Wind Turbines Manufacturer in China

In 2008 to combat in a series of negative factors, the world economy continues to come to an end years of high growth in 2009, the global economy are more likely to occur first post-war negative growth. Moreover, economic recession, inflation, and lurking in the economic and financial sector risks and to release and so on, which shows how the world economic recession and the risk of a step by step amplification. To stabilize the financial markets and stimulate economic growth, countries have introduced measures. However, the major economies are still hard to find signs of economic recovery, from 2009 the latest data, the major developed economies recession is becoming a deepening financial crisis is moving from developed to developing countries with rapidly growing the spread of the impact of the global real economy has been growing.

The face of the economic situation changes, the face of the international financial crisis, brought about unprecedented challenges, China has ever launched a new round of the intensity of macroeconomic regulation and control. To implement a proactive fiscal policy and loose monetary policy appropriate to pass a clear message: the expansion of domestic demand, to maintain growth, adjusting the structure of macro-control measures, will wind generators promote China’s economic difficulties and move towards a new stage of development. From September 15, 2008 the central bank announced that the first time in six years, cut lending rates, to 22008 years, in November Ten measures to expand domestic demand, the introduction to the china wind turbines Central Economic Work Conference reaffirmed the goal of insurance regulation and control of growth, to the ten industrial promotion policy of Intensive approved … … the face of crisis, China is decisive and effective way to initiate action.

Economic crisis in what form and when the end is still unknown. Weak international economy, protectionism, oil price fluctuations … … a series of international factor for China’s development has brought uncertainty, also in 2009 the Chinese economy has brought a series of challenges. If China’s economy can not effectively get rid of these shackles, in 2009 could be the following in 2008 that “the most difficult year” after a more difficult year. Of course, behind each of the challenges are bred of hope. In 2009 and future years, when the global crisis, but also anti-crisis and anti-recession in progress.

Can be seen that at a time when great changes in China’s wind power industry, the era of great development in the current economic situation, awareness of the situation under the control of the direction of the wind power industry impact and future development trend analysis to be informative, both for the China’s wind power industry’s long-term development, or on the wind power industry in the specific work of the breakthrough will have a positive guide. Then, in the current economic situation, China’s wind power industry will be what kind of impact? In China, wind power companies how should analyze the current development situation, to develop response strategies? Most importantly, how to find opportunity in crisis, access to a larger development?

This report is mainly based National Bureau of Statistics, the State Council Development Research Center, the National Development and Reform Commission, the State Ministry of Commerce, China General Administration of Customs, trade associations, as well as wind power generation industry research units of large amounts of data, combined with in-depth market research data, based on the the overall development of the current economic situation, the new situation China’s wind power industry development, economic performance data, key market segments, import and export, marketing, competitive situation and other analyzed and forecast, and the future of wind power development of the industry environment and development trend of the overall discussion and judged, in the end in front of a large number of analysis, forecasting, based on the study of the wind power industry’s future development and investment strategy.

American Wind Energy Association (AWEA) has revealed that the global wind energy in the 28.8% surge in 2008. In 2008 the United States built a 8.35GW of wind power capacity, for 50% of the original capacity, total capacity now has reached 25.1GW, accounting for one-fifth of the world’s wind power generation, and have gone beyond Germany’s 23.9GW, become the world’s wind power generation The first strong. 
American Wind Energy Association Executive Director, said Schweitzer homes in recent years, a growing emphasis on development of wind energy, wind power is expected in 2009 the United States will not only provide more American families new energy, but will also create more employment opportunities, to become the United States the new economic growth point. 

Practice has proved that the charm of wind generators is obvious, its energy cost is zero, pollution emissions, is also zero, and adequate supply. Arizona State University geography professor Maikepasi Gai Le Di said: "Great Plains region, wind energy is sufficient, if fully developed, only North Dakota, Texas and Kansas, the three states of the potential wind power on the sufficient to meet demand for electricity throughout the United States. " 

Increased investment in wind power 

As the world the process of seeking alternative sources of energy continues to accelerate, and now the world’s least 1000 large-scale energy companies and investment firms optimistic about the bright future of wind power, the world’s leading wind turbine manufacturers are keen to invest in companies in which the United States to invest in wind power generation is most active. 

U.S. General Electric Company recently announced that the next 10 years of investment in wind energy utilization will reach 5 billion U.S. dollars, while so far in this area, the company has invested 6.5 billion U.S. dollars. 4 years ago, General Electric from Enron’s bankruptcy estate acquired its fan manufacturing business. Thus, from the fans this year, GM expects sales and maintenance revenues will reach 20 billion U.S. dollars. 

