Cold thermal storage has been widely used in air conditioning systems. For electric air conditioning, it helps to shift the peak load on electricity grids; for solar cooling, it enables cooling supply during solar outages. CO2 hydrate has been proposed as a cold storage medium for its suitable phase change temperature and large latent heat. Tetra-n-butyl ammonium bromide (TBAB) has been studied to moderate the formation pressure of CO2 hydrate. In this study, formation and dissociation of CO2-TBAB semi-clathrate hydrate were conducted at low pressures ( < 10 bar) applicable to the operating conditions of air conditioning systems. The hydrates were formed with the TBAB mass fraction of 10, 20 and 32 wt%. Using the T-history method, the formation enthalpy of CO2-TBAB semi-clathrate hydrate was measured in a self-fabricated reaction tube. In addition, the formation behaviour of CO2-TBAB semi-clathrate hydrate, namely the CO2 gas uptake, the induction time and the supercooling degree, were investigated under various feed pressures and heat transfer fluid (HTF) temperatures. Besides, secondary promoters (tetra-n-butylammonium fluoride (TBAF) at the mass fraction of 0.1, 0.5, 2.0 and 3.5 wt%, sodium dodecyl sulphate (SDS) at the mass fraction of 0.1, 0.3 and 0.5 wt%, and TiO2 nanoparticle in 20 and 80 nm) were used to aid the hydrate formation. The aim of this study is to reduce the capital and operating cost of a CO2 hydrate cold storage system by increasing the gas uptake, decreasing the supercooling degree and shortening the induction time. (C) 2016 Elsevier Ltd. All rights reserved.