NL2016814B1

NL2016814B1 - Device for measurement of direct sunbeam irradiance

Info

Publication number: NL2016814B1
Application number: NL2016814A
Authority: NL
Inventors: Mes Joop
Original assignee: Kipp & Zonen B V
Priority date: 2016-05-23
Filing date: 2016-05-23
Publication date: 2017-11-30

Abstract

A device is provided for measurement of direct sunbeam irradiance, the device comprising a hollow collimator body, an opening at a first end of the body for receiving direct sunbeam irradiance within the body and a sensor module provided at a second end of the body opposite to the first end. The sensor module comprises a sensor being mounted such on the sensor module that it is arranged for receiving sunbeam irradiance entering through the opening and being incident to the sensor. The opening provides a free passage for objects to the inside of the body. If dust can enter the collimator tube, the total area for the dust to settle is many times larger compared to the window of a conventional pyrheliometer. Furthermore, pollution settling at the inner wall of the collimator body has no effect to accuracy of any measurements, because such pollution does not obstruct incident sunbeams.

Description

P111802NL00

Title: Device for measurement of direct sunbeam irradiance

TECHNICAL FIELD

The aspect relates to the field of pyrheliometers.

BACKGROUND

As discussed on Wikipedia, a pyrheliometer is an instrument for measurement of direct beam solar irradiance. Sunlight enters the instrument through a window and is directed onto a thermopile which converts heat to an electrical signal that can be recorded. The signal voltage is converted via a formula to measure Watts per square metre. It is used with a solar tracking system to keep the instrument aimed at the sun. A pyrheliometer comprises a collimator tube, with the window provided at one end and the thermopile at another, opposite end. The collimator tube usually comprises baffles having narrow concentric openings. This allows for minimising stray light from reaching the thermopile, ensuring only direct sunlight irradiance reaches the thermopile and only irradiance of direct sunlight is measured.

SUMMARY

It is preferred to provide a pyrheliometer requiring less maintenance and less cleaning in particular. Conventional pyrheliometers comprise a window having a diameter of about 1,8 centimetres and an area of 2,7 square centimetres. Any particles and a multitude of particles in particular result in scattering of incident sunlight. Scattering of the sunlight results in direct irradiance of sunlight not reaching the sensor, which results in a measurement error. Therefore, conventional pyrheliometers require frequent cleaning of the window of the pyrheliometer. A device is provided for measurement of direct sunbeam irradiance, the device comprising a hollow collimator body, an opening at a first end of the body for receiving direct sunbeam irradiance within the body and a sensor module provided at a second end of the body opposite to the first end. The sensor module comprises a sensor being mounted such on the sensor module that it is arranged for receiving sunbeam irradiance entering through the opening and being incident to the sensor. The opening provides a free passage for objects to the inside of the body.

In conventional pyrheliometers, the window is provided for preventing objects, like dust and other polluting particles, from entering the collimator body. A reason for this is reduction maintenance effort when cleaning the pyrheliometer. Indeed, with a closed body, only the window needs to be cleaned in case of pollution. However, the window needs to be cleaned relatively often.

It is appreciated that if dust allowed to enter the collimator tube, the total area for the dust to settle is many times larger compared to the window. A collimator body having a length of about 20 centimetres and a diameter of approximately 4 centimetres has a total inner surface of about 270 square centimetres, 100 times larger than a window of conventional pyrheliometers. Furthermore, pollution settling at the inner wall of the collimator body has no effect to accuracy of any measurements, because such pollution does not obstruct incident sunbeams.

Certain particles may cover the sensor after a prolonged period in time, which requires cleaning of the inner parts of the collimator body, but this period will be longer than with convention pyrheliometers. As pyrheliometers may be located at isolated locations, this longer maintenance interval is an advantage.

An embodiment of the device comprising a diffuser provided in the device such that sunbeam irradiance entering through the opening and being incident to the sensor reaches the sensor via the diffuser.

An advantage of this embodiment is that part of irradiance incident to the diffuser and scattered by any pollution on the diffuser is, despite the scattering by the pollution, also scattered into the diffuser. At least part of the irradiance scattered into the diffuser may subsequently be passed onto the sensor. This reduces the sensitivity for soiling. It is noted this embodiment works better if the diffuser is provided closer to the sensor.

In another embodiment, the diffuser is provided in a layer covering the sensor. As indicated above, application of a diffuser works better if the diffuser is provided closer to the sensor. With the diffuser provided as a layer covering the sensor, the diffuser is provided very close. An intermediate layer may be provided, like glue or any material for adjustment of one or more optical indices may be provided.

