TCS Daily

Wind Magic

By Sallie Baliunas - October 17, 2002 12:00 AM

Editor's note: This article continues Dr. Baliunas' series on alternative energy sources.

"Any sufficiently advanced technology," says Arthur C. Clarke's Third Law, "is indistinguishable from magic." Magic works as entertainment when the excitable human imagination sees the seeming suspension of physical laws.

But the material cosmos does not operate by alchemy, luck, superstition or magic. The physical laws, uncovered by science, show a predictable universe.

The practice of science challenges Homo sapiens to "think different," as Apple Computer's ad campaign portrayed great minds like physicist's Richard Feynman. The fruits of thinking different include engineering benefits for humans and the environment.

Glorious Grid

Looking back over the 20th century, the National Academy of Engineering named the top twenty engineering achievements that had helped the world become "healthier, safer and more productive."

Neil Armstrong, the first human to leave bootprints in the lunar regolith, worked on and announced the list. Was the greatest engineering achievement of the 20th century Mr. Armstrong's realm of space exploration? No, that was twelfth. Other important works included the Internet (13th), computers (8th), air conditioning and refrigeration (10th), the airplane (3rd), health technology (16th) and automobile (2nd). But for number one, the National Academy of Engineering chose electrification - the extensive electrical networks that deliver electricity to the developed world - because it had so markedly improved the human condition.

The astonishing ability to deliver quality electricity to homes and businesses relies on the sources of electrical power - the fossil fuels, nuclear and hydroelectric power that produce over 95% of U.S. electricity - and the grid. The grid delivers electricity, and thinking about the grid is essential for considering large scale application of intermittent sources of electricity like solar and wind power.

No, electricity is not stored in a wall socket, light switch or even a light bulb, to be conjured up by a monthly bill to the sorcerers. Electricity is not magic.

To turn on a light switch is to command a perfect performance of the un-magical laws of physics. A light bulb glows when an electrical current - or a stream of negatively charged subatomic particles called electrons - is delivered to it.

Fatal Flaw: Intermittency

One key fact about the stream of electrons is that it is not stored. Current must be made and supplied when a customer (for instance, by way of the light switch) demands it. A local power distribution system senses the demand for power by the flicked-on light switch and routes power to the user. The request by the power dispatching system is rapidly met by the generating utility. Thus, turning on a light switch not only draws electrons from the grid, but also causes the current to be produced by the utility supplying electricity.

Can sunlight and wind - which now stand at less than 1% of U.S. electrical production - yield significant amounts of quality electricity that so improved life in the 20th century? Not without costs and fossil fuels, despite the notion that sunlight and wind are "free" and "inexhaustible" fuels.

Skip the problem that sunlight and wind are very dilute, so collecting devices for those free fuels impacts many square miles of ecosystem. Concentrate on intermittency - especially of wind - and its effect on the reliability and quality of electricity.

Wind farms at ideal sites produce power around one-third of the time, and the times of its availability are not very predictable and may not match demand. What does that mean for the grid, and the consumer?

Dispatching power through the grid has two elements, a base level and a variable, or peaking level. The amount to be dispatched is carefully estimated, based partly on past demand and forecasts of future demand, for example, a weather prediction for unusual cold would portend greater demand for heating, hence power.

The dispatching system senses and tries to meet power demand in near-real time. Over- or under-supplies must be avoided, perhaps by fulfilling a neighboring system's request, or by calling for reduced power generation. Doing otherwise could damage customer and grid equipment, and strand customers with no power.

As for base load, nuclear and large coal plants supply it well. But they are not suited to match quick swings in demand. Other fossil fuel and hydro plants can generate not only the variable but also the base demand. Hydroelectric output, for example, can be quickly adjusted upward or downward by increasing or decreasing the water flow through the turbines.

Wind blows too irregularly to be counted on for either base or variable power demands. With a significant amount of wind power erratically entering the grid, a dispatch system would carefully pair the capricious wind supply with traditional supplies in order to "balance" or "firm" the grid. Hydro capacity and location limit it as a balancing supply of wind power, which leaves fossil fuels, especially natural gas, to do the job. The fossil fuel standby sources must be operating or spinning in reserve to be able to make up for the unreliability of wind power.

Volatile wind and insufficient grid firming have threatened the grid in Denmark. Wind supplies a significant fraction of Denmark's electricity - between 10 and 15%, which is a discussed target amount for the U.S. electrical supply. On New Year's Day, 2002, low electricity demand and high wind power output sent an excess of electricity flowing through the grid. Surrounding countries could not use the excess electricity, so twelve wind farms had to be manually shut down.

In other words, the more that wind is relied on for electrical production, the more reserve plants powered mainly by fossil fuels will be relied on to maintain successful dispatch of electricity to the consumer. And it's all because electricity must be created on demand.

It isn't magic, just the immutable laws of physics.



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