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CO2 direct air capture (DAC) has been increasingly discussed as a climate change mitigation option. Despite technical advances in the past decade, there are still misconceptions about DAC's current and long-term costs as well as energy, water and area demands. This could undermine DAC's anticipated role in a neutral or negative greenhouse gas emission energy system, and influence policy makers. In this study, a literature review and techno-economic analyses of state-of-the-art DAC technologies are performed, wherein, DAC technologies are categorised as high temperature aqueous solutions (HT DAC) and low temperature solid sorbent (LT DAC) systems, from an energy system perspective. DAC capital expenditures, energy demands and costs have been estimated under two scenarios for DAC capacities and financial learning rates in the period 2020 to 2050. DAC system costs could be lowered significantly with commercialisation in the 2020s followed by massive implementation in the 2040s and 2050s, making them cost competitive with point source carbon capture and an affordable climate change mitigation solution. It is concluded that LT DAC systems are favourable due to lower heat supply costs and the possibility of using waste heat from other systems. CO2 capture costs of LT DAC systems powered by hybrid PV-Wind-battery systems for Moroccan conditions and based on a conservative scenario, without/with utilisation of free waste heat are calculated at 222/133, 105/60, 69/40 and 54/32 (sic)/t(CO2) in 2020, 2030, 2040 and 2050, respectively. These new findings could enhance DAC's role in a successful climate change mitigation strategy. (C) 2019 The Authors. Published by Elsevier Ltd.