With water consumption increasing, populations growing, and climate change affecting natural freshwater sources, global water stress is of increasing concern. To meet the freshwater demand, methods of artificially producing clean water are being explored. Desalination is among the most mature of these freshwater production technologies, though it is often claimed that seawater desalination (centralized) and transportation of this water from the coast to inland locations is expensive. More recently, there is growing interest in atmospheric water harvesting (AWH) as a method of producing fresh water from ambient air. AWH is touted to be a cost-effective method of producing fresh water locally where water is needed (decentralized), and thus does not require water to be transported. However, few studies have attempted to quantify the energy costs associated with AWH, and a direct comparison with desalination has not been reported. In this work, we analyze an AWH based on active cooling (like a vapor compression air conditioner) that condenses water from air. We find that using these systems to harvest water from outdoor air is an order of magnitude more expensive than the combined costs of coastal seawater desalination and transportation of the clean water to inland locations. Instead, we show that an indoor cooling system based on AWH that cogenerates both water and building cooling is a more practical and cost-effective use case of this technology.

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