Solar Desalination Systems and Thermal Efficiency

Solar desalination harnesses solar energy to purify saline or contaminated water through evaporation and condensation pathways. In its simplest form, a solar still consists of a basin of feedwater covered by a transparent glazing. Incoming solar radiation heats the water, inducing evaporation; vapour then condenses on the cooler interior surface of the glazing and is collected as freshwater. Thermal efficiency in such systems is a critical metric, reflecting the proportion of solar irradiance converted into the latent heat of vapourisation. Conventional designs suffer from limited yield owing to low heat transfer rates and thermal dissipation losses, particularly during non-peak solar hours. To address these challenges, recent research has focused on integrating energy storage materials to preserve heat beyond daylight hours, advancing surface engineering to enhance absorptivity and phase-change technologies to regulate temperature, and employing optical concentrators to boost incident flux. Innovative geometries, including tubular configurations, rotating elements, and external condensers, have been demonstrated to increase evaporative surface area, disrupt thermal boundary layers, and improve condensing efficiency. Collectively, these developments aim to raise daily freshwater production, lower the levelised cost of water, and expand applicability in regions facing acute water scarcity.

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Solar Desalination Systems and Thermal Efficiency publication trend

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Technical terms

Phase-change material (PCM): A substance that absorbs or releases latent heat during its transition between solid and liquid phases, used to store and release thermal energy at nearly constant temperature.

Nusselt number: A dimensionless parameter representing the ratio of convective to conductive heat transfer across a fluid boundary layer, indicative of heat-transfer performance.

Exergy efficiency: The fraction of input energy that is converted into useful work or desired output, accounting for irreversibilities and system losses.

Nanocomposite: A composite material in which one phase has at least one dimension in the nanometre range, often used to enhance thermal conductivity and optical absorption.

Parabolic solar concentrator: An optical device employing a parabolic reflector to focus incident solar radiation onto a target receiver, increasing thermal flux.

References

1. Solar Still Efficiency Enhancement by Using Graphene Oxide/Paraffin Nano-PCM. Energies (2019).
2. Experimental enhancement of tubular solar still performance using rotating cylinder, nanoparticles' coating, parabolic solar concentrator, and phase change material. Case Studies in Thermal Engineering (2022).
3. Investigation and performance analysis of solar still with energy storage materials: An energy- exergy efficiency analysis. Case Studies in Thermal Engineering (2022).