Energy saving potential in freezing applications by applying cold thermal energy storage with solid carbon dioxide

In a time of fewer resources and rising energy prices savings of primary energy is an important goal for the food industry. This study analyses the potential of cold thermal energy storage (CTES) applying an indirect carbon dioxide system to reduce the electrical power needed by the freezing plant and to minimize the part load operation of the main compressor unit. Theoretical aspects are explained, a system concept is presented and industrial applications are discussed. As an example from the fish industry, a tunnel freezer is applied as a base case for the modelling, it freezes 30t fish per day. A cascade process of ammonia and a carbon dioxide (CO2) cycle is calculated for a 24 hours period. The calculation indicates that up to 30% less electricity is required for the equal freezing capacity, when CTES is utilized. CTES is a promising technology and offers new temperature levels (below -50 °C) for a wide range of applications. The proposed system offers a way to improve the performance and the efficiency of industrial applications as for example tunnel freezers. The final design and operation of CTES systems applying the natural working fluid CO2 requires further research in the behavior of solid CO2.