Anti-Frosting and Rapid Defrosting by Photothermal Superhydrophobic Surfaces for Electric Vehicle Heat Pumps

Research Overview

This study focuses on functional surfaces that combine superhydrophobicity and photothermal conversion. The surfaces were experimentally evaluated in terms of icing delay, photothermal ice melting, and rapid deicing under low-temperature conditions. The findings suggest a promising route toward low-energy auxiliary defrosting for electric vehicle heat pump heat exchangers.

          In electric vehicles, frosting on heat pump heat exchangers affects winter heating performance, defrosting energy consumption, driving range, and windshield defogging. Therefore, frost control is related not only to heat exchanger performance, but also to cabin comfort, visibility, and driving safety.
        

Graphical Abstract

Figure: One-page summary of the application background, concept, experimental evaluation, working mechanism, representative results, and potential applications of photothermal superhydrophobic surfaces for EV heat pump defrosting assistance.

Background and Objective

In cold and humid environments, frost forms on the outdoor heat exchanger of electric vehicle heat pumps. Frost accumulation blocks air flow passages, increases pressure loss, and deteriorates heat transfer performance. As a result, heating performance decreases, defrosting becomes more frequent, energy consumption increases, and driving range is reduced.

In addition, unstable cabin heating and reduced windshield defogging performance during defrosting may affect cabin comfort, visibility, and driving safety. Therefore, low-energy auxiliary defrosting technologies that can remove ice and frost rapidly and locally are required.

Features of This Study

Superhydrophobicity: Reduces the contact area between droplets and the solid surface, thereby delaying icing.
Photothermal conversion: Converts incident light into heat and locally warms the surface to promote ice melting.
Low ice adhesion: Promotes the formation of a thin water film at the ice–surface interface and reduces adhesion.
Drainage promotion: Helps melted water and ice slide off the surface, reducing residual water and refreezing risk.
EV application: Aims to support heat exchanger performance, reduce defrosting energy, and improve visibility and safety.

Proposed Method and Working Mechanism

1. Before icing

The microstructured surface retains air pockets, reducing the contact area between the droplet and the solid surface. This delays icing under low-temperature conditions.

2. During light irradiation

The photothermal function converts incident light into heat. Local surface heating promotes the initiation of ice melting.

3. When melting begins

A thin water film forms at the ice–surface interface. This changes the interface from strong solid–solid adhesion to a more slippery water-mediated state, reducing ice adhesion.

4. During deicing

Once adhesion is reduced, meltwater and ice can slide off the surface more easily. This lowers the risk of residual water and refreezing. By combining icing delay and active photothermal melting, the surface enables rapid deicing with reduced energy input.

          The central concept of this study is to achieve both delayed ice formation and rapid removal of formed ice using an integrated surface function.
        

Key Findings

High light absorption The maximum absorptivity at 808 nm reached 95.90%, indicating excellent photothermal conversion capability.

Icing delay Under −10°C conditions, the icing time was delayed by 1625 s compared with the control surface.

Ice melting under low light intensity The illumination intensity required to initiate ice melting was reduced to 0.10 W/cm².

Shorter ice-melting time Under low irradiation conditions, the total ice-melting time was shortened by up to 51.53%.

Reduced deicing energy In inclined-surface photothermal deicing experiments, the energy required for deicing was reduced by approximately 14.31%.

Effectiveness for rapid deicing The results indicate that the surface not only melts ice but also facilitates sliding removal and drainage after melting.

Future Prospects

The photothermal superhydrophobic surface demonstrated in this study is promising as an auxiliary defrosting technology for electric vehicle heat pump heat exchangers. It may contribute to maintaining winter heating performance, reducing defrosting energy consumption, improving heat exchanger efficiency, and suppressing driving-range reduction.

Future work should consider actual heat exchanger geometries, airflow conditions, frost-layer growth, and long-term durability in order to further evaluate the applicability of this approach to practical EV heat pump systems.

Potential Application Areas

This technology is expected to be applicable to low-temperature thermal management systems such as:

Electric vehicle heat pumps Air-source heat pumps Low-temperature heat exchangers Refrigeration and air-conditioning systems Thermal systems requiring anti-icing and deicing Winter visibility and safety enhancement

Conclusion

Photothermal superhydrophobic surfaces can delay icing under low-temperature conditions, promote ice melting under light irradiation, and accelerate deicing through low ice adhesion. These functions make them promising as low-energy auxiliary defrosting surfaces for electric vehicle heat pump heat exchangers.

          Conclusion:
          Photothermal superhydrophobic surfaces are promising as a low-energy auxiliary defrosting technology for electric vehicle heat pump heat exchangers.
        