ThermalBox®, a game-changing product to decarbonize industry process

Our system combines power-to-heat technology with thermal energy storage. By utilizing direct electrical heating of a circuit of molten salts, ThermalBox® generates 100% decarbonized process heat, in the form of steam or a fluid. A reliable and sustainable way to reduce carbon emissions and join to a cleaner future.

Designed to replace fossil fuel boilers

ThermalBox® is the innovative solution designed to replace fossil fuel boilers. Engineered for uninterrupted operation, it flawlessly delivers a continuous heat output of 1.5 to 10.5 MWt across standard configurations. This corresponds to producing 2 to 15 ton/h of slightly superheated steam (+10 °C) within a process pressure range of 5 – 30 barg.


Unmatched efficiency to decarbonize industrial heat with renewable electricity

ThermalBox® stands as the unparalleled leader in efficiently decarbonizing industrial heat through the utilization of renewable electricity. When comparing alternative methods, the difference in efficiency becomes strikingly clear. Producing hydrogen and applying it in a hydrogen boiler achieves an efficiency of c.57%. An electric boiler combined with a battery offers a higher efficiency of c.76%. Nonetheless, it is ThermalBox® that eclipses them all, boasting c.92% efficiency for heat production.

How it Works

Redefining thermal storage with unique design features

ThermalBox® sets itself apart with its innovative design, comprising two circuits that can operate either together or independently, tailored to renewable power source availability and process requirements. This unique capability allows for seamless integration of renewable energy sources while ensuring continuous heat production. Notably, ThermalBox® is designed to enable simultaneous charging and discharging, allowing to provide demand-side flexibility to the electricity network.

Operating at atmospheric pressure, ThermalBox® employs gravity for the circulation of molten salt, effortlessly transferring heat from the hot to the cold tank. This simple yet robust design enhances ease of operation and ensures secure functioning in the event of any system failures.


Molten salt at 180 °C stored in the low cold tank is pumped through the electric heater to the high hot tank at 400 °C


The molten salt is efficiently heated by an electric tubular heater, which operates on renewable energy. This ensures that the temperature reaches a reliable 400 °C, while keeping the surface temperature well below the salt’s chemical stability threshold and minimizing pressure loss.


The hot tank is designed to efficiently store thermal energy. The storage capacity of the system can be easily customized to meet the specific requirements of each application. By simply adding a pair of tanks (hot and cold) to the modular configuration of the ThermalBox®, the storage capacity can be increased as needed.


The shell and tube heat exchanger efficiently produces flexible process heat by utilizing molten salt in the shell and condensate/HTF in the tubes. Integration with the industrial process heat network is simplified by connecting to the existing heat collector at the appropriate pressure level.

Key Benefits

100% decarbonized process heat

Through electrification with a renewable energy source: hybridized on-site, PPA, and from a renewable grid.

Modular, adaptable & scalable

ThermalBox® can be customized for various industries and applications by combining standard components such as tanks, heaters, and evaporators.

Cost-competitive & quick payback

The Levelized Cost of Heat (LCOH) efficiently competes with that of fossil fuel boilers, ensuring a fast return on investment.

40 years of 24/7 thermal energy storage

ThermalBox® offers 4 to 12 hours of storage, allowing for fully flexible intraday operation with no limitations on charge or discharge cycles. Molten salts have a proven operational lifespan of over 20 years and are certified for 40 years.

Safe, flexible 
& digitally controlled

Remote monitoring, control applications, and plant control systems enable real-time demand flexibility services to the electricity network.
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On-demand flexible services

Optimizing Levelized Cost of Heat (LCOH)

Remote monitoring, control applications, and plant control systems enable real-time demand flexibility services to the electricity network.

Produce green heat by choosing or combining these 3 alternatives to power the ThermalBox® with renewable electricity

  1. On-site hybridization with a solar or wind generation plant
  2. Renewable Power Purchase Agreement (PPA)
  3. Connecting to a low emission electricity network

Build to Zero offers two delivery options


At Build to Zero, we offer a heat-as-service model where we take care of the entire process.

We deliver, install, and operate the ThermalBox® under a long-term contract. Working in collaboration with leading energy efficiency and renewable companies, we provide a comprehensive solution to our clients. This includes on-site solar PV or wind generation plants, as well as other Balance of Plant (BOP) equipment. Additionally, we partner with wholesale utilities and traders to help our clients negotiate renewable PPAs. This allows them to maximize revenue by leveraging the flexibility provided by ThermalBox® and delivering demand-side flexibility services to the electric system.


We also offer a CAPEX model to maximize efficiency and optimize capital investment for sustainable growth.

With this option, we deliver the ThermalBox® with configurations tailored to each client’s specific industrial process. Our team of experts in electrical, mechanical, and process engineering works to ensure maximum energy efficiency. We provide on-site construction and erection services through certified contractors, as well as start-up and operational services to ensure the ThermalBox® performs as expected. Integration with client control systems, complemented with remote monitoring and operational support, allows for seamless operation. We also provide on-site maintenance services and performance guarantees.

The simplicity and uniqueness of the ThermalBox® design are recognized through its registration under the Utility Model number U20233045, granted by the Spanish Patent and Trademark Office.

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