Can Wind Be Incorporated in Future Buildng Design? Prepared by Elif Kandiyoti

Can wind be incorporated in future building design? How to increase productivity by design? by Elif Kandiyoti

Can wind be incorporated in future building design? How to increase productivity by design? Abstract: All researches show how population and respectively energy demand grow. We have to produce electricity to supply this demand. As we learn from Energy and Environment course’s lectures, we lose 1/3 of energy we generate in transmission line. This indicates that we have to generate electricity as close as possible to where we live. According to the United Nations Environment Program, in 1950 fewer than a third of the people of the world lived in a town or city, while today almost half of the world’s population is urban, and the forecasts are that in just 20 years—by 2030—almost two-thirds of the people will live in cities and towns (Botkin, p 499). In large cities, land is limited and expensive; as a result buildings go vertically instead of horizontally. Thus we will look closely to tall buildings in cities. Moreover, the increasing concerns over environmental issues and the depletion of fossil fuel demanded the search for more sustainable electrical sources. One technology for generating electricity from renewable resources is to use wind turbines that convert the energy contained by the wind into electricity. The wind is a vast, worldwide renewable source of energy. Since ancient times, humans have harnessed the power of the wind (Muyeen, p14). Now we should look at what we can do with today’s technology and knowledge in tall buildings. Before implementing any turbine to anywhere we have to comprehend all aspects of wind energy from macro level to micro level in order to achieve optimum results. Unsuccessful applications of turbines can harm wind’s reputation. Thus we have to make feasibility study as early as possible. In this paper, we will cover all aspects of wind energy from wind flows to building shape, wind energy history, wind flows and its differences in rural and urban areas, wind turbines and their environmental impacts. 2

Wind History: The wind is a free, clean, and inexhaustible energy source. It has served mankind well for many centuries by propelling ships and driving wind turbines to grind grain and pump water. Wind was almost the only source of power for ships until Watt invented the steam engine in the 18th Century. Denmark was the first country to use the wind for generation of electricity. The Danes were using a 23 m diameter wind turbine in 1890 to generate electricity. By 1910, several hundred units with capacities of 5 to 25 kW were in operation in Denmark. About 1925, commercial wind-electric plants using two- and three-bladed propellers appeared on the American market. The most common brands were Wincharger (200 to 1200 W) and Jacobs (1.5 to 3 kW). These were used on farms to charge storage batteries which were then used to operate radios, lights, and small appliances with voltage ratings of 12, 32, or 110 volts. A good selection of 32 Vdc appliances was developed by industry to meet this demand. Then the Rural Electric Administration (REA) was established by Congress in 1936. Low interest loans were provided so the necessary transmission and distribution lines could be constructed to supply farmers with electricity. In the early days of the REA, around 1940, electricity could be supplied to the rural customer at a cost of 3 to 6 cents per kWh. The corresponding cost of wind generated electricity was 12 to 30 cents per kWh when interest, depreciation, and maintenance were included. The lower cost of electricity produced by a central utility plus the greater reliability led to the rapid demise of the home wind electric generator (Johnson, p1-3). What is wind: Wind results from the movement of air due to atmospheric pressure gradients. Wind flows from regions of higher pressure to regions of lower pressure. The larger the atmospheric pressure gradient, the higher the wind speed and thus, the greater the wind power that can be captured from the wind by means of wind energy-converting machinery. The generation and movement of wind are complicated due to a number of factors. Among them, the

3

most important factors are uneven solar heating, the Coriolis effect due to the earth’s selfrotation, and local geographical conditions ( Muyeen, p 4). There are 6 characteristic of wind. Understanding them will help us to optimize wind turbine design, develop wind measuring techniques, and select wind farm sites (Tong, p 12). 1-Wind Speed: Wind speed is one of the most critical characteristics in wind power generation. In fact, wind speed varies in both time and space, determined by many factors such as geographic and weather conditions. Because wind speed is a random parameter, measured wind speed data are usually dealt with using statistical methods (Tong, p 12). 2 Weibull Distribution; The variation in wind speed at a particular site can be best described using the Weibull distribution function which illustrates the probability of different mean wind speeds occurring at the site during a period of time (Tong, p 12). 3- Wind Turbulence: Wind turbulence is the fluctuation in wind speed in short time scales, especially for the horizontal velocity component. Wind turbulence has a strong impact on the power output fluctuation of wind turbine. Heavy turbulence may generate large dynamic fatigue loads acting on the turbine and thus reduce the expected turbine lifetime or result in turbine failure (Tong, p 12). 4- Wind Gust: Wind gust refers to a phenomenon that a wind blasts with a sudden increase in wind speed in a relatively small interval of time. In case of sudden turbulent gusts, wind speed, turbulence, and wind shear may change drastically (Tong, p 12). 5- Wind Direction: Statistical data of wind directions over a long period of time is very important in the site selection of wind farm and the layout of wind turbines in the wind farm. The wind rose

