Search

Several simple vapour cooling and pre-condensing concepts were assessed for the purpose of mitigating bubble column vapour temperatures, a critical aspect for the development of a bubble column driven greenhouse desalination system. Particular emphasis was on low-energy demand of the devices, ease of manufacture, low investment cost and technical and operational appropriateness for local people in remote places. Under laboratory conditions, the copper tube type I and II concepts achieved water recovery rates of between 65 and 75%. The water-tank cooled tube achieved 83% condensate recovery, albeit at the cost of large cooling water requirements, whereas the air cooled andpassive sleeve-cooled bubble condenser columns achieved condensate recovery rates of at least 50% under favourable ambient conditions. A “self-cooling” effect was observed for thepassive sleevecolumns that could perhaps be tailored to produce small quantities of potable water in hot and arid regions. Theeffectiveness–NTU method was used to allow for a meaningful comparison between the devices. While the majority of the tested concepts represented a “single-stage” approach to the humidification–dehumidification cycle, it is stressed that a well-designed latent heat recovery system would be crucial for the economic viability of a bubble greenhouse. [ABSTRACT FROM AUTHOR]

This paper describes the development and experimental evaluation of a novel bubble column-based humidification–dehumidification system, for small-scale desalination of saline groundwater or seawater in remote regions. A bubble evaporator prototype was built and matched with a simple flat-plate type condenser for concept assessment. Consistent bubble evaporation rates of between 80 and 88 ml per hour were demonstrated. Particular focus was on the performance of the simple condenser prototype, manufactured from rectangular polyvinylchlorid plastic pipe and copper sheet, a material with a high thermal conductivity that quickly allows for conduction of the heat energy. Under laboratory conditions, a long narrow condenser model of 1500 mm length and 100 mm width achieved condensate recovery rates of around 73%, without the need for external cooling. The condenser prototype was assessed under a range of different physical conditions, that is, external water cooling, partial insulation and aspects of air circulation, via implementing an internal honeycomb screen structure. Estimated by extrapolation, an up-scaled bubble desalination system with a 1 m2condenser may produce around 19 l of distilled water per day. Sodium chloride salt removal was found to be highly effective with condensate salt concentrations between 70 and 135 µS. Based on findings and with the intent to reduce material cost of the system, a shorter condenser length of 750 mm for the non-cooled (passive) condenser and of 500 mm for the water-cooled condenser was considered to be equally efficient as the experimentally evaluated prototype of 1500 mm length. [ABSTRACT FROM PUBLISHER]

Many metropolitan areas have a high dependency on Seawater Reverse Osmosis (SWRO) desalination plants for bulk water supply. Location and scale decisions are important for SWRO desalination plants owing to the significant environmental costs associated with long distance water pumping. The aim of this study is to introduce a Geographical Information System (GIS)-based method to assist such site-specific decisions. The method has 3 stages. Stage 1 uses GIS to identify feasible plant locations and water demand areas. Stage 2 develops a range of scenarios that balance plant size and number with water demand. In stage 3, the preferred scenario is selected based on environmental life cycle assessment. The method’s applicability was tested using data for the northern corridor of Perth, Western Australia (WA). Spatial water demand and suitable vacant land for accommodating SWRO plants in the case study are obtained in Stage 1. Based on these spatial data, two water planning options are designed in order to supply desalinated water to the demand area. The first option consists of a large SWRO desalination plant and its connected trunk main which supplies water into the demand centrally (centralized scenario). Second option consists of five medium-sized SWRO desalination plants integrated within the demand area (distributed scenario). The best scenario for environmental performance was found to be the distributed scenario which has 18% less GHG emission compared to centralized scenario. This method is adaptable to other case studies for identifying optimal SWRO plant sizes and locations based on environmental criteria. [ABSTRACT FROM PUBLISHER]

A quantitative framework for sustainable desalination planning in metropolitan areas, which integrates the tools of mixed integer linear programming and life cycle assessment, is presented. The life cycle optimisation framework allows for optimal desalination planning by considering choices over intake type, staging and location of the infrastructure under different land-use, environmental and economic policies. Optimality is defined by the decision maker's selected objective function, being either an environmental impact or a levelised cost indicator. The framework was tested for future desalination planning scenarios in the northern metropolitan area of Perth, Western Australia. Results indicate that multi-staged construction and decentralised planning solutions may produce lower life cycle environmental impacts (58%) and at a lower levelised cost (24%) than a centralised desalination solution currently being considered by Western Australian water planners. Sensitivity analysis results suggest that the better environmental and economic performance of decentralised planning over centralised planning is highly sensitive to the proportion of land that can be made available for the siting of decentralised plants near the demand zone. Insight into land use policies is a critical factor to the initiation and success of decentralised solution in developed metropolitan areas. [ABSTRACT FROM AUTHOR]

