Integration of cascaded nano-enhanced phase change materials in solar-driven MED-TVC desalination systems

In this work, an efficient integration of cascaded nano-enhanced phase change materials (NePCMs) as an energy storage system with a solar-driven MED-TVC desalination system is proposed through four different scenarios. The hybrid system consists of forward flow and parallel cross flow configurations of the MED-TVC system, a parabolic trough solar power unit, a high-temperature salt-based PCM storage system, three cascaded low- temperature fatty acid PCM storage units, and NePCMs. An optimal algorithm was developed to maximize the system's gain output ratio (GOR) while minimizing the loss of collected solar energy. To ensure practicality, the MED evaporators were designed with fixed capacities. The results showed that the parallel cross flow configuration is more efficient than the forward flow, particularly when integrated with solar energy. The addition of a cascaded low-temperature energy storage system, with descending melting points compatible with the temperature trend of the MED-TVC effects, significantly increases total water production by 53 % (from 2 to 3.08 x 10(5) kg/h) while reducing wasted energy by 68 % (from 1.9 to 0.6 x 10(5) MWh). Furthermore, using nanoparticles in NePCMs further enhances the system's effectiveness by improving the thermal properties of the PCMs, thereby increasing energy storage capacity. As a result, the GOR increases by over 50 %, waste energy is reduced by >79 %, and overall thermal efficiency improves by 10 %.