GB2532713A

GB2532713A - Lighting assembly

Info

Publication number: GB2532713A
Application number: GB1419115.9A
Authority: GB
Inventors: David Shadbolt Philip
Original assignee: ZETA SPECIALIST LIGHTING Ltd
Current assignee: ZETA SPECIALIST LIGHTING Ltd
Priority date: 2014-10-27
Filing date: 2014-10-27
Publication date: 2016-06-01
Also published as: GB201419115D0

Abstract

A solar-powered lighting assembly 102 comprises a photovoltaic arrangement 106 and an illuminating arrangement. The illuminating arrangement comprises LED arrays 114 and a light dispersing structure 104 made of transparent thermoplastic arranged over at least a portion of the photovoltaic arrangement 106. The light-dispersing structure 104 admits ambient solar light to the photovoltaic arrangement 106 and redirects and disperses light from the LED arrays 114 out of the solar powered lighting assembly 102 to illuminate the surroundings. A base element 108 contains a controller 110 and rechargeable battery 112.

Description

Lighting assembly This invention relates generally to solar-powered lighting assemblies, and in particular to self-contained, compact solar-powered lighting assemblies.

Increasing interest and investment over recent years in solar power as a renewable energy source has resulted in photovoltaic cells becoming more cost effective, and has also resulted in an increased production capacity. Similarly, interest in higher efficiency light sources has resulted in improved light-emitting diodes (LEDs). The achievable output for LEDs has increased, and the costs of manufacturing LEDs are falling. As a result, the combination of solar photovoltaics with light emitting devices such as LEDs into an off-grid lighting solution is highly attractive, particularly in view of the significant portion of the world's energy that is used for lighting.

However, it is difficult to combine solar photovoltaics with light-emitting diodes into a compact single product because of the need to have the photovoltaic cells and the light emitting diodes in separate physical locations, i.e. they cannot cover the same surface. This is because the light-emitting diodes would obscure the photovoltaic cells (and hence reduce the generated electrical energy) if they were placed over the photovoltaic cells on the same surface. This is undesirable as it means that for a given surface that is illuminated, it is necessary to allocate an additional surface of similar area upon which to mount the photovoltaic cells. This makes such a lighting assembly less appealing and less viable as an off-grid lighting solution.

According to the invention there is provided a solar-powered lighting assembly comprising: a photovoltaic arrangement; and an illuminating arrangement comprising: at least one light source; and a light-dispersing structure arranged over at least a portion of the photovoltaic arrangement; wherein the light-dispersing structure is configured to admit ambient solar light to the photovoltaic arrangement and to redirect and disperse light from the light source out of the solar-powered lighting assembly. -2 -

It can thus be seen that in accordance with the invention, a solar-powered lighting assembly can be provided which can be illuminated in the same area as the photovoltaic arrangement -i.e. it is not necessary to spatially separate the energy generation and the illumination. This arrangement provides obvious advantages in the reduction of space required, as the photovoltaic arrangement can be provided behind the light-dispersing structure. For example, the photovoltaic arrangement may be completely behind the light dispersing structure. A surface of the solar-powered lighting assembly can be used for both receiving ambient light and emitting generated light. This is in contrast with the prior art, which as noted above, requires photovoltaic cells to be to be provided on a separate surface from the light-emitting arrangement to prevent the light-emitting arrangement from obscuring the transmission of ambient light to the photovoltaic cells.

The light-dispersing structure preferably comprises a light guide panel. The light guide panel is preferably substantially flat, although it may have a curved surface, and preferably comprises a front surface and a back surface, and an edge surrounding the panel. The light-dispersing structure may comprise any suitable material or combination of materials (e.g. layers of materials). As non-limiting examples, the light-dispersing structure may comprise glass or plastics, e.g. thermoplastics.

The light-dispersing structure may be translucent. As used herein, translucent has the meaning of permitting the transmission of at least a portion of light incident on the light-dispersing structure. The light-dispersing means is preferably transparent.

As used herein, transparent has the meaning of transmitting all or substantially all of the light incident on the light-dispersing structure within a particular band (or bands) of wavelengths. The light-dispersing structure is preferably transparent at visible wavelengths and/or at wavelengths suitable for generating energy using the photovoltaic arrangement. The light-dispersing structure is preferably configured such that light that is incident substantially normally on the front and or back surface thereof is transmitted through the light-dispersing structure, while light travelling through the material of the light-dispersing structure itself, in a direction having a substantial component parallel to the front and/or back surface thereof is totally -3 -internally reflected, except when it is incident on a light-dispersing element, as discuss further below.

