Thermal performance and economic viability of a finned, inclined latent heat thermal energy storage unit: a numerical study

This study challenges a fundamental assumption in thermal energy storage design: that maximizing thermal performance is the optimal path to system viability. By coupling a detailed numerical simulation (finite volume method, enthalpy-porosity model) of a finned, flat-plate Latent Heat Thermal Energy Storage (LHTES) system with a rigorous thermo-economic assessment, we demonstrate a critical misalignment between thermal efficiency and economic return. Our integrated approach quantifies the combined effects of fin height (0-4 cm) and system inclination angle (0-90°) on the melting dynamics of n-docosane Phase Change Material (PCM). The thermal analysis reveals that while system inclination profoundly alters natural convection currents, increasing fin height dramatically accelerates melting rates, particularly in vertical orientations. The core contribution lies in the thermo-economic interrogation: we find that although all configurations yield positive investment metrics, the highest profitability - a Net Present Value (NPV) of $16,630.89 and an Internal Rate of Return (IRR) of 0.669% - is achieved under conditions that are suboptimal for rapid thermal charging. This divergence between the "fastest" system and the "most profitable" one underscores a critical oversight in current design paradigms. The findings establish a compelling case for an integrated, profitability-driven design approach.