Abstract
In this study, we propose a new approach to attain energy by salinity gradient engines with pistons based on hydrogels possessing polyelectrolyte and antipolyelectrolyte effects in a tandem arrangement, providing energy in each salinity gradient mode in a repeatable manner. The swelling of hydrogel with a polyelectrolyte effect and shrinking of hydrogel particles possessing an antipolyelectrolyte effect in desalinated water, and subsequent shrinking of hydrogel with polyelectrolyte and swelling of hydrogel antipolyelectrolyte effect in saline water, generate power in both increasing and decreasing salinity modes. To investigate the energy recovery, we scrutinized osmotic engine assemblies by a setup arrangement of pistons with hydrogel particles, with polyelectrolyte and antipolyelectrolyte effects, in tandem. The energy recovery from the tandem engine setup (calculated based on dry form for each polyelectrolyte polyacrylate-based hydrogel-SPA) and antipolyelectrolyte–sulfobetaine-based gel with methacrylate polymeric backbone-SBE) up to 581 J kg−1 and a mean power of 0.16 W kg−1 was obtained by the tandem setup of SPA and SBE hydrogel containing 3% crosslinking density and particle size of 500 microns with an external load of 3.0 kPa. Exchange of sulfobetaine with methacrylamide (SBAm), the main polymer backbone, revealed a positive increase in energy recovery of 670 J kg−1 with a mean power of 0.19 W kg−1 for the tandem system operating under the same parameters (SPA@SBAm). The energy recovery can be controlled, modulated and tuned by selecting both hydrogels with antipolyelectrolyte and polyelectrolyte effects and their performing parameters. This proof of concept provides blue energy harvesting by contributing both polyelectrolyte and antipolyelectrolyte effects in a single tandem setup; together with easy accessibility (diaper-based materials (SPA)) and known antibiofouling, these properties offer a robust alternative for energy harvesting.
Highlights
Continual depletion and increasing consumption of fossil fuel as well as the subsequent boosting of greenhouse emissions have made energy security and climate change top global challenges [1,2]
Connection, where the inlet of fluid is first introduced to the piston possessing hydrogel particles with antipolyelectrolyte and polyelectrolyte effects, generates more energy than opposite connection
The energy recovery of 670 J kg−1 was reached by the combined engine in which sulfobetaine gel with amidic functionality (SBAm) hydrogel obtained 3% crosslinking density and particle size of 500 micron with an external load of 3.0 kPa. This polyelectrolyte–antipolyelectrolyte combined system is comparable and generated a total mean power of 0.19 W kg−1 with an external load of 3.0 kPa, which is higher than the mean power recovered by poly(acrylic acid) hydrogelbased polyelectrolyte as a single system (0.23 W kg−1 with an external load of 6 kPa) [31]
Summary
Continual depletion and increasing consumption of fossil fuel as well as the subsequent boosting of greenhouse emissions have made energy security and climate change top global challenges [1,2]. We have studied the engine principle where the driven force is complementary and opposite to the salinity gradient with a so-called antipolyelectrolyte effect In this principle, hydrogel matrix swelling in response to seawater and movement of pistons is upward, and subsequent deswelling is in response to desalinated water with a downward movement of pistons. Polyzwitterionic sulfobetaine-based hydrogel use and maximum mean power generated from salinity gradient reach up to 28.6 mW kg−1 (calculated based on dry form), obtained by a hydrogel with a 3% crosslinking density, a 200–300 μm particle size, and 100 g as an external load [35] Energy efficiency in this combination was high at 0.73%. It should be mentioned that in all mentioned approaches, energy is generated only by decreasing or increasing the salinity gradient In this contribution, we describe an osmotic engine device containing two compartments with pistons in tandem configuration that possess antipolyelectrolyte- and polyelectrolyte effect-based hydrogels. The amidic polymer backbone function possessing more water than ester SBE-based hydrogels due to additional hydrogen bonding from N–H is a secondary amide group
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