In a set of embodiments the assembly comprises a solar concentrator arrangement to enhance the amount of light incident on the photovoltaic arrangement. This may be separate from, or formed as part of, the light dispersing structure.

Dispersion and/or redirection of the light from the light source by the light-dispersing structure may be achieved by any of a number of suitable configurations of the light-dispersing structure. In a set of embodiments the light is dispersed and/or redirected by light-dispersing elements on the front and/or back surfaces of the light-dispersing structure. For example, the front and/or back surface may be provided with raised or recessed (e.g. etched) dots, lines and/or patterns that cause light travelling substantially parallel to the front and/or back surface to be refracted, diffracted or reflected in a direction outward of the light-dispersing structure. The light-dispersing elements may be created using laser or mechanical etching. Additionally, or alternatively, the light-dispersing elements may be created using screen printing.

The light source may comprise any light-emitting device that can be powered using electrical energy. For example, the light source could comprise one or more filament light bulbs or light-emitting phosphorous strips. However, in preferred embodiments, the light source comprises a plurality of light emitting diodes (LEDs).

The photovoltaic arrangement preferably comprises at least one photovoltaic cell, preferably a plurality of photovoltaic cells. For example, photovoltaic cells may be arranged in an array. The photovoltaic arrangement could be substituted by any other energy generation means that can generate an electrical current from solar light.

In a set of embodiments the light source(s) is/are mounted at the edge of the light-dispersing structure. For example, the light source(s) may be arranged along one or more edges of the light-dispersing structure such that light therefrom passes into longitudinally into the light-dispersing structure. The light source may thus be configured so as to emit light substantially parallel to the front and/or back surfaces -4 -of the light-dispersing structure so that the light therefrom is totally internally reflected by the front or back surfaces but is refracted, diffracted or reflected out of the light-dispersing means by the light-dispersing elements.

Additionally or alternatively, the light source(s) may be provided embedded in the light-dispersing structure, and/or provided behind the light-dispersing structure. In such arrangements, the light source(s) may be arranged so as to cover a relatively small surface area (i.e. less than half the area of the light dispersing structure). This allows ambient solar light to be admitted to the photovoltaic arrangement without a significant amount of the light being obscured by the light source. This still provides the advantage of having an illuminating surface that can also be used to receive light for energy generation. This is because the light-dispersing structure receives light from the small light-emitting area of the embedded light source, but disperses the light, e.g. through light-dispersing elements over a large area, potentially the entire front surface of the light-dispersing structure. Accordingly, the entire front surface of the light-dispersing structure may appear illuminated. This contrasts with the prior art, in which only the regions where the LEDs are positioned will appear illuminated.

The light-dispersing structure may cover at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 95% of the photovoltaic arrangement. In some embodiments, all or substantially all of the photovoltaic arrangement is covered by the light-dispersing structure.

In accordance with some embodiments of the invention, the light-dispersing structure may have a portion that covers or is covered by a display article (for example, a poster or a sign) so that the light dispersing structure illuminates the display article.

The assembly may be configured so that energy generated by the photovoltaic arrangement is used immediately to generate light. This may be the case, for example, where it is desirable to light a display panel to draw attention to the display panel even though there is sufficient ambient light to read the display panel without illumination. In such embodiments, as the energy is used directly and immediately to generate light, it is not necessary to store the energy. -5 -

However, in preferred embodiments, the solar-powered lighting assembly comprises energy storage means. For example, the energy storage means may comprise a battery or a super capacitor. In accordance with embodiments having energy storage means, the lighting assembly may be configured so that energy generated by the photovoltaic arrangement is stored in the energy storage means to be used later to power the light source. The illuminating means may be switched off while the energy storage means is being charged, or it may be run at a lower power level (e.g. with some but not all LEDs being illuminated). Alternatively, the light source could be lit during the charging of the energy storage means. For example, the photovoltaic arrangement may be able to generate enough energy to power the light source directly and also to store energy to power the light source at a later time when ambient light is not available for energy generation. However, preferably the light source is switched off while the energy storage means is being charged in the presence of ambient light, and then the light source is switched on when the ambient light is diminished.

