FIELD

The present invention is directed to solutions for improving the thermal properties of transparent substrates, such as windows. In particular, the present invention relates to a device that can vary the transmission of radiation through a windowpane.

BACKGROUND

Climate change and carbon emissions are pressing issues now and will continue to be so for the foreseeable future. At present over 40% of global carbon emissions are from buildings, such as our homes and workplaces, with the big driver being the difficulty to regulate the temperature due to unwanted heat gain and unwanted heat loss depending on the time of the year. For instance, it is estimated that 40% of a typical buildings cooling costs may be due to solar heat gain through windows. There is a clear need for innovation and disruption in the glazing industry if our current buildings are to meet zero-net- carbon standards.

The most dominant technology on the market aimed at reducing solar heat gain and loss through windows is passive low E-Glass. At its most simple this involves placing a thin transparent fdm on a pane of glass to block the transfer of heat in or out of the building. The critical element of this technology is that it is passive and cannot be altered as weather conditions/temperatures change.

There is the need for improved glazing solutions for aiding in improving their thermal properties to maintain our buildings internal temperatures reducing unwanted heat transfer through windows.

SUMMARY OF INVENTION

According to a first aspect there is provided a window system for controlling the transmission of thermal radiation from an external source of electromagnetic radiation, the system comprising: a windowpane comprising a transparent substrate; a first electrode layer and a second electrode layer, located adjacent the windowpane, each of the electrode layers comprising a plurality of electrodes; a carrier material, located between the first electrode layer and the second electrode layer, the carrier material comprising a plurality of molecules that are orientable in the presence of an electric field; and a processor configured to: determine a position of an external source of electromagnetic radiation, where electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane; calculate based on the determined position a direction in which the electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane; determine, based on the calculated direction, an electrode in the first electrode layer and an electrode in the second electrode layer to apply a potential difference between so as to generate an electric field in the carrier material and thereby orientate molecules of the plurality of molecules located between the electrode in the first electrode layer and the electrode in the second electrode layer perpendicular to the direction in which the electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane so as to alter the transmission of electromagnetic radiation through the window system; and apply a potential difference between the determined electrode in the first electrode layer and the determined electrode in the second electrode layer.

In this way, the window system can detect the direction of the external source of radiation and control the transmission properties of the window to prevent radiation specifically incident along the direction from the external source of radiation. This can have the effect of blocking external radiation (e.g., light) directly from this dominant external source of radiation (such as the sun) whilst allowing the passage of radiation from other directions. Advantageously, this means that most of the window can remain transparent as radiation from other sources along other directions can pass through the window without significant attenuation, whereas radiation directly from the external source is blocked. To an observer on the opposite side of the window system to the external source of radiation this may have the appearance of a dark area over their view of the external source of radiation, whilst the remaining view through the windowpane being unobstructed.

The altering is preferably to reduce the transmission of electromagnetic radiation through the window system.

Located adjacent the windowpane does not intend to mean in direct contact with. But may mean next to, near to, located on, or attached to. The molecules have the property that they are orientable in the presence of an electric field. In addition, the molecules have the further property that they attenuate the passage of electromagnetic radiation when arranged in one direction and allow the passage of electromagnetic radiation in another direction. For instance, they may attenuate the passage of electromagnetic radiation when arranged perpendicular to the incident electromagnetic radiation, whereas they may permit the passage of electromagnetic radiation when arranged parallel to the incident electromagnetic radiation. Each molecule may have an asymmetric shape having a major axis and a minor axis. By orientating the molecules perpendicular to the direction in which the electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane the major axis may be perpendicular to the direction in which the electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane .

Further advantageously, as each electrode layer has a plurality of electrodes it is possible to accurately control the direction of the orientation of the molecules in the carrier material dependent on which electrodes in each layer a voltage is applied to. This can ensure that the molecules can be orientated as desired over a wide range of angles to alter the transmission of external radiation having a wide range of incident directions.

The electrodes of the first electrode layer may be independently controllable in that a voltage applied to one electrode of the first electrode layer need not necessarily be applied to the other electrodes of the first electrode layer. Likewise, the electrodes of the second electrodes layer may be independently controllable in that a voltage applied to one electrode of the second electrode layer need not necessarily be applied to the other electrodes of the second electrode layer. The electrodes of the first electrode layer may also be independently controllable to the electrodes of the second electrode layer.

As such, an electric potential can be applied to each of the electrodes independently of each other. This allows a potential difference to be applied to various pairs of electrodes.

In some arrangements, only the molecules located (in a region) between the determined electrode of the first plurality of electrodes, and the determined electrode of the second plurality of electrodes, between which the potential difference is applied, may be orientated by the potential difference. Molecules located at other regions may not be orientated by this electric field as the magnitude of the electric field generated by the potential difference in these regions may be too small to have an effect. The position of the external source of electromagnetic radiation may be the position of the external source of radiation relative to the window system. For instance, relative to the windowpane. The position may be for instance the azimuth and/or elevation of the external source of radiation. Calculating the direction in which the electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane may be calculating its azimuthal component, and/or calculating its elevation component.

The direction in which the electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane is its propagation direction. The propagation direction may have azimuthal and/or elevation components. In some arrangements, orientating the molecules of the plurality of molecules located between the electrode in the first electrode layer and the electrode in the second electrode layer may involve orientating the molecules perpendicular to the direction in which the elevation component of the electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane. Alternatively, it may be perpendicular to the azimuthal component (in the case of third and fourth electrode layers).

Reducing the transmission may include increasing the absorption and/or reflection of electromagnetic radiation through the device. Transmission of electromagnetic radiation may be transmission of visible, UV, IR, and/or other types of radiation. Each of these processes may be responsible for the transfer of heat through the window.

Preferably, the windowpane may have a major surface, the major surface defining a plane, and wherein perpendicular to a direction in which radiation from the external source of electromagnetic radiation is incident on the windowpane is in a direction out of the plane. Advantageously, this allows the orientation of the molecules to be changed such that they can follow the position of the external source of radiation. If the orientation was only in the plane of the windowpane, then this may not be achievable without requiring further polarisation filters and the use of polarisation filters will block light across the whole window aperture but without the effect of directionality achieved by the present aspect. The plane may be defined by the x-axis and the y-axes and a direction out of the plane may be in the x-z plane and/or y-z plane.

The major surface may be the surface through which the electromagnetic radiation from the external source of electromagnetic radiation is incident, i.e., the major surface is configured to receive the radiation from the external source. In other words, the major surface may be the outer facing surface of the windowpane. Each electrode layer may be located in a plane parallel to the major surface.

Preferably, the determined electrode in the first electrode layer, and the electrode in the second electrode layer, may be positioned at a first position along a first axis, and a second position along the first axis respectively, wherein the molecules of the plurality of molecules are configured to orientate along a direction defined between the first position and the second position.

The first position may be a different position along the first axis to the second position. In this way, the transmission of radiation through the device can be varied by selecting an appropriate difference in position between the electrode in the first electrode layer and the electrode in the second electrode layer. For instance, by selecting electrodes that have a larger difference in position the molecule orientation will differ to selecting electrodes that have a smaller difference in position. In other arrangements, the first position may be the same as the second position.

For instance, the molecules may orientate along the electric field lines caused by the potential difference between the electrodes. In other arrangements the molecules may orientate in a direction that is perpendicular to the direction of the electric field, for instance perpendicular to the electric field lines. The orientation of the molecules may in some instances not change in response to application of a particular electric field if the molecules are already orientated with respect to the electric field. Subsequently generating an electric field in a different direction may cause a further re-orientation of the molecules.

