Distillation Based on Solar Chimmney-Mediated Energy Harvesting
S. Kazadi1, K. Rhee1, S. Yim1, R. Zhang1, R. Yim1, W. Lin1, T. Lee1, M. Cao1
1Jisan Research Institute
Previous work described how an entrochemical process could be used to enable water distillation. In that process, environmental thermal energy is harvested and used to enable thermal distillation, driven by a thermal energy-transferring process that increases overall systemic entropy and is therefore spontaneous. In this work we examine the second step - one in which systemic entropy is transferred spontaneously to the atmosphere, restoring the systemic low entropy state. This entropy transfer is accomplished using airflow enabled by a solar chimney. We constructed a solar chimney with a solar collector of 0.74 m2 and a chimney of 6.096 m height. Our chimney enables 50.96 m3/day of airflow with a thermal lift of approximately 13.86 ºC in sunlight with an intensity of 900 W/m2. Using these data, we calculate maximal energy yields of 151.9 W/m2, 266.6 W/m2, and 338.2 W/m2 in climes of 20 ºC, 30 ºC, and 35 ºC ambient temperature. When this energy yield is applied to distillation, these correspond to water yields of 2.44 L/day/m2, 4.28 L/day/m2 and 5.43 L/day/m2, respectively via single stage distillation. We calculate similar quantites for reduced humidification values. We extrapolate to larger systems and systems of greater thermal lift following the model of Schlaich et. al. (2005). Extrapolating to systems in climes of 35 ºC with chimney height of 200 m (as constructed in 1981/2 by the company Enviromission in Manzanares, Spain) may generate energy densities of 1.382 kW/m2 and yield 22.22 L/day/m2. Similarly extrapolating to systems with thermal lifts of 30 ºC (which have been reported elsewhere) produces an energy density of 984.79 W/m2, generating as much as 15.827 L/day/m2 with a chimney of 6.096 m height. Further extrapolating to the collossal chimney proposed by Enviromission (1km tall and a total surface area of 38,027 acres) yields energy densities of 12.613 kW/m2 and daily water production of 3.119 x 1010 L/day (25,285 acre-feet/day), or enough to supply approximately 82.4 million average American households (the 6 m chimney model with a thermal lift of 30 ºC might generate enough to supply as many as 6.4 million average American households). Because of the additional release of humidified air, which ultimately can cause cloud formation within and downstream of the chimney (VanReken and Nenes, 2010), and that the process harvests environmental thermal energy as a way of enabling this process (specifically avoiding carbon-producing energy sources), this is an attractive potential option for brackish or seawater desalination.