Marginal Electricity Generation Research Articles

Long-term optimization of Egypt’s power sector: Policy implications

This paper presents an evaluation of energy supply strategies for Egypt’s power sector and identifies prospects to meet rising electricity demand while addressing energy security and low-carbon development issues. We apply the TIMES energy system model to examine Egypt’s energy policy goals as reflected in Egypt’s Vision 2030, and specifically: (a) targeted power generation based on renewable energy under two different scenarios; (b) targeted carbon dioxide (CO2) emissions’ mitigation toward low-carbon society development; and (c) constraints on natural gas production for power generation. The quantitative results from the model suggest a need for diversification from predominantly natural gas to a mix of renewable and conventional energy sources in order to improve energy security, reduce dependency on fossil fuels, and reduce carbon dioxide emissions, with the level of diversification changing with different policy options. Although total energy system cost is projected to increase the effects on fossil-fuel dependency, diversity of energy supply-mix, marginal electricity generation price, and GHG mitigation indicate that it may be wise to target promotion of renewable energy for power generation and develop a low-carbon society.

Well-to-wheel water footprints of conventional versus electric vehicles in the United States: A state-based comparative analysis

Today, increasing levels of water demand become a particularly serious challenge for many countries, especially since water is an essential element for production of transportation fuels. Unfortunately, no research efforts as of now have been directed specifically toward understanding the fundamental relationship between the adoption of electric vehicles (EVs) and water demand. This research aims to fill this knowledge gap by analyzing the water consumption and withdrawal impacts resulting from the increased usage of alternative vehicle technologies in the United States. 5 vehicle types - Internal Combustion Vehicles (ICVs), Hybrid Electric Vehicles (HEVs), Plug-in Hybrid Electric Vehicles (PHEV20, PHEV40) and Battery Electric Vehicles (BEVs) - are analyzed across 50 U.S. states with 3 different electricity generation mix profiles: the state-based average electricity generation mix, the state-based marginal electricity generation mix, and a hypothetical electricity generation mix consisting entirely of solar-powered charging stations. The well-to-wheel (WTW) life cycle analysis is used for the water footprint calculations. In worst case, BEVs may consume up to 70 times more water than ICVs. BEVs with solar charging have the lowest levels of water consumption and withdrawal and can reduce transportation water footprint by up to 97%. In most of the states, the marginal electricity generation mix has higher water consumption and withdrawal values than those of the average electricity generation mix. In particular, the authors suggest the use of BEVs with solar charging for states with the highest water-stressed areas (California (CA), Arizona (AZ), Nevada (NV), Florida (FL), etc.), and recommend the inclusion of incentives by federal and state governments for these states.

Ground truthing the environmental benefits of a polygeneration system: When to combine heat and power?

Energy systems are major contributors to critical environmental problems including climate change and air pollution. Over half of global energy end use is in the form of heat, three-quarters of which is from fossil fuels. We assess different ways to provide heat, cooling, and electricity to a university campus, comparing lifecycle primary energy requirements, greenhouse gas (GHG) emissions, and particulate matter impacts. For this case study, replacing cogeneration of cooling, heat, and power with grid electricity and building level heating and cooling can reduce GHG emissions by 30%, while cogeneration of heating and cooling in an electrically powered heat recovery chiller system with thermal energy storage can reduce GHG emissions by 45%. GHG reductions from grid electricity remain even if it is assumed to come from more carbon intensive marginal electricity generation. Prominent factors affecting the environmental benefits of polygeneration are identified, most notably the fuel mix and energy efficiency of regional grid electricity, and combined heat and power system efficiency. Thermal energy storage adds resilience to the system while reducing environmental impacts. A heuristic charts the viability of combined versus separate heat and power production for a general case, based on cogeneration efficiency and regional electricity carbon intensity. Low carbon grid electricity strengthens the case for a shift in polygeneration systems from combined heat and power to combined heating and cooling.

Exploring the suitability of electric vehicles in the United States

This study explores suitability of battery electric vehicles in the United States by considering their potential market share and operations costs as well as the state-specific variations in electricity generation profiles, given current government policies and the social acceptability of the technology. A performance assessment is developed to compare each state and identify major policy efforts that are needed to increase the environmental and economic competitiveness of electric vehicles. A novel multi-criteria decision-support framework, integrating Life Cycle Assessment, Data Envelopment Analysis, and Agent Based Modeling, is developed. To this end, the environmental and economic impacts of battery electric vehicles are calculated based on three scenarios: an average electricity generation mix, a marginal electricity generation mix, and a solely renewable energy mix with 100% solar. The states are classified, each requiring different policy strategies, in accordance with their performance scores. The results provide important insights for advancing transportation policies and a novel framework for multi-criteria decision-making in the future analyses.

