EP4479715A1

EP4479715A1 - Casing for irradiance sensors

Info

Publication number: EP4479715A1
Application number: EP23706120.5A
Authority: EP
Inventors: Hesan ZIAR; Victor Arturo MARTINEZ LOPEZ; Ana Laura ROMERO OLVERA; Olindo ISABELLA
Original assignee: Technische Universiteit Delft
Current assignee: Technische Universiteit Delft
Priority date: 2022-02-17
Filing date: 2023-02-14
Publication date: 2024-12-25
Also published as: NL2030982B1; WO2023158302A1

Abstract

The present invention is in the field of a sensor for measuring light, in particular of measuring solar irradiance on a planar surface, more in particular a sensor designed to measure the solar radiation flux density such as from the hemisphere above within a limited wavelength range, a casing for such a sensor, a sensor comprising said casing, and a PV-module or PV-system comprising said sensor.

Description

Casing for irradiance sensors

FIELD OF THE INVENTION

The present invention is in the field of a sensor for measuring light, in particular of measuring solar irradiance on a planar surface, more in particular a sensor designed to measure the solar radiation flux density (either spectrally resolved or integrated) such as from the hemisphere above within a limited wavelength range, a casing for such a sensor, a sensor comprising said casing, and a PV-module or PV-system comprising said sensor.

BACKGROUND OF THE INVENTION

A pyranometer is a type of actinometer used for measuring solar irradiance on a planar surface. It is designed to measure the solar radiation flux density (W/m²) from the hemisphere above. A typical pyranometer does not require any power to operate. Typically a limited wavelength of operation is used, such as in a range 300 nm (UV-light) to 3000 nm (infrared). The name pyranometer stems from the Greek. Typically irradiance measurements with different degrees of spectral sensitivity will be obtained. As the earth rotates and the pyranometer is typically fixed, the sunlight angle of incidence may vary. The pyranometer may be adapted to correct for such variations. Typically thermopile technology and silicon semiconductor technology may be used to construct a pyranometer (ISO 9060). A thermopile pyranometer typically has a connector with a connection cable, a pyranometer under at least one glass domes, a black detector surface, a sun screen, a heat sink, a desiccant indicator, and positioning means. A thermopile pyranometer is adapted to calculate irradiation from a differential measure between the temperature of the black sectors being present therein, exposed to the sun, and the temperature of the white sectors, which white sectors are not exposed to the sun. Such makes these sensors sensitive to temperature influences, such as due to heating of the sensor itself. The thermopile generates a small voltage in the order of 10 pV (microvolts) per W/m². The pyranometer may also be a photovoltaic pyranometer, such as a silicon photodiode, making use of the photoelectric effect to convert light into an electric current. The wavelength range of such photodiodes is somewhat more limited, such as to 400 nm and 1100 nm. The conversion is sensitive to temperature changes. The raise in current produced by the change in temperature may be ±0,1% per degree K. The PV pyranometer typically comprises a housing, the photodiode, an output circuit, signal conditioning electronics, and optical elements such as a diffuser or optical filters. The current generated by the photodiode is considered to be directly proportional to irradiance. It may function as a reference cell. So pyranometers may be more or less sensitive to light, or a part of the spectrum thereof, apart from inherent sensitivity issues such as diffraction light.

A pyranometer may have additional sensors, such as for temperature, wind speed, etc. A pyranometer typically requires calibration before and during use, e.g. using IEC 60904-4 or IEC 60904-2.

The applicant recently developed an improved albedometer, which albedometer is specifically suited for use as a pyranometer. It is adapted to resolve light, which may be direct sun light or reflected light. In this respect reference can be made to patent application WO2021/162544 (Al), which document and its content is incorporated by reference. https://www. deltaohm , com/wp- content/uploads/document/DeltaOHM_LPPYRAQ3_Class_Cjpyranometer_manual_ENG.pdf shows details of a classical pyranometer. Doi: 10.1016/J.ENCONMAN.2016.10.007, Vol. 129, p. 344-353 relates to a study is intended to design, manufacture, and modelling an inexpensive pyranometer using a thermoelectric module. The governing equations relating the solar intensity, output voltage, and ambient temperature have been derived by applying the mathematical and thermodynamic models. According to the thermodynamics modelling, the output voltage is a function of solar intensity, ambient temperature, internal parameters of thermoelectric module, convection and radiation coefficients, and geometrical characteristics of the setup. Moreover, the solar intensity can be considered as a linear function of voltage and ambient temperature within an acceptable range of accuracy. The pyranometer has a closed perfectly dome-shaped casing.

