Experimental study on combustion of torrefied palm kernel shell (PKS) in oxy‐fuel environment

Oxy‐combustion of biomass can be a major candidate to achieve negative emission of CO₂ from a pulverized fuel (pf)‐firing power generation plants. Understanding combustion behavior of biomass fuels in oxy‐firing conditions is a key for design of oxy‐combustion retrofit of pulverized fuel power plant. This study aims to investigate a lab‐scale combustion behavior of torrefied palm kernel shell (PKS) in oxy‐combustion environments in comparison with the reference bituminous coal. A 20 kW_th‐scale, down‐firing furnace was used to conduct the experiments using both air (conventional) and O₂/CO₂ (30 vol% for O₂) as an oxidant. A bituminous coal (Sebuku coal) was also combusted in both air‐ and oxy‐firing condition with the same conditions of oxidizers and thermal heat inputs. Distributions of gas temperature, unburned carbon, and NO_x concentration were measured through sampling of gases and particles along axial directions. Moreover, the concentrations of SO_x and HCl were measured at the exit of the furnace. Experimental results showed that burnout rate was enhanced during oxy‐fuel combustion. The unburnt carbon in the flue gas was reduced considerably (~75%) during combustion of torrefied PKS in oxy‐fuel environment as compared with air‐firing condition. In addition, NO emission was reduced by 16.5% during combustion of PKS in oxy‐fuel environment as compared with air‐firing condition.     

Cost and performance of fossil fuel power plants with CO2 capture and storage

CO₂ capture and storage (CCS) is receiving considerable attention as a potential greenhouse gas (GHG) mitigation option for fossil fuel power plants. Cost and performance estimates for CCS are critical factors in energy and policy analysis. CCS cost studies necessarily employ a host of technical and economic assumptions that can dramatically affect results. Thus, particular studies often are of limited value to analysts, researchers, and industry personnel seeking results for alternative cases. In this paper, we use a generalized modeling tool to estimate and compare the emissions, efficiency, resource requirements and current costs of fossil fuel power plants with CCS on a systematic basis. This plant-level analysis explores a broader range of key assumptions than found in recent studies we reviewed for three major plant types: pulverized coal (PC) plants, natural gas combined cycle (NGCC) plants, and integrated gasification combined cycle (IGCC) systems using coal. In particular, we examine the effects of recent increases in capital costs and natural gas prices, as well as effects of differential plant utilization rates, IGCC financing and operating assumptions, variations in plant size, and differences in fuel quality, including bituminous, sub-bituminous and lignite coals. Our results show higher power plant and CCS costs than prior studies as a consequence of recent escalations in capital and operating costs. The broader range of cases also reveals differences not previously reported in the relative costs of PC, NGCC and IGCC plants with and without CCS. While CCS can significantly reduce power plant emissions of CO₂ (typically by 85–90%), the impacts of CCS energy requirements on plant-level resource requirements and multi-media environmental emissions also are found to be significant, with increases of approximately 15–30% for current CCS systems. To characterize such impacts, an alternative definition of the “energy penalty” is proposed in lieu of the prevailing use of this term.     

Electrochemical study of composite materials for coal-based direct carbon fuel cell

The efficient conversion of solid carbon fuels into energy by reducing the emission of harmful gases is important for clean environment. In this regards, direct carbon fuel cell (DCFC) is a system that converts solid carbon directly into electrical energy with high thermodynamic efficiency (100%), system efficiency of 80% and half emission of gases compared to conventional coal power plants. This can generate electricity from any carbonaceous fuel such as charcoal, carbon black, carbon fiber, graphite, lignite, bituminous coal and waste materials. In this paper, ternary carbonate-samarium doped ceria (LNK-SDC) electrolyte has been synthesized via co-precipitation technique, while LiNiCuZnFeO (LNCZFO) electrode has been prepared using solid state reaction method. Due to significant ionic conductivity of electrolyte LNK-SDC, it is used in DCFC. Three types of solid carbon (lignite, bituminous, sub-bituminous) are used as fuel to generate power. The X-ray diffraction confirmed the cubic crystalline structure of samarium doped ceria, whereas XRD pattern of LNCZFO showed its composite structure.The proximate and ultimate coal analysis showed that fuel (carbon) with higher carbon content and lower ash content was promising fuel for DCFC. The measured ionic conductivity of LNK-SDC is 0.0998 Scm^?1 and electronic conductivity of LNCZFO is 10.1 Scm^?1 at 700 °C, respectively. A maximum power density of 58 mWcm^?2 is obtained using sub-bituminous fuel.     

