Solving today’s challenges requires juggling past, present, and future across many timescales.

Energy Blog: Time is Energy

Aug 25, 2020

by Michael E. Webber

Back in 2018, a dispute between Serbia and Kosovo led to an imbalance in the European-wide electric grid. A little more power was being drawn than was being accounted for by the system operator. This only came to light through an odd side-effect: Because of the relationship between the power on the grid and the alternating current oscillating along it, the frequency of the current was off by 0.004 cycles per second.

It’s scarcely enough to notice at first, but it threw electric clocks off by an incremental amount. After six weeks, European clocks were off by six minutes.

Geographic mismatches in the global energy system are well known. The need to move fuel and electricity from where it’s produced to where it’s consumed underpins national security concerns around imported oil and is at the heart of opposition to pipelines and transmission lines that span thousands of miles.

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But the temporal mismatches are also critically important. There are so many different timelines and timeframes for energy it’s hard to keep track.

We must balance the electric grid at sub-second intervals while building power plants and high-voltage transmission lines that can last decades, all while managing environmental impacts that last centuries.

Energy system planners whose portfolio spans keeping the lights on to disposing of nuclear waste perform a graceful balancing act that reaches from milliseconds to millennia.

Power plant managers work surrounded by the hum of large rotating machinery, heavy hunks of equipment bolted to power plant floors or to the top of wind turbine towers.

Those turbines and generators, spinning as elegantly as ballerinas, are synchronized to produce electricity at 50 or 60 cycles per second, depending on the location. That means these massive systems generate current that alternates every 20 milliseconds or less.

If the frequency of the grid sags too much—as little as a fraction of a millisecond per cycle—the whole system can trip; to avoid that, sometimes grid operators will decide to shed load, which leads to region-wide blackouts. Miniscule changes at a speed hard for humans to detect can have significant consequences.

Grid operators keep multiple power plants online and spinning just so that they
are ready on a moment’s notice to back up a tripped power plant or an equipment failure and to maintain the grid’s frequency. But because of the speeds involved, they have little time to react.

In contrast with such rapid changes, infrastructure takes years to build and lasts for decades. Hoover Dam on the Colorado River was built with a 1,000-year lifetime in mind.

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The way to span these vastly different timescales is with storage. We use batteries to store electricity in our handheld devices for minutes or hours; we store solid fuel at power plants for weeks or months; we store gas and oil in aboveground tanks and underground caverns for months to seasons; and mountains store snowpack that drives hydroelectricity for seasons to years.

Even the nonengineering side of the energy industry has multiple timescales. Financial decisions are reported quarterly and political elections are conducted biennially; both affect investments that require decades to unfold.

The other challenge we face is the difficulty in grasping lag time. The COVID-19 pandemic highlights this challenge. There are time lags between infection and symptoms, between symptoms and hospitalizations, and between hospitalizations and deaths. Each lag confounds policymakers, who have to wait weeks before a new policy can bring down case numbers. Or send them higher.

The same kinds of lags affect efforts to address climate change, where we must take actions today to mitigate warming that won’t happen for decades. Lag times over decades matched with sub-second balancing of the grid is a metaphor for all the other challenges we face in designing an energy system that simultaneously meets demands for affordability, reliability, and sustainability.

When we put too much emphasis on one requirement at the expense of others, we have a mismatch that puts everything out of whack.
Michael E. Webber is the Josey Centennial Professor of Energy Resources at the University of Texas in Austin and chief science and technology officer at ENGIE, a global energy company headquartered in Paris. His television series, Power Trip: The Story of Energy, is available on Apple TV, Amazon Prime Video, and local PBS stations.

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