Notes Topic 1 - 1 INTRODUCTION TO WIND

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1 INTRODUCTION TO WIND ENERGY........................................................................................................1 1.1 What is wind energy..................................................................................................................................1 1.2 Why use wind energy ................................................................................................................................1 Why choose wind over conventional fuel sources .........................................................................1 1.2.2 Why choose wind over other renewable energy technologies............................................................1 1.3 The history and rise of wind energy ..........................................................................................................2 1.3.1 The first windmills were for mechanical power generation ...............................................................2 1.3.2 Electrical power generation ................................................................................................................3 1.4 Wind energy in Australia ..........................................................................................................................6 1.5 Wind energy in the future..........................................................................................................................7 1.5.1 Onshore wind energy ..........................................................................................................................7 1.5.2 Offshore wind energy..........................................................................................................................7 1.5.3 Remote area power systems ................................................................................................................8 1.3 The history and rise of wind energy A brief overview documenting changes in wind turbine application, design and size up to the present day is presented below: 1.3.1 The first windmills were for mechanical power generation The first windmills were mechanical devices used for grinding grain or pumping water. It is generally believed that the world’s first windmills were developed in Persia about 500-900 A.D. The first use was apparently water pumping, but the details of the design are not known. Figure 1-1 shows a replica of a documented Persian windmill with vertical sails attached to the vertical shaft by horizontal struts. Originally the vertical sails would have been made of bundles of reeds or wood. This is a grain-grinding windmill and a grinding stone would have been attached to the vertical shaft of the machine. Figure 1-1 Replica of an early windmill used for grinding grain 1 INTRODUCTION TO WIND ENERGY 1.1 What is wind energy Wind energy is the process of harnessing energy from the wind using a turbine. The wind produces a torque on the turbine rotor and the resulting mechanical energy can be used to e.g. pump water, or it can be converted by means of a generator to electrical energy. This course is mainly concerned with the latter application as an alternative to electricity generated by conventional power sources i.e. fossil-fuel sources. 1.2 Why use wind energy Why choose wind over conventional fuel sources 1. Wind energy is clean - it emits no pollutants. Using a 600kW wind turbine at an average location is equivalent to saving 1,200 tonnes of carbon dioxide that would otherwise be produced from e.g. a coal-fired power station. 2. Wind energy is abundant - the energy in the wind is a sustainable resource. The total available wind resource in the world today (that is technically recoverable) is about 4 times greater than the world's entire electricity consumption in 1998. 3. Wind energy is ideal for developing countries since it requires no expensive provision of fuel - a major problem for several other electricity-generating technologies in developing countries. 4. Wind energy is adaptable - it is a scaleable technology that can be used in a wide range of applications from small battery chargers in remote areas to multi-megawatt turbines arranged in wind farms and meeting the electricity needs of thousands. 1.2.2 Why choose wind over other renewable energy technologies 1. Wind energy is the most technologically advanced renewable energy technology – over the last 15 years, advances in aerodynamics, structural dynamics and meteorology have contributed to increasing the annual energy output from a wind turbine by a factor of 100. 2. Wind energy is the most cost-competitive renewable energy technology compared to conventional power sources. The energy cost per kWh of electricity from wind is the same as for new coal-fired power stations fitted with smoke-scrubbing equipment. 3. Wind energy uses land resources sparingly - to produce the same annual energy output as a 600kW wind turbine, solar cells would occupy 400 times the land area and a typical biofuel plant would occupy 40,000 times the area. 1-1 (Source: http://telosnet.com/wind/early.html) The first examples of horizontal-axis wind turbines (the common configuration of wind turbines today) had blades with sails and appeared in Persia, Tibet and China in the 11th Century AD. Influenced by the Crusaders, the horizontal-axis windmill spread from Persia across the Mediterranean countries and into central Europe. Between the 12th and 19th Century, windmill performance was constantly improved and was used for pumping water for drainage as well as grinding grain. In the 1800’s, the typical European –style ‘post-mill’ (see Figure 1-2) used a 25m diameter rotor and was so widespread that in the Netherlands, 90% of the power used in the industry was based on wind energy. In extreme wind speeds, the windmills had to be manually turned out of the wind or the sailing blades had to be rolled up, to avoid damage to the windmill. The age of industrialisation led to a gradual decline in windmills in Europe but settlers introduced the machines to North America and small machines became very popular on farm and homesteads for pumping water for cattle. The machines had self-regulating mechanisms that pointed the rotor into the wind during high winds. 