It is based on a CO₂ heat pump, which is connected with a storage unit. Conversely to synthetic refrigerants, carbon dioxide (CO₂) is a natural, non-polluting refrigerant, neither ozone-layer-damaging nor climate-effective. For the required temperatures of more than 55°C, CO₂ heat pumps show a significantly higher efficiency than conventional appliances. From system-technical view, they are ideally to complete solar storage appliances.

The combination with the solar heat transfer medium and the specific demands of the CO₂ cycle require innovative solutions. The Institute for Thermodynamics at the Technical University Brunswick develops two variants of this new heat supply system based on a CO₂ heat pump: a low-power-version with large storage unit, a powerful version with a small one. Goal is to develop an overall control concept for heating systems. It appears that heat supply systems combining a CO₂ heat pump with a solar storage unit require considerable less primary energy than the system combining gas and solar energy.