Clean energy is the energy that has the least environmental impact and which is least polluting, such as wind. This report pictures a brief description about wind energy. Then the current wind power generation technology is discussed. Afterwards, current status of wind power generation throughout the whole world is depicted followed by an overview of the enablers of wind power generation growth and the projected future prospect. Finally, the challenges of this paradigm shift from traditional energy sources to wind energy sources are discussed from the technical, economical, political and environmental point of view.
Index Terms-Wind energy, clean energy, challenges of wind energy growth.
Introduction
The distinctive feature of clean energy is their lower carbon emissions and less pollution. Clean energy technologies include renewable energy, hybrid and co-generation, and energy efficiency technologies for power generation and alternative fuels. Wind is thought to be the one of the most promising clean energy source. They produce power for a wide range of applications without producing no or fewer pollutants than conventional technologies and unlike fossil fuel and they are not depleted over time [1]. Wind energy is actually another form of solar energy. The radiation from the sun heats different regions of the earth at different rates-most notably during the day and night, but also different surfaces are heated differently (e.g., water and land). Therefore they absorb or reflect heat at different rates. This in turn causes different portions of the atmosphere to warm differently. Hot air rises and reduces the atmospheric pressure at the earth's surface. Then cooler flows in to replace it. The outcome is wind with kinetic energy. A wind energy system converts the kinetic energy of the wind into mechanical or electrical energy that can be of our use [2]. This report presents wind as a clean energy source, wind power generation technology, present status and future prospect of wind power generation. At the last part of this report, the impediments on the way of wind power generation growth are discussed.
Wind Power Generation Technology
Wind electric turbines generate electricity for homes and businesses and for sale to utilities. There are two basic designs of wind electric turbines: vertical-axis (VAWT) and horizontal-axis (HAWT) machines as shown kin Fig. 1 [2]. Horizontal-axis wind turbines are most common today, constituting nearly all of the "utility-scale" (100 kilowatts, kW, capacity and larger) turbines in the global market [3].
HAWT has number of advantages. The variable blade pitch of HAWT gives the turbine blades the optimum angle of wind cut. It allows the angle of attack to be remotely adjusted gives greater control. Therefore the turbine collects the maximum amount of wind energy for the time of day and season. The tall tower base allows operation in sites with wind shear. The efficiency of this type fo system is also higher since the blades always move perpendicular to the wind, thus it receives power through the whole rotation. One of the main advantage of the HAWT is the transportation difficulty caused by the tall towers and blades up to 45 meters long. Tall HAWT are also difficult to install, as they need very tall and expensive cranes and skilled operators. Massive tower construction is required to support the heavy blades, gearbox, and generator.
The main advantages of the VAWT is the tower structure is not usually massive and are more frequently mounted with the lower bearing mounted near the land. The main disadvantages of the VAWT are, changing out parts is very difficult without removing the structure of a VAWT as its components are located on the ground and bears the weight of the structure above it. Near the ground the wind speeds are lower due to the ground's surface drag where rotor blades are located, therefore VAWTs may not produce as much energy at a given site as a HAWT with the same height.
(a) (b)
Fig. 1. Wind turbine configuration (a) Horizontal axis (b) Vertical axis [2].
Almost all wind turbines producing electricity consist of rotor blades which rotate around a hub. The hub is connected to a gearbox and generator. The gearbox and the generator are located inside the nacelle. Nacelle is the house of the electrical components and is mounted at the top of the tower. Rotor diameters of wind turbines can ranges up to 80 metres, smaller machines (around 30 meters) are typical in developing countries. Most wind turbines have three rotor blades which are usually made of fibreglass-reinforced polyester or wood-epoxy. The blades rotate at 10-30 revolutions per minute at constant speed, although an increasing number of machines operate at a variable speed. Power is controlled automatically as wind speed varies. The turbines stop operation at very high wind speeds to protect them from damage. Although most of them have gearboxes; there are increasing numbers with direct drives. The yaw mechanism turns the turbine so that it faces the wind. Sensors are used to monitor wind direction and the tower head is turned to face the wind. Towers are mostly cylindrical and made of steel. Lattice towers are also used in some locations. Towers range from 25m to 75m in height [2].
