Liquid air utilization in air conditioning and power generating in a commercial building

Current air conditioning (AC) systems use a vapour compression system that consume a great amount of energy particularly during the peak times where most electricity suppliers facing difficulties to meet the users demands. Shifting the peak cooling demands to off-peak times using cold energy storage systems is a promising technique leads to save energy and to reduce the CO2 emissions. This study presents new technology that uses the cold energy storage in form of liquid Air (LAir) or liquid nitrogen (LN2) to provide air conditioning and power to commercial buildings. Four different cryogenic cycles were modelled and analysis from a thermodynamic point view, and compared in terms of their, output power, cooling capacity, recovery efficiency, COP and how much energy could save when compared with the traditional AC system. The results showed that system performance when LAir is used is 21–25% higher than that of when LN2 is used, and the 4th configuration is the most effective cycle and it recovered up to 94% of the energy stored in LAir and 78% of the energy stored LN2. Compared to the conventional system at the current LAir and LN2 prices, the 1st, 2nd, 3rd and 4th cycles showed saving up to 15%, 24%, 31% and 37.5%, respectively, when LAir is used and −3.5%, 5%, 16% and 24%, consecutively, when LN2 is used.