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October 27, 2010

NASA creates a warning system to protect the electrical grid from damage from solar storms and Germany needs grid upgrade to protect against solar power

NASA's Solar Shield is a new and experimental forecasting system for the North American power grid

The troublemaker for power grids is the "GIC" – short for geomagnetically induced current. When a coronal mass ejection (a billion-ton solar storm cloud) hits Earth's magnetic field, the impact causes the field to shake and quiver. These magnetic vibrations induce currents almost everywhere, from Earth's upper atmosphere to the ground beneath our feet. Powerful GICs can overload circuits, trip breakers, and in extreme cases melt the windings of heavy-duty transformers.

This actually happened in Quebec on March 13, 1989, when a geomagnetic storm much less severe than the Carrington Event knocked out power across the entire province for more than nine hours. The storm damaged transformers in Quebec, New Jersey, and Great Britain, and caused more than 200 power anomalies across the USA from the eastern seaboard to the Pacific Northwest. A similar series of "Halloween storms" in October 2003 triggered a regional blackout in southern Sweden and may have damaged transformers in South Africa. While many utilities have taken steps to fortify their grids, many have not. Modern electrical grid networks are sprawling, interconnected, and stressed to the limit.





A large-scale blackout could last a long time, mainly due to transformer damage. As the National Academy report notes, "these multi-ton apparatus cannot be repaired in the field, and if damaged in this manner they need to be replaced with new units which have lead times of 12 months or more."

Permanent damage to the Salem New Jersey Nuclear Plant GSU Transformer caused by the March 13, 1989 geomagnetic storm. Photos courtesy of PSE&G. [larger image] That is why a node-by-node forecast of geomagnetic currents is potentially so valuable. During extreme storms, engineers could safeguard the most endangered transformers by disconnecting them from the grid. That itself could cause a blackout, but only temporarily. Transformers protected in this way would be available again for normal operations when the storm is over.

The innovation of Solar Shield is its ability to deliver transformer-level predictions. Pulkkinen explains how it works:

"Solar Shield springs into action when we see a coronal mass ejection (CME) billowing away from the sun. Images from SOHO and NASA's twin STEREO spacecraft show us the cloud from as many as three points of view, allowing us to make a 3D model of the CME, and predict when it will arrive."

While the CME is crossing the sun-Earth divide, a trip that typically takes 24 to 48 hours, the Solar Shield team prepares to calculate ground currents. "We work at Goddard's Community Coordinated Modeling Center (CCMC)," says Pulkkinen. The CCMC is a place where leading researchers from around the world have gathered their best physics-based computer programs for modeling space weather events. The crucial moment comes about 30 minutes before impact when the cloud sweeps past ACE, a spacecraft stationed 1.5 million km upstream from Earth. Sensors onboard ACE make in situ measurements of the CME's speed, density, and magnetic field. These data are transmitted to Earth and the waiting Solar Shield team.

"We quickly feed the data into CCMC computers," says Pulkkinen. "Our models predict fields and currents in Earth's upper atmosphere and propagate these currents down to the ground." With less than 30 minutes to go, Solar Shield can issue an alert to utilities with detailed information about GICs.

Meanwhile Germany has to beef up its grid to handle the dawn of each new day

Solar power is intermittent and can arrive in huge surges when the sun comes out (dawn of each day). These most often happen near midday rather than when demand for power is high, such as in the evenings. A small surge can be accommodated by switching off conventional power station generators, to keep the overall supply to the grid the same. But if the solar power input is too large it will exceed demand even with all the generators switched off. Stephan Köhler, head of Germany's energy agency, DENA, warned in an interview with the Berliner Zeitung on 17 October that at current rates of installation, solar capacity will soon reach those levels, and could trigger blackouts.

Uptake has been so rapid that solar capacity could reach 30 gigawatts, equal to the country's weekend power consumption, by the end of next year. "We need to cap installation of new panels," a spokesperson for DENA told New Scientist. The best long-term solution is to install region-wide grids

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