Turning buildings into flexible energy assets.
Cartesian builds compact thermal batteries that turn buildings and factories into flexible energy assets — heating, cooling, and everything in between.
- Heating · −20 → 120 °C
- Cooling · sub-zero to chilled
- 25-year design life
Partners
We build with leading research institutions, technology partners and public innovation programmes across Europe.
Compact
5× the energy density of water — fits where water storage never could.
Modular
Plug in another module to scale from 50 kW to 5 MW thermal.
Bankable
25-year design life, non-flammable, low-maintenance.
Circular
Reusable PCMs, recyclable steel and zero greenhouse-gas refrigerants.
Solutions
One thermal battery, six ways to increase your thermal capacity.
Increase cooling capacity
Add chilling capacity to existing installations without upsizing chillers or compressors.
- +25% installed capacity
- No chiller upsize
- Quieter daytime operation
Increase heating capacity
Cover peak heating demand by storing thermal energy off-peak — keep your heat pump small.
- Avoid heat pump upsize
- Stable peak supply
- Lower OPEX
Reduce grid peak demand
Shift load away from peak hours and tariff windows to cut demand charges and grid stress.
- Lower kW demand charges
- Decouple from grid peaks
- Avoid grid upgrade fees
Unlock computing power for data centres
Free up cooling capacity for additional racks — without any expensive grid or chiller upgrade.
- Backup cooling support
- Better use of on-site PV
- Potential revenue from grid flexibility
Compact thermal storage for urban projects
A practical alternative when energy wells, noise limits or rooftop space rule out conventional storage.
- 5× less volume than water
- Silent operation
- Indoor or outdoor
CO₂ heat pumps & domestic hot water circulation
Stable, efficient domestic hot water — cut compressor cycling and avoid electric or gas backup.
- ~19 000 kWh saved / yr
- No electric backup
- Charging with COP ~4
- Improved seasonal performance
Where we deliver
Built for the buildings that run the world.
From hyperscale data centres to neighbourhood heat networks — wherever heating or cooling matters, Cartesian unlocks flexibility.
Commercial and public buildings
Cut peak loads and energy bills across offices, retail, schools, hospitals and other public buildings.
Data centres
Maximize the revenue within your limited grid connection.
Logistics centres and warehouses
Protect the cold chain and add cooling headroom on peak days — without waiting for a bigger grid connection.
District heating or cooling
Defer pipe upgrades, integrate waste heat, balance grids at the edge.
Energy Service Companies
Invest in a thermal energy asset that provides consistent savings over 25 years.
How it works
Norwegian engineering, packaged as a thermal battery in a box.
Phase change materials store heat or cold when they melt and freeze. We package that physics into a compact, modular battery — and the controls that make it pay back.
Charge
When energy is cheap, clean or surplus, the Thermal Box absorbs heat or cold using phase change materials.
Store
PCMs change phase at exactly the temperature you need — banking 5× more energy per litre than water, with minimal losses.
Discharge
When demand peaks, the smart pump skid releases energy back into your existing HVAC, process, or grid.
Optimise
The controller cycles automatically against spot prices and CO₂ signals — every hour, all year round.
Patented · Made in Norway
A decade of phase change engineering, productised in Trondheim and shipped to projects across Europe.
Products
A complete kit. Engineered to retrofit.
Thermal Box Basic
The core Thermal Box module, delivered ready to integrate. Pumps, valves, controls and balance of plant are sourced by the contractor or system integrator.
- Storage capacity
- 60 – 125 kWh per module
- Heating / cooling output
- 20 – 35 kW per module
- Temperature range
- −20 °C to +120 °C
- Round-trip efficiency
- 98 %
Thermal Box Standard
Thermal Box delivered in a pre-assembled cabinet with circulation pump, energy meter, required valves and a Building Management System controller — ready for integration into your local Building Management System.
- Includes
- Thermal Box + hydraulic skid + controller
- Integration
- Ready for local Building Management System
- Storage capacity
- 60 – 125 kWh per module
- Lifetime
- 25+ years
Thermal Box Advanced
Everything in the Standard offering, plus a cloud-based management system with options for local integration into the Building Management System. Spot-price and CO₂-aware optimisation, remote M&V and over-the-air updates.
- Includes
- Standard + cloud management
- Optimisation
- Spot-price & CO₂ aware
- Monitoring
- Cloud dashboard · open API
- Integration
- Local Building Management System + remote
Product catalogue
The single PDF most engineers ask us for.
Capacities, operating temperatures, footprints, hydraulic and electrical integration notes — the full Thermal Box product family in one document. Hand it to your engineer, your installer or your bank.
- Module specifications
- Hydraulic schemes
- Indoor & outdoor
- Sizing guidance
References
Real installs. Measured savings. Happy buildings.
Cutting peak demand at a Trondheim office
More than 100 000 NOK in annual savings — and a smaller grid connection.
- peak demand reduction
- ~38%
- annual savings
- 100k NOK
- operational disturbance
- 0
Smart cold storage for an everyday supermarket
Lower energy consumption and a more resilient cold chain — without changing the recipe.
- energy use
- −22%
- captured at night
- Free-cooling
- no shutdown
- Retrofit
Storing solar energy in a zero-emission lab
A real-world testbed for the role of thermal storage in zero-emission buildings.
- stored on-site
- Solar+
- balance achieved
- ZEB
- open dataset
- R&D
Recognition
Backed by accelerators, juries and the trade press.
Independent validation that the Cartesian playbook scales beyond Norway.
- 2025 · Climate cohort
Amazon Sustainability Accelerator
Selected for Amazon's 2025 climate cohort — 12 weeks of growth support and access to Amazon's European sustainability network.
- 2025 · Winner
Nordic Innovation Award
Inaugural winner of the Nordic Innovation Award, presented in Copenhagen by the Nordic patent authorities.
- 2025 · Nominee
ISH Frankfurt — Designplus
Nominated for the Designplus Award at ISH Frankfurt, the world's leading trade fair for energy and heating innovation.
Common questions
Got questions about thermal storage?
From PCM chemistry and lifetime to indoor vs outdoor installs and typical payback — the answers are in the full FAQ.
Read all questionsWhat is thermal energy storage?
The term is used when storing energy as heat or cold, which can be released at a later stage. The heat or cold is usually stored when energy is cheap and then released when the heating or cooling demand is at a peak or the cost of energy is high.
What is PCM?
PCM means Phase Change Material and refers to any material that changes state, for example from solid to liquid, when reaching a certain temperature. This phase change enables large amounts of energy to be absorbed or released. Water is one PCM, storing cold at zero degrees Celsius by changing phase to ice. Cartesian uses a wide variety of other materials, such as bio-based waxes, to store heat or cold at different temperatures.
Is the Thermal Box and the PCM flammable?
For applications with HVAC systems, Cartesian's Thermal Box is not considered flammable. While some PCM might be flammable when they reach temperatures above 100 °C or more, the Thermal Box is designed to eliminate any risks of reaching flammability conditions in operations.
Are PCMs safe?
Cartesian offers only safe PCMs and primarily uses bio-based PCMs in the Thermal Box. The PCM will stay in the Thermal Box for its whole lifetime and is not consumed during operation. The Thermal Box is also designed to avoid any risk of PCM leakage.
Let's build the smarter grid