Prof. M. Gunawardana
International University of Management-Namibia
Energy is viewed as a strategic resource that provides the basis of our life and wealth. As with sunlight, the earth is extensively exposed to the wind. It is free and abundant. The wind helped to pump water, mill grains and sail ships for thousands of years. This article evaluates the capacity of the wind as a complementary energy resource.
Story of Winds
Around 5,000 years ago, the Paranoiac Kingdom in Egypt used the wind to sail ships on the Nile River. More than 4,000 years after that Persians (Iranians), the Chinese, Indians, Greeks and Roman empires dominated the sea by wind-powered ships.
Besides that, ancient people used wind-powered mills to grind grain. The Iranians were known as the earliest users of windmills. In the medieval period, technicians of Holland introduced an efficient model of the windmill that still dominates the landscape of the country.
Later, the first American colonists brought windmill-technology that helped to pump water, grind grain and power sawmills. Since 1920, rural areas of the United States of America have profited from wind-driven electricity.
After the industrial revolution, the growing demand for electricity could not be supplied by the wind. The rapid industrialization in the west gave birth to electricity lines.
Moreover, to cope with the accelerating demand for energy, coal, gas, oil and hydro-electricity acted as key energy suppliers. Finally, the windmill disappeared.
Currently, the surging oil prices, emerging power crises and looming climate change have forced nations to re-engineer their energy protocols by accommodating complementary energy resources, such as wind energy.
Birth of Winds
Wind is the flow of air. The wind energy originates from the sun. Wind is the action of air. Around 1% to 3% of the sun’s energy that reaches the earth is transformed into wind energy. The earth receives a lot of energy from the sun in the form of heat and light at different rates. Because of this, the earth’s ocean and the atmosphere are heated. In addition, the surface of the earth heats up faster than oceans. The equator area gets more heat than the poles. The heated air of the earth’s surface expands and goes higher, while cool air dashes in to fill that empty space created by the wind.
Additionally, massive atmospheric winds that encircle our planet are created, because the areas near the equator are heated more than the poles.
How It Works
Wind energy is a form of solar energy. Wind patterns and ocean currents spread out the sun’s energy across the continents. Warmer ocean temperatures could develop higher wind speeds and larger storm surges.
Wind is a renewable energy. Its supply is limitless.
The airfoil-shaped windmill blades catch the kinetic power of the winds. The wind flows over the blades and make them to rotate. The rotating blades and the grinder of the mill are connected to a shaft.
The wind turbines produce electricity by revolving the shaft that is connected to the generator. The generator converts mechanical energy into electricity.
Usually, the wind turbines are fitted with three reinforced blades. These blades bear the advantages of great intensity, fatigue resistance and high efficiency. They show high performance even at the low wind speed.
Speed Factor
Wind speeds are divided into seven classes. The basis of this classification (refer: www.ucsusa.org ) is ‘the average wind speed above the area of a land’, usually 50 metres high. For instance, the wind speeds of class three (6.7-7.4meters per second) and above are required to generate power economically. The elevation of the turbine is a deciding factor for wind speeds required for generating electricity. Higher wind speeds can generate higher volumes of power.
An average wind generator requires a wind speed of not less than 16 km per hour.
According to Betz`s Law (German Physicist Albert Betz – 1919), a wind turbine extracts about 59% of the energy. The rest flows through the turbine’s cross-section.
Surface roughness and wind obstacles such as big trees or constructions determine the speed of wind. Before the building of a wind turbine or wind park, it is vital to erect a meteorological tower with the necessary instruments to collect the wind, wind flowing trend and other site parameters.
Furthermore, there should be adequate space between each wind turbine in a wind park to minimize the efficiency loss. The height of an average metrological tower is around 40 metres.
A well-constructed wind turbine could have a 35% capacity factor (actual energy generated within a year). The capacity factor of an oil plant is 30%, a coal plant is 70% and a nuclear power reactor is 90%.
The length of turbine blade is another factor that decides the energy output. A 40-metre long turbine-blade possesses 5,029 square metres of wind swift area and power output is nearly 5.5 million KWh per year. By increasing the length of turbine blades, a wind turbine can produce more electricity.
Types of Turbines
Modern wind turbine technology has introduced a number of products with different sizes and different designs. Denmark, the global leader in wind energy technology, exports wind electricity generators ranging from 250 watts to 50 000 watts units, that can power dairy farms and small villages.
More than 50% of the turbines used in the world are made in Denmark. Aan Hui Hummer Dynamo (www.allwindenergy.com), an emerging Chinese wind technology company, produces mini-wind generators, home-wind generators, industrial wind generators and marine-wind power stations, starting from 250 watts to 5 megawatt (MW).
Presently, there are two types of wind turbines available in the market. They are known as Horizontal-axis and Vertical-axis wind turbines.
