The present manuscript experimentally investigated the exergetic performance (efficiency) of a closed loop earth to air heat exchanger (underground air tunnel) in the cooling mode. The experimental system was commissioned in June 2009 and experimental data collecting have been conducted since then. The data, consisting of hourly thermodynamics records a year cooling period, 2009–2011, were measured in the Solar Energy Institute of the Bornova Campus at Ege University. At the present time, the database contains more than 40,000 records of measurements. Exergetic efficiencies value of the system and system components have been analyzed. Furthermore, a long term exergetic modeling of a closed loop earth-to-air heat exchanger solar greenhouse cooling system for system analysis and performance assessment is presented. Exergetic efficiency of the system and its compenents at various reference states are also determined.