Connecting Small-scale Renewables to the Smart Grid

By Dick DeBlasio, NREL

Smart grid enthusiasm is everywhere, and much is rooted in the opportunity to increase reliance on renewable energy sources such as biomass, geothermal heat, sunlight and wind.

Small-scale renewable energy is an especially promising notion, offering the chance to widely decentralize power production and create a more secure, resilient facility for electricity delivery. In a scenario of distributed generation, utilities would be better positioned to more efficiently manage peak demands, subvert transmission overloads and keep power flowing to everyone. Their customers, in turn, would be able to lower costs by offsetting some of their usage of utility-provided power and effectively, via net metering, selling power back to the grid.

Where do barriers to connecting small-scale renewables to the smart grid reside? And what business, regulatory and consensus standards activities are taking place to overcome them?

Going Green in Steps Large and Small

With global energy demand climbing for foreseeable decades and governments at various levels legislating incremental conversion to green power, the next-generation smart grid will leverage renewable energy sources to a greater degree than before.

Large-scale renewables such as commercial wind farms figure to factor more prominently in worldwide energy supply. Small-scale, distributed renewables, too, stand to comprise an increasing role as interconnection methods for solar, wind and other generation technologies for consumers and businesses and storage candidates such as electric-vehicle batteries mature.

Small-scale renewables' modularity offers benefits that central-station power plants and long-distance transmission and distribution alone cannot deliver because power is generated when and where it is needed. When connected to the grid, distributed resources can augment the traditional, central-station model by relieving pressure on the entire facility during peak demand.

Key barriers must be overcome, however, to realize the potential of smart grid distributed generation and small-scale renewable energy sources. Advocates of all technoliges oversimplify logistics or exaggerate their causes' benefits, and some proposed renewables-leveraging techniques never have been done on significant scale. The existing grid was designed for centralized production of consistently flowing power; decentralization and increased reliance on intermittent renewable energy sources represent nothing less than one of the smart grid's transformations with significant business, regulatory and technical ramifications.

Understanding Interconnection Barriers

Grid interconnection of distributed generation technologies calls up cost, safety, security, reliability and interoperability issues.

Only limited history of their customers' providing power back to the grid exists; utilities have concerns about employee safety and system reliability regarding wide participation in power generation by interconnected nonutilities. Some utilities go beyond typical requirements, such as preventing power from flowing back to the grid when de-energized and ensuring access to manual disconnects, to mandate isolation transformers and steep liability insurances that make interconnection complex and costly.

The grid interface is a prime focus. It can contribute to worker safety and grid security during failures by adopting protective schemes. Here, too, common billing and measurement techniques are needed for a utility to cost-effectively engage all its customers and their multivendor, small-scale renewable generation technologies.

Storage also must be improved to realize renewables' greatest smart grid promise. Renewable energy sources have nonconstant output, so to count on them, the smart grid must be able to flexibly store for later use the power generated when the wind blows, the sun shines, etc. Storage solutions based on compressed air, district heating systems, electric vehicle batteries or pumped hydro must mature to adapt the smart grid for renewables' intermittency.

Moving Forward

Entities are helping overcome regulatory and business barriers to connecting renewables to the smart grid. Some jurisdictions and utilities offer incentives for participation in small-scale renewable generation.

In Europe, negotiations exist about how to distribute fairly the costs for linking distributed resources and accommodating their interconnection upstream in the grid.

The Department of Energy announced in July $92 million in new funds to stimulate innovation in U.S. green technology such as affordable, large-scale storage.

As for technical barriers, it is consensus standards development where the hype of a concept's potential is distilled down to functional reality.

Standards development can offer the gamut of the stakeholders in a technology's development an open, fair and equitable process to ensure industry and society's needs are well-served, to eliminate unnecessary expenditures and to unleash innovation.

IEEE has more than 100 smart grid standards in development. The IEEE 1547 Standard for Distributed Resources Interconnected with Electric Power Systems is a widely adopted resource relevant to small-scale renewables. It addresses the performance, operation, testing, safety considerations and maintenance of a grid interconnection.

IEEE 1547 has been identified in the U.S. National Institute of Standards and Technology (NIST) "Framework and Roadmap for Smart Grid Interoperability Standards."

A series of standards subsequently has emerged to complement the original IEEE 1547. P1547.8, targeted for 2012 ratification, is designed to future-proof the original framework by extending current functionality to emerging storage technologies and future advancements and by addressing industry and NIST recommendations for improved interconnection performance functionality.

The draft standard provides greater support for intermittent renewables and more flexible use of inverters, such as those in home solar power systems, enabling easier, more robust grid connection.

