Solar chimney power plant combined with membrane distillation (SCPPMD), part I: Principle and operation characteristics

•A solar chimney power plant combined with membrane distillation was proposed.•A novel air gap membrane module was designed to be fixed vertically in solar still.•A transient heat and mass model was established to predict the system performance.•The variation laws of the operation and output parameters of SCPPMD were studied.•The effect of seawater thickness on system performance was discussed. In this paper, a novel solar chimney power plant combined with membrane distillation (SCPPMD) was proposed. SCPPMD could not only achieve power output but also product more freshwater, by installing a novel air gap membrane distillation module vertically in the disc distiller. A transient heat and mass model was established to predict the system performance. Then, the operation laws of SCPPMD under unsteady weather conditions and the effect of seawater thickness were explored. The results show that the peak power generation is about 4p.m. and the peak water yield lags two hours. The hourly water yield of the membrane is much higher than that of the disc distiller and its valley value reaches 11.55 t/h, 14.26 times the valley value of the disc distiller and 0.875 times its peak value. Membrane distillation still has considerable freshwater output even when the water production of disc distiller is weak. As the seawater layer thickens, the peak-valley difference of power generation is reduced and the daily power generation drops; The peak hourly water yield of disc distiller drops, the valley value increases and its daily water yield drops; Both the peak and valley value of membrane hourly water yield increase, and its daily water yield rises; The change of the system water yield is basically the same as that of membrane.