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Energy Systems Integration Newsletter - January 2017

A monthly recap of the latest happenings at the Energy Systems Integration Facility and developments in energy systems integration (ESI) research at NREL and around the world.

Photo of a solar array.

Tests Show Large Solar Plants Can Balance a Low-Carbon Grid

In recent years, NREL has performed or contributed to a number of studies that address how the electric grid will operate with larger percentages of renewable energy, including low-carbon grids that may lack the inertia traditionally provided by large, spinning, steam-driven generators. The use of smart inverters for distributed energy resources has played a major role in some of these studies, and a new series of tests extends that approach to an entire 300-MW photovoltaic (PV) plant. Under a California Independent System Operator (CAISO) project with PV manufacturer First Solar and NREL, First Solar designed an advanced plant-level controller, allowing the plant to respond to grid signals as a unit.

The tests examined how the PV plant could support the grid in three critical areas: frequency control, voltage control, and ramping capacity. Perhaps the most unexpected and significant benefit was the agile voltage support offered by the PV plant both when it was generating during the day and at night when it was not generating power. At night, the plant can absorb a small amount of power from the grid, providing the reactive capability needed to support grid voltage.

The findings indicate that renewable energy could be integrated into electric grids at a much higher level and faster pace than once believed. The CAISO Board of Governors in December noted the findings as groundbreaking for advancing renewable energy integration, and they directed staff to develop market mechanisms to take commercial advantage of the advanced inverter technology. CAISO will also evaluate its solar fleet to determine the amount of existing capacity capable of providing essential reliability services. The test results will be presented to the North American Electric Reliability Corporation and other technical review committees. The report and associated fact sheets are posted on CAISO's Clean, Green Grid Web page.

Raytheon and NREL Joint Project Wins "Project of the Year" Award from ESTCP

The U.S. Department of Defense's Environmental Security Technology Certification Program (ESTCP)—the department's environmental technology demonstration and validation program—named a joint NREL and Raytheon project as the winner of its 2016 Project-of-the-Year Award for Energy and Water. The project involved integrating an advanced zinc-bromide flow battery and microgrid control technologies with the infrastructure at Marine Corps Air Station Miramar, located north of San Diego, California.

The project successfully demonstrated the microgrid controller's ability to integrate and control the flow battery, photovoltaic (PV) system, and facility loads while connected to and islanded from the grid. The technology was able to manually increase and decrease the building load by more than 50% during islanding, and the flow battery was able to store off-peak energy and discharge approximately 100 kW for nearly 3 hours during peak demand. Although the demonstration did not meet the success criteria for the islanding duration, the system was able to power the building from the PV array and flow battery alone for more than 5 hours. At its peak output, the PV array provided more than 75% of the facility's power.

New Report Could Ease the Pain of High PV Penetrations for China

The United States has a relatively long history of interconnecting solar photovoltaic (PV) systems to its electric grid, with state net metering policies dating back to 2000 and some early-adopter installations occurring before then. State interconnection standards followed later, starting around 2002. In contrast, China's domestic PV market was virtually nonexistent in 2010, but as of 2015, the country had installed a cumulative 35 GW of PV, with plans to install another 18 GW in 2016–2017.

With China's PV market growing rapidly, a new NREL report compares the PV interconnection standards in China to those in the United States, specifically reviewing the metrics for characterizing distribution networks with significant penetrations of PV generation. The report provides some suggestions for future revisions to China's PV interconnection standards and requirements, such as limiting the ramp rates of PV power plants. See "Comparative Analysis and Considerations for PV Interconnection Standards in the United States and China," which was funded under the U.S.-China Renewable Energy Partnership through the International Team at the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy.

DOE Publishes Guide to Cybersecurity for Small and Under-Resourced Utilities

Small and under-resourced utilities operate on strict budgets as they strive to keep rates low, but modern business demands call for greater reliability and resilience from the electric grid, which leads these utilities to increase the automation on their grids; however, each digitally controlled device or system that is added to the grid can potentially serve as a point of cyberattack. A new guide produced by NREL provides a structured process by which these utilities can decide which cyber controls to apply as they are, which to adopt with significant modifications, and which to defer. Download the guide on the Energy Department web site.

IEEE Article Examines How to Estimate Photovoltaic Hosting Capacity on Distribution Feeders

How much photovoltaic (PV) capacity can be added to a distribution feeder? And what are the best control techniques, locations, and inverter settings to maximize that capacity? NREL researchers looked at these questions by modeling and analyzing 17 real utility distribution feeders and developing a management approach that maximizes the feeders' ability to host PV power. Read the full paper "On Distributed PV Hosting Capacity Estimation, Sensitivity Study and Improvement" as published in IEEE Transactions on Sustainable Energy.

EERE Blog Tips Hat to NREL Solar Forecasting Study

A late-December posting on the Energy Department's Office of Energy Efficiency and Renewable Energy blog mentioned a 2015 study by NREL and IBM that found that more accurate day-ahead predictions of solar energy generation levels would save ratepayers in California $5 million in avoided costs. The blog—written by Tassos Golnas, technology manager of the SunShot Initiative—announced a new funding opportunity for solar forecasting, with the aim of providing predictions up to two days in advance. See the EERE blog post.

