GB2477765A

GB2477765A - Solar energy collecting window sunshade

Info

Publication number: GB2477765A
Application number: GB1002339A
Authority: GB
Inventors: John Nicholas Grazebrook
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-02-12
Filing date: 2010-02-12
Publication date: 2011-08-17
Also published as: GB201002339D0

Abstract

The shade 10 comprises a number of spaced apart louvers 12, each supporting an array of photovoltaic cells, which extend between a pair of supporting arms 13, the supporting arms extending the shade away from a building. The louvers may be fixed, typically at an angle of 20° to the horizontal, or be partially rotatable to follow the motion of the sun in the sky. The louver arrangement allows sunlight transmission between the louvers. Also claimed is a modular system for creating different sized sunshades.

Description

A Solar Energy Collecting Window Shade

Field

This invention relates to window shades of the type mounted on the exterior of a building to provide shade for windows during periods of high solar intensity.

Background of the Invention

Modern commercial and residential buildings are now being designed with increased emphasis on carbon emissions whilst maintaining thermal comfort for occupants and/or temperature sensitive equipment. Increased glazing areas are used to maximise winter solar heating and enhancing architectural impact and occupant well being. Modern glazing materials have enabled the use of glass without compromising building insulation. A problem with buildings having relatively large areas of glass is that when subject to high solar intensity the incident solar energy will heat the interior of the building and therefor require the use of air conditioning to maintain the internal temperature at a comfortable level. If the amount of solar energy and solar glare entering the building can be reduced then the carbon footprint can be reduced and occupant comfort maintained.

A known method of mitigating the effects of radiant heat loss in cold climates is the use of windows having low emissivity (low e) for preserving the heat in homes, offices, automobiles and other heated environments and for mitigating escape of heat to the cold exterior via the window glass. Low e windows are also useful in hot climates for rejecting thermal energy radiation from the exterior and for minimizing heat transfer via the windows to help maintain a cdol interior. Window glass itself may be treated and/or coated to provide low emissivity characteristics, see for example US685241 9.

The interiors of windows may be provided with blinds or shutters to keep out the solar energy. Yet another method is to provide window shades on the exterior of the building either above or in front of the window so that the window is shaded from full sunlight. Retractable canvas window canopies are well known and Iouvred sun shades comprising spaced apart lamellae arranged between fixed supports have been mounted above the window and in front of the window glazing. Such shades are available from Levolux Ltd. in the UK. It is also known to provide a fixed canopy made from an opaque material over a window.

It is also known from DE202005001 160 (Ui) that the horizontal slats of venetian blinds may be provided with photovoltaic cells for generating electricity. A similar arrangement is shown in EP0593201A1 in which solar cells may be mounted on pivotable horizontal louvres arranged in a vertical array externally of a glazing. A problem with this arrangement is that the output from the photovoltaic cells is small and unpredictable depending upon the chosen orientation of the slats and chosen percentage of the window obscured by the blind.

Vrgrir modern buildings, the buildings' frequently need to meet bdk b4issibn standards and or provide a proportion of theirpredicted energy consumidh hewable sources which means That both the degree of shade provided by window shades and any benefit derived from solar power must be predictable. The shading effect can be accuratey predicted for fixed shades arranged externally of the building above the window.

It is also known for fixed window canopies to be provided with a photovoltaic panels for producing electricity from solar energy. Such canopies are used extensively in the south of France and are available from Sunvie SA and Suneol SA in France. However such shades will in winter block out needed daylight which will be disadvantageous especially more northern latitudes.

Object of the Invention The present invention seeks to alleviate some of the above problems

Statements of Invention

According to a first aspect of the present invention there is provided an externally mountable sunshade for use on the exterior of a building above a window therein, the sunshade comprising a plurality of spaced apart Jouvres extending between a pair of support arms used for cantilevering the shade out from the building, each louvre supporting a linear array of photovoltaic cells which provide electrical energy which is connectable to an electrical storage system, for example the buildings main electrical distribution system or an occupant local electrical system.

