**2. Identification of offshore wind potential sites**

offshore wind farms. The promising factors for offshore wind development are (1) powerful and consistent winds compared to onshore, (2) low sound pollution and visual intrusion, (3) best benefit to coastal areas due to less transmission cost and losses, and (4) easy transporta-

Europe is leading the offshore wind market since the inception of its first commercial offshore wind project in 1996 with an installed capacity of more than 8 GW connected to grid as of 2014. The installed capacity of wind farms in Europe is 8.045 GW [1], while in China and Japan are 0.67 and 0.05 GW, respectively [2]. Proposals exist to expand the respective capacities to 24 GW (Europe) [3], 10 GW (China) [4], and 1 GW (Japan) [5] by 2020. Actually, more than 90% of the global offshore wind farms were located in European waters, and the contribution from various countries is shown in **Figure 1**. In 2013, the world's largest wind farm "London Array" with a capacity of 630 MW is commissioned in United Kingdom [6]. A project with 0.468 GW capacity is under construction in USA with proposals for expanding

Developing country like India is yet to meet the required energy demands through existing installed capacities of 259 GW [8]. During fiscal year 2013–2014, India has experienced an energy shortage of 4.2% (960 BU against a demand of 1002 BU) with a peak shortage of 4.5% (130 GW against a demand of 136 GW) [9]. The southern region has experienced a severe energy shortage of 6.8% with a peak shortage of 7.6% [9]. Tamil Nadu, Andhra Pradesh, Karnataka, and Kerala belonged to this region and have a coastline of 3100 km [10]. Offshore wind being pollution free would be an ideal solution to meet the increasing demand as these coasts were blessed with significant winds. India initiated the efforts toward the development of offshore wind in the potential locations, and policy guidelines were formulated by the Ministry of New and Renewable Energy (MNRE) to promote offshore wind projects. Prior to finalization of offshore wind policy in India, it was essential to study the key aspects such as identification of potential sites, selection of suitable wind turbines capacity, and arriving at feasible incentives to promote offshore wind, which were

Various technical institutes working with MNRE and the Ministry of Earth Sciences (MoES) along with the global partners carried out offshore wind assessment studies and identified

tion of larger capacity turbines.

148 Stability Control and Reliable Performance of Wind Turbines

the capacity to 10 GW by 2020 [7].

**Figure 1.** Installed capacity across the world (2014).

performed.

Wind Atlas gives good indication of the geographical distribution of the wind resource and will be useful for decision making and planning of feasibility studies. However, to meet the bankability requirements, precise measurements are required for a couple of years at the proposed site. Conventionally, Wind Atlas is generated using analytical wind measurements at a number of sites across the country. As long-term historical wind data are not available at all the terrains in India, the National Institute of Wind Energy (NIWE) has used Karlsruhe Atmospheric Mesoscale Model (KAMM)/Wind Atlas Analysis Application (WAsP) developed at Risø DTU National Laboratory and generated numerical Wind Atlas for India [11]. Verification of model results was carried out using measured wind speeds and directions from onshore NIWE metrological masts. The offshore winds till 100-km deep into ocean are also generated using the same model, and results need to be verified using measured offshore winds. The offshore Wind Atlas shows significant potential along the southern Tamil Nadu coast as shown in **Figure 2**.

**Figure 2.** Numerically generated offshore and onshore wind resource maps for India by NIWE (source: Risø DTU, Indian Wind Atlas, Center for Wind Energy Technology [11]).

NIWE has commissioned a 100-m high-guyed offshore mast in the coastal line of Dhanushkodi, Rameshwaram, to understand the wind profile behavior in the region. The measurement is the first of its kind in India being conducted in a narrow strip into the sea at Dhanushkodi, which gives a close representation for offshore wind. The data have been monitored since October 2013, and the 4-year-old measured wind profile at Dhanushkodi looks promising for wind power potential with a mean wind speed of 8.5 m/s.

The European Union (EU) Delegation to India granted the Facilitating Offshore Wind in India (FOWIND) project to the consortium led by the Global Wind Energy Council (GWEC) including DNV-GL, Center for Study of Science, Technology and Policy (CSTEP) with an objective of assessing and promoting the offshore wind power development in India and aiding in facilitating India's transition toward a low carbon energy future. FOWIND reported that a number of agencies and institutions have assessed the offshore wind potential of the Indian coast including the coasts of Gujarat and Tamil Nadu. However, all of these studies are subject to various limitations with a possibility to draw various conclusions. Based on the various studies, FOWIND identified the significant offshore wind potential zones as shown in **Figure 3**. (Source: FOWIND pre-feasibility report at www.fowind.in.)

