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Integrating Renewables in a Smart Grid World: An Interview with NRELs David Mooney

By Jon T. Brock, President, Desert Sky Group, LLC

Reprinted with permission from the Smart Grid RoadShow

February 27, 2012

Renewable energy and energy storage are becoming critical components of an emerging smart grid. The ability to integrate renewables in a large scale and safe manner are a high priority in the national energy picture. The National Renewable Energy Laboratory (NREL) is at the forefront of renewable integration. Late last year at the Smart Grid RoadShow hosted by AEP, CenterPoint Energy, and Oncor in Corpus Christi, TX, NREL’s David Mooney gave utility industry executives a glimpse of its work in the area of renewable integration. I recently caught up with Dr. Mooney in his Golden, Colorado office. I trust that you enjoy the insights that Dr. Mooney and NREL have on renewable integration.

Brock: Can you discuss the role that the National Renewable Energy Laboratory (NREL) plays in the energy industry?

Mooney: NREL is the only national laboratory solely dedicated to advancing renewable energy
and energy efficiency. Backed by 34 years of scientifically driven energy innovation and approximately 2,500 employees and contractors that make up an extensive concentration of leading clean energy scientists and engineers with a wide breadth of experience, NREL
leads the way in helping meet the growing demand for clean energy.

NREL is the heart of America’s rich history of clean energy discovery and accomplishment – in energy science, energy technology development, and technology commercialization. Our mission is to meet national energy challenges by delivering cost effective solutions. Our fundamental scientific research is aimed at achieving breakthroughs to transform renewable energy and energy efficiency technologies. Our understanding of systems engineering and energy markets makes us uniquely suited to integrating new energy technologies into a stronger, smarter national energy system.

Brock: Please give our readers a "state of renewable integration" along with the issues you see.

Mooney: Integrating large-scale wind and solar power is ongoing, but to different degrees around the country and world. Many grids today are successfully managing high penetrations of wind and solar. During periods of low electric demand and high wind, instantaneous percentages have reached more than 50% in Colorado, Ireland, Portugal, and Spain.

To maintain the reliability we’ve all come to expect, the variability and uncertainty of renewable generation requires the remainder of the power system to be more flexible in response. Additional flexibility can come from quick-start and ramp generators (such as gas and hydro), demand control, advanced renewable resource forecasting, and electrical and fuel storage. In addition, advanced, grid-friendly features such as frequency support, low- and high-voltage ride through, and active VAR control can be incorporated in wind and solar power plants. At an incremental additional cost, these features allow more secure and reliable grid operations during fault events or other emergencies. Finally, increased use of renewable power has an impact on transmission because the best resources are location-dependent and the “fuel” can’t be transported. Therefore, many networks may require expansion to reliably achieve higher renewable levels. Transmission is inexpensive relative to capacity additions, but multi-jurisdictional issues, cost allocation, and long planning and permitting horizons can be difficult. Some progress has been made with proactive transmission by designating renewable energy zones. NREL, along with multiple partners, is aggressively researching theses issues and developing methodologies to cost-effectively integrate greater penetrations of renewable and demand side technologies.

Brock: How does NREL forecast renewable resources?

Mooney: NREL’s focus is not on directly forecasting wind and solar resources, but on developing the underlying science and techniques that allow private companies to deliver forecasting services to wind/solar power plant and utility operators. As a research laboratory, NREL works to develop new forecasting methods and improve existing weather forecasting and models with the intent of reducing the uncertainty of renewable plant output and thus reduce the cost of integrating renewables on the grid. Because wind and solar forecasting research and development requires significant investments, NREL partners with other government agencies such as NOAA, academic institutions such as Colorado State University, University of Colorado and University of California San Diego, as well as with private forecast providers such as Windlogics, AWS Truepower and 3Tier. We also partner with various utilities, system operators and plant operators. NREL also collaborates on forecasting research with a large number of international researchers, especially in Europe, to improve solar and wind forecasting. These partnerships provide significant leveraging and cost savings to U.S. taxpayers while also getting top national and international experts to work together on a difficult problem.

Brock: Can you enlighten us on the impacts of distributed generation and storage applications?

Mooney: Significant amounts of variable and uncertain renewables (non-dispatchable) distributed generation is currently being interconnected into the electricity grid. Large-scale deployment of distributed renewables will likely result in the need for more system flexibility than is currently utilized. As penetration levels of PV, for example, increase on distribution circuits, this variability could compromise power quality and service reliability. Questions that need to be addressed as penetration levels increase include:

- At what penetration levels and technology mixes will the distributed generation need to be monitored and ultimately controlled?

- How can distributed generation be controlled – externally via control signals from a centralized controller or autonomously based on power quality and/or flow sensing?

- To what extent can load management be used to mitigate or eliminate the need for control of distributed generation or for the addition of storage?

- To what extent can energy storage be used to mitigate or eliminate the need for control of distributed generation? How can the energy storage itself be controlled?

- What are the highest value uses for storage?

o Frequency regulation

o Variability smoothing

o Peak shifting

NREL is currently addressing these issues along with its partners from utilities, industry, academia, and governmental research institutions.

