THE IMPORTANCE OF SITE SELECTION FOR SE

THE IMPORTANCE OF SITE SELECTION FOR SETTING UP A WIND TURBINE
Arjun Raghunandan1, Ganavi Gowda2, Gowrishankar Ramanan3, Akshay Pandian 4
1,2Telecommunication Engineering, 3Electrical & Electronics Engineering, 4Electronics & Communication Engineering 3RV College of Engineering, Bangalore, 1, 2, 4 MS RAMAIAH Institute of Technology, Bangalore
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Abstract - A wind energy system transforms the kinetic energy of the wind into mechanical or electrical energy that can be harnessed for practical use. Building a wind turbine is far more than simply a matter of finding a field or mountaintop where the wind is blowing and plopping one down. A great deal of attention should be given to finding the proper site for a wind turbine. The main factor one should consider is the average speed of the wind over an extended time. Estimation of the wind power potential for a site is the most important requirement for selecting a site for the installation of a wind turbine. Also wind turbines should be sited well above trees, buildings, and other obstacles else, the result will be poor energy production and increased wear and tear on the turbine. One way to get rid of this is to place the wind turbine on a tall tower. When selecting a place for setting up a wind turbine, engineers consider factors such as wind hazards, characteristics of the land that affect wind speed, and the effects of one turbine on nearby turbines in wind farms. The other factors that are important for selecting a site for installation of wind turbines are Hill effect, Roughness, or the amount of friction that Earth's surface exerts on wind, Tunnel effect, Turbulence, Variations in wind speed, Wind obstacles and Wind shear. This paper will emphasis on the necessary inspections which are to be done on the site before installing a Wind Turbine.

Key words – Renewable Energy Sources (RES), Wind Turbines, Wind Power Potential, Tunnel effect, Turbulence, Wind obstacles, Wind shear. I. INTRODUCTION

In recent years an increasing number of countries have implemented policy measures to promote renewable energy. However, the most important problem that the policy makers face with is the conflicting linguistic terms and subjective opinions on energy and Environment policy. Although wind power is a never ending green resource, assessment of environmental risks and impacts- which comprise the backbone of environmental policy- in the context of specific projects or sites often are necessary to explicate and weigh the environmental trade-offs that are involved. In the case of wind farms, a number of turbines (ranging from about 250 kW to 750 kW) are connected together to generate large amounts of power. Apart from the constraints resulting from the number of turbines, any site selection should think over the technical, economic, social, environmental and political aspects. Each aspect uses criteria for its own evaluation. Wind energy can be harnessed by a single wind turbine or several power generating units which are commonly called as wind farm. A wind farm has the following components:
Wind turbines
Towers
Transformers
Internal access roads
Transformer station
Transmission system connecting the facility to the national grid
The blades of the turbine collect the kinetic energy of the wind. Flow of the wind over the blade causes lift which results a rotation. The blades are connected to a drive shaft that turns an electric generator through a gear box. The profitability of generating wind energy mainly depends on the site of the wind farm. An inadequate site selection would lead to lower than expected wind power capture, increased maintenance costs, and so on.

II. TECHNICAL CONSIDERATIONS

Many technical factors affect the decision making on site selection including wind speed, land topography and geology, grid structure and distance and turbine size.

A) Wind speed

The viability of wind power in a given site depends on having sufficient wind speed available at the height at which the turbine is to be installed [1]. Any choice of wind turbine design must be based on the average wind velocity at the selected wind turbine construction site [2]. Cubic wind speed directly related with the energy generation potential of wind. Site’s wind energy potential can be formulated with the wind power density which represents the effect of wind speed distribution and wind speed. Wind speed data must be recorded for at least 1 year in order to have mapping for potential energy yield over site. WindPro, WAsP, MesoMap are most widely used wind source mesoscale mapping software that use a variety of parameters in order to combine weather and wind flow models. [3]