The window system may further comprise a third electrode layer and a fourth electrode layer, located adjacent the windowpane, each of the third and fourth electrode layers comprising a plurality of electrodes, wherein through applying voltage to electrodes of the first, second, third and fourth electrode layers, the plurality of molecules are rotatable over multiple axes to orientate the molecules perpendicular to the direction in which the electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane. In this way, the third and fourth plurality of electrodes can act to control the orientation of the molecules in a further dimension providing a further degree of control. Thus, the molecules are rotatable in multiple directions, for instance allowing rotation in three dimensions. An external source of electromagnetic radiation, such as the suns, may emit electromagnetic radiation that is not polarised so may have multiple components to it. Therefore, by being able to orientate the molecules about a range of axes the radiation can be efficiency blocked.

For instance, the first and second electrode layers may control the orientation of the molecules over elevation angles, and the third and fourth electrode layers may control the orientation of the molecules over azimuth angles. Radiation from an external source may have polarisation in a number of different axes. For instance, polarisation of transverse electromagnetic (TEM) waves is always perpendicular to its propagation direction i.e. the plane of polarisation of the incoming light will be perpendicular to the direction of incidence of the light. The first and second electrode layers may act to prevent radiation that is polarised in an axis and the third and fourth electrode layers may act to prevent radiation that is polarised in a perpendicular axis. This enables radiation having any polarisation to be blocked as minimum level of transmission can be reached when all polarisations within the plane can be rejected (through absorption and/or reflection). The first and second electrode layers operate together in the same way as the third and fourth electrode layers, albeit by controlling the orientation of molecules in an orthogonal direction. The electric field generated, and the resulting orientation of the molecules, may be influenced by a combination of the electric field generated by both the first and second and third and fourth electrode layers. In other arrangements, potential difference may be applied between the first and second electrode layers, and at a subsequent point in time potential difference may be applied to the third and fourth electrode layers.

Alternatively, the window system may further comprising a third electrode layer and a fourth electrode layer, located adjacent the windowpane, each of the third and fourth electrode layers comprising a plurality of electrodes; wherein the carrier material is a first layer of carrier material, and the system further comprises a second layer of carrier material, wherein the second layer of carrier material is located between the third electrode layer and the fourth electrode layer, the second layer of carrier material comprising a plurality of molecules that are orientable in the presence of an electric field; wherein the processor is further configured to: determine, based on the calculated direction, an electrode in the third electrode layer and an electrode in the fourth electrode layer to apply a potential difference between so as to generate an electric field in the second layer of carrier material and thereby orientate molecules of the plurality of molecules located between the electrode in the third electrode layer and the electrode in the fourth electrode layer perpendicular to the direction in which the electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane so as to reduce the transmission of electromagnetic radiation through the window system; and apply a potential difference between the determined electrode in the third electrode layer and the determined electrode in the fourth electrode layer.

In this way, the third and fourth plurality of electrodes can act to control the orientation of the molecules in the second carrier layer in a further dimension compared to the molecules in the first carrier layer. As outlined above, an external source of electromagnetic radiation, such as the sun, may emit electromagnetic radiation that is not polarised so may have multiple components to it. Therefore, by being able to orientate the molecules about a range of axes the radiation can be efficiency blocked.

For instance, as outline above the first and second electrode layers may control the orientation of the molecules in the first carrier layer over elevation angles, and the third and fourth electrode layers may control the orientation of the molecules in the second carrier layer over azimuth angles. The first and second electrode layers may act to prevent radiation that is polarised in an axis and the third and fourth electrode layers may act to prevent radiation that is polarised in a perpendicular axis. This enables radiation having any polarisation to be blocked. The first and second electrode layers operate together in the same way as the third and fourth electrode layers, albeit by controlling the orientation of molecules in an orthogonal direction.

Preferably, the molecules (located between the electrode in the third electrode layer and the electrode in the fourth electrode layer) may be orientated perpendicular to the orientation of the molecules in the first layer of carrier of material. In other arrangements, instead of or in addition, the window system may comprise a layer of polarising material. The layer of polarising material may be positioned in the same plane as the major surface of the windowpane. The layer of polarising material may be configured to prevent the passage of radiation having a certain polarisation through the window system. This may be instead of having the third and second layer of electrodes.

Preferably, the first electrode layer may be defined by a first axis and a second axis, where the second axis is orthogonal to the first axis, the plurality of electrodes of the first electrode layer spaced apart from each other along the first axis; and the second layer of electrodes may be defined by the first axis and the second axis, the plurality of electrodes of the second electrode layer spaced apart from each other along the first axis, and the second electrode layer spaced apart from the first electrode layer along an axis perpendicular to the first and second axis.

In this notation the first axis may be the y-axis, and the second axis may be the x-axis. In this notation then the axis perpendicular to the first and second axis may be the z- axis.

Preferably, the molecules orientate along a direction in the presence of the electric field may be between the first axis and the axis perpendicular to the first and second axis, thereby to reduce the transmission of electromagnetic radiation through the device. This may be achieved through applying potential difference to the electrodes of the first and second layer.

Preferably, each of the plurality of electrodes of the third electrode layer may be spaced apart from each other substantially along the second axis; and each of the plurality of electrodes of the fourth electrode layer may be spaced apart from each other substantially along the second axis..

The third electrode layer may be positioned between the first electrode layer and the carrier material, and the fourth electrode layer positioned between the second layer and the carrier material. Preferably, the molecules may orientate along a direction in the presence of the electric field may be between the second axis and the axis perpendicular to the first and second axis, thereby to reduce the transmission of electromagnetic radiation through the device. This may be achieved through applying potential difference to the electrodes of the third and fourth layer.

Preferably the step of determining, based on the calculated direction, an electrode in the first electrode layer and an electrode in the second electrode layer, may comprise the processor being configured to: determine multiple pairs of electrodes, each pair of electrodes comprising an electrode in the first electrode layer and an electrode in the second electrode layer; and sequentially apply a potential difference to each pair of electrodes, so as to orientate the plurality of molecules in the carrier material, located between the electrode in the first electrode layer and the electrode in the second electrode layer in each pair, perpendicular to the direction in which radiation from the external source of electromagnetic radiation is incident on the windowpane.

The multiple pairs of electrodes may be determined so as to orientate all of the plurality of molecules in the carrier material perpendicular to the direction in which radiation from the external source of electromagnetic radiation is incident on the windowpane.

In this way, the molecules across the entire window system can be configured to orientate in the desired direction. Each pair of electrodes contains an electrode in the first layer and an electrode in the second layer. By having a difference in position between the electrode in the first layer and the electrode in the second layer for each pair that is the same the molecules can be caused to orientate in the same direction across the device. This enables control of the molecules in the local area adjacent the electrodes that a voltage has been applied to. In this way, the rates of transmission can be the same across the entire window system. In this arrangement each pair of electrodes may contain a different electrode from the first electrode layer and electrode from the second electrode layer to each other. This can likewise be applied to the third and fourth electrode layers (rather than the first and second electrode layers).

By sequentially switching the electrodes of each pair on and then off (i.e., applying voltage to the electrodes of the pair and then stopping application of the voltage) the molecules can be orientated in a specific orientation between each electrode pair. For instance, by switching a first pair of electrodes on the molecules positioned between the first pair of electrodes will be caused to orientate such that they align along the field lines formed between the first pair of electrodes. Once the potential difference to the first pair of electrodes is switched off the molecules will preferably maintain their orientation. By then switching on a second pair of electrodes, the same effect will be achieved for the molecules positioned between the second pair of electrodes. By switching off it may be meant removing all voltage applied, or simply reducing the voltage.

In some arrangements, the device may permit different rates of transmission of electromagnetic radiation through the device at different regions, depending on the local orientation of the molecules. For instance, different regions of the window system may allow varying transmission of radiation to each other depending on the local orientation of molecules in each region, for instance, by only applying potential difference to pairs of electrodes in certain regions of the window system to alter the properties. Or by having a difference in position between the electrode in the first layer and the electrode in the second layer for each pair being different in different regions.