IEEE P1547.8 also addresses energy storage devices, hybrid generation storage systems and plug-in electric vehicles.

The IEEE P2030 Working Group was formed in March 2009 to unify communications, information technology (IT) and power engineers in developing a guide that establishes common smart grid definitions and identifies the next-generation facility's necessary elements and functional requirements.

The working group found the need for more than 70 standard interfaces to interconnect utilities, customers and components such as generation systems for small-scale renewable energy systems.

Sponsor balloting for the IEEE P2030 guide is scheduled for March 2011.

Renewables' role is expanding, and the ongoing, worldwide smart grid rollout only will accelerate that trend.

Distributed generation of small-scale renewable sources promises especially valuable benefits to utilities and their customers across efficiency, flexibility, security, reliability and economics.

Governments, utilities and standards bodies are working to overcome interconnection barriers and to ensure renewables' potential is realized in next-generation electricity delivery facility.

In addition to his role as chair of the IEEE P2030 Working Group, Dick DeBlasio is a member of the IEEE Standards Association Board of Governors and chief engineer and principle laboratory program manager for electricity programs with the National Renewable Energy Laboratory, http://nrel.gov.

Top Five Hurdles to Overcome When Integrating Renewables

By Darrell Hayslip, Xtreme Power

As the U.S. moves toward a renewable energy and smart grid future, it must address challenges associated with effectively incorporating clean power into the national energy mix. Power sources such as wind and solar have inherent weaknesses, given their dependence on natural and unpredictable fuel sources. Overcoming energy technology challenges is critical to building a more sustainable grid.

What are the major hurdles in implementing renewable energy onto the grid?

1. Price. The high capital expenditures required to install renewable energy projects present the biggest roadblock to sustainability. Just a few years ago, the industry experienced rapid growth as gas prices soared to unprecedented levels and prompted consumers to pursue other options. But now that petroleum prices have come back down, customers are asked to pay a premium for access to resources that are cleaner but more variable than their current generation sources. The rate of renewable project development is correlated to the renewable portfolio standards and other policies in a given area, so to see growth in this area, state and federal officials must enact provisions to justify the high cost of constructing, maintaining and distributing power from a clean energy system.

2. Predictability. As part of maintaining and ensuring reliability, utilities have been responsible for forecasting future energy demand at discrete intervals. After inputting data about elements such as weather conditions, a load profile is compiled for a 24-hour period. Armed with this information, the utility puts together a resource plan, which lays out the anticipated generation required and resources that will be committed to meet the day's forecast demand. This puts the utility in a predicament: It doesn't want to make generation commitments in excess of the load demand, but it also risks planning for too little and compromising the reliability of service. This challenge is compounded because purchasing is markedly more difficult with renewable resources. Wind conditions change, and a passing cloud can take a solar installation from optimal output to one closer to zero. The power's value is diminished over a controllable resource.

3. Variability. Renewable energy operators typically know how much energy will be generated at the site over a year, but the inherent moment-to-moment variability of solar and wind resources creates short-term uncertainty. With renewables, generation must respond to changing load and supply. The volatility in energy output of wind and solar installations limits the amount providers safely can connect to the grid and often requires other, more stable units to be tied in. Variability also burden's other sources to respond to any sudden outages from the renewable generation site.

4. Interconnection point. Large-scale renewable energy projects are springing up across the country in remote areas. Although these areas are ideal in available space, they generally lack access to effective transmission infrastructure. For example, the amount of western Texas renewable projects far exceeded the grid's ability to deliver their output to the market. If Dallas consumers are to use power generated in western Texas, the grid must be capable of transferring power from the generation area to load centers. Grid connection can be requested, but until the proper grid upgrades have been completed, this is a moot point. To fully capitalize on the ever-increasing amount of renewable generation available, major infrastructure and financing challenges must be addressed properly.

5. Siting. As mentioned, large-scale solar and wind projects often are built in large, unpopulated areas. Site selections frequently are met with two major stumbling blocks: Environmentalists often protest project development, claiming the systems disrupt nearby wildlife and in some cases threaten endangered species. In addition, building in remote locations means that the point of generation is far from consumers, making transmission that much more complicated. It makes more sense to construct projects near the point of consumption. Installing in populated areas, however, presents different complications. Although residents enjoy the environmental benefits of renewable energy projects, many do not want to look out the window and see a wind turbine or rack of solar panels—the classic "not in my backyard" situation. In the case of wind turbines, building in residential areas also presents a danger to bird populations. Even if other hurdles are addressed, siting likely will present the ultimate challenge in renewable energy project development.

Darrell Hayslip is chief development officer of Xtreme Power.

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