اندازه گیری گازهای گلخانه ای و تجزیه و تحلیل اقتصادی از گاز طبیعی ایران از استخراج نیروگاه های برق

This study attempts to examine the natural gas fired power plants in Iran. The required data from natural gas fired power plants were gathered during 2008. The characteristics of thirty two gas turbine power plants and twenty steam power plants have been measured. Their emission factor values were then compared with the standards of Energy Protection Agency, Euro Union and World Bank. Emission factors of gas turbine and steam power plants show that gas turbine power plants have a better performance than steam power plants. For economic analysis, fuel consumption and environmental damages caused by the emitted pollutants are considered as cost functions; and electricity sales revenue are taken as benefit functions. All of these functions have been obtained according to the capacity factor. Total revenue functions show that gas turbine and steam power plants are economically efficient at 98.15% and 90.89% of capacity factor, respectively; this indicates that long operating years of power plants leads to reduction of optimum capacity factor. The stated method could be implemented to assess the economic status of a country’s power plants where as efficient capacity factor close to one means that power plant works in much better condition

Nowadays, climate changes and people’s health problems are known as the most serious environmental issues and one of the main sources of climate change is fossil fuel power plants. Reasonable estimation of greenhouse gas emissions is essential for developing an appropriate policy to better address the global warming and people’s health problem. Fossil fuel power plants are great consumers of fossil fuel resources and are among greatest industrial emission producers. Emissions from power plants pose a potentially large risk to human health and the environment (Lopez et al., 2005). Therefore, any attempt for optimizing power plant operation and the renovation of its facilities, including economic and environmental attitudes, will gain huge benefits in the long time. Further, socio-economic and environmental factors should be evaluated together in the selection of area for creating new thermal power plants (Say, 2006). Therefore, it could be concluded that power plant emissions such as CO2 could be reduced with optimizing power plant operation and renovation of its facilities. Amount of CO2 not only damages the environment and causes financial losses, but also damages ozone layer. The energy sector accounts for approximately 90% of the CO2 emissions and 75% of the total greenhouse gas emissions in developed nations (Intergovernmental Panel on Climate Change IPCC, 2006). Capturing CO2 from exhaust gas at thermal power generation systems (PGSs) is considered as an effective means of dramatically reducing CO2 emissions into the atmosphere. Technologies of capturing CO2 include pre-combustion, post combustion and oxy-combustion methods (Davison, 2007 and Kanniche et al., 2010). The impact of capturing CO2 from fossil fuel power plants on the emissions of NOx and SOx is favorable. Although, due to the reduced efficiency of power plants equipped with capturing technologies, the large-scale implementation of capturing carbon increases the emission levels of NOx from the power sector, but some NOx and SOx can be removed during the CO2 capture (Tzimas et al., 2007). Using the CO2 capture repowering system, the unit cost of power is about 18.0% cheaper and the annual profit 6.68 times larger than that of the reference system. However, the depreciation year of the proposed system is estimated to be longer than that of the reference system (Pak et al., 2010). The most efficient load of a newly established power plant is its nameplate capacity. As time elapses, efficiency and the load up on which the power plant has the highest efficiency reduces; therefore it proves most efficient if power plants work on the efficient load (and not the nameplate capacity factor). This study aims to find the ratio of efficient load to the nominal capacity. If power plants work on the efficient load which is addressed here, it will yield the most economic benefit. Prior to this study, authors have investigated CO2, CO, SO2 and NOx emission factors of Iran’s fossil fuel fired power plants and have concluded that these power plants do not work on an efficient load (Alavije et al., 2010). This research evaluates the amount of Iran’s natural gas fired power plant emissions during 2008. The study is based on thirty two gas turbine and twenty steam power plants for estimation of CO2 and NOx emission factors. The nameplate capacity of the power plants ranges from 60 MW to 315 MW for steam power plants and 15–165 MW for gas turbine power plants. The total nominal and produced capacities of Iran’s governmental power plants are about 46 GW and 42 GW, respectively. The overall nominal capacity of the gas turbine and steam power plants are 11,798.7 MW and 14,935 MW, respectively. The overall electricity produced in gas turbine and steam power plants are 9807 MW and 14,565.6 MW, respectively. Therefore, it can be concluded that total capacity factor of gas turbine and steam power plants are 83.1% and 97.5%, respectively. Natural gas consumption is 16,000–72,000 m3/h for steam power plants and 4900–45,418 m3/h for gas turbine power plants (Environment Protection Department of Niroo Research Institute (NRI), 2008). Further, the developed emission factors are compared with those for other group works. An economic analysis is preformed which prefers the optimum power plant operation based on parameters such as fuel consumption cost, generating electricity revenue, emission cost, power plant load etc. In addition, the EF1 values of natural gas fired power plants are compared with the standards of EPA2, EU3 and World Bank.

The characteristics of thirty two gas turbine power plants and twenty steam power plants were measured and discussed in this paper. It was shown that CO2 EF is higher than EPA standard in steam power plants. Further, the NOx EF was also proved to be higher than EPA, WB and EU standards in steam power plants. Nevertheless, the CO2 and NOx EFs were lower than standards in gas turbine power plants. The steam power plants can be improved by increasing power plants efficiency and renovation of their facilities. Moreover revising power plant systems is necessary and should be carried out in all steam power plants in order to decrease EF in power industries. The economic approach indicated that the environmental cost of CO2 is significantly more than that of NOx in both steam and gas turbine power plants. Thus, it is economically recommended to invest in the CO2 reduction instead of investing in the NOx reduction. The capture methods for the CO2 such as control instruments in gas turbine and steam power plants can be used to reduce the CO2 EF. Due to long years of power plants’ operation in Iran, maximum economic profit of gas turbine power plants and steam power plants happens in capacity factors slightly lower than 100%. The economically efficient state of GPPs and SPPs are in 98.15% and 90.89% capacity factor. The capacity factor of gas turbine power plants makes the maximum economic profit slightly more than that for steam power plants. Hence, Iran gas turbine power plants are more efficient than steam power plants. Furthermore, this study indicates fewer amounts of emission factors for GPPs, high amounts of total revenue per kW h for GPPs and more capacity factors in economically efficient state of GPPs in comparison with SPPs. All obtained results are in good agreement and verify each other. The stated method could be implemented to assess the economic status of a country’s power plants where as efficient capacity factor close to one, means they work in much better condition. Difference between efficient capacity factors indicates that studied power plants do not work well for various reasons such as old equipment and need to have improvement.