Technical Summary

Wind is an intermittent but predictable resource.   Good sites have average annual wind speeds of 6.0 meters/sec (13 miles/hr) or greater, and accurate, multi-year wind speed data is critical to determining the economic feasibility of a wind project. 

Wind is a modular technology and wind farms can be erected quickly.   Most common wind turbines in commercial operation average 600 kW in power capacity.   However, and shown in the figure¹ , wind turbine sizes have increased dramatically in recent years, and this technology development has resulted in continued improvements in efficiency and reduced costs.  The newest trend is the development of turbines for offshore deployment. 

Wind turbines are very reliable and have availabilities greater than 95 percent.   Wind farm capacity factors range from 20 to percent at average wind sites to more than 40% at the best sites.   Possible environmental issues include, visual, cultural, land use, and bird impacts, and noise.   Planning approval and environmental assessment are usually necessary.

While wind is very close to being strictly cost-competitive, with conventional power generating technologies, its market growth is still mainly subsidy-driven in OECD countries.

Resource Assessment

Having high-quality wind resource data is extremely valuable to a wind energy project developer or potential wind energy user because it allows them to choose a general area of estimated high wind for more detailed examination.  Several wind resource databases and maps have been developed in recent years for such purposes. 

In the US, NREL identifies and gathers data for wind resource maps of the United States and foreign countries.  This information is maintained by NREL in the National Wind Technology Center, http://www.nrel.gov/wind/wind_pubs.html,, which provides the following wind resource data and links:

• Wind Resource Bibliography
• National Climatic Data Center Wind Speed Data
• Wind Maps of the United States including seasonal wind maps
• Wind Maps for all 50 State and US territories
• International Wind Resource Maps and databases for 14 countries
• Wind Resource Assessment Handbook 
• Wind Energy Potential paper, which describes how much electricity could be generated from wind in the United States.

In Europe, the Database of Wind Characteristics (http://www.winddata.com/) is compiled and maintained by the Technical University of Denmark (DTU) together with Risø National Laboratories.   This database contains four different categories of wind data: time series of wind characteristics, time series of wind turbine responses, wind resource data and wind farm data.

The time series are primarily intended for wind turbine design purposes and the resource data can be used for siting analysis.   The database provides wind speed measurements, measured under different conditions and terrain types at 55 different locations inside Europe, Egypt, Japan, Mexico, Costa Rico and United States.

Cost, Performance and Project Risks

Installed costs for on shore wind farmstypically range between $900/kW and $1100/kW, and for off-shore wind farms the cost is typically between $1500/kW and $1600/kW.

Operating and maintenance cost typically run about one US cent/kWh.

The cost of electricity from modern grid-connected wind farms ranges from 4 to 6 US cents/kWh depending on the site and strength of the wind resource.  These wind farms generally must compete against conventional grid power options ranging from 2 to 5 US cents/kWh.

Commercial wind turbines have a proven availability factor greater than 95 percent and have very low technical risk.  However, wind farms usually require local permits and project development risks often include the need for an environmental impact assessment to mitigate any environmental issues such as visual, noise, land use, cultural problems, or impacts on birds.  Finally, a power purchase agreement is necessary for grid-connected wind farms, and delays in these processes often constitute the greatest risk to a developer.

There is a strong potential for local manufacturing of many wind turbine components depending upon the technical capacity of the country.  Simple components include the steel towers, transformers, wiring and nacelle housings.  More highly machined components include the generator, gearboxes and bearings.  The most sophisticated components include the control structures and blades, and these are generally imported.

Standards and Certification

Design standards and certification assure that a wind turbine is sound, safe, and has been manufactured and constructed with good engineering practice. Standards need to continuously be updated to reflect the best knowledge on engineering practices and experience obtained over recent years. Having internationally recognized standards creates a level playing field in the market place and assures that every turbine meets a minimum level of safety.  

