Gobinath Pillai Rajarathnam

This work presents an adaptation of the material circularity indicator (MCI) that incorporates economic consideration. The Ellen MacArthur Foundation (EMF) has developed the MCI to characterize the sustainability, viz., the “circularity”, of a product by utilizing life cycle assessment data of a product range rather than a single product unit. Our new “circo-economic” indicator (MCIE), combines product MCI in relation to total product mass, with a cost-normalization against estimated plastic recycling costs, for both separately collected and municipal solid waste. This is applied to assess Dutch post-consumer plastic packaging waste comprising polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), film, and mixed plastic products. Results show that MCIE of separate plastic collection (0.81) exceeds municipal solid waste (0.73) for most plastics, thus suggesting that under cost normalization, there is greater conformity of separately collected washed and milled goods to the circular economy. Cost sensitivity analyses show that improvements in plastic sorting technology and policy incentives that enable the production of MSW washed and milled goods at levels comparable to their separately collected counterparts may significantly improve their MCI. We highlight data policy changes and industry collaboration as key to enhanced circularity—emphasized by the restrictive nature of current Dutch policy regarding the release of plastic production, recycling, and costing data, with a general industry reluctance against market integration of weight-benchmarked recycled plastics.

This study presents a life cycle assessment (LCA) of end-of-life (EoL) photovoltaic (PV) systems in Australia. Three different EoL scenarios are considered for 1 kWh of electricity generation across a 30-year PV system lifespan: (i) disposal to landfill, (ii) recycling by laminated glass recycling facility (LGRF), and (iii) recycling by full recovery of EoL photovoltaics (FRELP). It is found that recycling technologies reduce the overall impact score of the cradle-to-grave PV systems from 0.00706 to 0.00657 (for LGRF) and 0.00523 (for FRELP), as measured using the LCA ReCiPe endpoint single score. The CO₂ emissions to air decrease slightly from 0.059 kg CO₂ per kWh (landfill) to 0.054 kg CO₂ per kWh (for LGRF) and 0.046 kg CO₂ per kWh (for FRELP). Increasing the PV system lifespan from 30 years to 50 and 100 years (a hypothetical scenario) improves the ReCiPe endpoint single-score impact from 0.00706 to 0.00424 and 0.00212, respectively, with corresponding CO₂ emissions reductions from 0.059 kg CO₂ per kWh to 0.035 and 0.018 kg CO₂ per kWh, respectively. These results show that employing recycling slightly reduces the environmental impact of the EoL PV systems. It is, however, noted that recycling scenarios do not consider the recycling plant construction step due to a lack of data on these emerging PV panel recycling plants. Accounting for the latter will increase the environmental impact of the recycling scenarios, possibly defeating the purpose of recycling. Increasing the lifespan of the PV systems increases the longevity of the use of panel materials and is therefore favorable towards reducing environmental impacts. Our findings strongly suggest that PV recycling steps and technologies be carefully considered before implementation. More significantly, it is imperative to consider the circular design step up front, where PV systems are designed via circular economy principles such as utility and longevity and are rolled out through circular business models.

Zinc/bromine flow batteries are a promising solution for utility-scale electrical energy storage. The behavior of complex Zn–halogen species in the electrolyte during charge and discharge is currently not well-understood, and is an important aspect to be addressed in order to facilitate future electrolyte formulations. The speciation of the primary zinc bromide electrolyte with and without a secondary zinc chloride electrolyte is studied in the present work. Raman spectroscopy was carried out on aqueous solutions of zinc bromide at 5 concentrations (2–4 M) to account for the initial and later stages of charging, with 3 concentrations (1–2 M) of zinc chloride. Mixed solutions containing various combinations of each primary and secondary electrolyte concentrations were also studied. Semi-quantitative analysis of peaks after Gaussian and Lorentzian peak deconvolution showed that the proportion of four-ligand coordinated Zn–halides (i.e. [ZnBr ₄ ] ²⁻ and [ZnCl ₄ ] ²⁻ ) increases with higher salt concentration, as compared to complexes with lower halide coordination numbers. The presence of a previously unassigned peak was observed at the 220 cm ⁻¹ band in the Raman spectra of mixed electrolytes. Results from ab-initio molecular modeling using the GAUSSIAN 16 software package suggests this peak is due to the presence of the hybrid-halide anionic complex [ZnBr ₂ Cl(H ₂ O)] ^– . Increasing the Cl:Br ratio in electrolytes promotes hybridization and subsequently decreasing the proportion of single-halide Zn–Br complexes. While this speciation study is focused on Zn/Br batteries, the findings are also potentially applicable to other energy storage and electrochemical systems containing zinc halide electrolytes.

