No abstract

Increasing maintenance costs will hinder the expansion of the wind power industry in the coming decades. Training personnel, field maintenance, and frequent boat or helicopter visits to wind turbines (WTs) is becoming a large cost. One reason for this cost is the routine turbine inspection repair and other stochastic maintenance necessitated by increasingly unbalanced figure loads and unequal turbine fatigue distribution in large-scale offshore wind farms (OWFs). In order to solve the problems of unbalanced fatigue loads and unequal turbine fatigue distribution, thereby cutting the maintenance cost, this study analyzes the disadvantages of conventional turbine fatigue definitions. We propose an improved fatigue definition that simultaneously considers the mean wind speed, wind wake turbulence, and electric power generation. Further, based on timed automata theory, a power dispatch approach is proposed to balance the fatigue loads on turbines in a wind farm. A control topology is constructed to describe the logical states of the wind farm main controller (WFMC) in an offshore wind farm. With this novel power control approach, the WFMC can re-dispatch the reference power to the wind turbines according to their cumulative fatigue value and the real wind conditions around the individual turbines in every power dispatch time interval. A workflow is also designed for the control approach implementation. Finally, to validate this proposed approach, wind data from the Horns Rev offshore wind farm in Denmark are used for a numerical simulation. All the simulation results with 3D and 2D figures illustrate that this approach is feasible to balance the loads on an offshore wind farm. Some significant implications are that this novel approach can cut the maintenance cost and also prolong the service life of OWFs.

With the rapidly booming economy, China has been suffering from serious particulate matter (PM) pollution in recent years. In order to improve the air quality, Chinese government issued a new China National Ambient Air Quality Standard (No. GB3095-2012) in 2012. In this study, PM exposure level was simulated based on the data of 912 newly constructed monitoring sites and Voronoi Neighborhood Averaging (VNA) interpolation method. It is widely accepted that PM can cause short-term health effects. We calculated the short-term health benefit due to decreasing PM concentration to the levels of China National Ambient Air Quality Standard based on Environmental Benefits Mapping and Analysis Program (BenMAP). Our results indicated that if the daily average concentration of PM reduced to the daily Grade II standard (150 μg/m), the avoided deaths for all cause, cardiovascular disease, and respiratory disease would be 82,000 (95%CI: 49,000-120,000), 56,000 (95%CI: 34,000-78,000), and 16,000 (95%CI: 10,000-22,000) in 2014, respectively. The economic benefits of avoiding deaths due to all cause for rolling back the concentration of PM to the level of 50 μg/m were estimated to be 240 billion CNY and 16 billion CNY using willingness to pay (WTP) and human capital (HC) methods, respectively, which accounted for 0.38% (95%CI: 0.11-0.64%) and 0.03% (95%CI: 0.02-0.03%) of the total annual gross domestic product (GDP) of China in 2014.

No abstract

In the high-density crowd flow places in public buildings, typical mobile obstacles, such as trolley cases, mobile sweeping trolleys, shuttle trolleys, police patrol cars, etc., carried by passengers bring convenience for passengers to travel, and can also act as typical obstacles that hinder the flow of people. It is easy to block the flow of people, cause the crowd to become unstable, and cause overcrowding and even stampede accidents. To study the influence of moving obstacles on crowd stability, this paper analyzes the spatial and moving characteristics of typical moving obstacles and constructs a motion model of moving obstacles. Furthermore, based on smooth particle hydrodynamics (SPH), a coupled macroscopic pedestrian flow model including moving obstacles and pedestrian flow is proposed. In order to verify the effectiveness of this proposed coupled motion model, this study takes trolley luggage as an example to design and implement a moving obstacle experiment in pedestrian flow, exploring the impact of moving obstacles to the pedestrian flow, further to study the stability of pedestrian flow.