Large scale integration of wind power: moderating thermal power plant cycling

Power plant cycling in thermal plants typically implies high costs and emissions. It is, therefore, important to find ways to reduce the influence of variations in wind power generation on these plants without forsaking large amounts of wind power. Using a unit commitment model, this work investigates the possibility to reduce variations by means of a moderator, such as a storage unit or import/export capacity. The relation between the reduction in CO₂‐emissions and the power rating of the moderator is investigated, as well as the benefit of a moderator which handles weekly variations compared with a moderator which has to be balanced on a daily basis. It is found that a daily balanced moderator yields a decrease in emissions of about 2% at 20% wind power grid penetration. The reduction in emissions is mainly due to an avoidance of start‐up and part load emissions and a moderator of modest power rating is sufficient to achieve most of this decrease. In the case of a weekly balanced moderator, emissions are reduced as the moderator power rating increases. At 40% wind power grid penetration, a weekly balanced moderator reduces emissions with up to 11%. The major part of this reduction is due to the avoidance of wind power curtailment. The simulated benefit (CO₂‐emissions and costs) from adding a general moderator is compared with emissions from Life Cycle Assessment (LCA) studies and cost data of five available moderator technologies; transmission capacity, pumped hydro power, compressed air energy storage, flow batteries and sodium sulphur batteries. Copyright © 2010 John Wiley & Sons, Ltd.     

Impacts of large amounts of wind power on design and operation of power systems,results of IEA collaboration

There are dozens of studies made and ongoing related to wind integration. However, the results are not easy to compare. IEA WIND R&D Task 25 on ‘Design and Operation of Power Systems with Large Amounts of Wind Power’ collects and shares information on wind generation impacts on power systems, with analyses and guidelines on methodologies. In the state‐of‐the‐art report (October, 2007), and the final report of the 3 years period (July, 2009) the most relevant wind power grid integration studies have been analysed especially regarding methodologies and input data. Several issues that impact on the amount of wind power that can be integrated have been identified. Large balancing areas and aggregation benefits of wide areas help in reducing the variability and forecast errors of wind power as well as help in pooling more cost effective balancing resources. System operation and functioning electricity markets at less than day‐ahead time scales help reduce forecast errors of wind power. Transmission is the key to aggregation benefits, electricity markets and larger balancing areas. Best practices in wind integration studies are described. There is also benefit when adding wind power to power systems: it reduces the total operating costs and emissions as wind replaces fossil fuels and this should be highlighted more in future studies. Copyright © 2010 John Wiley & Sons, Ltd.     

SPATIAL AND TEMPORAL CHANGES IN TOTAL SUSPENDED SEDIMENT CONCENTRATIONS IN AN OXBOW LAKE AFTER IMPLEMENTING AGRICULTURAL LANDSCAPE MANAGEMENT PRACTICES

The Wolf–Broad oxbow lake (417 ha) was evaluated by the Mississippi Department of Environmental Quality and included on the Mississippi 303(d) list of impaired waterbodies for total suspended solids (TSS). A study was undertaken for 2 years to evaluate and document changes to TSS (mg L^?1) and overall lake turbidity (NTU) through best management practice implementation. These two objectives were analysed with routine monthly surface sampling events of turbidity (Eureka Manta 2, automated data sonde) as well as 20 random samples per sampling trip for TSS from June 2008 to June 2010. Results from a non‐parametric Kruskal–Wallis analysis indicated a significant month‐by‐year effect on turbidity and TSS (chi‐squared = 76.08, p = 0.001), but reach (chi‐squared = 2.45, p = 0.784) and depth by reach (chi‐squared = 2.44, p = 0.784) did not show significant effects on turbidity. There were no significant correlations between TSS concentrations and turbidity and 2 days and 7 days summed or mean rainfall for the duration of the evaluation. Spearman correlation analysis for TSS indicated significant correlations between TSS and mean two‐day (r² = 0.62, p = 0.002) and seven‐day (r² = 0.51, p = 0.014) wind speeds. All other variables used in the analysis did not show significant correlation with TSS ( p > 0.05). This suggests that wind conditions, rather than rainfall, predict the greatest variability in TSS and turbidity in Wolf Lake. These documented correlations between lake water column TSS, turbidity and wind highlight the difficulties of demonstrating success of management practices in the short temporal period between project initiation and completion. Unmanageable environmental conditions (wind speed and direction) and limited temporal monitoring scales (1 1/2 years post‐BMP implementation) limit the possibility of demonstrating successful water‐quality improvement within a 303(d) listed waterbody such as Wolf Lake. Copyright © 2011 John Wiley & Sons, Ltd.     