1-2 Figure 1-2 Replica of an old 19th Century European-style ‘post-mill’ (Source: http://telosnet.com/wind/early.html) The large wind turbine technology pioneered by Brush and La Cour was largely ignored, though many small battery-charging wind turbines were used on remote homesteads in the USA, often as the only source of electricity (see Figure 1-4). These `Windchargers’ reached a peak during 1920 - 1930 with 600,000 machines installed but eventually declined in popularity with the advent of rural electrification. Power shortages during World War I and II revitalised interest in large wind turbine technology. The Danish company F.L. Smidth produced slow-speed, stall-regulated machines with upwind rotors in the range 50-70kW and the American Smith-Putnam machine was a 1.25MW machine with a downwind rotor and pitch regulation. The SmithPutnam machine in particular was not very successful and was dismantled in 1945. Figure 1-4 ‘Windchargers’ – small battery-charging machines used on remote homesteads (Source: http://telosnet.com/wind/early.html) 1.3.2 Electrical power generation It is generally agreed that the first wind turbine for electricity generation was built in 1887-1888 by Charles F. Brush of Brush Electric Co., Cleveland, Ohio (Brush Electric later merged with Edison General Electric to form General Electric). It was the largest wind turbine in the world at that time with a rotor diameter of 17 m and 144 blades constructed from cedar wood. Figure 1-3 shows a photo of the turbine – a man is mowing the lawn to the right of the turbine, highlighting the scale of the machine. The turbine ran for 20 years, charging batteries on Brush’s estate and powering 350 incandescent lights. Despite it’s size, the turbine only supplied 12kW of power due to the fact that low-speed, multi-blade rotors do not have a high efficiency. In 1891, Professor Poul LaCour of Denmark discovered that fast rotating wind turbines with a low number of rotor blades are more efficient and built a 4 bladed machine of rotor diameter 23m, rated at 18kW. Figure 1-3 The world’s first electricity producing wind turbine, built in 1887-88 (Source: http://www.wincharger.com/gallery/original/index.htm) After the war, interest in large-scale wind power declined. Two exceptions were a 200kW installed in Gedser, Denmark and a 100kW Hutter machine from Germany. Johannes Juul built the Gedser machine in 1956-57. Juul was a student of Poul LaCour’s and was a pioneer in developing the world’s first alternating current (AC) wind turbines. The Gedser machine was a 3-bladed, upwind, stall-controlled machine with an asynchronous generator and many of the medium-large wind turbines installed in the world today are based on this design. The Hutter machine was notable for having 2 slender fibreglass blades mounted downwind of the tower on a teetering hub. The oil-crisis in the 1973 renewed the interest in wind energy. Financial support was made available for research and development and many large-scale prototype machines were tested. Many of the machines were in the MW range but proved expensive and unsuccessful due to problems with e.g. pitch mechanisms. More successful were the smaller wind turbines (around 50kW) with the incorporation of the induction generator for direct-grid connection. A commercial failure in the USA, small wind turbines with induction generators gained in popularity in Europe in countries such as Denmark, Germany and the Netherlands. With special government support schemes, the utilization of wind energy took place. In Denmark in the mid1970’s political support enabled the manufacturing industry (and turbine sizes) to grow. In 1978, the US government introduced the Public Utility Regulatory Policies Act (PURPA), in an attempt to decrease it’s dependence on foreign oil. PURPA, together with special tax credits for renewable energy, led to the first wind energy boom in history. In the mountain regions of California huge wind farms were installed (see Figure 1-5) initially consisting of mainly 50kW machines. 1-3 1-4 Figure 1-5 Wind farm in San Gorgonio Pass powering Palm Springs in California standard product for many of the 40 wind turbine manufacturers worldwide. There are currently 17,000 MW of wind energy installed worldwide. For the latest figures regarding installed capacity of wind energy see http://www.awea.org. 1.4 Wind energy in Australia Australia currently has roughly 75MW of installed wind power. Most of this installed capacity is accounted for by fifteen installations of greater than 25kW. Roughly half of the fifteen installations are single turbine installations and half are groups of wind turbines in wind farms. Many of the wind farms are wind-diesel stations where the turbines are indirectly connected to an electricity grid. The first wind farm in Australia was a wind-diesel station at Salmon Beach, WA where six 60kW Westwind machines were installed in 1989. The Salmon Beach farm has now been decommissioned and currently the Exmouth mini wind farm is the only wind farm with Australian-made machines; the other wind farms have imported machines from Europe, mainly from Denmark and Germany. (Source: http://www.palmsprings.com/services/wind.html) Figure 1-7 The Albany wind farm featuring 1.8MW Enercon wind turbines By the end of the 1980’s, the typical wind turbine size increased to about 200kW. Most wind turbines were now imported from Denmark and, like the Gedser machine, were 3-bladed, upwind, stall-regulated turbines. This design philosophy became known as The Danish Concept. Figure 1-6 The rapid growth of wind energy during the 1990’s (Source: Courtesy of Western Power Corporation) The first wind farm with directly grid-connected turbines was commissioned at Crookwell in NSW in 1998. The farm has eight Danish Vestas machines each rated at 600kW. The largest wind farm in Australia is currently at Albany in WA where there are twelve German Enercon machines each rated at 1.8MW giving a total installed capacity of 21.6MW (see Figure 1-7). Some photos of the construction of the Albany wind farm can be viewed at: