Windmills produce the cleanest renewable energy

by W.T.J.S. Kaviratne, Ambalangoda Special Cor

Historic records reveal that a ‘wind–drawn’ wheel was used to operate a machine as far back as the first century AD by a Greek engineer known as Heron of Alexandria. This was considered the first known instance of wind power being used to operate machines.

In ancient Tibet and China, similar wind-drawn wheels were reportedly used for numerous purposes since the fourth century. As early as 200 BC, windmills were used in Persia (modern Iran). In the 17th century, Babylonian Emperor Hamurabi had exploited wind power in irrigation projects.

An old windmill

Historical evidence proves that people from around the world were aware of wind power and how to use it in grinding grains. Windmills were also used to pump water, drain pools and lakes, extract ground water and for many other industrial purposes.

Converts wind energy

A windmill converts wind energy into rotational energy which in turn provides power to operate a machine.

In Holland windmills existed since 1200 AD and by the end of the 16th - 17th centuries, the number of windmills increased tremendously and it was estimated that there were more than 9,000 windmills in Holland in the 19th century.

In 1887, Prof James Byth in Scotland invented the first wind turbine of ‘vertical axis’ producing electricity and Charles F. Brush in Cleveland, Ohio, USA invented the first wind turbine of ‘horizontal axis’.

Denmark is globally known as a leading generator of electricity from wind power. The Danish wind turbine industry originated with the invention of its first wind turbine by Professor of Natural Science Poul Lo Cour and a team of scientists of Askov Folk High School in 1891. This project was funded by the Danish government. Within a few years, construction work of similar small-scale village power stations took place all around the agricultural countryside of Denmark.

Today, it is estimated that Denmark is responsible for over 50 percent of the world’s wind energy production. Twenty-four percent of the electricity produced in Denmark is from wind power, a world record. The Danish government aims at generating 50 percent of its electricity requirement from wind power by 2020 and plans to be independent of fossil fuel by 2050.

Even though there are 25 large manufacturers of wind turbines in the world, the top ten are responsible for manufacturing 95 percent of the wind turbines. Four of these companies are Vestas Wind Systems in Denmark, Enercon in Germany, NEG Micon in Denmark and Gamesa in Spain; they have produced two-thirds of the wind turbines installed throughout the world.

By the end of 2011, it was estimated that the capacity of electricity generated globally by wind power was around 238,351 Megawatts (MW).

The wind turbine is considered as yet another landmark invention and a great leap for mankind, creating avenues in generating renewable energy, replacing the power and energy produced by fossil fuels.

Wind turbines

Wind turbines are manufactured in a range of vertical and horizontal axis types. Like old windmills, they are mounted on tall towers of over 100 feet (30 metres) above the ground to capture wind power. They catch the wind’s energy with their blades mounted on a shaft to form a rotor. These blades are quite similar to the wings of an aircraft.

Whenever the wind blows, a pocket of low pressure air forms on the downward side of the blade. The low pressure air pocket then pulls the blade toward it, causing the rotor to turn in an action known as ‘lift’. The force of the lift is much stronger than the wind’s force against the front side of the blade which is called ‘drag’.

The combination of both lift and drag causes the rotor to spin like a propeller and the turning shaft spins the generator of the wind turbine to produce electricity. This electricity can be connected to a utility grid.

The European Union (EU) advocates the policy of reducing greenhouse gases by 20 percent from the 1999 levels. Increasing the consumption of renewable energy to 20 percent and improving energy efficiency by 20 percent for all its 27 member countries is the target. This was the first region to install off-shore wind turbines in 1991, in Vindeby.

A wind farm is an area where many wind turbines are installed. There are wind farms with over 100 wind turbines, covering a land area extending hundreds of square miles.

The largest ‘on shore’ wind farms are in California, USA and China and the largest ‘off-shore’ wind farm is in the United Kingdom. The world’s largest wind turbine constructed by the German wind turbine manufacturing firm, Enercon, E.126 was installed in Germany.

An off-shore wind turbine

Air density is one of the key factors in selecting areas for wind farms; the wind does not blow constantly and wind speed also varies from area to area. Off-shore wind turbines function more effectively than on-shore wind turbines as the wind blows stronger at sea than on land.

Global power generation

According to statistics, of the energy generated by wind power globally in 2009, USA had produced 35,159 MW, China 26,010 MW, Germany 25,777 MW, Spain 19,149 MW, India 10,149 MW, Italy 4,850 MW, France 4,521 MW, UK 4,092 MW, Portugal 3,525 MW and Denmark 3,497 MW.

Since early 1999, scientific research had been carried out in Sri Lanka on the feasibility of generating renewable energy from wind power. In 2003, the National Renewable Energy Laboratory (NREL) in USA carried out research on the feasibility of exploiting wind power in the island to generate renewable energy.

This research revealed that out of 65,000 kilometres of the total land area of the country, six percent covering around 4,100 square kilometres and 700 square kilometres of lagoons possess sufficient wind to produce energy. According to the Wind Energy Resource Atlas of Sri Lanka prepared by NREL, nearly 24,000 MW of electricity could be generated by wind.

The North Western coastal region from Kalpitiya North to the Mannar Island and Jaffna Peninsula, Central Highlands and parts of the Sabaragamuwa and Uva Provinces had been identified by the NREL as having suitable wind conditions for the production of wind energy. The Board of Investment has already given approval to four companies dealing with wind turbines to invest US$ 68 million to produce wind energy.

Five farms

Five wind farms operating in Sri Lanka are currently connected to the national grid. The wind farm at Hambantota, the first in Sri Lanka and operating since 1991, generates three MW. The wind farms at Ambewala (Central Hills) generates three MW, Mampuri (Puttalam) 10 MW, Seguwantivu 9.4. MW and Vidatamunai 10.4 MW. A team of Canadian engineers is researching the installing of a wind farm in Jaffna, to produce 134 MW of electricity.

At present 58 percent of the island’s power and energy requirement is produced by thermal power plants, 41 percent by hydro electricity and one percent by wind turbines. If wind power is properly exploited, it could generate nearly 20,000 MW according to the findings by NREL.

Wind power is globally recognised as the most environmentally-friendly renewable energy source because in generating electricity from wind energy, no fossil fuel such as oil, gas or coal are used. It doesn’t release greenhouse gases such as Carbon Dioxide, Methane or Nitrous Oxide to the atmosphere either.

Recently, the Minister of Power and Energy Patali Champika Ranawaka revealed that by 2015, the Government planned to generate 10 percent of Sri Lanka’s power and energy requirements from renewable sources of energy.