The Thermal Box module — integrate with your own balance of plant
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.
Thermal Box Basic is the bare module — the Cartesian thermal battery, delivered ready to integrate. Designed for contractors and system integrators who source their own pumps, valves and controls and want full control over the balance of plant. Each module stores 60–125 kWh, delivers 20–35 kW of heating or cooling and fits the footprint of a Euro pallet (1.2 × 0.8 × 1.8 m), weighing around 2 000 kg.
The bare Thermal Box module — for integrators who source their own hydraulics and controls.
Get a sized concept
Just the module
Thermal Box module, insulation and documented thermal interface — nothing else.
5× more compact
Up to 5× less volume than a water tank for the same stored kWh.
−20 to +120 °C
PCM library covers cooling, low-grade heat and high-temperature heat.
25+ year design life
Stable PCM cycling. No moving parts. Non-flammable.
Specifications
- 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 %
How it works
From the shop floor to your roof — in four steps.
- 01
Specify the PCM
Pick the melting temperature that matches your set-point — we have a library from −9 °C to +71 °C.
- 02
Engineer your hydraulics
You design the pump skid, valves and controls around the Thermal Box's documented thermal interface.
- 03
Install and connect
The module is delivered on a Euro-pallet footprint, ready to wire into your hydronic system.
- 04
Charge and cycle
Cycle once a day — over 10 000 cycles without performance loss.
What's included
Everything you need to ship a working install.
Pre-engineered, pressure-tested and certified before delivery — so commissioning takes days, not weeks.
- Modular steel cabinet (Euro-pallet footprint)
- PCM-filled stainless modules tuned to your set-point
- Insulated panels (≤ 0.05 W/m·K)
- Top vent collars for hydronic connections
- Documented thermal interface for integration
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.
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