The window system may further comprise a sensor configured to detect electromagnetic radiation from an external source, wherein the processor is configured to receive a signal from the sensor indicating the position of the external source of electromagnetic radiation. The sensor may be a single sensor. In other arrangements there may be a plurality of sensors. The sensor may be a photosensor capable of detecting electromagnetic radiation. The sensor may be configured to detect radiation over a certain wavelength band, for instance the sensor may detect only visible light. In other arrangements, the sensor may detect radiation over a wide range of the EM spectrum. For instance, it may be capable of detecting visible, IR and UV light. By having multiple sensors different sensors may be configured to detect different wavelength bands to each other. For instance, there may be dedicated IR sensors, dedicated UV sensors and/or dedicated visible sensors. The sensor may be a camera capable of detecting a photo of the external source of radiation from which its position can be determined. In other arrangements, the position of the external source may be determined without the use of a sensor. For instance, the processor may access a database that contains details of the position of the external source at a particular time of day. The window system may further comprise a sensor configured to detect the intensity of electromagnetic radiation from an external source of electromagnetic radiation. The sensor may be any of the sensors discussed above. Advantageously, by having a sensor configured to detect intensity of electromagnetic radiation it can determine whether it is required to activate the molecules in the carrier layer to reduce transmission of electromagnetic radiation through the window. For instance, the processor may be configured to receive a signal from the sensor indicating the intensity of electromagnetic radiation from the external source of electromagnetic radiation and determine whether to apply the potential difference between the determined electrodes based on said intensity. For instance, if the intensity is above a threshold level the processor may decide to apply the potential difference between the determined electrodes, whereas if the intensity is below a threshold level the processor may decide to not apply the potential difference between the determined electrodes. This can be used to maintain the desired thermal temperature inside the building in which the window system is installed.

The window system may further comprise a temperature sensor configured to detect temperature in a region adjacent to the window system. Advantageously, by detecting temperature in a region adjacent to the window system (such as either side of the window system), i.e. the temperature outside and the temperature inside the building on which the window system is installed, the device can be configured to reduce transmission of electromagnetic radiation through the window system based on a comparison with a target inside temperature. For instance, if the temperature inside the building on which the window system is installed is colder than desired, the processor may be configured to not apply a potential difference to the electrodes to cause the molecules to orientate to reduce the passage of electromagnetic radiation. In this way, the building may heat up from allowing the passage of radiation from the external source into the building. Whereas if the temperature inside the building on which the window system is installed is warmer than desired or at the desired temperature, the processor may be configured to apply the potential difference to the electrodes to cause the molecules to orientate to reduce the passage of electromagnetic radiation. In this way, the building will not be heated up through the passage of electromagnetic radiation through the window system. The temperature sensor may be any type of sensor capable of detecting temperature. The molecules are preferably anisotropic molecules. In other words, the molecules are non-spherical and have two axes that are different to each other. For instance, the molecules can be approximated as having a simplified shape having a long axis that is much shorter than their short axis. For instance, they may be rod-shaped. In this way, the molecules have properties that depend on the orientation of the molecule. For instance, along one axis the molecules may permit the passage of radiation, but along a different axis they may not allow the passage of radiation. The molecules may be carbon nanotubes. In other arrangements they may be any type of molecules which are sufficiently absorptive/reflective with respect to the wavelengths of the incoming electromagnetic radiation, and which can be oriented in an external electric (or even magnetic field) field. For instance, this may include long chain organic molecules which exhibit an approximately rod-like outer shape or a shape deviating from a sphere. These can be polarised by an external field and would align the field lines with their long main axis. Their optical properties could be tailored by introducing aromatic antenna complexes into their chains in a similar way to molecules used for organic (Dye- sensitized) solar cells.

Preferably, the molecules may be configured to maintain their orientation once the potential difference has been removed. In this way, the voltage applied to each of the electrodes may be pulsed. Upon application of a pulse of voltage the potential difference between the electrodes may cause the orientation of the molecules to change (if the electric field is in a direction to cause the change) and after the pulse the orientation of the molecules may remain in the orientation until a further pulse of voltage is applied. Advantageously, this enables the molecules to have a memory in that they do not require a continuous voltage supply to maintain a particular orientation. This keeps the amount of energy consumed by the device to a minimum by only applying voltage when a change is required. The voltage may be typically in the range of IV to 4V (as in hydrogels it is desired to stay below the point of electrolysis), but higher or lower voltages might work for different gel/active molecule combinations. In other arrangements the molecules may be configured such that a continuous voltage is required to maintain their orientation. The voltage applied may be AC or DC. For instance, transient square wave pulses of voltage may be used.

Preferably, the carrier material may be a gel. The carrier material may act to contain the molecules such that the molecules are held in position, i.e., to contain the molecules in a region within the device. However, the containment provided by the carrier material can be overcome in the presence of the electric field to allow re-orientation of the molecules as described above.

In some arrangements the gel may be hydrogels (especially gelatine). However, any other gel compositions will work such as Organogels, Xerogels, nanocomposite gels. Gels may be defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady state, although the liquid phase may still diffuse through this system. A gel may be defined phenomenologically as a soft, solid or solid-like material consisting of two or more components, one of which is a liquid, present in substantial quantity. An important property of the gel is its viscosity (and the fact that it needs to be sufficiently transparent with respect to the thickness of the layer used). It needs to be sufficiently viscous to hold the "optically active" molecules in place, without hindering their motion within the electric field.

The electrodes are preferably comprised of electrically conductive material. For instance, the electrodes may be formed of Indium Tin Oxide (ITO). However, the electrodes may be made of any thin metal films, and/or transparent conductive oxides, or conductive polymers. For instance, the electrodes may alternatively be made of Fluorinated Tin Oxide (FTO).

As the first electrode layer is arranged as a layer each of the plurality of electrodes of the first electrode layer are preferably arranged at the same position to each other along the axis perpendicular to the first and second axis. Likewise, as the second electrode layer is a layer each of the plurality of electrodes of the second electrode layer are preferably arranged at the same position to each other along the axis perpendicular to the first and second axis. As the first layer and the second layer are different, the position along the axis perpendicular to the first and second axis of the first layer is preferably different to the position along the axis perpendicular to the first and second axis of the second layer. This likewise applies to the third and fourth layers of electrodes i.e. the position along the axis perpendicular to the first and second axis of the third layer is preferably different to the position along the axis perpendicular to the first and second axis of the fourth layer, which are themselves different to the first and second layer. Each of the first layer and second layer (and third and fourth layer) define a plane in the first and second axis. However, in some arrangements it would be understood that the first layer of electrodes may have a depth in the axis perpendicular to the first and second axis such that each of the plurality of electrodes of the first layer of electrodes need not be at the same position in the axis perpendicular to the first and second axis. Likewise, it would be understood that the second layer of electrodes may have a depth in the axis perpendicular to the first and second axis such that each of the plurality of electrodes of the second layer of electrodes need not be at the same position in the axis perpendicular to the first and second axis. In these arrangements, this depth of each layer would be smaller (i.e., insignificant) compared to the distance (i.e., difference in position) between the first and second layers (along the axis perpendicular to the first and second axis). The above is also applicable to the third and fourth layers of electrodes.

Preferably, the transparent substrate is glass. In other arrangements, the transparent substate may be a plastic material, such as Perspex™.

According to a further aspect there is provided a method of controlling the transmission of thermal radiation from an external source though a window system, comprising: a windowpane, a first and second electrode layer located adjacent the windowpane, a carrier material located between the first electrode layer and the second electrode layer, the carrier material comprising a plurality of molecules that are orientable in the presence of an electric field, and a processor, the method comprising: determining a position of an external source of electromagnetic radiation, where electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane of the window system; calculating based on the determined position a direction in which the electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane; determining, based on the calculated direction, an electrode in a first electrode layer and an electrode in a second electrode layer to apply a potential difference between so as to generate an electric field in the carrier material and thereby orientate molecules of the plurality of molecules located between the electrode in the first electrode layer and the electrode in the second electrode layer perpendicular to the direction in which the electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane so as to alter the transmission of electromagnetic radiation through the window system; and generating the electric field by applying a potential difference between the determined electrode in the first electrode layer and the determined electrode in the second electrode layer.