It is noted that solar cell outputs show nontrivial variation with changing spectra. This may especially be the case for multi -junction solar cells, due to their increased spectrum sensitivity from current mismatch effects. Therefore, information about incoming solar spectrum is desired in order to accurately determine the yield of solar cells or modules and to optimize said yield.

The present invention therefore relates to an improved pyranometer, which solves one or more of the above problems and drawbacks of the prior art, providing reliable results, without jeopardizing functionality and advantages.

SUMMARY OF THE INVENTION

It is an object of the invention to overcome one or more limitations of the prior art and provides an improved pyranometer, which are less sensitive to changes in temperature, are more accurate, wherein a chance of overheating is reduced, and which provide passive cooling. Thereto a pyranometer is provided, comprising at least one solar irradiance sensor, such as the albedometer of the present inventors, and a casing, wherein the at least one solar irradiance sensor is provided in the casing, in particular on a support in said casing, more in particular on a support which is provided at a bottom section of the casing, wherein the casing comprises at least one fin extending outwards, in particular at least four fins, wherein the at least four fins are substantially evenly divided over a circumference of the casing. Fins are defined as surfaces that extend from an object, or part of said object, in this case the casing, which increase the rate of heat transfer to or from the environment by increasing convection. Likewise inverted fins (cavities) may be considered, which inverted fins are considered to be covered by the scope of the present claims. Open cavities are defined as the regions formed between adjacent fins. These cavities can be utilized to extract heat from the present casing. Hence the term fin is considered to relate to the extending surface, or likewise to the open cavity, or a combination thereof.

The present casing of the pyranometer in particular limits heating of the irradiance sensor. For instance, when illuminated directly from the top (90 °tilt) for 15 minutes with 800 W/m² the present pyranometer shows 2 °C less heating compared to a pyranometer with a casing without fins. When illuminated directly under an angle (60 °tilt) for 15 minutes with 800 W/m² the present pyranometer shows 5 °C less heating compared to a pyranometer with a casing without fins.

In a second aspect the present invention relates to a casing for the present pyranometer, in particular wherein the casing is partially or fully 3D-printed, or made by using a mould, or made by milling. The casing may equally well be used for other sensors or the like, such as a spectroradiometer.

In a third aspect the present invention relates to a sensor requiring thermal management comprising a casing according to the invention, and the sensor, the casing protecting the sensor from heating, in particular from overheating.

In a fourth aspect the present invention relates to a product comprising the present pyranometer, wherein the product is selected from a PV-module, a PV-system, a meteorological sensor, a climatological sensor, a building sensor, and a photovoltaic power station sensor. The product complies to IEC 61724-1 :2017. The product in particular relates to a pyranometer which is installed in-plane with the product.

Advantages of the present description are detailed throughout the description.

DETAILED DESCRIPTION OF THE INVENTION

In an exemplary embodiment of the present pyranometer the at least one solar irradiance sensor comprises silicon, such as a photodiode, or a thermopile sensor.

In an exemplary embodiment of the present pyranometer the casing comprises at least one opening, in particular at a top side thereof and/or at a bottom side thereof, wherein the at least one solar irradiance sensor is provided in said opening, wherein the opening may be covered with an optically transparent material, or in particular wherein the opening is covered with an opaque material, such as for Lambertian scattering of light. The optically transparent material can be either flat or have sphere shape.

In an exemplary embodiment of the present pyranometer the at least one solar irradiance sensor is provided in the casing, in particular on a support in said casing, more in particular on a support which is provided at a bottom section of the casing. The support may be part of a central part of the casing.

In an exemplary embodiment of the present pyranometer the casing comprises a top section, in particular a bottom section, and optionally a middle section, in particular wherein sections are detachably connected. When this casing is used for an irradiance sensor (not being an albedometer), then one top section may be enough.

