Thursday, July 16, 2015

Secret magic of induction cooking - How does it work ?

Induction cookers suddenly appeared on the market a few years back and stealthily replaced all other electricity based stoves like heater coils and nichrome alloy stoves.

Induction cookers are notoriously energy efficient and safer compared to these older technologies.

So, the question is How does an Induction cooker work ?

The answer, like any magical technology is MAGNETS.
Yes, magnetic fields.

Watch this video explain how Induction cooking uses magnetic fields to concentrate energy exactly where you need it.

Bill from Edison explains :

Electrical Engineer Bill Kornrumpf describes how it works. AC power is converted to DC by a rectifier, then it is converted into high frequency AC power by an inverter. EE W.P. Kornrumpf invented better control circuitry for this and other appliances, reducing the size and amount of raw material used.

If you would rather see a fun video demonstrating the difference the metal plate makes, here is a video of induction cooking with half a vessel :

This video illustrates the magic behind it all.

Induction pans are made of ferromagnetic metal. Induction hobs have electromagnets in them and when they're turned on the induction cookware on the hob essentially turns into the element and gets hot - quickly! The amazing thing is that the actual hob surface doesn't get hot aside from a bit of reflected heat.

How efficient is an Induction Cooktop ?

84 %

An induction cooker is faster and more energy-efficient than a traditional electric cooking surface. It allows instant control of cooking power similar to gas burners. Other cooking methods that use flames or hot heating elements have a significantly higher loss to the ambient; induction heating directly heats the pot. Because the induction effect does not directly heat the air around the vessel, induction cooking results in further energy efficiencies. Cooling air is blown through the electronics beneath the surface but is only slightly warm.

According to the U.S. Department of Energy, the efficiency of energy transfer for an induction cooker is 84%, versus 74% for a smooth-top non-induction electrical unit, for an approximate 12% saving in energy for the same amount of heat transfer. Energy transfer efficiency tests, however, are steady-state, and do not take into account the energy wasted in heating up the hot-plate, ceramic top, or element of a conventional cooker initially before full heat transfer can begin. This energy is left behind when the cooking utensil is removed, and lost during cooling. This loss, and energy similarly lost in heating up the utensil, is likely to be very significant when heating up small amounts of food in a short time, and for maximum efficiency it is important to use the optimum size and shape of pan (tall pans can waste heat through the sides).

The U.S. Department of Energy proposed in 2014 new test procedures for cooking products to allow direct comparison of efficiency measurements among induction, electric resistance, and gas cooking tops and ranges. The procedures use a new hybrid test block made of aluminum and stainless steel, so it is suitable for tests on induction cookers. The proposed rule lists results of real lab tests conducted with the hybrid block. For comparable (large) cooking elements the following efficiencies were measured with ±0.5% repeatibility: 70.7% - 73.6% for induction, 71.9% for electric coil, 43.9% for gas. Tests conducted thus far suggest the 84% induction efficiency reference value should be taken with caution. though, as explained above, real life savings compared to other methods of cooking are greater than suggested by simple transfer efficiency because of the elimination of heat lost in heating up a hob or plate, and the reduction in heat lost during heating up of the utensil. The energy delivered by any form of cooker is only partly used to heat the food up to temperature; once that has occurred all energy is delivered to the air as loss through steam or convection and radiation from the pan sides. Real life efficiency is therefore very dependent on pan size and design (a pan with insulated sides and top could in theory reduce energy use greatly).

Energy efficiency is the ratio between energy delivered to the food (and pan) and that consumed by the cooker, considered from the "customer side" of the energy meter. Cooking with gas has an energy efficiency of about 40% at the customer's meter and can be raised only by using very special pots,. When comparing with gas, the relative cost of electrical and gas energy, and the efficiency of the process by which electricity is generated, affect both overall environmental efficiency and cost to the user.

What are the advantages of an Induction Cooker ?