4

diagram is a useful tool of analyzing wind data that are related to wind directions at a particular location over a specific time period (year, season, month, week, etc.) (Tong, p 12). 6- Wind shear: Wind shear is a meteorological phenomenon in which wind increases with the height above the ground. The effect of height on the wind speed is mainly due to roughness on the earth’s surface (Tong, p12). Wind does not flow smoothly over the Earth’s surface. It encounters resistance, known as friction. This is called ground drag. Ground drag is caused by friction when air flows across a surface. Friction is the force that resists movement of one material against another. When wind flows across land or water, friction occurs. This reduces the speed at which air moves over a surface. Ground drag due to friction, however, varies considerably, depending on the roughness of the surface. The rougher or more irregular the surface, the greater the friction. As a result, air flowing across the surface of a lake generates less friction than air flowing over a meadow. Air flowing over a meadow generates less friction than air flowing over a forest. Friction extends to a height of about 1,650 feet (500 meters). However, the greatest effects are closest to Earth’s surface — the first 60 feet over a relatively flat, smooth surface. Over trees, the greatest effects occur within the first 60 feet (18 meters) above the tree line. Friction has a dramatic effect on wind speed at different heights. For instance, a 20-mile-per-hour wind measured at 1,000 feet above land covered with grasses flows at 5 miles per hour 10 feet above the surface. It then increases progressively until it breaks loose from the influence of the ground drag or friction. Ground drag dramatically influences wind speed near the surface of the ground where residential wind generators are located (Chiras, p 24). Because the effects of friction decrease with height above the surface of the Earth, savvy installers typically mount their wind machines on towers 80 to 120 feet high (24 to 37 meters), or 5

even as high as 180 feet (55 meters) in forested regions, so their turbines are out of the most significant ground drag. At these heights, the winds are substantially stronger than near the ground. As discussed shortly, a small increase in wind speed can result in a substantial increase in the amount of power that’s available from the wind and the amount of electricity a wind generator produces. Mounting a wind turbine on a tall tower therefore maximizes the electrical output of the machine. Placing a turbine on a short tower has just the opposite effect (Chiras, p 24). In figures below, we can see friction affects in different regions. Figure1: Friction in meadow,

Figure 2: Friction in forest

Source: Wind Power Basics (p 26)

Figure 3: Friction in urban environment

Another natural phenomenon that affects the output of most wind turbines is turbulence. Turbulence is produced as air flowing across the Earth’s surface encounters objects, such as trees or buildings. They interrupt the wind’s smooth laminar flow, causing it to tumble and swirl, the same way rocks in a stream interrupt the flow of water. Rapid changes in wind speed occur behind large obstacles and winds may even flow in the direction opposite to the wind. This highly disorganized wind flow is referred to as 6

turbulence. Turbulent wind flows wreck havoc on wind machines, especially the less expensive, lighter-weight wind turbines often installed on short towers. Turbulence also causes vibration and unequal forces on the wind turbine, especially the blades that may weaken and damage the machine. Turbulence, therefore, increases wear and tear on wind generators and, over time, can destroy a turbine. When considering a location to mount a wind turbine, be sure to consider turbulence-generating obstacles. Proper location is the key to avoid the damaging effects of turbulence. Turbulence can also be minimized by mounting a wind turbine on a tall tower (Chiras, p 25). After we have enough knowledge on wind, we have to evaluate availability of local wind in our site from macro scale to micro scale. At macro level, the main factor, the annual mean wind speed. In US, there is an 80-meter (m) wind resource map to identify potentially wind sites, provided by The U.S. Department of Energy. In other countries, this can be available at local weather stations. Annual mean wind is equal to the sum of the hourly average values for the whole year divided by 8760 (the number of hours in a year). The mean wind speed will depend on many factors such as the location in relation to dominating global wind currents, the distance from the coast, the amount of upstream ‘roughness’ that the winds have to travel over to reach the site as well as other conditions such as the altitude of the site (Stankovic, p 85). After finding enough information about adequate wind resources in our region, we can determine if our area of interest should be further explored. Wind resource at a micro level can vary significantly; therefore, we should get a professional evaluation of our specific area of interest. Besides professional evaluation, knowing wind flows in urban area can help us design our building suits in its local climate. When our interest is a tall building in urban environment, our focus will be on cities’ climate. 7