Additionally or alternatively, the lighting assembly may be connected to an electricity grid. Some or all of the energy generated by the photovoltaic arrangement could be provided to the grid (e.g. sold to the grid) and then some or all of the energy required to power the light source could be drawn from the grid at a later time. Such an arrangement may make the assembly less expensive to run. For example, as the energy generated during daylight hours that is transmitted to the grid can be sold (e.g. at peak rate) and then energy can be brought back from the grid (e.g. at non-peak rate) during night time hours.

However, in preferred embodiments, the solar-powered lighting assembly is not connected to an electricity grid. The combination of energy generation with illumination in a single assembly provides the advantage that it is not necessary for the assembly to be connected to the grid; the assembly may be self-contained and entirely self-powered. The energy storage means extends this advantage to embodiments in which the light source is to be powered at a different time from when energy is generated by the photovoltaic arrangement. -6 -

The light source may be configured to emit light at predetermined times, for example, at night. The lighting assembly may be provided with a programmable controller to allow the lighting assembly to be configured to power the light source at chosen times programmed into the controller. Additionally or alternatively, the lighting assembly may comprise one or more proximity sensors, for example to detect parked vehicles. The lighting assembly may be configured to power the light in response to a signal generated by proximity sensor(s).

Where the lighting assembly comprises two or more light sources, each light source may emit light that is a different colour from light emitted by at least one other light source. For example, the light source may comprise different coloured LEDs. The light emitters may be powered in different combinations, e.g. to generate different coloured light in different situations. For example, in combination with the proximity sensors mentioned above and/or a connection for receiving data (e.g. information relating to traffic conditions), the light source could be used to indicate free parking spaces, lane closures, etc. using different light colours.

The lighting assembly may be configured to power the light source when ambient light levels drop. The light level may be determined from the photovoltaic arrangement -e.g. from the voltage across it. For example, the lighting assembly may be provided with electronic circuitry configured to allow energy stored in the energy storage means to power the light source when the voltage across the photovoltaic cells drops below a threshold value.

The lighting assembly may be provided with a processor having an algorithm which checks the real time and adjusts the light output of the light source depending on the real time, e.g. according to a pre-set or user-programmed algorithm.

The lighting assembly may be configured to automatically reduce the amount of light generated by the light source when the power in the energy storage means reaches a lower threshold. This may prolong the lit period of the assembly during a desired period of illumination, e.g. night time.

Certain preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: -7 -Figure la shows a perspective view of a solar-powered lighting assembly in accordance with an embodiment of the present invention.

Figure 1 b shows an exploded perspective view of the solar-powered lighting assembly of Figure la.

Figure 2a shows a side cross-sectional schematic of a light guide panel in accordance with an embodiment of the invention, showing the transmission of ambient light.

Figure 2b shows a side cross-sectional view of a light guide panel in accordance with the embodiment of Figure 2a, showing the transmission of light generated by an LED.

Figure 3a shows a front view of a road sign incorporating a solar-powered lighting assembly in accordance with an embodiment of the invention.

Figure 3b shows a side cross-sectional schematic view of the road sign of Figure 3a, showing the transmission of ambient light into the solar-powered lighting assembly.

Figure 3c shows a side cross-sectional schematic view of the road sign of Figures 3a and 3b, showing the transmission of generated light from an LED.

Figure 4a shows a path light incorporating a solar-powered lighting assembly in accordance with a further embodiment of the present invention.

Figure 4b shows a perspective view of a path lined with a plurality of path lights according to the embodiment depicted in Figure 4a.

Figures la and lb show a solar-powered lighting assembly 102 comprising a light-dispersing structure in the form of a light guide panel 104, a photovoltaic cell array 106, a base element 108 containing a controller 110 and a battery 112. Around the edges of the light guide panel 104 are disposed four LED arrays 114 each comprising a plurality of LEDs 114a. -8 -

The light guide panel 104 is provided with etched lines 116 on its upper surface. For clarity, the etched lines are not shown in Figure la. The LED arrays 114 and the photovoltaic cell array 116 are connected to the controller 110 and the battery 112 via electrical connections (not shown).

