My research is on inventing transformative manufacturing technologies with a vision for dry (water-less) and resource-efficient factories, and developing new computational models for design, analysis, and evaluation of manufacturing and energy systems of the future.  Specific areas of interest include (1) supercritical carbon dioxide-based technologies in manufacturing, thermal management, and waste treatment applications; (2) predictive modeling and process simulation for data-driven decision-making in manufacturing systems; (3) thermodynamic, life cycle, and systems analysis of industrial and biogeochemical carbon capture and sequestration pathways; (4) least-cost climate change mitigation technology forecasting and policy analysis in the energy and transportation sectors, and (5) regional water impacts of global energy transitions to near-zero greenhouse gas emissions.

Select research projects from my doctoral and postdoctoral work are briefly summarized below.


Supercritical Carbon Dioxide Based Metalworking Fluids

Metalworking fluids (MWFs) are essential coolants and lubricants that are ubiquitous in the metals manufacturing industry.  This research studied the applicability of supercritical CO2 MWFs relative to other water and gas-based MWFs used in a wide variety of manufacturing processes and engineering materials in industrial practice.  In its supercritical state, CO2 possesses excellent solubility (and solubility control) for low and medium-carbon compounds such as vegetable oils.  Supercritical CO2 MWF is essentially a solution of CO2 compressed to about 14 MPa and 42 °C with small quantities of dissolved oil that is rapidly expanded through a nozzle.  The resulting spray particles contain chilled oil particles and dry ice, which provide a high degree of lubricity and cooling to the interface between the cutting tool and metal being machined.

Specific contributions include analysis of tool wear, machining forces, and thermal data collected from a large set of machining experiments at industrial conditions, and data synthesis to determine operating conditions and underlying mechanisms whereby supercritical CO2 MWFs provide better productivity than water and oil-based MWFs. The research also investigated the effectiveness of supercritical CO2 MWFs as an enabler for environmentally benign mechanical micro-machining processes to replace chemical fabrication processes without performance trade-offs.  Cutting forces and surface characteristics of Cu-101 and AISI-304 were measured and analyzed in a partial factorial experiment set.  Results showed improved micro-machinability, warranting further exploration of underlying mechanisms.

Read more about this research in these publications.

D. A. Stephenson, S. J. Skerlos, A. S. King, S. D. Supekar, J. Mater. Process. Technol. 214, 673–680 (2014).

S. D. Supekar, B. A. Gozen, B. Bediz, O. B. Ozdoganlar, S. J. Skerlos, J. Manuf. Sci. Eng. 135, 24501 (2013).

S. D. Supekar, A. F. Clarens, D. A. Stephenson, S. J. Skerlos, J. Mater. Process. Technol. 212, 2652–2658 (2012).



Industrial CO2 Recovery

CO2 as an industrial resource has a market of about 11 million metric tonnes annually in the U.S. with applications ranging from metals fabrication, food and beverage processing, and chemicals and pharmaceuticals manufacturing.  In this research, we studied the recovered CO2 supply chain, and estimated the environmental emissions and resource use associated with recovering CO2 from industrial sources such as fertilizer plants, ethanol distilleries, and refinery hydrogen plants.  This research developed a market-based allocation method in a consequential life cycle assessment framework, which can be applied to recovered CO2 as well as other industrial co-products, proposed a revised set of greenhouse gas accounting operational boundaries to incorporate reuse and sequestration as fates for CO2, and created emissions and resource use inventories for CO2 recovered from all major industrial sources based on a comprehensive understanding of the thermodynamics, process engineering, and environmental aspects of CO2 recovery.  

Our research showed that depending on the source and purity of CO2, 1 metric tonne of recovered CO2 leads to additional greenhouse gas emissions of 147 − 210 kg CO2 eq , while consuming 160 − 248 kWh of electricity, 254 − 480 MJ of heat, and 1836 − 4027 kg of water.  Applying these emissions and resource use numbers to scCO2 MWFs and scCO2-based wafer rinsing in semiconductor manufacturing, we find that the use of CO2 can actually reduce the carbon, water, and energy footprints of these manufacturing processes.  These results encourage further exploration of industrial technologies based on the use of CO2 and other industrial gases as working fluids can help eliminate the use of water in "dry" and energy-efficient factories.

