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Featured Application: This article presents a discussion on the gains from enhancing salt rejection from a broad perspective, which includes the specific energy consumption and some insights into a technical direction to improve salt rejection of TFC-RO membranes. Since the specific energy consumption (SEC) required for reverse osmosis (RO) desalination has been steeply reduced over the past few decades, there is an increasing demand for high-selectivity membranes. However, it is still hard to find research papers empirically dealing with increasing the salt rejection of RO membranes and addressing the SEC change possibly occurring while increasing salt rejection. Herein, we examined the feasibility of the process and material approaches to increase the salt rejection of RO membranes from the perspective of the SEC and weighed up a better approach to increase salt rejection between the two approaches. A process approach was confirmed to have some inherent limitations in terms of the trade-off between water permeability and salt rejection. Furthermore, a process approach is inappropriate to alter the intrinsic salt permeability of RO membranes, such that it should be far from a fundamental improvement in the selectivity of RO membranes. Thus, we could conclude that a material approach is necessary to make a fundamental improvement in the selectivity of RO membranes. This paper also provides discussion on the specific demands for RO membranes featuring superior mechanical properties and excellent water/salt permselectivity to minimize membrane compaction while maximizing the selectivity. [ABSTRACT FROM AUTHOR]

Highlights • The energy and economic impacts of solar photovoltaic soiling were modelled. • Relative net-present value change was defined to assess optimal cleaning intervals. • We compared the soiling-induced efficiency and economic losses in seven cities. • The efficiency loss is the lowest (<0.04) for Tokyo and highest (>0.8) for Doha. • The optimal intervals are 23–70 days (manual) and 17–49 days (machine). Abstract This work developed a framework to predict the energy and economic impacts of solar photovoltaic soiling. This framework includes the effects of relative humidity, precipitation and tilt angle on solar photovoltaic soiling. A concept of relative net-present value change was introduced to determine the optimal cleaning interval. The uncertainties in the economic analysis were accounted for using a Monte Carlo simulation method. The framework was used to study the soiling-induced efficiency and economic losses of solar photovoltaic modules in seven cities (i.e. Taichung, Tokyo, Hami, Malibu, Sanlucar la Mayor, Doha, and Walkaway). Overall, the efficiency loss (in ascending order) for Tokyo/Walkaway < Taichung < Sanlucar la Mayor < Malibu/Hami < Doha for a one-year study period. Doha experiences an efficiency loss over 80% for a 140-day exposure, while Tokyo has an efficiency loss less than 4% for a one-year exposure. Malibu has longest optimal cleaning intervals (70 days for manual cleaning and 49 days for machine-assisted cleaning) that leads to the relative net-present value changes of 1.7% and 1.1%. Doha has the shortest optimal cleaning intervals (23 days for manual cleaning and 17 days for machine-assisted cleaning) that leads to the relative net-present value changes of 21% and 19%. The work serves as an effective tool for designing optimal cleaning protocols for solar photovoltaic systems. [ABSTRACT FROM AUTHOR]

In this work, we explored the practicability of a nanochannel-based biomimetic membrane (NBM) incorporating pillar[5]arene water channels for seawater reverse osmosis (SWRO) desalination. Two classes of peptide-attached biomimetic channels, (pR)-pillar[5]arenes (pRPH) and (pS)-pillar[5]arenes (pSPH) were integrated into the selective layer of SWRO membranes via interfacial polymerization on the top side of a polysulfone (PSf) support membrane. Here, pSPH is a non-identical stereoisomer of pRPH and was used as a negative control to pRPH to elucidate the flux enhancement effect contributed by pRPH. The optimized NBM presented a water permeability of 2.52 L m-2 h-1 bar-1 and 99.5% rejection under SWRO testing conditions of 50 bar applied pressure and 32,000 mg/L NaCl as feed solution. The 62% permeability increment with reference to the control membrane is hypothesized to originate from hybrid polyamide layers that were rougher with more voids (higher effective surface area and lower hydraulic resistance for water transport) as well as the conceivable water transport pathways provided by the pRPH channels. The simulation results from module-scale modelling suggest that the optimized NBM could lead to 7.2% savings in specific energy consumption of the membrane unit stage (or reduce the required membrane area by 25%) with respect to the commercial SWC4-LD membrane. The performance of the optimized NBM was further assessed in a one-week desalination test using an actual seawater feed gathered from an SWRO plant in Singapore. The robust NBM exhibited stable performance and ∼28% higher water flux (42 L m-2 h-1) than SWC4-LD with a comparable rejection of 99.3%, suggesting the feasibility of pillar[5]arene-based biomimetic membranes for seawater desalination. [Display omitted] • pRPH nanochannel-based biomimetic membrane (NBM) was used for SWRO application. • pRPH channels were incorporated into the PA layer via interfacial polymerization. • High permeability of 2.52 Lm-2h-1bar-1 (99.5% NaCl rejection) was reported in SWRO. • The energy and footprint savings achievable was quantified by module-scale modelling. • The NBM exhibited stable flux in a 7-day desalination test using real seawater. [ABSTRACT FROM AUTHOR]