Selection of the wind turbine manufacturer is naturally an important issue for wind energy companies when they build new wind farms. This paper describes the main factors by which wind energy companies choose their tu...Selection of the wind turbine manufacturer is naturally an important issue for wind energy companies when they build new wind farms. This paper describes the main factors by which wind energy companies choose their turbine manufacturers in a selected case region in Finland. The study was conducted using semi-structured interviews, for which the experts and decision makers of selected wind energy companies formed the focus group. During the analysis of the results, it became clear that it was not possible to form a detailed and prioritized list of selection criteria, but still some general themes emerged. The main theme was the manufacturer and product reliability, and then the production volume, cost factors, availability factors, and the organization of maintenance in this order. Interestingly, the arctic conditions of the selected case region did not play any significant role.展开更多
We present a novel, low-cost approach to fabricate flexible piezoelectric nano- generators （NGs） consisting of ZnO nanowires （NWs） on carbon fibers and foldable Au-coated ZnO NWs on paper. By using such designed s...We present a novel, low-cost approach to fabricate flexible piezoelectric nano- generators （NGs） consisting of ZnO nanowires （NWs） on carbon fibers and foldable Au-coated ZnO NWs on paper. By using such designed structure of the NGs, the radial ZnO NWs on a cylindrical fiber can be utilized fully and the electrical output of the NG is improved. The electrical output behavior of the NGs can be optionally controlled by increasing the fiber number, adjusting the strain rate and connection modes. For the single-fiber based NGs, the output voltage is 17 mV and the current density is about 0.09 μA·cm^-2, and the electrical output is enhanced greatly compared to that of previous similar micro-fiber based NGs. Compared with the single-fiber based NGs, the output current of the multi-fiber based NGs made of 200 carbon fibers increased 100-fold. An output voltage of 18 mV and current of 35 nA are generated from the multi-fiber based NGs. The electrical energy generated by the NGs is enough to power a practical device. The developed novel NGs can be used for smart textile structures, wearable and self-powered nanodevices.展开更多
For a variable speed large scale wind turbine, the vibration issues become a key problem that cannot be ignored in the turbine＇s life cycle. Wind turbine tower vibration will cause superfluous mechanical loads. To re...For a variable speed large scale wind turbine, the vibration issues become a key problem that cannot be ignored in the turbine＇s life cycle. Wind turbine tower vibration will cause superfluous mechanical loads. To resolve the vibration issue, a method for constructng the energy function V is proposed to meet the demands of safe operation. The Lyapunov theorem has been em- bedded in a wind turbine control algorithm, proving the theoretical feasibility of stability control based on function V. Accord- ing to an analysis of this complex nonlinear model for the wind turbine, the general method of constructing an energy function suitable for a wind turbine is presented explicitly. The feasibility of applying an energy function to wind turbine vibration con- trol is verified experimentally using a 3.0-MW direct drive wind turbine model. The experimental results indicate that the dy- namic performance of the tested wind turbine model with energy function control is significantly better than that of the uncon- trolled structure in terms of the reduction of nacelle acceleration, velocity, and displacement response.展开更多
文摘Selection of the wind turbine manufacturer is naturally an important issue for wind energy companies when they build new wind farms. This paper describes the main factors by which wind energy companies choose their turbine manufacturers in a selected case region in Finland. The study was conducted using semi-structured interviews, for which the experts and decision makers of selected wind energy companies formed the focus group. During the analysis of the results, it became clear that it was not possible to form a detailed and prioritized list of selection criteria, but still some general themes emerged. The main theme was the manufacturer and product reliability, and then the production volume, cost factors, availability factors, and the organization of maintenance in this order. Interestingly, the arctic conditions of the selected case region did not play any significant role.
基金AcknowledgementsThis work was supported by the National Major Research Program of China （No. 2013CB932602）,the Major Project of International Cooperation and Exchanges （No. 2012DFA50990）, the National Natural Science Foundation of China （NSFC） （Nos. 51172022, 51232001, and 51372020）, the Fundamental Research Funds for Central Universities, the Program for New Century Excellent Talents in University, Beijing Higher Education Young Elite Teacher Project, the Programme of Introducing Talents of Discipline to Universities, and Program for Changjiang Scholars and Innovative Research Teams in University.
文摘We present a novel, low-cost approach to fabricate flexible piezoelectric nano- generators （NGs） consisting of ZnO nanowires （NWs） on carbon fibers and foldable Au-coated ZnO NWs on paper. By using such designed structure of the NGs, the radial ZnO NWs on a cylindrical fiber can be utilized fully and the electrical output of the NG is improved. The electrical output behavior of the NGs can be optionally controlled by increasing the fiber number, adjusting the strain rate and connection modes. For the single-fiber based NGs, the output voltage is 17 mV and the current density is about 0.09 μA·cm^-2, and the electrical output is enhanced greatly compared to that of previous similar micro-fiber based NGs. Compared with the single-fiber based NGs, the output current of the multi-fiber based NGs made of 200 carbon fibers increased 100-fold. An output voltage of 18 mV and current of 35 nA are generated from the multi-fiber based NGs. The electrical energy generated by the NGs is enough to power a practical device. The developed novel NGs can be used for smart textile structures, wearable and self-powered nanodevices.
文摘For a variable speed large scale wind turbine, the vibration issues become a key problem that cannot be ignored in the turbine＇s life cycle. Wind turbine tower vibration will cause superfluous mechanical loads. To resolve the vibration issue, a method for constructng the energy function V is proposed to meet the demands of safe operation. The Lyapunov theorem has been em- bedded in a wind turbine control algorithm, proving the theoretical feasibility of stability control based on function V. Accord- ing to an analysis of this complex nonlinear model for the wind turbine, the general method of constructing an energy function suitable for a wind turbine is presented explicitly. The feasibility of applying an energy function to wind turbine vibration con- trol is verified experimentally using a 3.0-MW direct drive wind turbine model. The experimental results indicate that the dy- namic performance of the tested wind turbine model with energy function control is significantly better than that of the uncon- trolled structure in terms of the reduction of nacelle acceleration, velocity, and displacement response.