Instant Adjustment

To serious cooks, the most important favorable point about induction cookers—given that they are as or more "powerful" at heating as any other sort—is that you can adjust the cooking heat instantly and with great precision. Before induction, good cooks, including all professionals, overwhelmingly preferred gas to all other forms of electric cooking for one reason: the substantial "inertia" in ordinary electric cookers—when you adjust the heat setting, the element (coil, halogen heater, whatever) only slowly starts to increase or decrease its temperature. With gas, when you adjust the element setting, the energy flow adjusts instantly.

But with induction cooking the heat level is every bit as instantaneous—and as exact—as with gas, yet with none of the many drawbacks of gas (which we will detail later). Induction elements can be adjusted to increments as fine as the cooker maker cares to supply (and nowadays that is very fine, especially at the critical low-temperatures end), and—again very important to serious cooks—such elements can run at as low a cooking-heat level as wanted for gentle simmering and suchlike (something even gas is not always good at). Someday, perhaps not so many years away, the world will look back on cooking with gas as we today look on cooking over a coal-burning kitchen stove.

No Wasted Heat

With induction cooking, energy is supplied directly to the cooking vessel by the magnetic field; thus, almost all of the source energy gets transferred to that vessel. With gas or conventional electric cookers (including halogen), the energy is first converted to heat and only then directed to the cooking vessel—with a lot of that heat going to waste heating up your kitchen (and you) instead of heating up your food.

As a comparison, 40%—less than half—of the energy in gas gets used to cook, whereas with induction 84% percent (or, by many estimates, more) of the energy in the electricity used gets used to cook (and the rest is not waste heat as it is with gas). There are two important heat-related consequences of that fact:
cooler kitchens: of course the cooking vessel and the food itself will radiate some of their heat into the cooking area—but compared to gas or other forms of electrically powered cooking, induction makes for a much cooler kitchen (recall the old saying: "If you can't stand the heat, get out of the kitchen."); and,

a cool stovetop: that's right! The stovetop itself barely gets warm except directly under the cooking vessel (and that only from such heat as the cooking vessel bottom transfers). No more burned fingers, no more baked-on spills, no more danger with children around.

We have already mentioned that the stovetop stays cool: that means no burned fingers or hands, for you or—especially—for any small children in the household. And for kitchens that need to take into account special needs, such as wheelchair access, nothing, but nothing, can beat induction for both safety and convenience.

Furthermore, because its energy is transferred only to relatively massive magnetic materials, you can turn an induction element to "maximum" and place your hand flat over it with no consequences whatever—it will not roast your non-ferrous hand! (Nor any rings or bracelets—the units all have sensors that detect how much ferrous metal is in the area that the magnetic field would occupy, and if it isn't at least as much as a small pot, they don't turn on.) And, while an element is actually working, all of its energy goes into the metal cooking vessel right over it—there is none left "floating around" to heat up anything else.

Moreover, gas—induction's only real competition—has special risks of its own, not all of which are as well known as they perhaps should be. While the risk of a gas flame, even a pilot light, blowing out and allowing gas to escape into the house is relatively small, it does exist. But a much bigger concern is simply gas itself, even when everything is working "right". Use any web search engine and enter the terms gas health risk cooking and see what you find ; if, for example, you visit the Gascape web site, you may never again want to even enter a house with gas laid on (take some time to really poke around on this site—you may be shocked). And, of course, all combustion releases toxic carbon monoxide.

Ease and Adaptability of Installation

Unlike most other types of cooking equipment, induction units are typically very thin in the vertical, often requiring not over two inches of depth below the countertop surface. When a cooking area is to be designed to allow wheelchair access, induction makes the matter simple and convenient.


It is an obvious but still very important fact that induction cookers are powered by electricity. Not every home actually has a gas pipeline available to it—for many, the only "gas" option is propane, with the corollary (and ugly, space-taking, potentially hazardous) propane tank and regular truck visits. But everyone has clean, silent, ever-present electricity.

Burning gas has byproducts that are vaporized, but eventually condense on a surface somewhere in the vicinity of the cooktop. Electrical cooking of any kinds eliminates such byproducts.

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