My time at Oak Ridge National Laboratory

I have had the opportunity to visit Oak Ridge National Laboratory's main campus several times. Every time I visit the lab, I am so inspired by the incredible innovations I see, and no matter how old I get, it never gets any less awesome to visit Tennessee's own nerd paradise. During past visits, I have toured the experiment hall at the Spallation Neutron Source, stood in the viewing area overlooking the core of the High-flux Isotope Reactor--which supplies the United States with medical isotopes for use in devices such as X-ray machines--toured the genetic modification greenhouse, and, of course, toured the Building Technologies Research and Integration Center (BTRIC) twice. I have also had the opportunity to tour the Manufacturing and Design Facility (MDF) and see the future of advanced additive and subtractive manufacturing and tour the National Transportation Research Center to see work on fuel efficiency, alternative fuels, and future mobility. As a self-proclaimed infrastructure nerd, the Building Technologies Research and Integration Center was always my greatest fascination at the lab, and I was recently lucky enough to have a forty-hour job shadowing experience at the BTRIC.

 

I spoke with Dr. Junjie Luo about his team's work on testing low GWP refrigerants and improving the efficiency of refrigeration. Refrigeration is a surprisingly large contributor to global anthropogenic emissions. The dominant refrigerants that run our heating and cooling mechanisms today are Hydrofluorocarbons (HFCs). In the not-so-distant past, they replaced Chlorofluorocarbons (CFCs) in an effort to combat stratospheric ozone depletion. However, HFCs come with incredibly high GWPs, making them by far the most potent greenhouse gasses humans are responsible for. When these refrigerants leak out of systems, they build up in the atmosphere, worsening the greenhouse effect and subsequent climate change. To combat this issue, ORNL's Building Technologies Research and Integration Center is testing refrigerants with GWPs less than one and hardware to optimize their use. Dr. Luo showed me several of the team's experimental setups and walked me through what their research aimed to achieve. We even had the chance to speak some Chinese!

 

I stood alongside Dr. Cheng Ming as he configured a test loop that would be used to assess the performance of new heat exchanger designs. The loop used R-124a as a refrigerant. The performance of a heat exchanger was measured by placing it between hot and cold subloops. As the refrigerant was circulated, delta T values and pressures were logged for both loops in one second intervals. Before the setup could be used for experimentation, a PID controller needed to be calibrated, and the appropriate LabVIEW plots needed to be configured. The need for the setup is simple: in order to use many of the new refrigerants Dr. Luo's team was experimenting with, we also need new heat exchangers, primarily because many of these new coolants are highly flammable.

 

Dr. Rui Zhang showed me her teams projects, which are using refraction to detect building envelope air leaks with a smartphone camera and see moisture content inside of walls using microwaves. Lack of the ability to precisely pinpoint air leaks in building envelopes has plagued energy efficiency for centuries. During the last century, we developed thermal cameras, which allow us to get a general idea of where leaks reside. However, even thermal cameras are not overly precise when it comes to pinpointing the exact location of minuscule apertures. Dr. Rui Zhang showed me her team's work on using light refraction to visualize air flow through even the smallest of penetrations. They have accomplished this by using a camera to record video of a potential leak site and applying an algorithm to analyze the live differences in refraction throughout different parts of the image. The challenge is in refining this algorithm to function even in the absence of a textured wall and improving its ability to cut through noise. Their goal was to eventually create a smartphone app that would use the phone’s onboard camera to bring this powerful tool into the hands of consumers and professionals. Dr. Zhang’s team is also tackling a more physically invasive problem: wall interior moisture detection. To this day, if you want to know the moisture content of various materials inside the wall so that you can evaluate it for rot, mold, etc., your only option is to tear a hole in it, likely in several separate locations. It goes without saying that this approach is impractical, as it requires time and effort intensive repair after the analysis has been completed. Plus, there are plenty of contexts where it is considered inappropriate to punch a hole in the wall, like in a rental unit that you do not own. Dr. Zhang’s team is also employing refraction to develop a less invasive way to evaluate moisture inside of walls. They have designed a device to emit microwaves toward the wall, then measure them on return using a photoresistor. Since the construction material being evaluated is a preset constant such as MDF, fiberglass, or a certain type of wood, differences in refraction are attributable to moisture content. As with their other project, this approach is not without its challenges. Other materials in close proximity to the one you are trying to measure interfere with the results, making it impossible to distinguish moisture om the material you are trying to study. Like with the air leak project, the optimization they are working on now is in finding a way to overcome this mechanical “noise.” I always say I know I have seen a great idea when I think to myself: "why has no one thought of this before?" That is certainly how I feel about Dr. Zhang's work.

 

Dr. Mengjia Tang showed me her work on hygrothermal characterization of several new building materials. As climate change and its associated impacts as well as resource dependency become an increasingly large challenge for not just infrastructure, but humanity as a whole, there is a need for more sustainable construction materials. Dr. Mengjia Tang is working on hygrothermal characterization of some of these new materials and evaluating standard issue lumber for the purpose of comparison. She showed me her experiments, which are examining moisture absorption of various materials through time. She is using three different solutions to regulate the relative humidity within her sample jars, testing each material in all three environments. Water is the solvent in all three cases, but the solutes are sodium chloride (NaCl), magnesium chloride (MgCl2), and potassium hydrate (KHO), which keep RH at approximately 33%, 50%, and 95% respectively. To clarify, this effect is modeled by Raoult’s Law (P_A = X_AP_A∗) where P_A is the vapor pressure of solvent above the solution, X_A is the mole fraction of the solution, and P_A∗ is the vapor pressure of pure solvent. Each jar is given a label to identify it, and Dr. Tang masses each one every day. She can't open the jars as that would compromise the formulated environments, so she subtracts the predetermined mass of each individual jar from her reading in a spreadsheet. Then, the change in mass models how much moisture the material has absorbed. When the percent change between a reading and the previous reading is less than 0.1%, the sample is considered as having reached full saturation and terminated.

 

Dr. Nolan Hayes showed me the software package he is developing to make instillation of overlay panels for building retrofits easier, more efficient, and cheaper than ever before. The idea is to have a user interface on a computer that can tell you where to place components, then evaluate how far out of true it is and adapt other measurements to correspond for future components. The system works by communicating with a theodolite over Bluetooth. It uses a JSON protocol to send and receive data and instructions. We spent a couple of hours writing code and testing the model on a test wall the team had built up. We did tests such as moving a bracket 5 inches out of place and ensuring the algorithm could still find it and produce an error value that would allow it to adjust other measurements to compensate. Eventually, in the shorter term, this algorithm will be packaged in a user interface that will assist crane operators in placing components without the need for any direction from the ground. That ability will dramatically improve the efficiency of building retrofits but also has the potential to make a huge difference in new construction. In the longer term, however, this software can be applied to enable full-scale automation. The team will eventually test it with a fully autonomous crane that attaches to the structure on a set of rails.

 

Dr. Hayes and I also visited the department's concrete lab, which is helping make progress toward eliminating the single largest contributor to anthropogenic greenhouse gas emissions. Another project at the BTRIC is testing spontaneous combustion and flame-retardant properties of various construction materials with the aim of improving infrastructure resiliency to wildfires.