Hydrogen production from polymeric organic solids via atmospheric pressure nonthermal Plasma

The potential of using hydrogen as a sustainable energy carrier is attributed to its high energy density and its utilization without CO$_2$ emissions. Existing technologies mainly produce hydrogen thermochemically via natural gas reforming or electrochemically through water splitting. Organic solid feedstocks rich in hydrogen, such as biomass and plastic waste, are under-utilized for this purpose. Approaches based on low-temperature atmospheric pressure plasma powered by renewable electricity could lead to the production of green hydrogen more viably than current approaches, leading to sustainable alternatives for upcycling plastic and biomass waste. This doctoral research dissertation focuses on the production of hydrogen from solids via atmospheric nonthermal plasma. First, two low-temperature atmospheric pressure plasma reactors, based on transferred arc (transarc) and gliding arc (glidarc) discharges and depicting complementary operational characteristics, are designed, built, and characterized to produce hydrogen from low-density polyethylene (LDPE) as a model plastic waste. Experimental results show that hydrogen production rate and efficiency increase monotonically with increasing voltage level in both reactors. Despite the reactors' markedly different modes of operation, their hydrogen production performance metrics are comparable.Comment: arXiv admin note: substantial text overlap with arXiv:2210.1136

Thermal Performance of Selected Oils in Uganda for Indirect Solar Domestic Cooking Applications

This study experimentally evaluated the thermal performance of selected oils in Uganda for indirect solar domestic cooking applications. The oil samples used were refined sunflower oil, refined palm oil and thermia B. These oils are locally available in Uganda. Thermal stratification, energy and exergy analysis were performed for each oil to determine their suitability for Thermal Energy Storage (TES) using a thermosiphon principle. The results showed that thermal stratification of refined sunflower oil was higher as compared to refined palm oil and thermia B during the first one hour. The stored energy and exergy for refined sunflower oil was generally higher than that of refined palm oil and thermia B. The thermal performance of refined sunflower oil was comparable to that of refined palm oil which was better than that of thermia B.Keywords: Thermosiphon; thermal stratification; energy; exergy; oi

Nonthermal Atmospheric Plasma Reactors for Hydrogen Production from Low-Density Polyethylene

Hydrogen is largely produced via natural gas reforming or electrochemical water-splitting, leaving organic solid feedstocks under-utilized. Plasma technology powered by renewable electricity can lead to the sustainable upcycling of plastic waste and production of green hydrogen. In this work, low-temperature atmospheric pressure plasma reactors based on transferred arc (transarc) and gliding arc (glidarc) discharges are designed, built, and characterized to produce hydrogen from low-density polyethylene (LDPE) as a model plastic waste. Experimental results show that hydrogen production rate and efficiency increase monotonically with increasing voltage level in both reactors, with the maximum hydrogen production of 0.33 and 0.42 mmol/g LDPE for transarc and glidarc reactors, respectively. For the transarc reactor, smaller electrode-feedstock spacing favors greater hydrogen production, whereas, for the glidarc reactor, greater hydrogen production is obtained at intermediate flow rates. The hydrogen production from LDPE is comparable despite the markedly different modes of operation between the two reactors

Hydrogen from Cellulose and Low-density Polyethylene via Atmospheric Pressure Nonthermal Plasma

The valorization of waste, by creating economic value while limiting environmental impact, can have an essential role in sustainable development. Particularly, polymeric waste such as biomass and plastics can be used for the production of green hydrogen as a carbon-free energy carrier through the use of nonthermal plasma powered by renewable, potentially surplus, electricity. In this study, a Streamer Dielectric-Barrier Discharge (SDBD) reactor is designed and built to extract hydrogen and carbon co-products from cellulose and low-density polyethylene (LDPE) as model feedstocks of biomass and plastic waste, respectively. Spectroscopic and electrical diagnostics, together with modeling, are used to estimate representative plasma properties, namely electron and excitation temperatures, number density, and power consumption. Cellulose and LDPE are plasma-treated for different treatment times to characterize the evolution of the hydrogen production process. Gas products are analyzed using gas chromatography to determine the mean hydrogen production rate, production efficiency, hydrogen yield, selectivity, and energy cost. The results show that the maximum hydrogen production efficiency for cellulose is 0.8 mol/kWh, which is approximately double that for LDPE. Furthermore, the energy cost of hydrogen production from cellulose is 600 kWh/kg of H2, half that of LDPE. Solid products are examined via scanning electron microscopy, revealing the distinct morphological structure of the two feedstocks treated, as well as by elemental composition analysis. The results demonstrate that SDBD plasma is effective at producing hydrogen from cellulose and LDPE at near atmospheric pressure and relatively low-temperature conditions in rapid-response and compact processes