Today we are facing huge challenges as the global warming, exhausting fossil energy resources, population growth and increasing energy demand. These aspects contribute to the urgent need to transform the energy generation and consumption based on fossil fuels to the energy systems consist of renewable energies and energy efficient technologies. One of the key solutions to the current challenges facing the world's energy future is renewable energy and it offers a smart solution to the increasing global energy demand and global warming.
The IEA (2006e) defines renewable energy as energy derived from natural processes that are replenished constantly. This definition applies to a wide range of energy sources derived directly or indirectly from the sun including solar, hydro, wind, wave and, but also includes non-solar sources such as geothermal, tidal and ocean currents. Renewable energies can meet the demand for electricity, satisfy heating and cooling needs and provide propulsion for vehicles without harming the environment. The following figure shows an overview of the renewable energies:
(from: Renewable Energies - Innovations for a Sustainable Energy Future, Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), June 2009, 7th Print)
The renewable energy sector is growing strongly and steadily. By early 2010, more than 100 countries had some type of policy target and/or promotion policy related to renewable energy (See also: International Energy Agency (IEA); [http://www.iea.org/textbase/pm/?mode=re|http://www.iea.org/textbase/pm/?mode=re]). Wind power and solar photovoltaic additions reached a record high during 2009 renewables accounted for over half of newly installed power capacity in 2009. For the second year in a row, more money was invested in new renewable energy capacity than in new fossil fuel capacity. The following table shows selected indicators (Renewables 2010; Global Status Report; Renewable Energy Network for the 21th century).
SELECTED INDICATORS 2007 2008 2009
Investment in new renewable capacity [billion $ / a] 104 130 150
Renewables power capacity (including only small hydro) [GW] 210 250 305
Renewables power capacity (including all hydro) [GW] 1,085 1,150 1,230
Hydropower capacity (existing, all sizes) [GW] 920 950 980
Wind power capacity (existing) [GW] 94 121 159
Solar photovoltaic capacity, grid-connected (existing) [GW] 7.6 13.5 21
Solar photovoltaic production [GW / a] 3.7 6.9 10.7
Solar hot water capacity (existing) [GWth] 125 149 180
Ethanol production [billion liters / a] 53 69 76
Biodiesel production [billion liters / a] 10 15 17
Countries with policy targets 68 75 85
States/provinces/countries with feed-in policies 51 64 75
States/provinces/countries with RPS policies 50 55 56
States/provinces/countries with biofuels mandates 53 55 65
Existing renewable power capacity worldwide reached an estimated 1,230 GW in 2009 (7 percent increase over 2008). The share of renewable energies in total energy production today is about a quarter of global energy production (estimated 4800 GW in 2009) and supplies about 18 percent of global electricity production (See Figure" Share of Global Electricity from Renewable Energy, 2008").
Share of Global Electricity from Renewable Energy, 2008 (Renewables 2010; Global Status Report; Renewable Energy Network for the 21th century)
When large-scale hydropower is not included, renewables provides more than 300 GW (22-percent increase over 2008) (See Figure "Renewable Power Capacities"). Especially, capacity of wind energy production facilities increased the most in 2009, by 38 GW. Hydropower has been growing year on year by about 30 GW in recent years, and solar photovoltaic capacity increased by more than 7 GW in 2009 (Renewables 2010; Global Status Report; Renewable Energy Network for the 21th century).
Renewable Power Capacities: Developing World, EU and Top Six Countries, 2009
The renewable energies for heating and cooling, biomass, solar, and geothermal energy currently supply hot water and space heating as well as cooling for millions of buildings worldwide. Solar hot water collectors alone are used by more than 70 million households worldwide as well as by many schools, hospitals, government, and commercial buildings. There is also a growing trend to use renewable heating for process heat in industry. Biomass and geothermal energy supply heat for industry, homes, and agriculture, and interest in the use of solar energy for cooling purposes is increasing.
The transport sector uses ethanol, made primarily from corn and sugar cane, and biodiesel, manufactured from vegetable oils, as renewable energies. Corn is the main resource to produce ethanol, i.e. more than half of global ethanol production. Sugar cane has a share of roughly one third of the production. Biogas is also being used in very limited quantities for transportation (e.g. in Sweden) as fuel for trains, buses, and other vehicles.