In an exemplary embodiment of the present pyranometer the top section is substantially dome shaped, and/or wherein the bottom section is substantially dome shaped.

In an exemplary embodiment of the present pyranometer the top section and/or bottom section are substantially hollow.

In an exemplary embodiment of the present pyranometer the at least one fin is provided is parallel to a longitudinal of the dome.

In the present pyranometer each fin individually protrudes from a central part of the casing to a circumference of the casing. In an exemplary embodiment of the present pyranometer a space between two adjacent fins increases from one end of the adjacent fins to another end of the adjacent fins, in particular increases from a centre of the pyranometer to the circumference thereof.

In an exemplary embodiment of the present pyranometer the top section comprises at least one fin, and wherein the bottom section comprises at least one fin.

In an exemplary embodiment the present pyranometer comprises an electronic controller inside the casing.

In an exemplary embodiment of the present pyranometer a cross-section of the casing is selected from circular, ellipsoidal, and multigonal, such as hexagonal, octagonal, and decagonal.

In an exemplary embodiment the present pyranometer comprises at least one electrical board, in particular provided inside the casing, wherein the at least one electrical board is selected from a power board, and from an interface circuit. For example, inside the casing one may have two electrical boards (or levels): one is what is referred to as a power board (or sensor level) which has the sensors The other is a control board (or control level), which has the control IC and the interface circuit. For the case of albedometer, two sensor boards and one control board may be provided.

In an exemplary embodiment of the present pyranometer the casing comprises at least one connector, such as for connecting to a holder, for electrically connecting to a controller, such as a serial connector, such as RS232, and RS458, and optionally comprising a wireless communication transmitter, such as wifi.

In an exemplary embodiment of the present pyranometer the casing comprises 360/n fins, wherein n is from 6-90, in particular from 12-36, more in particular from 15-24, and/or wherein fins are evenly divided over a circumference of the casing.

In an exemplary embodiment of the present pyranometer the at least one fin comprises a core, wherein the core is made of a thermal conducting material, in particular from a metal.

In an exemplary embodiment of the present pyranometer the casing provides convection of air surrounding said casing, in particular natural convection.

In an exemplary embodiment of the present pyranometer the casing is made of a polymer, in particular a thermal conducting material, such as a thermoset polymer, or of a metal, such as aluminium, or copper. Two exemplary versions comprise aluminium, of which one is coloured white and the other natural (grey) to observe the thermal cooling effect of both.

Embodiments and details of the present pyranometer are given below.

In an exemplary embodiment of the present pyranometer the at least one solar irradiance sensor is a geometrically and spectrally resolved albedometer for a bifacial PV-module comprising a spectrophotometer for spectrally resolving light comprising at least two arrays of n*m size comprising at least two spaced apart solar cells, each solar cell adapted to receive direct or reflected solar light, respectively, and providing an electrical signal in response thereto, and each individually adapted to receive a bandwidth of wavelength, wherein the bandwidth is < 300 nm, wherein bandwidths do not overlap, wherein n>l and m>3, at least one first array of the spectrophotometer receiving light in a first direction and at least one second array of the spectrophotometer receiving light in a second direction, wherein the first and second direction are opposite, a 3D image forming device, such as an optical camera, a LIDAR system, or a combination thereof, the 3D image forming device receiving an image in a second direction, and an electronic circuit for processing the individual electrical signals and for mapping spectrally resolved light and the 3D-image on top of one and another. In an alternative for a solar cell a photodiode or an irradiance sensor may be used; the term “solar cell” is therefore considered to encompass other variants as well, such as the ones mentioned,

In an exemplary embodiment the present pyranometer further comprises stored on the pyranometer a light intensity/response curve for each solar cell.

In an exemplary embodiment of the present pyranometer each solar cell is the same, and wherein each solar cell is provided with a filter for the respective bandwidth, or wherein each solar cell is adapted to respond to light within the bandwidth, or a combination thereof.

