ClosedCarbonLoop (CCL)

The X-Energy sub-project ClosedCarbonLoop (CCL) is researching the optimization of the CO₂ cycle when using atmospheric carbon dioxide for power-to-gas (PtG) technologies. To this end, a plant consisting of electrolysis, biological methanation and reconversion to electricity (using combined heat and power generation) that already exists at the CC4E Energy Campus Technology Centre has been supplemented by a CO₂ adsorption plant, a so-called Direct Air Capture (DAC) from project partner Climeworks.

The plant uses a process to separate carbon dioxide from the ambient air, which is then used in a downstream methanation process to produce methane (CH₄). CO₂ production is divided into two processes. During the adsorption phase, the ambient air is fed through the reactor by means of a fan; part of the CO₂ contained is bound to adsorbent substances (so-called sorbents). In the second phase, known as desorption, the CO₂ is separated from the sorbent under negative pressure and through the supply of thermal energy. Once the desorption phase is complete, the cycle can begin again. This process is called the temperature vacuum swing process (TVS).

PtG and power-to-liquid (PtL) concepts will be necessary in the future to temporarily store large surpluses from renewable energies over a longer period of time. This will mostly require carbon sources to synthesize hydrocarbons such as methane (CH₄). In addition, not all CO₂ emissions are avoidable; a small amount will continue to be produced, as is the case in the food industry, for example. It is therefore important to realize negative CO₂ emissions by "capturing" CO₂ in order to achieve the set climate targets. However, the solution of using CO₂ from power plants is limited. It can only be implemented regionally and is not a general solution. The extraction of CO₂ from the air, on the other hand, is location-independent and not limited in quantity. DAC technology is also flexible in terms of operation time, which is essential for stabilizing the power grid.

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Further background information on the X-Energy sub-project ClosedCarbonLoop (CCL) can be found on the CC4E YouTube channel: How the direct air capture system at the Bergedorf Technology Center works. (only German)