Model-based Regional Assessment of Water Use An Example for Semi-arid Northeastern Brazil

Abstract

Water use assessments are a necessary prerequisite for sustainable water resources management and planning in river basins, federal states, or countries. For reasons of transparency, flexibility, ease of update, and the possibility to generate scenarios of future water use, such assessments are best carried out by applying a water use model. To support water resources planning in two federal states of semi-arid Northeastern Brazil, Ceará and Piauí, the regional-scale water use model NoWUM was developed. It computes withdrawal and consumptive water use for each of 332 municipalities, distinguishing five water use sectors: irrigation, livestock, households, industry, and tourism. The model is suited to simulate the impact of global change and of management measures on water demand. Using NoWUM, the present-day water use situation in Ceará and Piauí is assessed. In addition, the impact of inter-annual climate variability and long-term climate change on irrigation requirements is considered. Scarce and uncertain input data lead to a high level of uncertainty in the model results. It is likely that water use in the most important sector, irrigation, is underestimated, while industrial water use is possibly overestimated. With some modifications, NoWUM has the potential to be applied for water use assessments in other data-poor regions of the globe.     

Assessment of Water Quality Management in Turkey

Abstract

There has been a noticeable increase in the amount of pollution in water resources in Turkey in recent years. Negative environmental developments, such as industrialization, increasing urbanization, improper pesticide and fertilizer applications in agricultural lands, and the drainage of domestic and industrial wastewater into water resources without any waste treatment applications, cause rapid pollution of both surface and groundwater resources. Therefore, it is necessary to allocate more attention to water resources monitoring and evaluation studies to prevent the pollution of water resources, and to reclaim these resources.     

Soil productivity analysis based on a fuzzy logic system

BACKGROUND: Maintaining soil productivity is essential if agriculture production systems are to be sustainable. However, there is a paucity of tools for measurement for the purpose of understanding changes in soil productivity. Fuzzy logic‐based analysis offers this possibility. It is a new method on the evaluation of soil productivity in Turkey and even in the world. RESULTS: Values for pH, salinity, carbonate and organic matter were entered into the system as input variables so as to obtain soil productivity as the output. After the membership functions related to input and output were determined, rules were created. Then, the fuzzy logic system was applied separately to pH, salinity, lime and organic matter values of different soil types present in the Kocaeli region with the aim of obtaining corresponding fuzzy values. Thus, soil productivity profiles of the region were deciphered. CONCLUSION: Organic matter levels in the study field remained below 30 g kg^?1 and varied between 22 and 28 g kg^?1. Productivity values were obtained as a percentage and varied between 16.9% and 18.1%. The lime content of the study soils varied in the range of 33–88 g kg^?1. Average totals for salt values of the field changed between 0.58 and 0.77 g kg^?1. Copyright © 2010 Society of Chemical Industry     

Roles of Water and Solids Composition in the Control of Glass Transition and Stickiness of Milk Powders