International standards for wind turbines are developed by the working groups of Technical Committee-88 (TC-88) of the International Electrotechnical Commission (IEC), the recognized international body for standards development activities.  These standards cover the following topics, and more information on them can be found at the American Wind Energy Association (AWEA) web site.  The standards can be purchased directly from IEC or through the American National Standards Institute .

• IEC 61400-1 Wind Turbine Safety and Design
• IEC 61400-1 Ed2 Wind Turbine Safety and Design Revision
• IEC 61400-2 Small Wind Turbine Safety
• IEC 61400-11 Noise Measurement
• IEC 61400-12 Power Performance
• IEC 61400-13 Mechanical Load Measurements
• IEC 61400-21 Power Quality
• IEC 61400-22 Wind Turbine Certification
• IEC 61400-23 Blade Structural Testing
• IEC 61400-24 Lightening Protection

AWEA is the recognized U.S. industry organization for standards development and maintains contact with the IEC standards development activities through the involvement of staff members and industry representatives on TC-88 standards subcommittees.

New standards are under development by IEC, IEEE, and AWEA, which will update or create technical requirements and design technique. NREL is creating guidelines on how to implement the standards for use by industry.   The key to effective standards is providing adequate consumer and safety protection while avoiding creation of market and economic barriers.

Several certification programs have been established in the United States and Europe.  In the US, NREL has set up a certification system in the in partnership with Underwriters Laboratories (UL).   IEC Standards are used as the basis for this certification program.

In Europe, DNV Wind Turbine Certification provides certification services for both wind turbine types as well as on-shore and off-shore wind farms.  DNV offers certification worldwide, and holds a wide range of national accreditations.

Grid Interconnection

Much work has been done to develop US and European interconnection requirements and standards.  IEC Standards and Definitions do exist and most wind turbine manufacturers have technical interconnection criteria called “Electric Grid Data”.   In the US, the National Wind Coordinating Committee² (NWCC) is attempting to standardize interconnection procedures in US, and the US Federal Energy Commission (FERC) Rule dated 23.07.2003promotes an interconnection standard for large (>20 MW) wind plants.   However, there are many site-specific aspects to grid interconnection, and the process for developing grid interconnection is illustrated in the figure below³ .

Wind Power Plant Grid Interconnection Process

Various aspects of the grid interconnection process can be further explored through the following links:

• US Department of Energy Wind and Hydropower Interconnection Standards http://www.eere.energy.gov/windandhydro/windpoweringamerica/ne_policy_netmetering.asp
• PJM Generation and Transmission Interconnection Studies, Main Manual, http://www.pjm.com/documents/downloads/manuals/generation-and-transmission-interconnection/m14Av1.pdf
• PJM Sample Interconnection Feasibility Study, http://www.pjm.com/services/trans/form-oatt-feas-study.html
• PJM Sample Interconnection Impact Study, http://www.pjm.com/planning/form-impact-study-data.html
• PJM Sample Facility Study, http://www.pjm.com/services/trans/downloads/20010313-facilities-study.pdf

Intermittency

Wind is an intermittent resource, and compared to conventional generators, a wind power plant’s output is relatively uncontrollable, unpredictable, and variable.   This is generally not a concern when the contribution from wind is small.  However, as wind becomes a larger share of total generating capacity, issues related to its integration with utility grid operations and markets are becoming increasingly important.

Such integration of wind is qualitatively different from that for other types of generators because wind output depends on whether, when, and how hard the wind blows.   Because of these characteristics and because electric-system operators have little experience with wind facilities, considerable disagreement can exist regarding the costs of integrating wind into electric grids.

As the total contribution from wind becomes significant (generally believed to be at about 10% to 15% of total system load) it can no longer be considered to be largely invisible (and therefore cost free) to a large electric grid.   On the other hand, every unscheduled megawatt movement of a wind farm does not necessarily need to be offset, megawatt for megawatt, by some other resource.

New quantitative methods for analyzing the integration of wind resources into a large electric grid have been developed and should be applied when the total contribution from wind becomes significant⁴ .    These analyses integrate real-time data on both wind resources and the load variability of the electric grid.  It also integrates the impacts of the associated short-term competitive market for wholesale electricity.  