Fig1. Hierarchy structure diagram for wind farm site selection

B) Land topography and geology

The speed and the direction of wind can be various depending on the characteristics of topography [4]. In flat areas where there is nothing to interfere with wind flow, at least 2600-6000 m2/MW may be required [5]. More land may be needed in areas with more rugged or complex topography and/or wind flow interference. Wind turbines are usually sited on farms that have slope smaller than 10-20% [6]. Garrique or maquis are more advantageous than forests as land cover for wind farm sitting [7]. It would be needed to clear and grade land in order to provide roads for trucks, constructions trailer or equipment storage area, access to construction site. Soil stability, foundation requirements, drainage and erosion problems must be assess by conducting geotechnical study. [3]

C) Grid structure and distance

The connection of wind turbines to an electricity grid can potentially affect reliability of supply and power quality, due to the unpredictable fluctuations in wind power output [8]. Feeding intermittent power into electricity grids can affect A Holistic Approach for Wind Farm Site Selection by Using FAHP 217 power quality. The impact depends primarily on the degree to which the intermittent source contributes to instantaneous load (i.e. on power penetration). At low penetrations, wind farms can be connected to the grid as active power generators, with control tasks concentrated at conventional plants. Many studies agree that penetrations of up to 10–20% can be absorbed in electricity networks without adversely affecting power quality and needing extra reserve capacity [8]. III. ECONOMIC CONSIDERATIONS

The economic sub factors that affect the site selection include capital cost, land cost and operational and management costs. One of the biggest advantages of renewable energy sources is that there is no fuel cost during operation of the plant, therefore contribution of capital cost to the overall wind farm economy is very high.

A) Capital cost

Construction, electrical connection, grid connection, planning, wind turbines, approvals, utilities and management are the main components of capital cost for wind farm projects [9]. There will be meteorological towers which will include anemometers to measure wind speed and direction, a data logger and meteorological mast. Steel tube or lattice could be used to construct these towers and would be free standing or guyed. It is required to take a special permit in order to build such a meteorological tower [10]. Capital cost related with these components will change due to region that wind farm is located. It would be needed to clear about 150-250 feet around a wind turbine site to prepare wind turbine construction. Electrical collection lines are constructed in order to connect wind turbines and collection substation. Based on the land geometry, costs of these lines vary. Capital cost of a typical wind farm project change between £600,000 and £1,000,000 per MW per annum. Turbine costs (64%), construction (13%) and electrical infrastructure (8%) costs constitute the major items of capital expenditures [11]. The amount of transmission infrastructure that has to be installed directly increases the cost of building a wind farm. Therefore, availability of existing transmission lines should be considered in selecting a site.

B) Land cost

For the site selection, main economic factor is the cost of the land where the wind farm is constructed; because, the cost of land primarily depends on the region, soil condition and the distance from the residential area. Since large areas are needed for wind farms, the rent or cost of the land becomes the major factor of site selection. For a commercially viable project, the size of the site is a crucial parameter.

C) Operational and management cost

It is estimated that O&M cost of wind farms require about £8000-£10,000 per MW per annum. Business rates, maintenance expenses, rents, staff payments are main components of O&M costs. O&M cost are usually very small percentage of total investment costs of wind farm projects [11]

D) Electricity market

Existing of an electricity market for the energy generated is an important factor affecting the economic benefits of the project. There should be energy demand in regions close to wind farms. When the intermittency of the wind energy taken into consideration, a continuous electricity market gains an extra importance for the region wind farm sited.

E) Incentives

Incentives are economic tools applied in order to encourage investors to support socially beneficial projects such as renewable energy projects that reduce the number of thermal power plants and so the carbon emissions. Applications of incentives such as specific levy exemptions and renewables obligations certificates vary from region to region [11]. For example, China has been applying some concession programs for wind power generation since 2005 [12]. In Turkey, in the Law on The Utilization of Renewable Energy Resources For The Purpose of Generating Electrical Energy, there is a special case for the investors in the cost of land. In the case of utilization of property which is under the possession of Forestry or Treasury or under the sovereignty of the State for the purpose of generating electricity from the renewable energy resources included in the law, these territories are permitted on the basis of its sale price, rented, given right of access, or usage permission by the Ministry of Environment and Forestry or the Ministry of Finance [13]. A 50% deduction shall be implemented for permission, rent, right of access, and usage permission in the investment period.

