排序方式： 共有32条查询结果，搜索用时 15 毫秒
1.
Lauri PuroAuthor VitaeJeffrey E. TeichAuthor Vitae Hannele WalleniusAuthor VitaeJyrki WalleniusAuthor Vitae 《Decision Support Systems》2011,51(1):31-41
We define and identify bidding strategies in real-life small loan auctions (Prosper.com). In such auctions, lenders bid for borrowers' loan listings and the winners get to fund the loan at an interest rate determined by the auction. The exceptionally large empirical database provided by Prosper.com offers a unique opportunity to test and further develop the theory of online auctions. This study shows that bidding behavior is not homogeneous among bidders, as the traditional auction theory suggests. Instead, bidders use many different bidding strategies. Moreover, learning and bidders' consistency over time in different auctions is studied. 相似文献
2.
The challenge of wind integration is to make best use of the variable and uncertain power source while maintaining the continuous balance between consumption and generation and high level of reliability in the power system. There is already experience of operating power systems with large amounts of wind power and integration studies give estimates on wind power impacts. Power systems are equipped to handle variability and uncertainty that comes from the electricity consumption, the load. Short‐term wind forecasting is required to manage large amounts of wind power. The main impacts of wind integration are investments in grid infrastructure and efficiency losses in power plants when following the increased variations and uncertainty in the power system. Wind power will lower emissions while replacing energy produced by fossil fuels and can also replace some power plant capacity. However, wind's lower capacity value compared to conventional power plants is one integration impact of wind power, meaning higher total installed capacity in power systems with high wind penetration. Managing options for wind integration impacts includes proper wind power plant grid‐connection rules, increasing transmission capacity and increasing flexibility that is available from generation plants and demand side. Further development of models and tools is required to study how entire power systems can be operated during the hours and days of very high penetration levels covering 60–80% of load. This article is categorized under:
- Wind Power > Systems and Infrastructure
- Wind Power > Climate and Environment
- Fossil Fuels > Systems and Infrastructure
3.
Hannele Holttinen Peter Meibom Antje Orths Bernhard Lange Mark O'Malley John Olav Tande Ana Estanqueiro Emilio Gomez Lennart Söder Goran Strbac J Charles Smith Frans van Hulle 《风能》2011,14(2):179-192
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. 相似文献
4.
J. Charles Smith Dale Osborn Robert Zavadil Warren Lasher Emilio Gmez‐Lzaro Ana Estanqueiro Thomas Trotscher John Tande Magnus Korps Frans Van Hulle Hannele Holttinen Antje Orths Daniel Burke Mark O'Malley Jan Dobschinski Barry Rawn Madeline Gibescu Lewis Dale 《Wiley Interdisciplinary Reviews: Energy and Environment》2013,2(1):1-13
This paper provides an overview of major transmission planning activities related to wind integration studies in the United States and Europe. Transmission planning for energy resources is different from planning for capacity resources. Those differences are explained, and illustrated with examples from several regions of the United States and Europe. Transmission planning for wind is becoming an iterative process consisting of generation expansion planning, economic‐based transmission planning, system reliability analysis, and wind integration studies. A brief look at the policy environment in which this activity is taking place is provided. A set of coherent and collaborative transmission planning, siting, and permitting policies and cost allocation method must be developed to achieve the intended objectives. The scale of transmission development envisioned for this purpose will require unprecedented cooperation across multiple jurisdictional boundaries. This article is categorized under:
- Wind Power > Systems and Infrastructure
- Energy Infrastructure > Systems and Infrastructure
- Energy Systems Economics > Systems and Infrastructure
5.
Hannele Holttinen 《风能》2005,8(2):173-195
Studies of the effects that wind power production imposes on the power system involve assessing the variations of large‐scale wind power production over the whole power system area. Large geographical spreading of wind power will reduce variability, increase predictability and decrease the occasions with near zero or peak output. In this article the patterns and statistical properties of large‐scale wind power production data are studied using the data sets available for the Nordic countries. The existing data from Denmark give the basis against which the data collected from the other Nordic countries are benchmarked. The main goal is to determine the statistical parameters describing the reduction of variability in the time series for the different areas in question. The hourly variations of large‐scale wind power stay 91%–94% of the time within ±5% of installed capacity in one country, and for the whole of the Nordic area 98% of the time. For the Nordic time series studied, the best indicator of reduced variability in the time series was the standard deviation of the hourly variations. According to the Danish data, it is reduced to less than 3% from a single site value of 10% of capacity. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
6.
The growing proportion of wind power in the Nordic power system increases day‐ahead forecasting errors, which have a link to the rising need for balancing power. However, having a large interconnected synchronous power system has its benefits, because it enables to aggregate imbalances from large geographical areas. In this paper, day‐ahead forecast errors from four Nordic countries and the impacts of wind power plant dispersion on forecast errors in areas of different sizes are studied. The forecast accuracy in different regions depends on the amount of the total wind power capacity in the region, how dispersed the capacity is and the forecast model applied. Further, there is a saturation effect involved, after which the reduction in the relative forecast error is not very large anymore. The correlations of day‐ahead forecast errors between areas decline rapidly when the distance increases. All error statistics show a strong decreasing trend up to the area sizes of 50,000 km2. The average mean absolute error (MAE) in different regions is 5.7% of installed capacity. However, MAE of a smaller area can be over 8% of the capacity, but when all the Nordic regions are aggregated together, the capacity‐normalized MAE decreases to 2.5%. The average of the largest errors for different regions is 39.8% and when looking at the largest forecast errors for smaller areas, the largest errors can exceed 80% of the installed capacity, whereas at the Nordic level, the maximum forecast error is only 13.5% of the installed capacity. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
7.
