INTRODUCTION

The IEA Wind member countries contain about 450 GW of hydropower capacity and more than 31 GW of wind generation. Integrating these two renewable resources for the benefit of consumers is an idea being pursued in several countries. Attendees at an IEA Wind Topical Experts Meeting in 2003 expressed the need for research activities to be conducted under the auspices of the IEA Wind agreement. In response, a proposal for Task 24 Integration of Wind and Hydropower Systems was approved by the ExCo in May 2004. This cooperative research effort will operate for four years, ending in May 2008, and offers participating organizations a way to multiply the experience and knowledge gained from individual efforts. In addition, the IEA Wind Task 24 works in cooperation with the IEA Hydropower Implementing Agreement, which is investigating integration of hydropower and wind through a complementary set of investigations.

The Task has two primary purposes.

a) To conduct cooperative research concerning the generation, transmission, and economics of integrating wind and hydropower systems, and
b) To provide a forum for information exchange.

The following are specific objectives of the Task:
• Establish an international forum for exchange of knowledge, ideas, and experiences related to the integration of wind and hydropower technologies within electricity supply systems
• Share information among participating members concerning grid integration; transmission issues; hydrological and hydropower impacts; markets and economics; and simplified modeling techniques
• Identify technically and economically feasible system configurations for integrating wind and hydropower. Include the effects of market structure on wind-hydro system economics with the intention of identifying the most effective market structures
• Document case studies pertaining to wind and hydropower integration, and create an on-line library of reports.
The objective of the Task will be achieved through at least four activities: Grid Integration Case Studies; Hydrologic Impact Case Studies; Market and Economic Case Studies; and Simplified Modeling of Wind-Hydro Integration Potential. While many case studies may involve all four of these topics, some countries that participate in this Task may only address and share information related to one. In addressing each case study topic, information exchange amongst the collaborators will address problem formulation and assumptions, analysis techniques, and results.

The following are expected outcomes of the Task:
• Identifying feasible wind/hydro system configurations
• Identifying and developing techniques to analyze grid integration of wind energy, especially as pertains to grids that include hydropower
• Understanding the capacity of wind energy that can be supported by hydropower in terms of the ancillary services
• Understanding the potential for energy storage
• Understanding the technical constraints and limiting parameters in wind and hydropower integration.

RESEARCH ACTIVITIES

Grid Integration Case Studies

Given the wide variety of hydropower installations, reservoirs, operating constraints, and hydrologic conditions, combined with the diverse characteristics of the numerous electrical grids (control areas), there are many possible wind/hydro integration combinations and many possible solutions to issues that arise. Figure 1 illustrates two of the many potential configurations for wind and hydropower integration within a transmission control area. Hydro generators typically have very quick start-up and response times and may have flexibility in water release timing. Therefore, hydro generators may be ideal for balancing wind energy fluctuations or for energy storage and redelivery. Studying the grid integration of wind energy, particularly on grids with hydropower resources, lies at the heart of understanding the potential for integrating wind and hydropower resources. Since this type of case study is fundamental, it is expected that all countries participating in the Task will contribute with at least one case study.

Hydrologic Impact Case Studies

Depending on the relative capacities of the wind and hydropower facilities, integration may necessitate changes in the way hydropower facilities operate. These changes may affect operation, maintenance, revenue, water storage, and the ability of the hydro facility to meet its primary purposes. Beyond these potential changes, integration with wind may provide benefits to the hydro system related to water storage or compliance with environmental regulations (e.g., fish passage), and create new economic opportunities. Without a proper understanding of these and other impacts and benefits, it is unlikely that many hydro facility operators will be interested in integrating with wind power. Thus, study of these impacts on hydropower facilities and hydrological operations to determine the benefits and costs could help pave the way for implementation of wind-hydro projects. Because of the requirements necessary to study hydrologic impacts, such as a hydroelectric operator or planner, it is expected that about half of the participating countries will contribute to these studies.

Market and Economic Case Studies

While grid integration and hydrologic impact studies may demonstrate the technical feasibility to integrate wind and hydropower systems, implementation will depend upon the economic feasibility of a given project. Such economic feasibility will depend on the type of electricity market in which the wind-hydro integration project is considered. Addressing economic feasibility in the electricity market will provide insight into which market types are practical for wind-hydro integration, as well as identify the key factors driving the economics. Using this understanding, there may be opportunities to devise new methods of scheduling and pricing that will be advantageous to wind-hydro integration and permit better utilization of system resources. These market and economic case studies will address the effects of today’s market structures on wind-hydro system economics with the intention of identifying the most effective market structures. Economic studies that consider the value of wind energy generation to the electricity customer during low-hydro years and extended droughts may also be investigated. Because economic feasibility is germane to the integrating wind and hydropower, it is expected that all participating countries will contribute to these studies.

Simplified Modeling of Wind-Hydro Integration Potential

Simplified methods for approximating the amount of wind power that can be physically or economically integrated with existing hydropower generation should be devised based on the characteristics of the local transmission control area loads, hydropower facilities, and the wind power resource. The analysis methods should include only the most influential operational constraints for hydro and electric reliability concerns. The goal is to develop a technique to approximate the potential for integrating wind and hydropower, without the need to conduct an in-depth study. However, any simplified method must still take a “system-wide” perspective, with the understanding that wind and hydropower interact within a larger grid that includes other generation resources. Because of this, it may be more fruitful for some investigators to consider simplified methods that study how much wind can be integrated in a large interconnected grid that includes significant hydropower resources, but not to consider specific hydropower resources. It is expected that one-quarter to one-third of the participating countries will contribute to the simplified modeling.

As the breadth of these case studies indicate, integrating wind and hydropower can be quite complex. An illustration providing a conceptual view of the relationships between wind, hydropower and the transmission control area along with “surrounding” issues is provided in Figure 2. A major accomplishment of this Task will be a database of case studies conducted through cooperative research of the Task participants, primarily for use by the Task participants.

STATUS AND PLANS

The following countries had committed to participating in the Task by the close of 2004: Australia, Canada, Finland, Norway, Sweden, Switzerland, and the United States. A kick-off meeting was planned for February 2005 at Hoover Dam, Boulder City, Nevada, United States, to initiate the collaborative work of the Task participants.
Author: Thomas L. Acker, NREL, United States

Figures 1a and 1b Two possible configurations for wind and hydropower integration within a transmission control area

Figure 2 A conceptual view of the relationships between wind power, hydropower, and the transmission control area, and the issues surrounding their integration.