The sun transmits an enormous amount of radiant energy into the solar system continuously. The Earth receives a very small fraction of this energy; still, an average of about 1370 W per square meter of the surface of the Earth's atmosphere, which absorbs and reflects some of this radiation and allows the transmission of sunshine on the earth. The radiation reaches the ground has energy greater than the total amount of energy consume of the world's human population and can be used to produce electricity or as thermal energy.
Solar energy is reckoned a renewable energy originated from the sun, the world's primary source of energy. The sun's rays can be harnessed by solar power systems for heat or electricity as a high temperature and clean energy source. In contrast with the other energy sources, solar energy is regarded as being practically unlimited.
Solar energy can be applied in many ways, including:
- Solar photovoltaic systems
- Concentrating solar power systems
- Solar thermal systems
Solar photovoltaic systems
The common way of obtaining solar power contains the use of photovoltaic applications, i.e. photovoltaic cells, in converting energy from the sun into electricity. Photovoltaic cells consist of semiconductors to convert energy from the sun directly into electricity. The converted solar energy can be used instantly by the electric devices or fed in electricity grids or stored by batteries or other storage mediums.
When sunlight with certain wavelengths or energy is absorbed by solar cells made of semiconducting materials, the radiation knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electric current. This process of converting light (photons) to electricity (voltage) is called the photovoltaic effect.
The solar cell is the basic unit of a solar module or array. A photovoltaic system consists of modules or arrays and a "balance of system" (BOS) encompasses other required components of a photovoltaic system. This includes wiring, switches, support racks, an inverter, and batteries in the case of off-grid systems.
The main part of a solar cell is the semiconductor layer, where the electron current will be created. In addition to the semiconducting materials, a solar cell consists of conducting materials to transfer electrons to the external load and to complete the electrical circuit. The complete cell is sealed by a transparent, waterproof housing, which will be coated with non-reflective materials to minimize the reflection of the incident light and thus to increase the efficiency of the cell.
There are a number of different materials suitable for making the semiconducting layers, and everyone has benefits and disadvantages. The commonly used semiconducting layers are made of silicon, gallium arsenide or polycrystalline thin films.
Silicon is still the most popular solar cell material for commercial applications because it is so readily abundant. However, to be useful in solar cells, it must be refined to 99.9999% purity.
Gallium arsenide (GaAs) is a compound semiconductor, i.e. a mixture of two elements, gallium (Ga) and arsenic (As). Gallium is a byproduct of the manufacturing of other metals, particularly aluminum and zinc, and it is rare. Arsenic is not rare, but it is poisonous.
Polycrystalline thin film cells comprise many tiny crystalline grains of semiconductor materials and require very little semiconductor material and are easy to manufacture.
An individual PV cell typically produces between 1 and 2 watts. The produced power can be increased by connecting cells together to construct modules or arrays, which can be interconnected for more power. Because of the high modularity of the photovoltaic systems, it is quite easy to add photovoltaic units to an existing system for further demands.
The thin-film materials like amorphous silicon and cadmium telluride can be made directly into modules, effectively bypassing the solar cell. PV modules, because of their electrical properties, produce direct rather than alternating current. With suitable electronics, photovoltaic systems can be grid-connected or stand-alone. A storage battery is normally optional for grid-connected systems, but is a necessity for stand-alone systems that need independence.
Some solar cells are designed to operate with concentrated sunlight (concentrating photovoltaics CVP) for the purpose of electrical power production. These cells are built into concentrating collectors that use a lens to focus the sunlight onto the cells. The main idea is to use very little of the expensive semiconducting PV material while collecting as much sunlight as possible. Some concentrating collectors are designed to be mounted on simple tracking devices, but most require sophisticated tracking devices to increase photovoltaic efficiency.
Solar Photovoltaic, Existing World Capacity, 1995-2009 (Renewables 2010; Global Status Report; Renewable Energy Network for the 21th century)
Solar Photovoltaic Existing Capacity, Top Six Countries 2009 (Renewables 2010; Global Status Report; Renewable Energy Network for the 21th century)
Concentrating solar power systems
Concentrating Solar Power (CSP) systems use the sun radiation as a heat source by applying of lenses or mirrors and tracking systems to transmit the solar energy to a heating medium and to operate a conventional power plant. The notable types of concentrating solar power systems are parabolic-trough, central receiver/power tower, and parabolic dish.
