An overview of wind energy 3/5/2018

World-wide electricity production 79% Dominant source after hydro Source: obser’ER

Global installed capacity of wind power Source: GWEC Capacity in 2017 Cumulative : 539 GW Can cover more than 5% electricity demand Newly added More than half from outside EU and US From China, India, Brazil, …

Wind energy by country Cumulative wind capacity in 2017 World’s top : 35% from China Share in whole EU : 33% 188 GW 89 GW 178096/539581 China overtook US in 2010 penetration = the percentage of demand covered by wind energy in a certain region Total amount of wind energy produced (annually) / Gross annual electricity demand Source: GWEC Domestic electricity generated by wind Percentage of power produced to total in a country World’s top : 42% in Denmark (2015)

Growth of power and size Cited from Blaabjerg, F., & Ma, K. “Future on power electronics for wind turbine systems” (2013) Future on Power Electronics for Wind Turbine Systems Average : 2-3 MW (2016) Products developed now : 4.5-8 MW Largest capacity : 8 MW with 164 m diameter 1 × 1 GW nuclear reactor = 500 × 2 MW wind turbines

Structure Source: US Department of Energy

Offshore wind High wind speed Large energy production Stable conditions of wind Reliable source Expensive and difficult to build and maintain Damage from wave and heavy storms Onshore Shallow ~30 m Deep 50 m ~ Offshore http://www.siemens.co.uk/en/news_press/index/news_archive/2013/london-array-worlds-largest-offshore-wind-farm-inaugurated.htm Source : SIEMENS Source : NREL First wind turbine : 220 kW, in Sweden (1991) Largest offshore wind farm : London Array 630 MW, 175 turbines

Vertical axis wind turbine Omni-directional (no need of yaw mechanisms) Less complexity of structure Generator positioned close to ground Darrieus type Savonius type http://www.green-mechanic.com/2013/04/advantages-and-disadvantages-of.html http://www.renugen.co.uk/windside-ws-4b-12v-420w-wind-turbine/ Source : Creative Commons (left), renugen (right)

Energy conversion 𝝆×𝑨×𝑽 Rotation Wind (mechanical energy) (kinetic energy) Rotation (mechanical energy) Electricity Power of wind = 𝟏 𝟐 × 𝒎 × 𝑽 𝟐 𝟏 𝟐 ×𝝆𝑨× 𝑽 𝟑 Density of air 𝝆×𝑨×𝑽 Proportional to Swept area Cube of wind speed Wind speed 𝑽 Double wind speed Power increased by 8 times Area 𝑨

Efficiency Power coefficient Ratio of extracted power to wind energy Determined by design of wind turbine Theory : 59% (maximum) Actual : 45 to 50% for modern large wind turbines Electric energy Energy from wind Conversion of energy 100 % 30-40 % Aerodynamic loss 50-60 % (at blade and rotor) p660 https://www.worldenergy.org/wp-content/uploads/2016/10/World-Energy-Resources-Full-report-2016.10.03.pdf Mechanical loss 4 % (at gear) Electrical loss 6 % (at generator)

Capacity factor Ratio of actual output to rated power Affected by weather variations, downtime, etc… Source: Swedish Energy Agency, Vindkraftsstatistik 2013 Power production during a week in Feb. 20-40 % for most wind turbines 45-60% on very good wind sites

Research at Division Focus on vertical axis wind turbine Company Vertical Wind AB Developed by Univeristy H-rotor type Located in Falkenberg and Marsta Research interest in Generator design Power modeling Aerodynamics … so on Falkenberg Three 24m-long blades, 40m height Marsta 6m height Vertical axis wind turbine in Falkenberg

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