Flexible Thermal storage selection and heat pump integration for industrial symbiosis

The industrial production sector is a major driver of global energy demand. In the EU28, industry accounts for 25% of final energy usage, with process heating responsible for 66% of this demand, highlighting the urgent need for sustainable heating solutions to mitigate greenhouse gas emissions. Flexible Industrial Energy Storage is critical for the transition from fossil fuels. While Phase Change Materials (PCMs) and thermochemical storage offer high energy densities, this work utilizes optimization heatmaps to demonstrate that sensible heat storage remains the economic standard: Water is optimal for low-temperature applications (< 150°C), while Granite and Limestone are cost-optimal for higher temperatures. PCMs and Cast Steel are viable only when volumetric constraints outweigh economic factors. High-Temperature Heat Pumps (HTHPs) provide a complementary pathway for decarbonization by recovering heat from exhaust and process streams. HTHPs are defined as systems delivering heat above 100°C and typically up to 200°C. In this context, the thesis identifies the Cascade nHexane/R718 cycle as a promising configuration for integrating a heat pump with thermal storage. This project proposes an automated, holistic methodology for selecting and integrating these technologies. The developed tool utilizes a Multi-Criteria Decision Making (MCDM) algorithm with validated alternative cost functions, reducing estimation uncertainty from 18.5% to 14.3%. The methodology was verified using the GreenLab Industrial Park case study. The results quantify a distinct trade-off between economics and decarbonization: A storage-only approach yields a rapid Return on Investment (DPBT ≈ 0.64 years) but limits CO2 savings to ≈ 56 ktCO2. Full electrification scenarios quadruple emissions savings (≈ 225 ktCO2) but extend the payback period to 3–5 years. Increasing the HTHP output temperature from 170°C to 230°C nearly halves the storage CAPEX (from 13.3 Me to 7.6 Me) by enabling larger thermal gradients, proving that advanced HTHPs are key enablers for reducing storage footprints.