ESIF Verifies the Water Savings of Johnson Controls' BlueStream Hybrid Cooling System

Johnson Controls developed the BlueStream Hybrid Cooling System to help customers address water challenges in facilities through more efficient cooling-tower operations. BlueStream features thermosyphon hybrid cooling to reduce water consumption in traditional cooling tower systems by 25% to 80% compared to all-evaporative heat-rejection systems. Used in conjunction with a traditional cooling tower, the BlueStream system offers "dry" cooling through a thermosyphon process in which refrigerant circulates naturally, with no need for a pump or compressor. Johnson Controls partnered with NREL and Sandia National Laboratories to install BlueStream at the Energy Systems Integration Facility's (ESIF's) 1-MW data center, where it is projected to save 1 million gallons of water each year. See the Johnson Controls press release.

NREL and EPRI Validate Grid-Interactive Microgrid Controller for Resilient Communities

NREL is collaborating with the Electric Power Research Institute to validate the performance of a Spirae-developed advanced microgrid controller capable of managing 1–10 MW of aggregated generation capacity. NREL is validating and testing the functions of the controller in the Energy Systems Integration Facility by connecting it to a real-time digital simulator (RTDS) model of a microgrid. The controller is also being connected to a utility-scale battery inverter that interacts with the RTDS model through an AC power amplifier, adjusting its output to the simulated electric grid voltage at the point of connection. In effect, this adds a utility-scale battery to the modeled microgrid. The controller is undergoing detailed testing to verify that it meets the technical functional requirements for one targeted community.

Kilowatt Labs to Validate a Full-Scale Microgrid Application of its Centauri Energy Server

Kilowatt Labs is bringing their Centauri Energy Server, a modular, power electronics, and energy distribution device to the Energy Systems Integration Facility (ESIF) for validation in a full-scale microgrid. The Centauri Energy Server, which features an integrated Sirius battery system, can draw on multiple energy sources. The ESIF testing will demonstrate how the server can provide 300–400 kWh of power to an installation during the course of more than 10 hours a day (5 with sun and 5 without) while operating independently of any fossil-fueled source, handling surge loads, and switching seamlessly among multiple energy sources.

INTEGRATE Project Wraps Up

All five partnerships that NREL was managing under the Integrated Network Testbed for Energy Grid Research and Technology Experimentation (INTEGRATE) project have now been completed. INTEGRATE was a $6.5-million, cost-shared project between the U.S. Department of Energy (DOE) and industry partners that aimed to enable the nation's electric grid to handle increasing amounts of renewable energy. INTEGRATE technologies should allow renewable energy systems and other clean energy technologies to be connected to a smart power grid in a "plug-and-play" manner, similar to how computers automatically connect to new devices plugged in by the users. INTEGRATE is part of the DOE Grid Modernization Initiative. See a summary of the INTEGRATE project on the Energy Systems Integration Facility website.

Save the Date: Siemens-OMNETRIC Industry Day at the ESIF on March 22

Please join us on March 22 at the Energy Systems Integration Facility (ESIF) for the Siemens-OMNETRIC Industry Day workshop and technology demonstration featuring the Siemens-OMNETRIC Microgrid Communications and Grid Edge Energy Management system, which was developed under the U.S. Department of Energy's Integrated Network Testbed for Energy Grid Research and Technology Experimentation (INTEGRATE) project. The technology incorporates innovative grid-edge control communications and a control platform using Siemens' Microgrid Management System and an Open-Field Message Bus framework. The new framework enables the electric grid to effectively support large-scale and complex operations, addressing interoperability with equipment and systems operating on the grid.

Participants will receive an overview of INTEGRATE; listen to presentations by OMNETRIC, CPS Energy, Duke Energy, University of Texas at San Antonio, and Siemens; and get a tour of NREL's unique ESIF laboratories. Following the demonstration, a brainstorming session will be held on feedback and future project development. Register for the free Siemens-OMNETRIC Industry Day on the event webpage.

Stop by Our booth at DistribuTECH

DistribuTECH is underway right now in San Diego, California, and we're there! If you're attending, stop by Booth #2152, located in the northeast corner of Hall F, and be sure to say hi!

ESI Researcher Had the Most Read Article on ResearchGate's Engineering Education Site

Dr. Ben Kroposki's paper "The sun also rises" was the most-read article on ResearchGate's Engineering Education site (logon required) for a week in late January, and it has now been read nearly 5,600 times via ResearchGate. This article discusses how wind and solar power and other renewable energy sources are an important part of any present-day energy system, and the portion of energy they supply is certain to be increasing over the next few years. With large-scale wind power reaching technological maturity, and with more than 100 GW of capacity installed, ample experience exists on integrating wind systems. With solar technologies, substantial research and development investments are being made to achieve parity with retail electricity costs in the near future. As this happens, annual capacity additions of solar power will become significant. Although the experience gleaned from the grid integration of wind power will certainly be helpful, integrating the sizable capacities of solar power will present a new set of challenges and opportunities. The article was originally published in the May–June 2009 issue of IEEE Power and Energy Magazine. See the online version on the IEEE website (subscription required).

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