In a further embodiment, the diffuser is opaque white. A white diffuser has an advantage to have substantially the same properties for all wavelengths within the visible spectrum.

In yet another embodiment, the opening is provided in cap releasably mounted to the first end of the body. An advantage is that the cap may be removed, allowing efficient cleaning of the inner side and parts of the collimator body.

Yet a further embodiment comprises at least one baffle having a concentric opening and the baffle being provided within the hollow part of the body, perpendicular to the central axis of the body.

In again another embodiment, the opening is provided in a cap releasably mounted to the first end of the body and the baffle is mounted to the cap, at a distance from the cap. This embodiment allows efficient removal of the cap and the one or more baffles, which facilitates convenient cleaning of the inner side and parts of the collimator body.

Again a further embodiment comprises at least one through hole between the first end of the body and the second end of the tube, the hole connecting the hollow inside of the body to the outside of the tube.

This embodiment facilitates release of at least some pollutants, either gaseous, liquid or solid, from the inner space of the collimator body.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will now be discussed in further details in conjunction with a drawing. In the drawing,

Figure 1: shows a pyrheliometer.

DETAILED DESCRIPTION

Figure 1 shows a pyrheliometer 100. The pyrheliometer 100 receives radiation 152 from the sun 150. The pyrheliometer 100 is arranged to measure direct sunbeam irradiance originating from the sun 150. To this end, the pyrheliometer 100 is provided with a cap 120 comprising an aperture 122, a collimator body 110 and a sensor module 140.

The collimator body 110 is provided as a tube, having in this embodiment a substantially cylindrical shape. The collimator body 100 is about twenty centimetres and preferably 19 centimetres long and preferably has an inner diameter between three and four centimetres and an outer diameter of four to five centimetres. In a preferred embodiment, the inner diameter is about 35 millimetres and the outer diameter is about 45 millimetres.

The cap 120 is arranged for covering a first end of the collimator body 110, in Figure 1 provided at the right. The cap 120 comprises an aperture 122. The aperture 122 preferably has a diameter of 2,5 centimetres and is provided concentrically in the cap 120. The aperture 122 is an opening that is not covered and permits entry of objects into the collimator tube 110. The cap 120 is releasably connected to the collimator body 110.

The connection between the collimator body 110 and the cap 120 may be provided by means of screws, threaded rods, for example protruding from the collimator body, and nuts, snap-fit connections, other, or a combination thereof.

In the collimator body 110, baffles 126 are provided. In this embodiment, the baffles 126 are discs that are provided concentrically within the collimator body. The baffles 126 are provided with concentric holes 128. In a preferred embodiment, the concentric holes 128, baffles apertures, decrease in diameter from the cap 120 towards the sensor module 140. The baffles 126 are in this embodiment connected to the cap 120 by means of multiple rods 124, at a distance from the cap 120. In the embodiment shown by Figure 1, the baffles 126 are provided relatively close to the cap 120.

In another embodiment, the baffles 126 are substantially evenly distributed over the length of the collimator body 110. An in yet another embodiment, the baffles are separated by concentric rings having an outer diameter substantially equal to and preferably slightly smaller than the inner diameter of the collimator body 110. In that embodiment, but also in other embodiments, the baffles 126 are not necessarily fixedly connected to the cap 120.

The sensor module 140 comprises a sensor 142 for detecting direct sunbeam irradiance, preferably in a quantitative way. The sensor 142 may be provided in any known and new way that sensors for pyrheliometers are provided. Adjacent to the sensor 142, a diffuser 144 is provided. The diffuser 144 diffuses, spreads out and/or scatters light incident to the diffuser 144.

As a results, sunbeam irradiance incident to the diffuser 144 is spread out over a larger part of the sensor 142 than only a smaller area of the diffuser 144 where the irradiance is received.

Spreading out or diffusion of incident sunbeam irradiance means that a larger, more homogeneous area is provided for sensing incident sunbeam irradiation by the sensor 142. This, in turn, makes the pyrheliometer less sensitive to pollution and pollution of the sensor 142 and the diffuser 144 in particular. A reason for this is that a dust particle on a front window of a convention pyrheliometer will result in scattering of most of the incident solar irradiation, for which reason it will not reach the sensor 142.