The base element 108, the photovoltaic cell array 106, and the light guide panel 104 are arranged in a stacked arrangement, with the base element 108 at the bottom, the photovoltaic cell array 106 in the middle, and the light guide panel 104 on top. The light guide panel 104 is made of a transparent thermoplastic. Ambient light incident on the top surface 104a of the light guide panel 104 is transmitted through the light guide panel 104 to the photovoltaic cell array 106. Accordingly, the photovoltaic cell array 106 is able to generate electrical energy from ambient, especially solar light.

The controller 110 determines how the energy generated by the photovoltaic cell array is used or stored. In accordance with the present embodiment, the energy can either be stored in the battery 112, used to light the LEDs 114a in the LED arrays 114, or a combination of both. In other embodiments, an external connection to an electricity grid may be provided to provide the additional option of selling energy to the grid.

In accordance with the present embodiment, the controller 110 is configured to store the electrical energy generated by the photovoltaics when ambient light is present (e.g. above a threshold level). The controller 110 is also configured to cause the energy in the battery to be used to light the LEDs 114a in the LED arrays 114 when the ambient light level drops below a threshold level. When it is determined by the controller 110 that the ambient light level has dropped such that the LEDs 114a need to be powered, energy from the battery 112 is used to light the LEDs 114a, and the light emitted from the LEDs 114a is transmitted through the light guide panel 104.

As the light propagates from the LEDs 114a, it is incident upon the front 104a or back 104b surface of the light guide panel 104. For a light guide panel having smooth front and back surfaces, the light would typically be totally internally -9 -reflected. However, the light guide panel 104 is provided with etched lines 116 on its front surface 104a. When the light generated by the LEDs 114a is incident on one of these etched lines 116, the light is refracted by the surface of the etched line 116 such that a substantial portion of the light is refracted out of the light guide panel 104. Accordingly, the light that is refracted outwards of the lighting assembly 102 illuminates the surroundings.

The transmission of light through the light guide panel 104 is shown in more detail in Figures 2a and 2b. In the present embodiment, the light guide panel has lines 116 (shown here in cross-section) etched into the front surface 104a. The back surface 104b is planar.

As shown in Figure 2a, when ambient light is incident on the upper surface 104a of the light guide panel 104, the light is admitted to the light guide panel 104 via the front surface 104a. The light is transmitted through the light guide panel 104 to the back surface 104b. The light then passes through the back surface to the photovoltaic cell array 106. If the light is incident on one of the etched lines 116, the light may be slightly refracted as it passes through the surface 104a, but still reaches the back surface 104b, where it is transmitted through to the photovoltaic cell array 106. In this manner, ambient light is able to reach the photovoltaic cell array 106 to generate energy.

Figure 2b shows the light guide panel 104 when the LED array 114 is illuminated. Light is transmitted from the LEDs 114a along the length of the light guide panel 104. As can be seen in the Figure, when a light ray is incident on the back surface 104b of the light guide panel 104, it is totally internally reflected, and is then transmitted in the direction of the upper surface 104a. If the light is incident on one of the etched lines 116, due to the angle of the surface created by the etched line 116, rather than being totally internally reflected again, the light is refracted out of the light guide panel to the surroundings. The light may be totally internally reflected a number of times from the back surface 104b and planar portions of the front surface 104a before it is incident on an etched line 116 and refracted out of the light guide panel 104. The effect of this light-dispersing structure is that light from the edge-mounted LEDs 114a is transmitted out of the structure 104 and into the surrounding environment.

Figure 3a shows a road sign 302 incorporating a solar-powered lighting assembly in accordance with an embodiment of the present invention. The road sign 302 is in the configuration of a standard circular UK road sign, having an outer annular portion 304, and an inner circular portion 306 depicting an image 308 for imparting information to a road user. The components of the solar-powered lighting assembly are shown in the cross-sectional schematics of Figure 3b and Figure 3c.

The road sign 302 and lighting assembly comprise a light guide panel 310, and photovoltaic cells 312 positioned underneath the circular outer portion 304 of the road sign 302. An LED array 314 is provided around the circumference of the light guide panel 310. Behind the light guide panel 310 and photovoltaic cell array 312 is a rear casing 316 containing a controller 318 and a battery 320.

