Daniel Stack, Electrified Thermal Solutions, explains the benefits of thermal energy storage systems for cement plants.
Global Cement (GC): Please can you introduce Electrified Thermal Solutions to our readers?
Daniel Stack (DS): Electrified Thermal Solutions was founded by myself and my co-founder Joey Kabel in 2021, with non-dilutive funding from the US government and the Activate Fellowship. Its mission is to electrify heavy industry, moving ‘hard-to- abate’ sectors away from fossil fuels. The company’s technology, now marketed as the Joule Hive, takes renewably-generated electrical power, be it solar, wind, hydroelectric or nuclear, and converts it to high-temperature heat for thermal processes.
GC: How was the Joule Hive developed?
DS: The novel technology behind the Joule Hive is E-Bricks. These are electrically-conductive aluminium oxide and chromium oxide bricks doped with semiconductor materials that were developed during my time at MIT. Joey, an expert in semiconductor ceramics, played a key role in improving the system in his role as Chief Technology Officer.
The E-Brick is essentially a large resistor, building up heat as electricity passes directly through it. The Joule Hive is a stack of many E-Bricks, a giant resistor. As electricity passes through the stack it heats up to 1800°C. When air or other gas passes around the bricks, it is heated to more than 1500°C. This can then be put to work in high-temperature industrial processes, including cement production.
GC: What were the main steps in the development of the Joule Hive?
DS: Scale-up has been very rapid. We have gone from working with a few bricks on the bench to a system the size of an elevator, and then to the 20MWh container-based Joule Hive in just three years. In January 2026, we commissioned the first Joule Hive at Southwest Research Institute in San Antonio, Texas. It can store 20MW of heat at peak temperatures of 1800°C and heat gas to up to 1500°C.
GC: That’s very fast...
DS: Yes... the rapid scale up has been possible due to the fact that E-Bricks contain only common materials. Indeed, they are 98% similar to standard refractory bricks. The other 2%, a combination of doping agents and other components for our proprietary blend, are also found around the world.
This meant that, once we got the formula right, it was very rapid to scale up. Any brick supplier that supplies the glass industry is capable of making E-Bricks. Proving that point, the first multi-tonne batches of E-Bricks are being made by Harbison Walker International, a member of Calderys, in the US, as part of an agreement we announced in 2025.
GC: What are some of the advantages of the Joule Hive over other thermal energy storage systems?
DS: The main issue with other thermal storage systems is that they rely on another material to heat the bricks, be it metallic elements, carbide rods or molybdenum disilicide. This is a problem because, given time, these materials will all oxidise and decay. They will need to be replaced, and - even worse - the higher the temperature goes, the faster the burn out. This is unreliable and will cost a lot of money at the high temperatures needed by the cement industry. The longevity and reliability of the E-Bricks is the Joule Hive’s big advantage. The E-Bricks never oxidise because they are already oxides, as are the additives.
Another big advantage is that we can run at high voltages, between 10kV to 100kV. These are the kind of voltages that enter industrial sites around the world. There’s no need for stepping down the voltages, which requires a lot of copper conduit and other components. This reduces the cost of the installation substantially and gives Electrified Thermal Solutions a distinct advantage over low-voltage systems when it comes to scaling up.
GC: What will be the first applications to adopt this technology?
DS: Cement is certainly one of the major applications, but we are also targeting steel, aluminium, glass and other high-temperature industries. This is reflected in some of our investors: Holcim MAQER Ventures in the cement industry, Arcelor Mittal through its XCarb Innovation Fund from steel, Vale Ventures from iron ore and the venture arm of Tüpraş, the Turkish petrochemical company. Buzzi is also on board as a partner.
There is a universal need for high temperature gas and these companies, while they are thinking about their sustainability credentials, are also thinking about cost. It is already cheaper to use heat from a Joule Hive than it is to use the dominant fossil fuel in many markets.
GC: How would a cement plant use the Joule Hive?
DS: A typical cement plant demands ~150MW. Each Joule Hive can supply 5MW at present, so a simple calculation says the plant would need 30 of them. We can deploy an array of units to deliver the hot gas to the calciner, the preheater tower, and to the rotary kiln itself down the centre of the shaft to deliver the heat rates that the plant needs.
Of course, each plant is different, so we would need to look at the profile of the plant to see how the system needs to be plugged in. It won’t happen overnight, but we can - today - plug in and partially replace the heat going to the preheater tower or the rotary kiln. As we move forward, we would look to advance that to the majority or eventually all of the heat coming from the Joule Hives.
GC: You mentioned that the system can use air or other gases? What would the cement sector use?
DS: Air is the default ‘universal fluid’ that is used to deliver heat to heavy industries, because it is all around us. In the cement industry, however, it makes more sense to develop a CO2-based system. If the aim is to remove fossil fuels altogether, it becomes possible to loop CO2 between the Joule Hive and the plant. This means that the atmosphere of the cement plant would be CO2-rich, with continuously-evolved process CO2 collected and taken for storage or utilisation. This kills two birds with one stone - remove fossil fuels, with all of their impurities - and make it easy to capture the CO2. That’s the dream!
GC: What’s the lead time for a Joule Hive?
DS: Installation is not as complicated as other novel technologies. We just need a connection to the incoming power supply, a concrete base and some ducting to the process itself. A project to install a small number of Joule Hives could be completed within less than 12 months. On-site installation time itself is only about two months.
GC: How will the process develop in the future?
DS: The containerised Joule Hive, as we see it today, is only a stepping stone towards larger systems as, for Gigawatts of power, we would need hundreds of containers. Instead, we envisage purpose-built tower structures for large users, like the steel sector, possibly for cement too. We can scale up by using larger units, not just adding more units.
GC: What are your 5 - 10 year aspirations for this technology?
DS: We have ambitious plans to expand very rapidly. Firstly, the demand is there. Indeed, it is now cheaper to use electricity as an energy source than the established fossil fuel, between 20 - 50% of the time. While North and South America and Europe are at the front of this trend, the same is increasingly true in all regions of the world. If we can save producers money, the demand will be there. Secondly, the system we built in Texas is now in operation and can be replicated anywhere across the world in the next 12 - 15 months.
So, the Joule Hive tackles the emissions challenge, but also saves the industry money, while leading to a more prosperous industry and society by having electrification as a pathway. Our goal is to deploy Gigawatts of heat by 2030, with a vision of full industrial electrification by 2045. We want to plug Joule Hives into every furnace, boiler and kiln on the planet!
GC: We wish you the best on this mission.
DS: Thank you - It was good to talk!
