Heat in the industrial sector

The heat transition in the industrial sector is a key part of making industrial processes climate neutral.

Whether it is drying, smelting or forging – technical processes in industry would not be conceivable without process heat. More than 60 per cent of the industrial energy demand in Germany is used for this purpose.

 

The industrial sector in Germany needs around 504 terawatt-hours (TWh) a year to produce process heat. At the same time, the various branches of industry and industrial processes have very different requirements in terms of temperature level: whereas a minimum temperature of about 160 degrees Celsius (°C) is sufficient for drying paper, combustion and smelting processes need temperatures well above 1,000°C. Such high temperature levels are required for about half of the industrial process heat, especially for metal production and processing, but also in the cement, glass and ceramics industries. About a quarter of companies in the chemical and engineering sectors need average temperature levels of around 500°C. Demand for temperature levels of up to 100°C only accounts for about ten per cent, for instance at companies in the food industry. In North Rhine-Westphalia, the chemical, iron and steel industries are the biggest consumers of heat.

Cooling systems also come under heating applications, but the energy demand for industrial cooling systems and air-conditioning in buildings accounts for a relatively low percentage calculated at 30 terawatt-hours.

 

Strategies and policies for the heat transition in the industrial sector

With a 75% share, fossil fuels such as coal, gas and oil still supply the bulk of industrial heat, leading to substantial emissions predominantly associated with generating process heat. The main fields of action to reduce these emissions can be loosely divided into four areas: increasing efficiency, i.e., among other things using internal or external waste heat, incorporating renewable sources of heat as far as possible, electrification using renewable electricity and using alternative sources of energy, such as green hydrogen for example. A huge volume of emissions can be cut by increasing efficiency and switching to renewable energy. Various approaches and technologies are feasible in this respect depending on the required temperature level.

Increasing efficiency: avoiding waste and using waste heat

The economic potential for increasing efficiency has already largely been exhausted in many conventional industrial processes. Furthermore, all of the technical potential needs to be tapped in the future. Above all, it is important to reduce primary heat demand by optimising or converting processes and preventing heat loss, e.g. through optimal insulation, because: heat that does not need to be produced in the first place has the best carbon footprint. Beyond that, “unavoidable” waste heat can be utilised in a variety of ways. For example, factories and businesses can use it directly for preheating processes, to heat premises and to heat water. Alternatively, it can also be fed into a local or district heating network and thus made available to external parties, for example a local business, or to heat buildings in urban districts.

 

Converting to electricity is also possible. If the temperature of the waste heat is too low to utilise, it can be increased using heat pumps, for example. Waste heat utilisation offers great potential for climate protection since nearly half of the energy used to generate heat is still currently being lost as dissipated heat. A recent analysis of potential by the North Rhine-Westphalia Agency for Nature, Environment and Consumer Protection assumes 88 to 96 terawatt-hours of technically available waste heat per year in NRW, of which around half (44 to 48 terawatt-hours) is reckoned to be technically usable – this would equate to a CO2 reduction of up to 13 million tonnes per year. When developing the much-discussed prospective hydrogen infrastructure, further waste heat sources can be expected, particularly from electrolysers.

All change: using renewable sources of heat

The upside is that there are no additional conversion losses when using renewable heat. The downside, however, is that renewable sources of heat at temperature levels that are technically and economically usable for industrial purposes are only available to a limited extent in NRW. 

In this country, temperatures of up to about 250°C can be generated using solar thermal power with what are known as non-concentrating collectors, which use both direct and diffuse solar radiation. However, this type of heat production is extremely volatile and depends on the time of day. If combined with a heat accumulator, however, solar heat can offer sound support to generate renewable heat for low temperature applications such as drying and heating processes, e.g. in the food industry.

 

The use of deep geothermal energy, also known as deep geothermics, involves drill depths of over 400 metres. The temperatures that can potentially be achieved are heavily dependent on the location and the quality of the subsoil. In NRW, large segments of the subsoil have yet to be sufficiently investigated, but this area is presumed to have great potential. With geothermics, it is possible to achieve temperatures of up to 180°C at depths of several kilometres. One great advantage is its base load operation capability, which means that it is not subject to fluctuations due to the time of day, time of year or the weather. For this reason, it is suitable for providing a reliable supply for industrial processes at lower to middle temperature ranges (e.g. drying processes in the paper industry) and can also be combined with heat pumps if necessary to boost the temperature level.