Development of CO2 emission factors from a large circulating fluidized bed boiler

Greenhouse gas emissions of the nation should be precisely assessed in order to effectively tackle the problems stemming from climate changes. To do so, country-specific data that reflect a nation’s distinct characteristics must be applied to more precisely assess greenhouse gas emissions. In this research, carbon emission factors were assessed for emission sources making up over 53% of the domestic anthracite consumption with calorific values of fuels and elementary analysis. Furthermore, oxidation rates were assessed based on measurement results of unburned carbon produced from tested power plants to calculate CO₂ emission factors. Ultimately, the CO₂ emission factor was calculated at 106,747 kg/TJ, about 9% higher than the anthracite emission factor presented by the Intergovernmental Panel on Climate Control. Such differences are assumed to mainly come from disparities of anthracite properties along with combustion technology and differences of oxidation rates depending on the combustion conditions. Therefore, continued research on a wide variety of fuels and energy consumption facilities should be conducted in order to establish country-specific data, which will help more accurately assess greenhouse gas emissions and subsequently will lead to reliable greenhouse gas reduction goals.     

Life cycle inventory analysis for electricity in Korea

A life cycle inventory analysis (LCI) database that encompasses the entire Korean electrical energy grid was developed. The CO₂ emission per functional unit of electricity, 1 kWh of usable electricity, was 0.49 kg/f.u. Contribution of direct emission of CO₂ to the total CO₂ emission was around 95%. In the case of emissions of SO_x, NO_x, and PM, contribution of the upstream processes including raw energy material extraction, transport, and fuel processing to the total emissions were 29%, 26%, and 43%, respectively. Emissions of air pollutants from power generation or direct emissions are much greater in quantity than those from the upstream processes. On the other hand, the opposite is true for the emissions of water pollutants. Bituminous coal was the largest source of emissions of air and water pollutants including CO₂. Natural gas was the best fuel and anthracite coal was the worst fuel with respect to the direct and upstream emissions of air and water pollutants and wastes.     

Quantification of provincial-level carbon emissions from energy consumption in China

Greenhouse gas emission inventories are useful tools for monitoring air quality and assisting local policy development. This article estimates CO₂ emission inventories from energy consumption and carbon intensities of provinces and municipalities in Mainland China in 1990, 1995, 2000, and 2005–2008 using the IPCC mass balance approach. Results show that China's coal-based energy structure and unique economic development have heavily impacted CO₂ emissions. Fortunately, although coal consumption has increased to over 70% of all fuel use, the share of CO₂ emissions from coal has gradually decreased due to energy consumption restructuring. The switch from coal-dominance to cleaner, renewable energies (wind, solar, natural gas, nuclear power, geothermal, biomass energy) will undoubtedly reduce CO₂ emissions in China. Results also indicate that carbon intensity has improved steadily, as China's economic development introduces new technologies intended to minimize environmental pollution and destruction. Our results suggest that China's CO₂ emissions may not be as high as expected in future, and will gradually lessen.     

Trade-off in emissions of acid gas pollutants and of carbon dioxide in fossil fuel power plants with carbon capture

This paper investigates the impact of capture of carbon dioxide (CO₂) from fossil fuel power plants on the emissions of nitrogen oxides (NO_X) and sulphur oxides (SO_X), which are acid gas pollutants. This was done by estimating the emissions of these chemical compounds from natural gas combined cycle and pulverized coal plants, equipped with post-combustion carbon capture technology for the removal of CO₂ from their flue gases, and comparing them with the emissions of similar plants without CO₂ capture. The capture of CO₂ is not likely to increase the emissions of acid gas pollutants from individual power plants; on the contrary, some NO_X and SO_X will also be removed during the capture of CO₂. The large-scale implementation of carbon capture is however likely to increase the emission levels of NO_X from the power sector due to the reduced efficiency of power plants equipped with capture technologies. Furthermore, SO_X emissions from coal plants should be decreased to avoid significant losses of the chemicals that are used to capture CO₂. The increase in the quantity of NO_X emissions will be however low, estimated at 5% for the natural gas power plant park and 24% for the coal plants, while the emissions of SO_X from coal fired plants will be reduced by as much as 99% when at least 80% of the CO₂ generated will be captured.     