The altering is preferably to reduce the transmission of electromagnetic radiation through the window system.

Preferably, wherein the window system may further comprise a third electrode layer and a fourth electrode layer, located adjacent the windowpane, each of the third and fourth electrode layers comprising a plurality of electrodes; and wherein the carrier material is a first layer of carrier material, and the system further comprises a second layer of carrier material, wherein the second layer of carrier material is located between the third electrode layer and the fourth electrode layer, the second layer of carrier material comprising a plurality of molecules that are orientable in the presence of an electric field; the method may further comprise: determining, based on the calculated direction, an electrode in the third electrode layer and an electrode in the fourth electrode layer to apply a potential difference between so as to generate an electric field in the second layer of carrier material and thereby orientate molecules of the plurality of molecules located between the electrode in the third electrode layer and the electrode in the fourth electrode layer perpendicular to the direction in which the electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane so as to reduce the transmission of electromagnetic radiation through the window system; and applying a potential difference between the determined electrode in the third electrode layer and the determined electrode in the fourth electrode layer.

Preferably, the molecules (located between the electrode in the third electrode layer and the electrode in the fourth electrode layer) may be orientated perpendicular to the orientation of the molecules in the first layer of carrier of material.

Preferably the method may further comprise tracking the position of the external source of electromagnetic radiation over time and repeatedly determining electrodes to apply a potential difference between to ensure the molecules are orientated perpendicular to the direction in which the electromagnetic radiation from the external source of electromagnetic radiation is incident on the windowpane. Over time the position of the external source of radiation may change. For instance, the position of the sun in the sky changes throughout the day. Through continually tracking the position of the source of electromagnetic radiation the potential difference can be applied to the appropriate electrodes to ensure that the molecules maintain the desired orientation relative to the direction of the external radiation. For instance, the difference in position (such as along the first axis) between the electrode of the first layer of electrode and the electrode of the second layer of electrodes to which potential difference is applied may change over time due to the orientation of the molecules requiring to be different due to the changing position of the external source of radiation.

In some arrangements, the step of determining, based on the calculated direction, an electrode in the first electrode layer and an electrode in the second electrode layer, may comprise: determining multiple pairs of electrodes, each pair of electrodes comprising an electrode in the first electrode layer and an electrode in the second electrode layer; and sequentially applying a potential difference to each pair of electrodes, so as to orientate the plurality of molecules in the carrier material, located between the electrode in the first electrode layer and the electrode in the second electrode layer in each pair, perpendicular to the direction in which radiation from the external source of electromagnetic radiation is incident on the windowpane.

Preferably, the multiple pairs of electrodes may be determined so as to orientate all of the plurality of molecules in the carrier material perpendicular to the direction in which radiation from the external source of electromagnetic radiation is incident on the windowpane.

The method may further comprise: detecting via a sensor the position of the external source of electromagnetic radiation.

The method may further comprise : detecting, via a sensor, the intensity of electromagnetic radiation from the external source of electromagnetic radiation; and determining whether to apply the potential difference between the determined electrodes based on said intensity. The method may further comprise: detecting, via a sensor, a temperature in a region adjacent to the window system; and determining whether to apply the potential difference based on said temperature.

DESCRIPTION OF DRAWINGS

Figure 1 is a perspective exploded view of a window comprising a mechanism for controlling the transmission of electromagnetic radiation through the window according to an aspect of the invention.

Figure 2 is a perspective view of the window comprising a mechanism for controlling the transmission of electromagnetic radiation through the window of Figure 1;

Figure 3 is a side on cross sectional view of the window comprising a mechanism for controlling the transmission of electromagnetic radiation through the window of Figure 1;

Figure 4 is a side on cross sectional view of a portion of the window comprising a mechanism for controlling the transmission of electromagnetic radiation through the window of Figure 1 showing details of the electrodes and molecules between the electrodes;

Figures 5A to 5C show a series of side on cross sectional views of a portion of the window comprising a mechanism for controlling the transmission of electromagnetic radiation through the window of Figure 1 showing how controlling orientation of the molecules can be achieved through selectively applying voltage to different electrodes;

Figure 6 shows a series of side on cross sectional views of the window comprising a mechanism for controlling the transmission of electromagnetic radiation through the window of Figure 1 showing how controlling orientation of the molecules can be achieved through selectively applying voltage to different electrodes;

Figure 7 shows a further series of side on cross sectional views of the window comprising a mechanism for controlling the transmission of electromagnetic radiation through the window of Figure 1 showing how controlling orientation of the molecules can be achieved through selectively applying voltage to different electrodes;

Figure 8 is a perspective exploded view of a window comprising a mechanism for controlling the transmission of electromagnetic radiation through the window according to a further aspect of the invention;

Figure 9 is a perspective view of the window comprising a mechanism for controlling the transmission of electromagnetic radiation through the window of Figure 8;

Figure 10 is a side on cross sectional view of the window comprising a mechanism for controlling the transmission of electromagnetic radiation through the window of Figure 8;

Figure 11 is a front view of layers that make up a portion of the mechanism of Figure 8;

Figure 12 is a side on cross sectional view of a window comprising a mechanism for controlling the transmission of electromagnetic radiation through the window according to a further aspect of the invention;

Figure 13 shows a coordinate-axis system demonstrating the angles over which the molecules can be orientated of the device in Figures 7 to 12;

Figure 14 shows a side on cross sectional view of a window according to an aspect of the present invention comprising a mechanism for controlling the transmission of electromagnetic radiation through the window in one configuration allowing external electromagnetic radiation to pass through the window;

Figure 15 shows a side on cross sectional view of a window according to an aspect of the present invention comprising a mechanism for controlling the transmission of electromagnetic radiation through the window in one configuration preventing external electromagnetic radiation passing through the window; Figure 16 shows a top view of a room in which a window according to an aspect of the present invention, comprising a mechanism for controlling the transmission of electromagnetic radiation through the window, is located showing the field of view for people in different positions within the room;

Figure 17 shows a front on view of the window of Figure 16 from the perspective of a person in the room showing their field of view through the window;

Figure 18 shows a front on view of the window of Figure 16 from the perspective of a different person in the room showing their field of view through the window;

Figure 19 shows a schematic view of a controller part of the mechanism for controlling the transmission of electromagnetic radiation through the window according to an aspect of the present invention; and

Figure 20 shows is a perspective exploded view of a window comprising a mechanism for controlling the transmission of electromagnetic radiation through the window according to a further aspect of the invention.

DETAILED DESCRIPTION

The present invention is directed to a window system having a device (otherwise referred to as mechanism) to control the transmission of electromagnetic radiation through the window system. The window system is capable of determining the position of a source of external electromagnetic radiation, such as the sun, and causing the device to alter the transmission of electromagnetic radiation through the window system. One advantage of the device is its ability to reduce transmission of electromagnetic radiation through the window system from the external source whilst ensuring transmission of light (radiation) from other sources in other directions is not attenuated, so as to maintain a high transparency through the window system except from the light directly incident from the external source. A further feature is the ability to adjust, i.e., reduce or increase, the transmission of electromagnetic radiation through the window in real time. This can enable the window to respond to outside (and inside) temperatures aiding in thermal regulation of the building in which it is used as transfer of heat through the window can be controlled.

Figure 1 is a perspective exploded view of a window 100 comprising a mechanism 1 for controlling the transmission of electromagnetic radiation through the window according to an aspect of the invention. Figure 2 is a perspective view of the window 100, comprising a mechanism 1 for controlling the transmission of electromagnetic radiation through the window of Figure 1.

As can be seen the window 100 comprises two glass panes 101 and 103. The mechanism

1 is located between the glass panes 101 and 103 such that the glass panes 101 and 103 sandwich mechanism 1. The mechanism 1 consists of a series of layers. A layer of electrodes 2 are located adjacent the glass pane 101, and a layer of electrodes 4 are located adjacent the glass pane 103. A gel layer 6 is located between the layer of electrodes 2 and layer of electrodes 4.

