The materials that modern society depends on—iron and steel, cement, lime, aluminium, and critical minerals—are all produced using high-temperature industrial heat. Traditionally, most of that heat has been supplied by burning fossil fuels, creating a significant share of global industrial emissions.
The electrification of industrial heat offers a clear pathway to phase out the burning of fossil fuels in heavy industry. Electricity systems, however, are increasingly under strain as they themselves transition to incorporate higher shares of variable renewable generation and strive to meet growing demand from electrification and the rise of data centres. This creates a dual challenge. First, how can energy-intensive industrial processes be electrified without exposing operations to volatility and higher energy prices? Second, how can electrification of industry help, rather than hinder, the stability of the grid?
Calix is developing hybrid-electric mineral processing to meet this dual challenge. It aims to reduce costs and emissions for producers while unlocking the potential of energy-intensive industrial facilities to help stabilise the grid.
What is hybrid industrial heating?
Hybrid-electric industrial heating refers to heating systems that use two energy sources—electricity and combustible fuels—either independently or together, switching dynamically between them without interrupting production.
A useful everyday analogy is a hybrid car. A hybrid vehicle blends an electric motor with a combustion engine, automatically selecting the most efficient combination of power depending on speed, terrain and driving conditions. In the same way, hybrid industrial heating would blend electricity and fuel, choosing the most suitable energy mix as energy prices, grid conditions and operating requirements change.
Transition vs transformation: Why hybrid beats full electrification
Fully electric industrial heating promises the deepest emissions reductions over the long term, but there are real barriers to implementing this approach today. Electricity is often significantly more expensive, as an industrial energy source, than the fossil-fuel alternatives. Access to firm grid connections for electrified equipment can be costly, slow and uncertain. Long term baseload electricity contracts are expensive, and the liberalised electricity market (day-head / intra-day) is often too volatile for industrial assets, with extreme price swings in both directions.
Hybrid-electric heating offers a pragmatic alternative. Calix’s technology is now also being designed to provide two independent energy sources, fuel and electricity, within the same plant. This hybrid approach aims to enable industrial operators to shift between energy inputs: using electricity when it is cheapest (or negatively priced) and switching back to fuel when the electricity price rises again. In effect, hybrid systems can put a practical “cap” on energy costs. Combustion provides a stable baseline, while electricity can be used opportunistically as and when it delivers an economic benefit.
Electrifying large industrial facilities, such as cement plants, requires adding around 50–100 MW of demand to local grids. Many grids cannot guarantee meeting this demand without adding new supply or making other extensive and costly upgrades that can delay projects for years.
A hybrid solution can help avoid this cost and delay. By varying its electricity use in real time and relying on combustion when needed, a hybrid enabled plant may operate using whatever spare grid capacity is available at any moment with what is known as a non-firm connection. This may allow plants to be connected faster and for reduced transmission fees.
Taken together, these benefits mean a hybrid solution may enable faster and lower cost industrial electrification, with ongoing energy operating costs that will always be equal to or lower than a single energy source plant.
How hybrid heating works
In a hybrid configuration, heat can be supplied in two main ways. Burners may heat the tube externally using fuels such as natural gas, waste-derived alternative fuels, or biomass. At the same time, an electric current can be passed through resistive heating elements, including through the alloy tube itself. Either source can operate on its own, or both can operate together. The process is dependent on the temperature at the tube wall, agnostic to which energy input is being used. This design may therefore enable the balance between electricity and combustion to change quickly and smoothly, without disrupting the core production process.
Reducing cost, emissions and risk
Hybrid heating aims to deliver several practical advantages for operators of energy intensive plants.
Lower and more predictable energy costs. By dynamically switching between fuel and electricity, operators could consistently select the lowest cost energy source available at a given time, avoiding price spikes and reducing average energy costs.
Lower risk transition to electrification. Rather than forcing an immediate, all-electric transformation, hybrid systems may enable an electric transition. Rates of electricity consumption may be aligned with improvements in local grid capacity, renewable supply and market conditions. Flexible, non-firm grid connections are cheaper and faster.
Reduced emissions. Every unit of heat supplied by electricity instead of fuel reduces CO₂ emissions, especially as electricity grids continue to decarbonise. If a biogenic fuel is used within the hybrid-electric plant, then net-zero heating becomes feasible.
Reliability and resilience. Two independent heat sources provide redundancy. If electricity supply is constrained, fuel can maintain production; if fuel supply is disrupted, electricity can step in.
“Hybrid electrification aims to allow industrial plants to turn energy volatility from a risk into a competitive advantage—lowering costs, cutting emissions and unlocking new revenue streams—without compromising production.”
Calix Founder and Chief Scientist, Dr Mark Sceats
Turning flexibility into new revenue
Beyond cost savings, hybrid heating may unlock new potential revenue opportunities from grid services. A hybrid electric plant may adjust electricity use in response to grid signals; increasing its draw when renewable supply is abundant and reducing it when grids are under stress to meet demand. This flexibility aims to enable industrial plants to enter into grid services contracts, in which they are paid for their capacity to balance demand with supply.
These contracts can be lucrative, and existing industrial facilities are already undertaking grid balancing services. The flexibility of current plants, however, is often highly constrained. Certain existing electrified equipment may be turned down or off with advanced notice, and only for limited periods before it interferes with production. Conversely, Calix’s hybrid electric heating aims to enable producers to both increase and decrease electricity demand as needed, indefinitely, without interrupting production. As such, the plant’s capacity to provide grid balancing services is significantly increased.
With volatility in electricity systems set to grow, flexible industrial demand can be expected to become increasingly valuable to grid system operators, and hybrid electric industrial heating offers a unique solution.
Stacked value sources, stronger business cases
Importantly, hybrid heating aims to improve the overall economics of decarbonisation by stacking multiple sources of value. Lower energy costs could directly improve operating margins, while participation in grid services offers the potential to generate new, recurring revenue streams.
These benefits aim to strengthen the business case for adopting Calix’s technology, adding to existing potential sources of value, such as efficient capture of unavoidable process emissions, avoidance of carbon price liabilities, creating value from waste materials, and adding value to existing products. Rather than relying on a single decarbonisation lever, Calix aims to enable industrial plants to pursue a more flexible and resilient pathway to lower costs and lower emissions.
Towards commercial readiness
Calix’s hybrid heating concept builds on many years of technology development. Early incarnations of the technology demonstrated indirect heating using natural gas. More recently, multiple fully electric pilot and commercial demonstration plants have been built, including the now completed lithium Mid-Stream Demonstration Plant with PLS.
The most recently commissioned pilot-scale electric calciner at the Calix Technology Centre, known as Thor’s Hammer, included the first demonstration of direct electrification, in which the tube itself acts as a resistive heating element as a current is passed through it. This innovation has led to hybrid design opportunities by creating space for a second heat source within a single system.
Further work aims to deliver a hybrid design that integrates electric and combustion heating systems in a single plant and demonstrates rapid switching between energy sources in response to market conditions or grid signals.
Towards cleaner industrial heat and smarter energy systems
Hybrid electrification recognises a simple reality: the energy transition will not be smooth, and it will not happen overnight. Energy prices will be volatile, grid access will constrained, and grid instability will offer an increasingly important challenge.
For Calix, hybridisation may be a unique value proposition enabled by indirect heating. For industry, it offers the potential to de-risk electrification and improve competitiveness. For society, it aims to be a new tool to balance energy grids, reduce system costs and help usher in a lower cost and lower emissions way of making the materials we depend upon.
To learn more about our hybrid electric solutions, please contact enquiries@calix.global
