Techno-economic evaluation of pipeline compression system: economic evaluation of the natural gas pipeline compression system - part 3

This paper presents the evaluation of the life cycle cost (LCC) of the natural gas pipeline investment using ‘’techno-economic and environmental risk assessment’’ (TERA) technique. The significance of this paper is to evaluate the cost implication of all the parts of this research work. The selected engines models for the gas compressor drive were developed based on public domain specification, using an inhouse engine performance simulation software: TURBOMATCH. The gas turbine engines were modelled to run at constant power amid high ambient temperature. The performance results were further used for the economic investigation using a developed model in MATLAB. These were investigated with respect to three seasons (winter, dry and hot season) of the years based on the location of this project (Trans- Saharan gas pipeline with 18 compression stations). Three economic conditions of 0%, 2% and 4% escalation rate of fuel and maintenance cost were investigated to analyse the LCC. The results obtained shows that the total LCC for the 0% escalation rate was approximately $32.01 billion. The fuel cost was 39.60% of the total LCC for the entire project. The operating and maintenance (O&M) costs, gas turbine, gas compressor, the pipeline with all accessories costs and emission tax attracted 10.1%, 6.89%, 9.95%, 28.89%, and 4.57%, respectively of the total life cost. The result also depicted that 2% and 4% escalation rate of fuel and O&M cost on the LCC result in 19.5% and 47.8% increased, respectively when compared with the 0% escalation rate at the end of project life. The result of the overall life-cycle cost of the pipeline investment represents the operational cost of the system. The proposed approach will help operators on the real potential cost of pipeline investment, taking into account the different cost element and ambient condition of the natural gas pipeline system. Importantly, this model can be applied or adapted to any natural gas pipeline transportation business

Residual stress consideration in fatigue damage of offshore wind turbine monopiles: to be or not to be?

The purpose of this paper was to investigate the impact of residual stresses on fatigue damage of offshore wind turbine monopiles by numerical analysis approach using ABAQUS software, a finite element analysis (FEA) tool. Three monopile models with the same dimension (within standard range) have been developed in ABAQUS and partitioned circumferentially into equal rings. Longitudinal partitions have been rotated through 180° as obtainable in practice. Characteristic loads typical of a real life offshore wind turbine environment have been applied to all three models, with tensile and compressive residual stresses applied as additional loads at the critical weld region to the first and second models while the third model had no additional load. With zero boundary conditions applied in all six degrees of freedom, the simulation has been run for 107 cycles of wind and wave loads as recommended in standards in each case. Stress results obtained from the critical weld region in the three models showed that the presence of tensile residual stresses equal to the material yield stress contributed a maximum 0.05% to fatigue damage of the monopile when compared with results from the model with no residual stress while the presence of compressive residual stresses with the magnitude of the yield stress of the material caused a gain of 0.06% in fatigue life by similar comparison, indicating negligible contribution of residual stresses to the stress build up in the critical weld region, thus suggesting that the magnitude of the residual stress as high as the yield stress of the material of the monopile is not large enough to cause the monopile to open up in the axial directio

Economic optimization from fleets of aero-derivative gas turbines utilising flared associated gas

Associated gas is been wasted to flaring in some parts of the world. The use of these flared gases for both industrial and economic purposes would be very beneficial. This paper presents the development of a model for optimizing the economic return of fleets of gas turbines utilizing flared associated gas. The paper further analyzed the impact of gas turbine degradation on the optimized divestment times of the redundant engines and the economic use of associated gas. Hypothetical but realistic gas turbines were modeled using the Cranfield University performance simulation tool, TURBOMATCH. In furtherance with the investigation, the Techno-Economic and Environmental Risk Assessment (TERA) framework has been adopted for a broad and multi-dimensional optimization of the economic return from the fleets. The results were employed in three degradation scenarios (optimistic, medium, and pessimistic) within the TERA framework to generate economic models. Genetic Algorithm (GA) in MATLAB was used in carrying out optimization to maximize the economic benefit. The result showed that an increase of 1.0% and 1.6% in the energy and net present value (NPV) respectively of the optimized clean fleet as against the baseline were achieved. The economic performance of the fleets shows the optimized fleet (clean) having the highest NPV of $2.84b and the pessimistic degraded fleet having the least NPV of$2.39b. More results revealed that degradation reduced the NPV of the project by 4.0%, 9.1%, and 15.8% for the three different degradation scenarios. This paper has proposed a model that can be used for the profitable economic utilization of associated gas which would be useful to gas turbine operators and investor

Social media usage for computing education:the effect of tie strength and group communication on perceived learning outcome

Abstract Social media has become an important platform where users share, comment, discuss, communicate, interact, and play games. Aside from using social media for personal, social, and business purposes, the use of social media has gained attention, particularly for collaborative learning in the educational sector. This paper examines the role of social media in computing education based on the use of WhatsApp social media group. Additionally, the study explores how social media usage by students influences their perceived learning outcomes. Given these aims, the study formulated four research hypotheses and tested using Partial Least Square Structural Equation Modelling. With the participants of three hundred and thirteen (n=313) students, the study found a positive relationship between social media usage for computing education and perceived learning outcomes. In addition, the study found a linear relationship between communication ingroup and perceived learning outcomes. Finally, the study revealed that social media positively relates to tie strength, and that tie strength influences in-group communication