Electric Heat Is Inefficient
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Electric Heat Is Inefficient

An email from the Economist magazine describes a new way heat intensive production processes are trying to use electricity rather than burning fossil fuels. I don't think it is going to work. I lived in a house that had a heat pump and froze most of the winter. Electricity does not produce warmth well. Fire and the wheel are what enabled man to develop civilized society. Banning fire is not going to make society better. Electricity can do many things well, but heating with it is inefficient.

Anyway, the article by Paul Markillie says:

Having explored a lot of factories and industrial plants, I have learned that there is one thing that inevitably comes with the territory: heat. For most goods there is usually one stage of production or more in which things need warming up. In the manufacturing business this is known as “process heat”. It might require a few hundred degrees Celsius to cook or bend something, or to mould plastic parts; a thousand to make steel; or more than 1,400°C in a kiln to transform limestone into cement.

Some of this heat is produced by using electricity, typically by passing a current through an element. This is good for roughly 400°C or so, but it gets trickier after that. One reason is that at very high temperatures the materials from which standard heating elements are made could start to melt. Which is why most very hot processes burn fossil fuels to generate heat.

But times change and industry is now looking to a carbon-free future. And for good reason, because just three industries that use lots of heat—chemicals, steel and cement—account for the lion’s share of industrial carbon emissions. Their heat requirements make them some of the toughest industries to clean up. Whereas producers that require lower temperatures can relatively easily electrify their processes, and thus run their operations on green renewable power, that is not always possible for the hot crowd. 

This week, I took a look at a novel method of generating high-temperature process heat that could change all that. The system has begun trials at a test centre in the Netherlands. It uses electricity to produce 1,000°C of heat for steam cracking. This process is employed in petrochemical plants to convert naphtha, which is largely obtained from crude oil, into the chemical building blocks used by the plastics industry.

The machine being tested resembles a turbine used in power stations to produce electricity from natural gas. In this case, though, it runs in reverse. Ordinarily, a gas turbine burns fuel to produce fast-expanding gases that turn a series of rotors connected to a shaft. This shaft then drives a generator to make electricity. The RotoDynamic unit, as it is called, instead uses an electric motor to spin a series of rotors that rapidly accelerate and decelerate gases or liquids. The huge amount of kinetic energy this creates results in lots of heat.

Coolbrook, a Finnish engineering firm that developed the RotoDynamic system, reckons it will be good for producing temperatures of up to 1,700°C. That means it could be used to electrify production of a number of energy-intensive products, including petrochemicals, steel, cement, glass and ceramics. And if run on electricity from renewable sources, that could cut emissions in those sectors substantially.

There is some way to go before the trials will show if the system is likely to be commercially successful. After naphtha cracking, it will be tested on other industrial processes. But already a number of big companies are looking at trying it out as part of their efforts to create green heat.

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