A comparative analysis of energy and CO2 taxes on the primary energy mix for electricity generation

In many countries, economies are moving towards internalization of external costs of greenhouse‐gas (GHG) emissions. This can best be achieved by either imposing additional taxes or by using an emission‐permit‐trading scheme. The electricity sector is under scrutiny in the allocation of emission‐reduction objectives, not only because it is a large homogeneous target, but also because of the obvious emission‐reduction potential by decreasing power generation based on carbon‐intensive fuels. In this paper, we discuss the impact of a primary‐energy tax and a CO₂ tax on the dispatching strategy in power generation. In a case study for the Belgian power‐generating context, several tax levels are investigated and the impact on the optimal dispatch is simulated. The impact of the taxes on the power demand or on the investment strategies is not considered. As a conclusion, we find that a CO₂ tax is more effective than a primary‐energy tax. Both taxes accomplish an increased generation efficiency in the form of a promotion of combined‐cycle gas‐fired units over coal‐fired units. The CO₂ tax adds an incentive for fuel switching which can be achieved by altering the merit order of power plants or by switching to a fuel with a lower carbon content within a plant. For the CO₂ tax, 13 €/tonCO₂ is withheld as the optimal value which results in an emission reduction of 13% of the electricity‐related GHG emissions in the Belgian power context of 2000. A tax higher than 13 €/tonCO₂ does not contribute to the further reduction of GHGs. Copyright © 2005 John Wiley & Sons, Ltd.     

The European power plant infrastructure—Presentation of the Chalmers energy infrastructure database with applications

This paper presents a newly established database of the European power plant infrastructure (power plants, fuel infrastructure, fuel resources and CO₂ storage options) for the EU25 member states (MS) and applies the database in a general discussion of the European power plant and natural gas infrastructure as well as in a simple simulation analysis of British and German power generation up to the year 2050 with respect to phase-out of existing generation capacity, fuel mix and fuel dependency. The results are discussed with respect to age structure of the current production plants, CO₂ emissions, natural gas dependency and CO₂ capture and storage (CCS) under stringent CO₂ emission constraints.     

Combustion behavior of single particles from three different coal ranks and from sugar cane bagasse in O2/N2 and O2/CO2 atmospheres

The combustion behavior of single fuel particles was assessed in O₂/N₂ and O₂/CO₂ background gases, with oxygen mole fractions in the range of 20–100%. Fuels included four pulverized coals from different ranks (a high-volatile bituminous, a sub-bituminous and two lignites) as well as pulverized sugarcane-bagasse, a biomass residue. Particles of 75–90 μm were injected under laminar flow in a bench-scale, transparent drop-tube furnace (DTF), electrically-heated to 1400 K where, upon experiencing high heating rates, they ignited and burned. The combustion of individual particles was observed with three-color optical pyrometry and high-speed high-resolution cinematography to obtain temperature and burnout time histories. Based on combined observations from these techniques, a comprehensive understanding of the behaviors of these fuels was developed under a variety of conditions, including simulated oxy-fuel combustion. The fuels exhibited distinct combustion behaviors. In air, the bituminous coal particles burned in two distinctive modes; the volatiles burned in bright envelope flames surrounding the devolatilizing char particles followed by heterogeneous char combustion. The volatile matter of sub-bituminous coal particles burned either in subdued envelope flames, surrounding devolatilizing and occasionally fragmenting chars, or heterogeneously at the char surface. Lignite particles typically burned with extensive fragmentation, and their volatiles burned simultaneously with the char fragments. The volatiles of bagasse particles burned in spherical and transparent envelope flames. Increasing the oxygen mole fraction in N₂, increased flame and char surface temperatures, and decreased burnout times; particles of all fuels burned more intensely with an increasing tendency of the volatiles to burn closer to the char surface. When the background gas N₂ was substituted with CO₂, the combustion of all fuels was distinctly less intense; at moderate O₂ mole fractions (<30%) most particles did not ignite under active flow conditions in the furnace (they did ignite under quiescent gas flow conditions in the DTF). Increasing the oxygen mole fraction in CO₂ increased the likelihood of combustion and its intensity. Combustion of volatiles in envelope flames was suppressed in the presence of CO₂, particularly under active gas flow in the DTF.     