The layer of electrodes 2 contains a plurality of electrodes (such as 5a 5b) arranged within the layer. Likewise, the layer of electrodes 4 contains a plurality of electrodes (such as 8a 8b) arranged within the layer. Each of the electrodes of the layer 2 and layer

4 have an elongate shape that extends along an axis, i.e., the x-axis as shown in Figure 1 and 2. Each of the plurality of electrodes of the layer 2 are spaced apart from each other along the y-axis by an insulating gap, and each of the plurality of electrodes of the layer 4 are spaced apart from each other along the y-axis by an insulating gap. The layer of electrodes 2 is spaced apart from the layer of electrodes 4 along the z-axis (as shown in Figure 1 and 2).

Each windowpane 101 103 have two opposing major surfaces extending in the x-y plane. Only one major surface can be seen in Figure 1 for each windowpane, with major surface 105 visible for windowpane 103, and major surface 107 visible for windowpane 101.

The gel layer 6 includes a viscous gel matrix having anisotropic molecules located within. In the examples shown the anisotropic molecules are single walled carbon nanotubes. Figure 3 is a side on cross sectional view of the window 100 of Figures 1 and 2 showing the layers as described above when looking along the x-axis. Inset 120 shows a zoomed in version of a region of the window’s 100 cross section showing the anisotropic molecules 10 in gel layer 6. Figure 4 shows a further detailed view of what is shown in inset 120 of Figure 3. As can be seen the anisotropic molecules 10 are single walled carbon nanotubes have an elongate rod-like shape having a length longer than their width. A large number of anisotropic molecules 10 are shown, however in reality the concentration of active molecules 10 within the gel layer 6 will be in the pmol to mmol range. Prior to voltages being applied to the layers of electrodes the anisotropic molecules 10 may be randomly orientated as shown in Figure 4. The gel matrix acts to support and suspend the anisotropic molecules 10 in a particular orientation so that they do not randomly move within the gel matrix. However, upon application of voltage to the electrode layers 2, 4 the orientation of the anisotropic molecules may change, as will be described in detail below.

The anisotropic molecules 10 permit transmission of radiation through the gel layer 6 dependent on their orientation. For instance, by orientating the anisotropic molecules 10 such that their longest side is parallel to the incoming radiation, the anisotropic molecules 10 may provide minimal (or no) attenuation of the radiation. Whereas orientating the anisotropic molecules 10 such that their longest side is perpendicular to the incoming radiation, the anisotropic molecules 10 may provide maximum (or full) attenuation of the radiation. Thus, by controlling the orientation of the anisotropic molecules 10, with respect to the orientation of the incoming radiation, the transfer of electromagnetic radiation (and therefore heat) through the window 100 can be controlled. The transmission of radiation through the layer is proportional to approximately sin ² (® i), where ®i is the angle between the electric field and the molecular main axis (i.e. their longest side).

The ability to finely control the orientation of the molecules 10 requires a reasonable ratio of the width of the gel layer 6 in the z-direction (as indicated by di in Figure 4) to height of each electrode in the y-direction (as indicated by hi in Figure 4). In addition, by having di greater than the length of the anisotropic molecules (as indicated by L in Figure 4) the anisotropic molecules 10 can be oriented at any angle. Upon application of a voltage to electrode layer 2 and electrode layer 4 a potential difference can be set up causing an electric field in the gel layer 7. If the electric field is sufficient to overcome the force provided by the gel, holding the anisotropic molecules 10 in place, this electric field can polarise the molecules 10 within the gel layer 7 such that they orientate along the electric field lines. By only applying voltage to select electrodes in each of the electrode layers 2, 4 the exact orientation of the anisotropic molecules 10 can be controlled. An example of this is shown in Figures 5A to 5C.

In Figure 5A a positive voltage is applied to electrode 5a and a negative voltage to electrode 8c, thus setting up a relative potential between electrode 5a and electrode 8c. No voltage is applied to any of the other electrodes (5b, 5c, 5d, 5e, 8a, 8b, 8d, 8e). Thus, an electric field formed between electrode 5a and 8c causes the anisotropic molecules 10 between these electrodes to align along the direction of the electric field lines. As electrode 5a is at a different position to electrode 8c along the y-axis this causes the anisotropic molecules to align at an angle in the y-z plane along a line formed between electrode 5a and electrode 8c.

Figure 5B shows a further example of how to orientate molecules 10 in a certain orientation. In Figure 5B a voltage is applied to electrode 5c and a negative voltage to electrode 8c, thus setting up a relative potential between electrode 5c and electrode 8c. No voltage is applied to any of the other electrodes (5a, 5b, 5d, 5e, 8a, 8b, 8d, 8e). Therefore, an electric field formed between electrode 5c and 8c causes the anisotropic molecules 10 between these electrodes to align along the direction of the electric field lines. In this example the electrode 5c is at the same position to electrode 8c along the y-axis, which causes the anisotropic molecules to align along the z-axis, i.e., along a line formed between electrode 5c and electrode 8c.

Figure 5C shows a further example of how to orientate molecules 10 in a certain orientation. In Figure 5C a positive voltage is applied to electrode 5e and a negative voltage to electrode 8b, thus setting up a relative potential between electrode 5e and electrode 8b. No voltage is applied to any of the other electrodes (5a, 5b, 5c, 5d, 8a, 8c, 8d, 8e). Thus, an electric field formed between electrode 5e and 8b causes the anisotropic molecules 10 between these electrodes to align along the direction of the electric field. In this example the electrode 5e is at a different position to electrode 8b along the y-axis which causes the anisotropic molecules to align at an angle in the y-z plane along a line formed between electrode 5e and electrode 8b.

Figures 5A to 5C demonstrate how the electrodes can be independently controlled. In the arrangements shown in Figure 5B radiation incident along the window along the z- direction would pass through the window unimpeded due to the molecules 10 being aligned along the z-axis. In comparison, the arrangements shown in Figures 5A and 5C would provide some attenuation to the radiation passing along the z-direction as molecules 10 have an orientation with some y-component.

In certain instances, it may be desired that all the anisotropic molecules 10 within the gel layer 6 are orientated in the same direction. One way in which this may be achieved is shown in Figure 6 which shows a series of side on cross sectional views of window 100 at a series of points in time. At t=0, as shown in 20a, a voltage is applied to only electrodes 5a and 8b setting up a potential difference between these two electrodes. This causes the anisotropic molecules in the region between these two electrodes to orientate in a direction between the electrodes 5a and 8b. At t=l, as shown in 20b, a voltage is applied to only electrodes 5b and 8c setting up a potential difference between these two electrodes. This causes the anisotropic molecules in the region between these two electrodes to orientate in a direction between the electrodes 5b and 8c. At t=2, as shown in 20c, a voltage is applied to only electrodes 5c and 8d setting up a potential difference between these two electrodes. This causes the anisotropic molecules in the region between these two electrodes to orientate in a direction between the electrodes 5c and 8d. At t=3, as shown in 20d, a voltage is applied to only electrodes 5d and 8e setting up a potential difference between these two electrodes. This causes the anisotropic molecules in the region between these two electrodes to orientate in a direction between the electrodes 5d and 8e. By continuing this pattern along the whole length of the electrode layers, i.e., applying a potential difference in the way shown in 20a-20d along the whole length of the electrode layers, the anisotropic molecules along the entire length of the gel layer 6 can be orientated in the same direction. As the difference in position (along the y-axis) of the electrodes to which a voltage is applied is the same at each moment in time (i.e., between 20a, 20b, 20c and 20d) the molecules along the length of the gel layer 7 are caused to orientate in the same direction to each other. Figure 7, which shows a series of side on cross sectional views of window 100 at a series of points in time, demonstrates a further way in which all the anisotropic molecules 10 within the gel layer 6 can be orientated in the same direction. Between time t=0 and t=3 a voltage is applied to the electrodes 5a-5d, and 8b-8e as described above in relation to Figure 6 between time t=0 and t=3. However, in addition at t=0, as shown in 20e, a voltage is applied to electrodes 5m and 8n, in addition to electrodes 5a and 8b, setting up a potential difference between electrodes 5m and 8n. This causes the anisotropic molecules in the region between these two electrodes to orientate in a direction between the electrodes 5m and 8n. Likewise, at t= 1 , as shown in 20f, a voltage is applied to electrodes 5n and 8o, in addition to electrodes 5b and 8c, setting up a potential difference between electrodes 5n and 8o. This causes the anisotropic molecules in the region between these two electrodes to orientate in a direction between the electrodes 5n and 8o. At t=2, as shown in 20g, a voltage is applied to electrodes 5o and 8p, in addition to electrodes 5c and 8d, setting up a potential difference between electrodes 5o and 8p. This causes the anisotropic molecules in the region between these two electrodes to orientate in a direction between the electrodes 5o and 8p. At t=3, as shown in 20h, a voltage is applied to electrodes 5p and 8q, in addition to electrodes 5d and 8e, setting up a potential difference between electrodes 5p and 8q. This causes the anisotropic molecules in the region between these two electrodes to orientate in a direction between the electrodes 5p and 8q.