This study addresses the feasibility, sizing, and scheduling of an island micro‐grid involving photovoltaic, wind turbine, diesel generator, and battery energy storage systems. In addition, the end‐use demand is expanded beyond residential electricity loads, as the full electrification on domestic water supply and transportation, in the forms of desalination and electric vehicles (EVs), are proposed in this study with integration to a renewable energy system focused micro‐grid. A mixed integer linear programming model is constructed to explore the mutual interactions of desalination plant, vehicle‐to‐grid enabled EVs and residential load deferring on a micro‐grid. A case study in Bruny Island, Australia was incorporated in the study, based on the existing infrastructure and future planning. Multiple scenarios were run utilizing real‐world, fine resolution time‐series data. Results were compared to investigate the impact of the polygeneration configuration and potential economic savings on household affordability. Our study displayed the advantage of electrifying and integrating household resources into the micro‐grid, such as transportation and water filtration. The integration created a greater diversity in electricity end‐uses, allowed for better scheduling and Renewable System management. In addition, the cost‐benefit analysis of stationary battery storage units was modeled against the other forms of energy storage, such as electric vehicles and seawater desalination plant, with findings suggesting the potential economic advantage of storage other than grid connected batteries in a residential precinct.

Component sizing optimization and technoeconomic feasibility studies for stand‐alone power systems have been actively discussed in recent years. However, most models and studies overlook the importance of individual component performance, input data resolution and their integration with the system. This article compares the rapidly evolving battery storage technology applications using the context of a stand‐alone system, through a case study on Bruny Island, Tasmania, Australia, where the current electricity infrastructure is approaching its end of life. We constructed a mixed‐integer linear programming model to achieve optimal balance between modeling accuracy and computational complexity. The model was constructed to obtain the optimal component sizing on the basis of minimum lifetime net present cost. It was shown in our work that any transition of islands to become fully stand alone should be carefully considered, where a limited grid connection could still provide significant value to the infrastructure, greatly reduce its stress over peak hours. This concept was illustrated further with another set of model scenarios aiming to explore the performance of battery storage systems with different power output allowances, limited by the time‐series data resolution, were developed. It was shown that the selection of incomplete input data cycle, reliance on standardized average values and utilization of low resolution time‐series data could heavily skew the results of a model, as the use of incomplete dataset and oversimplified average values subtly conceal some of the critical sizing and operation issues in a technoeconomic feasibility study, impacting the accuracy of the model to reflect the real problem.

This study benchmarks cycle performance of electrolyte solutions containing novel bromine sequestration agents (BSA) in a zinc bromine flow battery. Five alternative BSA candidates – 1-ethyl-1-methylpiperidinium bromide ([C₂MPip]Br), 1-ethylpyridinium bromide ([C₂Py]Br), 1-(2-hydroxyethyl)-pyridinium bromide ([C₂OHPy]Br), 1-ethyl-3-methylimidazolium bromide ([C₂MIm]Br) and 1-(2-hydroxyethyl)-3-methylimidazolium bromide ([C₂OHMIm]Br) were investigated under operational conditions typical for zinc bromine flow batteries. Results were compared to the conventional BSA, 1-ethyl-1-methylpyrrolidinium bromide ([C₂MPyrr]Br). Electrolytes containing the various alternative BSAs were tested at bench scale in a full-cell battery setup under controlled electrolyte flow and temperature. The evaluated performance parameters were: voltaic efficiency, coulombic efficiency, energy efficiency and recoverable charge. A correlation between BSA–bromine bond strength and cycle performance was observed. Performance of the tested electrolytes varied widely, and gains in coulombic efficiency were generally offset by losses in voltaic efficiency. [C₂Py]Br and [C₂MIm]Br produced cycle performance improvements compared to the other BSAs studied.

Chloride-based supporting electrolytes are conventionally used in zinc/bromine (Zn/Br) and other flow batteries to ensure good conductivity during charge/discharge operation. This work presents preliminary results from experimental and periodic density functional studies of the interactions between chlorides and electrodeposited zinc generated during the charging phase of the Zn/Br system. Scanning electron microscopy and X-ray diffraction analysis show that even relatively low concentrations (0.5 M) of ZnCl₂ supporting electrolyte influences zinc electrodeposition behaviour during the charging phase, with a strong preference for the (004) orientation. Molecular modelling carried out in this work provides a foundation for understanding how chlorides present in the supporting electrolyte interact with and alter the electrodeposited zinc surface in Zn/Br flow batteries. Chloride strongly binds above the Zn(001) surface with binding energies of 260–288 kJ mol-1 at 0.11–0.33 ML coverage. Chloride binding lowers the Zn(001) surface uniformity, with higher coverage resulting in lower binding energies. These findings warrant further investigation of the influence and behaviour of supporting electrolytes on the primary electrolyte and at the electrode-electrolyte interface. While this work focuses on Zn/Br systems, the findings are also potentially applicable to other types of RFBs which utilise chloride-containing electrolytes.