To study the wind characteristics, the wind speeds along Rameshwaram, Kanyakumari, and Jakhau were obtained from INCOIS at a 10-m elevation and extrapolated to 80 m using power law with a shear coefficient of 0.14 [13]. The mean wind speeds at Rameshwaram, Kanyakumari, and Jakhau for derived winds at an 80-m elevation are 8.5, 9.1, and 7.3 m/s, respectively.

**Figure 4.** Offshore wind potential maps for Indian coast by Earth System Science Organization (ESSO)-INCOIS.

A suitability analysis for these three potential sites along the Indian coast was carried out by Earth System Science Organization (ESSO)-NIOT based on the wind data obtained from ESSO-INCOIS. The properties of various class II wind turbines available in the market, in the range of 2–7 MW, were considered to identify suitable turbine. The uncertainties due to measurement scheme, futuristic wind prediction, and wind shear for measured wind speeds were considered, and the plant load factors at various probabilistic levels like 50 (P50), 75 (P75), and 90% (P90) were arrived at. It is observed that Repower 3.4-MW turbine performs well at both the locations. The power production from wind turbine after accounting for various losses like turbine unavailability (3%), Wake effects losses (8%), and electrical losses (5%) for

 Suzlon 2.1 0.43 0.45 0.47 0.37 0.38 0.40 Repower 3.2 0.40 0.42 0.44 0.33 0.34 0.36 Repower 3.4 0.51 0.53 0.55 0.43 0.45 0.46 Repower 5.0 0.39 0.40 0.42 0.33 0.34 0.35 Repower 6.2 0.31 0.33 0.34 0.30 0.31 0.32

1 Repower 3.4 0.43 0.45 0.46 0.37 0.38 0.39

**Kanyakumari Rameshwaram**

**(P90) (P75) (P50) (P90) (P75) (P50)**

Offshore Wind Feasibility Study in India http://dx.doi.org/10.5772/intechopen.74916 151

Repower 3.4 MW turbine is given in **Table 1**.

**(MW)**

Plant load factors after incorporating losses in power production

**Table 1.** Performance of wind turbines at potential sites (plant load factor).

**S. no. Company Capacity** 

The Indian National Centre for Ocean Information Services (INCOIS) has developed wind potential maps based on satellite winds from QuickSCAT as shown in **Figure 4** [12]. These satellite-derived winds were validated and calibrated using in situ winds from five moored buoys deployed by the National Institute of Ocean Technology (NIOT) along the Indian coast. The wind potential maps generated by these institutes indicate significant potential along Tamil Nadu and Gujarat coast. It is observed that winds of magnitude 6 m/s or more persist for more than 300 days and 8 m/s or more persists for about 200 days along the southern coasts of Tamil Nadu. The wind potential maps generated by both the institutes indicate Rameshwaram and Kanyakumari along the Tamil Nadu as suitable sites for setting offshore wind farms.

**Figure 3.** Offshore wind potential zones identified by FOWIND.

NIWE has commissioned a 100-m high-guyed offshore mast in the coastal line of Dhanushkodi, Rameshwaram, to understand the wind profile behavior in the region. The measurement is the first of its kind in India being conducted in a narrow strip into the sea at Dhanushkodi, which gives a close representation for offshore wind. The data have been monitored since October 2013, and the 4-year-old measured wind profile at Dhanushkodi looks promising for

The European Union (EU) Delegation to India granted the Facilitating Offshore Wind in India (FOWIND) project to the consortium led by the Global Wind Energy Council (GWEC) including DNV-GL, Center for Study of Science, Technology and Policy (CSTEP) with an objective of assessing and promoting the offshore wind power development in India and aiding in facilitating India's transition toward a low carbon energy future. FOWIND reported that a number of agencies and institutions have assessed the offshore wind potential of the Indian coast including the coasts of Gujarat and Tamil Nadu. However, all of these studies are subject to various limitations with a possibility to draw various conclusions. Based on the various studies, FOWIND identified the significant offshore wind potential zones as shown in **Figure 3**.

The Indian National Centre for Ocean Information Services (INCOIS) has developed wind potential maps based on satellite winds from QuickSCAT as shown in **Figure 4** [12]. These satellite-derived winds were validated and calibrated using in situ winds from five moored buoys deployed by the National Institute of Ocean Technology (NIOT) along the Indian coast. The wind potential maps generated by these institutes indicate significant potential along Tamil Nadu and Gujarat coast. It is observed that winds of magnitude 6 m/s or more persist for more than 300 days and 8 m/s or more persists for about 200 days along the southern coasts of Tamil Nadu. The wind potential maps generated by both the institutes indicate Rameshwaram and Kanyakumari along the Tamil Nadu as suitable sites for setting offshore

wind power potential with a mean wind speed of 8.5 m/s.

150 Stability Control and Reliable Performance of Wind Turbines

(Source: FOWIND pre-feasibility report at www.fowind.in.)