Preferably the sun shade is substantially planar and the louvres are supported by the arms so as to be cantilevered substantially horizontally outwardly of the building. The louvres may be fixed in position relative to the support arms, preferably at a suitable angle for maximising the exposure of the photovoltaic cells to the sunlight whilst minimising shading of adjacent louvres, and typically at about 200 of arc to the horizontal. In an alternative arrangement the louvers may be rotated to follow a limited movement of the sun through the sky.

The spaced apart louvers when in alignment in a horizontal plane may occupy 65-75% of the total area of the sunshade allowing for passage of a limited amount of sunlight on each side of the louvers. The sun shade may comprise standard length louvres supporting a linear array of ten pv cells with between 4-6 louvres per sun shade.

A second aspect of the present invention provided a building having windows with sun shades according to the present invention provided above at least some of the windows. The sun shades on the building may have different widths and br lengths above the windows, and preferably the different widths sun shades are formed from standard width modules assembled together which may have the same numbers of standard louvers or different numbers of louvres as is required.

Desciption of the Drawincis The present invention will be described by way of example and with reference to the accompanying drawings in which: Fig. 1 is a plan view of a sun shade according to the present invention, Fig. 2 is a front elevation of the sun shade in Fig. 1, Fig. 3 is a side elevation of the sun shade in Fig. 1, Figs 4 & 5 are side views of alternative sun shades, Fig. 6 is front elevation of a building having sun shades according to the present invention mounted thereon, and Fig. 7 is side elevation of the building shown in Fig. 6.

Detailed Description of the present Invention

With reference to Figs 1 to 3, there is shown a sun shade 10 which in use is mounted on the wall 11 of a building B (see Figs 6 & 7) above a glazed window aperture W. The sun shade 10 comprises a plurality of Iouvres 12, in this example four, which are substantially flat but which may have curved upper and lower surfaces to stiffen the louvres 12 lengthwise. The Iouvres 12 are mounted on a pair of spaced apart support arms 13 and may be rotationally fixed to said arms so as to be at a desired angle to the horizontal when the sun shade is mounted substantially horizontally on the wall 11, as shown. The preferred angle is about 20° of arc in latitudes >50 ° but other angles may be selected as is desired depending upon location. The angle is selected so that adjacent louvres are not shaded by a neighbouring louver between March-September.

The upper surface of each louver 12 has a longitudinal array of photovoltaic (pv) cells 15 mounted thereon, preferably by means of a suitable adhesive.

Alternatively, the pv cells may be mounted on a support to form a sub-assembly fixed to the respective louvre using fixtures, brackets, or other suitable means. In the present example shown in Figs. 1-3, the sun shade comprises four louvres each of which is approximately 1660mm in length L and 220mm in width w supported between support arms 13 spaced apart by about 1800mm having a nominal length of about 1210mm. The pitch of the louvres as about 300mm so that the obscured area within the shade is about 73% of the area of the shade. Each louver 12 has ten pv cells 15 arranged in series forming a pv module on the respective louver. The pv cells 15 are preferably 156 x 156 high performance mono crystalline cells and the ten cell pv module has a nominal output of 4OWp so that the four louver sun shade provides a peak output of l6OWp (Energy and carbon emission calculations have been completed using DCLG approved SAP 2006 software and are for the UK).

The annual generation 125.O4kWhr and the carbon saved 0.422 (2006 emission factor) = 52.7kgCO2 and (carbon saved @ 0.59, new 2010 emission factor = 73.77kgC02) * 7 In an alternative arrangement, the Iouvres 12 may be rotatably mounted in the support arms 13 so as to follow the movement of the sun through the sky.

The pitch of the louvres 12 ensures that there is a gap of approximately 90 mm between neighbouring louvres allowing some natural light to pass through the shade 10. This allows some natural daylight to enter the window which may be important on dull overcast days and during winter months.

