## 4.7 Carbon capture and storage (CCS)

### 4.7.1 Technologies

This module introduces the Carbon Capture and Storage (CCS) in the model. For CCS, supply costs of injections and sequestration reflect sites availability at the regional level, as well as energy penalties, capture and leakage rates. CCS can be used with Gas, Coal, and Biomass power plants in the model and competes with traditional fuel power plants for a sufficiently high carbon price signal.

The following table summarizes the main parameters related to the CCS technologies.

Coal pre-comb Coal post-comb. Coal Oxyfuel Natural gas Biomass
Capacity factor [%] 81 83 83 84 80
CO$$_2$$ Capture rate ratio [%] 89 90 95 89 90
Net efficiency [% on LHV basis] 33.88 33.7 33.15 47.99 28
Lifetime 40 40 40 25 25
Investment cost [$/kW] 3077.7 3063.4 3252.9 1508.4 3693.2 O&M costs [$/MWh] 10.15 13.44 9.54 6.41 10.33
Learning rate [%] 6.7 3.8 2.8 4.2 5
Floor cost [\$/kW] 1472 1472 1472 750 2000
Capacity before learning [GW] 7 5 10 3 10

Retrofitting Coal plants operative in 2015 represents an alternative to CCS technologies. Retrofitting is defined as an investment cost for the retrofitting unit and differential effects for a subset of the existing coal capacity, namely efficiency drop of 10 percentages points and introduction of CO$$_2$$ capture.

### 4.7.2 Transport and storage

CO2 can be stored in seven different types of geological reservoir with an own cost, differentiated across regions in terms of distance from the plant and maximum storage capacity. The quantity of carbon captured, $$Q_{CCS}$$, is computed for all CCS technologies according to a specific capture rate ratio:

$Q_{CCS}(t,n) = \sum_{f,j} Q_{f,j}(t,n) \times ccs\_capture\_rate(j)$ This quantity can be stored in different sites $$k_{st}$$ and the following balance is satisfied for each region:

$Q_{CCS}(t,n) = \sum_{k_{st}} Q_{st}(k_{st},t,n)$ where $$Q_{st}$$ is the quantity stored per year. The total amount of storage needed $$M_{CCS}(k_{st},t,n)$$ is then computed cumulatively: it is initialized equal to zero, and accounts for possible CO2 leakage (due to a percentage leakage factor $$\lambda_{st}$$).

$M_{CCS}(k_{st},t,n) = M_{CCS}(k_{st},t-1,n) \times (1-\lambda_{st}) + \Delta_{t'} \times Q_{st}(k_{st},t,n).$ $$M_{CCS}(k_{st},t,n)$$ is constrained by an upper bound, representative of the maximum available storage capacity in each region. Leakage from the reservoir is accounted for and is included in the global emission balance. However, the default leakage rate is set equal to zero.

$Q_{CO2lk}(t,n) = \lambda_{st} \times \sum_{k{st}} M_{CCS}(k_{st},t,n)$ The costs for CCS transportation and storage $$C_{CCS}(n,t)$$ are then an increasing step function of the cumulative sequestrated emissions, where the parameters are chosen to calibrate transport and storage costs suggested by Rubin, Davison, and Herzog (2015) and capacity of storage to the available estimates, notably (IEAGHG 2011), who estimate a total storage capacity of 11096 GtCO2.

$C_{e}(n,t) = \sum_{k_{st}}Q_{st}(k_{st},t,n) \times (c'_{tr} \times l_{tr}(k_{st},n) + c_{st}(k_{st})), \forall e \in \{CCS\}$ The unit cost of transport and storage is evaluated as: $C_{CCS}(n,t) = C_{e}(n,t) / Q_{e}(t,n), \forall e \in \{CCS\}$

### References

Rubin, Edward S., John E. Davison, and Howard J. Herzog. 2015. “The Cost of $$CO_2$$ Capture and Storage.” International Journal of Greenhouse Gas Control 40 (September): 378–400. doi:10.1016/j.ijggc.2015.05.018.

IEAGHG. 2011. “Potential for Biomass and Carbon Dioxide Capture and Storage.” IEA Greenhouse Gas R&D Programme.