Operational Carbon Footprint of the U.S. Water Sector’s Energy Consumption

Accounting of energy-related GHG emissions in the water sector have largely been conducted at single utilities or cities and rarely at a regional or country scale. In this study, we assess the carbon footprints of operational energy use for 76 wastewater utilities and 64 water utilities across the United States. Additionally, we investigate water-related GHG emissions at a sub-annual scale through three case cities to understand how GHG emissions change at the monthly scale. We estimate the total drinking water and wastewater GHG emissions associated with electricity, biogas, natural gas, and fuel oil consumption across the United States to be 26.5 x 109 and 20.1 x 109 kg CO2e respectively. We find the average GHG emissions per unit drinking water and wastewater emissions to be 0.463 kg CO2e/ m3 and 0.42 kg CO2e/ m3, respectively. The research provides insights into operational GHG emissions of the water sector and advances the understanding of temporal variations in the life-cycle of energy use

Modelling the dispersion of airborne pollutants in the Pretoria urban area

The theory and methodology of urban air pollution dispersion models are reviewed to provide the background for a critical approach to modelling atmospheric pollution in South African conditions. It is shown that there is no evidence to suggest the existence of a universally applicable modelling technique. Three models of various degrees of complexity, the Gaussian plume model for multiple sources, the ATDL-grid model and the Gifford-Hanna simple model, are applied to predict long-term concentrations of atmospheric sulphur dioxide in the Pretoria urban area and evaluated against observations. Whereas the ATDL-grid model does not adequately simulate air pollution levels during the main pollution season in Pretoria, more realistic results are obtained by the Gaussian plume model for multiple sources and the Gifferd-Hanna simple model. The refinements introduced into the two models to further improve their performance are presented. A closer association between predicted and observed SO2 concentrations is consistently obtained when an increasing number of wind and stability observations are used in the Gaussian plume model for multiple sources to simulate spatial variations in the dispersion conditions over Pretoria. The Gifford-Hanna simple model is refined by including estimates of hourly, monthly and seasonal air pollution concentrations. An objective weighting scheme is used in conjunction with experimental evidence to determine variations of the stability factor in the model. The methodology of future applications is discussed and it is shown that the refined Gifford-Hanna simple model provides a fast and inexpensive basis for predicting concentration levels of spheric pollutants from multiple sources with a degree of success comparable to the performance of the Gaussian plume model

VIRTUE : integrating CFD ship design

Novel ship concepts, increasing size and speed, and strong competition in the global maritime market require that a ship's hydrodynamic performance be studied at the highest level of sophistication. All hydrodynamic aspects need to be considered so as to optimize trade-offs between resistance, propulsion (and cavitation), seakeeping or manoeuvring. VIRTUE takes a holistic approach to hydrodynamic design and focuses on integrating advanced CFD tools in a software platform that can control and launch multi-objective hydrodynamic design projects. In this paper current practice, future requirements and a potential software integration platform are presented. The necessity of parametric modelling as a means of effectively generating and efficiently varying geometry, and the added-value of advanced visualization, is discussed. An illustrating example is given as a test case, a container carrier investigation, and the requirements and a proposed architecture for the platform are outlined