Cities affect the local climate; as the city changes, so does its climate. Cities are generally less windy than nonurban areas because buildings and other structures obstruct the flow of air. But city buildings also channel the wind, sometimes creating local wind tunnels with high wind speeds. The flow of wind around one building is influenced by nearby buildings, and the total wind flow through a city is the result of the relationships among all the buildings. Thus, plans for a new building must take into account its location among other buildings as well as its shape (Botkin, p 509). Urban environment affects wind velocity in a few ways. Buildings cast shadows and act as barriers to wind and create channels which increase wind velocity: The bulk of two buildings of differing size adjacent to one another affects wind flows so strongly that the downward flow of air on the taller block creates higher wind speeds in two zones (Thomas, p 25, 116). Figure 4 and 5 at below illustrates how the differing arrangement of simple buildings can disturb the wind flow, generate varying wake patterns and induce swirling turbulent flow. When siting turbine in an urban environment these disturbed flow zones should be identified and avoided. This is commonly achieved by ensuring the blades of the turbine are sufficiently elevated above roof level. Generally, the disturbed flow region in the isolated roughness flow case is considered to be twice the height of the obstacles. Therefore turbine blades, generally, should be located twice the height of the tallest local obstacle to avoid a significant drop in potential performance. There are cases where the acceleration near building can be used to gain an advantage but usually if the building has not been carefully designed with wind energy in mind this should be avoided. The wake region in the isolated roughness case is considered to extend to between 10 and 20 times the obstacle height (Stankovic, p 76).

8

Figure 4: Undisturbed Regions shows wind flow in urban environment and places to avoid installing wind turbine. Source: Urban Wind Energy (p 77)

Figure 5: Optimal turbine heights in undisturbed regions to avoid from turbulent region. Source: Urban Wind Energy (p 77)

9

Wind Turbines: After having knowledge on wind flows, we have to look closely how turbines work. Before we choose a turbine we should know that every turbine is not equal. They give different results in different conditions. Decision should be made according to wind data of our site. A modern wind turbine is an energy-converting machine to convert the kinetic energy of wind into mechanical energy and in turn into electrical energy. Wind turbines can be classified according to the turbine generator configuration, airflow path relatively to the turbine rotor, turbine capacity, the generator-driving pattern, the power supply mode, and the location of turbine installation (Tong, p15). There are two ways to convert wind energy into mechanical power in the rotor axis: dragdriven rotor, a lift-driven rotor or a combination of both concepts: the hybrid rotor. The conversion mechanism of wind power into mechanical power of the lift-driven and drag-driven rotor is different. A lift-driven wind turbine can be a horizontal axis wind turbine (HAWT) or a vertical axis wind turbine (VAWT). The drag-driven wind turbines have a vertical axis. The driving force of the drag-driven rotor originates from the difference in drag of (rotating) bluff bodies. The projected blade area of the drag-driven rotor is approximately equal to the rotor area. The projected blade area of the lift-driven rotor is a fraction of that area (Merten, p 6).

Figure 6: Drag and Lift forces. Sources: CATs

10

Most commercial wind turbines today belong to the horizontal-axis type, in which the rotating axis of blades is parallel to the wind stream. The advantages of this type of wind turbines include the high turbine efficiency, high power density, low cut-in wind speeds, and low cost per unit power output. On the other hand the blades of the vertical-axis wind turbines rotate with respect to their vertical axes that are perpendicular to the ground wind turbine. A significant advantage of VAWT is that the turbine can accept wind from any direction and thus no yaw control is needed. Since the wind generator, gearbox, and other main turbine components can be set up on the ground, it greatly simplifies the wind tower design and construction, and consequently reduces the turbine cost. However, the vertical-axis wind turbines must use an external energy source to rotate the blades during initialization. Because the axis of the wind turbine is supported only on one end at the ground, its maximum practical height is thus limited. Due to the lower wind power efficiency, vertical-axis wind turbines today make up only a small percentage of wind turbines (Tong, p 16). Based on the configuration of the wind rotor with respect to the wind flowing direction, the horizontal-axis wind turbines can be further classified as upwind and downwind wind turbines. The majority of horizontal-axis wind turbines being used today are upwind turbines, in which the wind rotors face the wind. The main advantage of upwind designs is to avoid the distortion of the flow field as the wind passes though the wind tower and nacelle. For a downwind turbine, wind blows first through the nacelle and tower and then the rotor blades. This configuration enables the rotor blades to be made more flexible without considering tower strike. However, because of the influence of the distorted unstable wakes behind the tower and nacelle, the wind power output generated from a downwind turbine fluctuates greatly. In addition, the unstable flow field may result in more aerodynamic losses and introduce more fatigue loads on