On the front of the light guide panel 310 is a pattern of etched dots 322 covering the entire surface of the light guide panel. Overlaid on the front surface of the light guide panel 310 is an adhesive, translucent display sheet 324 covering the central portion 306 of the road sign 302. The sheet 324 has the road sign image 308 printed on it. An adhesive display sheet 326 is also provided over the outer portion 304. In this embodiment, the sheet 326 is substantially transparent, and tinted red in colour, so that when it is backlit by light emitted from the light guide panel 310 it appears red. The display sheet 326 permits transmission of a sufficient amount of ambient light to the photovoltaic cells 312 in order to supply adequate energy for lighting the LEDs 314.

Figure 3b shows the incidence of ambient light on the road sign. The ambient light is indicated by arrows 328. The ambient light passes through substantially transparent display sheets 326, and then is transmitted through the light guide panel 310 in a manner similar to that described with respect to Figure 2a. The light is then transmitted to the photovoltaic cells 312. The photovoltaic cells use the ambient light to generate energy which is stored in the battery 320.

The controller 318 determines whether the ambient light level has dropped to a sufficiently low level that it is necessary to light the road sign 302 to enable it to be read by road users. This determination is made from the voltage across the photovoltaic cells 312. A higher the voltage across the photovoltaic cell indicates a higher light level. Accordingly, by determining when the voltage drops a threshold value, it can be determined that the ambient light level is low enough to warrant lighting the road sign 302.

When the light level has dropped, energy from the battery 320 is used to light the LED array 314. The transmission of the light generated by the LED array 314 is shown in Figure 3c. The light is transmitted through the light guide panel 310 and emitted from the front surface of the light guide panel 310 in a manner similar to that described with regard to Figure 2b. Light emitted from the LED array 314 and may be totally internally reflected one or more times as it is transmitted through the light guide panel 310. When the generated light is incident on one of the etched dots of the pattern of etched dots 322, the angle of the surface resulting from the etching causes the light to be refracted out of the light guide panel 310 and transmitted through the translucent display sheets 324 and 326. In this manner, the display sheets depicting the image and colours of the road sign 302 are backlit by the light guide panel 310, improving their visibility to road users.

Figure 4a shows a floor level light 402 for lighting a path, incorporating a solar-powered lighting assembly according to a further embodiment of the present invention. The path light comprises a main casing 404 containing a controller 406 and a battery 408. A light guide panel 410 is provided in a recessed portion on the top of the path light 402. Around the edge of the recessed portion there is a first array of photovoltaic cells 412a and beneath the light guide panel is a second array of photovoltaic cells 412b. The photovoltaic cells are electrically connected to the controller 406 and the battery 408. The light guide panel 410 is transparent and is provided with a pattern of etched dots on the surface (omitted from Figure 4a for clarity). Light is admitted to the photovoltaic cells 412b via the light guide panel 410 in a manner to that described previously with regard Figures 2a and 3b. Energy is thereby generated and stored in the battery 408.

When it is determined by the controller 406 the path light should be illuminated, energy from the battery 408 is used to generate light using light-emitting phosphor strips 414 lining the recessed portion of the path light, i.e. around the edge of the light guide panel 410. Light emitted from the phosphor strips 414 is transmitted through the light guide panel 410 and refracted via the pattern of etched dots from the front surface of the light guide panel 410 in the manner described previously with regard to Figures 2b and 3c.

Figure 4b shows the use of a plurality of path lights 402 to line a path 416. As the path lights 402 generate and store energy from ambient light, each path light is a self-contained unit that does not require power from an electricity grid. Accordingly, the path lights can be used advantageously in poorly lit areas to replace or supplement street lighting without requiring any connection to the electricity grid.

Many other uses for such a path light 402 could be envisioned. As a few non-limiting examples, for lighting roads, pathways, or shopping precincts, or as decoration in entertainment venues, or for runway lighting.

Although only a few example embodiments of the present invention have been described, it will be appreciated that many variations are possible within the scope of the invention. A solar-powered lighting assembly in accordance with the present invention may be advantageous in any circumstance where it is desirable to provide lighting, in particular where space is limited, or where connection to an electricity grid is difficult or undesirable.