Although molecules that are neighbouring the region between the two electrodes to which a potential difference has been applied may experience a residual electric field this will drop off with distance and will provide a negligible effect on the overall ordering of the molecules achieved using the methods shown above. In any case, as electrodes 5m-5p and 8n-8q are sufficiently far from electrodes 5a-5d, and 8b-8e then the electric field from electrodes 5m-5p and 8n-8q does not have an impact on the molecules in the region between electrodes 5a-5d, and 8b-8e, and vice versa. Therefore, the speed of switching molecule orientation throughout the device can by increased by applying the voltage to electrodes in different regions that are sufficiently far apart. The difference in position (along the y-axis) of the electrodes 5m-5p and 8n-8q is the same as between electrodes 5a-5d, and 8b-8e to ensure the same orientation of the molecules.

Figure 8 is a perspective exploded view of a window 200 comprising a mechanism 80 for controlling the transmission of electromagnetic radiation through the window according to a further arrangement. Figure 9 is a perspective view of the window 200, comprising mechanism 80 for controlling the transmission of electromagnetic radiation through the window, of Figure 8. Figure 10 is a side on cross sectional view of the window 200 of Figures 8 and 9 showing the layers when looking along the x-axis.

As can be seen from Figures 8 and 9 window 200 is formed of glass panes 101 103, and has electrode layer 2 and electrode layer 4, and gel layer 6 as consistent with window 100 in Figures 1 and 2. However, further layers are present in the window 200 of Figure 8 compared to window 100.

Specifically, a further electrode layer 22 is located between electrode layer 2 and windowpane 101. Insulating layer 26 is located between electrode layer 2 and further electrode layer 22. Insulating layer 26 is formed of insulating material that ensures that short circuits do not occur between the electrode layer 2 and electrode layer 22. In addition, a further electrode layer 24 is located between electrode layer 4 and windowpane 103. Insulating layer 28 is located between electrode layer 4 and further electrode layer 24. Insulating layer 28 is formed of insulating material that ensures that short circuits do not occur between the electrode layer 4 and electrode layer 24. The insulating material of the insulating layers 26 28 may be any type of insulating transparent polymers, (including polycarbonate, polyethylene, PVC, polyester, polystirole), or glass, or thin oxides, or any other known insulating material.

The layer of electrodes 22 contains a plurality of electrodes (such as 30a 30b) arranged within the layer. Likewise, the layer of electrodes 24 contains a plurality of electrodes

(such as 32a 32b) arranged within the layer. The electrodes of both layer 22 and layer 24 each have an elongate shape that extends along an axis which is orthogonal to the direction in which the elongate electrodes in layer 2 and layer 4 extend, i.e., the y-axis as shown in Figure 8 and 9. Each of the plurality of electrodes of the layer 22 are spaced apart from each other along the x-axis by an insulating gap, and each of the plurality of electrodes of the layer 24 are spaced apart from each other along the x-axis by an insulating gap. Each layer of electrodes (i.e., layer 22, layer 2, layer 4 and layer 24) are separated from each other along the z-axis (as shown in Figure 8 and 9). Figure 11 shows front on views of electrode layer 2, insulation layer 26 and electrode layer 22. The combination of each of these layers is shown as layer 40. The purpose of the additional electrode layers 24 22 in the arrangement shown in Figures 8 to 10 can enable control of orientation of the anisotropic molecules 10 over a further range of angles. As electrode layers 24 and 22 are arranged orthogonal to those in layer 2 and 4 by controlling the voltage applied to each of the electrodes of layer 24 and 22 in a similar manner as described in relation to Figures 6 and 7, but along the x- axis rather than the y-axis (owing to the different arrangement of the electrodes in these layers).

A non-zero voltage may be applied to electrode layers 24 22 at a different point in time to electrode layers 2 4 so that the electric fields generated by layer 24 22 are not affected by layers 2 4. However, in other arrangements, a non-zero voltage may be applied to electrode layers 24 22 and electrode layers 2 4 at the same time so that the electric fields generated will be a complex combination from each of the electrode layers. Figure 13 shows the axis system 50, as shown in the Figures 1 to 12 (and Figure 20), showing the angles over which the anisotropic molecules 10 can be orientated. Electrode layers 2 and electrode layer 4 control the orientation of anisotropic molecules 10 over the (elevation) angle cp (as shown in Figures 5A to 5C above). Electrode layers 22 and electrode layer 24 control the orientation of anisotropic molecules 10 over the (azimuth) angle 0. Thus window 100 shown in Figures 1 to 3 can be used to orientate molecules over (elevation) angle cp only. Whereas window 200 in Figures 8 to 10 (and window 600 in Figure 20) can be used to orientate molecules over both (elevation) angle cp and (azimuth) angle 0. In some uses orientation over only either elevation angle cp or azimuth angle 0 may be sufficient. However, by having a greater control of orientation of molecules over both elevation and azimuth angles molecule orientation can be tailored to control radiation incident on the window from a wider variety of directions (e.g. both perpendicular polarisation directions).

Figure 12 shows a side on cross sectional view of a window 300 according to a further arrangement, showing the layers when looking along the x-axis. The window 300 of Figure 12 has the same number and arrangement of electrodes layers as in window 200 of Figure 8 but having the layers differently arranged along the z-axis. Specifically, window 300 is identical to the arrangement of layers in window 100, as described in relation to Figures 1 to 3, but with additional layers arranged on the outer major surfaces of windowpanes 101 and 103. Specifically, electrode layer 22 is arranged on outer major surface of pane 101 (such that pane 101 is sandwiched between electrode layers 22 and 2). Electrode layer 24 is arranged on outer major surface of pane 103 (such that pane 103 is sandwiched between electrode layers 24 and 4). Outer coatings 36 and 34 are located on the side of the electrode layers 22 24 opposite to the windowpanes 101 103.

The outer coatings 36 34 aid to protect the electrode layers 22 24. Control of radiation through the window 300 of Figure 12 is carried out by applying voltage to the layers of electrodes in the same way as described in relation to Figures 8 and 9 above.

Figure 20 is a perspective exploded view of a window 600 comprising a mechanism 80 for controlling the transmission of electromagnetic radiation through the window 600 according to a further aspect of the invention.

As can be seen from Figure 20 window 600 is formed of glass panes 101 103, and has electrode layers 2, 4, 22 and 24 as consistent with window 200 in Figure 8. However, the arrangement of the electrode layers is different when compared to the electrode layers in window 200 of Figure 8. There is also two gel layers 6a and 6b in the arrangement in Figure 14, rather than a single gel layer. Specifically, electrode layers 2 and 4 are on either side (i.e. sandwich) gel layer 6b, and electrode layers 22 and 24 are on either side (i.e. sandwich) gel layer 6a. In this arrangement, only a single insulating layer 26 is required separating the electrode layers 4 and 22.

