Raising the Bar: Increased Hydraulic Pressure Allows
Unprecedented High Power Densities in Pressure-Retarded Osmosis
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Abstract
Pressure-retarded
osmosis (PRO) has the potential to generate sustainable
energy from salinity gradients. PRO is typically considered for operation
with river water and seawater, but a far greater energy of mixing
can be harnessed from hypersaline solutions. This study investigates
the power density that can be obtained in PRO from such concentrated
solutions. Thin-film composite membranes with an embedded woven mesh
were supported by tricot fabric feed spacers in a specially designed
crossflow cell to maximize the operating pressure of the system, reaching
a stable applied hydraulic pressure of 48 bar (700 psi) for more than
10 h. Operation at this increased hydraulic pressure allowed unprecedented
power densities, up to 60 W/m<sup>2</sup> with a 3 M (180 g/L) NaCl
draw solution. Experimental power densities demonstrate reasonable
agreement with power densities modeled using measured membrane properties,
indicating high-pressure operation does not drastically alter membrane
performance. Our findings exhibit the promise of the generation of
power from high-pressure PRO with concentrated solutions