IEEE Power & Energy Society
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Guest Editorial

Microgrids

There May Be One in Your Future

Depending on where you live, work, shop, or go to school, there may well be a microgrid in your future. A number of technical, cost, and societal factors are coming together to make microgrids the biggest driving change in the electric power infrastructure on the horizon.

  • The cost of distributed generation is continuing to drop and is competitive with grid-supplied power in many regions.
    • Photovoltaic panels and inverters continue to decline in cost.
    • Clean natural gas-fired diesel generation is inexpensive because of very low gas prices.
  • Electricity prices in some regions in the United States, especially in the Northeast and California, remain high.
  • Environmental restrictions make older backup generation less attractive.
  • Grid reliability is perceived as unsatisfactory in regions with bad weather and lower customer density.
  • Storms such as Katrina, Irene, and Sandy have heightened the need for local back-up power to withstand multiday outages, especially for any load that is critical to public safety, health, and welfare.
  • The costs and complexities of microgrid design and grid interconnection are being addressed via numerous pilot projects.
  • Some states have measures that require, encourage, or support microgrid development.
  • Retail access to wholesale markets can create improved economics for microgrid operations.
  • The penetration of grid interconnection of high renewables drives the need for more control of distributed resources and is another microgrid driver.
  • The U.S. Department of Defense (DOD) is actively pursuing microgrids as a means to achieve energy surety, security, and economics at military facilities nationwide.

There is enough activity in the microgrid world today that multiple market research studies are out there, touting billions of dollars of microgrid business over the next few years.

Microgrids have been in existence at some universities and large medical campuses for decades. The Galvin Institute at Illinois, for instance, has had a microgrid for some years, and Cornell University has operated a campus microgrid for 30 years. Facilities like these were built around campus cogeneration plants that were capable of selling excess power to the grid at a wholesale level and were able to maintain electrical supply to the campus in the event of a grid outage. Combined heat and power facilities helped make the economics work. These facilities used waste heat from combustion turbines and/or combined cycle generators.

In more recent years, other generation technologies, especially photovoltaic and also small-scale wind or clean diesel, have entered the mix. In the past five years the U.S. Department of Energy (DOE) has dramatically increased the total effort in technology development and demonstration to include advanced technologies like energy storage, improved power electronics, control systems, and market interactions. Advanced demand management systems including building automation systems, control of smart charging for electric vehicles, and possibly process control of industrial processes all play a role.

Having set the stage for the importance of microgrids in the context of smart grid development, we have ventured to devote this issue to this topic. The articles contained within will help provide the reader with an excellent overview of the technologies and approaches for next generation of microgrids.

The seven articles and the “In My View” column in this issue are authored by leading experts. We will present the highlights of these articles to capture a quick summary of this issue.

The first three articles by the DOE, the University of California at San Diego (UCSD), and Southern California Edison (SCE) all describe “civilian” microgrid efforts and focus on technology proof of concept/demonstration and evaluation programs.

The first article, by Merrill Smith and Dan Ton of the DOE, emphasizes microgrids as a key building block for a smart grid and describes how the DOE has established microgrid R&D as a key focus area. According to the authors, “A significant number of R&D needs and challenges have been identified for microgrids during the two recent workshops, with input from more than 170 experts and practitioners representing a broad group of stakeholders in the United States and other countries such as Europe, Japan, Korea, and Canada. Also evident from workshop discussions and presentations are the technical, economical, societal, and environmental benefits that can result from successful development and deployment of microgrids.

“Engaging stakeholders and knowledgeable practitioners to seek input on R&D needs is a key part of the R&D topic development process. With the input collected, the program will further refine R&D requirements to plan and develop a competitive funding opportunity announcement (subject to available DOE funds). The DOE microgrid R&D initiative hopes to advance microgrids, in partnership with industry and research experts, from conception through R&D execution.”

The second article describes the microgrid implementation on the UCSD campus. This article by Byron Washom et al. summarizes their work accomplished: “University campuses offer a perfect setting for establishing a microgrid and the ability to maximize operational benefits of microgrid operation. The university setting also offers a unique collection of intellectual resources. Thus, in addition to improving operational efficiency, lower operating costs, and reducing the overall carbon footprint of the microgrid, the university environment is an ideal laboratory in which to conduct research to advance modern power system operation and integration of distributed renewable generation for the power delivery industry as a whole and provide opportunities for new graduate student research and learning.”

The third article by Mike Montoya and his SCE colleagues describe their on-going effort on the system of the future at Irvine with an emphasis on the inverters that are the heart and soul of most of the renewable energy sources. Their work focused on the operational behavior of inverters subjected to electrical system transients. The authors say that “this work involved lab testing inverters and developing proper models to determine the behavior of the electrical grid with high penetrations of variable renewable generation, which is mostly inverter based. The test results have been analyzed, and new transient models are being developed and validated. The models will be used to simulate the performance of the electrical grid during all kinds of transient events to determine the reliability of the overall electrical system.

