Wind Power: The Economic Impact of Intermittency

Wind is the fastest growing renewable energy source for generating electricity, but economic research lags behind. In this study, therefore, we examine the economics of integrating large-scale wind energy into an existing electrical grid. Using a simple grid management model to investigate the impact of various levels of wind penetration on grid management costs, we show that costs of reducing CO2 emissions by relying more on wind power depend on the generation mix of the existing electricity grid and the degree of wind penetration, with costs ranging from $21 to well over$1000 per tonne of CO2 reduced. Costs are lowest if wind displaces large amounts of fossil fuel production and there is some hydroelectric power to act as a buffer. Hydro capacity has the ability to store wind generated power for use at more opportune times. If wind does nothing more than replace hydro or nuclear power then the environmental benefits (reduced CO2 emissions) of investing in wind power are small.Wind power, carbon costs, electricity grids, mathematical programming

Network Constrained Wind Integration: An Optimal Cost Approach

Planning electricity supply is important because power demand continues to increase while there is a concomitant desire to increase reliance on renewable sources. Extant research pays particular attention to highly variable, low-carbon energy sources such as wind and small-scale hydroelectric power. Models generally employ only a simple load levelling technique, ensuring that generation meets demand in every period. The current research considers the power transmission system as well as load levelling. A network model is developed to simulate the integration of highly variable non-dispatchable power into an electrical grid that relies on traditional generation sources, while remaining within the network’s operating constraints. The model minimizes a quadratic cost function over two periods of 336 hours, with periods representing low (summer) and high (winter) demand, subject to various linear constraints. The model is numerically solved using Matlab and GAMS software environments. Results indicate that, even for a grid heavily dependent on hydroelectricity, the addition of wind power can create difficulties, with system costs increasing with wind penetration, sometimes significantly.Electric networks, optimal power flow, wind power, intermittent sources

Economic Analysis of Feed-in Tariffs for Generating Electricity from Renewable Energy Sources

Feed-in tariffs, renewable energy

Stochastic Assessment of Nigerian Wood for Bridge Decks

This presentation assures the suitability of Nigerian wood using a stochastic safety evaluation method for bridge decks. A timber bridge deck is modeled in accordance to current specifications, to represent real life experiment in order to depict the structural behavior of planks when used as bridge decks. This model is then subjected to some degree of entropy using Advance Second Moment Reliability Assessment (ASMRA) method, which is then subsequently analyzed using JAVA library with the help of Flanagan polynomial. It is observed that, strength classes, timber thicknesses and stringer spacings are the major factors among others influencing the structural behavior of Nigerian timber species proposed as bridge decks material. Therefore, the major classes of the timber recommended for bridge decks are those within the strength classes N1 to N4and with dimensions ranging from 100 x 250mm to 150 x 300mm on stringers spaced not greater than 300mm. These strength classes with their corresponding material properties can be a source of sustainable bridge decks material over a reasonable period of time as indicated by the probability of failure as a result of damage due to load accumulation. In view of this, timber which is a locally available material can be used as supplement for bridge decks to substitute for the expensive concrete and steel which are the most commonly used materials and substantially reduce the cost of decks. Also, abandoned bridges with defects only in their decks in both rural and urban locations can be effectively rehabilitated in order to improve traffic flow, economic activities and the quality of life of the people.http://dx.doi.org/10.4314/njt.v34i2.

Damage prediction of low-rise buildings under hurricane winds

Low-rise buildings are defined as the buildings with a mean roof height less than the least horizontal dimension and less than 18.3 m in ASCE 7-10. They represent the majority of commercial, residential, and industrial buildings. Approximate 90% of the existing low-rise residential buildings are constructed as wood light-frame buildings that are not fully engineered and thus more vulnerable to extreme wind pressures, wind borne debris and rain water intrusion. The resulting hurricane-induced economic loss is primarily attributed to the insufficient performance of building envelope instead of the catastrophic failure of their main structural system for Category 1 to 4 hurricanes. The limitations of the current public hurricane loss prediction models for low-rise buildings motivate the current study. Firstly, the wind loading is estimated by modifying the ASCE 7 or other design provisions that envelope the peak wind pressure in limited building surface zones for design purpose. It is difficult to modify those non-contemporaneous wind pressure coefficients close to realistic simultaneous wind loads accurately and to exclude the structural resonant portion on gust effect factor G that is built in with pressure coefficient Cp in most scenarios defined as ASCE 7-10. Secondly, the empirically prescribed tributary area, load path and load sharing may be reasonable for design on the conservative side, but not suitable for damage prediction that demands accurate instead of conservative load distribution among the entire system. Thirdly, most current standards are developed by obtaining equivalent pressure coefficients that envelope the peak responses calculated from wind tunnel data for a range of assumed structural wind resisting system without appropriate attention on building envelope. Currently, the prediction of the mean recurrence interval for peak structural responses under wind loading is achieved by integrating local meteorology data, wind tunnel aerodynamic database, and refined Finite Element analysis techniques as Database Assisted Design does. Those efforts are mainly focused on main wind force resistance system in the past and are extended to evaluate the building envelope performance in this study. The major objectives of this study include to (1) initiate a Database-assisted damage prediction framework for both main wind force resistance system and components and claddings, (2) collect aerodynamic datasets on scaled models by wind tunnel testing, (3) develop a comprehensive and in-depth 3D Finite Element model for both building frame system and its envelope, and qualitatively validate the analytical model under realistic wind pressures with limited available post disaster reports, (4) numerically predict the detailed structural responses for ongoing quantitative validation against the full scale static tests conducted by Florida International University, and (5) develop the vulnerability curves for a selected roof corner sheathing panel by using a database assisted stochastic finite element modeling approach