Biomass co-firing options on the emission reduction and electricity generation costs in coal-fired power plants

Co-firing offers a near-term solution for reducing CO₂ emissions from conventional fossil fuel power plants. Viable alternatives to long-term CO₂ reduction technologies such as CO₂ sequestration, oxy-firing and carbon loop combustion are being discussed, but all of them remain in the early to mid stages of development. Co-firing, on the other hand, is a well-proven technology and is in regular use though does not eliminate CO₂ emissions entirely. An incremental gain in CO₂ reduction can be achieved by immediate implementation of biomass co-firing in nearly all coal-fired power plants with minimum modifications and moderate investment, making co-firing a near-term solution for the greenhouse gas emission problem. If a majority of coal-fired boilers operating around the world adopt co-firing systems, the total reduction in CO₂ emissions would be substantial. It is the most efficient means of power generation from biomass, and it thus offers CO₂ avoidance cost lower than that for CO₂ sequestration from existing power plants. The present analysis examines several co-firing options including a novel option external (indirect) firing using combustion or gasification in an existing coal or oil fired plant. Capital and operating costs of such external units are calculated to determine the return on investment. Two of these indirect co-firing options are analyzed along with the option of direct co-firing of biomass in pulverizing mills to compare their operational merits and cost advantages with the gasification option.     

Carbon Dioxide Emissions and Carbonation Sensors

Abstract

The gases with higher heat capacities than those of O₂ and N₂ cause greenhouse effects. Carbon dioxide (CO₂) is the main greenhouse gas associated with global climate change. At the present time, coal is responsible for 30–40% of world CO₂ emissions from fossil fuels. There was a higher correlation between the amount of carbon dioxide emission and percentage of carbon in the fuel for all equations. The squares of correlation coefficients were 0.9999, 0.9978, and 0.9995. The gas sensing characteristics of MgO and CaO as the CO₂ gas sensors and CO₂ emission capacities selected carbonaceous fuels have been investigated. It was found that increasing the percentage of carbon in carbonaceous fuel caused CO₂ emission increase. Carbonation is a stabilization of CO₂ by solidification process. The availability of a CO₂ fixation technology would serve as insurance in case global warming causes severe restrictions on CO₂ emissions. In order to prevent rapid climate change, it will be necessary to stabilize CO₂ as carbonate by the carbonation process. The carbonation was carried out using MgO and CaO as CO₂ sensors. The yield of carbonation increased with increasing temperature. The rate of carbonation conversion sharply increased in the initial 20 min and then reduced and reached a plateau value after about 40 min. The carbonation conversion with MgO is higher than that of CaO.     

Single particle ignition and combustion of anthracite,semi-anthracite and bituminous coals in air and simulated oxy-fuel conditions

A fundamental investigation has been conducted on the combustion behavior of single particles (75–150 μm) of four coals of different ranks: anthracite, semi-anthracite, medium-volatile bituminous and high-volatile bituminous. A laboratory-scale transparent laminar-flow drop-tube furnace, electrically-heated to 1400 K, was used to burn the coals. The experiments were performed in different combustion atmospheres: air (21%O₂/79%N₂) and four simulated dry oxy-fuel conditions: 21%O₂/79%CO₂, 30%O₂/70%CO₂, 35%O₂/65%CO₂ and 50%O₂/50%CO₂. The ignition and combustion of single particles was observed by means of three-color pyrometry and high-speed high-resolution cinematography to obtain temperature–time histories and record combustion behaviors. On the basis of the observations made with these techniques, a comprehensive examination of the ignition and combustion behaviors of these fuels was achieved. Higher rank coals (anthracite and semi-anthracite) ignited heterogeneously on the particle surface, whereas the bituminous coal particles ignited homogeneously in the gas phase. Moreover, deduced ignition temperatures increased with increasing coal rank and decreased with increasing oxygen concentrations. Strikingly disparate combustion behaviors were observed depending on the coal rank. The combustion of bituminous coal particles took place in two phases. First, volatiles evolved, ignited and burned in luminous enveloping flames. Upon extinction of these flames, the char residues ignited and burned. In contrast, the higher rank coal particles ignited and burned heterogeneously. The replacement of the background N₂ gas of air with CO₂ (i.e., changing from air to an oxy-fuel atmosphere) at the same oxygen mole fraction impaired the intensity of combustion. It reduced the combustion temperatures and lengthened the burnout times of the particles. Increasing the oxygen mole fraction in CO₂ to 30–35% restored the intensity of combustion to that of air for all the coals studied. Volatile flame burnout times increased linearly with the volatile matter content in the coal in both air and all oxygen mole fractions in CO₂. On the other hand, char burnout times increased linearly or quadratically versus carbon content in the coal, depending on the oxygen mole fraction in the background gas.     

