A refrigeration system using phase change material (PCM) with six operating modes is proposed to reduce the cooling energy use of energy-demanding spaces such as data centers and telecommunication base stations. PCM is used to store the cold of outdoor air (OA) and/or that produced by vapor compression refrigeration (VCR) at night, and to release the stored energy for indoor cooling during the daytime. Real-time space cooling and cold charging by VCR can be accomplished simultaneously. Free cooling from OA can provide significant energy saving for space conditioning. A prototype system using a commercially available PCM was developed and tested to investigate the system performance and operation characteristics. The temperatures of air, water and refrigerant were measured along with the refrigerant pressure. The study calculates and analyzes the refrigerating capacity, cooling capacity, cold storage rate, supplied cold, stored cold, and the coefficient of performance (COP) upon the measurements. Experimental results indicate that the proposed refrigeration system can perform the requested tasks in a stable manner. The paper further compares the operating performances with the cold from OA and from VCR. It is found that under the outdoor temperature of 15 degrees C, OA appears to be more energy-efficient than VCR when the stored cold is less than 5.8 MJ, but it takes more time to charge the cold. (C) 2017 Elsevier B.V. All rights reserved.