Cold storage system and method of operating a multi-packed bed cold storage system

A Cold Storage System comprising:

• a cold storage (C) for storing coldness;
• a compressor (A) enabling the circulation of a heat transfer fluid (HTF);
• a heat exchanger coil (D) for delivering of coldness to a user, wherein the heat exchanger coil (D) is arranged between the compressor (A) and the cold storage;
• and
• a bypass line with a bypass control valve (L), wherein the bypass line connects an inlet and an outlet of the cold storage (C) and the bypass control valve (L) is adapted to control a bypass flow through the bypass line to keep a temperature at the outlet of the cold storage (C) at a predefined setpoint temperature.

A method for operating a pressurised, low/ultra-low temperature, single or multi-packed bed cold storage system for central air conditioning, other cooling requirements or as energy storage system for renewable energy sources comprising a chiller as a cooling source (B) for cooling the heat transfer fluid (HTF) to low or ultra-low temperature, a multi-packed bed system as a cold storage (C) for storing coldness, the HTF compressor (A) enabling the circulation of the HTF in the closed circuit that operated under high-pressure and the heat exchanger coil for delivering of coldness to user (D) characterizing that,

• setpoints for temperatures and operation pressure which are:
• Charging setpoint temperature at the outlet of chiller as a Setpoint temperature for chiller,
• Setpoint temperature at the exit of every packed bed as a Setpoint temperature for bottom of each packed bed during charging mode,
• Setpoint temperature at the inlet of the HTF compressor,
• Setpoint pressure of the HTF compressor as a setpoint pressure,
• Setpoint temperature at the heat exchanger for delivering cooling to the user as a setpoint temperature of the heat exchanger for cooling purposes
• are set to the predetermined values before initiating the system;
• during charging phase, the heat transfer fluid is compressed by the HTF compressor (A);
• the pressurized HTF enters the chiller (B), where its temperature decreases to the setpoint temperature for chiller;
• the cold and pressurized HTF enters the multi-packed bed system (C) from the bottom and exit from the top;
• at the outlet (point (3)) of the multi-packed bed system, the HTF flows to the HTF compressor;
• the charging phase is stopped, when the temperature of the HTF at the top of the multi-packed bed system (point (3)) reaches the setpoint temperature at exit of packed bed;
• a bypass control valve (K) is applied in between the exit of chiller (B) and the exit of multi packed bed system (C) and the exit of HTF compressor (A) for keeping the HTF temperature at the inlet of HTF compressor (A) as setpoint temperature;
• and
• if no bypass is applied, the HTF temperature at the exit of the multi-packed bed system at point (3) is high at the start and declines over the course of the charging phase due the temperature decrease in the multi packed bed.