Present Status of Wind Power
Despite the recent economic depression throughout the whole world, the wind energy experienced tremendous growth. A double digit growth for the wind energy market is expected to be maintained despite the general economic crisis in the coming few years [4]. 11 of the top 15 countries who represents over 80% of the world market, world wind energy association (WWEA) recorded 5374 MW new installed capacity in the first quarter of 2009, equalling an increase of 23% compared with last year in the same countries [4]. WWEA keeps its previous prevision of a total installed capacity of 152,000 MW worldwide by the end of 2009, which will mean a new record of over 30'000 MW newly installed capacity within one year. This represents a market growth of 25% compared with last year [4].
Fig. 2. Total and new installed capacity in of wind power in MW [4].
As shown in Fig. 2, the status of wind energy is a stable, profitable and low-risk investment. Although due to financing challenges some wind energy projects are postponed, the overall market development can still compensate such delays. As a matter of fact, in most cases the project show down are a direct consequence of new regulations and bureaucratic delays rather than of financing difficulties. And this situation is expected to improve over time. Despite all these barriers, the annual growth rate continued to increase since the year 2004, reaching 31.7% in 2009 after 29.0% in 2008, 26.6% in 2007, 25.6% in the year 2006 and 23.8% in 2005 [4].
All wind turbines installed within 2009 contribute 340TWhr to the worldwide electricity supply which represents 2% of the global electricity demand [4]. Even wind has become one of the largest electricity sources in some countries and regions. In Denmark 20% of the generated electricity comes from wind energy. Other countries with high wind every penetration includes Portugal with 15%, Spain with 14% and Germany with 9% [4].
Driving Force of Future Wind Energy Growth
In [5], six major forces are identified which are pushing wind power into the mainstream and driving the rapid growth across the globe. They are,
Costs: Probably the most powerful force driving current wind energy growth is simple economics. As a general trend, wind-energy costs are falling and costs of fossil fuel energy are going up. Actually the future of wind energy depends on the reduction of manufacturing and operating costs.
Capital: Influx of capital is changing the wind energy landscape, with billions of currencies poured in from a myriad of public and private sector sources. Where there's money, technology expansion is sure to follow. Capital, in the form of corporate investments, VC, government grants, project finance, debt equity, and the public stock markets, is critical to the growth of any emerging sector. In fact, all the major technology expansions, from biotech to the computer revolution, owe their success to an influx of capital from a range of sources. Wind energy technology is also following the same trend.
Competition: Many governments and companies are competing aggressively to dominate the wind energy sector. From small cities to urban metropolises and from states to nations, governments at every level are competing to be leaders in the clean tech revolution. A number of factors are driving this competitive field. The most important of which is the need to build strong local economy and develop high paying local jobs. Equally important is the competition for limited global energy is driving the wind power technology to reduce the energy dependency over the other countries.
China: Wind energy growth is also driven by huge demand for energy in China, India and other developing nations. China is facing energy crisis issues. With a projected migration of more than 400 million people from rural areas to cities by 2020, China will not be able to sustain its growth if it doesn't widely embrace clean technology like wind [5].
Consumers: Concerned consumers are demanding cleaner products and services that are non-polluting, have least impact on environment and embrace quality over quantity like wind. Actually, without consumer demand, no market would materialize. Today, high price of conventional energy, contaminated ecosystems and growing awareness against climate change and the geopolitical costs associated with fossil fuels are driving a change in consumer attitudes. As a result, consumer demands for clean-tech products and services are rising rapidly. That's forcing companies to produce cleaner, more efficient wind energy and market them aggressively.
Climate: The debate about climate change has gone from uncertainty to peer-reviewed certainty and smart business like wind energy generation is gaining attention. Concern is growing about the climate-change consequences caused by our continued dependence on carbon-intensive, GHG-emitting fossil fuel based energy and transportation sources and manufacturing processes. This public concern is driving wind energy based clean technology investment.
