Urban Wind Power

Why? Locations, where is no space for large turbines Energy savings o Preventing energy transporting losses from larger power plants Individual energy producers o More awareness of energy effiency o Less depency on energy companies Savings of fossil fuel recources and CO 2 Could be a part of high level renewable energy policy Energy payback

Wind condition in urban areas A lot of obstacles, such as buildings and street furniture o Wind speed accelerates when getting round obstacles Turbulent flow Challenges due to rapidly changing wind direction and speed o Extra stresses on turbine o Problems for turbine design Difficult to find suitable places for turbines

Suitable locations for turbines Less turbulent areas: o Building roofs o Open areas on the ground Industrial area Rural areas The annual wind speed should be at least 5.5 m/s The roof should be ~50% taller than surroundings Turbines positioned near the centre of the roof

Several turbines should be placed at the same location if possible The lowest position of the rotor should be higher than 30% of the building height The influence of wind rose must be taken into consideration Expected energy yield 200 – 400 kW/m 2 /year

Problems in urban areas The most remarkable drawback is noise o Aerodynamic noise o Mechanical noise Mechanical noise can be reduced by careful design and insulation of turbine head Only a little difference in noise level between turbine types o 87% of turbines offer noise less than 60 dB with a wind speed of 5 m/s Social effects could be a problem o Building owners, neighbours etc. Vibrations and flickering

Urban turbines Small turbines o Rotor diameter 0,75 – 25m (IEC definition) The rated power of turbines is 0,1 – 50 kW o Mainly < 30 kW On grid voltage 230 Volts o Possibility to sell electricity Off grid voltage 12/24/48 Volts o Used in remote areas Lifetime is typically years The investment costs are high

Learning curve (case in the UK)

Turbine concepts Basic division: Horizontal axis wind turbine (HAWT) Vertical axis wind turbine (VAWT)  Divided further in drag- and lift-based turbines All concepts have their own characteristic advantages and disadvantages, the best turbine is site-dependent

Horizontal axis turbines The most succesful commercial turbine type at the moment Superior concept in industrial scale In smaller scale & urban environment major drawbacks become more visible The most common model is a three bladed so called Danish type rotor

Vertical axis turbine Two common types Savonius Darrieus Not feasible in industrial scale due to lower efficiency compared to HAWTs In urban environment some advantages over HAWTs

Savonius rotor The most used drag- type rotor concept Scoops see less drag going against wind than with wind Very reliable, low need for maintenance Low efficiency, maximum C p =0,18 Very silent

Darrieus rotor Lift-based consept Reliability is a problem, especially blades have been sensiteve for vibrations Theoretically same efficiency as HAWTs, best achieved C p =0,38

Comparison between different turbine concepts

Projects Oklahoma Medical Research Foundation in Oklahoma City, U.S. 18 Savonius type turbines with height of 5,6 m, rated 4,5 kW each The largest building integrated wind power system in the world

Projects Civic center 3 in Huddersfield, UK 2x6 kW HAWTs integrated with PV cells and solar panels

Projects Strand wind project in Townsville, Australia Educational and tourism project Single 6 kW twin rotor darrieus turbine

Performance of urban turbines

Thank You! Any Questions?