http://www.westernpower.com.au/html/home/environment/renewable_energy/renewable_wind.html - albanygallery (Source: http://www.earth-policy.org/Alerts/Alert14_data.htm) Toward the end of the 1980’s financial support for wind energy waned in the US but picked up in Europe (particularly Germany) and in India, during the 1990’s, due to government support schemes. This period earned wind energy the label of the fastest growing energy technology of the 1990’s with market growth rates of around 40-50%. In 1999, annual sales figures for the wind industry amounted to $4 billion US dollars. The technology has developed in parallel to the market, and a 1.5MW machine is rapidly becoming a 1-5 Larger wind farms are planned for Australia mostly in Victoria where Pacific Hydro Limited have plans for 5 wind farms with installed capacity up to 65MW. Overall, Pacific Hydro expects to install wind energy projects with a total capacity of at least 500 MW in Australia within the next three to four years. 1-6 1.5.1 Onshore wind energy The International Energy Agency predicts that the world’s electricity consumption will double by 2020. With growth rates of 20-30%, wind energy could be in a position to meet 10% of world demand in 2020. In Denmark, government plans are for 50% of their electricity demand to be met by wind power by the year 2030. ice. Three types of foundation have been proposed. Gravity caisson foundations are made of either concrete or steel and filled with dense minerals as ballasting. Monopile foundations are driven into the ground to depths of 10-20m. A tripod foundation has its origin in the offshore oil and gas industries and is a multi-pile foundation that shares the loading between the three legs. For more information on the foundations of In addition, offshore wind turbines see http://www.windpower.dk/tour/rd/foundat.htm. http://www.windpowerphotos.com/ also has a good slide show of wind turbine photos, particularly dealing with offshore applications. As well as the increase in size of wind farms, wind power will become more widespread with the greatest growth expected in Europe, North America and China. The size of turbines is also continuing to increase. Vestas, the world’s leading manufacturer of wind turbines per installed MW, no longer produce the 225kW machines that are installed at the Ten Mile Lagoon wind farm in Esperance; their smallest turbine being 660kW. The next generation of turbines being produced is in the multi-megawatt range (3 - 5MW). Currently under development in Germany is a 4MW Enercon machine with a rotor diameter of 112 m. The blades are so large that they must be manufactured in segments and internally `hooked’ together. The Danish are at the forefront of new offshore wind developments with planning proposals for 750MW currently submitted and plans for a total of 4,000MW by 2030 (essential to Denmark’s aim of meeting 50% of their electricity needs by 2030). In the UK there are plans for 18 offshore wind farms. One restriction on the development of offshore wind farms is that locations 0-10km from the land may be sensitive to adverse public reaction due to the visual effect on the coastal landscape. The technology available within the next decade, however, is likely to restrict economically feasible projects to water depths below 40m. 1.5.2 Offshore wind energy 1.5.3 Remote area power systems 1.5 Wind energy in the future Figure 1-8 The 4.95MW Vindeby offshore wind farm in Denmark As well as playing a role in the history of the large wind turbine industry (See Section – Electrical Power Generation), the market for small wind turbines (< 50kW) with permanent magnet alternators has also expanded but with its emphasis on off-grid applications. In 1999 there was a market growth of 35% in the small-scale wind turbine industry with the total number of machines produced in the West rising to 60,000 and a further 150,000 machines now installed in China. Traditionally, small-scale systems have been used in the marine and RV industry. The largest potential market, however, is that of Village Power. There are currently two billion people in the world without electricity and small wind turbines offer the opportunity of bringing power to remote (off-grid) communities throughout the world. Small turbines can be used to compliment existing small diesel generation systems or used in hybrid with PV systems. Figure 1-9 shows small wind systems (3x20kW Westwind turbines) incorporated as part of a wind-diesel station at Exmouth. Figure 1-9 Wind-diesel station at Exmouth (Source: http://www.afm.dtu.dk/wind/turbines/gallery.html) There is greater wind energy potential out at sea and offshore wind turbines generally yield 50 per cent higher output than turbines on nearby onshore sites. The most active countries in offshore wind power are countries in Northern Europe such as Denmark, Germany, the Netherlands, Sweden and the UK. These countries have limited high wind speed sites on land but many suitable offshore locations in relatively shallow water. In demonstration projects, turbines have been installed up to 6km from the coast on foundations in water depths up to 10m. Design of foundations must cater for loading from waves and pack 1-7 (Source: Courtesy of Western Power Corporation) 1-8 References: [1] Ackermann, T. and Söder, L. (2000), Wind Energy Technology and Current Status: A Review, Renewable & Sustainable Energy Reviews, 4, pp 318-321. [2] Boyle, G., (ed.) (1996) Renewable Energy – Power for a Sustainable Future, Oxford University Press, USA, pp 276-279. [3] IEA CADDET Renewable Energy Technologies Programme, Electricity from Offshore Wind (2000). [4] Wind Force 10 – A blueprint to achieve 10% of the world’s electricity from wind power by 2020, European Wind Energy Association, Forum for Energy and Development and Greenpeace International (1999). [5] Wind Power Facts – Why wind energy?, Danish Wind Turbine Manufacturers Association (1997). Useful Websites: http://telosnet.com/wind/ http://www.windpower.org/pictures/index.htm 1-9 ...
View Full Document

This note was uploaded on 06/09/2011 for the course PV 5053 taught by Professor Aasd during the Three '11 term at University of New South Wales.

Ask a homework question - tutors are online