between the slats 61.

The array of slats 61 may be rotated through an angle of 1800, as shown in Figure 6, by rotation of cylindrical member 62, against which cylindrical member 62 a portion of the array of slats 61 is disposed by way of gravitation force as shown. The arrangement can be such that it is ensured that a portion of the array of slats 61 is disposed against cylindrical member 62 by a force other than gravitational force. Rotation of the array of slats 61 causes a surface 63 of the array of slats 61 to move from a position at which surface 63 faces internally of the building, as shown, the array of slats 61 being moved across opposite sides of a wall 64 of the building.

The arrangement is such that during hours of sunlight, surface 63 is exposed to solar radiation. Surface 63 has a storage medium 4 incorporated into each slot 61, such that the incidence of solar radiation on surface 63 causes solar thermal energy to be absorbed and stored by the storage medium 4. The arrangement of units 13 containing the storage medium 14 on surface 63 is similar to that shown in Figure 2. During hours of darkness, the array of slats 61 is rotated about 1800 by rotation of cylindrical member 62 such that surface 63 faces internally of the building, and in such a position discharges thermal energy into the building. A grille 65, which does not substantially attenuate thermal radiation is placed between the array of slats 61 and the interior of the building, as shown, so as to protect slats 61 from accidental physical damage.

When the arrangement of the array of slats 61 is such that surface 63 is in a position to absorb solar thermal energy, the array of slats 61 may preferably be moved to a position defined for example, by plane 66, in order to vary the angle of incidence of solar radiation incident on surface 63 such that the rate of energy absorption of the storage medium 4 is optimized.

The embodiment of the present invention illustrated in Figure 6 can be combined with window blinds or shutters according to the other embodiments of the present invention.

In Annex 5 is detailed data showing the average daily amount of solar radiation which was available during the winter months in the town of Ispra (Varese, Northern Italy). The inclinations of the solar collector panels are 90" and 45 , respectively, to the horizontal.

It will be seen from Annex 5 that the average daily amount of energy that can be extracted during the winter months from a collector at an inclination of 40 to the horizontal with an efficiency of 40% and 60% is: 40% efficiency 1.05 kWh/m2 60% efficiency 1.58 kWh/m2 Annex 6 indicates the theoretical heat storage capacity of an aluminium honeycomb structure of the type hereinbefore described according to a preferred embodiment of the present invention. The honeycomb structure has a thickness of 1 cm and has a cell width of 0.5 cm. Examples of the storage capacity of three different energy storage media are shown in Annex 6 for an area of the honeycomb structure of 1 m2 and 6.3m2.

The storage capacity data in Annex 6 refer to one charge - discharge cycle per day.

By way of comparison, Annex 6 also shows the average daily amount of solar energy available in the winter in Ispra (Varese Northern Italy) as shown in Annex 5 from an area of 1 m2 or 6.3m2 of a collecting surface having 60% efficiency, the inclination of the collecting surface being 90" to the horizontal.

It will be seen from Annex 6 that the storage medium consisting of a reciprocal salt pair has a high storage capacity when compared with the average daily amount of solar energy available from a solar collector having 60% efficiency.

Annex 7 shows an estimation of the energy required per day to heat a room having a volume of 60m3 in the winter of Ispra (Varese, Northern Italy).

From the data shown hereinabove, it will be seen that the estimate percentage energy saving for a room 60m3 in volume having a window shutter or a window blind according to an embodiment of the present invention is given by: Storage Capacity of Shutter/Blind x 100, Energy Required for Heating the Room and is found to be: 49% when Glauber's Salt is employed as the storage medium; 30% when paraffin is employed as the storage medium.

It will be seen from the data in Annex 6 and in Annex 7 that using solar energy absorbing, storing and subsequent emitting apparatus according to the present invention can give theoretical energy savings of 30 to 50% for the energy request to heat a room, the value depending upon the area of solar energy absorbing apparatus used and upon the storage medium employed to store thermal energy.

