Marc J. L. Caballes

Compared with the waste-to-heat and electricity-based hybrid refrigeration system, the innovative lab-scale refrigeration system integrated with the DC and AC cooling units that able to use solar and electricity as energy resources. Previous studies found that temperature control and uniform temperature distribution in refrigeration systems are both critical factors reducing vibrio growth on raw oysters and saving energy consumption. Therefore, this refrigeration system also equipped a specially designed divider and was used to test various air circulation strategies to achieve uniform temperature distribution in six individual compartments. The objective is to investigate and evaluate the effects of air circulation strategies and operating conditions on the cooling performance, including temperature distribution, standard deviation of compartment temperatures, and cooling time using a factorial design method. Results indicated the maximum temperature difference between the compartments was 8.9 ± 2.0 °C, 6.7 ± 2.0 °C, and 4.8 ± 2.0 °C in the scenarios of no air circulation, natural air circulation, and combined natural and forced air circulation, respectively. The interaction of fan location and fan direction showed a significant effect on the compartment temperatures while there was no significant effect on cooling time. A circulation fan on the lower part of the 12-volt section with an air supply from the 12- to 110-volt section was determined as the optimal condition to achieve relatively uniform temperature distribution. Refrigeration system also achieved a cooling temperature of 7.2 °C within 150 min to meet regulations. To that end, the innovative hybrid oyster refrigeration system will benefit oyster industries, as well as the aquaculture farmers in terms of complying with regulations and energy savings.

Electricity generation and emission characteristics during the poultry litter and natural gas co-combustion process has rarely been studied. In this study, a Stirling engine was successfully integrated into the existing lab-scale swirling fluidized bed combustion system in order to further investigate the poultry litter and natural gas co-combustion process. Electricity, gaseous emissions, particulate matter (PM), and fly ash composition were analyzed under various operating conditions. Results indicated that the electricity reached 905 W under a water flow rate of 13.1 L/min and an engine head temperature of 584 °C. It was found that excess air (EA) ratios between 0.79 and 1.08 can relatively produce more electricity with lower emissions. At a secondary air (SA) height of 850 mm, secondary air/total air (SA/TA) ratios between 0.22 and 0.44 may significantly reduce NO_x and CO emissions. By increasing the mixing ratio (MR), SO₂ was reduced while NO_x increased at the beginning of co-combustion process but then decreased again. Additionally, PM results were lower than Maryland emissions standards. The fly ash results showed a higher nutrient content (close to 16%). This study shows the possibility of using poultry litter as a sustainable energy source for energy production while emitting lower emissions in the small decentralized combustion system.