Development of preservative-treated cross-laminated timber and lignin-reinforced polyurethane-adhesive for glued laminated timber

Interest in the use of mass timber in building and construction is growing worldwide, this is due to the structural integrity and reduced environmental footprint of timber-based structures. Concerns associated with the biological and environmental degradation of mass timber necessitate the development of adequate protection strategies to ensure the durability of these products. Preservative treatment is a proven technique that increases the durability and performance of wood in-service and can also be applied to large-sized timber panels such as cross-laminated timber (CLT). Therefore, this study focused on investigating the feasibility of treating prefabricated 3- and 5-layer CLT panels with Copper-azole type C (CA-C) and micronized copper azole (MCA) preservatives. Further, we studied the effects of panel layup and thickness on the preservative impregnation in CLT. Based on the experimental results, we found adequate preservative penetration and retention in the treated 3- and 5-layer CLT panels, particularly in CA-C treated panels. Also, the lengthwise layup shows better treatment results in both CA-C and MCA-treated panels. In addition to the preservative-treatment of CLT panels, this dissertation covers the development of lignin-reinforced polyurethane adhesive (PUR) for bonding glue-laminated timber (Glulam). Herein, the glulam were fabricated and bonded using lignin-reinforced PUR at different wt% (1, 2, and 3) and tested for shear strength, wood failure and delamination. The lignin-treated PUR samples showed improved adhesion properties via high shear strength and reduced delamination compared to the control specimens. Thus, the lignin-reinforced PUR adhesive shows great potential as a bio-based and environment-friendly wood adhesive for producing glulam used in structural applications

State of Structural Timber Fire Endurance

The paper is motivated by the need for information relating to the design and behavior of wood structural components. Such information is critically reviewed. Most standard conventional components have been five tested under the sponsorship of materials suppliers or designers. However, only the fire endurance of floors and columns have both models and experimental evidence available for use. Models for the fire endurance of heavy timber, or glulam, beams are presented that are based on reduction of the cross section with duration of fire exposure and a reduction of strength of the outer fibers. Essentially no experimental information is available on model effectiveness. No models for the performance of wood-base wall systems were found, but extensive experimental ratings exist. To facilitate further research, a review of the influence of fire on wood and wood properties is given. Included are strength and deformation under load, charring of solid sections and panels, temperature distribution, and thermal properties. Research needs, in addition to filling the gaps found, include: analysis of risk based upon both variability of the "fire load" and "structural fire resistance"; and benefit/cost analyses on fire protection

Bio-based building skin

This book provides a compendium of material properties, demonstrates several successful examples of bio-based materials’ application in building facades, and offers ideas for new designs and novel solutions. It features a state-of-the-art review, addresses the latest trends in material selection, assembling systems, and innovative functions of facades in detail. Selected case studies on buildings from diverse locations are subsequently presented to demonstrate the successful implementation of various biomaterial solutions, which defines unique architectural styles and building functions. The structures, morphologies and aesthetic impressions related to bio-based building facades are discussed from the perspective of art and innovation; essential factors influencing the performance of materials with respect to functionality and safety are also presented. Special emphasis is placed on assessing the performance of a given facade throughout the service life of a building, and after its end. The book not only provides an excellent source of technical and scientific information, but also contributes to public awareness by demonstrating the benefits to be gained from the proper use of bio-based materials in facades. As such, it will appeal to a broad audience including architects, engineers, designers and building contractors. ; Presents case-studies and latest trends in material selection, assembling systems, and innovative functions of facades Discusses structure morphologies and aesthetic impressions related to bio-based building facades Highlights factors influencing performance of facades, with a special focus on service life of the buildin