Industrial Electrical Heating: Technologies and Advantages

Overview

This article provides an introduction to industrial electric process heating (electro-heating) technologies. It briefly describes the basic principles of various electro-heating technologies and presents the economic, process and environmental advantages.

Common Electro-Heat Technologies

Resistance heating:	Direct: An electric current is driven through a material, which heats up due to its electrical resistivity. Indirect: An electric current is driven through a resistor, which heats up, and through convection and radiation, heats up a surrounding fluid or gas.
Infrared heating:	A heat source at high temperature emits infrared waves that are subsequently absorbed by a colder object.
Induction heating:	A solenoid is used to generate an alternating magnetic field. If a conductor is placed inside this field, an alternating electric current is induced in this conductor that opposes the alternating magnetic field. These eddy currents heat up the conductor.
Dielectric heating:	When a changing electrical field is applied to an electrical non-conducting material with an asymmetrical molecule structure, friction will occur between the vibrating molecules as they attempt to align with this field, leading to internal heat development.
Microwave heating:	Dielectric heating with a frequency range between 900 and 3,000 MHz.
Radiofrequency heating:	Dielectric heating with a frequency range between 10 and 30 MHz.
Electric arc heating:	A metal is placed between two graphite electrodes which are charged to generate an electric arc between them. The high current goes through the metal and heats it. Arc temperatures up to 3,000°C are used to melt metals.
Plasma arc heating:	A special type of electric arc heating, using plasma torches instead of graphite electrodes.
Electron-beam heating:	This technique employs a hot cathode for the production of electrons and a high voltage difference beaming those electrons at the target material.

Advantages of Electro Heating

Economic Advantages

Lifecycle cost is one of the first things to be taken into account when comparing the financial impact of two heating technologies. However, it is not always a simple matter to determine which factors should be included in this cost calculation. The investment cost and the energy costs over the lifetime of the installation are in most cases fairly easy to calculate. Other cost elements may be much more difficult to determine, since a production line with built-in electro-heat technology will often be conceived completely differently than a production line with a natural gas furnace. As a result, it might be necessary to calculate the lifetime cost of the complete line with all its investment, production, and maintenance factors to make a fair comparison. The result of such a calculation will be case specific.

Aside from the lifecycle cost, other economic arguments can be involved as well, such as the initial investment cost of the installation. Except for dielectric heating, electro-heat technologies generally score well on this point. In many cases this will be a major reason to prefer electro-heat technologies over heating techniques employing fossil fuel.

Another economic argument in favor of all electro-heat technologies is that electricity prices are less volatile than the prices of natural gas or other fossil fuels. Moreover, electro-heat installations often offer the opportunity to buy low-cost base-load electricity during low load periods of the day.

Finally, electricity is the major option for the future for all but a few energy using systems. Natural gas is a depletable energy source and its price will rise substantially long before the last reserves are cracked. The Energy Return On Energy Investment (EROEI) is a good measure for assessing the economic viability of an energy source. Today, the EROEIs of both oil and natural gas are in steep decline, showing that the most accessible reserves have already been used. This means that – even without taking climate change and other environmental issues into account – we will be forced to shift to a non-fossil-fuel economy at some point in the upcoming decades.

Logistic Advantages

Accessible technologies – Not only do electro-heat technologies often have a low initial investment cost thanks to their high power density, they are also compact installations relative to their production capacity. While this argument is especially true for infrared heating, it also holds for other electro-heat technologies. In addition, there are no fuel transport and storage issues involved, as with some fossil fuels. These advantages combine to make electro-heat technologies much more accessible and therefore popular among SMEs, especially in the metal and food processing industries.

Suitable for control and automation – The output of electro-heat appliances can be adjusted to a high degree of sensitivity and adapted to circumstances and the target material by regulating parameters such as frequency voltage and current. This makes electro-heat installations highly suitable for fully automated production lines. Electro-heat appliances are also highly flexible, thanks to the easy regulation of the output power and the ability to turn the installations on and off at high speed and without significant energy losses.

Environmental Advantages

Even when transmission and distribution losses are taken into account, electro-heat techniques still exhibit significantly better results than local fossil fuel heating systems in terms of CO2 emissions in the large majority of cases. Since the share of renewable energy in the generation mix is expected to continue its rapid increase in the upcoming decades, CO2 emissions related to electro-heat technologies will decrease further.

Further Information

• Industrial Electrical Heating: Applications

Leonardo Energy - Application notes:

• Application note: Introduction to industrial electrical heating
• Application note: Dielectric heating
• Application note: Induction heating
• Application note: Infrared heating