Techno-economic aspects of increasing primary energy efficiency in industrial branches using thermal energy storage

Abstract

Thermal energy storage (TES) can play a key role in increasing primary energy efficiency in the industrial sector. Differences in location-specific conditions lead to differences in TES requirements across companies and to a lack of techno-economic knowhow regarding standardized implementation. This study provides a techno-economic overview of potential TES technologies (sensible, latent, thermochemical, and sorption) based on key performance indicators (KPI) and performs a qualitative pre-selection of the TES to be used in specific industrial branches at specific temperature levels. The outcome is a TES application matrix for industrial branches based on the quantified energetic and exergetic heat demand per temperature level and branch. This matrix is expected to facilitate and support the selection of future TES projects. The study demonstrates its methodology of estimating the energetic and exergetic heat demand of a country by applying it to Austria. In this case, the estimated energetic industrial heat demand is about 88 TWh/year, and the exergetic industrial heat demand is about 50 TWh/year. In the application matrix, 2,470 variants of industrial energetic heat demand and potential TES applications are evaluated. The results show that there is only a 6% match between a TES priority field of application and the fields with the greatest energetic heat demand. As the costs of a TES system influence its industrial use, an economic top–down method of determining the maximum costs (and thus economic viability) of a TES system is presented. The generic approach is demonstrated by conducting a case study of a cement plant. The acceptable storage costs are derived by determining the energy and cost savings relative to a conventional gas-driven energy supply system. Depending on the size of the TES, the acceptable costs are found to vary between 1.4 and 14.4 €/kWh for a capacity of 500 MWh and 1 MWh, respectively. A sensitivity analysis is also conducted to show how gas and CO2 emission allowance prices affect the acceptability of storage costs. The study also discusses the main considerations and factors in efficient TES selection and successful system integration. Finally, the development and innovation required to increase industrial use are outlined. The study's economic analysis of TES integration in a cement plant shows that TES implementation is not feasible under the present conditions unless appropriate measures and incentives are applied.