Incident solar irradiation scattered by a dust particle on the diffuser 144 will be scattered as well, but a substantial part will still enter the diffuser and reach the sensor 142. Furthermore and therefore, use of the diffuser 144 allows in this way for use of a smaller sensor 142 than used for conventional pyrheliometers, which allows for a faster response time of the pyrheliometer 100. A conventional sensor has a diameter of 1,5 centimetres, whereas use of a diffuser allows for the sensor 142 to have a diameter of approximately 0,1 centimetres or up.

It is noted a conventional pyrheliometer may also be equipped with a sensor having a smaller diameter, but this will require a much shorter collimator tube, which, in turn, will make aligning the conventional pyrheliometer to the sun much more difficult.

The diffuser 144 preferably comprises quartz, Teflon, PMMA or another suitable material, either a mineral, an organic polymer, other, or a combination thereof. Furthermore, additives may be added to the material or materials used in order to promote the opacity of the diffuser 144 and, optionally, for providing a colour other than white. The diffuser 144 is preferably provided as a disk having a diameter substantially the same as that of the conventional sensor 142 or slightly larger. The diffuser preferably has a thickness between 0,05 centimetres and 0,3 centimetres. The diffuser is preferably opaque, having a substantially white colour.

The sensor module 140 further comprises a signal processing module 146. The signal processing module 146 comprises electronics for amplifying a signal received from the sensor 142, for converting the signal to a digital signal, for communicating the digitised signal in accordance with a pre-determined communication protocol, for providing other processing of the signal received from the sensor 142 or a combination thereof. If external processing of the signal received from the sensor 142 is preferred, the signal processing module 146 may be omitted. The sensor module 140 further may comprise a cover 148 for covering the diffuser 144 and/or the sensor 142.

The cover 148 is arranged for repelling any pollution from the diffuser 144 and/or the sensor 142 to reduce the need for cleaning of the sensor module 140.

The collimator body 110 further comprises one or more through holes 112 provided along the length of the collimator body 110. The through holes 112 enable release of particles like dust and the like and liquid like rainwater from the inner space of the collimator body 110.

Expressions such as "comprise", "include", "incorporate", "contain", "is" and "have" are to be construed in a non-exclusive manner when interpreting the description and its associated claims, namely construed to allow for other items or components which are not explicitly defined also to be present. Reference to the singular is also to be construed in be a reference to the plural and vice versa.

In the description above, it will be understood that when an element such as layer, region or substrate is referred to as being “on” or “onto” another element, the element is either directly on the other element, or intervening elements may also be present.

Furthermore, the invention may also be embodied with less components than provided in the embodiments described here, wherein one component carries out multiple functions. Just as well may the invention be embodied using more elements than depicted in the Figure, wherein functions carried out by one component in the embodiment provided are distributed over multiple components. A person skilled in the art will readily appreciate that various parameters disclosed in the description may be modified and that various embodiments disclosed and/or claimed may be combined without departing from the scope of the invention.

Claims

A device for measuring a direct sunburst radiation, the device comprising: a hollow collimator body; an opening at a first end of the body for receiving direct sun ray radiation into the body; A sensor module provided at a second end of the body, the sensor module comprising a sensor attached to the sensor module such that it is adapted to receive sunbeam radiation that enters through the aperture and impinges on the sensor; The opening offers a free passage of particles to the interior of the body.

The device of claim 1, further comprising a diffuser provided in the device such that sunbeam radiation entering through the aperture and incident on the sensor reaches the sensor via the diffuser.

Device as claimed in claim 2, wherein the diffuser is provided in a layer which covers the sensor.

Device as claimed in claim 2 or 3, wherein the diffuser is provided in direct contact with the sensor.

Device according to any of claims 2 to 4, wherein the diffuser is opaque white.

Device as claimed in any of the foregoing claims, wherein the opening is provided with a lid which is detachably connected to the first end of the body.

7. Device as claimed in any of the foregoing claims, further comprising at least one screen with a concentric opening and wherein the screen is provided in the hollow part of the body, perpendicular to the central axis of the body.

Device as claimed in claim 7, wherein: The opening is provided with a lid detachably connected to the first end of the body; and The screen is attached to the lid at a distance from the lid.

Device as claimed in any of the foregoing claims, wherein the sensor module is detachably attached to the collimator body.

The device of claim 7, wherein: the sensor module is releasably connected to the body; and The screen is detachably attached to the sensor module, at a distance from the sensor module.

The device of any preceding claim, further comprising at least one through hole between the first end of the body and the second end of the body, which hole connects the hollow interior of the body to the outside of the body.

Device as claimed in any of the foregoing claims, further comprising a sensor cover for protecting the sensor against any objects that enter the hollow interior of the body.