California, the U.S. wind energy the most developed areas. Initially, the state government adopted a tax policy to encourage enterprises to establish a wind farm, the development of wind energy. After many years of promotion and development of wind farms in California offers a wide range of employment opportunities and higher taxes. Tehachapi is a small town in California, is one of California’s three major wind farm. Today, the U.S. government for the development of wind power reached the capital invested billions of dollars a year. Tehachapi town is like in the past the west, reproduced in 1849 in California’s "gold rush fever." 

FPL Group’s annual revenue as high as 90 billion U.S. dollars, a subsidiary of FPL Energy’s electricity production sector (FPL Energy) is currently the United States the number one wind power farm. FPL Energy in the United States a total of 43 family traditions electric field, are found in 15 states, accounting for the nation’s wind power capacity of around 40%. Sino-US energy companies began last fall to build a wind farm in Iowa, upon completion, will become one of the world’s largest wind farm. For the past few years, investment in wind energy projects in more than 20 billion dollars. 

2020, wind power will account for 5% of the total U.S. electricity generation, wind energy will also become very important in American daily life of a renewable energy. According to plan, by 2015, Colorado, 10% of the electricity utilities must come from renewable energy sources, wind energy is one of them. The eastern part of the current Colorado schools, cities and towns and some urban areas are using the local wind energy resources. 

Updated wind power technology 

In recent years, the U.S. small wind turbines technology has been a major improvement, such as improved fan blade design, the widespread use of wind sensors, using automatic control system, reduced manpower, reduced costs. Since the introduction of new technologies, especially the application of new materials and electronic control systems, the U.S. wind turbine power generation plant installation costs from 1984 to 3700 U.S. dollars per kilowatt, fell in 2003 to 535 U.S. dollars, is expected to drop to 2010, per kilowatt – below 300 U.S. dollars. In 1984, the United States, the cost of wind power would be 20 cents per kilowatt-hour is currently 3 cents, that can already be competing with conventional power generation costs. 

Currently used by more fans than ever before, more efficient, more stable performance. General Electric produced 1.5 MW 460 fans can meet people’s demand for electricity, up to 100 meters, Blade length 70 meters (more than the wingspan of a Boeing 747 aircraft, much longer). Therefore, taking into account tax incentives, a standard fan is now produced one kwh of electricity each costs only 3-4 cents, while the early 20th century, 80 per kilowatt of electricity cost is 20 cents. In the United States in some areas, or new natural gas power plants and coal compared to that of electricity generation method highly competitive. 

The United States attaches great importance to the development of new fans 10 years ago, a single typhoon machines typically 50 kW power generation capacity has now increased to 300-500 kilowatts or more, in 2002, a capacity of 600 kilowatts of fans in Hawaii, installed and put into use. At the same time, manufacturing, materials, fan blades have been widely adopted high strength and light weight composite materials, a number of cutting-edge aerospace technology is now also used in fan system. 

According to U.S. media reports, the U.S. government is vigorously promoting the fan manufacturing industry in order to become an important foundation for the 21st century, the energy equipment industry. It is predicted that by 2010, the United States and Europe will appear fan replacement climax, there will be a large number of old fans have been eliminated, so fans are very optimistic about market prospects. 

Policy support efforts to 

United States President Barack Obama promises, although the economic downturn, the Government will continue to adhere to increase wind energy production tax rate to stimulate wind energy development. Aim is to support the preferential policies, so that the price of wind power and allow the public affordable. At the same time, the use of wind energy companies in the project can get the first 20 years of 1.8% per kilowatt-hour tax deductions. 1 kwh of electricity is equivalent to 50-watt light bulb for 20 hours of electricity consumed. Experts believe that because the United States most of the power plant’s fuel —- coal and natural gas prices continue to climb, so wind power as an alternative energy becomes more attractive. 

Last year in October, as the 700 billion U.S. dollars emergency assistance to finance part of the law, the U.S. Congress that will help wind power industry and other new energy industry in production and investment tax relief plan and the formation of the law. The tax relief package provides tax relief for new energy production offers one-year extension of investment tax relief for 8 years. 

The industry believes that wind energy industry will also be a result of "renewable energy portfolio standard" benefit. There are already including California, Texas, New York and Massachusetts, including 17 states have adopted this standard. Although the specific content of the states between the standards vary, but all are requiring utilities to purchase electricity from renewable energy sources in the part must attain a certain percentage.

