GwindPP

Offshore Wind Turbine Foundations: Monopile, Jacket, and Tripod The main drivers of offshore wind power development are onshore site limitations and global targets to expand renewable energy capacity. Thus, there is a high potential for offshore wind power development.   Monopile, jacket, and tripod offshore wind turbine foundations:

Wind Power and Power System Balancing A power system load and generation must be equal or within the allowed deviation for security reasons. Power systems operate either at 50Hz or 60Hz frequency.    The violation of the balance between power consumption/load and production/generation in a power system will alter the frequency and threaten the stability of the power system ( Basit et al. 2012).   European Transmission System Operators must maintain a real-time balance between generated and consumed electrical energy (Mott MacDonald 2013). Balancing responsibility for a power producer is to match the output of forecasted electricity in real-time (The European Wind Energy Association 2015).   Wind power generation is variable and production forecasts are not reliable, and the additional reserve capacity needs to meet possible net load changes (Sader 1993). There are two types of reserve services: spinning reserve and supplementary reserve. The...

Wind Power and Voltage Control The voltage level in a power system must be either constant or within a very narrow range as equipment of power system utilities and households are designed to operate at a specific voltage level ( Sourkounis & Tourou 2013).   In transmission lines, a mismatch in reactive power demand and supply will alter a voltage level ( Basit et al. 2012).   Wind farms can support the voltage level by injecting or absorbing reactive power (by generator and shunt).    Qin et al. (2018) proposed a decision-making algorithm for the Danish automatic voltage control system, which is to minimize the grid losses while maintaining voltage magnitude at an acceptable level. The result shows the reduction of power losses by the participation of wind farms in the automatic voltage control system (Qin et al. 2018).  

Grid Code Requirements for Wind Farms The capacity of wind power generation tends to grow globally.   Grid operators for safety and reliability reasons have new requirements as wind power capacity tends to increase.   The main requirements of grid codes for wind power generation are the following ( Basit et al., 2012):   1. Frequency/active power control Active power control is the ability to regulate the power output of a wind turbine ( Sourkounis & Tourou 2013).   2. Voltage/reactive power control Grid codes require that wind farms support the voltage level by injecting or absorbing reactive power ( Sourkounis & Tourou 2013).   3. Low voltage ride through. One of the main requirements of grid codes for wind power is a low voltage ride through, which simply means that wind farms must stay connected to the grid during a fault ( Basit et al., 2012).  

The Positive Environmental Externalities of Wind Farms Wind power generation may reduce greenhouse gas emissions by replacing conventional fossil-fuel-based power plants.   Conventional power plants emit greenhouse gases from fuel burning. The amount of carbon dioxide emissions depends on the quantity of fuel burnt and the amount of carbon in the fuel (Denny & O’Malley 2006).   The quantity of carbon dioxide savings due to wind power generation varies case by case depending on power system characteristics.   Other environmental benefits of wind power include avoiding damage to crops and forests by local air pollution. Also, avoiding water pollution from conventional power plants (World Bank 2015).  

 The Negative Environmental Externalities of Wind Farms The negative impact of wind farms on an ecosystem, landscape, and biodiversity are externalities. The more common negative externalities of wind power projects are visual and noise effects and the impact on birds.   Brennan & Van Rensburg (2016) estimated a willingness to accept the negative impacts of wind farms in Ireland. Most survey respondents showed a willingness to accept the negative externalities of wind farms for some monetary compensation (Brennan & Van Rensburg 2016).   Mattmann et al. (2016) conducted a quantitative non-market valuation meta-analysis of wind power externalities based on a data set of 60 observations drawn from 32 studies. The analysis states the importance of visual effects for wind power acceptance. However, the negative impacts of wind power projects on biodiversity are not significant in welfare measures ( Mattmann et al. 2015).   Bird mortality d...

The Trends of Wind Power Installation Costs  The installation cost of a wind turbine includes a wind turbine purchase, construction work, grid connection, planning, and land use expenses (IRENA 2018). The cost of wind power is forecasted to decline in 2030 compared to 2015 (Williams et al. 2017). Wind turbine design innovations and the variety of wind turbine offers by manufacturers are the current trends that drive wind power cost reductions. The weighted average costs for wind power installations have declined globally by 70 % between 1983 and 2017 from USD 4880/kW to USD 1477/kW (Figure 1).

Wind Turbine Blade Aerodynamics:  Horizontal  Axis Turbines    A rotating turbine blade experiences oncoming wind differently, which is called relative wind. A section of the turbine blade receives a wind velocity differently due to its rotation.   The interaction between oncoming wind and a blade generates lift and drag forces.   Drag force is in the same direction as the relative wind, and it holds the blade back. The lift force is perpendicular to the relative wind (Figure 1).   A maximum lift and minimum drag forces are needed to achieve a higher power coefficient.   Modern Wind turbine blades have an airfoil shape to get an optimal angle of attack and greater lift force (Figure 2).    An angle of attack above certain degrees increases the drag force and causes a stall (Figure 3).   Wind Turbine Blade

Wind Power Extraction by Wind Turbines There is a limit, only a partial extraction of power available in the wind is possible. The amount of extracted wind power in percentages is termed the Power Coefficient (Cp). For example, 25% Cp indicates that only 25% out of 100% available wind power is extracted.    The limit for power extraction from wind is 59.3%, which is Betz's law. A wind turbine extracts wind power by slowing down incoming wind velocity through the rotor blades and letting pass through. The maximum power is extracted when the incoming wind velocity is reduced by one-third at the rotor.   The actual Power Coefficient (Cp) of a wind turbine is below 59.3% due to aerodynamic, generator, and cable losses.   Modern wind turbines operate at a certain Tip Speed Ratio (TSR) to optimize the power output. TSR is the ratio between the velocity of the tip of the blade and the incoming wind speed. The rotor of a wind turbine rotates at a cer...