Future of Wind Power Generation
As discussed in previous section that the global financial and economic crisis had almost no negative impact on the general development of the wind sector worldwide. Many governments showed keen interest to accelerate wind deployment in their countries. This indicates that investment in wind and other renewable technologies is seen by them as the answer to the financial as well as to the still ongoing energy crisis. Hence, it is almost inevitably expected that future politically stable and improved frameworks will lead to more investment in wind utilisation around the globe [4].
Within this political environment and as predicted in the world wind energy report 2008, the finance sector has started to understand that wind technology is in principle a low-risk investment not only for the investors themselves if the right policies are in place.
In addition to such direct microeconomic benefits for wind investors, wind turbines stabilise the overall energy prices and hence reduce general economic risks in a country, while reducing the dependency on (in most cases imported) fossil and nuclear resources.
Interesting prospects for financing wind and other renewable technologies came up in the context of the UN climate change discussions: The International Renewable Energy Alliance proposed at the COP15 in Copenhagen a Global Fund for Renewable Energy Investment, including a Global Feed-in Tariff programme [4 wwea]. This proposal would enable mainly developing countries to invest on a large scale in renewable energy and has already attracted major interest amongst governments and international organisations. Adopted in the frame of the UNFCCC, it would pave the way for an accelerated huge and worldwide boom of renewable energy deployment [4].
Increasing awareness of the economic, social and environmental benefits of wind energy will further boost investment in new wind farms. Assuming that the global financial situation will improve substantially in the near future, many further world regions will be able to raise the funds that are necessary to speed up wind energy deployment.
Fig. 2. Current wind power generation (from 1997 to 2009) and projected wind power generation in GW [4].
Another positive factor will be the supportive role of the International Renewable Energy Agency - founded in January 2009 and becoming more operational in 2010. IRENA with its current 143 member countries will contribute to the global dissemination of know-how and through acting as a balancing lobby at international decision making processes such as the UN climate change negotiations. n the one hand, the United Nations failed to come to a climate change agreement at the COP15 in Copenhagen - which might have brought additional incentives for investment in emission free technologies such as wind. However, wind investment so far was only marginally based on the contributions from carbon finance. Additional funds currently under discussion may give additional incentives and increase the growth rates of wind power mainly in the developing world.
Further growth can especially be expected in the leading wind markets China (with its recently implemented feed-in tariff), USA (with more and more favourable frameworks expected both on national but also on state level), Germany, Spain and India and in many further countries in Europe, especially in Eastern Europe, but also in many Asian and Latin American countries. Major projects are also expected to be implemented in some African countries, notably in South Africa with its feed-in tariff and in North Africa.
Another, often neglected success factor of wind are community power ownership models. Such models are re-gaining strength and are expected to contribute substantially to the further growth of wind power in many world regions, by mobilising additional economic and social support for wind technology. New and notable examples can be found in the United Kingdom (in particular in Scotland), Canada, Australia as well as in South Africa and in many other parts of the world.
Based on the accelerated growth rates, WWEA increases its expectations for the future growth of the global wind capacity: By the end of the year 2020, at least 1,900,000 Megawatt can be expected to be installed globally.