(1) Horizontal axis: – This type of wind turbine is fitted with blades similar to the propellers of airplanes. These blades catch the wind and spin. A typical horizontal-axis wind turbine is around 65 metres tall and fitted with three massive blades attached to an axle. The axle is connected to the gearbox.
The power generator is housed in a box (nacelle) behind the blades and it converts wind energy into electricity. These types of wind turbines were used in pre-industrial Denmark. But the modern horizontal axis turbines are more productive than ancient models.
(2) Vertical axis: – This type of wind turbine is fitted with blades that set from top to bottom vertically. And it is around 30 metres tall. A vertical axis-wind turbine looks like a Hugh two-blade eggbeater. They are used for small-scale commercial establishments or pilot projects. Anyhow, still these types of wind turbines are not so popular and commercially not viable.
Wind Farms
Germany, Spain, USA, Denmark, China and Italy began to develop advanced wind turbines and wind farms to face the 1970`s oil-shock. A cluster of wind turbines constructed in a location is called ‘wind farm’. It produces electricity for villages, residential areas or industries.
Most of these wind farms are built, operated and owned by private electricity companies. The American Wind Energy Association has initiated a 5,000-MW wind farm project. The Horse Hollow Wind Energy Complex in Texas, USA is the world largest wind farm with 421 turbines. It supplies electricity for 230,000 households. Virtually, this wind farm can power entire capital-city areas (like Windhoek) of Namibia.
The construction timeline for a wind farm is around 2 years and it is relatively faster than other power plants.
The Middlegrunden wind farm in Denmark is the world’s largest offshore wind power station that provides electricity for 132,000 houses. The wind farm at Wellington city, New Zealand generates 200 MW to provide electricity for 111,000 houses.
Prominent Users
The unpredictable oil prices coupled with greenhouse gas emission have pushed the governments, businesses and communities to explore environmentally friendly energy sources. Wind energy is one of them.
The multinational business corporations have taken a serious note on renewable sources including wind energy. Royal Dutch Shell and British Petroleum spend millions of dollars for the research and development of renewable energies like solar and wind energies.
Johansson & Johnson, well-known pharmaceutical manufacturer, receives 30% of its electricity in the form of renewable sources: biomass, solar and wind. Wall Mart, the American supermarket kingdom is aggressively promoting solar and wind energy for its 6,600 branches worldwide.
Transnational computer chip manufacturers like Intel and Advanced Micro Devices, use energy extensively.
Windy Economics
The following factors highlight the economics of wind energy: (1) the cost of wind energy is decided by the average wind speed and the size of a wind farm. (2) Wind energy is a highly capital-intensive technology. (3) The cost of wind energy is declining faster than the cost of conventional generation. It today costs only about one-fifth as much as in the mid-1980s. (4) Wind energy produces no emissions, so there is no damage to the environment or public health from emissions.
Anyhow, in comparison to many energy products, the cost of wind energy is declining slowly. According to the study of the Electric Power Research Institute, even though the production cost of wind energy is currently in a competitive range with those of mainstream power technologies, it would ultimately become the least expensive electricity generation source.
Also, we should not forget that fossil fuels accelerate global warming imposing costs, particularly on developing nations, in the form of increased health expenses.
Key Players
Wind energy is the fastest growing power-technology in the world. The wind energy capacity of the United States is 11,699 MW in the last year and by 2020 it will provide 5% of the national electricity demand.
Emerging economic powerhouses in Asia – China and India – have taken a serous note to invest in green energy such as solar and wind. For instance, according to the Economist (July 21-27, 2007) China’s venture capital investment in clean energy is picking up, from US$170 million in 2005 to US$425 million in 2006.
There are now more than 40,000 wind-turbines in 40 countries.
Denmark, the wind energy pioneer in the world, produces 20% of the electricity form the wind. Is it not a miracle?
Technologically advanced nations like America, UK, Germany, Denmark, China and India have begun to allocate more resources for research and development for alternative energies.
The following 10 countries are the key global players in the wind industry in 2006: Germany – 21,283 MW, Spain – 12,801 MW, USA -11,699 MW, India – 7, 111 MW, Denmark – 3,140 MW, China – 2,956 MW, Italy -2,123 MW, United Kingdom – 2,175 MW, Portugal – 1,874 MW, France – 1567 MW.
Serious Challenge
Renewable energies are born with limitations.
As per the United Nations “World Energy Overview (2004)”, the global electricity production share of non-hydro-renewables is less than 2%.
They alone will not guarantee the survivorship and growth of our energy-intensive economies.
However, through innovation and research, there are potentials to expand the capacity of renewables.
For some decades, their contribution to the global energy pool will not exceed 10%.
Despite environmental worries and other criticisms, nations will definitely use coal, oil, gas and nuclear energy to keep their economic sectors alive.
Meanwhile, renewable energy sources will continuously serve as smart energy partners in the global economy. So, we need winds, too!