: The air‐stable phosphide, ZnCu2P8, was synthesized from its elements in gram amounts. It crystallizes in the Cu2.5In0.5P8 structure type [C2/c, Z = 4, a = 1110.8(2) pm, b = 964.7(2) pm, c = 752.7(1) pm, β = 110.027(3)°], and is the first ternary phosphide in the system Zn/Cu/P. Its crystal structure consists of two‐dimensional, layered polyphosphide‐anions, separated by tetrahedrally‐coordinated cations. 135 symmetry independent configurations, each with a different and specific Zn2+ and Cu+ arrangement, where explored with density functional methods. Whereby, each of the 135 cation ordering pattern has a diverse bandgap, and the total energies vary in the range of 1 eV. As several configurations with low energy are close in energy, an intrinsic disorder is discussed as origin of the promising low lattice thermal conductivity, observed.

The thermal performance of macro-encapsulated latent heat storage elements in form of thin, rectangular plates within an air-driven heat storage system is investigated. The plates are made of high-density polyethylene and filled with phase change material. Several plates are stacked together and inserted into a box which can be installed in a heating/air conditioning system. First, an experimental test rig was designed. Measured temperature and pressure drop data retrieved from the rig was then used to validate a simplified computational fluid dynamics model describing a section of the test setup including a stack of ten plates. Afterward, the model was reduced in complexity in order to perform a parametric study by varying geometric parameters of the storage plates. In total, 217 different geometries were simulated and their thermo-hydraulic efficiency was evaluated. As a result, geometries were proposed, which can potentially increase the thermohydraulic efficiency of the storage plates by over 50%.

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