>>>It is estimated that the earth has enough wind power resources to meet current global energy needs. Upon analyzing approximately 7,500 surface stations and another 500 balloon-launch stations, Archer and Jacobson (2005) estimate that wind can generate more than enough power to satisfy the world's energy demand. More than 13% of all reporting stations experience annual mean wind speeds greater than the 6.9 meters per second (m/s) at a height of 80 m, which is considered economically feasible to generate electricity. They find that northern Europe (along the North Sea), the southern tip of the South American continent, the island of Tasmania in Australia, the Great Lakes region, and the northeastern and northwestern coasts of North America have the strongest wind power potentials. If turbines were set up in all the regions with wind speeds greater then 6.9 m/s, they would generate 72 TW of electricity, which is almost five times the world's current energy use. However, it is not possible to set up turbines in every region identified due to existing buildings, land rights and other obstacles. Nevertheless, even 20% of those sites could satisfy current world energy consumption. A study initiated by the United Nations' Environment Program (UNEP) to evaluate wind power potential in 19 African countries estimates that the wind power potential could reach 53 TW in those countries alone (InWEnt Consulting, 2004). As a result of concerns about climate change and higher prices of fossil fuels, wind power has a strong potential for continued rapid deployment. A 2006 joint study by the Global Wind Energy Council (GWEC) and Greenpeace International (2006) estimates that wind energy can make a major contribution to global electricity supply within the next 30 years (see Table 2). The study shows that wind energy could supply 5% of the world's electricity by 2030 and 6.6% by 2050 under the reference wind power scenario. The contribution would range from 15.6% in 2030 to 17.7% by 2050 under the moderate scenario. Wind energy's contribution to world electricity demand would range from 29.1% in 2030 up to 34.2% by 2050 under the advanced scenario. GWEC and Greenpeace International (2006) projections of installed capacity, electricity output and the contribution of wind power to global electricity supply by 2030 and 2050 are provided in Table 2. [6].
This promising projected future growth of wind power is supported by the future energy strategy of many countries. For example, the current energy strategy of Germany provides substantial scope for renewable energy generation growth. The projected energy mix of Germany on 2020 with 47% of the total electricity obtained from renewable sources and wind being the largest contributor with19% generation. The projected renewable energy power production will triple within 2020 and will maintain an impressive annual growth of 9%. Most importantly, no additional fossil fuel power plants will be needed in Germany (except those whose construction started before 2008) to guarantee energy security of Germany [7].
Fig. 3. Projected energy mix of Germany on 2020 with 47% of the total electricity obtained from renewable sources and wind being the largest contributor (19%.) [6].
Challenges of Wind Power Generation Growth
Wind power is starting to play an increasingly important role in supplying clean energy throughout the whole world, since much of our world's green power generation is derived from wind. Although market research shows that many consumers will purchase renewable power even if it costs somewhat more than conventional power, future growth of the industry will be shaped by different technical, economical, policy related and environmental challenges which prevents residential customers, small and large businesses, industries, and utilities from investing in them [8]. These challenges are discussed bellow:
A. Technical challenges
Grid limitation: According to [9] the biggest limitations of wind power is not in the generating technology, but rather in the antiquated power grid of most part of the world, which cannot automatically reroute power from one region to another as demand and supply rise and fall. That makes it difficult to take full advantage of wind power, whose output vacillates according to the weather.
Problem related to high penetration level: High penetration of intermittent wind power (greater than 20% of generation meeting load) in the system faces fundamental technical and financial constraints with regards to the connection of wind farms to the electrical network. In that situation, the main challenge is network stability.
Line overloading: While integrating the wind power to the existing grid is has to be ensured that the interconnecting transmission or distribution lines will not be over-loaded. This is important to ensure that the introduction of additional generation will not overload the thermal limit of the lines and other electrical equipment. Both active and reactive power requirements should be investigated. Reactive power should be generated not only at the interconnection point (PCC), but also throughout the network, and should be compensated locally, i.e., by the wind power generators.
Fault current recalculation: It is very important to determine the impact of additional generation sources to the short circuit current ratings of existing electrical equipment on the network. Because, in some cases the additional wind generation unit integration may cause the short circuit breakers ineffective during the fault.
Modified transient stability: Dynamic behaviour of the system during contingencies, sudden load changes and disturbances gets significantly modified with additional wind generating source. In most cases, fast-acting reactive-power compensation equipment, including SVCs and STATCOMs, has to be included for improving the transient stability of the network which.
Electromagnetic transients: Wind power integration requires ensuring fast operational switching transients have a detailed representation of the connected equipment, wind turbines, their controls and protections, the converters, and DC links.
