Chairman Emeritus Reconnect 39 – “Re-powering Windfarms”

My dear friends,

Wind is blowing today towards shifting to renewables in the interest of environment and mitigation of climate change. Wind energy is one of the important sectors of Renewable energy. Its origin has an interesting history traceable to Holland which is situated in a Continental dent of Europe, a third of the country lying below sea level. It is said that “God Created the World, but the Dutch Created the Netherlands” by constantly pumping water out to the sea by deploying windmills. Gradually they graduated to wind electric generators (WEGs).

Similarly Denmark in Scandinavia relied heavily on wind power. At times its surplus wind power was shared amongst Germany, Norway and Sweden which can store it in hydropower systems for later use. Denmark became a pioneer in developing commercial wind power during the 1970s, and even today a substantial share of the wind turbines around the world are produced by Danish manufacturers.

Blind Import of Technology

When India started looking at wind power option in later part of 1980’s, the above two countries naturally attracted attention. Particularly Denmark, exporting wind turbines to an advanced country like USA, engrossed attention of Indian collaborators who were keen to manufacture turbines within the country. About 20 manufacturers collaborated to replicte the designs of Danish machines typically having 30 m hub height and 30-40 m rotor diameter. Though we started with demonstration projects of 55 kW / 90 kW turbines, we went ahead with 225 kW to 600 kW, private sector investment flowing in from early 1990’s. With blind import of technology (similar to “waste-to-energy” plants with inadequate knowledge of the local resource) supported by MNES’ promotional policies and incentives, India installed about 1500 MW of wind power in little over 15 years (1516.87 MW by 31-Mar-2002 to be precise).

However, the Capacity Utilization factor (CUF) was generally found to be in the range of 5-10%. This perplexed everyone concerned. Even those responsible for wind resource assessment and analysis of performance of Demonstration projects could not provide timely clues about the influence of differential power law indices in Europe and India. One wind power developer, however, experimented by installing two wind turbines in his windfarm, one with 30 m hub height and the other with 50 m. The energy capture of the turbine at the higher hub height was remarkably higher, more than compensating for the higher cost of the installation due to higher height and deeper foundation. This was an eye opener to make everyone realize that the wind resource of a tropical country like India was different than Europe. The power law index being different, it was sensible to go for higher heights and since then the turbines installed in India are located 50 m and above from the ground level.

Commonly used models now a days are rated at 1.5 MW to 2.1 MW and even higher. With advancing technology of harnessing wind energy at higher heights, these higher rating WEGs have hub height of 80-100 m and rotor diameter of 90-100 m. The type of generator and rotor are of cutting-edge design resulting higher CUF. Typically a MW range WEG has CUF of 20% in low wind area and 25-30% in high wind sites.

Despite mid course correction what happens to 1500 MW old sites?

Country has to pay serious attention to the fact that despite midcourse correction for new windfarms, can it afford to keep underutilizing the wind resource of the sites where 1500 MW is standing with 5-10% CUF? Over the decades those machines would also have been derated substantially, some of them having outlived their expected  life.

If new generation WEGs with taller hub height and higher rotor diameter are installed at sites now occupied by old WEGs, not only the MW installed capacity would increase but generation would multiply manifold. It would therefore be in national interest to re-power these old inefficient windfarms.

Since higher height and higher rating WEGs were installed after March’2002, the cut-off date for re-powering may be considered as 31-Mar-2002, as suggested by Consolidated Energy Consultants Ltd.(CECL). Based on this cut-off date, the potential for re-powering happens to be:

90 MW in Andhra Pradesh

64 MW in Karnataka

178 MW in Gujarat

311 MW in Maharashtra

22 MW in Madhya Pradesh

838 MW in Tamil Nadu

Total 1503 MW

This means that there is a possibility of doubling the capacity of old windfarms and multiplying their generation.

Several demonstration windfarm projects of small capacity were installed with an aggregate capacity of 73 MW and these can be readily available for re-powering. These WEGs can easily be replaced with the consent of Central and State Governments. Already one windfarm in Maharashtra is being re-powered. The other windfarms which can be considered for re-powering are those commissioned till 2002 and having WEG operating upto 600 kW. These wind farms are mostly located in the state of Tamil Nadu and partly in Gujarat.

Since the country sets targets in terms of installed capacity and not the actual generation, it would be an effort to convince the authorities that though the re-powering of old windfarms would contribute to doubling their capacity from 1500 to 3000 MW, qualitatively the upgraded capacity would generate at 20-30% against the old windfarms’ CUF of 5-10%, generation going up 10-times optimizing the land use. We should hasten this historic correction not only through retrofitting or inter-cropping of taller WEGs but also crossbreeding with solar PV (wind and solar complementing each other in the diurnal variations), under the National Action Plan on Climate Change (NAPCC).

Satyamev Jayate !!!

Best wishes and Regards,

Dr. B.S.K.Naidu

BE(Hons), M.Tech., Ph.D., CBI-Scholar, D.Engg. (Calif.), FNAE, Hon.D.WRE (USA)
Chairman Emeritus, Great Lakes, Gurgaon, NCR, New Delhi, INDIA
Former Director General (NPTI & CPRI / REL), Ex. Director (REC) / Executive Director (IREDA)

No job is small or big, the way in which you do, makes it small or big (c)

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