Parabolic-trough systems concentrate the sun's energy by means of parabolic mirrors. The mirrors are tilted toward the sun, focusing sunlight on a receiver positioned along the focal line of the mirror to heat the working fluid of a heat exchanger in order to produce electricity in a conventional steam generator.
Another concentrating solar power technique applies many flat mirrors in a Fresnel arrangement, focusing sunlight on two tubes with working fluid. This system is much cheaper than parabolic mirrors, and allows more mirrors in the same amount of space to use more of the available sunlight. Nevertheless, parabolic trough systems provide the best land-use factor of any solar technology.
Central Receiver or tower power plants involve many hundreds of mirrors following the sun's path and concentrating its rays onto a receiver at the top of a tower. There the heat exchange medium (air, water, salt) is heated to 500 - 1 000 °C to generate electricity through a conventional steam generator.
Solar chimneys or green towers consist of a large greenhouse that funnels into a central tower or chimney. As sunlight shines on the greenhouse, the air inside is heated, and expands. The expanding air flows toward the central tower, driving a wind turbine to generate electricity.
The parabolic dish or Stirling solar dish combines a parabolic concentrating dish with a Stirling heat engine. The solar energy causes the fluid to expand in the engine to produce mechanical power and run a generator to produce electricity. The advantages of Stirling solar over photovoltaic cells are higher efficiency of converting sunlight into electricity and longer lifetime.
Comparison of Solar Thermal Power Technologies (European Solar Thermal Power Industry Association (ESTIA), Greenpeace International, Solar Thermal Power Plants, ISBN: 90-73361-82-6)
The Greenpeace International and the European Solar Thermal Power Industry Association (ESTIA) published a study about the potential and prospect of concentrating solar power (See Figure Comparison of Solar Thermal Power Technologies) and found that concentrating solar power could account for up to 5% of the world's energy needs by 2040.
Solar thermal systems
Solar thermal applications collect the sun's energy to heat air or liquid directly thus can be used for a wide range of applications including domestic hot water, heating in buildings and industrial processes as well as solar cooling. A solar thermal system consists of a collector, a water storage tank, and in some cases a circulation pump.
The collector is made of a thin, flat box with a transparent cover with a flat solar black absorber or a vacuum glass cylinder and metal pipes contain a heat transfer fluid, water or more often a fluid containing anti-freeze and a corrosion inhibitor.
The collected heat can be stored in a hot water storage tank. Systems that use fluids other than water usually heat the water by heat exchanger.
Solar water heating systems can be either active or passive, but the most common are active systems. Active systems use pumps to move the liquid between the collector and the storage tank in contrary to passive systems that use only the flow of the heated water.
Solar thermal installations for domestic use at large a supplementary energy source, i.e. central heating system or electric heating element, which is activated when the water in the tank falls below a minimum temperature setting.
In many climates, a solar thermal system provide up to 85% of domestic hot water energy. In many northern European countries, combined hot water and space heating systems are used to save 15 to 25% of home heating energy.
Solar Hot Water / Heating Existing Capacity, Top Ten Countries / Regions, 2008 (Renewables 2010; Global Status Report; Renewable Energy Network for the 21th century)
Solar Hot Water / Heating Existing Capacity Added, Top Ten Countries / Regions, 2008 (Renewables 2010; Global Status Report; Renewable Energy Network for the 21th century)
The solar thermal collectors can be applied for the active solar cooling using thermally driven cooling systems, either with absorption or desiccant technologies.
Solar absorption systems operate essentially similar to a fridge using thermal energy harnessed by a solar collector to separate a mixture with an absorbent (e.g. lithium bromide salt) and coolant (e.g. water, vapor). The coolant is then condensed and eventually evaporated to produce a cooling effect throughout the space. The evaporated coolant is then reabsorbed to continue the cycle.
Efficient absorption coolants require water of at least 90 °C. The evacuated-tube solar collectors and the flat plate solar collectors, which designed for these temperatures, are suitable for the solar cooling systems.
Solar desiccant technologies use solar thermal energy to regenerate desiccants (e.g. silica gel, calcium sulfate) by absorbing the air humidity to cool it. The thermal energy from the solar collectors is used to dry the desiccant, driving off the absorbed water. Desiccant systems can work at relatively low temperatures which gives them an advantage over absorption systems.
