Smart Grid needs to get smarter

Lights need to stay on even during extreme weather or other types of disasters and new options may soon be available to avoid power-related crises.

07/30/2012


ISS SourceLights need to stay on even during extreme weather or other types of disasters and new options may soon be available to avoid power-related crises.

Starting small could keep critical services going, even when the high-voltage grid suffers a crippling blow, said researchers at Carnegie Mellon University. By thinking small like the U.S. military, it is possible to protect power supplies in the event of a massive grid failure. By adopting small, local energy technologies, it is possible to keep services up and running. California Governor Jerry Brown said he wants 12,000 MW of such power supplies in his state.

In the current conditions of the grid, a natural disaster could result in prolonged regional blackouts. To combat future widespread and extended power outages, Carnegie Mellon University researchers created a strategy to use local distributed electricity generation, distribution automation, and smart meters to form small electricity “islands” that would support critical social services in the event of a substantial disruption resulting from extreme weather, terrorism, or other causes.

Distributed generation (DG) collects and distributes electricity from many small energy sources rather than relying on large centralized power facilities. Carnegie Mellon University researchers Anu Narayanan and M. Granger Morgan examined the incremental cost of adding DG units and smart meters to a hypothetical community of 5,000 households covering an area of 5 km.

Under normal operation, large centralized utility generators send electricity along a high-voltage transmission system to a low-voltage distribution system that ultimately delivers power to homes, schools, police stations and other local consumers. An extreme disturbance such as a hurricane can disrupt the high-voltage transmission system and eliminate power to entire regions.

Under the Narayanan and Morgan strategy, electricity circuits would manually or automatically reroute to form isolated energy islands powered by local DG units. To achieve a smart grid DG system, utility companies would need to install smart meters that can efficiently disconnect non-critical loads, add automated components to reroute electricity circuits, and upgrade fault-handling equipment and control software to ensure the smaller grid’s reliability.

Community social services deemed critical during a substantial power outage could include a subset of community grocery stores, gas stations, cellular telephone base stations, streetlights, police stations, and schools.

The researchers said for their model community 350 kW of power would be necessary to continue these services during a blackout, but this limited power supply could cycle between the services. For example, the school could operate in day shifts for elementary, middle, and high school students and then close at night, when the police station could get power at full capacity. Beyond those basic necessities, communities could invest in backup power for water and sewage treatment, traffic lights, and the local jail. Additional arrangements would need to provide for temperature control if a blackout occurred in a region or season that required heating or cooling for basic survival. Most hospitals, airports, and radio and television broadcasting stations already possess independent emergency backup power supplies.

Narayanan and Morgan studied the costs of building regional DG circuits to support critical social services. Scenarios vary based on whether a region has zero, limited, or sufficient existing DG capacity. If enough DG units already exist within a region, the costs include the fee to purchase the options to acquire 350 kW during a blackout. If a region has insufficient existing DG infrastructure, the costs of installing new DG units and providing maintenance are key.

Other considerations include the use of public or private financing options to fund a DG project and the probability of an extended regional blackout. The researchers estimate the cost per household for implementing various DG scenarios would be $9 to $22 per year for risk probabilities ranging from 0.01 to 0.0001. Even the highest cost estimate is far less than 1% of an assumed median household income of $50,000, providing support for switching to DG units. The potential costs to a community resulting from a large power outage also must factor into decisions about whether to invest in these upgrades.

Strategically constructing regional DG circuits may help reduce the effects of catastrophic electricity failure resulting from natural or human-triggered events, ensuring critical services necessary for the health and safety of communities. The researchers said this strategy would best undergo implementation on a statewide or regional level to prevent the influx of citizens from neighboring communities that lack such an emergency power procedure to ensure critical social services.

“There are currently a few obstacles to implementing such a strategy, including state laws that prevent the deployment of cost-effective combined heat and power (CHP) ‘microgrids,’ and the lack of incentive for power companies to invest in such a system,” Narayanan said. “We have the technology to make our critical services less vulnerable to large blackouts. What we need now are the right policy initiatives to make it happen.”



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