(Dr. Samuel Shelton, advisor)

"Micro-Cogeneration Optimal Design for Service Hot Water Thermal Loads"

Abstract

Decentralization of electric power generation is being encouraged by the initiation of electric utility deregulation combined with the availability of efficient small gas turbine generators. These decentralized power generation systems make possible the use of the waste heat normally rejected at central power plants. Economic justification of these cogeneration systems generally require a high thermal load factor, high utility electric costs, and relatively low gas costs.  These factors appear to be favorable in athletic club facilities with a high and nearly constant hot water demand for showers.  Field data was obtained for such a facility using about 20,000 gallons of hot water per day. A cogeneration system was then designed using recently introduced gas turbine equipment. The cogenerator size was economically optimized using the statistical profile of the thermal load data.

The economic and environmental impacts of the resulting micro-cogeneration energy system consisting of an 84 kW-turbine generator were then analyzed. The simple pay back period in this particular case was found to be 6.8 years. After the pay back period, it was found that the facility would continue to save $20,800 per year throughout the life of the cogeneration system. The extra natural gas consumed by the turbine generators over the current gas-fired water heater results in a slight increase in on-site carbon emissions. The reduction in electricity provided by the central power plant results in a decrease of carbon emissions at the central power plant, which exceeds the increase at the club site. Comparing the current system with the cogeneration system, the micro-cogeneration energy system reduces total carbon emissions by 46.7 tons of carbon per year. For a system life of 20 years, this results in an profit of $146.51 per ton of reduced carbon emissions. Studies have claimed that reducing carbon emissions costs $100-200 per ton of carbon. These studies ignore new technologies that are now available.