ANNEX 1 Heat transfer coefficient (K)") for some typical window and wall-structures Kin Kcallhour.m2. "C Single-glass window with wooden frame: 5 Single-glass window with metallic frame: 6 Double-glass window with wooden frame: 3 Wall in compact bricks, 0.25m thick: 1.7 Wall in air bricks 0.25m thick: 1.3 ANNEX 2 Heat losses calculated for a window of 6.3m2 surface and for three different K-values assuming an average temperature difference of 12.so between the inside and the outside wall.

K Kcalihour Kcaliday kWh/day 5 393 9450 10.9 6 472 11340 13.2 3 236 5670 6.6 ") K gives the number of kcal per hour and per m2 surface transmitted through a wall, when the temperature difference between the inner side and the outer side of the wall is 1"C.

ANNEX 3 Storage capacity of some typical storage media measured over a temperature interval of 40"C between the initial and the final state of the storage system: Energy Storage capacity Energy Storage Medium in kcalldm3 in kWhidm3 Water 40 0.046 Glauber's salt (Na2SO4.10H20); 115 0.133 Paraffin 70 0.081 Reciprocal salt pair (Ba(OH)28H2O + 2KN03) 190 0.221 ") 1 kWH - 860 kcal ANNEX 4 Some known chemical- and latent heat storage media operating within the temperature range of usual solar collectors.

Energy Energy Storage Medium Storage capacity Transformation Temperature Kcalldm ) C Reciprocalsaltpairs: Ba(OH)2.8H2O + 2KNO3 190 65 2CsBr+(NH4)2SO4 350 49 2LiNO3.3H2O + (NH4)2S04 287 28 Salt hydrates Na2S203.5H20 110 48 Na2SO4.10H2O (Glauber'ssalt) 115 32 Organic compounds Paraffins 70 45-60 ") 860 Kcal 1 kWh ANNEX 5 90 Inclination Month whim2 November1980 1,626 December 1980 2,672 January 1981 3,532 February 1981 2,817 March 1981 2,596 Daily amount averaged over the winter 2,648 45t Inclination Month kWh/m November1980 1,522 December 1980 2,502 January 1981 3,363 February 1981 3,166 March 1981 3,422 Daily amount averaged over the winter 2,795 ANNEX 6 Storage medium Storage capacity in kWh Solar energy available in kWh" lm2 6.3m2 lm2 6.3m2 Reciprocal salt pair Ba(OH)2.8H2O + 2KN03 2.38 14.99 1.58 kWh/day 9.95 kWh/day Glauber's salt Na2SO4.10H2O 1.44 9.07 Paraffin 0.88 5.54 ANNEX 7 Estimation of the energy required per day to heat an office of standard dimensions (=60 m3) in the winter-climate of Northern Italy.

Volume: 5 x 4 x 3 m: 60m3 Average temperature difference AT: 12.5"C Heating time: 12 hours/day Combustion factor: 0.83 Distribution system-efficiency: 0.90 Overall dispersion coefficient: 1.3 kcal/h.m3. "C Estimated 60 X 12.5 X 12 X 1.3 Energy = 0.83 x 0.90 = 15662 kcal = 18.21 kWh required per day

Claims

1. A thermal storage panel capable of storing thermal energy in response to solar irradiation and including as a storage medium a substance which undergoes a reversible chemical reaction or a reversible phase transformation at a temperature substantially above room temperature.

2. A panel as claimed in Claim 1 wherein the storage medium comprises a mixture of two salts, the mixture having reciprocal salt pairs as hereinbefore defined.

3. A panel as claimed in Claim 1 wherein the storage medium comprises a hydrated salt.

4. A panel as claimed in Claim 1 wherein the storage medium comprises an organic compound.

5. A panel as claimed in Claim 1 wherein the storage medium comprises a salt solution or a mixture of salt solutions.

6. A panel as claimed in any preceding claim wherein the storage medium is contained in a plurality of individual compartments, the volume of each compartment being substantially less than the volume of storage medium which is associated with the panel.

