Strong Potential

Advanced monitoring techniques for wind assessment at higher heights

The success of the wind energy segment depends on accurate monitoring and resource assessment of the wind potential, based on which sites are selected for setting up wind power projects. This process is more cumbersome than usual when estimating the potential of offshore wind projects. Such assessments assist various stakeholders in formulating effective policies and regulations, or in making investment decisions.

India is working towards improving the business and regulatory environment, as well as providing necessary and reliable information on wind resources across the country. As modern wind turbines have larger rotor diameters and higher hub heights, identifying areas that have wind potential at greater heights is a crucial exercise. To this end, in October 2019, the National Institute of Wind Energy (NIWE) used advanced mapping techniques to assess the wind potential at 120 metres above the ground level (agl). Earlier, similar studies had been carried out by the NIWE at lower heights. In 2015, this mapping was revised by corroborating meso-scale-derived wind maps and micro-scale measurements, and a map of the wind potential at 100 metre agl was published.

The 120 metre potential assessment was carried out along similar lines at a spatial resolution of 500 metre using an advanced meso-micro coupled numerical wind flow model with data from 406 actual measurement sites across India. The study estimated an indicative wind potential by excluding unsuitable areas. The potential was stated in terms of capacity utilisation factor (CUF) and land categories to assist all stakeholders in decision-making. Unexploited potential areas were also covered in the study to enable a better understanding of new potential locations in India. The study included several sensitivity analyses on land use patterns to gauge the variation in the estimated wind potential.

Key results

According to the study, the estimated installable wind potential of India is 695 GW at 120 metre agl. Of this, 340 GW, 347 GW and 8 GW can be installed on wasteland, cultivable land and forest areas respectively. The estimated wind potential at 100 metre was 302 GW, significantly lower than the potential at 120 metre. Furthermore, a wind potential of 132 GW is possible in areas with CUF greater than 32 per cent, while a wind potential of about 57 GW is possible in areas with CUF greater than 35 per cent. In fact, based on the sensitivity analysis, with increased land area utilisation, the wind potential can increase to 98 GW, enabling a CUF of over 35 per cent.

For the better utilisation of renewable energy resources, areas that have a high wind potential (leading to higher CUF) can set up large wind farms, and areas with a lower CUF potential could be considered for either distributed generation or wind-solar hybrids. According to the study, high CUF potential regions are distributed across Andhra Pradesh, Gujarat, Karnataka, Maharashtra and Tamil Nadu, with a scattered potential across Kerala, Madhya Pradesh, Telangana, Jammu & Kashmir and Rajasthan. In addition, pockets of medium wind potential are located in Punjab, Haryana, Uttarakhand, Bihar, West Bengal, Odisha and across the north-eastern states.

Extended study of the offshore wind potential

As the offshore wind power segment has not been tapped in India and its importance has been growing steadily, the NIWE’s study also covered the potential of offshore wind in India. The NIWE carried out preliminary wind resource assessments and coordinated on bathymetric/oceanographic studies for the demarcation of offshore wind energy blocks as per the National Offshore Wind Energy Policy, 2015. The key points of the study are:

  • For the offshore wind energy market, cost drivers associated with different technologies vary significantly. Environmental constraints, seabed conditions and structure, wind resources, array layouts, grid connection, the turbine technology used, and installation methods have to be correlated in order to understand the scale of the opportunity and the capital expenditure required to realise a technology’s development.
  • Various initiatives are being taken for offshore wind development in the country, including preliminary assessments and collaborative studies. Pre-feasibility studies for offshore wind power development in Gujarat and Tamil Nadu were carried out under the Facilitating Offshore Wind energy in India project, a consortium led by the Global Wind Energy Council, in May 2015, and eight potential zones were identified.
  • NIWE has prepared an offshore wind resource map for India’s entire coastline up to 200 nautical miles (Exclusive Economic Zone), using satellite data.
  • Broadly, areas off the coast of Tamil Nadu, Gujarat and Odisha have better offshore wind potential.

Advanced technologies and satellite data were deployed for this assessment. The offshore wind map was prepared usingmonthly average surface wind data from the Quick Scatterometer (QuikSCAT). QuikSCAT was an earth observation satellite that carried the Sea Winds scatterometer. Its primary mission was to measure surface wind speed and direction over the ice-free global oceans. It emitted pulses of low-power microwave radiation and measured the power reflected back to its receiving antenna from the wind-roughened sea surface; the surface winds were then measured from the roughness of the sea surface.

Advancements in atmospheric modelling and resource assessment technologies

The NIWE has carried out a rigorous atmospheric modelling analysis on weather conditions. Its high resolution numerical modelling of weather conditions provides sensitive, high quality information that is crucial for the development of wind projects. Such modelling is also useful during the early stages of prospecting a wind farm design. Meso- and micro-scale coupled wind resource products have seen a rise in uptake by the wind power sector. They offer reliable and long-term reference data for wind condition characterisation, and were used by the NIWE in its aforementioned study. Furthermore, simulations were carried using the Weather Research and Forecasting System (WRF) atmospheric model developed by NCAR/NCEP. It is a highly sophisticated model that uses the latest advances in physics and numerics, and is employed largely for research, climate analysis and operational weather forecasting.

The NIWE uses various advanced data sets for its resource assessment and monitoring. Some of the more interesting satellite data sources are:

  • The topography data comes from the Shuttle Radar Topography Mission, which obtains elevation data to generate a high resolution digital topographic database of Earth.
  • Airport and helipad locations are also identified from satellite images. In addition, an intense online review is performed to identify airport locations, defence airports, under-construction airports, etc. This is crucial, as all airport locations are given a circular buffer area of 10 km, which is removed from the wind potential map.

In addition to the use of such advanced technologies, the NIWE has for a long time been an advocate for replacing meteorological masts with remote sensing devices such as light detection and ranging, and sound detection and ranging. These devices work on the Doppler shift principle and are better alternatives to meteorological masts due to their portability and ease of handling. They allow for short-term measurements, as well as measurements at multiple heights. In contrast, the installation of meteorological masts, onshore as well as offshore, is costly, time-consuming and laden with land constraints.

Future outlook

Going forward, it will be interesting to see how the results from these detailed assessments are used in the development of projects. Often, such rigorous studies just remain reference points and do not translate into growth for the sector due to unfavourable policies and regulations, and the lack of a positive business environment. Still, the NIWE’s proactive role in carrying out such technologically rigorous assessments is commendable and will definitely assist all stakeholders in the power sector.

By Sarthak Takyar

GET ACCESS TO OUR ARTICLES

Enter your email address