Reduction of greenhouse gas emission on a medium-pressure boiler using hydrogen-rich fuel control

The increasing emission of greenhouse gases from the combustion of fossil fuel is believed to be responsible for global warming. A study was carried out to probe the influence of replacing fuel gas with hydrogen-rich refinery gas (R.G.) on the reduction of gas emission (CO₂ and NO_x) and energy saving. Test results show that the emission of CO₂ can be reduced by 16.4% annually (or 21,500 tons per year). The NO_x emission can be 8.2% lower, or 75 tons less per year. Furthermore, the use of refinery gas leads to a saving of NT$57 million (approximately US$1.73 million) on fuel costs each year. There are no CO₂, CO, SO_x, unburned hydrocarbon, or particles generated from the combustion of added hydrogen. The hydrogen content in R.G. employed in this study was between 50 and 80 mol%, so the C/H ratio of the feeding fuel was reduced. Therefore, the use of hydrogen-rich fuel has practical benefits for both energy saving and the reduction of greenhouse gas emission.     

Carbon dioxide emission from the Turkish electricity sector and its mitigation options

In this study, electricity generation associated CO₂ emissions and fuel-specific CO₂ emission factors are calculated based on the IPCC methodology using the data of fossil-fueled power plants that ran between 2001 and 2008 in Turkey. The estimated CO₂ emissions from fossil-fueled power plants between 2009 and 2019 are also calculated using the fuel-specific CO₂ emission factors and data on the projected generation capacity of the power plants that are planned to be built during this period. Given that the total electricity supply (planned+existing) will not be sufficient to provide the estimated demand between 2011 and 2019, four scenarios based on using different fuel mixtures are developed to overcome this deficiency. The results from these scenarios show that a significant decrease in the amount of CO₂ emissions from electricity generation can be achieved if the share of the fossil-fueled power plants is lowered. The Renewable Energy Scenario is found to result in the lowest CO₂ emissions between 2009 and 2019. The associated CO₂ emissions calculated based on this scenario are approximately 192 million tons lower than that of the Business As Usual Scenario for the estimation period.     

Significance of CO2-free hydrogen globally and for Japan using a long-term global energy system analysis

In this paper, the significance of CO₂-free hydrogen is discussed using a long-term global energy system. The energy demand–supply system including CO₂-free hydrogen was assumed, though there are still large uncertainties as to whether a global CO₂-free hydrogen energy system will be deployed. System analysis was conducted using the global and long-term intertemporal optimization energy model GRAPE under severe CO₂ emission constraints. Applied global CO₂ constraints for 2050 were a 50% reduction from 1990 levels. CO₂ constraints accounting for Intended Nationally Determined Contributions (INDCs) in each region were also considered. A variety of energy resources and technologies were considered in this model. Hydrogen can be produced from low-grade coal or natural gas with CO₂ capture and electricity from renewable energy. The hydrogen CIF (cost, insurance, and freight) price for Japan was about 3.2 cents/MJ in 2030. Hydrogen demand technologies considered in this paper are hydrogen-fired power plants, direct combustion, combined heat and power (fuel cells, gas engines, and gas turbines), fuel cell vehicles, and hydrogen internal combustion engine vehicles. The majority of CO₂-free hydrogen was deployed in the transportation sector. CO₂-free hydrogen was utilized in the power sector, where deployment of other zero emission technology has some constraints. From an economic viewpoint, CO₂-free hydrogen can reduce the global energy system cost. From the viewpoint of a localized region, such as Japan, deployment of CO₂-free hydrogen can improve energy security and environmental indicators.     

