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Solar-driven Desalination with Phase-Change Energy Storage

Along with recycled wastewater, desalination is one of the few rain-independent water sources. Solar-driven desalination is a promising technology since it provides an inexpensive, self-sustaining water supply.

In this News, we show how ADINA has been used to optimise a solar-driven desalination cycle that employs a phase-changing material to maintain constant temperature throughout the day and night. This work was carried out by E.K. Summers, et al. at MIT (see the reference below), and was funded by King Fahd University of Petroleum and Minerals.

Figure 1 shows the schematic drawing of the collector. The phase change material is paraffin wax with an embedded aluminum matrix to enhance the wax layer conductivity. ADINA was used to optimize the thickness of this layer to produce a constant output temperature for a variety of weather and operating conditions.





Figure 1  Schematic of collector with the storage media


Figure 2 shows the details of the model. Temperature-dependent convective boundary conditions were applied to account for the natural convection between the glazings, the forced convection due to the air flow, and the irradiation from the sky. The phase change was encapsulated into the heat capacity of the material. Of course, ADINA also could have been used to directly account for the phase change between liquid and vapor.





Figure 2  Model of solar collector with built-in storage




The ADINA results showed that a phase change material layer thickness of 8 cm was optimal. The ADINA simulations accounted for various mass flow rates, from 0.013 to 0.052 kg/s, representing Reynolds numbers in the duct from 4000 to 16000.

The researchers built the optimized energy storage collector and tested it in a variety of weather and operating conditions in Dhahran, Saudi Arabia. Figure 3 shows the collector experimental setup onsite.






Figure 3  Collector experimental setup on site




As can be seen in Figure 4, the experimental results show strong agreement with the ADINA simulations. The above movie shows the temperature variation for the optimal configuration used to determine the melt front.






Figure 4  Simulated and experimental temperature profiles for the solar collector for a sunny day. The solar irradiation is shown in green




This example demonstrates how the powerful modeling capabilities of ADINA can be used by industry and researchers in the advancement of state-of-the-art engineering designs.

 

Reference

  • E.K. Summers, M.A. Antar, J.H. Lienhard V, "Design and optimization of an air heating solar collector with integrated phase change material energy storage for use in humidification–dehumidification desalination", Solar Energy, 86:3417-3429, 2012.


Keywords:
Solar air heater, desalination, energy storage, phase change material, heat transfer

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