Parisa A. Bahri

The effect of applied shear stress on Botryococcus braunii, in the presence of solvent is important to further understanding the mechanisms behind in-situ solvent extraction and will be critical in the design and scale up of an effective extraction process. This paper looks at the effect of various mixing rates on colony structure and culture photosynthetic activity in the presence of heptane. Partial colony disruption was found to occur at shear rates of 335 s -1, with the main mechanism of disruption believed to be microeddies generated by turbulence around the impeller. Photosynthetic activity was seen to drop by 55 % during the extraction period requiring a short recovery time of 3 days, reaching 66.5 % of its original value. These results provide valuable insight and data on the shear limits of B. braunii required in the design of a repeated milking process and will assist in the design and scale up of a viable milking process.

The present study investigates the impacts of the implementation of the energy goal of SDGs (SDG 7) to national development plans on household sector energy demand of Indonesia. Three scenarios were developed: reference, current policy, and SDGs scenarios, which were simulated using the Long-range Energy Alternatives Planning system (LEAP). Results show that providing clean energy access for all Indonesian (Target 7.1 of SDG 7) will increase energy demand by 67 million GJ, by 2030. However, implementation of efficiency measures (Target 7.3) will cancel out this increase. This study also reveals and discusses other interesting findings.

When solar energy technologies are compared to the conventional energy production alternatives, they may require incentives and financial support due to their relatively high investment costs and low bidding offers in electricity markets. Tax and cash incentives are able to diminish the gap between the levelized cost of electricity and the power purchasing agreements in most of the projects. The purpose of this paper is to research the effect of combining a number of tax and cash incentives under different financial structures and to find the best combinations of support mechanisms by considering maximum reduction of levelized cost of electricity and minimum government cost, applied to Chile as a case study.

This paper presents a feasibility analysis for running a water treatment system by renewable energies in a regional town of Western Australia. The main motivation is the inadequate capacity in the electricity feeder supplying the town especially in summer. Instead of augmenting the feeder to the town to supply the electricity demand of the water treatment system, locally installed renewable energies seem to be sustainable, cost effective and attractive for the local electricity utility. This paper finds an economically attractive and technically feasible solution in the form of integrating a distributed system of rooftop solar photovoltaic systems with wind energy and existing grid to supply the energy demand of the town, as well as the new water treatment system. The proposed hybrid energy system provides electricity at a lower cost than the current energy solution, while improving the penetration of renewable energies in the region.

The essential connection between energy and water, also defined as the energy-water nexus, has been recognized by scientists and policy makers worldwide. Integrated solutions and policies that consider both energy and water aspects into future planning have been developing at a fast pace. In this paper, we review the state of the art of the energy-water nexus, with particular focus on the integration between renewable energy and desalination technologies. We also model the integration of reverse osmosis (RO) desalination and solar photovoltaics in an edge-of-grid coastal town in Western Australia. The current literature agrees on the sustainable use of renewable energy sources to improve the water-energy nexus in the context of water desalination. Although the integration of solar and wind energy with desalination technologies is a mature and well-proven solution at both small and large scales, the intermittency and fluctuating nature of wind and solar power still constitute the main technical challenge that has limited the diffusion of renewable energy powered desalination on a large scale. Several successful applications of renewable energy powered desalination in remote, off the grid, locations have tackled the issue of power intermittency by the use of batteries and diesel generators. Such systems often couple reverse osmosis desalination with solar photovoltaic energy. Large desalination plants have been successfully connected to wind farms and grid electricity to secure uninterrupted plant operations, thus meeting water targets in large-scale systems. Our review identifies a knowledge gap in the integration of decentralized energy systems, e.g. rooftop solar photovoltaic, with small scale RO desalination. Such configuration would benefit those regional towns that have historically suffered from weak and unreliable connections to the electricity grid, thus helping them secure both their energy and water requirements. The modelling exercise on a renewable energy powered RO plant in an edge-of-grid town in Western Australia has identified an operating strategy that maximizes the renewable energy fraction and secures the annual supply of water. The system involves operating the RO unit for six months of the year at a daily variable load and integrating solar energy with grid electricity. Careful evaluation of the RO performance under such operating conditions is necessary to ensure a safe and reliable water treatment process. A niche in the literature of the energy-water nexus has been identified in the integration of rooftop solar photovoltaic, grid electricity and desalination technologies applied in a regional context. A future study will consider the rollout of rooftop solar photovoltaic installations across the whole town, thus enabling the active engagement of the community by integrating the households’ energy demand response patterns to the operations of both rooftop photovoltaics and the desalination unit.

This paper presents a broad assessment of the energy production potential available from solid organic wastes when treated with anaerobic digestion in Sub-Saharan Africa (SSA). Energy production potentials were estimated by calculating the methane (CH4) production potential based on data from the Food and Agricultural Organization (FAO), studies done in urban centres on the organic fraction of municipal solid waste (OFMSW), livestock manure, livestock food waste, crop residues normally burned, and crop primary equivalent waste. The total CH4 production potential of organic solid wastes in SSA was estimated to be 12.8 billion m3/yr, equivalent to 133 million GWh/yr of heat energy. Given that current domestic biogas programmes in SSA focus on cattle manure as the main feedstock, the large energy production potential from other organic waste streams highlights the opportunity to improve waste management practices through harnessing these abundant waste resources in biogas systems.

A 5-L bioreactor was set up with an impeller, cooling and heating coils, probes for measuring pH, temperature and dissolved oxygen concentration. The reactor instrumentation was interfaced with a computer via data acquisition hardware. LabVIEW, a graphical programming language was used in all measurement and control programs. The reactor temperature control could be achieved by a conventional proportional-integral (PI) controller. In contrast controlling pH was difficult due to a considerable variation in the slope of the titration curve. A simple PI loop resulted in aggressive pH control actions, causing excessive base addition and likely demise of the microorganisms. In this work synthetic waste water was used for testing control schemes. The Generic Model Control (GMC) and gain-scheduling adaptive control strategies were investigated and compared with a PI control scheme. In these strategies, the rate change of pH was assumed to be a function of residence time, base addition, and pH, allowing the continuous calculation of base added against the pH measured. Some experimental and simulated results are presented for comparison.

The cobalt solvent extraction (CoSX) system using Cyanex 272 as the organic extractant, has been modelled for single, two and three stage extraction circuits using MATLAB and Aspen Custom Modeler (ACM) mathematical modelling software. Steady state simulations and optimisations have been conducted on the developed models. An initial sensitivity analysis has shown that increasing pH or the organic to aqueous (O:A) ratio significantly increases individual metal extraction efficiencies. However to achieve the ultimate aim of maximising cobalt extraction while minimising magnesium and nickel co-extraction and reagent consumption, an economic objective function has been formulated within the optimisation problem to solve for the optimum pH setpoint and O:A ratio. For this case study a two stage Co SX circuit with the (O:A) ratio at 0.162 and pH at 4.64 was found to be optimal. This set of conditions would achieve 99% cobalt extraction, while limiting magnesium co-extraction to 9% and nickel co-extraction to <0.5%.

In this paper an innovative method for one and seven-day forecast of electricity load is proposed. The new approach has been tested on three different cases from south-west Western Australia's interconnected system. They have been tested under the most realistic conditions by considering only minimum and maximum forecasts of temperature and relative humidity as available future inputs. Two different nonlinear approaches of neural networks and decision trees have been applied to fit proper models. A modified version of mean absolute percentage error (MMAPE) of each model over the test year is presented. By applying a developed criterion to recognize the dominant component of the electricity load, user of this work will be able to choose the most efficient forecasting method.