Abstract
► We have developed a numerical model for an osmotic power plant. ► We examined the net power output as function of several design parameters. ► The results of lab scale membranes do not directly predict the module results. ► The model shows that counter current flow is preferred to co-current. ► The model shows that it is feasible to produce 0.5
MW with 1
m
3/s of fresh water.
A hydrodynamic mass transfer model for a pressure retarded osmosis (PRO) power plant is developed to investigate the technical feasibility of such a power plant. The key element is a 2D model at the membrane level, which accounts for the actual size of the membrane sheets. This model enables the computation of salinity gradients along both sides of a membrane sheet, from which the local membrane flux is calculated.
Integration of the membrane flux across a membrane sheet yields the trans membrane flow rate in an entire module. The novelty of this paper is the determination of the performance of an osmotic power module from the 2D hydrodynamic mass transfer model. The developed numerical model can be calibrated against lab measurements and, more importantly can be used for reliable extrapolation of the membrane performance to the module and plant scale.
On the membrane level, the results are comparable to lab scale results from literature. However, the power output for real size membranes is about 40% lower than for lab scale membranes. Furthermore, counter-current flow gives an approximately 15% larger power output then co-current flow for real size membranes. The maximum gross power output that can be obtained with commercially available membranes is about 4.5
W/m
2. The optimum net power output is 0.5
MW/(m
3/s) for BWRO membranes. If hollow fiber membranes can be used and salt water pre treatment can be removed the power output can be 0.92
MW/(m
3/s).