Lifetime Assessment of Polyolefinic Liners for Pit Thermal Energy Storages

This paper presents the lifetime assessment of polyolefinic liner materials for pit thermal energy storages (PTES). The study introduces a predictive approach based on accelerated aging of micro‐specimens, enabling lifetime extrapolation to real‐scale liners under service‐relevant conditions. A novel high‐temperature‐resistant polypropylene (PP‐HTR) was tested between 85°C and 135°C. Aging was evaluated by oxidation onset temperature and strain‐at‐break, determined through thermal analysis and tensile testing. Results were compared to commercial polypropylene random copolymer (PP‐R) and high‐density polyethylene (PE‐RT) grades. For lifetime extrapolation, an Arrhenius relationship was established for temperature dependence and a power law model for the effect of thickness. Assuming cumulative damages, lifetime values were estimated for several upcoming PTES. The novel PP‐HTR liner exhibited superior long‐term durability, outperforming PP‐R and PE‐RT materials by a factor of 4 and 6, respectively. Endurance times of up to 50 years at 80°C were deduced.