December 04, 2004
On Public Electric Power Grid Reliability And Terrorism

Mark P. Mills and Peter W. Huber have an article in the City Journal on whether terrorists could manage to knock out electric power to New York City for a long period of time and on how to make the electric grid more reliable.

It takes almost 11 gigawatts of electricity to keep New York City lit in the late afternoon on a hot summer day—a huge amount of power. All the air conditioners, lights, elevators, and quietly humming computers inside use a whole lot more energy than the cars and trucks out on the streets. But because the fuels and infrastructure that deliver the electric power are so distant and well hidden, it's hard to focus public attention on how vital they are to the city's survival. And how vulnerable.

Few of us have even the vaguest idea just how much a gigawatt of power might be. So let's talk Pontiacs instead: 110,000 of them, parked door to door in Central Park. At exactly the same moment, 110,000 drivers start the 110,000 engines, shift into neutral, push pedal to metal, and send 110,000 engines screaming up to the tachometer's red line. Collectively, these engines are now generating a total of about 11 gigawatts of shaft power.

The writers do not bring this up but the power of those cars suggest a future solution to the power back-up needs of New York City. See my posts Will Electric Hybrid Cars Be Used As Peak Electric Power Sources? and Cars May Become Greater Electricity Generators Than Big Electric Plants.

Mills and Huber say that with more sophisticated technology the massive power blackout that struck the American Northeast and Canada on August 14, 2003 could have been prevented.

Had they had real-time access to SCADA networks in Ohio, utilities across the Northeast would have seen the August 14 problem coming many minutes, if not hours, before it hit and could have activated protective switches before the giant wave swept east to overpower them. But in the deregulatory scramble of the 1990s, regulators had pushed the physical interconnection of power lines out ahead of the interconnection of SCADA networks. The software systems needed for automated monitoring and control across systems had not yet been deployed. By contrast, on-site power networks in factories and data centers nationwide are monitored far more closely and make much more sophisticated use of predictive failure algorithms.

Nor had the grid's key switches kept pace. To this day, almost all the grid's logic is provided by electromechanical switches—massive, spring-loaded devices that take fractions of seconds (an eternity by electrical standards) to actuate. But ultra-high-power silicon switches could control grid power flows much faster, more precisely, and more reliably. Already, these truck-size cabinets, containing arrays of solid-state switches that can handle up to 35 megawatts, safeguard power supplies at military bases, airport control hubs, and data and telecom centers. At levels up to 100 megawatts, enormous custom-built arrays of solid-state switches could both interconnect and isolate high-power transmission lines, but so far, they're operating at only about 50 grid-level interconnection points worldwide.

The current structure of regulation of the electric power grid provides disincentives for building a more reliable grid. If you want to follow the debate on government regulation of the electric power industry and energy policy more generally be sure to check out Lynne Kiesling's Knowledge Problem blog.

One quibble I have with their essay has to do with their argument that capacity for locally generated power increases the reliability of the public grid.

At the same time, distributed, small-scale, and often private efforts to secure power supplies at individual nodes directly strengthen the reliability of the public grid. Large-area power outages like the one on 8/14 often result from cascading failures. Aggressive load shedding is the only way to cut off chain reactions of this kind. A broadly distributed base of secure capacity on private premises adds resilience to the public grid, simply by making a significant part of its normal load less dependent on it. Islands of especially robust and reliable power serve as centers for relieving stresses on the network and for restoring power more broadly. Thus, in the aggregate, private initiatives to secure private power can increase the stability and reliability of the public grid as well.

Local generation capacity reduces the dependence of those locations on the public grid. But if the public grid is overloaded and in danger of a cascade of failures those local generation plants only help if they kick on before the cascade of failures and in response to a building strain in the grid. If local generating capacity is designed to turn on in response to a loss of power then their switching on will come too late to prevent a large grid cascading failure. Back-up generators reduce the disruption to society as a whole by allowing hospitals, phone services, and other services to continue to function. But generators that kick on in response to grid failure do not prevent grid failure.

If those local plants operate continuously as a permanent substitute for getting power from the public grid they have no effect on the reliability of the public grid. Such sites do not figure into calculations of how much generation or distribution capacity the public grid needs. So the public grid will be smaller due to the lack of demand from self-sufficient sites and the public grid will be just as liable to reach some critical point and fall over. If terrorists knock out transmission lines or switching stations or natural gas pipelines that deliver gas to electric plants then local generation capacity will not save the grid from failure. If the local generators are run on natural gas then they will even stop working in response to attacks on natural gas pipeline systems just as the public natural gas powered electric generator plants will stop.

Ultimately vulnerability to the public grid may end because the economies of scale from building large electric power plants may vanish and the need for a grid to distribute power from those large plants may come to an end. For how that might come to pass see my post Thin Film Fuel Cells May Obsolesce Large Electric Plants. However, if fuel cells are powered by natural gas then such a turn of events will not end the vulnerability of society to attacks on large power distribution networks. We will still be vulnerable to attacks on natural gas pipeline systems. However, liquid fuel systems are much less vulnerable to attacks because local storage of liquid fuels is cheap and easy.

An economy based on cheap batteries and cheap solar photovoltaics would be much less vulnerable to attack in some parts of the country. But the problem with solar is that it is not concentrated enough to allow enough local generation of power in a highly dense area such as New York City. So in a solar/battery economy grids would still be needed to bring power to major metropolitan areas, especially in regions closer to the poles.

However, solar power used to drive artificial hydrocarbon synthesis (carbon-hydrogen fixing by either direct photosynthesis in an artificial structure or electrically driven chemical reactions - which photosynthesis really is anyway ) to create liquid hydrocarbon compounds would be fairly invulnerable to any man-made disruption. Though a very large volcanic eruption would seriously disrupt any solar-based power system (and most life on the planet). Nuclear power would continue to deliver power after a huge volcanic disruption.

Share |      Randall Parker, 2004 December 04 01:51 PM  Energy Tech


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