Installation Of Measuring Devices Research Articles

Gaussian mixture models for the optimal sparse sampling of offshore wind resource

Abstract. Wind resource assessment is a crucial step for the development of offshore wind energy. It relies on the installation of measurement devices, whose placement is an open challenge for developers. Indeed, the optimal sensor placement for field reconstruction is an open challenge in the field of sparse sampling. As for the application to offshore wind field reconstruction, no similar study was found, and standard strategies are based on semi-empirical choices. In this paper, a sparse sampling method using a Gaussian mixture model on numerical weather prediction data is developed for offshore wind reconstruction. It is applied to France's main offshore wind energy development areas: Normandy, southern Brittany and the Mediterranean Sea. The study is based on 3 years of Météo-France AROME's data, available through the MeteoNet data set. Using a Gaussian mixture model for data clustering, it leads to optimal sensor locations with regards to wind field reconstruction error. The proposed workflow is described and compared to state-of-the-art methods for sparse sampling. It constitutes a robust yet simple method for the definition of optimal sensor siting for offshore wind field reconstruction. The described method applied to the study area output sensor arrays of respectively seven, four and four sensors for Normandy, southern Brittany and the Mediterranean Sea. Those sensor arrays perform approximately 20 % better than the median Monte Carlo case and more than 30 % better than state-of-the-art methods with regards to wind field reconstruction error.

Effective hydraulic properties of 3D virtual stony soils identified by inverse modeling

Abstract. Stony soils that have a considerable amount of rock fragments (RFs) are widespread around the world. However, experiments to determine the effective soil hydraulic properties (SHPs) of stony soils, i.e., the water retention curve (WRC) and hydraulic conductivity curve (HCC), are challenging. Installation of measurement devices and sensors in these soils is difficult, and the data are less reliable because of their high local heterogeneity. Therefore, effective properties of stony soils especially under unsaturated hydraulic conditions are still not well understood. An alternative approach to evaluate the SHPs of these systems with internal structural heterogeneity is numerical simulation. We used the Hydrus 2D/3D software to create virtual stony soils in 3D and simulate water flow for different volumetric fractions of RFs, f. Stony soils with different values of f from 11 % to 37 % were created by placing impermeable spheres as RFs in a sandy loam soil. Time series of local pressure heads at various depths, mean water contents, and fluxes across the upper boundary were generated in a virtual evaporation experiment. Additionally, a multistep unit-gradient simulation was applied to determine effective values of hydraulic conductivity near saturation up to pF=2. The generated data were evaluated by inverse modeling, assuming a homogeneous system, and the effective hydraulic properties were identified. The effective properties were compared with predictions from available scaling models of SHPs for different values of f. Our results showed that scaling the WRC of the background soil based on only the value of f gives acceptable results in the case of impermeable RFs. However, the reduction in conductivity could not be simply scaled by the value of f. Predictions were highly improved by applying the Novák, Maxwell, and GEM models to scale the HCC. The Maxwell model matched the numerically identified HCC best.

Lightning Peak Current Sensor Based on Electret Technology

Lightning peak current is one of the most important parameter concerning the studies of the lightning phenomena. Nowadays, with a continuous dissemination of elevated structures, such as telecommunication towers, the study of the lightning peak current could be intensified with the installation of measurement devices in large scale. Thus, it is useful to develop a device that is robust, compact, low cost, and allows data collection. This paper describes a high-current sensor operating in a range up to 100- and 7.7-kA resolution. The system consists of a self-integrating Rogowski coil connected to the electret sensor by a coaxial cable. The electret sensor is installed in a sturdy and inexpensive casing at the tower base. Measurements indicate a linear and precise correlation between the voltage generated by the coil, installed on the top of the tower, and the impulse current from lightning.

The “HumFlow” Project – Developing a minimal invasive measurement system for estimating energy and humidity transfer processes through building walls

Establishing suitable indoor climate conditions for exhibits in historical buildings is one of the main goals for curators in museums and exhibitions. Different guidelines in the field of preventive conservation provide therefore useful criteria and methods to prevent or to delay the deterioration of the objects of cultural heritage. Maintaining such a suitable indoor climate often needs the usage of expensive HVAC-equipment, whose installation occasionally damages the historical structure of such buildings and poses a problem for protection standards for historical monuments. The ongoing “HumFlow” project contributes to the solution of two problems: Firstly, avoiding damages to building structures provoked by installation of measurement devices and, secondly, gaining enough measurement data and information of humidity and energy transfer processes of walls and other surfaces by developing a minimal invasive measurement system. This paper focuses on the overall project goals, describes the test bed including experiment design, discusses the first results and provides a simple hygrothermal model of a flat wall. Therefore, it can be seen as an introduction for subsequent contributions of this project.