Why Can’t Magnetism Be Used as a Source of Energy?

by Kate Repantis on January 9, 2015 · 6 comments

in Energy, Research

Guest Post by Sarah Jensen from the Ask an Engineer series, published by MIT’s School of Engineering

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

Photo: Bob Mical

Photo: Bob Mical

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 SM ’12. Still, he adds, “magnetism is extremely useful for converting energy from one form to another. About 99 percent 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.” Read more

Visit the MIT School of Engineering’s Ask an Engineer site for answers to more of your questions.

{ 6 comments… read them below or add one }

KIM January 9, 2015 at 1:45 pm

“About 99 percent of the power generated from fossil fuels, nuclear and hydroelectric energy, and wind comes from systems that use magnetism in the conversion process.”
That should be 100% not 99% or the sentence should be rewritten.

“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. “ Should read Every electrical energy… photovoltaic and dry cells-

“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.

This whole section is confusing plus the magnets are electromagnets not permeate magnets and are part of the generator not the turbine. Its the relative motion between the electromagnetic windings in a generator and the generator output windings that causes the current to flow. Also referred to as Faradays law.

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KIM January 9, 2015 at 2:34 pm

OK after doing some research heat energy left over from fossil fuel and nuclear plants can be used to produce electricity via the thermoelectric effect which along with the chemical process in drycells is missing from the original article. What I’m wondering is does anyone bother to proofread these articles for scientific accuracy?

Plus is this article really answering the original question? I would have explained this by comparing a magnetic field to a gravitational field. Their is no inherent energy in the gravitational filed itself. If you let the gravitational field act on an object by reducing or increasing an opposing force energy is either stored or released because of the resulting motion.

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Tymon January 9, 2015 at 8:13 pm

Stating that magnetism is a force but has no energy is incorrect and the author is forgetting the definition of work. Two separated magnets have energy in the same way a loaded spring has. The energy can be released in the form of work when the magnets are allowed to move.

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GJC January 9, 2015 at 8:13 pm

To KIM, there are still thousands of windmills that do work by moving water from lower to higher elevations using only mechanical gears and levers. These would be in the 1% of applications today perhaps, but can still be purchased from farm supply catalogs. It still might be the best way to use a windmill, because water at an elevation is a viable energy storage mechanism.

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GJC January 9, 2015 at 8:26 pm

Now, I will take exception to the false generalization implied in the article that only photovoltaics can generate electrical energy without a magnetic field.

There are several variations of the Wimshurst machine that use electrostatic fields alone to implement an electric generator. Of course, to convert the high voltage low current DC to a lower voltage, it is hard to imagine anything practical that doesn’t involve an inductor of some kind, hence your magnetic field gets involved. But you could keep an open mind to alternatives.

Oh, piezoelectric and thermoelectric devices also avoid explicit magnetic field usage.

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Kim OBrien June 18, 2015 at 8:22 am

There is a whole YouTube sub culture devoted to magnet motors, ‘free energy’ and over unity. Most claim that since Nickola Tesla was forgotten from history books that favor Edison and because J.P. Morgan once said. “I’m not interested in power I can put a meter on.” a conspiracy involving financers and Energy companies is preventing access to ‘free energy’. They have fewer followers than creationism but nevertheless YouTube provides an audience that would other wise be very small.

This comes from the Ask an Engineer folks where in the past we found out that electrons are pulled from the ground by the power station and now we find out by reading the original article that frequency becomes voltage due to magnetism in transformers.

“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.”

“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.” My ‘D’ and triple ‘A’ cells have spinning turbines inside?

If this is the level MIT’s electrical engineering department functions at (supposedly the best in the world) no wonder these conspiracy people have followers.

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