How heat could solve climate problems

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It's finally springtime in New York. The skies are clearing up, the trees are blooming, and I'm already wishing I could bottle up all this sunshine to save for when winter comes around again.

While I can't change the weather (not yet, anyway), it's wild to think about just how much control many of us have over the temperature in most areas of our lives. We can set the thermostat to precisely 72 F, take hot showers, and even step into a warm car on a cold day.

But there's another arena where our mastery of temperature control is less visible, but arguably even more important: the manufacturing processes that make the building blocks of our lives. Having heat on demand is necessary for making ... pretty much everything.

The problem is, temperature control in industry has historically relied on fossil fuels like coal and natural gas, and it's a bit of a climate nightmare: industrial heat alone is responsible for about 20% of emissions globally. A growing number of folks are looking for new ways to fiddle with industrial thermostats, so let's take a look at what technologies are on the table and where we go from here.

Heating up

When I say heat is used everywhere in industry and manufacturing, I mean everywhere. But what that looks like can vary pretty widely.

Some industries, like food and paper-making, require relatively low temperatures. For example, extending milk's shelf life by killing off harmful bugs via pasteurization requires getting it to temperatures under 100 C (212 F). On the other hand, making steel can require getting up to around 1,500 C (2,700 F) to melt iron and kick off chemical reactions that strengthen the metal.

In total, three-quarters of all energy used by industrial processes is in the form of heat, and only one-quarter is electricity. So while many of us are focused on how to clean up the electrical grid that powers our homes and an increasing number of our vehicles, industry will have an even bigger job ahead trying to address its heat demand.

In September 2022, the US Department of Energy announced a program called the Industrial Heat Shot, aimed at developing technologies for industrial heat that cut emissions at least 85% by 2035.

What I think is really interesting here is that because different industries need vastly different ranges of heat, we could see the development of a whole bunch of technologies.

Burning up

One tried-and-true method for generating heat is burning something like fossil fuels. The only problem is that they spew carbon dioxide and other powerful greenhouse gases into the atmosphere. If we want to hit our climate targets, we need to set fire to something else.

Many are looking to hydrogen as a versatile, climate-friendly fuel. The benefits are clear: burning hydrogen just produces water, and it could reach the ultra-high temperatures needed for some of the most pollution-intensive industries, like steel and cement production.

Where the hydrogen comes from will matter, though. Gray" hydrogen, which is generated using natural gas, would sort of defeat the purpose of the switch. Green" hydrogen, which is made using renewable electricity, would be a more climate-friendly route, though it would require a massive new amount of that electricity.

Just replacing today's hydrogen production from fossil fuels with green hydrogen would require about 4,500 terawatt-hours of electricity, comparable to total US generation. And we're going to need a lot more hydrogen than what we're currently producing if it's going to be used more widely in industry.

An aside: carbon capture and storage could allow some industrial processes to continue heating with fossil fuels while capturing resulting emissions. The technology is still expensive and has not been proven widely, though, which is why many caution against relying on it too heavily.

Charging up

For situations that don't require quite such high temperatures, electricity could step into the ring.

You might remember my story on heat pumps from a couple of months back: these seemingly magical devices use electricity to move heat from one place to another. Heat pumps can be used to heat and cool homes, and new developments could allow the devices to supply heat for industry.

Today's heat pumps can commonly deliver temperatures up to around 100 C (212 F). But there are some early demonstrations and prototypes of industrial heat pumps that can reach 200 C (400 F), which could work for about half the total heat use in US industry, according to research from the National Renewable Energy Laboratory.

The problem with using electricity for heat is the same as the problem with using electricity in general: if you want to use renewables, you need to figure out how to make sure electricity is available when it's needed.

Many industrial processes don't turn on and off on a dime, so even if the wind stops and the sun sets, you need to be able to keep the process running. Batteries could help, and so could nuclear, geothermal, and all the other solutions people are working on to smooth out the grid.

But a growing number of startups are working on another way to use electric heat in industry: heat batteries." These devices use a mechanism similar to the one in a toaster to turn electricity into heat, which is then stored in stacks of bricks. It's a unique approach to energy storage, and to using renewable electricity.

I wrote all about these mysterious hot bricks, so if you want to know more, check out my story from Monday.

If heat batteries prove to be effective and reliable, they could play a big role in cleaning up industrial heat. But ultimately, hydrogen, heat pumps, and a host of other technologies will probably need to play a role for industry to hit its climate goals.

Related reading

• Cheap renewable energy is making green hydrogen competitive with fossil fuels.
• Here's how electricity and hydrogen could clean up heavy industry.
• We're entering the era of the heat pump. Here's everything you need to know about how they work.
• I truly can't stop talking about hot bricks.

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