Chiller energy savings by waste cold recovery from liquid nitrogen bulk

Abstract

Waste cold energy generated from the liquid nitrogen vaporization is usually abandoned when the gas supply system is pre-designed without cold integration. The purpose of this study is to investigate the potential for energy savings in a chiller system through the integration of waste cold recovery with thermal energy storage. The waste cold recovery system captures the waste cold generated during the operation of the liquid bulk nitrogen system and transfers it to a thermal energy storage system. This stored energy can then be utilized to supplement the chiller system during the targeted periods of peak demand, reducing its load and increasing its efficiency. The minimum of thermal energy storage capacity is determined by targeting the maximum peak shaving load through Cold Energy Storage Cascade Analysis (CESCA). The study analyses the feasibility of the waste cold recovery method in terms of energy savings, payback period and cost-effectiveness with peak load shaving of air-cooled and water-cooled chiller. Case study of 500 kg/h of liquid nitrogen revealed the significant energy savings at 124 MWh annually and avoided of 83 tCO2/year with minimum thermal energy storage capacity at seven tones of refrigeration. The simple payback period on air-cooled chiller is slightly better than water-cooled chiller which ranged from four to five years. The study concludes that the integration of waste cold recovery with thermal energy storage is a promising solution for liquid bulk nitrogen users looking for energy savings efforts and reduce their carbon footprint.