In an exemplary embodiment of the present pyranometer a central wavelength of a bandwidth of a first solar cell is 470+20 nm, or wherein a central wavelength of a bandwidth of a second solar cell is 980+20 nm, or wherein a central wavelength of a bandwidth of a third solar cell is 900+20 nm, or wherein a central wavelength of a bandwidth of a fourth solar cell is 850+20 nm, or wherein a central wavelength of a bandwidth of a fifth solar cell is 1170+20 nm, or wherein a central wavelength of a bandwidth of a sixth solar cell is 785+20 nm, or wherein a central wavelength of a bandwidth of a seventh solar cell is 705+20 nm, or wherein a central wavelength of a bandwidth of a eighth solar cell is 675+20 nm, or wherein a central wavelength of a bandwidth of a ninth solar cell is 630+20 nm, or wherein a central wavelength of a bandwidth of a tenth solar cell is 360+20 nm, or wherein a central wavelength of a bandwidth of a eleventh solar cell is 550+20 nm, or wherein a central wavelength of a bandwidth of a twelfth solar cell is 1050+20 nm, and combinations thereof.

In an exemplary embodiment of the present pyranometer the array comprises 3-12 solar cells, preferably 6-8 solar cells, each individually, and/or wherein solar cells are placed apart at a distance of >1 mm, such as 0.5-5 cm, and/or wherein solar cells have a size of 1*1 mm² to 10*10 cm². The array may be of any shape, such as triangular, rectangular, hexagonal, octagonal, circular, etc.

In an exemplary embodiment the present pyranometer further comprises stored on the pyranometer at least one spectral reflected light intensity distribution of a reflecting surface, and/or further comprises stored on the pyranometer at least one spectral light intensity distribution of incoming light, preferably a spectral light intensity distribution of every day of a year, more preferably a spectral light intensity distribution of every minute of every day of a year, preferably adapted for a given latitude.

In an exemplary embodiment the present pyranometer comprises an optical transparent casing, preferably wherein the spectrophotometer, and electronic circuit, are embedded in said casing, and/or a temperature controller for adjusting the pyranometer, and/or a location sensor, and/or a level sensor, and/or a mounting structure, and/or a connector, such as a USB connector, and/or a pressure sensor, and/or a timer, and/or at least one optical diffuser located over the at least one array.

In an exemplary embodiment of the present pyranometer each solar cell is individually adapted to receive low intensity light, preferably from 1-400 W/m², more preferably from 5-100 W/m², such as from 7-10 W/m².

In an exemplary embodiment of the present pyranometer the spectrophotometer, the 3D image forming device, and the electronic circuit are incorporated in the pyranometer.

The invention will hereafter be further elucidated through the following examples which are exemplary and explanatory of nature and are not intended to be considered limiting of the invention. To the person skilled in the art, it may be clear that many variants, being obvious or not, may be conceivable falling within the scope of protection, defined by the present embodiments.

SUMMARY OF THE FIGURES

Figs. la-c,2, 3a-b, 4a-b and 5 show details of the present invention.

DETAILED DESCRIPTION OF FIGURES

The figures are detailed throughout the description, and specifically in the experimental section below.

In the figures: 100 pyranometer

1 bubble inclinometer sensor

2 array of PV-cells

3 Internal circuitry

4 Casing

5 fin

6 top section casing

7 bottom section casing

8 opening casing

9 middle section casing

10 connector holder

11 connector controller

12 optical element for the opening

13 sealant

Figure la shows a schematic top view of the invention, with the present pyranometer 100, in particular an albedometer, which may be considered as a back-to-back pyranometer, the casing 4, and the opening 8 in the casing. A space between fins increase from a top side of the casing towards a middle part of the casing.

Fig. lb shows a top view with the present fins 5 distributed evenly over a circumference of the casing, the bubble inclinometer sensor 1, as well as an array of PV-cells.

Fig. 1c shows a side view of the present pyranometer, with the longitudinal axis thereof indicated. Figure 2 shows a worked-open version of the present pyranometer, with Internal circuitry 3, a top section of the casing 6, a bottom section of the casing 7, a middle section of the casing 9, a connector for holding the pyranometer 10, and a connector for a controller 11.

Figure 3a shows an example of heating with 800 W/m² during 15 minutes under 90°, for a casing with fins, and for a casing without fins (3b). A difference in sensor temperature is 2K. It is noted that the difference in sensor temperature itself is reported, because this is the temperature that directly affects the readings (irradiance measurements), and has more impact on the life-time of the sensor than for example the casing temperature.