Claims

Claims: 1. A solar-powered lighting assembly comprising: a photovoltaic arrangement; and an illuminating arrangement comprising: at least one light source; and a light-dispersing structure arranged over at least a portion of the photovoltaic arrangement; wherein the light-dispersing structure is configured to admit ambient solar light to the photovoltaic arrangement and to redirect and disperse light from the light source out of the solar-powered lighting assembly.

A solar-powered lighting assembly as claimed in claim 1, wherein the light-dispersing structure comprises a light guide panel.

A solar-powered lighting assembly as claimed in claim 1 or 2, wherein the lighting assembly or the light-dispersing structure comprises a solar concentrator.

4. A solar-powered lighting assembly as claimed in any of claims 1, 2 or 3, wherein the light-dispersing structure is translucent.

A solar-powered lighting assembly as claimed in any preceding claim, wherein the light-dispersing means is transparent.

A solar-powered lighting assembly as claimed in any preceding claim, wherein the light-dispersing structure is transparent at visible wavelengths and/or at wavelengths suitable for generating energy using the photovoltaic arrangement.

A solar-powered lighting assembly as claimed in any preceding claim, wherein the light-dispersing structure comprises light dispersing elements arranged to reflect, refract, diffract, or otherwise direct light out of the light-dispersing structure.

8. A solar-powered lighting assembly as claimed in any preceding claim, wherein the light-dispersing elements are provided on the front and/or back surfaces of the light-dispersing structure. 10. 11. 12. 13. 14. 15. 16.

A solar-powered lighting assembly as claimed in any preceding claim, wherein the light-dispersing elements comprise raised or recessed dots, lines and/or patterns.

A solar-powered lighting assembly as claimed in any preceding claim, wherein the light-dispersing elements have been created using laser or mechanical etching, or screen printing.

A solar-powered lighting assembly as claimed in any preceding claim, wherein the photovoltaic arrangement comprises a plurality of photovoltaic cells.

A solar-powered lighting assembly as claimed in any preceding claim, comprising two or more light sources, wherein each light source emits light that is a different colour from light emitted by at least one other light source.

A solar-powered lighting assembly as claimed in any preceding claim, wherein the light source comprises a plurality of light emitting diodes.

A solar-powered lighting assembly as claimed in any preceding claim, wherein at least some of the light source(s) is/are mounted at the edge of the light-dispersing structure.

A solar-powered lighting assembly as claimed in any preceding claim, wherein at least some of the light source(s) are embedded in the light-dispersing structure, and/or provided behind the light-dispersing structure.

A solar-powered lighting assembly as claimed in claim 15, wherein the light source(s) are arranged so as to cover less than half the area of the light-dispersing structure.

17. A solar-powered lighting assembly as claimed in any preceding claim, wherein all or substantially all of the photovoltaic arrangement is covered by the light-dispersing structure.

18. A solar-powered lighting assembly as claimed in any preceding claim, wherein the light-dispersing structure has a portion that covers or is covered by a display article so that the light dispersing structure illuminates the display article.

19. A solar-powered lighting assembly as claimed in any preceding claim, wherein the solar-powered lighting assembly comprises energy storage means.

20. A solar-powered lighting assembly as claimed in any of claims 1 to 19, wherein the lighting assembly is self-contained and entirely self-powered.

21. A solar-powered lighting assembly as claimed in any preceding claim, wherein the lighting assembly is configured to switch off the light source while the energy storage means is being charged in the presence of ambient light.

22. A solar-powered lighting assembly as claimed in any preceding claim, wherein the lighting assembly is configured to power the light source when ambient light levels drop.

23. A solar-powered lighting assembly as claimed in any preceding claim, wherein the light source is configured to emit light at predetermined times.

24. A solar-powered lighting assembly as claimed in any preceding claim, wherein the lighting assembly comprises a programmable controller to allow the lighting assembly to be configured to power the light source at chosen times programmed into the controller.

25. A solar-powered lighting assembly as claimed in any preceding claim, wherein the lighting assembly comprises a processor having an algorithm which checks the real time and adjusts the light output of the light source depending on the real time.

26. A solar-powered lighting assembly as claimed in any preceding claim, wherein the lighting assembly is configured to automatically reduce the amount of light generated by the light source when the power in the energy storage means reaches a lower threshold.

27. A solar-powered lighting assembly as claimed in any preceding claim, further comprising one or more proximity sensors and/or a connection for receiving data.