U.S. Department of Energy, said wind power by 2030 will account for 20% of U.S. electricity demand, supporting 50 million jobs, reduce greenhouse gas emissions equivalent to 140 million motor vehicle emissions, saving four trillion gallons. American Wind Energy Association is expected in 2009, issued by the nation’s 60 billion kwh of wind power would replace 91 million electricity barrels of oil, or 560 billion cubic meters of natural gas, equivalent to 9% of U.S. gas-fired power generation. 

With the declining cost of wind turbines, wind power increasingly shows its unique competitive edge. American Wind Energy Association revealed that the United States far more than 220 companies to participate in a government-led co-operation plan for the goal is to develop wind power generation equipment in the home. There are indications that more and more entrepreneurs are now favor wind energy, projects related to energy cooperation is gradually increasing, many multinational companies are becoming increasingly fierce competition between.

The world’s largest thin-film solar cell components of R & D companies – the United States FirstSolar (first solar energy company), will be in the Ordos City Hangjinqi photovoltaic power generation projects in construction, power generation capacity will reach 2G-watt (2000 MW).

According to a memorandum of understanding signed by both parties, both wind turbines sides will cooperate in the Ordos City, in the construction of a Hangjinqi has 2G-watt generating capacity of solar photovoltaic power plants. Project construction will be wind generators completed in four phases, the first phase of the start time is June 1, 2010, power generation, will be the size of 0.03G watts (30 MW); 2, 3 will be completed in 2014, the scale for the 0.1G W (100 MW) and 0.87G watts (870 MW), followed by the four project completion scheduled for 2019, the size of 1G W (1000 MW). The project area will reach 64 square kilometers, with an china wind turbines expected total investment of 4 billion to 6 billion yuan. Than the size of the station now operates the world’s largest photovoltaic power plant large 30 times. Is by far the world’s largest human use of solar energy projects.

“I think China is really making rapid progress in this area, although the wimdill development time is very short, but this year China is likely to become in 2009 the upper hand this year’s electric generating capacity in the world’s largest country. This illustrates the dynamics of the industry development. I think China is a wind energy can promote rapid economic development, a good example, because five years ago, China has almost no installed capacity of wind power equipment, this year, you could have the world’s first installed capacity, ” Zervos said.

“For me, this is very positive, because China is an important country in carbon emissions. Therefore, the Chinese government quickly to wind, solar and other renewable energy sources develop in the direction is very correct. We very much appreciate the Chinese in this regard as. I now believe that two or three years, China will become the world’s total installed capacity of electric upwind first country, “Professor Zervos is also the European Renewable Energy Council.

At present, the world’s largest companies upwind power generating capacity of the Vestas of Denmark, the United States, GM ranked second. Followed by Spain, India and Germany, China’s first wind power Huarui Technology Co., Ltd. ranks seventh in the world.

Professor Zervos said that he was to have so many people to participate in the sea wind of the General Assembly was very pleasantly surprised, the original 3,000 people are expected to participate in the result register shows that nearly 5,000 people attended the meeting and exhibitions.

“This shows that people’s great expectations for offshore wind power. It is a rapidly growing area. A variety of factors indicate that the development of wind power can and will achieve the European Union in 2020 to reduce carbon emissions by 20% of the target play an important role in the process of , “Zervos says.

During the meeting, the European Wind Energy Association released a report entitled “Opportunities of the ocean,” the report said, the EU has plans to develop 100GW of wind energy projects, so that the wind power by 2020 to reach 10% of total European consumption. This annual loss of 200 million tons of carbon emissions.

Wind energy industry has also published a “Declaration of the European wind energy at sea,” announced that the industry will ensure that offshore wind power to produce enough equipment, installation vessels, cable laying vessels, providing high-voltage transmission technology. At the same time, the declaration called on the European Commission to publish a blueprint for the North Sea grid, the EU’s energy security and infrastructure blueprint to provide financial support for low-carbon technologies, introduction of market integration, such as the road map.

“We are ready to further develop the industrial sector preparations, it is the politicians carefully developed framework to facilitate the development of offshore wind power. This requires in Copenhagen to reach a consensual agreement,” said Prof. Zervos.

With regard to the existence of a bubble in the industry there is a bubble or future danger, Zervos professor said he not think so.

“This is a heavy industry, there is no bubble, I do not have. wind generators for European land-based wind power has accounted for 4% of EU electricity. This is proof of benefit.”