Electrification: heat from renewable electricity

The opportunities for converting electricity generated by renewable resources into heat are manifold and are amalgamated under the term “Power-to-Heat”. If heat is produced using electricity, no direct greenhouse gas emissions arise. A key prerequisite for becoming neutral along the entire efficiency chain, however, is that electricity is produced sustainably, e.g. from sun, wind or water, and that the proportion of renewable energy in the electricity mix on the grid is increased considerably.

 

Factories can operate electrode boilers for instance, which convert electricity into hot water or steam. These systems can reach maximum temperatures of several hundred degrees. Until now, however, process steam has mainly been produced using fossil sources, since natural gas is still a cheaper fuel than electricity. Moreover, electrification using the electricity mix currently available is not yet advisable from a climate protection perspective. Nevertheless, there are potential advantages: the level of efficiency when using electricity in a boiler is high and electrode boilers can easily be integrated into systems at relatively low investment costs.

 

Heating technologies that use conduction (by means of electrical resistance), induction or electrical arcing, for instance, offer further options for generating heat from electricity with a view to heating or even smelting glass, aluminium and steel.

 

In the future, industrial companies could potentially even use surpluses from volatile renewable energy production to generate the heat they need in a flexible and cost-effective way, thus making a contribution to storage and grid stabilisation.

Defossilisation: using alternative fuels

When using alternative energy sources, we must also always take conversion losses in power production into account. If power from renewable sources is used directly for heating purposes, overall efficiency is greater than it is when using electricity for power-to-gas processes to produce hydrogen or synthetic methane, which is then subsequently used for heating. 

 

Faced with the target of completely avoiding CO2 emissions, we need to minimise our use of carbon-based fuels (those containing carbon), since it is otherwise inevitable that carbon dioxide is given off when they are burned. This is known as decarbonisation. In industrial processes where neither heating using renewable sources nor electrification are feasible, combustion processes are likely to continue to be required in the future. Green hydrogen offers the advantage that only steam is emitted when it is burned. The deployment of present-day gas burners and ovens using hydrogen technology, e.g. in high-temperature production for metallurgic processes, in rolling mills and foundries and in glass manufacture, needs to be investigated, developed and tested.

 

Carbon-based fuels continue to be necessary in a few industrial processes. For instance, carbon is needed for special alloys in the metalworking industry and in heat treatment furnaces for very large components, since the high temperatures and radiant heat required can only be achieved using carbon-based gaseous fuel. In the chemical sector, carbon is also needed as a feedstock for a whole series of products. Complete decarbonisation is not possible in these cases. However, in future, the carbon should no longer be of fossil origin – this is known as defossilisation. Potential sources of energy include biomass, biomethane and synthetic methane, for example. Sustainably exploitable quantities of biomass and biomethane are limited, however, so we must use it in as targeted and efficient a manner as possible. Research and development is currently still needed into the area of simultaneous material and energetic usage in the chemical sector and in the metalworking industry. For example, tests are being carried out on substituting conventional coke with what is known as “bio coke” in the iron and steel industry.

Schaubild symbolisiert vier Stufen: Steigerung der Effizienz, Erschließung erneuerbarer Wärmequellen, elektrische Wärmeerzeugung und alternative Energieträger

Four-stage model of a climate-neutral process heat supply

Säulendiagramm veranschaulicht die erreichbaren Temperaturen, am höchsten u.a. grüner Wasserstoff mit 1.500 Grad Celsius

Achievable temperature on the basis of renewable energy sources in NRW and potential future industrial applications (see the discussion paper on climate-neutral industrial heat).

Ein Schaubild zeigt die Wirkungsgrade, am höchsten ist er bei der direktelektrischen Wärmeerzeugung (97%), also Power-to-Heat

Efficiency chains and conversion losses in Power-to-Heat, hydrogen combustion and the combustion of synthetic methane based on the example of process steam generation (see the discussion paper on climate-neutral industrial heat).

You will find further information on these pages

You want to learn more about hydrogen as an energy carrier of the future? Then click here.

You want to learn more about hydrogen infrastructure? Then click here.

You want to know more about production and colors of hydrogen? Then click here.

You want to learn more about electrical power production? Then click here.

Want to find out more about handling CO2? Then click here.

Your contact

Portrait der Projektmanagerin Industrie und Produktion Tania Begemann vor einer Glasfront.

Tania Begemann

Project Manager Industry and Production

Phone: +49 209 408 599-11

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Portrait des Projektmanagers Industrie und Produktion Dr. Stefan Herrig vor einer großen Glasfront.

Dr. Stefan Herrig

Project Manager Industry and Production

Phone: +49.209.408599-10

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