Lab Notebook: Growing SunChill™

Author: Russell Muren

The summer of 2014 has been a time of growth for the SunChill™ team. We added our first Grad Student, Sean Ryan, and hired our first full time SunChill™ employee, Jack Darrah. Additionally, we started our formal work with the Fraunhofer membrane distillation team in Freiburg, Germany. Originally we envisioned Sean and Jack needing a longer adjustment period to get up to speed, but are fired up to see results pouring in fast.

The main thrust of the technical work over the past two months has been focused on the 3D printing. We started earlier this year using some available, but fairly low tolerance, printers on the CSU campus and quickly realized a higher quality option was necessary. So in June we purchased a newly released Makerbot Z18.

Although we have produced some really high quality parts on this machine since it arrived, its important to stress just how much work was required to get this machine to make a reliable part. 3D printing may be trending, but it is still very early days and Rebound is pushing this technology way up against its limits. Waterproof walls thinner than 1mm used to build unsupported, complicated geometries with features as small as 0.5cm proved difficult to produce. However, as with all learning curves, we slowly learned what print settings would produce reliable parts. Are we at the top of this curve? Ha, no. We are progressing, however, making increasingly optimized, thin-walled, waterproof parts.

Based on our past work with Fraunhofer, we knew that achieving the desired system performance would require us to remove the air from the membrane during the bring/water separation process. This deaeration step can easily double the membrane’s efficiency and separation power. Unfortunately, this boost comes at the price of a somewhat more complicated membrane module.

To get a leg up on this research, we put together a simple flow test to determine how long we could keep a membrane deaerated. This is important because we deaerate using solar power and don’t want the air we remove one day seeping back in overnight. Our hope was that the module would remain deaerated for at least 12 hours and, fortunately, it has stayed partially deaerated for more than 30 days. These positive results were recently validated by Fraunhofer, who has taken testing to the next level by pushing real modules to very high levels of deaeration. The German team has shown that, with full-sized modules, 24 hours of complete deaeration is possible while partial deaeration can be maintained for days. Very positive news considering separation is the most complicated process in the SunChill™ system.