Abstract: Plasticization and glass transition of amorphous components in food powders often result in stickiness and caking. The glass transition temperature (T_g) of milk powders was measured by differential scanning calorimetry (DSC) and a viscometer method was used to determine sticky-point temperatures. Water sorption isotherms were established for varying solids compositions. Lactose contents were analyzed by high-performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD) and proteins were identified using SDS-PAGE gel electrophoresis. Solids composition and water affected both the T_g and stickiness behavior. Stickiness was governed by carbohydrates and water plasticization. At low protein contents, precrystallization of lactose decreased the sticky point temperature, but increasing protein content in all milk powders decreased stickiness at all water activities. The results showed that glass transition can be used to describe time-dependent stickiness and crystallization phenomena, and it can be used as a parameter to control and reduce stickiness of dairy solids with various compositions. Practical Application: Glass transition of component sugars in milk powders with various water contents was responsible for a solid-liquid transformation which resulted in their viscous flow at particle surfaces and stickiness of the powders. Stickiness leads to wall deposition in dehydration and caking of powders in storage when the amorphous carbohydrate-rich components gain liquid characteristics. High protein contents in milk powders decreased stickiness, but precrystallization of lactose prior to spray drying increased stickiness at low protein content. Milk powders in storage gained higher water contents with increasing protein contents, but stickiness was reduced and lactose crystallization was delayed which improved storage stability.     

Simultaneous determination of type A,B and D trichothecenes and their occurrence in cereals and cereal products

A sensitive LC–MS/MS method for the simultaneous determination of type A, B and D trichothecenes in cereals is presented. The limits of detection ranged between 0.1 and 0.7 µg kg^?1 for all analytes. The method was applied to 289 representatively drawn samples of wheat, rye and oat products. Ninety-four percent of the wheat samples (n = 130), 95% of the rye samples (n = 61) and 100% of the oat samples (n = 98) were contaminated with the type A trichothecenes T-2 and HT-2 toxin. Median levels of T-2/HT-2 (sum of the toxins) were 0.91, 0.53 and 8.2 µg kg^?1, respectively. Highest levels were found in wheat bran (24 µg kg^?1), rye kernels (3.1 µg kg^?1) and oat flakes (85 µg kg^?1). All wheat and rye samples and 75% of the oat samples were contaminated with the type B trichothecene deoxynivalenol. Median levels of this toxin were 23, 15 and 0.53 µg kg^?1, respectively. Highest levels were found in wheat bran (1160 µg kg^?1), rye kernels (288 µg kg^?1) and oat flakes (55 µg kg^?1). The type B trichothecene nivalenol was detected in 67% of the wheat samples, in 3% of the rye samples and in 24% of the oat samples with highest levels in wheat bran (96 µg kg^?1), rye kernels (1.8 µg kg^?1) and in oat flakes (17 µg kg^?1), respectively. Levels of other type A and B trichothecenes played a minor role, although the rates of contamination were often high. Neither macrocyclic type D trichothecenes (satratoxin G and H, verrucarin A, roridin A) nor diacetylverrucarol and verrucarol (type A trichothecenes), were detected in any of the samples.     

The Computational Modeling of Transitional Flow through a Transonic Linear Turbine: Comparative Performance of Various Turbulence Models

Aero-thermal characteristics of transitional flow through a highly loaded transonic linear turbine are studied at the design incidence using computational methods. The three-dimensional compressible turbulent flow through a turbine inlet guide vane is simulated using finite-volume method-based fluid flow solutions using both Reynolds-averaged Navier Stokes (RANS) equations-based turbulence models, and a dynamic large eddy simulation (LES) approach which is based on a Smagorinsky-Lilly subgrid scale (SGS) model. The calculations are made for exit isentropic Mach numbers ranging from 0.7 to 1.1, and for Reynolds numbers ranging from 5 × 10⁵ to 2 × 10⁶. The numerical results obtained from different turbulence model simulations are compared with each other, and with the experimental data available in the open literature in terms of integrated flow parameters, such as pressure and heat transfer coefficients for varying exit Mach and Reynolds numbers. The present numerical approach indicates a guide line that the present LES approach can be a reliable choice for turbomachinery flows.