The thermally activated solar air conditioning is utilized only in some big facilities. Further research and development is needed in order to use solar power to cool homes and offices in more efficient, low-cost ways.
Solar energy systems -trends
The PV market has continued to grow by almost 15% in 2009 compared to 2008 and the total power installed in the World raised by 45% up to 22.9 GW. Europe is leading the way with almost 16 GW of installed capacity in 2009, representing about 70% of the World cumulative PV power installed at the end of 2009 (European Photovoltaic Industry Association , Global market outlook for photovoltaics until 2014).
Global solar thermal power capacity increased more than 70 percent between 2005 and the end of 2009, from 354 MW to about 610 MW, and had nearly doubled by March 2010 to 662 MW (Renewables 2010; Global Status Report; Renewable Energy Network for the 21th century).
In 2009, existing solar water and space heating capacity increased by an estimated 21 percent to reach about 180 GWth globally, excluding unglazed swimming pool heating. The European Union accounted for most of the remaining global added capacity, installing an estimated 2.9 GWth in 2009 (Renewables 2010; Global Status Report; Renewable Energy Network for the 21th century).The market for solar thermal performed better than expected and for the second year in a row, over 4 million square meters of solar panels were installed in Europe. Over the last three years the market for solar cooling has increased by 40 to 70% per annum. In 2009, a total of 450 solar cooling systems were installed worldwide (European Solar Thermal Industry Federation (ESTIF), Solar Thermal Markets in Europe Trends and Market Statistics 2009).
Europe continues the further development of the solar power systems with the European Industrial Initiative according to the Strategic Energy Technology Plan aims to increase, coordinate, and focus EU support on key low-carbon energy technologies, such as solar energy (photovoltaic energy and concentrating solar power, published first by the European Commission in November 2007 (Brussels, 22.11.2007, COM(2007) 723 final, Communication from the Commission, to the Council the European Parliament, the European Economic and Social Committee and the Committee of the Regions, A European Strategic Energy Technology Plan (SET-PLAN) - Towards a low carbon future).
The European solar Initiative focuses on photovoltaics (PV) and concentrating solar power (CSP) technologies. The objective of the PV component of the Initiative is to improve the competitiveness of the PV technology and to facilitate its large scale penetration in urban areas and green field locations, as well as its integration into the electricity grid. These measures should establish PV as a competitive and sustainable energy technology contributing up to 12% of European electricity demand by 2020 For the CSP component, the objective is to demonstrate the competitiveness and readiness for mass deployment of advanced CSP plants, through scaling-up of the most promising technologies to pre-commercial or commercial level in order to contribute to around 3% of European electricity supply by 2020 with a potential of at least 10% by 2030 if the DESERTEC (solar technology, mainly CSP, in Middle East and North Africa countries and export of electricity to Europe.)vision is achieved (Commission staff working document - Accompanying document to the Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions on Investing in the Development of Low Carbon Technologies (SET-Plan) - A technology roadmap (SEC/2009/1295 final)
This Commission staff working document presents the solar energy roadmap, officially presented and discussed at the Strategic Energy Technology Plan (SET-Plan) workshop, held in Sweden in the same publishing month. The roadmap is a key instrument for the development of European solar energy in the 2010 - 2020 period and will play an important role in climate protection and in fostering the EU Member States to meet the 2020 targets identified by the RES Directive (Directive 2009/28/EC of the European Parliament and of the Council of 23 April 2009 on the promotion of the use of energy from renewable sources and amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC
European industrial initiative on solar energy – photovoltaic energy aims to improve the competitiveness and ensure the sustainability of the technology and to facilitate its large-scale penetration in urban areas and as free-field production units, as well as its integration into the electricity grid.
The photovoltaic energy roadmap 2010-2020 has the following key areas (see the next picture):
- PV Systems to enhance the energy yield and reduce costs
- Integration of PV-generated electricity
European industrial initiative on solar energy – concentrating solar power aims To demonstrate the competitiveness and readiness for mass deployment of advanced concentrating solar power (CSP) plants, through scaling-up of the most promising technologies to pre-commercial or commercial level.
