Heavy vehicles rolling on wet roads produce splash and spray clouds. These aerosols reduce the visibility of other drivers, contribute to a small, but quantifiable proportion of road traffic accidents and affect the operational capabilities of autonomous vehicles travelling near them. Even though knowing the physical properties of these aerosols is essential for testing and validating sensors for environment perception and recognition of autonomous vehicles, there is little information about them. In this work the physical characteristics of spray clouds produced by heavy vehicles rolling on wet asphalt were measured by optical methods. Time resolved droplet size, mass concentration, number density, light extinction and contrast attenuation parallel and perpendicular to the travelling direction of the vehicle were measured. Vehicle velocity, vehicle configuration and water depth were varied during the tests. Results show that the average droplet diameter ranges between 100 and 400 μm with maximum diameters of almost 4 mm. Mass concentration gamuts between 0,2 and 0,7 kg/m3 with peaks surpassing 1 kg/m3 while number density spans between 20 and 40 cm−3 and occasionally exceeds 100 cm−3. Light extinction can reach levels as high as 0,2 m−1 and contrast, evaluated from images, can reach values under 0,1. 

The Euramet.PR-K2.a comparison on spectral responsivity for the wavelength range 900 nm to 1600 nm, as described in this report, was carried out to establish the degree of equivalence for the participating European laboratories with respect to the Key Comparison Reference Value (KCRV) of the CCPR-K2.a-2003 comparison. Seven laboratories, including pilot and link laboratory, participated. The comparison was piloted by VSL (Netherlands). Both VSL and NPL (UK) act as link laboratories to the CCPR-K2.a-2003 comparison. Most laboratories show a DoE within 1 % from the CCPR KCRV for almost the full wavelength range, with some slightly larger differences mostly above 1450 nm. One laboratory shows larger deviations, up to 3%. This report provides an overview of the comparison, a description of the characterization of the reference detectors, the data-analysis, participant results and their uncertainties and the degree of equivalence of participating laboratories with the CCPR KCRV. The full Technical Reports of the participants are included in the Appendix of the comparison report. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA). 

For the solar energy industry to increase its competitiveness, there is a global drive to lower the cost of solar-generated electricity. Photovoltaic (PV) module assembly is material-demanding, and the cover glass constitutes a significant proportion of the cost. Currently, 3-mm-thick glass is the predominant cover material for PV modules, accounting for 10%–25% of the total cost. Here, we review the state-of-the-art of cover glasses for PV modules and present our recent results for improvement of the glass. These improvements were demonstrated in terms of mechanical, chemical and optical properties by optimizing the glass composition, including addition of novel dopants, to produce cover glasses that can provide (i) enhanced UV protection of polymeric PV module components, potentially increasing module service lifetimes; (ii) re-emission of a proportion of the absorbed UV photon energy as visible photons capable of being absorbed by the solar cells, thereby increasing PV module efficiencies and (iii) successful laboratory-scale demonstration of proof of concept, with increases of 1%–6% in Isc and 1%–8% in Ipm. Improvements in both chemical and crack resistance of the cover glass were also achieved through modest chemical reformulation, highlighting what may be achievable within existing manufacturing technology constraints. © 2020 The Authors.

Utvinning av solenergi genom solceller är en lovande teknik för att öka andelen förnyelsebara energikällor både nu och i framtiden. Glas till solceller är en betydande del av kostnaden och en nödvändighet att utveckla för att öka livslängden och minska priset per utvunnen watt. I LIMES har man studerat dels att tillsätta optiskt aktiva komponenter som absorberar skadligt UV ljus och samtidigt konverterar det till synligt ljus som i sin tur kan konverteras till energi i solcellerna. Därmed är vinsten tvåfaldig, ökar både livslängden och effektiviteten med upp till 4%. Vidare har det studerats hur man kan optimera de mekaniska och kemiska egenskaperna av glas för att kunna öka den mekaniska och kemiska livslängden, detta genom att optimera glassammansättningen. Man har inom projektet visat att motstånd mot sprickbildning av en ny sammansättning ökar med en faktor 3 och att den kemiska resistensen ökar med en faktor 4. Termo-kemisk härdning av glas har demonstrerats i labskala som ger upphov till minst lika stor härdningsgrad samt ökar motstånd mot sprickbildning med en faktor 2. Det möjliggör användning av tunnare glas och därmed betydligt lättare solceller. Glasytans sammansättning modifieras signifikant genom att öka halten aluminiumoxid och det ger upphov till de förbättrade egenskaperna. Den termo-kemiska behandlingen ökar vattens kontaktvinkel mot glasytan vilket bidrar till ett självrengörande glas. Multifunktionella ytor på glas som är både antireflektiva och självrengörande har studerats genom två olika angreppssätt, nanostrukturerad ytmodifiering och porösa antireflektiva beläggningar med fotokatalytisk nedbrytningsförmåga. Nanostrukturerade glasytor ger upphov till en ökad ljusspridning och kan på så vis effektivt guida ner diffust ljus till solceller och samtidigt ändra vattens kontaktvinkel mot glaset. LIMES-koncepten har demonstrerats genom kvantitativa mätningar och tillverkande av små kiselsolcellsmoduler. Projektet har stått för att öka potentialen för kommersialisering ifrån TRL (Technology Readiness Level) nivå 2-4 till 4-6. Man undersöker i det närmaste hur man kan skala upp planglastillverkning för att kunna ta nästa steg mot kommersialisering.

