Debra Lew

Annual Report on U.S. Wind Power Installation, Cost, and Performance Trends: 2006

This report--the first in what is envisioned to be an ongoing annual series--attempts to fill this need by providing a detailed overview of developments and trends in the U.S. wind power market, with a particular focus on 2006.

Creating the Dataset for the Western Wind and Solar Integration Study (U.S.A.)

The Western Wind and Solar Integration Study (WWSIS) is one of the worlds largest regional integration studies to date. This paper discusses the creation of the wind dataset that will be the basis for assessing the operating impacts and mitigation options due to the variability and uncertainty of wind power on the utility grids. The dataset is based on output from a mesoscale numerical weather prediction (NWP) model, covering over 4 million square kilometers with a spatial resolution of approximately two-kilometers over a period of three years with a temporal resolution of 10 minutes. The mesoscale model dataset includes all the meteorological variables necessary to calculate wind energy production. Individual time series were produced for over 30 thousand locations representing more than 900 GW of potential wind power generation.

The evolution of wind power integration studies: Past, present, and future

The rapid growth of wind power as a generation resource in the past decade has given many utilities and Regional Transmission Organizations (RTO) concerns due to its unconventional characteristics. Because of these concerns, many of these entities have initiated studies that evaluate the feasibility of large amounts of wind power onto their system and the operational impacts present. This paper will discuss some of the past major studies, mostly focusing on the United States, and the basic methodologies that were used during these studies. The paper will also review many of the different results and conclusions of the studies and discuss how they have helped the power industry as a whole. Lastly, the authors will attempt to share their ideas on some of the limitations of the current and past integration studies, and some insight on how these may be evolving in the future.

Integrating Variable Renewable Energy: Challenges and Solutions

In the U.S., a number of utilities are adopting higher penetrations of renewables, driven in part by state policies. While power systems have been designed to handle the variable nature of loads, the additional supply-side variability and uncertainty can pose new challenges for utilities and system operators. However, a variety of operational and technical solutions exist to help integrate higher penetrations of wind and solar generation. This paper explores renewable energy integration challenges and mitigation strategies that have been implemented in the U.S. and internationally, including forecasting, demand response, flexible generation, larger balancing areas or balancing area cooperation, and operational practices such as fast scheduling and dispatch.

Up with wind

In this article, we focus on three important aspects of large regional wind-integration studies: wind data development, transmission analysis, and the modeling of wind-integration scenarios. Careful development and validation of the wind data inputs to an integration study are essential to obtain meaningful results. New transmission will be required for much of the future wind development; hence, it is imperative to plan for this transmission because it takes longer to build new transmission than it does to build wind plants. The transmission analysis can include a transmission-expansion plan to be done as part of the wind-integration study or can use existing transmission plans and analyze potential congestion. Finally, scenario modeling investigates the operational impacts of wind variability and uncertainty. The production cost models can be either deterministic or stochastic in nature. They can examine a wide range of sensitivities.including unit commitment and operating reserve considerations, different market scenarios, carbon reductions for different scenarios, storage considerations, forecasting, and the contribution of wind to system reliability.

Assessment of Simulated Wind Data Requirements for Wind Integration Studies

Wind integration studies are now routinely undertaken by utilities and system operators to investigate the operational impacts of the variability and uncertainty of wind power on the grid. There are widely adopted techniques and assumptions that are used to model the wind data used in these studies. As wind penetration levels increase, some of the assumptions and methodologies are no longer valid and new methodologies have been devised. Based on involvement in conducting studies, reviewing studies, and/or developing datasets for studies in the Western Interconnect, the Eastern Interconnect, Hawaii, and other regions, the authors report on the evolution of techniques to better model the wind power output for cases with high penetrations of wind energy.

Operational Analysis and Methods for Wind Integration Studies

Wind integration studies are increasingly important tools to estimate the impacts that the addition of large amounts of variable and uncertain generation will have on the electricity grid. As the number of these studies has increased in recent years, the sophistication of the methods and assumptions utilized has also increased. These methods have had to evolve with increasing penetration rates and to study changing research questions. In this work, the authors report on the state of the art in this area and make suggestions for improving the methods and assumptions used for cases with high levels of wind power.

Finding Flexibility: Cycling the Conventional Fleet

Adding new generation, load, or transmission to the grid changes the operation of the incumbent power system. Wind and solar generation plants are no different, but their impact on the rest of the grid is exacerbated by the facts that wind and solar energy is nondispatchable and such generators produce variable output. And because wind and solar effectively bid into the market at very low or negative cost, they are preferred resources in the dispatch stack. They are used by system operators whenever possible, unless there are generator operating limits or transmission constraints.

Impacts of wind and solar on emissions and wear and tear of fossil-fueled generators

High penetrations of wind and solar power will impact the operations of the conventional generators on the power system. Regional integration studies have shown that wind and solar may cause fossil-fueled generators to cycle on and off and load follow more frequently and potentially more rapidly. Increased cycling, deeper load following, and rapid ramping may result in wear and tear impacts on fossil-fueled generators that lead to increased capital and maintenance costs, increased equivalent forced outage rates, and degraded performance over time. Heat rates and emissions from fossil-fueled generators may be higher during cycling and ramping than during steady-state operation. Many wind and solar integration studies have not taken these increased cost and emissions impacts into account because data have not been available. This analysis considers the cost and emissions impacts of cycling and ramping of fossil-fueled generation to refine assessments of wind and solar impacts on the power system.

Impact of High Solar Penetration in the Western Interconnection

This paper presents an overview of the variable characteristics of solar power, as well as the accompanying grid dynamic performance and operational economics for a system with significant solar generation. The paper will show results of economic operational simulations of a very high solar generation future for the western half of the United States.