Boosting the adoption and the reliability of renewable energy sources: Mitigating the large-scale wind power intermittency through vehicle to grid technology

The integration of wind energy in the electricity sector and the adoption of electric vehicles in the transportation sector both have the potential to significantly reduce greenhouse gas emissions individually as well as in tandem with Vehicle-to-Grid technology. This study aims to evaluate the greenhouse gas emission savings of mitigating intermittency resulting from the introduction of wind power through Vehicle-to-Grid technologies, as well as the extent to which the marginal electricity consumption from charging an electric vehicle fleet may weaken this overall environmental benefit. To this end, the comparisons are conducted in seven independent system operator regions. The results indicate that, in most cases, the emission savings of a combination of wind power and Vehicle-to-Grid technology outweighs the additional emissions from marginal electricity generation for electric vehicles. In addition, the fluctuations in newly-integrated wind power could be balanced in the future using EVs and V2G technology, provided that a moderate portion of EV owners is willing to provide V2G services. On the other hand, such a combination is not favorable if the Vehicle-to-Grid service participation rate is less than 5% of all electric vehicle owners within a particular region.

Marginal Generation Technology in the Chinese Power Market towards 2030 Based on Consequential Life Cycle Assessment

Electricity consumption is often the hotspot of life cycle assessment (LCA) of products, industrial activities, or services. The objective of this paper is to provide a consistent, scientific, region-specific electricity-supply-based inventory of electricity generation technology for national and regional power grids. Marginal electricity generation technology is pivotal in assessing impacts related to additional consumption of electricity. China covers a large geographical area with regional supply grids; these are arguably equally or less integrated. Meanwhile, it is also a country with internal imbalances in regional energy supply and demand. Therefore, we suggest an approach to achieve a geographical subdivision of the Chinese electricity grid, corresponding to the interprovincial regional power grids, namely the North, the Northeast, the East, the Central, the Northwest, and the Southwest China Grids, and the China Southern Power Grid. The approach combines information from the Chinese national plans on for capacity changes in both production and distribution grids, and knowledge of resource availability. The results show that nationally, marginal technology is coal-fired electricity generation, which is the same scenario in the North and Northwest China Grid. In the Northeast, East, and Central China Grid, nuclear power gradually replaces coal-fired electricity and becomes the marginal technology. In the Southwest China Grid and the China Southern Power Grid, the marginal electricity is hydropower towards 2030.

Spatial and temporal variations of marginal electricity generation: the case of the Finnish, Nordic, and European energy systems up to 2030

Assumptions related to energy generation often play a decisive role in abatement studies for estimating the effects of demand-side interventions. However, there can be significant geographical and temporal variation in the emission intensities of electricity generation in different regions. The aim of this article is to describe how spatial and temporal variations related to a particular energy system may affect an electricity generation unit operating on the margins. The approach takes the generation mix within interconnected electricity markets and the exchange of electricity between these markets into account. The short-term (2009–2010) and long-term (until 2030) hour-by-hour marginal electricity generation unit and marginal emission intensities are identified for electricity use, using the Finnish, Nordic and European energy systems as actual cases. The estimated marginal electricity generation technology and marginal emission intensities for electricity use differed significantly within the studied time horizon and between the studied countries and energy systems. Furthermore, due to the projected structural changes in the energy systems, i.e. changes in the fuel mix and electricity generation technologies, the carbon dioxide (CO2) intensity of marginal electricity generation will decrease in the Nordic countries and in the EU in the long-term. However, the approach used for calculating the effect of change in electricity exchange on the margin increased the variability of the results considerably for some Nordic countries, such as Sweden and Norway, whose export of electricity was high and whose marginal generation mix differed significantly from the European system. Furthermore, the spatial and temporal variations of marginal electricity generation will increase in the future. This variation, combined with the interconnections between market areas for exchanging electricity in the EU will require improved understanding of the impacts of exchanged marginal electricity generation on the possible emission leakage between EU countries to better inform policy decisions.