The concentrating solar power roadmap 2010-2020 has the following key areas (see the next picture):
- Reduction of generation, operation and maintenance costs
- Improvement of operational flexibility and energy dispatchability
- Improvement in the environmental and water-use footprint
- Advanced concepts & designs
A wind energy system transforms the kinetic energy of the wind into rotational energy, which in turn is converted to electricity. Wind energy is one of the most promising renewable energy sources, although the wind is an intermittent energy source, and not all the time available.
There are global winds related to large scale solar heating of different regions of the earth's surface and seasonal variations in solar incidence. There are also localized winds due the effects of temperature differences between land and seas, or mountains and valleys. On the other hand, wind speed usually increases with height above ground, since the wind sped might be reduced by roughness of ground topographies such as hills and vegetation. The alternating availability of wind energy however no particular trouble for network operation, especially since this represents only a small proportion of total energy demand.
The wind power is proportional to the
- area swept by rotors,
- cube of the wind speed,
- air density.
The fact that the wind power is proportional to the cube of wind speed is of great importance i.e. the doubling of wind speed means an eightfold of wind power.
The actual power also will depend on several technical factors mainly on the construction of the windmill system. There are also physical limits to the power efficiency of the windmill systems and this is 59.3% of energy from the wind (Betz limit). The modern wind energy systems provide an efficiency degree almost 45%.by extracting of energy from the wind, transferring the momentum of passing air to rotor blades. The rotors of most wind turbines face into the wind and move to follow changes in wind direction. Energy is concentrated into a rotating shaft and converted into electricity.
There are a wide range of wind power turbine technologies available, from small through to large commercial wind turbines. Wind turbines can also be classified by the orientation of the axis of rotation to the direction of the wind – horizontal axis machines and vertical axis machines. The horizontal axis wind turbines are by far the most common.
The basic components of a typical wind energy system are
- a rotor, or blades, which convert the wind's energy into rotational shaft energy;
- a enclosure, or nacelle containing a drive train, usually including a gearbox and a generator;
- a tower, to support the rotor and drive train, and
- balance of system components (electronic equipment such as controls, electrical cables, ground support equipment, and interconnection equipment).
Wind turbine classed by the orientation (http://www.windenergy.org.vn/index.php?mact=Uploads,m7,getfile,1&m7upload_id=69&m7returnid=89&page=89)
The wind energy systems called small-scale wind power with a capacity up to 50 kW are used to produce electricity for communities, individual homes and small businesses especially in remote locations.
The utilization of wind energy in the urban environment is based on small-scale vertical-axis wind turbines with rotor diameters of only several meters since vertical-axis wind turbines are, by design, insensitive to the wind direction. The turbines for remote area applications are generally are horizontal-axis turbines with tree blade rotors of a couple of meters in diameter and generate round 10 kW of power.
These wind turbines can be used directly on site as stand-alone applications (battery based) or combined with a photovoltaic system or they can be connected to an electricity grid.
The large-scale wind turbines (utility-scale wind turbines) are now available from 100 kW to 10 MW. The wind energy systems in kW-range generate individually on small farms or businesses, whereas the systems in MW-range are placed in on-shore or offshore wind farms. The most of the large-scale wind turbines constructed as a horizontal-axis turbine, which rotates into the wind. The amount of power a wind turbine can generate depends on the rating of the wind turbine and the wind regime in which it is to operate. The rating is the maximum amount of power the turbine can generate at a certain wind speed (typically 25 mph). The electricity generated by a large-scale wind turbine is usually fed into electricity grid, where it will be mixed with electricity from other power plants and delivered to final customers.
The capacity of large-scale wind turbines are increased almost exponential in the last thirty years, not least because of the growing size of the rotors. The following table illustrates the size of new 10-MW turbines with comparisons to previous generations of the large-scale turbines and the turbine's capacity as power rating.
Stages of the large-scale turbines
The wind farms utilize multiple large-scale wind turbines in the same location to produce electric power. The preferred locations are adequately windy and have largely constant winds, e.g. coastal areas or exposed high areas, like hills, or offshore. The main aspects of wind farm operations are maximizing electricity production whilst minimizing infrastructure, operation, maintenance costs and environmental impacts.
