Getting water out of thin air – and relieving drought stress in trees
The environmental sciences can be a bit depressing at times. When you examine the facts, it is easy to be disheartened by the unfortunate state of our ecosystems, oceans, climate and, worst of all, the general public’s perception of these issues. We’ve created issues that we are only beginning to comprehend, let alone fix, and show no signs of easing up any time soon. Environmental work can seem futile, even absurd, and we’ve all questioned our own motives and choice of major. However, as anyone who has chosen to pursue an environmental career can inform you, these issues are just as much worthy as they are intimidating… and let me tell you, they’re pretty intimidating. So the question for every aspiring environmentalist then becomes, where do I start?
For me, the answer was SCU’s engineering quad, a once-mystical enclave I became aware of through its ice cream vending machine and damage done to my friends’ social lives. Hidden within the Bannan Citadel lies the Latimer Energy Lab, a space dedicated to hands-on research of renewable and sustainable energy generation and use and my employer for this past summer. A team consisting of myself and three mechanical engineers- Max Reese, Lalo Melendez and Andy Ly- were tasked with designing and building a device that would capture water suspended in the air (humidity) and use it for irrigation in remote locations. The U.S. Department of Agriculture estimates that twelve and a half million trees have died in the Sierra alone due to the current drought, with tree mortality rates increasing, in some cases doubling, from year to year. Keeping trees alive in such important areas as the Sierra is necessary not only for carbon sequestration and ecological reasons, but also aesthetics. Who would want to see Yosemite if there were no trees? Okay, honestly I think that would still be one of the most beautiful places on Earth, but I digress.
We made our first model using a Peltier cooler (it uses semiconductors to make one side of a ceramic square hot and the other side cold when an electrical current is added) and... it actually worked! Within a few minutes of running, the cold side of the Peltier chip was covered in condensation and within an hour it began to drip off. We were making water from air! Alchemy!
After a couple weeks of iterations, however, the realization that Peltier coolers are about 10% efficient began to sink in as we received only 1.3 mL of water per hour in our best iteration. Given that our target was a liter per day, some significant rethinking was needed. This is when we discovered desiccants, the chemicals in the bottom of the glass cases in Chem 13 lab. Within a couple more weeks we were using these hydrophilic salts, calcium chloride in our case, to gather water vapor from the air and then evaporate it back out using solar radiation and collect it in a makeshift solar still. On our final day of testing we were able to get about ⅓ of a liter using only the energy required by a 12 volt computer fan attached to a battery and a small solar panel. Given the low relative humidity here in sunny and dry California, we were very proud of our device’s efficiency, but we hope to improve it further throughout the coming year and work toward its implementation in the field.
As an environmental science student who stuck his hand in the engineering mystery box and felt around a bit, I still have relatively little idea what’s in that box (although this time the brains seemed more realistic than the spaghetti did at my fourth grade Halloween party) but I have gained appreciation for the kind of interdisciplinary collaboration it takes to turn an idea into a functional product. Given a significant investment of time, trust and mentorship on behalf of the engineering school, I was able to have a meaningful and productive internship despite not being an engineer. In a world that seems as if it’s filled with negatives, being able to make a tangible difference and solve a real-world problem gives me some optimism. And resumé value.