Theory 096/Energy & Environment /Carbon capture
Capture Penalty Is a Temperature Ratio
Sorbents are ranked by capacity. The penalty may be decided by how far the temperature must be raised.
The energy penalty of carbon capture is set by the ratio of desorption temperature to the source temperature rather than by sorbent capacity, so a low-capacity sorbent with a small temperature swing can outperform a high-capacity one with a large swing.
01The evidence
Capture penalties vary between sorbents in ways that do not track capacity, and the variation tracks regeneration temperature.
02The tension
Sorbent development targets capacity, which predicts penalty from how much is captured per cycle and ignores the heat needed to release it.
03The mechanism
Regeneration requires raising the sorbent above the binding temperature. The heat required scales with the temperature lift and with the heat capacity of the bed, not only with the amount captured.
That makes the temperature ratio the determinant, and predicts penalty should track it better than capacity.
04What this is not
Capacity ranking predicts penalty from uptake. This predicts from lift, which explains the poor correlation.
05Predictions
- P1Penalty should track the temperature ratio.
- P2Low-lift sorbents should win despite lower capacity.
- P3Lift should predict better than capacity.
06Refutation
Penalty tracking capacity at controlled lift would restore capacity ranking.
07What it changes
It would change sorbent selection criteria.