Power sector development in India with CO2 emission targets: Effects of regional grid integration and the role of clean technologies

The power sector in India at present comprises of five separate regional electricity grids having practically no integrated operation in between them. This study analyses the utility planning, environmental and economical effects of integrated power sector development at the national level in which the regional electric grids are developed and operated as one integrated system. It also examines the effects of selected CO₂ emission reduction targets in the power sector and the role of renewable power generation technologies in India. The study shows that the integrated development and operation of the power system at the national level would reduce the total cost including fuel cost by 4912 million $, total capacity addition by 2784 MW, while the emission of CO₂, SO₂ and NO_x would be reduced by 231.6 (1.9%), 0.8 (0.9%), 0.4 (1.2%) million tons, respectively, during the planning horizon. Furthermore, the study shows that the expected unserved energy, one of the indices of generation system reliability, would decrease to 26 GWh under integrated national power system from 5158 GWh. As different levels of CO₂ emission reduction targets were imposed, there is a switching of generation from conventional coal plants to gas fired plants, clean coal technologies and nuclear based plants. As a result the capacity expansion cost has increased. It was found that wind power plant is most attractive and economical in the Indian perspective among the renewable options considered (Solar, wind and biomass). Copyright © 2003 John Wiley & Sons, Ltd.     

Baseload electricity from wind via compressed air energy storage (CAES)

This study investigates two methods of transforming intermittent wind electricity into firm baseload capacity: (1) using electricity from natural gas combined-cycle (NGCC) power plants and (2) using electricity from compressed air energy storage (CAES) power plants. The two wind models are compared in terms of capital and electricity costs, CO₂ emissions, and fuel consumption rates. The findings indicate that the combination of wind and NGCC power plants is the lowest-cost method of transforming wind electricity into firm baseload capacity power supply at current natural gas prices (∼$6/GJ). However, the electricity supplied by wind and CAES power plants becomes economically competitive when the cost of natural gas for electric producers is $10.55/GJ or greater. In addition, the Wind-CAES system has the lowest CO₂ emissions (93% and 71% lower than pulverized coal power plants and Wind-NGCC, respectively) and the lowest fuel consumption rates (9 and 4 times lower than pulverized coal power plants and Wind-NGCC, respectively). As such, the large-scale introduction of Wind-CAES systems in the U.S. appears to be the prudent long-term choice once natural gas price volatility, costs, and climate impacts are all considered.     

Quantitative analysis of potential power production and environmental benefits of Biomass Integrated Gasification Combined Cycles in the European Union

Biomass Integrated Gasification Combined Cycles (BioIGCC) are a promising technology, alternative to fossil fuels for power generation. Significant reduction of CO₂ emissions could be achieved, although important changes in the gas turbines and gasifiers design and further technological development would be necessary. The aim of this work is to study quantitatively the benefits of using BioIGCC plants instead of fossil fuel technologies, in terms of power supply and CO₂ emission avoidance, including the study of pre-combustion CO₂ capture. Different biomass substrates are analysed and compared and the required land use in each case and for different scenarios is also studied and quantified. The power generation and greenhouse gas emission avoidance potential of BioIGCC technology in Europe is also studied and the viability of this technology in different circumstances is discussed. In several cases BioIGCC plants are found to be viable from the point of view of availability of biomass resources and the cost of the produced kWh. In the whole EU-27 the potential hovers around 30 GW and a reduction of nearly 4% of the total EU emissions in 2009 in a conservative scenario, and up to 100 GW and 15% of emission reduction in a more optimistic one.     

Targeting existing power plants: EPA emission reduction with wind and demand response

Electricity generation accounts for 40% of CO₂ emissions from fossil fuel combustion in the United States. Section 111 of the Clean Air Act (CAA) allows for greenhouse gas emission regulation by the US Environmental Protection Agency (EPA). In June 2014, EPA issued the Clean Power Plan that proposes regulation of existing power plants via a “best system of emission reduction” or BSER. Reducing carbon dioxide emissions caused by electricity generation is one of the main motivations for increasing wind power and other renewable energy use, and this option is included in the BSER. This paper applies Monte Carlo simulation with a two-stage power flow optimization framework to analyze the potential CO₂ emission reduction with 10% and 20% wind penetration using the proposed BSER. The results show that EPA's BSER does achieve significant emission reduction, but an increase in cost of electricity and load curtailment can result if significant wind is installed without other measures. These concerns are eliminated by including recourse to real-time demand response along with EPA's BSER, suggesting that the proposed BSER, implemented alone, could be insufficient for reaching EPA's target CO₂ reductions while also safeguarding power system reliability and cost.