Real-Time Environmental Data Collector with Energy Harvesting and Intelligent Sensing for Marine Applications
Abstract
Underwater data collectors are devices designed to acquire information from beneath the ocean surface, providing valuable insight to subsurface conditions that are hard to measure by conventional surface instruments such as buoys and ship-based sensors.
The proposed data collector is optimized for Singapore waters and integrates an expanded sensor suite, including conductivity, temperature, and depth (CTD) sensors, a hydrophone, and an echosounder. The system is designed with a reduced size and weight (0.9 m length, 10.2 kg) compared to current underwater data collectors such as Argo floats (Argo: 1.3 m length, 40 kg) and has an extended deployment time of 10 years (~3500 profiles, assuming daily profiling), compared to 3–5 years (~100–200 profiles at 10-day cycles) for Argo systems. This extended operational lifespan is enabled by rechargeable batteries and solar energy harvesting.
The system architecture includes a buoyancy engine for depth control, sensor integration for data acquisition, power system design, and solar energy harvesting. The resulting data collector is lightweight, man-portable, and readily deployable. The sensor suite includes conductivity, temperature and depth sensors for inferring sound velocity of the ocean waters at that location and depth, an echosounder for determining seabed depth, and a hydrophone to listen to the ocean soundscape and for underwater sound pollution monitoring. Experimental validation demonstrates accurate sensor measurements, stable depth control, and effective solar energy harvesting, with example quantitative results provided in Section V.
The system is intended for the collection of oceanographic data, with an emphasis on real-time measurements of ocean conditions (data transmitted upon each surfacing). The enhanced data collector will facilitate oceanographic research by providing real-time data on ocean conditions, sound pollution monitoring and sediment movement information.
Keywords
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Introduction
Underwater data collectors are devices designed to gather information from beneath the surface of oceans. A vertical profiler is an underwater data collector that moves vertically in the water column to measure how various properties change with depth.
Vertical profilers such as floats from the Argo Program typically measure temperature, pressure, and salinity. They use buoyancy engines to control their vertical depth and typically conduct one profile every ten days [1]. Power management remains a significant challenge due to battery limitations, limiting the range of sensors that can be used and profiling frequency [2].
Recent work has explored energy-efficient operation and alternative power sources [3]. For instance, Yu et al. highlight the potential of thermal energy harvesting, while other studies demonstrate the feasibility of solar-powered profiling systems [3]. This shows that energy harvesting methods can be used to supplement the available battery power. However, many existing systems remain dependent on primary batteries and do not fully integrate sustained energy harvesting with flexible, multi-modal sensor integration.
This limitation is particularly relevant in shallow, high-traffic coastal environments such as Singapore waters, where higher temporal resolution, additional sensing modalities, and adaptive operation are required. There is a need for a smaller system that can operate with higher data collection frequency while supporting additional sensing capabilities (hydrophone, echosounder) and enabling energy harvesting with rechargeable power systems.
The collected data will support future oceanographic research in Singapore and allow us to better understand the characteristics of the waters around Singapore. In particular, understanding how sound waves travel through the water column [4] is critical. Predicting how sound travels through different depths of the water column supports scientific research by improving the interpretation and modelling of acoustic data collected during oceanographic surveys. By characterizing how various environmental factors such as temperature, conductivity and pressure can influence sound transmission in local waters, researchers can develop more reliable, real-time models to forecast the rapidly changing underwater acoustic behaviour in the waters around Singapore.
Conclusion
This project focuses on the design and development of a prototype environmental data collector for marine applications. A hydraulic buoyancy engine was designed and implemented. Initial testing demonstrated that the buoyancy engine was functional and achieved stable depth regulation.
The sensor subsystem was successfully implemented. Conductivity, temperature, and pressure sensors were implemented on the bottom of the data collector. An echosounder was integrated for bathymetry collection. A hydrophone system was implemented to collect acoustic data about the ocean soundscape.
The electronics subsystem was developed. A custom PCB was designed and fabricated. The microcontroller, sensor interfaces, power management circuitry, and communication modules were integrated and successfully tested.
A solar energy harvesting system was implemented. Flexible solar panels were mounted on the external structure. Mechanical integration of the system was completed. Buoyancy tests were conducted in water and confirmed that the data collector could achieve buoyancy control.
Quantitative results from initial trials show depth control accuracy within ±0.3 m, solar harvest of approximately 8.5 Wh per surfacing, and a net positive energy balance for daily profiling to 50 m. Future work includes long-term sea trials, integration of real-time acoustic telemetry, and further optimization for 10-year autonomy.
References
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