Estimating the learning rate of a technology with multiple variants: The case of carbon storage

Carbon storage comprises four technology variants defined by the nature of the storage reservoir - (onshore or offshore) depleted oil & gas reservoirs and (onshore or offshore) saline aquifers - and each variant has a different learning rate reflecting its different cost structure. Moreover, the proportional contribution of each variant to total storage is likely to change with the growth of global storage capacity. The composite learning rate for carbon storage is estimated for scenarios in which the relative contributions change: a negative learning rate is determined in one scenario.