Remote sensing test for dielectric fluids

The Bureau of Safety and Environmental Enforcement (BSEE) funded project 140E0124P0011 to Water Mapping, LLC (WM) to conduct research on the capabilities of remote sensing technologies for detecting floating refined hydrocarbons such as Dielectric Fluids (DF) associated with energy harvesting operations on the outer continental shelf. This project consisted of a series of laboratory tests in control setting scenarios at Ohmsett and Water Mapping facilities. To carry out this project, three of the most commonly commercially available DF in the industry were used: Hyvolt, Midel, and FR3. For this project, BSEE acquired a multispectral sensor Altum-PT1 from MicaSense, additionally Water Mapping utilized other infrared, multispectral, and visual sensors. The core mission of this project was to determine under which ambient conditions those sensors could detect presence/absence of floating DFs and at what degree was possible to characterize qualitatively or quantitively the thickness of the floating layer of DF. 

The objectives of the project consisted of testing the sensors under a variable set of viewing angles and ambient conditions (illumination and air temperature) to determine operationalization of these sensors for a possible emergency response in case of a spill of DFs into the environment. To meet these objectives, the work was executed as a three-staged test program that moved from controlled target trials to full-scale tank deployments. Initial laboratory testing (first stage) and field-style setups (second-stage) were used to establish sensor behavior over known DF thicknesses, verify calibration and processing routines (including band alignment and thermal temperature conversion), and identify the combinations of viewing geometry and ambient conditions most favorable for detection. These findings were then carried forward into the third-stage Ohmsett campaigns designed to stress-test detection and thickness characterization under realistic outdoor variability (sun angle, irradiance, temperature change through day/night). One of the main challenges of the project was the intrinsic transparency of all DFs, therefore, the Ohmsett tests specifically laid out multiple targets of DF samples of known types and thicknesses. 

The results of this project showed that due to the physical and chemical properties of DFs, thermal and multispectral sensors can be used to detect DFs floating over water, however optical/visual sensors where not suitable to neither detect nor characterize DFs. While the near-infrared sensor had a remarkable capacity to detect presence/absence of DFs, the thermal sensors demonstrated their capability to characterize qualitatively and quantitatively their thickness under a range of ambient conditions. The positive results from the Ohmsett experiment shed light towards operationalization of remote sensing mounted on aerial sensors for emergency response operations. The reflectance of DFs in the near-infrared wavelength shows a contrast of 0.08 reflectance units higher than the clean water under daylight. Due to the physical and chemical properties of DFs to store heat, detection of thicker layers of DFs could be observed even at dark after few hours after sunset using the infrared (thermal) sensor. The significant technical achievement of this work is the development of a sophisticated image processing algorithm. This operationalization tool is distinguished by its ability to process and classify DF thicknesses in near real time, marking a paradigm shift in data processing capacity and establishing a new benchmark for analytical speed critical to inform spill response decision makers.