Read more about this research in these publications.

S. D. Supekar, S. J. Skerlos, Environ. Sci. Technol. 48, 14615–14623 (2014).

S. D. Supekar, S. J. Skerlos, Procedia CIRP. 15, 461–466 (2014).



Carbon Capture from Power Plants

This research focused on understanding the mass and energy feedbacks inherent to carbon capture systems, and their effects on the thermodynamic, environmental, and economic performance of power plants retrofitted with carbon capture.  In the context of power plants equipped with carbon capture, this research has established an analytical relationship between the pre-capture and post-capture efficiency of a power plant and quantified the effects of potentially more stringent quality/purity requirements for CO2 sequestration on the thermal efficiency and costs of carbon capture using process and life cycle models similar to those used for CO2 capture from industrial sources.  The analysis showed that the thermal efficiency penalty (drop in overall plant efficiency after adding a carbon capture unit) for older and relatively inefficient coal power plants can be vastly higher than the efficiency penalty for newer and more efficient coal power plants by as much as 9 %-points (typical efficiency of coal power plants ranges from 32 – 40%).  This result holds significant implications for carbon capture and sequestration (CCS) in subcritical coal power plants which comprise the majority of the world's installed coal power fleet.

This research also formulated a set of analytical equations for the thermal efficiency, CO2 emissions, and economics sixteen major carbon capture retrofit configurations for coal and natural gas CCS plants involving steam cycle integration as well as auxiliary boiler or gas turbine-based combined heat and power plants for supplying capture energy (the analytical equations incorporate the critical mass and energy feedbacks involved).  These expressions can rapidly and accurately evaluate profit-maximizing CCS configurations for thousands of individual plants without the need for costly process simulation models.  The equations have been implemented in the latest release of the Argonne GREET model.

Read more about this research in these publications.

S. D. Supekar, S. J. Skerlos, Environ. Sci. Technol., 51, 12908–12917 (2017).

S. D. Supekar, S. J. Skerlos, Environ. Sci. Technol. 49, 12576–12584 (2015).



Least-Cost Greenhouse Gas Mitigation in the U.S. Electric and Auto Sectors (The LETSACT Model)

This research created the Least-cost Energy and Transportation Sectoral Analysis for Climate Targets (LETSACT) technology planning and policy evaluation model for assessing current strategies and developing new strategies for climate change mitigation and adaptation.  The model offers several functionalities of economic equilibrium models at a lower computational cost.  This research has identified cost-minimizing technology pathways to cut about 45 billion tonnes of CO2 from these sectors by 2050.  Further, the work has established that even with optimistic technological and cost advancements, the cost of meeting CO2 reduction targets increases sharply with every year of delay beyond 2020 in pursuing these targets.  This increasing cost is in addition to the social and environmental damage costs of climate change.  This research is the first to quantify the ramifications of the inertia of vehicles and power plant turnover rates in the U.S. on the private costs of CO2 abatement, and it underscores the urgency of introducing adequate policy measures to keep emissions on track with IPCC targets. 

My ongoing research in this area combines the LETSACT model with carbon capture technology models to understand the costs and regional land and water use implications of negative emission technologies such as ambient CO2 capture and bioenergy with CCS in society’s transition to zero- and negative-carbon energy systems.  Current focus is on direct air capture (DAC) technology, which sucks CO2 from the atmosphere for long-term storage or sequestration.  We are particularly interested finding if, when, and to what extent can large-scale deployment of DAC plants help the U.S. stay within its carbon budget, and how such large-scale DAC deployment would impact the electricity demand and composition (coal, natural gas, renewables etc.) of the electric fleet.

Find out more about this research in these publications.

S. D. Supekar, S. J. Skerlos, Environ. Sci. Technol. 51, 10932–10942 (2017).

S. D. Supekar, K. A. Caruso, M. S. Daskin, S. J. Skerlos, Re-engineering Manufacturing for Sustainability, A. Y. C. Nee, B. Song, S.-K. Ong, Eds. (Springer, Singapore, 2013).