Energy savings can come in many different forms. In my research group, we focus on materials engineering solutions to extend the solar module lifetime as a way of reducing the cost of solar electricity. We are also developing solar-rejection coating materials for radiative cooling, which can be used for buildings, transportation systems, clothing, and even space vehicles. These solutions represent our approach to use increased durability as well as conservation for cost savings.

One of the ways to reduce the cost of solar electricity to 3¢/kWh, thus reaching parity with fossil-fuel-based generation, is to reduce the degradation rate of solar modules and extend their lifetime well beyond 30 years. The extended module lifetime in turn can positively influence the financial model and the bankability of utility-scale PV projects. Today, the highest-risk-priority solar module degradation mechanism is what is known as hot spots, often induced by cell cracks. In order to address this degradation mechanism, we make use of low-cost, multi-walled carbon nanotubes embedded in commercial screen-printable silver pastes. When the carbon nanotubes are properly functionalized and appropriately incorporated into commercial silver pastes, the resulting metal contacts on solar cells, after screen-printing and firing, show exceptional fracture toughness. These composite metal contacts possess increased ductility, electrical gap-bridging capability up to 50 µm, and “self-healing” to regain electrical continuity after cycles of complete electrical failure. I will present our work ranging from materials engineering to module-level testing to demonstrate the utility of carbon-nanotube-reinforced metallization.

The idea of radiative cooling has been around since the 60s but recaptured people’s imagination in recent years. These coatings can achieve passive cooling, often below the ambient temperature, without having to expend an ounce of electricity. The asymmetry in heat transfer rate in summer vs. winter, combined with the low cost of natural gas, makes the radiative cooling economically attractive. In my group, we make use of low-cost, bulk-quantity, commercial ingredients (e.g., silica microspheres, paint binder, and silicone) to develop the coating material. Our technology eliminates the need for complex fabrications and expensive materials, such as silver. I will demonstrate that when the coatings consist of properly sized and randomly packed microspheres (also known as photonic glass) in a paint format, the temperature of the “painted” object can reach as much as 12 ºC below the ambient temperature and 5 ºC below the best performing commercial solar rejection paint under intense summer solar radiation.

Biography:

Dr. Han is a Regents Professor in the Departments of Chemical & Biological Engineering and Electrical & Computer Engineering at the University of New Mexico. He earned his Ph.D. in chemical engineering from the University of California at Santa Barbara and his B.S. in chemical engineering with honors from the University of California at Berkeley. Dr. Han has over 25 years of experience in electronic and photonic materials engineering and fabrication. His current research topics include (1) writable/rewritable quantum circuitry by stress patterning; (2) low-cost, crack-tolerant, advanced metallization for solar cell durability; (3) thin film processing and nanoscale surface corrugation for enhanced light trapping for photovoltaic devices; and (4) microsphere-based manufacturable coatings for radiative cooling. He has close to 70 publications in peer-reviewed journals and over 200 invited/contributed papers at academic institutions, national laboratories, and conferences. For his excellence in both research and teaching, Dr. Han received a Regents Professor title at UNM in 2015, a UNM Junior Faculty Research Excellence Award in 2005, and an NSF Career Award in 2001. He is also a recipient of STC.UNM Innovation Award consecutively from 2009 to 2020, and he was elected as the 2018 STC.UNM Innovation Fellow. Dr. Han holds 19 UNM-affiliated U.S. patents and 6 pending U.S. and PCT patent applications. He currently serves as the Chief Technology Officer of Osazda Energy LLC, a startup company based on his intellectual property generated at UNM. Prior to his entrepreneurial venture, Dr. Han served as the main campus faculty member of the STC.UNM Board of Directors from 2015 to 2016.

Contact:

Email: sang.m.han@osazda.com or meister@unm.edu