A wind farm consists of wind turbines, access tracks, underground cabling, connection network, a switchyard (electrical substation), control equipment and a connection to a grid system with a size from a few megawatts up to the gigawatts (in Taveljso, in the municipality of Piteå, with 1,101 wind turbines, total capacity 4 GW, ([http://www.sweden.gov.se/sb/d/12872/a/140909|http://www.sweden.gov.se/sb/d/12872/a/140909]).
The best places for on-shore wind farms are in coastal areas, yet a limited number of wind farms are located in mountainous areas. The main reasons are the reduced power density, unfavorable accessibility of mountainous areas and the limited infrastructure.
The next chart shows the existing world wind power capacity grew exponential over the last decade.
Wind Power, Existing World Capacity, 1996-2009 Renewables 2010; Global Status Report; Renewable Energy Network for the 21th century)
The worldwide capacity was reached in 2009 about 160,000 MW and will be exceeded presumably 200,000 MW in the year 2010. The added wind power capacity in the year 2009 amounted to about 38,000 MW, i.e. a growth rate of more than 30 %. Thus, wind turbines installed by the end of 2009 will be able to generate 340 TWh per year.
Wind Power, Existing World Capacity, Top 10 Countries, 2009 Renewables 2010; Global Status Report; Renewable Energy Network for the 21th century)
In the year 2009, altogether 82 countries used wind energy on a commercial basis, out of which 49 countries increased their installed capacity. Worldwide, 35 countries had wind farms with a capacity of 100 Megawatt or more installed, compared with 32 countries in the previous year and 24 countries four years ago. (World Wind Energy Report 2009, World Wind Energy Association WWEA 2010)The European Countries have a major share of the generation of wind power (see next chart)
Global cumulative wind energy capacity (1990-2008) (Pure Power, Wind energy targets for 2020 and 2030, A report by the European Wind Energy Association - 2009 update)
Global annual wind energy capacity (1990-2008) (Pure Power, Wind energy targets for 2020 and 2030, A report by the European Wind Energy Association - 2009 update)
Offshore wind capacity continued to grow in the year 2009. By the end of the year, wind farms installed in the sea could be found in twelve countries, ten of them in Europe and some minor installations in China and Japan. Total installed capacity amounted to almost two Gigawatt, 1,2 % of the total wind capacity worldwide.
Wind turbines with a capacity of 454 Megawatt were added in 2009, with major new offshore wind farms in Denmark, the United Kingdom, Germany, Sweden and China.
The growth rate of offshore wind is with 30 % slightly below the general growth rate of wind power. (World Wind Energy Report 2009, World Wind Energy Association WWEA 2010)
Annual and cumulative installed EU offshore wind capacity (1991-2008) (Pure Power, Wind energy targets for 2020 and 2030, A report by the European Wind Energy Association - 2009 update)
Offshore wind resources are characterized by higher load hours, as the offshore wind speeds are considerably higher than onshore due to less roughness of the surface. The designs for offshore turbines are based on the onshore power technology, with additional protection against sea salt incursion.
Offshore wind locations are generally considered to be ten kilometers or more from land. In most cases offshore systems are more expensive than onshore because of the additional costs, e.g. for foundations, power transmission through undersea cables, more technical equipment, maintenance and corrosion protection measures. Offshore wind turbines are on the other hand less noticeable than turbines on land, as their apparent size and noise are mitigated by distance.
Offshore wind capacity continued to grow in the year 2009. By the end of the year, wind farms installed in the sea could be found in twelve countries, ten of them in Europe and some minor installations in China and Japan. Total installed capacity amounted to almost two Gigawatt, 1,2 % of the total wind capacity worldwide.
New annual EU wind energy capacity (1991-2020) (Pure Power, Wind energy targets for 2020 and 2030, A report by the European Wind Energy Association - 2009 update)
Wind power production in the EU (2000-2020) (Pure Power, Wind energy targets for 2020 and 2030, A report by the European Wind Energy Association - 2009 update)
An essential element in establishing wind energy is to ensure that the electricity generated can feed into the grid system and reach electricity consumers.
The main components for the grid connection of a wind turbine are a transformer and a substation consists of a circuit breaker and an electricity meter. Turbines have each a transformer to the medium voltage line due to the high losses in low voltage lines. A separate substation for transformation from the medium voltage system to the high voltage system is for large wind farms required. The circuit breaker works as an interface between the wind turbine and the grid.
