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Extreme weather and other natural disasters can threaten lives, disable communities and devastate electric utilities' generation, transmission and distribution systems. And following recent storms like Hurricane Sandy, the resilience of the grid has perhaps become more important than ever to utilities and their customers.

Although distribution resiliency is based on several elements, including damage prevention and system recovery, survivability is a novel function for most utilities - one that will require new business models and innovation.

Survivability refers to the ability to maintain some basic level of electrical functionality to individual consumers or communities in the event of a complete loss of electrical service from the distribution system. The key elements of survivability include communicating with customers; using resilient technologies to supply critical infrastructures such as traffic signals, prisons, hospitals and cell phones; and equipping and enabling consumers to use distributed generation.

The concept of assisting customers with survivability features is relatively new to the electric industry. Historically, many customers such as hospitals, banks and data centers have assumed responsibility for their own survivability, relying on generators, uninterruptible power supplies and, occasionally, alternative distribution feeds (custom service coordinated with the electric utility).

What can be done now?

Because customers’ expectations of service reliability have changed dramatically with the evolution of the 24/7, digitally connected society, now is an opportune time for utilities to reassess their role in maintaining power to essential services, such as traffic lights, prisons and hospitals, and in providing customers with uninterrupted access to communications and modern conveniences.

There are various opportunities to improve survivability using existing technology and materials, including the following:

Communicating with customers: Utilities are beginning to use both the Internet and smartphones to enhance the targeting and speed of their communications. For example, Commonwealth Edison Co. (ComEd) is among a growing number of utilities that facilitate externally facing outage reporting and communication.

ComEd offers an interactive outage map on ComEd.com that customers can use to determine the location and scope of outages and to get estimated times of restoration. ComEd also offers a mobile application for iPhone and Android devices that enables customers to report an outage and check restoration status; view their account summary and history; manage payments, including budget billing, automatic payments and one-time payments; report a meter reading; and find a location to make an in-person payment.

Community energy storage: The electricity enterprise may benefit from cost-effective and reliable bulk energy storage to help balance and optimize supply and demand of bulk power resources. Distribution-level energy storage offers potential advantages, such as enhanced reliability and support of self-sufficiency.

The Electric Power Research Institute (EPRI) is examining the functional requirements and storage technology capabilities for mitigating the effects of variable renewable generation, improving reliability, and facilitating service when the distribution system is damaged. Certain battery technologies may be approaching a stage of development at which they can be considered for distributed storage applications at a community - or even individual customer - scale.

Where can innovation be employed?
Through collaboration with electric utilities and technology providers worldwide, there are also opportunities for accelerating the development and adoption of innovative technologies and methods that may help with survivability, including the following:

Using PEVs as a power source: Plug-in electric vehicles (PEVs), both all-electric and hybrid, could be used to supply energy to a home during an outage. Hybrid electric vehicles also could operate as a gasoline-fueled generator to provide additional standby power.

Automakers are interested in the concept, but the technologies require further development. Nissan Motor Co. Ltd. recently unveiled a system that enables the Nissan Leaf to connect with a residential distribution panel to supply a residence with electricity from its lithium-ion batteries. The batteries can provide up to 24 kWh of electricity, sufficient to power a household’s critical needs for up to two days.

Using solar photovoltaic (PV) systems as a backup:
Increasingly, consumers are installing rooftop PV systems to augment grid-supplied electricity. Usually limited by roof area and sized to meet an economically viable portion of the building’s electrical needs, these systems cannot supply 100% of a residence’s typical demand, nor do the systems, as currently configured, allow for operation as independent microgrids to supply part of a residence’s needs. EPRI assessments have identified inverter and control designs that could convert PV systems into self-sufficient technologies, but few inverter manufacturers have stepped forward to serve this need.

In 2011, two U.S. Department of Energy projects demonstrated inverter products that can operate while tied to the grid or “islanded.” Princeton Power Inc. demonstrated a 100 kW demand response inverter with two DC terminals and two AC terminals. Princeton is also introducing a 10 kW version specifically for the residential and small commercial markets. Meanwhile, Petra Solar demonstrated a micro-inverter-based PV system capable of operating in grid-tied or islanded mode.

Both companies report that they have demonstrated seamless transition between these modes. Other companies report development of similar products. With a proper transfer switch (perhaps controlled by the utility), these products could provide backup power to residences or a community during an outage.

Matching consumer load to PV capabilities:
The existing controls associated with PV arrays are not sufficiently functional to match the electrical demand of a residence without the presence of grid supply or local storage. Companies are developing residential circuit breaker panels that allow the control of individual circuits and appliances.

Control devices could be developed to weave these breaker panels into the PV system so that when grid power is lost, load is automatically curtailed to balance supply and load for the residential microgrid. These systems also could manage the “ramps” that occur as the sun rises and sets or as clouds block sunlight.

Providing urgent services: An opportunity exists to identify innovative technologies that can provide limited services or “urgent services” to critical aspects of community infrastructure. Only a few of these technologies have been identified, and fewer still have been researched. Examples include the following:

- Cell phones: During a prolonged power outage, even if cell phone towers are energized, the cell phones themselves will eventually run dry. Cell phone users whose automobiles have gas or electric storage and patch cords can charge their phones. A few consumers have solar chargers. A resiliency plan would encourage and instruct citizens to have solar chargers. Utilities could consider making them available through various channels and at various prices or at no cost.

- Conventional vehicles: If appropriate cables and connectors were available, conventional internal combustion engine (ICE)-powered vehicles could be used to energize devices such as cell phone chargers, flashlight battery chargers and critical medical devices.

- Traffic lights: During rolling blackouts in South Africa in 2007, a major cause of traffic accidents was the loss of functional signals. A self-sufficient traffic light system might be designed with LEDs and battery backup (or solar PV backup) to operate during an outage.

Clark Gellings is a fellow at the Electric Power Research Institute. This article is adapted from a recent EPRI white paper titled “Enhancing Distribution Resiliency: Opportunities for Applying Innovative Technologies.” For more information on the paper, click here.


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