7. A thermal energy storage panel comprising a supporting member and a thermoplastic sheet, the sheet being formed with a multiplicity of blisters containing an energy storage medium, which energy storage medium undergoes a reversible chemical reaction or a reversible phase transformation at a temperature substantially above room temperature.

8. Apparatus for absorption storage and subsequent emission into a building of solar thermal energy, the apparatus comprising one or more members arranged at a side of the building, each member including an energy storage medium, which energy storage medium undergoes a reversible chemical reaction or a reversible phase transformation at a temperature substantially above room temperature and is incorporated in the member, and being movable from a first position at which first position the member can absorb and store incident solar thermal energy, to a second position, at which second position the member can emit the stored thermal energy into the building.

9. Apparatus as claimed in Claim 8 wherein a surface of one side of each member incorporates the energy storage medium, the medium being disposed at the surface of the member, which surface is exposed to solar radiation when the member is in the first position.

10. Apparatus as claimed in Claim 9 wherein each member is arranged so as to be vertical and to be rotatable about a longitudinal axis of the member, between the first position and the second position.

11. Apparatus as claimed in Claim 10 wherein the members are arranged to be simultaneously rotatable about 360 , the distance between the said longitudinal axis of adjacent members being substantially equal to the width of each member.

12. Apparatus as claimed in Claim 11 wherein each member is arranged such that the longitudinal axis of each member is horizontal, with the members being successively adjacent to each other and the longitudinal edges of adjacent members being closely disposed together, each member being rotatable about an axis, which axis is longitudinal of the member and is disposed between adjacent members, so as to form a flexible array.

13. Apparatus as claimed in Claim 12 wherein in the first position a substantial number of the members are coplanar and are arranged to be substantially vertical or to be at a particular angle to the vertical.

14. Apparatus as claimed in Claim 13 wherein in the second position the members of the shutter are arranged so as to be capable of emitting radiation into the building and the shutter is moved from the first position to the second position by rotation of a cylindrical member about a longitudinal axis of the cylindrical member, which longitudinal axis is parallel to the longitudinal axis of each member, the member at an edge of the shutter being attached to the cylindrical member such that rotation of the cylindrical member causes the shutter to be disposed circumferentially of the cylindrical member.

15. Apparatus as claimed in Claim 9 wherein the members are arranged horizontally in an array, the array being movable from the first position to the second position, at which second position the array covers a portion of a window, by rotation about a vertical axis, which vertical axis is positioned longitudinal to and at an edge of the array.

16. Apparatus as claimed in Claim 15 wherein the array is rotatable about a horizontal axis, which horizontal axis is disposed at an upper edge of the array.

17. Apparatus as claimed in Claim 9 wherein a number of the members are arranged with the members being successively adjacent to each other such that a longitudinal axis of each member is horizontal and adjacent members are joined at and are rotatable about a longitudinal axis disposed between adjacent edges of adjacent members so as to form a flexible array.

18. Apparatus as claimed in Claim 17 wherein a substantial portion of the array is movable from the first position to the second position by rotation of the surface of the said one side of each member about 1800 from a position external of to a position internal of a wall of the building by rotation of a second cylindrical member, which second cylindrical member is positioned in the plane of the wall, against a portion of which cylindrical member is closely disposed a portion of the surface of the side of the array, which side is opposite to the said one side of each member.

19. Apparatus as claimed in any of Claims 8 to 18 wherein a surface of each member, which surface is not exposed to incident solar radiation, has an insulative layer disposed against or incorporated into the surface.

20. A method for the absorption, storage and subsequent emission into a building of solar thermal energy incorporating the use of apparatus as claimed in any preceding claim.

21. Apparatus for the absorption, storage and subsequent emission into a building of solar thermal energy substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.