Microfluidic Salinity Gradient-Induced All-Day Electricity Production in Solar Steam Generation

Area of Science:

• Sustainable Energy
• Water Desalination
• Materials Science

Background:

• Global freshwater and energy demands are rising.
• Solar steam generation offers a promising, cost-effective freshwater alternative.
• Existing methods often face limitations in continuous operation and energy generation.

Purpose of the Study:

• To develop a system for simultaneous freshwater generation and electricity production using solar light.
• To maintain a salinity gradient in microfluidic channels for continuous operation.
• To explore the potential for all-day-long power generation and efficient water desalination.

Main Methods:

• Utilized two-legged paper-based microfluidic channels with a salinity gradient (seawater and tap water).
• Connected channels to a conical evaporator for solar steam generation.
• Systematically varied salt concentrations to study their effect on voltage output.
• Measured open-circuit voltage, short-circuit current, evaporation efficiency, and salt harvesting rates.

Main Results:

• Achieved an average open-circuit voltage of 150 mV and a short-circuit current of 6.5 μA per channel.
• Demonstrated a water evaporation efficiency of 88%.
• Increased open-circuit voltage to 250 mV with higher salinity (20 wt % NaCl).
• Obtained a maximum output power density of 9.9 mW m⁻² with four channels in series.
• Harvested salt at a rate of 0.33 kg m⁻² h⁻¹.

Conclusions:

• The developed system enables simultaneous freshwater generation, electricity production, and salt harvesting.
• The all-day-long electricity generation is driven by the sustained salinity gradient.
• This approach offers a versatile and efficient solution for addressing global water and energy challenges.