11

the turbine. Furthermore, the blades in a downwind wind turbine may produce higher impulsive or thumping noise (Tong, p 17). In a summary, there are 3 turbine types: Vertical Axis Wind Turbine (VAWT), Darrieus (2 Blades, 3 Blades, and H-Rotor), Savonius, and Alternative Designs (Helical, MagLev). Horizontal Axis Win Turbine (HAWT) 1 Blade, 2 Blades, 3 Blades and more, windmill, CoAxial multi rotor. Other types are Aerial/Floating and Wind Belt. Figure 7: Horizontal Axis Wind Turbine and Vertical Axis Wind Turbine. Source: CATs

Figure 8: Horizontal Axis Wind Turbine Components. Source: CATs. Figure 9: Vertical Axis Vind Turbine types. Source: Wind Power Generation and Wind Turbine Design. (p 17)

12

In the built environment, we are looking for the higher buildings to site our wind turbine. Moreover, a wind turbine sited between buildings suffers from turbulence and the resulting frequent changes in wind direction and high fatigue load. Such high fatigue load is coupled with the probability of damaging the wind turbine and the risks for trespassers that could be hit by (part of) a fractured blade. Furthermore, the frequent changes in wind direction cause frequent yawing of a HAWT so that the HAWT is hardly aligned with the flow. Such average misalignment causes a drop in energy yield. A VAWT is better suitable to perform in such turbulent environment, as yawing is not required for a VAWT. But the rotor size of the VAWT should be small in order to avoid the unsteady effects coupled with frequent changes in wind direction and in order to profit from the local speed up close to buildings (Merten, p 168). Secondly, the concentrator effect of the building in combination with the wind rose should be considered. The concentrator effect of the building should fit the wind rose. Acceleration of the undisturbed wind speed by the building for only one wind direction and deceleration for all other wind directions in an omni-directional wind climate is not very profitable for the energy yield (Merten, p 168). Thirdly, the most suitable wind turbine for the site should be chosen. Compared to drag driven wind turbines, lift driven wind turbines have better prospects to become economic. The choice between a VAWT and a HAWT depends nevertheless on several additional issues. The frequent wind direction changes in the built environment are already mentioned. On roofs of sharp edged buildings the flow angle should also be considered. The flow direction close to the edges of a sharp edged building is not parallel to the roof and as a consequence, a HAWT in that flow from below shows a power drop compared to a HAWT in horizontal flow. The power output of a small H-Darrieus or lift driven VAWT increases in flow from below. The H-Darrieus 13

is therefore preferred for that flow. For concentrator buildings such as the plate concentrator and the shrouded configuration, the HAWT is preferred because the rotor of an H-Darrieus is not able to extract power from the total rotor surface (Merten, p 168). On-grid and off-grid wind turbines: Wind turbines can be used for either on-grid or offgrid applications. Most medium-size and almost all large-size wind turbines are used in grid tied applications. One of the obvious advantages for on-grid wind turbine systems is that there is no energy storage problem. As the contrast, most of small wind turbines are off-grid for residential homes, farms, telecommunications, and other applications. However, as an intermittent power source, wind power produced from off-grid wind turbines may change dramatically over a short period of time with little warning. Consequently, off-grid wind turbines are usually used in connection with batteries, diesel generators, and photovoltaic systems for improving the stability of wind power supply (Tong, p18). Safety is one of the most important concerns in wind turbines. We have to control turbine under any severe weather condition such as tornedo for reliable and safe operation. Under high wind speed conditions, the power output from a wind turbine may exceed its rated value. Thus, power control is required to control the power output within allowable fluctuations for avoiding turbine damage and stabilizing the power output. The main control systems in a modern wind turbine include pitch control, stall control (passive and active), yaw control, and others. Two primary control strategies in the power control: pitch control and stall control (Tong, p 24). Turbine operation is another aspect we have to know. Wind speed is related to turbine operation.

14

Cut-in wind speed: At this speed the wind provides enough force to begin to turn the blades. The value depends on the blade design and the friction-generating elements of the drive train (Stankovic, p 72). Start up wind speed: At this speed the blades are moving fast enough, and are capable of transferring enough torque to the drive shaft, to enable useful electricity to be generated. At this speed the generator will start to operate and produce useful electricity. Although the start-up wind speed can be very close to the cut-in speed they are not the same. For example, the Bergey XL1 turbine has a cut-in speed of 2.5m/s; however, the start-up wind speed is just over 3m/s. Although the turbine may be able to generate some electricity at 2.5m/s it may not be compatible with the electrical grid (Stankovic, p 72). Minimum annual mean wind speed: The annual mean wind speed is simply the wind speed at a certain location averaged over a year. If the annual mean wind speed at a site is equal or greater than the designated ‘minimum annual mean wind speed’, there will be enough energy in the wind on an average basis to begin to consider the idea of where the technology will move from unfeasible to feasible, a useful value to keep in mind is a minimum annual mean wind speed of 5.5m/s. It should be noted that this refers to the average speed of the wind at the turbine hub height which could be, for example, 70m or more and not the general site speed, which may have been taken from a standard weather station with an anemometer 10m above ground level (Stankovic, p 72). Rated wind speed: This corresponds to the maximum energy the turbine can extract from the wind. The rated wind speed is sometimes referred to as the ‘name plate value’ as this is the peak value quoted when referring to a particular turbine. Beyond this wind speed the turbine will