Impact on network protection devices: The stand alone operation or grid connected operation of the wind power generation unit presents significant challenge to the network protection system as most of the current switches, breakers and relays are not designed to handle bidirectional power flow and modifies current profile during fault. So, stand alone operation or grid connected operation of wind power generation requires investigation on how unintentional islanding and reverse power flow may have a large impact on existing protection schemes, philosophy, and settings. Based on that investigation result, the network protection scheme should be modified to avoid any system failure and accident [16].
Power levelling and energy balancing: Due to the fluctuating and uncontrollable nature of wind power as well as the uncorrelated generation from wind and load, wind power generation has to be balanced with other fast controllable generation sources. These include gas, hydro, or renewable power generating sources, as well as short and long-term energy storage, to smooth out fluctuating power from wind generators and increase the overall reliability and efficiency of the system. The costs associated with capital, operations, maintenance and generator stop-start cycles have to be taken into account as well [10].
Power Quality: Fluctuations in the wind power and the associated power transport (AC or DC), have direct consequences to the power quality. As a result, large voltage fluctuations may result in voltage variations outside the regulation limits, as well as violations on flicker and other power quality standards [15].
Problem related to increased rating: In wind power's early days, 750 kW was the industry's standard output for a single turbine. Now most new wind turbines crank out more than twice that amount of juice, around 2 MW. It's essential to increase the output of a wind turbine to make it more cost effective and to increase efficiency. But the turbines with very high output still needs further research on turbine technology, material cost reduction and increasing efficiency.
Limited transmission capacity: Transmission capacity and access are becoming major obstacles to the development of wind power resources. Often the best resources for wind farms are in remote locations, distant from power grids and far from cities where electricity is heavily used. So the development of wind farms often requires the need for new or expanded transmission facilities[17].
Transmission scheduling difficulties: Transmission scheduling difficulties for wind power can result because the original rules for access to transmission capacity were not designed with intermittent sources, like wind, in mind. As the electricity sector slowly transforms itself from one with several hundred vertically integrated utilities with their own transmission control areas to one with a combination of regional transmission organizations (RTOs) and traditional control centers, the rules are being rewritten. Under the old rules, economic penalties were applied to generators that did not meet their day-ahead schedule requirements. For wind power, this occurred frequently since power output varies with wind variability, making scheduling difficult. Wind developers claim that the old rules discriminated against intermittent sources.
Variable nature of wind power: Wind power is a variable resource, providing electricity only when the winds are blowing. Wind speeds vary by the time of day, season and even from one year to the next. This variable nature means that wind power is not a solution to all our energy needs and must only play a supporting role in a larger electricity network.
Limited wind resource assessment data: Project developers need more information about a particular region's wind resources in order to minimize risk and choose the best sites. But most part of the world has very limited wind resource assessment data due to the underfunded research and opportunity. In this situation a detailed assessment of wind resources throughout the whole world should be carried out and international assistance is likely needed to accelerate these activities.
Immature local manufacturing capability: Although some countries of the world are strongly promoting local manufacturing capability for wind turbines, most of the countries are still lagging behind. If a country has to reduce the cost of the wind generation units then the local manufacturing capability has to be increased. Also markets for these turbines must be increased in order to lower costs by providing greater economies of scale. Special market driver policy should help in expanding markets and reducing costs.
Radar Issues: Wind turbines can interfere with civilian and military radar at some locations. The potential interference occurs when wind turbines reflect radar waves and cause ghosting (false readings) or shadowing (dead zones) on receiving monitors. Radar interference thus raises national security and safety concerns [11].
B. Economical challenges
Returns on Investment: Comparatively higher capital cost (per installed kilowatt) is the main challenge for clean energy to grow. In spite of all the benefits smaller and distributed clean systems can offer, their comparatively higher initial capital cost make them too risky for most utilities and businesses. This is particularly true for two of the most common distributed clean technologies: wind and solar power.
