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Cogeneration. . Is the simultaneous production of electrical and thermal energy from a single fuel source . Typical Cogeneration Fuels . Natural Gas Coal Diesel oil Bio mass [e.g. methane, from digesters or municipal landfills] . Example. Example. Overall Thermodynamic Efficiency
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Cogeneration. Is the simultaneous production of electrical and thermal energy from a single fuel source
Typical Cogeneration Fuels • Natural Gas • Coal • Diesel oil • Bio mass [e.g. methane, from digesters or municipal landfills]
Example • Overall Thermodynamic Efficiency • Often called Utilization Factor • Conventional Efficiency Power Plant Boiler • Improvement
Fuel Savings if conventional System Output is 50 MW • Fuel cogen • Fuel conven • Fuel Savings
Economics • Plant operates 68% of time or 6000 hrs/year (conservative estimate). Fuel Savings If we use natural gas, $8/MMBtu, the monetary savings ~$7,000,000/year. • How much could you invest economically? • How much CO2 reductions per year?
Topping Cycle Bottoming Cycle Operating cycles
Gas Turbine Topping Cycle Installed at Rice University
Prime movers • Reciprocating engines • efficient • compact • easy to install • suitable for small applications • Gas Turbines • Intermediate power applications • Relatively compact • Reliable • Easy to install • “combined cycles”, but only for large industrial applications
Prime Movers (cont.) • Steam Turbines • Good efficiency only for units larger that 10mW • Can use a variety of fuels including solid waste and biomass • “extraction” turbines; a portion of the steam flow removed during the expansion process • “back pressure” entire steam flow used after last stage of expansion
Economic Criteria • Payback Period • Is the length of time required for the cumulative net savings to equal the initial installed capital cost. Divide the initial investment by the annual net savings. • Discounted Cash-Flow Method • Analyses the cash-flows over the full life of the project and accounts for the time value of money, including interest rate and rate of inflation.