15

either passively or actively reduce the percentage of energy it will extract from the wind in order to prevent damage to the device (Stankovic, p 72). Cut-out wind speed: At this speed the wind turbine will stop turning completely in order to prevent damage to the turbine. This cut-out speed is usually quite high, such as 25m/s, and will rarely occur on most sites (Stankovic, p 72). One other wind speed term to consider is the storm-rated wind speed (or survival wind speed). This can be critical for an urban wind turbine if winds are being deliberately accelerated (Stankovic, p 72). Table 1: Typical values for key wind speed. Source: Urban Wind Energy (p 73)

16

Design case: In building environment wind has positive and negative effects, many of which are subjectively evaluated. For the structural engineer of high–rise, wind effect is a negative factor that inflates construction costs. For urban planner, wind has a positive effect as a result of carrying off contaminants and a negative effect by diminishing the comfort of pedestrians. For fire protection experts, the impact of wind on guaranteed smoke extraction in case of fire in high rise. (Eisele Page 117) Moreover, according to Carbon Trust A Natural Choice Natural Ventilation booklet, Natural ventilation systems supply fresh air and remove excess heat, odor, CO2 and other contaminants. We can benefit from all departments experience when we evaluate wind for design. Sometimes we can use it to reduce energy consumption, sometimes for reducing material usage. When we design buildings it is important to reduce energy use before generating it. Building orientation with the respect of solar angle and wind flow direction can utilize the natural ventilation, lighting and heating thus can reduce a significant amount of energy use and cost. (Afrin, p 67) After reducing energy consumption, we should design our buildings to take advantage of on side renewable energy. In this case, it is wind energy. Orientation of building is the core of the design. Every site has different constricts that affects its orientations. Sun and wind are two of them. Wind is an important aspect not only for generating electricity but also for structure of the buildings. Even though, we don’t install a turbine to our building we have to know how our buildings are affected by wind load. Which direction wind comes from, which direction it goes. From how many directions it comes to our site. In order to understand wind direction, we can use wind rose. Wind rose gives a very succinct but information-laden view of how wind speed and direction are typically distributed at

17

a particular location. Presented in a circular format, the wind rose shows the frequency of winds blowing from particular directions. (NRCS)

Figure 10: Building orientation considering wind load. Source: High –Rise Manuel: Typology and Design, Construction and Technology (p 118) Now it is time to install a wind turbine to our buildings. There are two important criteria when installing a wind turbine to a building. The first one is the place we put the turbine, second is how to shape the building to accelerate natural wind speed which hit the turbine. For optimum result, it is important to shape the building with wind energy in mind. With the right shape, turbine efficiency can be improved significantly. Generally, there are 6 different ways to integrate a turbine to a building. They have their advantages and disadvantages. We will only compare them with their wind acceleration which affects turbine efficiency. Before making any design decision, you should consider all affects. (Stankovic, p 160) 1. This option primarily takes advantage of the opportunity to access higher quality winds that tend to exist at greater altitudes. These winds will not only have a relatively

18

high energy content but are also likely to be less turbulent. However, there will be a degree of natural wind acceleration with a ~10 per cent energy increase for the natural wind acceleration alone (Stankovic, p 160) We can see lots of examples of this option. 2. This option takes advantage of the higher quality winds at higher altitudes and additional local acceleration with a ~15 per cent energy increase for the local wind acceleration The rounded façade will mean the tower height can be much lower (Stankovic, p160). 3. This option takes advantage of the higher quality winds at higher altitudes and notable local acceleration especially if the wind character of the region is bi-directional ~20 per cent energy increase due to local acceleration (Stankovic, p 160).

4. This option takes advantage of the higher quality winds at higher altitudes and substantial local acceleration even if the wind distribution is the same for all directions a 25 per cent energy increase over a free-standing equivalent can be achieved with an increase of 40 per cent for bi-directional winds. Although this option requires a loss of lettable space there are a number of examples of large/tall buildings replacing lettable area with a ‘feature opening’ – e.g. for aesthetics, sky gardens or to relieve wind loading. In this case a feature opening can be used to generate wind energy (Stankovic, p160). 5. This is similar to the square concentrator with the exception that the shape lends itself to HAWT and energy yields are further increased for example for a uniform wind a 35 per cent energy increase over a free-standing equivalent can be achieved with an increase of 50 per cent for bi-directional winds (Stankovic p160).

