Henrik Kjeldsen

The measurement and control of temperature plays a key role in achieving the European Green Deal targets for a low carbon energy system. Fibre-optic thermometry is an emerging technology that can improve temperature measurement in extreme environments for energy providers and industry due to its distributed sensing and immunity to electromagnetic fields. Various applications for optimisation and monitoring in the energy sector are described, covering the whole range from energy generation to transmission and consumption. However, fibre-optic thermometers have cross sensitivities to other quantities (e.g., strain and humidity) and ageing effects that need to be investigated, quantified and minimised to obtain traceable and reliable measurements. This is particularly important so that applications in critical infrastructure can benefit from future measurements that are not possible with conventional sensors. The European INFOTherm project aims to overcome the limitations that currently prevent the widespread use of fibre-optic thermometry by creating a dedicated European metrology infrastructure for research, development and calibration. First results on measurement uncertainty, improvement of measurement techniques and practical field tests are presented.

Surface soil moisture (SSM) products derived from microwave remote sensing technology are currently operational at coarse resolutions (10-40 km) and global scale. Despite the utility of existing Earth Observation (EO) SSM products, there is significant scientific interest in enhancing the ability to resolve fine-scale surface heterogeneity. High spatial resolution soil moisture patterns (e.g., 0.1-1 km) can improve our quantitative understanding of the soil-vegetation-atmosphere system and enhance applications such as mapping the impact of irrigation on local water budgets, assessing the effects of local soil moisture variability on atmospheric instability, and improving numerical weather prediction (NWP) and hydrological modeling at regional scales. Additionally, these high-resolution data are crucial for hydrometeorological research focusing on extreme weather events in the context of climate change.The European Copernicus program, with its sustained observation strategy using Synthetic Aperture Radar (SAR) sensors, including the European Radar Observatory Sentinel-1 (S-1), the S-1 Next Generation satellites, and the forthcoming EU L-band Radar Observation System for Europe (ROSE-L), motivates and stimulates the development of operational land surface monitoring at high spatial resolution.From the EO SSM validation perspective, significant efforts have been made to define protocols, identify reference measurements (RMs), and address the spatial mismatch between EO SSM products and RMs, which are typically point-scale measurements from hydrologic networks. However, this process is still ongoing, particularly for high-resolution SSM products, and requires a collaborative effort among different scientific communities to achieve metrologically traceable EO SSM.This paper presents the European project “Metrology for Multi-Scale Monitoring of Soil Moisture” (SoMMet), which aims to establish a metrological basis and harmonization in soil moisture measurements across scales, from point scale to remote sensing, through cosmic ray neutron sensors (CRNS). These sensors are characterized by different measurement supports in the horizontal, vertical, and temporal dimensions. A key aspect of the project is to conduct field campaigns at three high-level field sites across Europe: Marquardt in Northern Germany, Bondeno in Northern Italy, and the Apulian Tavoliere in Southern Italy. The comparison of soil moisture data from point scale, CRNS, and S-1 SSM at these experimental sites is discussed, and recommendations on EO SSM validation practices are provided.Acknowledgment: The project 21GRD08 SoMMet has received funding from the European Partnership on Metrology, co-financed from the European Union’s Horizon Europe Research and Innovation Programme and by the Participating States.

Soil moisture is one of the essential climate variables, and it is interesting from both meteorological and agricultural perspectives. At the same time, soil moisture measurements span several length scales, from in-field studies with point scale sensors, to field scale with CRNS-probes to even larger study areas investigated with remote sensing. These different techniques make use of fundamentally different physical principles for obtaining soil moisture measurements, and harmonizing these measurements requires that SI-traceability can be demonstrated. For the common metric of volumetric water content, this requires demonstrating traceability of both water and soil volume.The Danish Technological Institute (DTI) has implemented a dedicated setup for determination of water content. The setup takes samples ranging from 100 g up to 2 kg and a volume up to 2 liters, which makes measurements on representative soil samples feasible. In contrast to the to the traditional loss-on-drying method, the DTI reference setup provides SI-traceability of the water content, through measurements of air flow and dew point temperature.In this presentation, the design principles of the setup and the utilization of the setup for SI-traceable calibration of point scale soil moisture sensors are described.

Precipitation is among the most important meteorological variables for meteorological, hydrological and climate studies. From an operational point of view, non-catching precipitation gauges are attractive, because they require less maintenance compared to the more traditional catching types (e.g. gravimetric or tipping-bucket). For that reason, in recent years non-catching precipitation gauges are increasingly adopted in meteorological networks. Despite the growing number of such gauges, calibration procedures and dedicated setups are missing. The result is that sensors are not calibrated, and this has a negative influence on the accuracy and reliability of the measured data. Therefore, Danish Technological Institute (DTI) is currently developing at setup for test and calibration of non-catching rain gauges. The setup is intended to simulate real rain, i.e. it will produce water drops that are similar in both size and velocity to those found in real rain. The setup can produce drops with diameters from about 0.2 mm to several mm. Traceability to the SI-unit system is obtained by flow and area measurements. In this context a volumetric pump is employed and calibrated gravimetrically in the DTI micro-flow laboratory. The drop velocity is determined using a photographic system. A key advantage of the setup is that the non-catching gauges can be calibrated under well-controlled, stable laboratory conditions. The presentation describes the design principle and summarizes recent progress of the setup at DTI.