Cost competitiveness: Wind energy is increasingly cost-competitive with conventional generating technologies. Greater efficiencies (from larger turbines) and improved technology continue to drive cost down. Wind energy can be installed on a modular basis and has no fuel cost. And, as environmental costs are increasingly factored into the costs of conventional generating technologies, the cost of wind energy becomes less and less of an obstacle to deployment. But still the initial cost of installing a wing power generation unit is much high. To support the growth of wind energy generation throughout the whole world, this cost should be further reduced.
Lack of high competition: Although the wind power generation is seeing tremendous growth over the past few years but still the market competition is not very high. But pressure from market competition is needed to trim costs and improve efficiency.
High price of power generated from wind: The lack of systemic management of the wind power distribution on network leads to the high price of the wind power. Detailed regulations have not been set up for several sensitive issues, such as the apportionment of price difference and tax subsidy. Therefore the wind electric power can only be utilized in the local areas where it is produced. Sometimes large wind farms are located in an area where the economy is underdeveloped. The use of the power is less than the average level. So the plants usually cannot run completely. This type of situation restricts the development of wind power and results in high price of power generated from wind.
Lack of low cost local wind power units: The manufacturing technology of wind power units is a significant factor to reflect the expanding level of wind power industry in a country [12]. The high initial investment costs are mostly caused by the imports of the most wind turbines that installed in a country's wind power plants. Compared with some advanced countries such as Denmark, Germany, etc., the installation cost in wind power plants of some other countries are comparatively higher. It has been estimated that local production of wind turbines can reduce costs by 20% [13]. In many countries of the world, in-network type of large wind power unit has not entered into market too long ago. Presently, very few countries have mastered the basic manufacturing technology of high rating units and can produce the main components and parts independently. Most of the countries import the key components from abroad. This increases the cost significantly. As a result, until now the low rate of localized manufacture of wind power units is a choke point in most of part of the world.
The problems on financing of wind power projects: There are not many fully commercialized wind power projects in the whole world. Most soft loans and domestic government programmes have a domestic bank loan component, which require payback periods of few years. The stress on the return of loans increases the cost of wind power generation indirectly [14]. Also, for many commercial loan organizations, there is a higher risk existing in the exploitation of novel energy resources. Therefore the loans provided are usually short-term with higher interest rates, which put the wind power in an inferior position compared with conventional power. Lack of long-term loans is a great disadvantage for many less competent wind power development corporations. Compounding these problems, very few commercial alternatives exist outside these conventional financing schemes. This is exacerbated by the lack of commercial domestic project developers, which contributes to high transaction costs for each wind power project.
Predatory Market Power: The addition of wind power sources straightforwardly threatens the market share of utilities, energy companies and other power operators. Usually utilities are by nature monopolistic entities that had almost total control over the generation, transmission and distribution of electricity with little accountability for cost. As addition of wind energy sources create potential scenario where they might lose the market control, so the wind energy growth faces a strong challenge from them.
C. Policy barriers
Need of incentives: In the last two decades, improvements in wind turbine design and technology have reduced the costs of wind power by more than half. Still, the growth of wind power in most part of the world remained limited. This is due, in large part, to the presence of abundant, low-cost, competing sources of conventional electricity supply in the country. Wind power developers argue that new government economic incentives and policies are needed to "level the playing field" and help wind power to compete with other fuel sources in the electricity market. They say that increased government incentives are needed to encourage the development of significant amounts of wind power.
Difficulty in securing project approval and negotiating power purchase agreements: Getting project approval from the central government and negotiating power purchase agreements with the local utility may be the most difficult task for wind power developers around the globe. These problems are not unique to the wind power field, and should become less burdensome as overall transparency in the policy making improves. Accession to the World Trade Organization (WTO) should further accelerate the development of a market-based economy driven by rule-of-law.
Lack of government policy in developing countries: In the developing countries with the limited financial resources, the governments are not able to give assistance on wind power cosmically, just like in the developed countries. In this situation, the government should establish certain policies for wind power generation. And the local government should give assistance on wind power by assessing the local conditions [12]. The other important aspect is the support from financial credits. From the course of the wind power development, the large scale projects should be encouraged.