19

6. This option takes some advantage of the higher quality winds at higher altitudes. However, unless the building form is optimized for the local wind character it is likely that the turbines will not perform as well as free-standing equivalents (around 80–90 per cent of the total energy) (Stankovic, p 160).

7. A range of architectural forms are possible when a multi building development is being considered. Significant local acceleration can be achieved for reasonably basic, non- optimized forms around 10 per cent extra energy compared to a free-standing equivalent (Stankovic, p 160). Since growing demand on renewable energy in the world, these types are implemented all over the world by architects and engineers. We will look at two buildings that implemented all the information we covered in this paper. Picture 1: Bahrain World Trade Center in Bahrain, completed in 2008, designed by Atkins. The two 50 story sail shaped office towers taper to a height of 240m and support three 29m diameter horizontal-axis wind turbines. The towers are harmoniously integrated on top of a three story sculpted podium and basement which accommodates a new shopping center, restaurants, business center and car parking. The elliptical plan forms and sail-like profiles act as aerofoil, funneling the onshore breeze between them as well as creating a negative pressure

20

behind, thus accelerating wind velocity between the two towers. Vertically, the sculpting of the towers is also a function of airflow dynamics. As they taper upwards, their aerofoil sections reduce. This effect when combined with the increasing velocity of the onshore breeze at increasing heights creates a near equal regime of wind velocity on each of the three turbines. Understanding and utilizing this phenomenon has been one of the key factors that has allowed the practical integration of wind turbine generators in a commercial building design. (Killa, p2) Picture 2: Pearl River Tower, in Guangzhou, China, completed in 2012, designed by SOM. The initial design concept was to develop a super-tall building capable of having a “net-zero” annual energy impact on the city with a view to being the most energy efficient super-tall building in the world. The brief for the Pearl River Tower developed into a 71-story, 310m tall office tower with associated a conference facilities, a total gross area of approximately 2.2 million square feet (Frechette, p 3). Design process took into consideration the interaction of the whole building structure and systems and its site location. The key to a successful high performance requires the design team to consider the site, energy sources both active and passive, materials, indoor air quality, and how they might become incorporated into building form that is more than gestural. These considerations include simple concepts including site analysis, building orientation, wind direction, sun path analysis to more sophisticated approaches and technologies including the use of radiant ceilings, double wall systems, photo-voltaic and wind turbine technology (Frechette, p 8). 21

The building incorporates four large openings, approximately 3x4 meters wide. The facades are shaped to decrease the drag forces and optimize the wind velocity passing through the four openings. These openings function as ‘pressure relief’ valves for the building. This strategy maximizes the wind power potential at these four locations as the power potential from the wind speed is a cube function of wind velocity, therefore a small increase in velocity can translate to larger increase in power potential (Frechette, p 8). The Pearl River Tower will implement vertical axis turbines, as they are capable of harnessing wind from both prevailing wind direction with mirror efficiency loss. The building design capitalizes the pressure difference between the windward and leeward side of the building and will facilitate air flow through the four openings located adjacent to the mechanical floors within the building. At the windward side there is a stagnation condition that causes the locally increased pressure to be higher than the undisturbed pressure approaching the building. At the leeward side of the building a low pressure exists that is induced by the high velocity flow at the sides and roof of the building (Frechette, p 8). There are other examples we see in news, however we don’t have technical information on them. We cannot accept them as source. I will express them according to websites’ information to show wind turbine installation. Pictures 3: Starda Tower in London At 147 metres, the newly opened Strata is London's tallest residential building. The turbine with nine-meter blades integrated. If the turbines work as planned, they should generate

22

8% of this 43-storey building's energy needs. This is roughly enough to run its electrical and mechanical services (including three express lifts and automated window-cleaning rigs) as well as the lighting, heating and ventilation of its public spaces, which include an underground car and cycle park. Source: http://www.guardian.co.uk/artanddesign/2010/jul/18/strata-tower-london-greenarchitecture ( Glancey,Jonathan. Sunday 18 July 2010) (April 2013) Picture 4: Gullwing Twin Wind Tower in Dubai. Architects and designers at ARXX Studio have designed a self-sustaining twin tower skyscraper for Dubai, which generates all the energy it needs from renewable sources. Christened the Gullwing Twin Wind Towers, the tower incorporates a unique energy generating system that uses wind turbine hinges attached to the building to generate electricity from wind. The wings are circular structure, which drive turbines to produce clean electricity. The turbines are cylindrical with circular sections, where each section contains a series of bladed rings to capture the wind. The towers have been designed in the form of cylinders to simulate a tornado effect to maximize energy generation. Source: http://www.greencleaningideas.com/2010/08/gullwingtwin-wind-tower-skyscraper-is-wrapped-with-wind-turbines/ (April, 2013) 23