Bri‐Mathias S. Hodge Himanshu Jain Carlo Brancucci Gab‐Su Seo Magnus Korps Juha Kiviluoma Hannele Holttinen James Charles Smith Antje Orths Ana Estanqueiro Lennart Sder Damian Flynn Til Kristian Vrana Rick Wallace Kenyon Benjamin Kroposki 《Wiley Interdisciplinary Reviews: Energy and Environment》2020,9(5)
Rapidly increasing levels of variable inverter‐based renewable energy sources (are quickly changing electric power systems and prompting questions about how the systems will be operated when renewable generation becomes the dominant technologies. In this article, we review the status of this shifting paradigm in power systems throughout the world. We then review the implications of this shift, focusing on the rising challenges, and we provide an overview and technology‐readiness classifications of some proposed mitigation strategies. Finally, we highlight outstanding questions that will require solutions to reach these ultrahigh shares of variable inverter‐based renewable energy sources. This article is categorized under:
- Wind Power > Systems and Infrastructure
- Energy Systems Economics > Systems and Infrastructure
- Energy Infrastructure > Systems and Infrastructure
8.
The use of building information modelling (BIM) and related software tools is increasingly expanding in the work of site managers in construction projects. The early uses of BIM in the actual tasks of site managers are explored by examining the utilization of BIM in their work and the challenges in the deployment of the new digital tools for traditional project collaboration. The ethnographic method of the study consists of shadowing the site managers’ work. The site managers actively used BIM and found it beneficial for their daily work. However, the use of BIM in construction sites is still limited because only a few managers have the competence to use BIM software tools, mobile tools are lacking, and the information content of the models needed for construction work is insufficient. 相似文献
9.
Anna‐Marja Aura Sirpa Karppinen Hannele Virtanen Pirkko Forssell Satu‐Maarit Heinonen Tarja Nurmi Herman Adlercreutz Kaisa Poutanen 《Journal of the science of food and agriculture》2005,85(12):2085-2093
Plant lignans are converted to mammalian forms, enterodiol and enterolactone, in the colon. Enhanced plasma or urinary enterolactone levels have been associated with lowered risk of cardiovascular diseases and breast cancer. Processed rye bran and its fractions were compared to ascertain the fermentation rates of fermentable carbohydrates and the bioconversion of lignans. Rye bran was extruded and treated with a food‐grade xylanase. Part of the xylanase‐treated rye bran was separated into a soluble rye bran extract and an insoluble residue, and a part of the xylanase‐treated rye bran was freeze‐dried without separation. All the samples were digested by pepsin and pancreatin and subsequently fermented with a human faecal inoculum in vitro. The consumption of carbohydrates, the productions of short‐chain fatty acids (SCFA), enterodiol and enterolactone were followed as a function of time. The soluble rye bran extract showed the fastest fermentation rate and the highest extent of fermentation determined as the consumption of neutral sugar residues (arabinose, xylose and glucose), the production of SCFA and the formation of enterodiol and enterolactone. Xylanase treatment enhanced the fermentation rate of extruded rye bran. An even a higher fermentation rate was observed for rye bran extract containing soluble carbohydrates. The amount of enterolactone precursors in rye seemed to be too low for enterolactone formation using an amount of substrate suitable for carbohydrate fermentation. However, xylanase treatment enhanced the availability of plant lignans from rye bran, as enterodiol formation was increased by the use of xylanase. Copyright © 2005 Society of Chemical Industry 相似文献
10.
Jaana M. Kusnetsov Pertti J. Martikainen Hannele R. Jousimies-Somer Marja-Liisa Visnen Arto I. Tulkki Henry E. Ahonen Aino I. Nevalainen 《Water research》1993,27(1)
The occurrence of Legionella in water of 30 cooling tower systems was studied, as well as the relationship of its occurrence with the physical, chemical and microbiological characteristics of the waters. The samples were concentrated by membrane filtration and one part of the concentrate was acid washed. Three types of culture media, MWY, CCVC and BCYEα were used. Fourteen (47%) of the cooling systems were Legionella-positive. Numbers of Legionella in the positive systems varied between 50 and 490,000 cfu/l. Legionella pneumophila was the dominant isolate, and the serogroups 6 and 1 were the commonest ones. There was no statistically significant difference in mean water temperature between the Legionella-positive (27°C) and -negative (24°C) systems. The total number of bacteria (AODC) was lower in the Legionella-positive than in the negative systems. Also the nutrient concentrations were generally lower in the Legionella-positive cooling systems. The results suggest that different factors regulate the occurrence of Legionella than that of overall bacterial populations in the cooling tower systems. 相似文献