Study of solar regenerated membrane desiccant system to control humidity and decrease energy consumption in office spaces

Abstract

This paper investigates the feasibility of using a solar regenerated liquid desiccant membrane system to remove humidity from an office space. While conventional vapor compression cycles dehumidify the air before supplying it to the indoor space, through using sub cool–reheat process, the proposed cycle absorbs the humidity directly from indoor space through the dehumidifier. The dehumidifier consists of a set of permeable vertical tubes placed in the indoor space with liquid desiccant flowing through them. Solar energy is used as the source of thermal energy required for the regeneration of the desiccant and sea water is used as heat sink to provide the cooling needs of the liquid desiccant.A mathematical model of the membrane desiccant system was integrated with the internal space model and solar system model to predict the humidity removal capacity from the space at given dehumidification and heat sink temperatures and outdoor environmental conditions. Experiments were performed to validate the model results be comparing exit humidity and temperature of the exit air from the space.The validated model was applied to a case study consisting of an internal office during the month of August in Beirut hot humid climate. A decrease of 10% in indoor relative humidity is observed when the system was used. The cost of the proposed system was compared to the cost of a conventional vapor compression cycle that provides the same indoor conditions. A payback period of 7years and 8month was estimated compared to the investment in the vapor compression cycle.