# Remote Water Quality Monitoring System for Use in Fairway Applications
## 2 Materials and Methods
### Remote Water Quality Monitoring System Architecture
* Gravity--Analog Electrical Conductivity Sensor PRO (SEN0451) [41]: The Gravity sensor allows precise measurement of the electrical conductivity of water solutions. Powered by 3 V to 5 V, it generates a stable output signal between 0 V and 3 V. Equipped with an industrial-grade probe and a platinum resistance thermometer (PT1000) for temperature measurement, it enables precise monitoring of water quality across a wide range of 1 to 2200 \(\upmu\)S/cm. With its resistance to pressure and high IP68 waterproof rating, it is ideal for use in harsh environments. The selected sensors demonstrated full compatibility with the previously chosen Leonardo + GSM module unit (Table 1). * Power supply for the central unit  
Full autonomy of the buoy (measurement and data transmission system) requires an internal power source. In the implemented system, a battery was used without a hybrid system with a second energy source, a photovoltaic system, or a wind generator, as is the case in other solutions [1; 2; 4]. This is due to the fact that the autonomous buoy is exposed to damage in the waterway (usually a river), e.g., to contact with floating tree branches, twigs or vessels, which would cause damage to the external energy source. Installing additional sources of electrical energy on buoys involves numerous risks, both above and below the water. Below are the main aspects of the issue:  
* Risks above water:
* Collisions with floating objects: Buoys located in busy waterways are susceptible to collisions with floating vessels such as boats, ships, and other watercraft. They are also at risk of contact with floating debris like tree branches. Such incidents may damage both the buoy and the devices installed on it. * Exposure to weather conditions: Devices (e.g., photovoltaic panels and wind turbines) installed on buoys are exposed to rain, wind, snow, hail, and UV radiation. Severe storms, fluctuating temperatures, and intense sunlight can cause mechanical damage, corrosion, and material degradation. * Vandalism or theft: Devices installed above water can be easily accessed by unauthorized individuals, increasing the risk of intentional damage or theft. * Risks below water:
* Collisions with underwater objects: Buoys may come into contact with drifting debris, branches, ice, or other underwater obstacles, which can damage the devices. * Corrosion and biofouling: Constant exposure to water promotes the corrosion of metal components of energy-generating devices (e.g., water turbines). Additionally, the growth of marine organisms like algae, mussels, or barnacles can burden the structure, limit functionality, or render it completely inoperative. * Hydrodynamic forces: Water currents, waves, and tides can affect the buoy's stability, creating stresses that may lead to damage to installed devices. Vibrations and oscillations can further accelerate component wear. On Figure 2, examples of damaged buoys are shown. In conclusion, installing external energy sources on buoys is highly problematic due to the numerous risks associated with the aquatic environment. The battery selected in the solution must meet high requirements related primarily to its service. The operation of a new generation LiFePO4 20 Ah 12.8 V battery for powering the central unit was proposed, tested, and compared to a classic lead-acid battery. The advantages of the LiFePO4 battery in its application to the intelligent buoy are as follows [42]:Lower weight: The LiFePO4 20 Ah battery weighs about 2 kg compared to its lead-acid equivalent of 5 kg, which is crucial for installation in a buoy and in its subsequent operation (replacement);
* Longer service life: It offers over 10 years of operation, and thanks to the low self-discharge, even after a year of non-use, the battery should be fully ready for operation.