Thermodynamic analysis of a highly pressurized co2 cycle for renewable energy applications

Refrigerated gases have been used to store energy with limited success. This paper presents the results of an exploratory study of how the behavior of fluids compressed to high pressures can be used to increase the efficiency of refrigeration cycles and one possible application for renewable energy. This research presents the results of thermodynamic modeling and analysis of a novel Carbon Dioxide (CO2) cycle to be used for alternative energy production. The thermodynamic computational simulations are carried out in MATLAB and use the NIST REFPROP database for modeling the high pressure (on the order of 1000 MPa) CO2 state points. Preliminary results show that the maximum energy that can be recovered using the proposed high pressure cycle in on the order of 11,043 J, for each mole of CO2 flowing in the cycle. Thus the Coefficient of Performance is COP = 2.22, and the efficiency of the cycle is estimated as η = 35%. Future work will focus on the development of equipment such as the cryogenic turbo-expander that can operate at the ultra-high pressures studied.