Mitigating thermal stratification in lakes/reservoirs through wind-powered air diffusers

Area of Science:

• Environmental Engineering
• Renewable Energy Systems
• Fluid Dynamics

Background:

• Thermal stratification in large water bodies causes significant water quality degradation.
• Artificial mixing systems are crucial for mitigating these issues in reservoirs.
• Existing systems often rely on electrical energy, posing limitations.

Purpose of the Study:

• To design and experimentally evaluate a wind-powered artificial mixing system using Savonius rotors.
• To compare the performance of different Savonius rotor configurations (three-stage vs. four-stage) for artificial mixing.
• To assess rotor performance in terms of power, torque, and mixing efficiency.

Main Methods:

• Experimental testing of various Savonius rotor combinations (three-stage and four-stage) with different phase shifts.
• Measurement of rotor power and torque coefficients.
• Evaluation of artificial mixing efficiency in a controlled water tank simulating thermal stratification.

Main Results:

• The three-stage rotor with a 60° phase shift demonstrated superior power and torque coefficients (0.14 power efficiency).
• The four-stage rotor with a 45° phase shift achieved the highest mixing efficiency at 95%.
• Four-stage rotors generally outperformed three-stage rotors in mixing efficiency, while three-stage rotors excelled in power and torque.

Conclusions:

• Wind-powered artificial mixing systems offer a viable alternative to electrically powered systems for addressing thermal stratification.
• Rotor design (stage number and phase shift) significantly impacts both power generation and mixing efficiency.
• Specific configurations, like the four-stage rotor, are highly effective for achieving efficient artificial destratification in water bodies.