The prediction of thermodynamic properties performance in porous silicon (pSi) photonic crystals (PhCs) was studied for enhancement of light conversion into different types of energy based thermophotovoltaic energy conversion system. The unit-cell for 2D square and triangular lattices of circular air holes were formulated and solved using plane wave expansion (PWE) method. This was used to investigate the thermodynamic properties and the effect of lattice dynamic on these properties at different porosities in silicon PhCs; which are regarded as isolated and non-interacting particles systems. This was achieved by connecting density of states (DOS) and thermodynamic quantities as described in statistical physics. It revealed that irrespective of lattice type, increasing porosity ensued a decline in thermodynamic properties. Novel insights and theoretical concepts that could be integrated in thermophotovoltaic system were revealed. Regarding the square lattice, the optimum value of these properties except the free energy was obtained at R/a = 0.30 for 20% and 50% porosities, and at R/a = 0.25 for 80% porosity. Regardless of the porosity, the optimum value for the triangular lattice was found at R/a = 0.25. These characteristics have attempted to provide contributions with regards to the selection of the appropriate design for PhC in order to achieve high efficiency conversion. (C) 2018 Elsevier Ltd. All rights reserved.