Kenneth McLeod, Binghamton University, State University of New York
To curb climate change, many experts have called for a massive switch from fossil fuels to electricity. The aim is to electrify processes such as heating homes and powering cars, and then generate the increased needs for electrical energy using low- or zero-carbon sources like wind, solar and hydropower.
More than 30 cities in California, including Berkeley and San Francisco, have moved in this direction by banning natural gas service in most new buildings. Currently, energy use in buildings generates more than 40% of San Francisco’s greenhouse gas emissions.
There are simple electric options for heating buildings, hot water, and drying clothes, but switching to electricity might be more controversial in the kitchen. Traditional electric ranges are notoriously slow to heat and cool. They also pose safety concerns as their heating coils can stay hot for tens of minutes after shutdown.
What’s a serious cook to do? A high-tech alternative is magnetic induction. This technology was first proposed over 100 years ago and demonstrated at the World’s Fair in Chicago in 1933. Today, magnetic induction cookers and hobs are common in Europe and Asia, but remain a niche technology in the United States. As more cities and states move towards electrification, here’s a look at how magnetic induction works and its pros and cons for cooking.
I am an electrical engineer specializing in research on electromagnetic fields. Much of my work focuses on medical therapy applications – but whether you expose human tissue or a pan on a cooktop to electromagnetic fields, the principles are the same.
To understand what electromagnetic fields are, the key principle is that an electric charge creates a field around it – essentially, a force that extends in all directions. Think about static electricity, which is an electrical charge often produced by friction. If you rub a balloon on your hair, the friction will charge the balloon with static electricity; Then when you lift the ball away from your head, your hair will stand on end, even if the ball does not touch it. The ball pulls at your hair with attractive electric force.
Moving electrical charges, like electricity flowing through a wire, produce magnetic fields – areas of magnetic force around the current path. The Earth has a magnetic field because electric currents flow through its molten core.
Magnetic fields can also produce electric fields and that is why we use the term electromagnetic fields. This concept was discovered in the 1830s by English scientist Michael Faraday, who showed that if an electrically conductive material, such as a wire, is placed in a moving magnetic field, an electric field is created in the conductor. We call it magnetic induction. If the conductor is looped, an electric current will flow around the loop.
Faraday’s discovery served as the basis for the development of electric motors. His work also demonstrated a way to heat materials without using a traditional heat source such as fire.
Where does the heat come from?
All materials have resistance, which means that when electric current passes through them, the flow will at least be somewhat impeded. This resistance leads to the loss of part of the electrical energy: the energy turns into heat and, as a result, the conductor heats up. In my biomedical research, we are studying the use of radiofrequency magnetic fields to heat body tissue to help tissue heal.
Instead of conventional burners, the cooking points on induction hobs are called hotplates and consist of spools of wire recessed into the surface of the hob. For maximum efficiency, engineers want most of the magnetic field energy produced by each hob to be absorbed by the cookware placed on it. The magnetic field will create an electric field at the bottom of the pot, and because of the resistance, the pot will heat up, even if the hob does not.
For best performance, magnetic induction ranges and hobs should operate at a high magnetic field frequency – typically 24 KHz. They also require pots made from materials that magnetic fields do not easily pass through. Metals with a high iron or nickel content absorb magnetic fields, so these are the most efficient options for induction cooking. Iron absorbs magnetic fields more easily than nickel and is much cheaper, so iron-based materials are most often used for magnetic induction cookware.
More responsive and safer, but more expensive
Since induction hobs require something to absorb magnetic fields in order to produce heat, they are inherently safer than a traditional electric hob. Placing your hand on the hob will not heat your hand noticeably. And because these systems heat cookware without directly heating the cooktop, cooktops cool quickly after the cookware is removed, reducing the risk of burns.
Cookware itself tends to heat up and cool down quickly, and temperature control is very precise – one of the key properties of cooking value in gas ranges. Another plus is that induction hobs usually have smooth surfaces – often glass or ceramic – so they’re easy to clean.
Modern induction hobs are as energy efficient as traditional electric ranges and about twice as efficient as gas ranges. But that doesn’t necessarily mean they’re cheaper to operate. In many parts of the United States, natural gas is much cheaper than electricity, sometimes by a factor of three or four. This partly explains the wider acceptance of induction hobs in Europe, where until recently natural gas was much more expensive than electricity.
Another factor that has influenced adoption is that induction ranges and hobs are generally more expensive than traditional gas or electric ranges, but not substantially. And cooks will need to replace aluminum, copper, non-magnetic stainless steel, and ceramic pans, none of which work effectively on induction hobs. A quick check is that if a magnet sticks to the bottom of a pot, the pot will work on an induction hob.[The Conversation’s science, health and technology editors pick their favorite stories. Weekly on Wednesdays.]
Despite these factors, I expect orders to reduce the use of natural gas will lead to significantly increased use of magnetic induction ranges and cooktops. These measures usually focus on newly constructed buildings, so they won’t require costly conversions of existing homes.
Young singles and families moving into these new residences may not have acquired many cooking utensils yet and are likely to appreciate the safety associated with magnetic induction, especially if they have children. And early adopters who are willing to pay more for electricity from green sources, or for a hybrid or electric car, may not be upset paying a few hundred dollars more for a magnetic induction cooktop. and pans that work with it.
Domestically, the United States may adopt some form of carbon pricing in the near future, which would increase the cost of natural gas. And there is growing concern about indoor air pollution from gas appliances. More than a century after its first proposal, the day of magnetic induction cooking in the sun may have arrived.
Kenneth McLeod, Professor of Systems Science and Director of the Clinical Sciences and Engineering Research Laboratory, Binghamton University, State University of New York
This article is republished from The Conversation under a Creative Commons license. Read the original article.