This study presents comparative life cycle assessments (LCAs) and levelised cost (LC) analyses of desalination supply systems, integrated with a spatial–temporal model at three geographical scales: a centralised scenario and two alternative decentralised scenarios . For the centralised scenario we focused on a proposed 320,000 m 3 /day SWRO desalination plant to support future urban expansion in the northern corridor of Perth, Western Australia. The alternative, decentralised scenarios each integrate several medium sized plants into the same geographical water demand area as the centralised scenario and also produce 320,000 m 3 /day in total. Results indicate that environmental impacts would be ~ 20% lower and LC 7% to 18% lower for the decentralised scenarios than for the centralised scenario . Contribution analysis revealed that, for the centralised scenario , although economies of scale resulted in lower environmental impacts from the desalination plant construction and operation phases, these savings were outweighed by the environmental impacts associated with the construction and operation of the water transfer mains required to connect the large plant to the network. Perth water stakeholders and policy makers can use our results to inform development decisions, and the proposed LCA method can be implemented in other metropolitan areas for desalination planning. [ABSTRACT FROM AUTHOR]

The Bubble-Greenhouse system combines the well established Seawater Greenhouse concept with a novel humidification–dehumidification (HD) process, based on the large air/water interface generated by bubbling air through a water filled column. Multistage bubble evaporators and multistage bubble condensers allow for effective recovery and reuse of latent heat via a heating/cooling circuit throughout all column stages. The system can operate with salinities of 5000–35,000 ppm. Following the HD process, cooled vapour provides the tropical type greenhouse with a humid environment for selected crops. Additional condensation occurs along the greenhouse skin and is gravity-fed to drip line irrigation. Low grade energy options such as solar-thermal, photovoltaic, wind, geo-thermal and salinity-gradient solar ponds provide the energy for the Bubble-Greenhouse. Alternatively, waste heat from diesel power stations nearby can provide cogeneration of electricity and bubble evaporator heat and pressure requirements. Crops grown inside a greenhouse demonstrate a strongly reduced water demand and the closed environment protects crops from insects and diseases. As the technology is conceptually simple to implement, it holds great potential for community participation, empowerment, skills development and capacity building of local people in remote locations. [ABSTRACT FROM AUTHOR]

Abstract: This paper evaluates life cycle Greenhouse Gas (GHG) emissions of a Seawater Reverse Osmosis (SWRO) desalination plant and assesses its performance under three power supply scenarios. A Life Cycle Assessment (LCA) analysis is conducted for a plant located in Perth, Western Australia (WA). Input and output flows of SWRO plant are based on literature and Perth desalination plants. The Simapro Australian and Ecoinvent databases are used for operational phase Life Cycle Inventory (LCI). An LCI for the construction phase of the plant is developed using economic input–output analysis. Electricity supply scenarios are “100% WA grid”, “100% wind energy” and “92% wind energy plus 8% Photovoltaic (PV) solar energy”. Results indicate that renewable energy powered desalination plants achieve GHG emissions reduction of ∼90% compared to the plant powered by WA grid scenario. For the plant powered by fossil based grid electricity, electricity use in the operational phase is found to be responsible for more than 92% of its GHG emissions. On the other hand, for the plants powered by renewable energy, the highest contribution belongs to chemical use in the operational phase (60%) followed by the construction phase (17%). Indirect emissions due to the electricity consumption in the chemical, wind turbine and PV solar panel manufacturing are found to contribute the lion's share (36–39%) of the life cycle emissions for the renewable energy powered desalination plants. Any improvement in fuel mixes in grid electricity towards cleaner energy sources can be beneficial by reducing impacts associated with upstream electricity use in manufacturing. This work provides the first reference to identify and quantify supply chain contributions to the overall environmental impact associated with renewable energy powered desalination plants. [Copyright &y& Elsevier]