Tarea No. 06 IILI03058 FUENTES NO CONVENCIONALES DE ENERGÍA Ago-Dic 2023 1. Consider an average PC plant with a heat rate of 10,340 Btu/kWh burning a typical U.S. coal with a carbon content of 24.5 kgC/GJ (1 GJ = 1 × 109 J). About 15% of thermal losses are up the stack and the remaining 85% are taken away by cooling water. i Find the efficiency of the plant. ii Find the rate of carbon and CO2 emissions from the plant in kg/kWh. iii If CO2 emissions eventually are taxed at $10 per metric ton (1 metric ton =1000 kg), what would be the additional cost of electricity from this coal plant (¢/kWh)? (CO2 has a molecular weight of 12 + 2 × 16 = 44) 2. A combined-cycle, natural gas (consider it as methane CH4 ), power plant has an efficiency of 52%. Natural gas has an energy density of 55,340 kJ/kg and about 77% of the fuel is carbon. i What is the heat rate of this plant expressed as kJ/kWh and Btu/kWh? ii Find the emission rate of carbon (kg C/kWh) and carbon dioxide (kgCO2 /kWh). Compare those with the average coal plant emission rates found in the previous problem. 3. In a reasonable location, a photovoltaic array will deliver about 1500 kWh/yr per kW of rated power. i What would its CF be? ii One estimate of the maximum potential for rooftop photovoltaics (PVs) in the United States suggests as much as 1000 GW of PVs could be installed. How many metric tons of CO2 emissions would be avoided per year? 4. For the following power plants, calculate the added cost (¢/kWh) that a $50 tax per metric ton of CO2 would impose. Use carbon content of fuels from Table 1. i ii iii iv v Old coal plant with heat rate 10,500 Btu/kWh. New coal plant with heat rate 8,500 Btu/kWh. New IGCC coal plant with heat rate 9,000 Btu/kWh. NGCC plant with heat rate 7,000 Btu/kWh. Gas turbine with heat rate 9,500 Btu/kWh. Table 1. Assumptions for calculating carbon emissions. Efficiency is based on HHV of fuels. Technology New Coal Old Coal GT NGCC Heat Rate (Btu/kWh) 8,750 10,340 9,300 6,900 Efficiency (%) 39.0 33.0 36.7 49.4 Fuel (kg C / GJ) 24.5 24.5 13.7 13.7 Emissions (kg C / kWh) 0.23 0.27 0.13 0.10 Emissions (kg CO2 / kWh) 0.83 0.98 0.49 0.37 5. An average pulverized coal power plant has an efficiency of about 33%. Suppose a new ultra-supercritical coal (USC) plant increases that to 42%. Assume coal burning emits 24.5 kg C/GJ. i If CO2 emissions are eventually taxed at $50 per metric ton, what would the tax savings be for the USC plant ($/kWh)? ii If coal that delivers 24 million kJ of heat per metric ton costs $40/t what would be the fuel savings for the USC plant ($/kWh)? 1