The arrangement of electrode layers in window 600 is such that potential difference applied to electrode layers 2 and 4 (in the manner as described above in relation to Figures 5A to 7) results in an electric field being generated in gel layer 6b causing the molecules 10 in gel layer 6b to be orientated as described above. Whereas potential difference applied to electrode layers 22 and 24 results in an electric fded being generated in gel layer 6a causing the molecules 10 in gel layer 6a to be orientated as described above. Thus, the orientation of molecules 10 in gel layer 6b are controlled by the electrodes in layer 2 and 4, i.e., over the (elevation) angle cp. Whereas the orientation of molecules 10 in gel layer 6a are controlled by the electrodes in layer 22 and 24, i.e., over the (azimuth) angle 0. In this way, each layer 6a 6b may be configured to attenuate a different polarisation direction of the incoming radiation to each other through the controlling of the molecule orientation. For each of the above examples, the windows 100 200 300 600 may be installed in a building such that the windowpane 103 is the external windowpane on the outside of the building and windowpane 101 is the internal windowpane on the inside of the building. Radiation, such as from the sun, is first incident on pane 103 on major surface 105. The radiation passes through the pane 103 and through the transparent electrode layer 4 (and 24 in Figure 12 and 10) before subsequently incident on gel layer 6. Depending on the orientation of the molecules in the gel layer 6 the radiation will either pass through (or a portion thereof will) or be attenuated (via absorption and reflection) by the gel layer. The radiation (if not attenuated) will then pass through the transparent electrode layer 2 (and 22 in Figure 12 and 10) and through the pane 101. Radiation may also travel through the opposite direction (i.e., from pane 101 to pane 103) from inside the building to outside. This will be described in more detail in relation to Figures 14 to 18.

Figure 14 shows a side on cross sectional view of a portion of a window 400 according to an arrangement comprising a mechanism for controlling the transmission of electromagnetic radiation through the window in one configuration allowing external electromagnetic radiation to pass through the window. The window 400 may be any of windows 100 200 300 600 as described above. Window 400 has windowpanes 101 and 103. The window 400 may have the same layers as any of windows 100 200 300 600 as described above, which are not shown in Figure 14. The plurality of molecules 10 in carrier layer are illustrated to show their orientation relative to incoming electromagnetic radiation 60 from the sun 70.

As can be seen in Figure 14, the sun’s 70 radiation 60 has a component of its propagation direction in the y-z plane (i.e. a plane defined by the y and z axis) as indicated by the arrow showing the direction of the radiation (i.e. its direction of propagation). Here we are only considering its directional component in the y-z plane. The molecules are orientated such that they are also orientated in the y-z plane with their major axis along the same direction as the radiation 60. In this way, as the sun’s radiation and the molecules are parallel to each other, the molecules do not attenuate the sun’s radiation 60. In this configuration the sun’s radiation is allowed to pass through the window. Figure 15 shows a side on cross sectional view of a portion of a window 400 of Figure 14 with the mechanism for controlling the transmission of electromagnetic radiation through the window in a further configuration preventing external electromagnetic radiation from passing through the window. The change in orientation of the molecules 10 between Figures 14 and 15 may be achieved as described above for the previous Figures 5A to 7.

As can be seen in Figure 15, the sun’s 70 radiation 60 has a component of its propagation direction in the y-z plane. The molecules are orientated such that they are also orientated in the y-z plane with their major axis perpendicular to the direction of the propagating radiation 60. In this way, as the direction of propagation of the sun’s radiation and the molecules are perpendicular to each other, the molecules attenuate the sun’s radiation 60. In this configuration the sun’s radiation is prevented from passing through the window.

Although only a propagation direction in the y-z plane is shown in Figure 15 the light from the sun may also propagate along the x-z plane too, i.e. the sun’s radiation may not necessarily be confined to the y-z plane and may have components along both planes. In other words, it may have both azimuthal and elevation components. However, both of these components can be treated separately with the arrangement as described in relation to Figure 15 only blocking the radiation propagating along the y-z plane.

To attenuate the radiation component propagating along the x-z plane, a separate layer of molecules (such as layer 6a as shown in Figure 20) (or the same layer of molecules as is the case in Figures 10 and 12) will be controlled such that these molecules may have an orientation in the x-z plane (not shown) (such that the direction of propagation of the sun’s radiation and the molecules are still perpendicular to each other). This may be controlled such as through the use of electrode layers 22 and 24 as shown and discussed in the arrangements in Figures 10 and 12 and 20.

In reality, by taking the above described approach each of these mechanisms will block a single polarisation contribution of the sun’s radiation (as the sun’s radiation is not polarised it will have two perpendicular polarisation contributions). One of these polarisation will be blocked by the orientation of the molecules as shown in Figure 15 (i.e. in the y-z plane) and the other polarisation may be blocked by the orientation of the molecules x-z plane (i.e. using layers 22 and 24).

Figure 16 shows a top view of a room in which the window 400 of Figures 14 and 15 is located showing the field of view for people in different positions within the room. As can be seen window 400 is located on one side of room 72 with pane 101 being internal to the room and pane 103 being external to the room 72. Radiation 60 from the sun is shown as being incident on the window 400 at an angle in the x-z plane (but will also have a contribution in the y-z plane as outlined above). The molecules 10 in the window

400 are orientated as shown in Figure 15 blocking the radiation from the sun 70 along the direction of incidence.

Three people 74 75 76 are shown in the room 72 each positioned in a different location thereby having a different view through the window 400. The first person at position 74 has field of view 78. As the molecules are orientated in a direction that is largely parallel (i.e., not perpendicular) to the light along the field of view 78 the first person 74 sees through the window with full transparency as the molecules do not block the light in their field of view 78 (as no light in their field of view is not directly from the sun). This can be seen in Figure 17 which shows the first person’s 72 view 74 through window

400 showing no visible changes to the transparency such that they see object 84 with no loss of transparency.

The second person at position 76 has a field of view 82. As the sun 70 is in their field of view 82 the radiation 60 from the sun is incident on window 400 and as the molecules are orientated perpendicular to the sun’s radiation 60 they block the sun’s direct radiation 60. However, radiation from different sources that are not incident along the same direction as the sun’s radiation 60 can pass through the window 400 unimpeded giving no change to transparency. This can be seen in Figure 18 which shows the second person’s 76 view 82 through window 400 showing a dark ring 86 around the sun 70 that gets darker towards its centre. This is due to the molecules 10 being orientated in the arrangement as discussed above blocking the radiation from the sun 70. As can be seen however, no visible changes to the transparency is observed for other objects such as object 84, which can be seen with no loss of transparency as the light from this object is not perpendicular to the orientation of the molecules 10. The third person 75 having a field of view 80 also sees an almost unobstructed transparent view, but with the sun 70 that is just in the field of view having a dark outline blocking out the sun’s direct radiation.

As the sun moves over the course of the day the molecules may be re-oriented as described above so as to ensure that the radiation from the sun remains blocked.

The windows 100 200 300 400 600 may also include a controller 501 that is capable of controlling the voltage applied to the electrodes to tailor the radiation transmission of the windows as shown in Figure 19. The controller 501 has a microprocessor 503 and memory 505.

Controller 501 is in communication with sensor(s) 507. Sensor(s) 507 may include one or more sensors for measuring parameters. For instance, the sensor may be a temperature sensor for detecting the temperature inside and/or outside of the building on which the window system is installed (for instance either side of windowpanes 103 101). The sensor 507 may also, or in addition, include a radiation detector (such as a light/UV and/or IR sensor). By having a radiation detector(s), the position of the sun can be determined through detecting the suns radiation, and/or the intensity of the sun’s radiation can be determined.