The next European offshore wind energy by 2011, the General Assembly will be held in Amsterdam in the Netherlands.

In recent years, international crude oil prices running high, giving rise to national attention on energy issues, have to take effective measures to ensure energy supplies. The face of a possible energy crisis, competition for energy will be the main reason for the future of global conflict. Solve the energy crisis, first, to improve combustion efficiency in order to reduce resource consumption to achieve clean coal combustion in order to reduce pollution; second is to develop new energy sources, active use of renewable energy; 3 is the development of new materials, new techniques, to maximize energy efficiency.

< 2005 Nian 2 16, aimed at reducing greenhouse gas emissions, "Kyoto Protocol" entry into force, to include new energy sources including wind power to replace thermal power generation to reduce carbon dioxide emissions has become a global consensus, countries around the world are scrambling to develop new wind energy sources. In solar, biomass, and many other new energy industry, wind power industry is a national priority to develop the location. Wind power as a clean, renewable energy, more and more countries around the world attention. Yun amount of its huge, global wind energy is about 2.74 * 109MW, of which wind energy can be used for 2 * 107MW, than the Earth can be development and utilization of water volume 10 times bigger. Global wind-power generation are to 35% annual growth rate, Germany, the United States, Italy and other countries up to 50%, become a development trend, the global wind generators annual output has exceeded 5.0 billion.

< European Wind Energy Union (EWEA) 2004 Annual Report states: By 2010, wind power generation will account for 5.5% of European electricity demand; to 2020, you can 12%. Boss in wind power in Germany has been more than 70 private wind power development companies, the German domestic wind power by the end of 2005 the total wind generators installed capacity 17,574 units, with a total installed capacity of 18,428 MW, wind power accounted for 4.3% of the total generating capacity. Germany plans to wind power generation in 2050 the total generating capacity of 50%. Germany is the experience of wind power reached more than 50 countries and regions.

< 2005, China's National People's Congress passed China's first of a new energy legislation "Renewable Energy Law." Actively developing wind power has become our country to achieve sustainable development, ecological and environmental protection a basic national policy of one of the means, which will help improve China's energy structure, increase the quality of energy to overcome energy shortages, power shortages to eliminate bottlenecks.

< focus on the development of wind energy new energy for China, not only to change the energy structure of China is of great significance, but also to enhance the energy consumption of very large China's international image of great significance. Over the past year in the Chinese energy industry broke out again and again the vicious events: coal mine explosion in Shanxi, Jilin, explosions and so on petrochemicals. These are to a large extent of the damage China's image in the international community good. In December 2005, the British Thames Times published an article "Pollution in China," criticized China's energy policy.

While the clean and green renewable wind energy sources, but a high degree of dependence on the weather, thereby limiting its development. The use of ocean tides to generate electricity dependence on the weather, we should much smaller power, tidal power has therefore become the field of renewable energy sources in recent years, a hot new term. Recently, in the UK the world’s first tidal energy generators put into commercial operation.

This was named “SeaGen” tidal generator is located in Northern Ireland, Strangford Bay estuary, which is about 37 meters, 47 meters high, with a total weight of more than 300 tons. The principle is the use of tidal power tidal fluctuation of water level difference to wind generate electricity, the generator is equipped with two tidal energy turbines, is like an “underwater windmill“, its principles and wind power generation is also similar, except the wind push changed to promote the tides and currents, resulting in more environmentally friendly power. The system since May 2008 began trial operation, the current generating capacity of up to 12 megawatts, about 1,000 households to meet the average electricity demand, the highest in the world’s first tidal energy system capacity. However, tidal power because it is a new technology, its cost of wind  power generation is also high, about the cost of other new energy generating four to five times, but with improved technology and extension, which is expected to reduce the cost of the future. Tidal power generation is also being subjected to wave the size of the wind turbines impact and possible impact on marine life concerns, although “Se aGen” generating units have been commercially available, but its follow-up there are still many problems waiting to be resolved.

Pictures show the new generator wind blade and the wind blade’s detail structure.

The impeller wing section design done carefully by the aerodynamics expert, according to the airscrew structure, takes shape by the intensity glass fiber reinforced plastic, the end joint tech has the extremely low starting and cut-in point, ensures the low wind start and stable quiet running.the wind power utilization ratio enhance up to 0.26 from the traditional 0.5, the extremely high wind power utilization ratio.

