LAUSR

The mitigation of climate change requires fast reductions in greenhouse gas emissions and calls for fundamental transitions of energy systems. In most places, the increased exploitation of variable renewable sources (wind and solar) forms the backbone of these transitions. To remain consistent with the Paris Agreement temperature goals, negative emission technologies will likely be needed to achieve net zero emissions in the second half of the century. In integrated assessment models, negative emissions are typically realized through land-based approaches. However, due to their coarse temporal and spatial resolution, such models might underestimate the potential of decentrally deployable and flexible technologies such as Direct Air Capture (DAC). Based on validated high-resolution power generation time series, we show that DAC can extract CO2 from the atmosphere and facilitate the integration of variable renewables at the same time. It is a promising flexibility provider as it can be ramped within minutes. Our results show that negative emissions of up to 500 Mt CO2/year in Europe may be achievable by using renewable excess energy only. Electricity systems with high shares of volatile renewables will induce excess generation events during which electricity is cheap thereby lowering the operational costs of DAC. If investment costs can be sufficiently reduced, this may render very energy intensive but highly flexible technologies such as DAC viable. Plain Language Summary There is a finite amount of greenhouse gases that humankind can emit into the atmosphere before the 1.5 and 2 ∘C climate targets are exceeded. This calls for emission reductions in all sectors of human activity, in particular in the energy sector. In many countries, energy transitions have already led to the expansion of variable renewable energy technologies that depend strongly on weather such as wind and solar. In addition to the expansion of renewable energy, scenarios that achieve the 1.5 or 2 ∘C target require negative carbon emissions later in the century to make up for insufficient emission reductions so far. In this study, we investigate the cobenefits of a negative emission technology called Direct Air Capture (DAC) and a high share of wind and solar energy. The advantage of DAC is that it can in principle be deployed decentrally and it can be switched on and off very quickly. It is thus possible to use DAC to smooth the variability of renewable power generation while achieving negative emissions. Our study focuses on the technical aspects of including DAC in the power system and does not provide a thorough assessment of the economic viability of DAC deployment.