A key feature of the new analytical approach is its integration of wind with the overall electrical system. The uncontrollable, unpredictable, and variable nature of wind output is not analyzed in isolation. Rather, as is true for all loads and resources, the wind output is aggregated with all the other resources and loads to analyze the net effects of wind on the power system.

Aggregation is a powerful mechanism used by the electricity industry to lower costs to all consumers. Such aggregation means that the operator need not offset wind output on a megawatt-for-megawatt basis. Rather, all the system operator need do, when unscheduled wind output appears on its system, is maintain its average reliability performance at the same level it would have without the wind resource.

The results developed with this new analytical method suggest that a system operator need not acquire regulation and intra-hour-balancing resources to counter every change in output from a wind farm.  The system operator should treat wind the same way that any time-varying load or generator should be treated in competitive wholesale electricity market.  

The analysis must be performed for specific wind power plants and the electric grids they supply.  However, generalized results from early analyses indicate that:

• Scheduling wind output ahead of time (e.g., in an hour-ahead energy market) yields lower system impacts than having the wind appear entirely as intra-hour imbalance energy.
• There is significant benefit to accurately scheduling wind plant output one hour ahead, and that this benefit increases as the size of the wind facility increases. These benefits suggest that the value of accurate forecasts of wind output could be substantial.
• The average cost of integrating wind production into a system, all else being equal, increases as the size of the wind facility increases. However, this cost is generally  a small fraction of the system regulation cost.
• The magnitude of the wind integration cost depends on the correlation between the aggregated wind plant output and hourly spot prices. These results suggest that those examining alternative locations for wind farms should consider prices and revenues as well as local wind speeds.
• Market design can affect the operation and revenues of a wind farm. Penalties unrelated to system costs are unfair.  Cost should reflect real system impacts based on detailed analyses.

Wind Farm Bid Documents

The Bank/GEF China Renewable Energy Development Project provided financing for 20 MW of wind farms in Shanghai Province. The following “Standard Bidding Documents for the Supply and Installation of Plant and Equipment” were prepared for use in that project and are available in the Project Tools: Bidding Documents.  The documents follow the Bank forms for contracts involving the supply, installation and commissioning of specially engineered plant and equipment, that should be used when (i) the value of the plant and equipment portion represents the major part of the estimated contract value, or (ii) the nature and complexity of the plant and equipment is such that the facilities cannot safely be taken over by the Employer without elaborate testing, pre-commissioning, commissioning and acceptance procedures being followed.

Section I.  Invitation for Bids
Section II.  Instructions to Bidders  (Not included, should be project specific)
Section III.  Bid Data Sheet
Section IV.  General Conditions of Contract  (Not included, should be project specific)
Section V.  Special Conditions of Contract
Section VI.  Technical Specifications and Drawings
Section VII.  Sample Forms and Procedures

1.  Bid Forms and Price Schedules
2.  Bid Security Form
3.  Form of Contract Agreement and its Appendices
4.  Performance Security Forms
5.  Bank Guarantee Form for Advance Payment
6.  Form of Completion Certificate
7.  Form of Operational Acceptance Certificate
8.  Form of Irrevocable Letter of Guarantee for Warranty

Wind Farm Project Development Documents

A complete set of project development documents were prepared as part of the Medium Size Project for Developing the LEGAL AND REGULATORY FRAMEWORK FOR WIND POWER IN RUSSIA under a Grant from the International Finance Corporation (IFC) in its capacity as Implementing Agent for the Global Environment Facility (GEF).

These project development documents cover the following aspects of developing a wind farm in significant detail:

¹ Renewable Energies: Innovation for the future, Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), Public Relations Division, Berlin, 2004
² United States, National Wind Coordinating Committee, “Interconnection Issue Brief,” September 2003. 
³ Grid Interconnection And Operation For Wind Power Plants in Russia, IFC/GEF (DOC). 
⁴ Interactions of Wind Farms With Bulk-Power Operations and Markets (PDF).