Solar thermal systems can support a substantial heat demand in the industrial and residential sectors, but it does not always match demand. Therefore, thermal energy storage (TES) is critical in these systems. Among the different TES methods, adsorption and absorption (sorption) heat storage is promising compared to conventional sensible TES and latent TES. Sorption based thermochemical heat storage offers high energy densities as well as exceptional advantages in minimising losses when utilised for long-term heat storage solutions. Furthermore, sorption systems can be regenerated at relatively low temperatures (approximately 120 °C) which are achievable by solar collectors. To commercialise sorption storage systems, additional research and development is required to make them more economical. One of the most promising material types for TES is Zeolites which can store approximately 150 kWhth/m3. Typical applications for zeolite include drying, space heating and carbon capture. Natural zeolite is available locally in South Africa at a tenth of the price of the commercial grade zeolite 13X. However, natural zeolites may contain structures and impurities which can negatively affect the adsorption capacity. It is therefore necessary to investigate the TES properties for any relevant source. A lab-scale prototype was developed to analyse the thermal storage characteristics of natural (clinoptilolite sourced from a local supplier) in an open (non-pressurised) sorption system. The experiments that were conducted involved a reversible reaction between a solid (natural zeolite) and a gas (water vapour in air). The findings from the study will be evaluated to determine the feasibility of locally sourced natural zeolite for thermal energy storage.