Figure 4a shows an example of heating with 800 W/m² during 15 minutes under 60°, for a casing with fins, and for a casing without fins (4b). A difference in sensor temperature is 1 ,8K. Figure 5, shows how the temperature increases for a pyranometer with a casing with fins (bottom line) and for one without fins.

Claims

1. Pyranometer, comprising at least one solar irradiance sensor, and a casing, the casing configured to protect the solar irradiance sensor from heating by passive cooling, wherein the casing comprises at least one fin extending outwards, in particular at least four fins, wherein the at least four fins are substantially evenly divided over a circumference of the casing, wherein each fin individually protrudes from a central part of the casing to a circumference of the casing.

2. Pyranometer according to claim 1, wherein the at least one solar irradiance sensor comprises silicon, such as a photodiode, or a thermopile sensor.

3. Pyranometer according to any of claims 1-2, wherein the casing comprises at least one opening, in particular at a top side thereof and/or at a bottom side thereof, wherein the at least one solar irradiance sensor is provided in said opening, in particular wherein the opening is covered with an optically transparent material, or in particular wherein the opening is covered with an opaque material, and/or wherein the at least one solar irradiance sensor is provided in the casing, in particular on a support in said casing, more in particular on a support which is provided at a bottom section of the casing.

4. Pyranometer according to any of claims 1-3, wherein the casing comprises a top section, in particular a bottom section, and optionally a middle section, in particular wherein sections are detachably connected, and/or wherein the top section is substantially dome shaped, and/or wherein the bottom section is substantially dome shaped, and/or wherein the top section and/or bottom section are substantially hollow.

5. Pyranometer according to any of claims 1-4, wherein the at least one fin is provided is parallel to a longitudinal of the dome, and/or wherein a space between two adjacent fins increases from one end of the adjacent fins to another end of the adjacent fins, in particular increases from a centre of the pyranometer to the circumference thereof.

6. Pyranometer according to any of claims 4-5, wherein the top section comprises at least one fin, and wherein the bottom section comprises at least one fin.

7. Pyranometer according to any of claims 1-6, comprising an electronic controller inside the casing.

8. Pyranometer according to any of claims 1-7, wherein a cross-section of the casing is selected from circular, ellipsoidal, and multigonal, such as hexagonal, octagonal, and decagonal.

9. Pyranometer according to any of claims 1-8, comprising at least one electrical board, in particular provided inside the casing, wherein the at least one electrical board is selected from a power board, and from an interface circuit.

10. Pyranometer according to any of claims 1-9, wherein the casing comprises at least one connector, such as for connecting to a holder, for electrically connecting to a controller, such as a serial connector, such as RS232, and RS458, and optionally comprising a wireless communication transmitter, such as wifi.

11. Pyranometer according to any of claims 1-10, wherein the casing comprises 360/n fins, wherein n is from 6-90, in particular from 12-36, more in particular from 15-24, and/or wherein fins are evenly divided over a circumference of the casing.

12. Pyranometer according to any of claims 1-11, wherein the at least one fin comprises a core, wherein the core is made of a thermal conducting material, in particular from a metal.

13. Pyranometer according to any of claims 1-12, wherein the casing provides convection of air surrounding said casing, in particular natural convection.

14. Pyranometer according to any of claims 1-13, wherein the casing is made of a polymer, in particular a thermal conducting material, such as a thermoset polymer, or of a metal, such as aluminium, or copper.

15. Casing for a Pyranometer according to any of claims 1-14, the casing configured to protect the solar irradiance sensor from heating by passive cooling, wherein the casing comprises at least one fin extending outwards, in particular at least four fins, wherein the at least four fins are substantially evenly divided over a circumference of the casing, wherein each fin individually protrudes from a central part of the casing to a circumference of the casing, in particular wherein the casing is partially or fully 3D-printed, or made by using a mould, or made by milling.

16. Sensor requiring thermal management comprising a casing according to claim 15, and the sensor, the casing protecting the sensor from heating, in particular from overheating.

17. Product comprising a Pyranometer according to any of claims 1-14, wherein the product is selected from a PV-module, a PV-system, a meteorological sensor, a climatological sensor, a building sensor, and a photovoltaic power station sensor.