Referring now to Fig. 4, there is shown five louver 12 shade 110 having support arms 113 approximately 1470mm in length. The support arms 113 are spaced apart by the approximately the same distance as the supports arms 13 in the sun shade 10. The peak output from the sun shade will be about 200Wp and the annual generation = 156.3OkWhr with carbon saved @ 0.422 (2006 emission factor) = 66.OkgCO2 and (carbon saved @ 0.59, new 2010 emission factor) = 92.2kgCO2 Fig. 5 shows a six louvre sun shade 210 having support arms 213 approximately 1770mm in length. The support arms 213 are spaced apart by the approximately the same distance as the supports arms 13 in the sun shade 10. The peak output from the sun shade will be about 24OWp and the annual generation = 187.56 kWhr with carbon saved @ 0.422 (2006 emission factor) = 79.15 kgCO2 and (carbon saved @ 0.59, new 2010 emission factor) = 110.7 kgCO2 With reference also to Figures 6 and 7, there is shown a building B with a plurality of sun shades mounted on its south facing elevation above windows w. Depending upon the requirements for electrical generation the sun shades may be selected from the three different shades 10, 110 or 210. The sun shades 10,110, 210 may be provided in standard width modules where the louvre length and spacing between the support arms 13, 113, 213 is standardized and based on a louvre 12 supporting a ten pv cell array as shown above. The building B shown is provided with a single modular sun shade I OA above the single windows and two adjacent modular shades 10 B above the pairs of windows. The two sun shade modules may be assembled together or mounted in close proximity on the wall 11. In order to maximize electricity generation the top floor windows are provided with a plurality of modular shades 1 OC, in this example sixteen modules but other numbers may be selected as is required, arranged side by side across the whole front façade of the building. Again the modules may be assembled together or mounted on the building in close proximity one with another.

The electrical energy from the different sun shades is discharged through wires or other suitable electrically conductive paths to an electrical storage device, and/or a local electrical distribution system which may in large buildings be connected to the national grid via a suitable meter.

Claims

Clairhs 1. An externally mountable sunshade for use on the exterior of a building above a window therein, the sunshade comprising a plurality of spaced apart louvres extending between a pair of support arms used for cantilevering the shade outwardly from the building, each louver supporting a linear array of photovoltaic cells which provide electrical energy which is connectable to a suitable electrical system.
2. A sun shade as claimed in Claim 1, whereon the sun shade is substantially planar and the louvres are supported by the arms so as to be cantilevered substantially horizontally outwardly of the building.
3. A sun shade as claimed in Claim 1 or Claim 2 wherein the louvres are fixed in position relative to the support arms.
4. A sun shade as claimed in Claim 3 wherein the louvres are fixed at a suitable angle for maximising the exposure of the photovoltaic cells to the sunlight, and typically at about 200 of arc to the horizontal.5. A sun shade as claimed in Claim 1 or Claim 2 wherein In the louvers may be rotated to follow a limited movement of the sun through the sky.
5. A sun shade as claimed in any one of Claims 1 to 4, wherein the spaced apart louvers when in alignment in a horizontal plane obscure between 65- 75%'of the total area of the sunshade allowing for passage of sunlight on each side of the louvres.
6. A sun shade as claimed in any one of Claims 1 to 5, wherein the sun shade comprising standard length louvres supporting a linear array of ten pv cells, there being between 4-6 louvres per sun shade.
7. An externally mountable sunshade for use on the exterior of a building above a window therein and which is substantially as described herein with reference to Figs 1-3, 4 & 5 of the drawings.
8. A building having windows with sun shades as claimed in any one of Claims 1 to 7, provided above at least some of the windows.
9. A building as claimed in any Claim 8, wherein the sun shades on the building may have different widths and br lengths above the windows, and preferably the different widths sun shades are formed from standard width modules which may have the same numbers of standard louvers or different numbers of louvres as is required.
10. A building as claimed in Claim 9 wherein the standard width sun shade modules are assembled together. -II