Our Hummer Dynamo limited company contrasts the domestic and foreign several small wind-driven generator match blade manufacturer’s blade, through many tests in the foundation, the independent development has designed one kind of new wind blade

In view of the traditional glass fiber reinforced plastic wind blade cannot bear the gale, the low temperature easy break, the gale area service life not to surpass for 5 years and other flaws. Our hummer company developed high strength wind-driven generator wind turbines blade which has controlled the type straight. This wind turbines blade structure is firm, can bear 8 levels of gales.

Our hummerwind turbines mini wind-driven generator adopts outside rotor unique design, reached “own energy consumption low, the wind power utilization ratio to be high the high request. The new wind blade used cut -wind structure, the generator movement does not have the axial force, but can protect outside rotor maximum. Enabled the wind power utilization ratio enhance from traditional 0.26 to 0.43, has achieved the breeze start truly

Hummer wind blade’s successful application causes the problem that gale area such as Inner Mongolian prairie and coast where the wind-driven wind generator’s wind blade damage rate highly, is readily solved. Simultaneously made the entire wind turbine’s service life prolong three to five years. Because hummer mini wind-driven generator wind blade use “the end joint tech stable quiet running, also reduced the noise and has brought enormous convenient for user’s use and replacemen

The wind blade according to the airscrew structure and technics to manufacture, the wind blade has passed through the transient equilibrium test, firm and durable, design life for 8-10 years

After studying rotors blades at home and abroad, Hummer company independently designs a new type blade basing on a lot of tests

The traditional wind turbines  blades made in glass fiber reinforced plastic is not resistant to strong wind, it is easy to break at lower temperature and lasts less 3 years if used in strong wind areas. While Hummer’s blade is solid and resistant to wind 8-grade up, which overcome the shortcomings of traditional products .

For several years, we have been monitoring the runing condition of wind generator, as a reasult we successfully developd the auto controlling system for middle-sized and small-size wind genrator. That system not only can seek the wind direction automaticly, but can monitor the runing condition, rotating speed, wind turbines temprature, wind speed, wind direction,etc. At the same time all the parameters acquired by the monitor system wil be sent to the control centetr. when the wind generator runs abnormally, the control center will turn the blades out of  wind while turn them back into the wind when the abnormal conditions released.

The following is some photos of Hummer 3kw and 5kw wind-solar hybrid Inverter,

1. 3kw Hummer wind-solar hybrid inverter

2. 5kw Hummer wind-solar hybrid inverter

3. Back Panel

While the financial crisis dragged down the real economy, the building of wind farms in Inner Mongolia are contrarian speed run. Up to now, Inner Mongolia, wind power installed capacity of more than 300 million kw, ranking first in the country. 2010, Inner Mongolia, the total installed wind power capacity will exceed 5 million kilowatts.

Looking at the country. In 2008, China’s total wind power installed capacity to reach 12.2 million kilowatts, is “Eleventh Five-Year Plan” task two times. In 2009, the national total installed capacity is expected to reach 20 million kilowatts.

“The wind generators equipment manufacturing industry is not overheating, but a serious overheating”

The siren song of wind farm construction, gave birth to the huge demand for wind turbines equipment.

After several years of “Great Leap Forward” type development has been the national leader in wind power capacity in Inner Mongolia, wind power manufacturing sector is also wind and water. Wind power generation equipment manufacturing linked to interaction with the fans, priority was given to local manufacturing and assembly of wind power generation equipment, wind generators resources enterprise configuration, which greatly boosted the manufacturing sector in Inner Mongolia fan investment and development.

This year in January, Baotou Rare Earth exchange the whole Industry (Group) Co., Ltd. invested a “rare-earth permanent magnet motor series products and rare earth permanent magnet megawatt wind turbine” project settled in Baotou, project investment 280 million yuan, annual output of 12 wind turbines MW; in March of this year, from wind power in Guangdong Ming Yang Technology Co., Ltd. to invest in wind power generation equipment production projects blades settled Hohhot, the total investments by 10 billion yuan, annual output of wind power generation equipment 500 sets, 500 sets of wind blades.

At the same time, foreign wind power equipment manufacturing giants also have vied for Inner Mongolia. British-owned enterprise Tianshun (Suzhou) Metal Products Co., Ltd. signed a wind power tower tube production project cooperation agreement to make world-class professional manufacture technology of wind power equipment manufacturing enterprises have settled down in Baotou equipment manufacturing industrial park, with an annual output of wind power tower tube 800 (sets) of production capacity; No. 1 world ranking of wind power generation equipment maker Dan Maiwei Stas company is located in Hohhot, the first Taiwan factory to produce 850 kilowatts wind turbines. Plant a total Investment 6 billion, started construction in July last year, can produce 800 sets of wind turbines.