Because intermittency nature of wind power and instantaneous electrical generation and consumption must keep on in balance to maintain grid stability, this unpredictability can result substantial challenges to incorporating large amounts of wind power into a grid system. However, the practice shows that combining a various mix of energy supply allows large wind power penetration in an electricity grid without actual disadvantages, for the variability of the wind power causes not more complications for electricity grid management than the other energy sources. The large-scale integration of wind energy should be seen in the context that wind will provide a substantial share of future global electricity demand. While wind energy covered around 1 per cent of global electricity demand in 2008, it is estimated for 2020 and 2030 are for penetration levels of 3.6 per cent and 3.9 per cent respectively, depending on future electricity demand (Data analyzed from the global energy figures from the IEO2010 on the EIA Home Page [http://www.eia.gov/oiaf/ieo/index.html|http://www.eia.gov/oiaf/ieo/index.html] )
Wind power is renewable and produces no greenhouse gases during operation, such as carbon dioxide and methane. Compared to the environmental effects of traditional energy sources, the environmental effects of wind power are relatively minor. Factors that need to be considered in the early stages of a wind farm project are the visual impact, noise pollution and shadow flicker impact on local residents, the impact of construction and operation on protected areas and important or protected flora and fauna. The environmental constraints presented in annex 3 "Introduction to environmental and social constraints" of the EEA Technical report "Europe's onshore and offshore wind energy potential - An assessment of environmental and economic constraints" deals with the environmental impact of the wind energy and the international and European legal requirements. The annex discuss especially
- Impact of wind farms on biodiversity (collision risk, barrier effect, displacement, habitat loss or degradation),
- Impact of onshore and offshore wind farms on selected species groups (impact on birds, Impact on other species groups, bats, marine animals, other marine species and habitats),
- Identification and mapping of sensitive areas,
- Mitigation measures (wind farm configuration, minimizing disturbance, temporary shutdown, compensation).
Wind energy systems -trends
The wind energy systems trends include growth of the offshore wind energy systems and small-scale grid-connected turbines, and new wind projects in a much wider variety of geographical locations around the world and within countries. Firms continue to increase average turbine sizes and improve technologies, such as with gearless designs. In 2009, the global total wind power installations reached 38 GW (41 % increase over 2008), and the offshore wind power market with added about 640 MW of capacity in 2009, total 2 GW, grew 72 % compared to the previous year (Renewables 2010; Global Status Report; Renewable Energy Network for the 21th century). Europe as a global leader in terms of wind energy technology and one of the top markets for installations continues the further development of the wind power systems with the European Industrial Initiative according to the Strategic Energy Technology Plan aims to increase, coordinate, and focus EU support on key low-carbon energy technologies, such as wind power, published first by the European Commission in November 2007 (Brussels, 22.11.2007, COM(2007) 723 final, Communication from the Commission, to the Council the European Parliament, the European Economic and Social Committee and the Committee of the Regions, A European Strategic Energy Technology Plan (SET-PLAN) - Towards a low carbon future).
The European Wind Initiative aims to make wind energy more competitive, to harness the potential of offshore resources and deep waters, to facilitate grid integration of wind power, and to enable wind energy to take a 20% share of the final EU electricity consumption by 2020 (Commission staff working document - Accompanying document to the Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions on Investing in the Development of Low Carbon Technologies (SET-Plan) - A technology roadmap (SEC/2009/1295 final)
This Commission staff working document presents the wind energy roadmap, officially presented and discussed at the Strategic Energy Technology Plan (SET-Plan) workshop, held in Sweden in the same publishing month. The roadmap is a key instrument for the development of European wind power in the 2010 - 2020 period and will play an important role in climate protection and in fostering the EU Member States to meet the 2020 targets identified by the RES Directive (Directive 2009/28/EC of the European Parliament and of the Council of 23 April 2009 on the promotion of the use of energy from renewable sources and amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC), by achieving the following goals:
- A wind energy penetration level of 20% in 2020;
- Onshore wind power fully competitive in 2020;
- 50.000 new skilled jobs created in the EU by the wind energy sector in the 2010 – 2020 period.
The wind energy roadmap 2010-2020 has the following key areas (see the next picture):
- New turbines and components
- Offshore technology
- Grid integration
- Resource assessment and spatial planning