| 1. |
- Ackermann, Kathrin, et al.
(författare)
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N-2 Fixation in Feather Mosses is a Sensitive Indicator of N Deposition in Boreal Forests
- 2012
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Ingår i: Ecosystems. - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 15:6, s. 986-998
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen (N) fixation in the feather moss-cyanobacteria association represents a major N source in boreal forests which experience low levels of N deposition; however, little is known about the effects of anthropogenic N inputs on the rate of fixation of atmospheric N-2 in mosses and the succeeding effects on soil nutrient concentrations and microbial community composition. We collected soil samples and moss shoots of Pleurozium schreberi at six distances along busy and remote roads in northern Sweden to assess the influence of road-derived N inputs on N-2 fixation in moss, soil nutrient concentrations and microbial communities. Soil nutrients were similar between busy and remote roads; N-2 fixation was higher in mosses along the remote roads than along the busy roads and increased with increasing distance from busy roads up to rates of N-2 fixation similar to remote roads. Throughfall N was higher in sites adjacent to the busy roads but showed no distance effect. Soil microbial phospholipid fatty acid (PLFA) composition exhibited a weak pattern regarding road type. Concentrations of bacterial and total PLFAs decreased with increasing distance from busy roads, whereas fungal PLFAs showed no distance effect. Our results show that N-2 fixation in feather mosses is highly affected by N deposition, here derived from roads in northern Sweden. Moreover, as other measured factors showed only weak differences between the road types, atmospheric N-2 fixation in feather mosses represents a highly sensitive indicator for increased N loads to natural systems.
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| 2. |
- Ackermann, Thomas
(författare)
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Historical Development and Current Status of Wind Power
- 2012
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Ingår i: Wind Power in Power Systems, Second Edition. - : John Wiley & Sons. - 9780470974162 ; , s. 21-24
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Bokkapitel (refereegranskat)abstract
- The chapter provides an overview of the historical development (mechanical and electrical power generation) of wind power. It also present the current status of wind power world-wide (capacity installed) together with a discussion of the main drivers for the wind power development, e.g. feed-in tariffs, green certificates etc. Furthermore, the chapter briefly discuss the current trends in wind turbine technology, e.g. larger turbines, and projects development, e.g. offshore wind power.
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| 3. |
- Ackermann, Thomas
(författare)
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Introduction
- 2012
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Ingår i: Wind Power in Power Systems, Second Edition. - : Wiley. ; , s. 1-5
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Bokkapitel (refereegranskat)
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| 4. |
- Ackermann, Thomas, et al.
(författare)
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New Control Concept for Offshore Wind Power Plants : Constant-Speed Turbines on a Grid with Variable Frequency
- 2012. - 2
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Ingår i: Wind Power in Power Systems. - : John Wiley & Sons. - 9780470974162 ; , s. 345-359
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Bokkapitel (refereegranskat)abstract
- By using a permanent magnet induction machine as wind generator, the gearbox and converter can be omitted, and the total number of parts reduced leading to a low maintenance and reliable turbine for offshore application. The rotation speed of the turbine however cannot be matched to the wind speed, reducing the energy yield at part load. To overcome this drawback, a central converter can be used, which adjusts the frequency of the local grid in the wind park; this is the so-called park-variable concept. This concept has been compared with respect to energy yield with constant speed and variable speed turbines. Overall, the differences in energy yield of the investigated concepts are so small that other criteria, such as reliability or cost, may be relevant for the selection of one or the other approach. Above all, the park-variable concept represents an interesting alternative to today's common concepts.
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| 5. |
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| 6. |
- Ackermann, Thomas, et al.
(författare)
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The Value of Wind Power
- 2012. - 2
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Ingår i: Wind Power in Power Systems. - : John Wiley & Sons. - 9780470974162 ; , s. 131-155
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Bokkapitel (refereegranskat)abstract
- The aim of the power plants in a power system is to supply the load in an economical, reliable and environmentally acceptable way. Different power plants can fulfil these requirements in different ways. In order to select the right sources it is important to compare the value of the different sources using an objective approach. The aim of this chapter is describe the different needs of a power system and how these needs can be met with wind power, that is, the value of wind power in a certain system. The values are operating cost value, capacity value, control value, grid loss reduction value and grid investment value. The values can be calculated for different types of power plants, they can be both positive and negative, and they can be calculated both as a physical cost value and a market value.