“China’s wind power equipment manufacturing industry is not overheating, but a serious overheating.” As early as March of this year at the China Wind Power Equipment Manufacturing Industry Development International Forum and there were experts.

Statistics show that domestic wind power machine manufacturing enterprises ultra-70, more than other parts of the world’s total wind power equipment manufacturers. At present, not only in the machine on the market there has been excessive influx of business conditions in the blade market is expected to rush into mass action phenomenon.

Rely heavily on the introduction of the core technology becomes increasingly obvious shortcomings of the missing

Although wind power generator small and large businesses sprouted up in the core technology and key components in such areas as manufacturing enterprises to go is the introduction of all-routes.

According to reports, the wind generators  manufacturing sector rush into mass action, heavy dependence on the introduction of its shortcomings become increasingly apparent.

First of all, the introduction of technology and the domestic wind power to adapt to the climate environment is often not been scientific proof. Once the grid, the potential quality and safety of a lot of problems. At the same time, the domestic wind generators have not formed as the foreign policy of “First there is a demand to build the project” and “the same regional production, the same regional consumption” model of industrial. Some local governments eager to build new wind power projects, resulting in waste of resources is not conducive to the orderly development of the market.

Second, the technology re-introduction, lack of self-innovation capability, resulting in high cost of wind power, industry profitability is generally low.

Third, digestion and absorption and slow pace, the lack of core technology is increasingly prominent. In particular, a large number of MW of new wind turbine rush into large-scale production, product quality problems become increasingly acute.

According to the National Energy Research Institute and the wind special committees research shows that products in the machine manufacturing enterprises in the process of running and trial there have been quality problems. State Power Longyuan Electric Power Group Corporation Chief Engineer, Young students, said: “from 2007 to 2008 two years, we have repeatedly encountered do not match the domestic business equipment, commissioning unit pass out of trouble, etc. But if you run assessment. Even put into operation Domestic units there have been many times the quality and technical problems. ”

China’s wind power industry lies not only in the construction of wind farms, but the main thing is should take this opportunity to promote wind power equipment manufacturing industry upgrade. Industry experts generally agreed that, in the face of wind power industry in recent years, the rapid rise of China’s urgent need to establish industry-access system, a sound of wind power technical standards and testing certification system for wind power equipment quality protection, and thus to promote market integration.

A windmill is a machine that is powered by the energy of the wind. It is designed to convert the energy of the wind into more useful forms using rotating blades or sails. The term also refers to the structure it is commonly built on. In much of Europe, windmills served originally to grind grain (hence the “mill” derivation), though later applications included pumping water and, more recently, wind generation of electricity. Contemporary electricity-generating versions are referred to as wind turbines.

In northwestern Europe, the horizontal-shaft or vertical windmill (so called due to the dimension of the movement of its sails) dates from the last quarter of the 12th century in the triangle of northern France, eastern England and Flanders. Joseph Needham states that the earliest known reference came in 1191 by a Dean Herbert of East Anglia, who supposedly competed with the mills of the abbey of Bury St Edmunds. These earliest mills were used to grind cereals. The evidence at present is that the earliest type was the post mill, so named because of the large upright post on which the mill’s main structure (the “body” or “buck”) is balanced. By mounting the body this way, the mill is able to rotate to face the (variable) wind direction; an essential requirement for windmills to operate economically in North-Western Europe, where wind directions are various. By the end of the thirteenth century the masonry tower mill, on which only the timber cap rotated rather than the whole body of the mill, had been introduced. In the Netherlands these stone towerlike mills are called “round or eight-sided stone stage mills, ground-sailers (windmills with sails reaching almost down to the ground), mound mills, etc.” (Dutch: ronde/achtkante stenen stelling molens, grond-zeilers, beltmolens, etc.). Dutch tower mills (“torenmolens”)  wind turbines are always cylindrical (such as atop castle or city wall towers). Because only the cap of the tower mill needed to be turned the main structure could be made much taller, allowing the sails to be made longer, which enabled them to provide useful work even in low winds. Such mills often have a small auxiliary set of sails called a fantail at the rear of the cap and at right angles to the sails; this rotates the cap through gearing so the sails face into the wind.