**Figure 3.** Offshore wind potential zones identified by FOWIND.

wind farms.

**Figure 4.** Offshore wind potential maps for Indian coast by Earth System Science Organization (ESSO)-INCOIS.

To study the wind characteristics, the wind speeds along Rameshwaram, Kanyakumari, and Jakhau were obtained from INCOIS at a 10-m elevation and extrapolated to 80 m using power law with a shear coefficient of 0.14 [13]. The mean wind speeds at Rameshwaram, Kanyakumari, and Jakhau for derived winds at an 80-m elevation are 8.5, 9.1, and 7.3 m/s, respectively.

A suitability analysis for these three potential sites along the Indian coast was carried out by Earth System Science Organization (ESSO)-NIOT based on the wind data obtained from ESSO-INCOIS. The properties of various class II wind turbines available in the market, in the range of 2–7 MW, were considered to identify suitable turbine. The uncertainties due to measurement scheme, futuristic wind prediction, and wind shear for measured wind speeds were considered, and the plant load factors at various probabilistic levels like 50 (P50), 75 (P75), and 90% (P90) were arrived at. It is observed that Repower 3.4-MW turbine performs well at both the locations. The power production from wind turbine after accounting for various losses like turbine unavailability (3%), Wake effects losses (8%), and electrical losses (5%) for Repower 3.4 MW turbine is given in **Table 1**.


**Table 1.** Performance of wind turbines at potential sites (plant load factor).

protection. Capital expenditures for offshore wind projects depend on marine vessel day rates which are uncertain, and offshore foundations require more steel for jackets and pilings than onshore foundations. The components that affect the capital cost of wind turbine are (1) wind turbine and its installation, (2) substructure and its installation, and (3) electrical systems and

Offshore Wind Feasibility Study in India http://dx.doi.org/10.5772/intechopen.74916 153

The capital cost is modeled with hypothetical 170-MW wind farm composed of 50, 3.4-MW turbines. The turbine data available in open source are considered (Repower) for this study. The farm considered in shallow water of 10–15-m water depth with a 5-m diameter monopile with 100-mm thick and 30-m penetration into seabed. The cost of various components, operation and maintenance cost, is considered as per existing wind farms and modified to Indian

The primary capital cost for onshore wind projects is the turbine; installation costs make up about 14% of the total capital costs. For offshore wind projects, the cost of installation is higher, approximately 20% of the total costs, and the costs of building the foundations account for another 20% of capital costs. For offshore wind, operation and maintenance costs make up a larger proportion of the overall components of the COE. This is likely due to the costs of accessing offshore wind farms and maintaining turbines in operating condition. The components considered are substructure, transition piece, wind turbine, installation of the above three components, inner array and export cables laying, and offshore substation installation [1, 14–19].

One of the most significant challenges facing offshore wind engineers is the effective and costefficient fixing of the turbine tower to the seabed. To date, this has typically been achieved via a monopile foundation which constitutes approximately 20–25% of the total capital expenditure in offshore wind farm construction. In this study, monopile- and gravity-based foundations are considered for capital cost estimation. For substructure and transition piece fabrication, Rs. 200/− per kg is considered based on the market studies for monopile and Rs. 25,000/− per

The wind turbine itself is the most important cost component of an offshore wind project constituting from 30 to 40% of the total capex. Here, the turbine cost is considered based on interaction with the Original Equipment Manufacturers (OEMs). A range of interacting drivers will affect costs into the future, like increasing competition, competing markets, innovation, scale effects, and standardization before drawing conclusions about the overall scale and

Foundation, turbine, substation, and cable installation together comprise approximately 20% of overall capex. At present, no offshore wind projects have been developed or are under construction in India, and since there is no direct Indian experience to draw upon, a comparative

cubic meter for gravity foundation (including concrete reinforcement and handling).

its installation (inner array cables, export cables, and substation).

conditions, which is explained in detail in subsequent sections.

**3.1. Substructure and transition piece**

trajectory of change to turbine costs.

**3.2. Wind turbine**

**3.3. Installation**

**Figure 5.** Installed LiDAR at Gulf of Khambhat for MNRE-NIWE.

The wind resource assessment is proposed to be validated with LiDAR-based data collection platform. These platforms were designed and successfully installed with the technical support of the National Institute of Ocean Technology (NIOT) at Gulf of Khambhat for M/s NIWE and Gulf of Kutch for M/s Suzlon to obtain wind velocities along with profiles. The platforms at Gulf of Khambhat and Gulf of Kutch have been installed in high tidal currents and poor soil conditions (**Figure 5**). The substructure (monopile) shown in **Figure 5** supports the data collection equipment/wind turbine by absorbing the environmental loads acting on it. The monopile is fabricated using the steel plates and mobilized using barges and installed at the site.
