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Energy Systems Integration News

February 2014

Photo of the exterior of the NREL Energy Systems Integration Facility at sunrise.

The ESIF's most frequent and reliable visitor. Photo by Ben Kroposki, NREL

Welcome to Energy Systems Integration News, the National Renewable Energy Laboratory's (NREL's) monthly newsletter designed to keep industry partners, stakeholders, associations, and educational institutes up to date on the latest energy systems integration (ESI) developments at NREL and worldwide.

In This Issue


NREL Finds Active Power Control of Wind Turbines Can Improve Power Grid Reliability

Think variable wind energy is a liability when it comes to producing reliable power? A new report from NREL may make you think again. In partnership with the Electric Power Research Institute (EPRI) and the University of Colorado, NREL has completed a comprehensive study to understand how wind power technology can actually assist the power grid by controlling the active power output being placed onto the system.

The study, Active Power Controls from Wind Power: Bridging the Gaps, finds that wind power can support the power system by adjusting its power output to enhance system reliability. Additionally, the study finds that it may be economically beneficial to provide active power control from wind energy during many instances, and potential damage loads on the turbines from providing this control are negligible. Active power control helps balance load with generation at various times, avoiding erroneous power flows, involuntary load shedding, machine damage, and the risk of potential blackouts.

The study included a number of different power system simulations, control simulations, and field tests using turbines at NREL's National Wind Technology Center (NWTC). The study also developed proposals for new ancillary services designs in U.S. wholesale electricity markets, studied how wind power affects system frequency in the Western U.S. with and without active power control, and tested the use of active power control at the NWTC to better understand the performance and structural impacts on wind turbines when providing active power control to the electric system.

Learn more about NREL's transmission grid integration research.

NREL Evaluates Accuracy of Satellite-Based Solar Resource Models

Predictions of the solar resource under clear sky conditions are now more accurate than ever, thanks to new research from NREL. The new report Evaluation of Clear Sky Models for Satellite-Based Irradiance Estimates details an intercomparison of three popular broadband clear sky solar irradiance model results with measured data, as well as satellite-based model clear sky results compared to measured clear sky data. The authors conclude that one of the popular clear sky models (the Bird clear sky model developed by Richard Bird and Roland Hulstrom) could serve as a more accurate replacement for current satellite-model clear sky estimations. Additionally, analysis of the model results with respect to model input parameters indicates that rather than climatological, annual, or monthly mean input data, higher-time-resolution input parameters improve the general clear sky model performance.

Find out more about NREL's resource assessment and forecasting research.

ESIF Commissions 1.5 MW of PV Simulation Capability

The dynamic capabilities of the Energy Systems Integration Facility (ESIF) continue to grow—in December, another 500 kilowatts (kW) of programmable direct-current (DC) power supplies were installed and commissioned at the facility, expanding its photovoltaic (PV) emulation capabilities to a full 1.5 megawatts (MW). This increased capacity will support full-power testing of commercial-scale PV inverters, as well as improve the ESIF's flexibility to support simultaneous testing of multiple devices as part of stand-alone or integrated experiments.

Check out the ESIF website to learn more about the unique capabilities of the nation's first user facility dedicated to utility-scale clean energy grid integration.

NREL Researchers Publish New Book on Power Electronics for Renewable and Distributed Energy Systems

NREL researchers have taken an integrative approach in a new book for the electric power sector. Unlike most other books that treat power electronics and renewable energy as two separate subjects, Power Electronics for Renewable and Distributed Energy Systems integrates them, discussing power electronic converter topologies, controls, and integration that are specific to renewable and distributed energy system applications. Edited by NREL researchers Dr. Sudipta Chakraborty and Dr. William Kramer and Colorado School of Mines Professor Dr. Marcelo Simões, and with contributed chapters from subject matter experts all over the world, Power Electronics for Renewable and Distributed Energy Systems will be a valuable sourcebook for electrical engineers and consultants working to deploy various renewable and distributed energy systems and can serve as a comprehensive guide for upper-level undergraduate and graduate students across the globe.