The use of a real-time digital simulator will enable SCE to quickly investigate the electrical system’s dynamic behavior for many potential configurations and contingencies. This new tool allows simulations to interact with actual hardware (e.g., protective relays, controllers, inverters) in real time. Presently, SCE is lab testing inverters with advanced features such as voltage and frequency ride-through, volt var control, and power output control. These advanced features should prove to be useful in the implementation of microgrids.”

The DOD adds an additional dimension to the microgrid topic—providing resiliency to military facilities so that they can operate off grid for prolonged periods. The fourth article, by MIT Lincoln Labs and the DOD, describes these programs.

Another development is the role that microgrids can play in rural electrification in developing countries. Bringing electric lights, the ability to charge cell phones/smartphones, and the possibility to run personal computers to rural villages can have a dramatic impact on educational attainment and village economics. The full grid development as we are used to in the developed world can be too expensive and ambitious for many locales, and lower intensity local microgrids that are powered by PV and/or small scale wind with some electrical storage or by liquid propane (LP) fueled generators (LP lends itself well to rural distribution) can provide cost effective rural electrification. Terry Mohn and his company, General Microgrids, is a leader in this field and his article, the fifth one, describes the impacts that rural microgrids can have on village life.

Microgrid economics bring all the complexities of utility-integrated resource planning to the microscale. Time-varying/real-time wholesale energy prices, incentives for energy efficiency and renewable generation, markets for demand response, and future technology and energy prices all come into play. Decisions about generation technologies and reliability objectives can influence the system configuration including the design of the facility distribution network and switchgear/power electronics. A number of firms and universities are developing, or already have, commercial products that can operate a microgrid in the wholesale markets, including the optimization of generation and demand response against market prices and participation in ancillary services markets where allowed. The inclusion of uncertainty about renewable production and the optimization of electric storage complicate the problem considerably. How to assess microgrid economics in the longer term and make the best investment decisions under uncertainty is a much more difficult problem; the sixth paper by KEMA and Rutgers University describes the nature of the problem and shows some sample microgrid economics.

The seventh, and final, article on European microgrids and ecocities by Laurent Schmitt and his associates at Alstom Grid cover their current work on three European microgrid projects together with their technocommercial objectives. For a comprehensive discussion, they have presented one microgrid project from each of the following classes: NiceGRID, a utility microgrid, IssyGrid, a city microgrid, and Réflexe, an industrial microgrid. They conclude the article with a future vision for microgrid business and technology framework based on the lessons learned.

Most microgrid developments in the developed world will not be “green field” new construction, of course. In many cases the existing infrastructure may be owned and/or operated in part or whole by the electric utility and not the customer. Grid interconnection standards developed for single-technology distributed generation do not cover the full range of microgrid possibilities, and retail access to wholesale markets can challenge billing and settlement systems. The presence of a large microgrid on a distribution or subtransmission circuit can have implications for utility protection and automation systems. Many potential microgrid sites want the benefits of reduced energy costs, reduced emissions footprint, and improved reliability but on an outsourced basis. Third-party financing and the development of microgrids on a purchased power agreement basis akin to renewable energy procurement is attractive for many users. How this model develops and interacts with utility franchise and tariff law and regulation is a developing question. Utility participation in this development is desirable both in terms of technical expertise around distribution systems as well as grid and market integration. “In My View” column author Ed Krapels of Anbaric Holding speaks to some of these questions.

Finally, improving grid resiliency is a current objective around the United States in light of recent widespread and multiday outages after severe weather events. Microgrid development is the customer’s answer to the problem when power outages are not acceptable on any basis. This leads to a couple of interesting questions: first, on a regional basis, how should planners consider and balance customer investments in reliability/resiliency with utility investments? And second, when is it technically and economically feasible today for a facility microgrid to provide emergency services to adjacent customers over utility infrastructure? (It is never allowed today, per se, but will it be in the future?) How could such a construct be planned, incentivized, and compensated, as well as integrated with utility planning and operations? Just as microgrids decentralize generation and energy economics/operation, they have the potential to decentralize system planning and investments, if we are smart enough to road map how this can happen for best overall benefits.

These articles cover a wide spectrum of issues related to the development of microgrids. We hope they help put this broad topic in perspective for our readers and provide a foundation for more detailed investigations. We also hope this issue will be useful source of reference for those who are currently undertaking, or will undertake, this critical issue. For further insight into any of the topics covered in this issue, you are encouraged to go through the recent literature and the “Further Reading” entries cited at the end of each article. We also strongly encourage the readers to read the “In My View” column. We thank the magazine’s Editorial Board for encouraging us to develop this issue. We applaud their vision and encouragement.

In This Issue

Feature Articles

Departments & Columns

Upcoming Issue Themes

  • November/December 2017
    Renewable Integration
  • January/February 2018
    Societal Views of the Value of Electricity
  • March/April 2018
    Controlling the Unpredictable Grid