Picture 5: 525 Golden Gate, in San Francisco CA 525 Golden Gate in comparison to similarly-sized office buildings features 50% less of a carbon footprint, uses 32% less energy, and consumes 60% less water. The 13level, 277,511 gross-square-foot, $190 million SFPUC headquarters building is one of the greenest urban office buildings of its kind, bringing together in a modern, contextually-designed office tower some of the most innovative new technologies at the forefront of building design. A wind turbine tower on the north facade, solar panels on sunny exteriors, sun-shading and other techniques combine to make the building power-efficient, using 32% less energy than similarly-sized office buildings. The integrated, hybrid solar array and wind turbine installation can generate up to 227,000 kilowatt hours per year or 7% of the building’s energy needs. Source: http://questpointsolarsolutions.com/?tag=wind-turbines (April, 2013) Environmental affects: Wind energy is one of the cleanest and most environmentally neutral energy sources in the world today. Compared to conventional fossil fuel energy sources, wind energy generation does not degrade the quality of our air and water and can make important contributions to reducing climate-change effects and meeting national energy security goals. In addition, it avoids environmental effects from the mining, drilling, and hazardous waste storage associated with using fossil fuels. Wind energy offers many ecosystem benefits, especially as compared to other forms of electricity production. Wind energy production can also, however, negatively affect wildlife habitat and individual species, and measures to mitigate prospective 24

impacts may be required. As with all responsible industrial development, wind power facilities need to adhere to high standards for environmental protection. (U.S. DOE) Environmental concerns associated with wind energy development are noise, visual impact, oscillating shadow, avian/bat mortality and other concerns. Noise: Like all mechanical systems, wind turbines produce some noise when they operate. Most of the turbine noise is masked by the sound of the wind itself, and the turbines run only when the wind blows. In recent years, engineers have made design changes to reduce the noise from wind turbines. Early model turbines are generally noisier than most new and larger models. As wind turbines have become more efficient, more of the wind is converted into rotational torque and less into acoustic noise. Additionally, proper siting and insulating materials can be used to minimize noise impacts. (1) Besides noise in the audible frequencies so-called infra-noise has also been the subject of concern. (Stiebler, p 7) Oscillating shadow: The oscillating shadow of a WES (Wind Energy Solutions) due to the rotating blades optical can also be a source of optical disturbance for residents (“disco effect”). Depending on local conditions, minimum distances are required, e.g. 6 times the overall height as mandated by a court. (Stiebler, p 7) Visual Impacts: Because they must generally be sited in exposed places, wind turbines are often highly visible; however, being visible is not necessarily the same as being intrusive. Aesthetic issues are by their nature highly subjective. Proper siting decisions can help to avoid any aesthetic impacts. Avian/Bat Mortality: Bird and bat deaths are one of the most controversial biological issues related to wind turbines. The deaths of birds and bats at wind farm sites have raised concerns by fish and wildlife agencies and conservation groups. On the other hand, several large 25

wind facilities have operated for years with only minor impacts on these animals. To try to address this issue, the wind industry and government agencies have sponsored research into collisions, relevant bird and bat behavior, mitigation measures, and appropriate study design protocols. In addition, project developers are required to collect data through monitoring efforts at existing and proposed wind energy sites. Careful site selection is needed to minimize fatalities and in some cases additional research may be needed to address bird and bat impact issues. While structures such as smokestacks, lighthouses, tall buildings, and radio and television towers have also been associated with bird and bat kills, bird and bat mortality is a serious concern for the wind industry. (Wind Energy Development Programmatic EIS ) Other Concerns: Unlike most other generation technologies, wind turbines do not use combustion to generate electricity, and hence don't produce air emissions. The only potentially toxic or hazardous materials are relatively small amounts of lubricating oils and hydraulic and insulating fluids. Therefore, contamination of surface or ground water or soils is highly unlikely. The primary health and safety considerations are related to blade movement and the presence of industrial equipment in areas potentially accessible to the public. An additional concern associated with wind turbines is potential interference with radar and telecommunication facilities. And like all electrical generating facilities, wind generators produce electric and generating facilities, wind generators produce electric and magnetic fields. (Wind Energy Development Programmatic EIS) Vibration: Hence, compared to the HAWT, the rotational sampling frequency of a VAWT is twice as high, because the blades of the VAWT pass the turbulent structures twice: once at the upwind side of the VAWT and once at the downwind side of the VAWT. Care should be taken to avoid frequencies of the HAWT or VAWT close to the eigenfrequencies (resonance 26