The controller 501 is also in communication with a power source 509 which is capable of supplying the voltage to electrode layers 2, 4, 22, 24. The power source 509 may be a power supply such as mains powered, or battery powered. The voltage may be a DC voltage or AC voltage. As the gel layer 6 (and 6a 6b) has a density such that the anisotropic molecules 10 can change orientation only under the influence of the electric field the voltage needs only be applied to the electrodes when their orientation needs to be changed, i.e., when the thermal properties of the window is to be altered. Advantageously, this means that the amount of power consumed by the device can be kept low as power is only required when a change is required, rather than continuously.

The processor 503 of the controller 501 may be capable of carrying out tasks to control the operation of the window 100 200 300 400 600. The sensor(s) 507 may be configured to detect a position of the sun’s radiation to determine its position. Based on this position of the sun, the processor may determine the position of the sun relative to the window (or another fixed reference point). For instance, it may determine the azimuth and/or elevation of the sun in the sky. Based on the determined position of the sun in the sky the processor may be configured to determine the direction through which the sun’s radiation is incident on the window. Based on the determined direction the processor can determine which electrodes in each layer to apply a potential difference between (for instance, as described above in relation to Figures 5A to 7) and then control the power source to apply the potential difference to the determined electrodes to align the molecules to either allow or prevent the passage of radiation through the window.

The processor 503 may be capable of determining whether the molecules should be orientated so as to attenuate the radiation from the sun or not. For instance, the processor may receive a signal from the sensor(s) 507 indicating the temperature inside of the building in which the window is installed. If the temperature is below a certain threshold the processor 503 may determine not to apply a potential difference to the electrodes so as to not block radiation from the sun. Alternatively, if the temperature is above a certain threshold the processor 503 may determine to apply a potential difference to the electrodes to orientate the molecules so as to block radiation from the sun. However, in some instance, even if the temperature is below a certain threshold the processor 503 may determine to apply a potential difference to the electrodes to reorientate to molecules in an orientation so as to not block radiation from the sun (for instance, if the molecules are already orientated in a direction to block radiation from the sun).

Likewise, the same approach may be taken with the processor deciding to re-orientate the molecules (or not) dependent on the processor receiving a signal indicating the intensity of the sun’s radiation from the sensor(s) 507. For instance, when the intensity is above a threshold the processor may decide to block the sun’s radiation.

The processor 503 can apply a voltage to each of electrodes of each layer independently. For instance, the processor may select which electrode in layer 2 to apply a voltage to and which electrode in layer 4 to apply a voltage to achieve the desired orientation of the molecules over angle cp. It may also select which electrode in layer 22 to apply a voltage to and which electrode in layer 24 to apply a voltage to achieve the desired orientation of the molecules over angle 0. The above description is presented to enable any person skilled in the art to make and use the system and is provided in the context of a particular application. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art.

The windows 100 200 300 600 shown here may be any type of window containing more than one pane of glass. For instance, they may be double glazed windows with panes 101 and 103 forming the two panes of the double-glazing unit. Alternatively, they may be triple glazed windows with further panes of glass to those shown. The panes 101 103 have a rectangular shape but it would be understood that they may be any shape to fit the window recess. The panes 101 and 103 are transparent glass substates. However, the present invention may equally be used in other types of substates for instance plastic, such as Perspex™.

The electrode layers 2, 4, 22, 24 are made from Indium Tin Oxide (ITO). However, could be made from any type of electrically conductive material such as aluminium, silver, gold, or any thin metal, or transparent conductive oxides including (ITO, TCO), or conductive organic molecules.

In the arrangement shown in Figure 1 the electrodes are arranged such that they are elongate along the x-axis only and thus control orientation of molecules over (elevation) angle cp only. However, in other arrangements the window may have electrodes that are arranged such that they are elongate along the y-axis only and thus control orientation of molecules over (azimuth) angle 0 only.

Although the electrodes in the layers of the windows described above are elongate, in other arrangements they need not necessarily be so. In other arrangements they may have a square shape, such that each elongate electrode shown in Figure 1, for example, are split into a series of square electrodes. Each of the square electrodes are independently controllable. Applying a voltage to a row or column of electrodes in this manner may enable the same effects as described above in relation to the arrangements having elongate arrangements of electrodes. However, having square electrodes may enable a greater control of orientations achievable. Although the electrodes are shown as being straight in other arrangements the electrodes may be curved. In other arrangements, the electrodes may be arranged diagonally with respect to panes 103 and 101 rather than parallel to either the x or y axis. For instance, the electrodes 2, 4 may be arranged diagonally in an opposite direction to electrodes 22 24 to achieve the same effect as described in the above arrangements. The examples shown in the figures are only a select number of examples of the arrangements of the layers. In other arrangements the layers may be arranged differently with respect to the panes of glass 101 103. For instance, electrode layers 2 and 4 may be arranged on the other side of panes 101 103. The anisotropic molecules in the described examples are single walled carbon nanotubes. However, any type of anisotropic particle may be used so long as its orientation can affect the passage of radiation through the device. The term anisotropic is used to denote a molecule exhibiting properties with different values when measured in different directions. Anisotropic shaped molecules are non-spherical molecules whose shape can typically be approximated by a simplified shape having a long axis and a much shorter axis, e.g. in rod-shaped.

Although the devices are described in relation to windows for buildings the above arrangements may be used in any type of window. For instance, windows for a vehicle, or machinery may employ these above-described arrangements. In addition, the invention may not necessary be limited to windows and may be applicable for use on any type of glass product.

In addition, the mode of operation described above in relation to Figures 6 and 7 are just a few examples of how the device may be used. The choice of which electrodes to apply voltage to at each point in time may be varied dependent on device use. For instance, it may be desired that only a portion of the window is controlled to prevent radiation through that region of the window - so voltage is applied to electrodes only at that point. Whereas no voltage may be applied to electrodes in other regions of the window where it is not required to reduce the passage of radiation through the window.

In the above-described examples, the molecules are configured to aid in the modulation of electromagnetic radiation of a variety of wavelengths through the window. For instance, both UV, visible and IR radiation are modulated by the anisotropic molecules. However, in other arrangements the molecules may be configured to modulate only one specific wavelength band. For instance, blocking IR but allowing passage of IR radiation.

Altering the transmission of electromagnetic radiation in the above-described examples is caused by the anisotropic molecules which, depending on their orientation, absorb and/or reflect light therefore altering the thermal radiation properties of the window. However, thermal conductivity along the long axis of the molecules is typically much higher (for carbon nanotubes by as much as orders of magnitude) than in a perpendicular direction. This can provide a further means of improvements of energy efficiency.

However, as the molecules are embedded into a window (such as a double or triple pane window) this thermal conductivity does not play a significant role in practice, and the predominate effects are based on the transmission attenuation of the thermal radiation.

It is noted that polarisation of TEM waves is always perpendicular to their propagation direction i.e. the plane of polarisation of the incoming light will be perpendicular to the direction of the light. Minimum transmission can be reached when all polarisations within that plane can be rejected (through absorption and/or reflection). It is sufficient to arbitrarily choose two perpendicular (to each other) polarisations within that plane to reach minimum transmission, i.e. by arranging the electrodes in the different layers

(layers 2 and 4 compared to layers 24 and 22) substantially perpendicular to each other - but the arrangement need not necessarily be the horizontal and vertical orientation of the electrodes as shown in the above figures but may be arranged at any angle so long as the sets of layers are perpendicular to each other in the x-y plane which is perpendicular to the incoming direction of the radiation.

Although the example of the sun’s radiation is given above it would be understood that the device may be capable of altering the transmission through the window of any type of external source of radiation. For instance, there may be an external light source (such as a streetlight) that it may be desirable to block light from passing through the window.

Although not shown in any of the arrangements above, in some arrangements there may be an additional insulative layer between the electrodes and the gel layers. For instance, between electrode layer 2 and get layer 6b in Figure 14, or for instance between electrode layer 2 and gel layer 6 in Figure 1. The purpose of the insulative layer between the electrodes and gel layers may be to serve as a thin protective layer to enable higher voltages (if so desired) to be used in conjunction with a hydro-gel within the gel layer without getting unwanted electrolysis.