Extraction of solar energy through solar cells is a promising technology for increasing the share of renewable energy sources, both now and in the future. Glass for solar cells is a significant part of the cost, and a necessity to develop to increase life expectancy and reduce the cost per watt recovered. In the LIMES project have adding optically active components been studied, these absorb harmful UV light and simultaneously converts those UV photons into visible light, which in turn can be converted into energy in solar cells. Thus, the profit is twofold, increasing both the lifetime and efficiency by up to 4%. Further, it has been studied how to optimize the mechanical and chemical properties of glass by optimizing the glass composition in order to increase the mechanical and chemical lifetime. It has shown that resistance to cracking of the new composition increases by a factor of 3 and that the chemical resistance is increased by a factor of 4. Novel thermo-chemical strengthening of glass has been demonstrated in the lab and giving rise to at least equal strengthening level and increases the crack resistance by a factor of 2. It enables the use of thinner glass and thus significantly lighter photovoltaic modules. In the thermo-chemical strengthening process, the glass surface composition is modified significantly by increasing the content of aluminum oxide and thus gives rise to improved properties. The thermo-chemical treatment increases the glass surface contact angle of water, which contributes to a self-cleaning glass. Multifunctional glass surfaces that are both anti-reflective and self-cleaning have been studied by two different approaches, nanostructured surface modification and porous antireflective coatings with photocatalytic degradation ability. Nanostructured glass surfaces gives rise to an increased light scattering and can thus effectively guide diffused light to the solar cells and simultaneously change the glass contact angle with water. The LIMES-concept has been demonstrated by quantitative measurements and manufacturing of small silicon photovoltaic modules. The project has significantly increased the potential for commercialization by increasing the TRL (Technology Readiness Level) level from 2-4 to 4-6. Investigations on how to scale up manufacturing flat glass in order to take the next step towards commercialization is on-going.

Antireflective coatings on glass have increasing applications, on e.g. cover glass of PV modules, display glass, spectacle lenses or window glazing’s. Sol-gel derived mesoporous coatings can be tuned both in terms of porosity and thickness, thus allowing tuning of the refractive index. Additionally, the sol-gel approach is bottom-up, which facilitates easy upscaling. In the current work we present dip-coated mesoporous silica coatings of different pore orientation and film thickness prepared on microscope glass slides and silicon wafers. The silica coatings were derived from TEOS (tetraorthosilicates) mixed with ethanol and diluted HCl. Hexagonal and cubic pore ordering of the thin films with a pore size in the range of 5-10 nm were obtained. The thin films were characterized in terms of non-contact profilometry, stylus profilometry,  nanohardness, scratch resistance, UV-Vis-NIR transmittance and UV-Vis-NIR reflectance. The thicknesses of the studied films varied from 100 nm up to several hundreds of nm without jeopardizing the film homogeneity. All the mesoporous films exhibited higher transmittance than the uncoated glass substrate. The film with hexagonal pore orientation has a somewhat higher nanohardness than the cubic one, however,  no difference was found in the scratch resistance for the films with different pore orientations.

Accurate temperature measurements in flow lines are critical for many industrial processes. It is normally more a rule than an exception in such applications to obtain water flows with in-homogenous temperature distributions. In this paper a number of comparisons between different Pt-100 configurations used to measure the average temperature of water flows with in-homogenous temperature distributions were studied. By using a custom-built flow injector a water flow with a hot water layer on top of a cold water layer was created. The temperature difference between the two layers was up to 32K. The average temperature from a custom-built multiple Pt-100 sensors (consisting of 9 Pt-100) was used as reference. Our study shows that for a 32 K temperature difference between the two layers the deviation to the references decreased from about 4 K to 1 K by taking the average temperature of 4 Pt-100 mounted in the same pipe plane (90° apart) instead of a single Pt-100. Overall the deviation to the temperature reference for the average temperature of 4 Pt-100 is remarkable lower than the deviation for a single Pt-100 under the same conditions. In addition the immersion depth of a single Pt-100 was also investigated at three different water temperatures.

This project studies whether or not a digital camera can be used to evaluate colour difference or colour contrast. When characterizing a test object that changes colour over time it is not always possible to do a normal colour measurement with a spectroradiometer. The alternative could be to use film or rapid fire photography to record the changes and extract the colour data from the digital information. This project involves development of a method where spectroradiometric data of a colour chart is compared to digital data taken from photos and film of the same colour chart using Photoshop. In each measurement 22 colours have been evaluated by calculating the colour difference between a direct spectroradiometric measurement of a single colour and data taken from Photoshop of that same colour. The data is compared in the CIELAB colour space using the ?E94 metric which should faithfully represent how the human eye perceives colour difference. Three sets of measurements are made .Two sets where the spectroradiometric data is compared to data from still photos, first with photos directly from the camera and then with RAW-data from the camera. The third measurement compared the spectroradiometric data with data from a frame from a video. The results show that the 22 colours are reproduced with varying degrees of accuracy in photos and video compared to a direct measurement using a spectroradiometer. For the two photo measurements the results span from ?E94 = 0.82 for the best colour reproduction to ?E94 = 17.01 for the worst reproduction. The average deviation was ?E94 = 7.48 and ?E94 = 8.46 respectively where a colour difference of ?E94 =1.0 is considered a just noticeable difference. For video the deviation spans from ?E94 = 4.89 to ?E94 = 18.11 with an average deviation of ?E94 = 11.59. ?E94 has also been used to evaluate how the colour contrast between two different colours differ between the spectroradiometric measurement and data from Photoshop. The results show that for photos the colour contrast deviates quite a bit between the two methods. A deeper evaluation of the video method shows that as long as the contrast between two colours is small the deviation compared to the spectroradiometric measurement will also be small.