Published by Springer, the book includes an overview of power electronics technologies, followed by detailed discussions on power electronics required for various renewable and distributed energy resources, including photovoltaics, wind, small hydroelectric, fuel cells, microturbines, and variable-speed generation. Energy storage systems such as battery and fast-response storage systems are also discussed along with application-specific examples. After establishing fundamentals, later chapters focus on more complex topics such as modular power electronics, microgrids, and smart grids for integrating renewable and distributed energy. Emerging topics such as advanced electric vehicles and distributed control paradigms for power system control are discussed in the final two chapters.

Learn more about NREL's distributed grid integration research.

Controllable Grid Interface Facility Dedicated at NREL's NWTC

A new test system that could prove key to integrating more renewable power on the electric grid is now in operation at NREL. Located at NREL's National Wind Technology Center (NWTC), the 7 MVA controllable grid interface (CGI) test system has been dedicated and is now in operation. Using a combination of hardware and real-time control software, the CGI helps examine how multi-megawatt wind turbines, solar inverters, energy storage systems, and other electrical equipment interact with the power grid. The CGI can significantly reduce certification testing time and costs while providing system engineers with a better understanding of both how these devices react to grid disturbances, as well as provide various ancillary services back to the grid.

This capability allows industry to partner with NREL to test, optimize, and visualize the grid-integration-related performance of the unit under test long before it is deployed in the field, saving time and resources while minimizing integration issues. CGI is a valuable asset for the energy industry to further improve the reliability of renewable generation, and advance the development of grid-friendly features of renewable and emerging technologies. For example, CGI allows wind turbine generator manufacturers to test both the mechanical and electrical characteristics of their machines in a controlled grid environment by replicating many electrical scenarios that are only partially available in field testing. The renewable energy industry now has a platform upon which to ensure that renewable energy systems meet stringent national and international electrical standards and to test the grid compliance of innovative electrical topologies and controls—all of which will increase the reliability and lower the cost of energy delivered by wind and solar power.

Read more about NREL's CGI capability.

NREL Researchers Impact FERC Small Generation Interconnection Procedures

The impact of NREL's research is clear in a new development from the nation's energy regulatory agency. NREL researchers have had significant input into the first-ever revision of the Federal Energy Regulatory Commission (FERC) Small Generator Interconnection Procedures (SGIP). FERC released its Final Rule on November 22, 2013, which contains numerous changes based on reports published by NREL. Researchers Michael Coddington and Barry Mather were co-authors of these reports and worked closely with FERC and other organizations to bring about changes in the SGIP.

Several key changes were a direct result of recommendations in the NREL reports, including the utilization of minimum daytime load data on feeders to improve penetration screens and a fast track table that moved from 2 MW to 5 MW on some circuits. The FERC stated that the revisions will "reduce the time and cost to process small generator interconnection requests…, maintain reliability, increase energy supply, and remove barriers to the development of new energy resources." NREL collaborated with experts at the U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy (EERE), the Interstate Renewable Energy Council (IREC), EPRI, and Sandia National Laboratories on the reports.

Learn more about NREL's work in distributed grid integration.

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ESI Around the World

DOE Releases Grid Energy Storage Report

A new U.S. Department of Energy (DOE) report pinpoints the major challenges—and solutions—for developing energy storage technologies for the electric grid. As part of the Obama Administration's commitment to a cleaner, more secure energy future, Energy Secretary Ernest Moniz released the Grid Energy Storage report in December, identifying the benefits of grid energy storage, the challenges that must be addressed to enable broader use, and the efforts of DOE, in conjunction with industry and other government organizations, to meet those challenges.