frequency of a system) of the support structure (building roof, building walls, mast, etc.) on which they are mounted (Merten, p 9). Shadow flicker: Situations where the wind turbines blades are within the direct path of the sunrays to the eyes or reflections of the sun’s rays on the wind turbine blades should be avoided. The latter is simple to solve with dull paint. Situations where the blades are within the direct path of the sun’s rays are a nuisance if the observer is close to the wind turbine and at visible frequencies below some 20 Hz. Compared to the Darrieus, HAWT’s have more problems in avoiding those low frequencies because of the single-blade passage where the Darrieus has a double-blade passage between the sunrays and the observer instead. The HAWT is thus more likely to cause hindrance because of shadow flickering below 20 Hz (Merten, p 10). Conclusion: We can generate electricity from tall buildings as long as we have enough information. The first thing we have to do is look at wind availability in macro level. This data can be obtained from local weather station. If there is enough wind available, we have to evaluate our site specifically with a professional. In case we have enough wind to generate power, we should look at the constrains of our site. Which direction wind flows, what blocks it. We have to orient our building to take advantage of wind while considering wind loads for structure. Then we have to decide where to install a turbine or turbines. After choosing the right place for the turbine, we have to accelerate the wind speed with our design. Finally, we have to keep in mind that even though wind is a clean energy resource, there are some minor environmental effects that should be considered on designing the buildings.

27

ASSOCIATIONS American Wind Energy Association AWEA http://www.awea.org/learnabout/ National Renewable Energy Laboratory NREL http://www.nrel.gov/ The European Wind Energy Association EWEA http://www.ewea.org/ U.S. Department of Energy DOE http://www1.eere.energy.gov/wind/small_wind_system_faqs.html Global Wind Energy Council http://www.gwec.net/

Citations Afrin, Shahrina. Green Skyscraper: Integration of Plants into Skyscraper. Stockholm 2009. KTH, Department of Urban Planning and Environment Division of Urban and Regional Studies Kungliga Tekniska högskolan. Master Thesis. www.infra.kth.se/sb/sp Botkin, Daniel B.; Keller, Edward. Environmental Science: Earth as a Living Planet. USA: John Wiley & Sons, Inc 2011.

Chiras, Dan. Wind PowerBasics. Canada. New Society Publishers 2010. Eisele, Johann; Kloft, Ellen. High –Rise Manuel: Typology and Design, Construction and Technology.

Fleming, Robins. Wind Stresses in Buildings: With a Chapter on Earthquakes and Earthquake Resistance. London. Chapman & Hall 1930.

28

Frechette, Roger E. Gilchrist, Russell. ‘Towards Zero Energy’ A Case Study of the Pearl River Tower, Guangzhou, China. CTBUH (Council on Tall Building and Urban Habitat) Technical Paper. Dubai 2008. http://ctbuh.org/LinkClick.aspx?fileticket=%2bpedN46s7Es%3d&tabid=486&language= en-US/

Johnson, Gary. L. Wind Energy Systems. Manhattan, KS. October 2006 Killa, Shaun. Smith, Richard F. Harnessing Energy in Tall Buildings: Bahrain World Trade Center and Beyond. CTBUH (Council on Tall Building and Urban Habitat) Technical Paper. Dubai 2008. http://ctbuh.org/LinkClick.aspx?fileticket=DGjD8kpuHRk%3d&tabid=486&language=e n-US/

Muyeen, S.M. Wind Power. Croatia. Intech 2010

Merten, Sander. Wind Energy in the Built Environment: Concentrator Effects of Buildings. UK. Multi Science 2006. Stankovic, Sinisa; Campbell, Neil; Harries, Alan. Urban Wind Energy. UK and USA: Earthscan, 2009. Stiebler, Manfred. Wind Energy Systems for Electric Power Generation. Germany. SpringerVerlag Berlin Heidelberg 2008 Tong, Wei. Wind Power Generation and Wind Turbine Design. USA and UK: WIT press, 2010 Thomas, Derek. Architecture and the Urban Environment; A Vision for the New Age.

Carbon Trust, A Natural Choice Natural Ventilation. http://www.carbontrust.com/media/81365/ctg048-a-natural-choice-naturalventilation.pdf 29

CATs (Coherent Application Threads). Wind Turbines. Boston University, Mechanical Engineering. http://people.bu.edu/noahb/files/wind_turbine_main.pdf U.S DOE United States Department of Energy. 20% Wind Energy by 2030. Springfield, VA. 2008 http://www.nrel.gov/docs/fy08osti/41869.pdf WEDP EIS : Wind Energy Development Programmatic EIS, April 2013. http://windeis.anl.gov/guide/concern/ NRCS, U.S. Department of Agriculture Natural Resources Conservation Services. http://www.wcc.nrcs.usda.gov/climate/windrose.html Utility-Scale Land-Based 80-Meter Wind Maps http://www.windpoweringamerica.gov/wind_maps.asp)

30