This paper presents methodologies and equipment for SI-traceable inline measurements of water content (a critical quality parameter) in solid biofuels. Inline measurement systems for water content are commonly used at CHP plants, providing continuous real-time data. However, the accuracy of these systems is in most cases unsatisfactory, mainly because the systems are not calibrated representatively for the relevant material, and until now, calibrations traceable to the SI system have not been available. To provide reliable and accurate inline water content data, new procedures and equipment for calibrating measurement systems were developed. Two reference methods for the determination of water content were developed; one measures the airflow and dewpoint of desorbed water in the air passing a test sample, while the other uses a P₂O₅-sensor. Additionally, a transfer standard based on a cavity resonance sensor was developed for fast onsite calibration of the inline sensor at the power plant. This new instrument allows for quick and accurate measurements. The transfer standard is made metrologically traceable to the primary measurement standards. The entire system was demonstrated by calibrating an inline microwave-based (MW) sensor at the CHP plant of VERDO in Randers, Denmark. Thus, a complete metrological traceability chain was established from an industrial to a primary standard.

In this study, five laboratories, namely, BRML (Romania), TUBITAK UME (Turkey), IMBIH (Bosnia and Herzegovina), BAM (Germany), and DTI (Denmark), developed and validated analytical procedures by ICP-MS, ICP-OES, MWP-AES, WD-XRF, and ID-MS for the determination of inorganic impurities in solid and liquid biofuels, established the budget of uncertainties, and developed the method for determining the amount of ash in the measurement range 0–1.2% with absolute repeatability less than 0.1% and absolute reproducibility of 0.2% (according to EN ISO 18122). In order to create homogeneous certified reference materials, improved methodologies for the measurement and characterization of solid and liquid biofuels were developed. Thus, information regarding the precision, accuracy, and bias of the method, and identifying the factors that intervened in the measurement of uncertainty were experimentally determined, supplementing the information from the existing standards in the field.

Precipitation is among the most important meteorological variables for, e.g., meteorological, hydrological, water management and climate studies. In recent years, non-catching precipitation gauges are increasingly adopted in meteorological networks. Despite such growing diffusion, calibration procedures and associated uncertainty budget are not yet standardized or prescribed in best practice documents and standards. This paper reports a metrological study aimed at proposing calibration procedures and completing the uncertainty budgets, to make non-catching precipitation gauge measurements traceable to primary standards. The study is based on the preliminary characterization of different rain drop generators, specifically developed for the investigation. Characterization of different models of non-catching rain gauges is also included.

Calibration traceability can be broken where there are significant, unquantified uncertainties. Thermometry in harsh environments using electrical sensors, such as thermocouples or resistance thermometers, can be unpredictably affected by electro-magnetic sources. For this application, phosphor based temperature sensors with fibre-optic connection have been made following two different approaches – phosphor decay time changes and phosphor emission spectral changes – and tested by bombardment with high energy electrons and by measurements in large magnetic fields. Both sets of tests showed good immunity to exposure, and with magnetic field tests significantly better than a thermocouple. Phosphor thermometry therefore has potential to retain traceability in situations where conventional sensors might fail.

We describe the design of and the first commissioning experiments with a newly constructed electrostatic storage ring named SAPHIRA (Storage Ring in Aarhus for PHoton-Ion Reaction Analysis). With an intense beam of Cu⁻ at 4 keV, the storage ring is characterized in terms of the stored ion beam decay rate, the longitudinal spreading of an injected ion bunch, as well as the direct measurements of the transverse spatial distributions under different conditions of storage. The ion storage stability in SAPHIRA was investigated systematically in a selected region of its electrical configuration space.

We have analyzed oscillations of the red giant star HD 186355 observed by the NASA Kepler satellite. The data consist of the first five quarters of science operations of Kepler, which cover about 13 months. The high-precision time-series data allow us to accurately extract the oscillation frequencies from the power spectrum. We find that the frequency of the maximum oscillation power, ν_max, and the mean large frequency separation, Δν, are around 106 and 9.4 μHz, respectively. A regular pattern of radial and non-radial oscillation modes is identified by stacking the power spectra in an echelle diagram. We use the scaling relations of Δν and ν_max to estimate the preliminary asteroseismic mass, which is confirmed with the modeling result (M = 1.45 ± 0.05 M _☉) using the Yale Rotating stellar Evolution Code (YREC7). In addition, we constrain the effective temperature, luminosity, and radius from comparisons between observational constraints and models. A number of mixed l = 1 modes are also detected and taken into account in our model comparisons. We find a mean observational period spacing for these mixed modes of about 58 s, suggesting that this red giant branch star is in the shell hydrogen-burning phase.