Brock: It is my understanding that NREL has a new integration laboratory under construction. What can you tell us about it?

Mooney: NREL’s Energy Systems Integration Facility (ESIF), scheduled to be substantially complete by fall 2012, is designed to help address challenges and reduce risks of incorporating new energy technologies into America’s electricity delivery system. Research, development, and testing conducted in the ESIF will aim to overcome a variety of challenges facing our nation’s energy system. These include challenges related to integrating higher levels of renewable energy into the electrical grid, developing advanced fuels such as hydrogen, evaluating the use of advanced energy storage technologies, and advancing electrification of the transportation system.

The 182,500-ft2 facility will house approximately 200 scientists and engineers, 15 fully equipped laboratories, several outdoor test areas, and a high performance computing data center with the fastest computing system solely dedicated to energy efficiency and renewable energy technologies in the world. The laboratory will allow for rapid configuration of a variety of energy systems to conduct experiments in a controlled environment at meaningful power levels up to 2MW.

This state-of-the-art facility will enable NREL and industry to work together to develop and evaluate their individual technologies on a controlled integrated energy system platform. Participation from utilities, equipment manufacturers, renewable systems integra­tors, universities, and other national labs and related industries that fully utilize ESIF’s capabilities will dramatically accelerate the research required to transform the energy system to one that is cleaner, more secure, and more reliable, with less risk.

Brock: What are the trends for renewable energy moving forward in the near to mid-term?

Mooney: Several trends for renewables will continue to emerge in the near and medium term. We're going to continue to see large, utility-scale renewable deployments. Considerable new wind build outs, very large scale concentrating solar power, and more and more very large scale PV plants will continue to come on line as system prices continue to fall. These deployments will be driven in the near term primarily by state portfolios standards and facilitated by production and investment tax credits. NREL and others will continue to work with utilities and systems operators to enable the reliable operation of the system under high penetrations of variable generation. While these large-scale deployments continue, many new trends will emerge at the other end of the system – in the distribution system. There is likely to be more and more distributed generation deployed and integrated into the system at homes and businesses. Currently most utilities look at PV, for example, as a demand reduction technology. But there are some circuits in specific areas that are seeing penetration levels high enough to cause distributed PV to be viewed as generators, not just demand reduction. It’s in the distribution system where there are likely to be the biggest changes in the future. In addition to increases in distributed generation, there is likely to be increases in electric and plug-in hybrid vehicles along with smart grid development. Some early studies show, for example, that the uptake of electric and plug in hybrids vehicles in the market is not going to place a huge burden on central generating assets, but could cause stress on the distribution infrastructure depending on the geographic distribution and charging habits of vehicle owners. Much of this technology could enable (or require) a more active operation of the distribution systems, which would certainly be a significant change. All these new technologies coupled with changing pricing structures could lead to a tremendous amount of customer choice that could drive how technology gets adopted into the distribution system.

Brock: I'm certain that a lot of these new scenarios moving forward will end up in your integration laboratory?

Mooney: Absolutely, that's really the motivation for the new lab. We're trying to anticipate what new systems scenarios might be likely so we can configure and operate those systems in a controlled environment. In this way we can work the kinks out of the physical configurations and controls and greatly reduce the risks for new technology adoption prior to systems being deployed and interconnected. Of course this work will be done in close collaboration with equipment suppliers, utilities, systems operators, and potential end users. A good example of this is in the area of microgrids. There is a wide diversity of interests in microgrids, from utilities offering reliability services to the Department of Defense looking to energy security at their fixed bases. In the ESIF, a megawatt scale microgrid can be configured with multiple generation sources, different demand profiles, and multiple storage technologies. This type of system can be configured and run at full power in the lab where the control systems can be validated in both grid-tied and isolated configurations. The utility or DoD base will then be able field the validated system with full confidence that it will perform as designed.

Brock: Thank you, Dr. Mooney, for your valuable insights on renewable integration. We look forward to continuing this dialogue and others related to the smart grid in St. Petersburg at the Smart Grid RoadShow in April.

Mooney: You are welcome, Jon. I’m looking forward to it.

Dr. David Mooney, Director of the Electricity, Resources, and Building Systems Integration Center at the National Renewable Energy Laboratory (NREL) in Golden, Colorado. NREL is the U.S. Department of Energy’s primary laboratory for research and development of renewable energy and energy efficiency technologies.

Jon Brock is President of utility and energy advisor Desert Sky Group, LLC. Jon is also a member of the SGRS Program Advisory Committee. He can be reached at

1 comment | Add a New Comment
1. Timothy | May 20, 2012 at 10:01 AM EDT

As renewable engrey home systems become more popular, will DC powered devices make a comeback?AC was introduced to transfer electricity more efficiently over long distances, it wouldn't really be needed in a home system. Since most home systems produce DC, it gets turned to usable AC with a significant loss of engrey.So, do you think we will start seeing a growing DC power section in the area of electric powered devices in stores?

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