FERC Energy Storage Ruling Starts to Clear Regulatory Uncertainty

Regulatory uncertainty is beginning to clear when it comes to energy storage. The recently issued Federal Energy Regulatory Commission (FERC) Order 784 sets "fast"-responding energy storage sources like batteries, flow batteries, and flywheels against slower gas- or coal-fired plants in the ancillary services market—helping to open this market for storage project developers. This ruling follows FERC Order 755, enacted in 2011, which increased the pay for fast-responding sources that are bidding into frequency regulation service markets.

Relevant language from the ruling includes: "The Commission is also requiring each public utility transmission provider to add to its OATT [open access transmission tariff] Schedule 3a statement that it will take into account the speed and accuracy of regulation resources in its determination of reserve requirements for Regulation and Frequency Response service. […] Finally, the Commission is revising the accounting and reporting requirements under its Uniform System of Accounts for public utilities and licensees (USofA) and its forms, statements, and reports…to better account for and report transactions associated with the use of energy storage devices in public utility operations."

Obama Administration Launches Quadrennial Energy Review

The White House has announced that it will establish a Quadrennial Energy Review with a key focus on energy infrastructure. As noted in the January 9 memo: "The initial focus for the Quadrennial Energy Review will be our Nation's infrastructure for transporting, transmitting, and delivering energy. Our current infrastructure is increasingly challenged by transformations in energy supply, markets, and patterns of end use; issues of aging and capacity; impacts of climate change; and cyber and physical threats. Any vulnerability in this infrastructure may be exacerbated by the increasing interdependencies of energy systems with water, telecommunications, transportation, and emergency response systems. The first Quadrennial Energy Review Report will serve as a roadmap to help address these challenges."

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Who's Who at the ESIF

DoD, Industry Groups Among December's ESIF Visitors

The Energy Systems Integration Facility (ESIF) continues to attract high-profile guests. Recent visitors include:

  • CleanTech Syndicate
  • Colorado Clean Tech Industry Association
  • Electric Utility Consultants, Inc.
  • Macedonia Delegation
  • Mika Ohbayashi, ED, Japanese Renewable Energy Foundation
  • U.S. Army's Energy Initiatives Task Force
  • U.S. Department of Defense, Tom Morehouse
  • Wells Fargo

NREL Teams with CSIRO to Research Communications for Plug-and-Play Solar Microgrid Controller

Add another name to the list of companies partnering with NREL on innovative ESI research at the ESIF. NREL has joined forces with Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) to develop a plug-and-play technology that will result in newly connected solar generation being automatically "discovered" and configured by the main generation control system. NREL will perform a review of communications protocols to identify important protocols that the plug-and-play solar microgrid controller must be compatible with. CSIRO will also collaborate with multinational engineering firm ABB on the project.

NREL will perform prototype testing of the microgrid controller in the ESIF to test the hardware's ability to manage the output power of a diesel generator in the presence of a load bank and solar simulator. The effort ultimately aims to simplify the integration, accelerate the deployment, and lower the cost of solar energy in hybrid distributed generation applications using this new plug-and-play solar technology.

Learn more about other ESIF partners and how to work with NREL at the ESIF.

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Next Up

Phasor Measurement Unit Data Report Coming Soon

NREL ESI researchers are hard at work to finalize a report on phasor measurement unit data. The U.S. power industry is undertaking several initiatives that will improve the operations of the electric power grid—one of which is the implementation of wide-area measurements using phasor measurement units to dynamically monitor the operations and status of the network and provide advanced situational awareness and stability assessment. NREL's report will present potential future applications of synchrophasors for power system operations under high penetrations of wind and other renewable energy sources. Stay tuned for more information in an upcoming issue of Energy Systems Integration News.

New ASTM Standard Under Development

With input from NREL, the new ASTM standard "Guide for Evaluating Uncertainty in Calibration and Field Measurements of Broadband Irradiance with Pyranometers and Pyrheliometers" has been put to ballot. The new standard is expected to be released in the next few months. Look to future issues of Energy Systems Integration News for more information.

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