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RENEWABLE ENERGY OPPORTUNITIES FOR A CITY: WIND ENERGY

image credit: Images from New World Wind, Inhabitat, smartcitiesdive
Niyireth Torres's picture
urban Planner Renewable energy enthusiast

I help cities, towns, and communities achieve sustainable practices by providing strategic planning using my knowledge of green building practices, renewable energy, architecture, and the retail...

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  • Jul 29, 2021
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You mostly picture a wind farm in rural areas or at sea when you think of wind power. But with new advances in technology, there is a possibility to increase the presence of wind power in cities with a vertical axis wind turbine.

 

A vertical axis wind turbine (VAWT) is a type of wind turbine where the main rotor shaft is set transverse to the wind. The main components are located at the base of the turbine being close to the ground, facilitating the generator and gearbox service and repair. It does not need to be pointed into the wind, removing the need for wind sensing and orientation mechanisms. They are 15% more efficient than the conventional horizontal axis wind turbines as they generate less turbulence. 

 

The more popular horizontal axis turbine is not suitable for the urban environment. It produces more energy efficiently but requires more space to be built on-site and higher wind speed averages to move. They are nosier and esthetically are not pleasing since they resemble propellers.

 

Uses

 

Wind power or wind energy is a renewable energy that uses wind to provide mechanical power through wind turbines to turn electric generators for electrical power. It is a popular sustainable renewable energy source for its small environmental impact, its support to a domestic supply chain, its affordability, the ability to reduce air pollution emissions, the preservation of water resources, and the increase of community revenues.

 

The U.S Department of Energy (DOE’s) Wind Energy Technologies Office and a team of researchers, academics, scientists, engineers, and wind industry experts collaborated on the Wind Vision Report to conceptualize a new vision for wind energy through 2050. It envisions the future of wind, where it supplies 35% of the U.S. national electrical demand.  

 

Examples of wind power in urban environments: 

 

  • The French company New World Wind has developed tree-shaped turbines called Wind Tree, meant to be installed to run silently within cities at a ground level. Created to be built off-site, aesthetically pleasing, take less space, and not generate much noise. It is 36 feet (11 meters) tall and around 26 feet (8 meters) in diameter and has 72 artificial leaves. Each leaf is a small turbine that rotates vertically. A single tree can generate 3.1 kW of power and is expected to spin 280 days out of the year.   

 

 

  • Venger Wind and U.S. renewable distributor SWG Energy installed 18 Omnidirectional wind turbines on the top of the Oklahoma Medical Research Foundation (OMRF) in Oklahoma City. The wind turbines are integrated into the design of the building, positioned to receive wind North and Southside of the rooftop. It is the world’s largest rooftop wind farm, constructed as a part of OMRF’s sustainability strategy for a zero-emissions research tower.

 

 

  • The Greenway Self Park project from HOK in Chicago is an example of building-integrated wind turbines. It marries wind energy with architecture to generate enough power to cover the cost of lighting the building exterior at night. The dozen vertical axis wind turbines are staked in two double-helical columns along the southeast corner to use the breezes coming from any direction and the different speeds.  

 

 

Opportunities 

 

Wind power is a renewable energy that has great potential in urban areas. Wind speed patterns in cities are different than in nature or in rural areas. Buildings affect the wind in urban locations with sharp corners and rectangular shapes causing localized wind accelerations, called wind tunnels, accelerating wind speeds as the air squeezes through buildings. It can cause pedestrians to trip or have objects flying at high velocity. Especially inroads with tall buildings, it can cause a downdraught effect where the wind is deflected downward.

 

The grouping of tall buildings and skyscrapers can create “street canyons” or “urban canyons” that affect local conditions, such as temperature, wind, light, and air quality. The vertical axis turbines can exploit this phenomenon. Winds from any direction at multiple velocities and the inconsistent breezes of the urban microenvironment can be harnessed and turned into energy.

 

For this to happen, wind harnessing technology has to be integrated with the design of:

 

  • Rooftops: Wind harvesting can be done on rooftops, whether it was integrated into the architectural design, such as the Oklahoma Medical Research Foundation rooftop wind farm, or it can be installed as an afterthought. Rooftops are underutilized real estate in an urban area. The use of wind harvesting technology to reduce electricity costs for a building is a better option than solar energy since smaller buildings wouldn’t get as much exposure as taller ones. They are installed at higher levels and can harness higher wind speeds. 
  • Facades: As mentioned before, cities with tall buildings have the phenomenon of wind tunnels at ground levels, where wind harvesting facades are a better solution for harnessing wind than vertical wind turbines. Using wind harvesting in facades creates cheaper, esthetically pleasing, and more efficient energy systems. An example of this is Murtada Alkaabi's design, which uses unique façade elements made from recyclable plastic to allow free movement and more compression that creates pressure or force converted to an electric charge called piezoelectricity. The principle of piezoelectricity consists of electricity resulting from pressure and latent heat in certain solid materials, such as crystals and certain ceramics. All the generated wind energy will go through a connector between the inverter and mains to the power grid, creating a loop between user and supplier. The excess energy is stored in batteries that can be used on a non-windy day.  

 

  • Parks: Parks are the social areas of the city that often have public art displayed. Why not have it be functional as well? The Wind Tree and the Flower Turbine would be perfect installations for public spaces and parks. They contribute to the city by providing intelligent lighting, aiding mobility, and reuniting inhabitants with the source of their electricity. The Wind Tree, the tree-shaped sculpture with leaf-shaped wind turbines, contributes to the experience of living in a city that can remember, correlate, and anticipate, contributing to the rise of the conscious city. The Flower Turbine is a small tulip-shaped turbine that produces no noise. Birds can see and not run into them and, when grouped, can perform 20-50%. These turbines can be considered eco-kinetic art. It is a moving art piece that brings to light the local and global environmental situations of the need for renewable energy vs. fossil fuels, showcasing that it can be beautiful, noninvasive, local, and coexist with our current way of living.

 

Unlike conventional horizontal axis wind turbine technology, which has been perfected for over a hundred years, vertical axis wind turbine and façade wind harvesting are relatively new. In VAMT, they are fatigue prone due to the wide variation of winds during each rotation, and the blades twist and bend during each turn, shortening their lifetime. At the same time, façade harvesting is in the initial stages of recognition as a viable technology. In both cases, there needs to be more innovation to perfect the existing technology. There is an interest, especially in the energy community, to implement more wind energy. Still, urban areas need to be considered in the expansion of wind harvesting since they are an untapped market.  

 

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