Lack of concession bidding system: The problem in the development of wind power generation is how to reduce the cost of the construction and the price of wind power. In order to solve the problem, a competitive system should be established and wind power generation should be commercialized. In this situation, the concession bidding of wind power can be very effective. Such mechanism introduces new financing system and strong competition of investors at home and abroad to reduce project cost, enhance the construction, operation and management level, and effectively lower the price of wind power. Concessionary bidding in some countries can acts as a successful role model in the wind power exploitation and development to the rest of the world. As this type of bidding will attract and motivate capital investors, including many private investors; so It can also diversify the sources of investment, introduce more competition and disrupt monopoly. It is foreseeable that the wind power development will gradually go on a more rational and healthy track.
Inconsistent incentives: Many government policies encourage wind power technologies by subsidies and incentives. Wind energy being a very sensitive issue with different interest groups, the incentives and subsidies in this sector were very inconsistent during different political government in different countries. This was a great obstacle for any long term growth plan of clean energy.
Varying standards: In spite of the huge progress individual countries have made to promote wind power, contributions from individual countries remained constrained by the design and variation of their differing statutes. These country wise inconsistencies clogged the growth of wind energy. As a result, implementing agencies and stakeholders grapple with inconsistent goals.
Under funded R&D: There is a general trend of investing on wind energy source addition and installation. But both the public and private sectors continue to underfund R&D on wind power technologies, especially compared to conventional systems. The government is focused on researching other areas. Small firms usually do not conduct R&D programs because they are more risk averse and have fewer resources. On the other hand, large firms are reluctant to undertake R&D because they are more focused on short-term gains and dealing with competitors.
Imperfect policy to reduce cost of wind power: Generation cost and utility purchase price of wind power are considered as two key points that influence the development of wind power. But in most of countries, there are still no detailed policies to reduce the price of the wind power. The government pricing policy should assure that wind power plant developers will be able to sell wind power at a high tariff, so that their sale's income of wind power will cover not only all costs of wind power plant construction but also the repayment of loan and interest. A certain amount of profits could even be acquired from the beginning of wind power plant operation. High price of wind power can be effective to guarantee the payback of investment.
D. Environmental concerns
Land use issues: Wind turbines are tall structures which ideally need to operate in an exposed site where they can make best use of the prevailing wind. This means they are likely to be visible over a relatively wide area. Whether this has a detrimental effect is highly subjective. Being visible is not the same as being intrusive. While some people express concern about the effect wind turbines have on the beauty of our landscape, others see them as elegant and graceful, symbols of a better, less polluted future. The landscape is largely human-made and has evolved over time. Changes to the visual appearance of the countryside, such as roads or lines of electricity pylons, which were once considered intrusions, are now largely accepted as part of the view. Wind turbines can be removed easily when decommissioned, and the landscape returned to its previous condition. Nevertheless, most countries have established rules which exclude certain areas, such as national parks or nature reserves, from development. Others have identified priority areas where wind power is specifically encouraged through strategic planning guidelines [19].
Sound: the sound emission of wind turbines can be subdivided into mechanical and aerodynamic sound. Better design and better insulation have made more recent wind turbine models much quieter than their predecessors. Mechanical noise from the gearbox and generator has been virtually eliminated, leaving the turning blades as the main sound source. Changes in blade design and operation can reduce this. Compared to road traffic, trains, construction activities and many other sources of industrial noise, however, the sound generated by wind turbines in operation is low [19].
Birds: Birds can be affected by wind energy development through loss of habitat, disturbance to their breeding and foraging areas and by collisions caused by the rotating turbine blades. Compared to other causes of mortality among birds, however, the effect of wind power is relatively minor [19].
Conclusion
This report presents a brief overview of the wind energy systems with a focus on the challenges faced by it. The current scenario of wind energy generation and its possible future scopes are also depicted. Some major technical, financial, political and environmental challenges in wind energy are identified and discussed.
