DARPA Atmospheric Water Extraction (AWE): Revolutionizing Water Supply for the Warfighter

The supply of potable water to warfighters in the field is not just a logistical challenge—it’s a critical factor that impacts mission success, safety, and operational flexibility. Historically, the transport of water has incurred significant economic costs, tactical limitations, and, tragically, avoidable casualties. For instance, during Operations Enduring Freedom (OEF) and Iraqi Freedom (OIF), 10-12% of U.S. Marine Corps casualties were attributed to the logistics of moving water and fuel. Recognizing the vital role of water in military operations, DARPA has launched the Atmospheric Water Extraction (AWE) program with a vision to liberate warfighters from the water supply chain and reduce the associated logistical burden.

Program Vision: Harnessing Airborne Moisture for Potable Water

The AWE program is centered around supporting small businesses in developing first-of-its-kind water-from-air systems that utilize novel sorbent-based approaches. These innovative systems aim to efficiently extract water from the atmosphere, even in the most challenging environments where traditional methods fail. Unlike conventional compression/condenser devices that struggle in cold or dry conditions and have reached their practical efficiency limits, sorbent-based devices have the potential to operate effectively across a wider range of environments, ensuring the availability of potable water regardless of the operational theater.

Sorbent-based devices are systems that utilize materials known as sorbents to capture and hold water vapor from the air, which can then be extracted and converted into liquid water. These devices work by leveraging the properties of sorbent materials, which have a high affinity for water molecules. Sorbents can be either absorbents, which take in water into their structure, or adsorbents, which capture water on their surface. The choice of material depends on the specific application and environmental conditions.

In the context of atmospheric water extraction, sorbent-based devices are designed to operate in a wide range of environmental conditions, including those where traditional methods like condensation may not be effective. For example, in extremely dry or cold climates where there is minimal moisture in the air, sorbent materials can still capture water vapor due to their strong attraction to water molecules.

Once the water vapor is captured, it needs to be released from the sorbent to be collected as liquid water. Traditional sorbent systems often use heat to release the water, a process that involves evaporating the captured moisture and then condensing it back into a liquid form. However, this method can be energy-intensive because it relies on the latent heat of vaporization, which is the energy required to turn water from a liquid to a gas and back again.

To improve efficiency, new approaches are being developed that aim to release the water from the sorbent without relying solely on heat, potentially using other methods like pressure changes, chemical reactions, or advanced materials that release water at lower energy costs. These innovations could make sorbent-based water extraction systems more practical and efficient for a variety of uses, including military, humanitarian, and disaster relief operations where access to potable water is critical.

How Does AWE+ Work?

At the heart of DARPA’s AWE+ program lies the development of revolutionary sorbent materials. These materials are engineered to possess an extraordinary affinity for water vapor, efficiently capturing it from the surrounding air. Imagine these sorbents as highly porous sponges, eagerly soaking up moisture from the atmosphere.

Once water vapor is trapped within the sorbent, the next critical challenge arises: extracting the captured water in a manner that is both efficient and energy-conserving. DARPA is investigating several promising techniques to achieve this:

Photoswitching

This approach harnesses the power of light to trigger the release of water from the sorbent. By exposing the material to specific wavelengths of light, researchers aim to induce a change in the sorbent’s structure, causing it to expel the absorbed water. This method holds the potential for creating self-sustaining systems that rely solely on solar energy for both water capture and extraction.

Compressive Release

This method involves applying pressure to the sorbent to force out the captured water. By squeezing the material, researchers can physically expel the moisture. While this technique is relatively straightforward, optimizing the pressure required to achieve efficient water extraction without damaging the sorbent is a key challenge.

Multi-Stage Liquid Desiccant Distillation

A more complex approach, multi-stage liquid desiccant distillation, employs a series of liquid desiccants to progressively remove water from the air. Each stage in the process involves a different desiccant with varying water absorption capacities. This method offers the potential for high water recovery rates but requires careful engineering to balance efficiency and energy consumption.

The ultimate goal of these research efforts is to develop AWE+ systems that can operate effectively across a wide spectrum of environmental conditions. From arid deserts to humid rainforests, these devices should be capable of extracting potable water reliably and efficiently. By overcoming the challenges associated with sorbent materials and water extraction, DARPA seeks to create a technology that can revolutionize water acquisition and provide a sustainable solution to global water scarcity.

DoD Relevance: Meeting Warfighter and Humanitarian Needs

Each warfighter requires approximately 8 liters of water daily, and the current methods of supplying this essential resource impose severe tactical limitations. The reliance on water resupply hampers maneuverability, limits decision-making space, and complicates the logistics of emerging operational concepts like Expeditionary Advanced Base Operations (EABO) and Multi-Domain Operations (MDO).

DoD operations occur globally, spanning various climates, from cold and arid regions to humid tropical environments. Traditional water extraction technologies, such as compression and condenser-type devices, are often ineffective in extreme conditions, particularly in cold or dry environments where moisture levels are low. These technologies have also reached their practical limits in terms of efficiency. Consequently, there is a pressing need for sorbent devices that can overcome these limitations and provide reliable water extraction capabilities across all domains of operation, ensuring tactical flexibility for military forces.

Moreover, the ability to generate potable water on-site is not only crucial for military operations but also for humanitarian and disaster relief missions, where access to clean water is often a matter of life and death.

Technical Challenges and Requirements

To achieve its goals, the AWE program focuses on the development of sorbent devices capable of efficient water release and potability. Traditional sorbent devices use heat to release water, a process bound by the latent heat of vaporization with limited efficiency. DARPA is seeking innovative approaches that bypass these limitations, aiming for a more energy-efficient extraction process that minimizes the need for purification. The water produced must be potable or easily made potable, and the program emphasizes the stability of the devices to ensure they do not degrade over time by leaching materials into the water.

A key technical requirement is the energy budget for these devices, which is set at 100Wh of thermal energy and 100Wh of electrical energy per kilogram of water produced. This strict energy budget necessitates the development of highly efficient systems that can operate across various environments, from humid tropics to arid deserts, without compromising performance.

Furthermore, the water produced by these devices must be potable or easily made potable. If the extracted water requires additional purification, only the post-purified quantities will count towards DARPA’s performance metrics, and the energy costs associated with purification must be included in the size, weight, and power (SWaP) estimates. This ensures that the overall efficiency of the system is accurately assessed. Additionally, the stability of the sorbent materials is crucial, as any degradation over time—such as the leaching of materials into the water—could compromise the device’s performance and longevity. Ensuring the stability and purity of the water produced is therefore a key requirement for the success of these innovative water-from-air technologies in military applications.

Towards Field Deployment: Transitioning to Advanced Prototypes

The AWE program aims to bring these innovative water-from-air systems to a Technology Readiness Level (TRL) of 3-4 by the end of the program. Successful technologies will then require partnerships for further development and fielding by the Department of Defense (DoD). Planning for this transition is crucial from the onset, ensuring that the groundbreaking technologies developed under the AWE program can be scaled up and deployed to meet the needs of warfighters and humanitarian missions globally.

In summary, DARPA’s Atmospheric Water Extraction program represents a critical step towards ensuring that the U.S. military can operate with greater independence from traditional supply chains. By developing advanced, scalable technologies that can extract potable water from the atmosphere, the AWE program is poised to significantly enhance warfighter readiness, reduce logistical burdens, and support a wide range of humanitarian efforts.