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| 7. |
- Ackermann, Thomas, et al.
(författare)
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Transmission Systems for Offshore Wind Power Plants and Operation Planning Strategies for Offshore Power Systems
- 2012. - 2
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Ingår i: Wind Power in Power Systems. - : John Wiley & Sons. - 9780470974162 ; , s. 293-327
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Bokkapitel (refereegranskat)abstract
- The electric system within an offshore wind power plant and its connection to the main power system pose new challenges to the experts. The best way of interconnecting the wind turbines inside a wind farm has to be found, fulfilling both, redundancy requirements without compromising economic feasibility. The best choice between technologies (HVAC, HVDC - VSC or LCC) for connecting windfarms to shore has to be made, depending on several criteria. The risk of losing this connection versus redundancy has to be economically evaluated. By combining interconnectors and offshore windfarm connections in a modular way, a DC offshore grid can be developed. Anyhow, already during the planning phase the secure operation should be considered thoroughly, because the optimal architecture has to be found, minimizing the necessary assets ensuring secure operation and facilitating later expansion options. The interaction with the onshore grid has to be investigated as well. To enable investigations covering these issues a benchmark offshore test system has been developed which is described in this chapter.
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| 8. |
- Matevosyan, J., et al.
(författare)
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Technical Regulations for the Interconnection of Wind Power Plants to the Power System
- 2012. - 2
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Ingår i: Wind Power in Power Systems. - : John Wiley & Sons. - 9780470974162 ; , s. 209-240
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Bokkapitel (refereegranskat)abstract
- This chapter provides a brief discussion and analysis of the current status of interconnection regulations for wind turbines and wind turbines in Europe. The chapter starts with a short overview of the relevant technical regulation issues, which includes a brief description of the relevant interconnection regulations considered in this chapter. This is followed by a detailed comparison of the different interconnection regulations. The discussion also includes the capabilities of wind turbines to comply with these requirements. Finally, issues related to international interconnection practice are briefly discussed.
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| 9. |
- Morthorst, P. E., et al.
(författare)
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Economic Aspects of Wind Power in Power Systems
- 2012. - 2
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Ingår i: Wind Power in Power Systems, Second Edition. - : John Wiley & Sons. - 9780470974162 ; , s. 489-516
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Bokkapitel (refereegranskat)abstract
- The integration of large amounts of wind power into the energy system requires a strong interplay with power markets. In this respect the power exchange is an important instrument, defining a single market clearing price for each trading period. Following the liberalisation of the EU electricity industry power markets are increasingly being organised as power exchanges to a certain extent following the same lines, where a number of if not identical then closely related services are being provided. Using the NordPool power market as an example this chapter outlines the basic characteristics of the two key markets, the day-ahead market and the regulating market. The determination of the day-ahead price is described and the impact of wind power on power prices investigated. Finally, the cost of regulation is addressed.
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| 10. |
- Slootweg, J. G., et al.
(författare)
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Wind Power and the Smart Grid
- 2012. - 2
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Ingår i: Wind Power in Power Systems. - : John Wiley & Sons. - 9780470974162 ; , s. 951-973
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Bokkapitel (refereegranskat)abstract
- It is justified to ask why something potentially offering such benefits as Smart Grids seem to do, is not yet in place. As will be discussed in this chapter, this is due to the fact that many conditions must be fulfilled in order to really reap benefits of Smart Grids; if this is indeed the case, benefits can indeed be substantial. In order to get grip on the broad concept of Smart Grids and its interaction with wind power and its system integration, first some definitions of the Smart Grid concept will be analyzed. Thereafter, the reasons for considering Smart Grids are discussed and the question why Smart Grids presently attract so much attention whereas throughout the last century the topic was hardly known, is debated. In the next section, three different Smart Grid concepts are treated and the analysis of each of the three concepts is focused towards their relation with wind power. Finally, practical examples are discussed.
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