Why can’t magnetism be used as a source of energy?

Because magnets do not contain energy — but they can help control it…

By Sarah Jensen

In 1841, German physician and physicist Julius von Mayer coined what was to become known as a first law of thermodynamics: “Energy can be neither created nor destroyed,” he wrote. It can, however, be converted from one kind to another — by solar panels that turn sunlight to electricity, or in the transformation of natural gas molecules to the heat that cooks our dinner and heats our homes.

“Magnetism is a force, but it has no energy of its own,” says David Cohen-Tanugi, vice president of the MIT Energy Club and a John S. Hennessy Fellow in MIT’s Materials Science and Engineering department. Still, he adds, “magnetism is extremely useful for converting energy from one form to another. About 99% of the power generated from fossil fuels, nuclear and hydroelectric energy, and wind comes from systems that use magnetism in the conversion process.”

Every energy generation technology — with the exception of photovoltaics — relies on spinning turbines that put electrons in motion and push them through circuits and generators. “As these charged particles move past magnets inside the turbines, they create a field around them that affects other charged particles,” says Cohen-Tanugi. “This is the magnetic force that converts the energy of wind and coal and nuclear fuel to the electricity that’s sent out into the power grid.”

Much of that grid is managed by using principles of magnetism, as well. “The transformer stations you see along the highway or in industrial areas are responsible for converting high voltage electricity to a usable 110 volts,” says Cohen-Tanugi. High voltage lines deliver power from the power plant to the transformer stations, and as electrons move through the transformer’s large coils, they give rise to magnetic fields that change the electricity’s frequency to a voltage safe for powering our toasters, bedside lamps, and hair dryers.

Generators and motors in everything from hybrid cars to computer hard drives employ magnets, and researchers are currently investigating the potential of rare earth magnets, exceptionally strong permanent magnets composed of alloys of rare earth elements. Already used in state-of-the-art motors and generators and other energy-sector applications, they represent the next generation in magnetism’s role in energy production.

Thanks to 51-year-old Mark Taylor from Charlotte, North Carolina, for this question.

Posted: May 22, 2012

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