IV. ENVIRONMENTAL CONSIDERATIONS

The environmental sub factors that affect the site selection of a wind farm include visual impact, electromagnetic interference, wild life and endangered species and noise impact. Wind turbines can generate noise while they are working and their image can be incompatible with the general view of the region.

A) Visual impact

Wind turbines are located in windy places, and most of the time, those places are highly visible. To many people, those big towers with 2 or 3 blades create visual pollution. To minimize the impacts of visual pollution, many investors implement the actions listed below:

The wind turbine tower, nacelle and blades as well as the transformer box, is painted a neutral color to blend in with the surroundings.
The turbine is sited to reduce the possibility of shadow flicker falling on surrounding inhabited structures.

B) Wild life & endangered species

Wind farms affect birds mainly through the actions listed below:
Collision with turbines and associated power lines
Disturbance leading to displacement including barriers to movement, loss of habitat resulting from wind turbines [1][5]

To minimize the risk of bird collision, site selection should be done precisely. But decision making in site selection is problematic due to the reason that migration roads of birds may vary from one year to another.

C) Electromagnetic interference

Electromagnetic interference is an electromagnetic disturbance that interrupts, obstructs, or degrades the effective performance of electronics or electrical equipment [14]. Wind turbines may reflect, scatter or diffract the electromagnetic waves which in turn interfere with the original signal arriving at the receiver.

D) Noise impact

Noise can generally be classified according to its two main sources: aerodynamic and mechanical. Aerodynamic noise is produced when the turbine blades interact with eddies caused by atmospheric turbulence. Mechanical noise is generated by the rotor machinery such as the gearbox and generator.

V. SOCIAL CONSIDERATIONS

Social factors that affect the selection of a site include public acceptance, distance from residential area and alternative land use options of candidate wind farm site. Some regulatory procedures may set restrictions or incentives to apply wind farm projects. Public acceptance is vital for the application of that kind of projects. Public may oppose projects because of possible environmental or social effects.

A) Regulatory boundaries

There may be some national or international level regulation related with the construction and operation of wind farms. These regulations must be explored before evaluating the socio-political position of a wind farm project. Some nations encourage use of renewable energy resource and develop special regulations for the renewable energy generation plants. On the other hand, there could be some restrictions related with the construction and operation of energy generating plant.

B) Public acceptance

Public is the most vital component of a region and their opposition to issues can lead to abolish proposed projects. Support of public for wind energy generation is expected to be high in general but proposed wind farms have often been met with strong local opposition. In the study of public psychology [15], it is stated that nearby residents are more likely to become involved in decision making.

C) Land use

Land use affects the decision of wind farm siting from two points of view. Firstly, there are some cases where no wind farms can be built although sufficient wind speed was detected. These cases are mainly related with land use or condition. Land related constraints are:
Forest area
Wetlands
Land of high productivity
Archaeological sites
Aviation zones
Military zones

Alternative land uses of site where wind farm to be constructed affect the decision of wind farm site.

D) Distance from the residential area

Wind turbines are giant machines that can be over 120m tall and have blades that sweep up to 6000m2 in area. Because of their big size, these machines have the potential to disturb visual scene. Besides, noise and vibration stemming from the wind turbines may cause residents to suffer from sleep disturbance, headaches, visual blurring. Those types of complaints can be avoided if the wind turbines are sited a considerable distance from the residential area.

VI. CONCLUSION

Setting up of wind farms therefore is a tedious process which may take years for it to be operational. Long duration case studies and research is required to make sure the harmful effects on the environment and other associated concerns stated above, are addressed and minimized.

Some steps that can be taken to address these issues are given below:
Identify the area and study its topographical structure. Map the important facilities such as existing power grid, etc., close to it.
Make sure the located area is far from habitation, so that it does not raise concerns to the locals.
If forest land is used, the animals and other species have to be safely shifted to a wild reserve, so that they are not harmed in any ways.
Government should set up policies which would promote set up of wind farms and use of power generated, efficiently.
Wind farms should be set up on elevated land such as a hill, where the wind speed is more, to generate more power.

REFERENCES

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