An investigation of the techno-economic impact of internal combustion engine based cogeneration systems on the energy requirements and greenhouse gas emissions of the Canadian housing stock

This study provides a techno-economic evaluation of retrofitting internal combustion engine (ICE) based cogeneration systems in the Canadian housing stock (CHS). The study was conducted using the Canadian Hybrid Residential End-Use Energy and GHG Emissions Model (CHREM). CHREM includes close to 17,000 unique house files that are statistically representative of the Canadian housing stock. The cogeneration system performance was evaluated using a high resolution integrated building performance simulation software. It is assumed that the ICE cogeneration system is retrofitted into all houses that currently use a central space heating system and have a suitable basement or crawl space. The GHG emission intensity factor associated with marginal electricity generation in each province is used to estimate the annual GHG emissions reduction due to the cogeneration system retrofit. The results show that cogeneration retrofit yields 13% energy savings in the CHS. While the annual GHG emissions would increase in some provinces due to cogeneration retrofits, the total GHG emissions of the CHS would be reduced by 35%. The economic analysis indicates that ICE cogeneration system retrofits may provide an economically feasible opportunity to approach net/nearly zero energy status for existing Canadian houses.

Conventional, hybrid, plug-in hybrid or electric vehicles? State-based comparative carbon and energy footprint analysis in the United States

Abstract Electric vehicles (EVs), plug-in hybrid electric vehicles (PHEVs), and hybrid electric vehicles (HEVs) are often considered as better options in terms of greenhouse gas emissions and energy consumption compared to internal combustion vehicles. However, making any decision among these vehicle options is not a straightforward process due to temporal and spatial variations, such as the sources of the electricity used and regional driving patterns. In this study, we compared these vehicle options across 50 states, taking into account state-specific average and marginal electricity generation mixes, regional driving patterns, and vehicle and battery manufacturing impacts. Furthermore, a policy scenario proposing the widespread use of solar energy to charge EVs and PHEVs is evaluated. Based on the average electricity generation mix scenario, EVs are found to be least carbon-intensive vehicle option in 24 states, while HEVs are found to be the most energy-efficient option in 45 states. In the marginal electricity mix scenario, widespread adoption of EVs is found to be an unwise strategy given the existing and near-future marginal electricity generation mix. On the other hand, EVs can be superior to other alternatives in terms of energy-consumption, if the required energy to generate 1 kW h of electricity is below 1.25 kW h.

Erratum to the ‘Greenhouse gas emission intensity factors for marginal electricity generation in Canada’International Journal of Energy Research2010; 34:1309-1327

Erratum to the ‘Greenhouse gas emission intensity factors for marginal electricity generation in Canada’<i>International Journal of Energy Research</i>2010; 34:1309-1327

Greenhouse gas emission intensity factors for marginal electricity generation in Canada

In Canada, each province has its own electric utility system, and each system is responsible for meeting the demand of its customer base. Electricity demand in all provinces is highly variable throughout the day, as well as during the year. In order to achieve a good match between electricity demand and generation, a mix of base, intermediate and peaking load power plants is used, which uses different fuel sources. When a renewable energy technology or an energy efficiency measure that results in electricity savings is implemented on a regional, provincial and national scale, the electricity savings reflect in the peak (marginal) electricity generation. Thus, the greenhouse gas (GHG) emission reduction due to the reduction in electricity generation corresponds to the fuel used to generate the electricity at the margin. In Canada, the fuel used for marginal electricity generation varies from province to province and from hour to hour. To estimate the reduction in GHG emissions due to reducing electricity generation at the margin, it is necessary to have information on the fuel mix used to generate the marginal electricity for each province on a suitable time scale. With such information, it is possible to estimate a marginal GHG emission intensity factor for each province, which would provide the amount of GHG emissions produced as result of producing 1 kWh of electricity on the margin. However, such information is regarded confidential by most electric utilities and is not made public. In this paper, methodologies are presented to estimate the GHG intensity factors (GHGIFs) for marginal electricity generation for each province of Canada based on the information available in the public domain. The GHGIFs developed for each province are also presented, which are expected to be valid within the next 5-year horizon. Copyright © 2010 John Wiley & Sons, Ltd.

Well-To-Wheels Energy Use and Greenhouse Gas Emissions of Plug-in Hybrid Electric Vehicles

Researchers at Argonne National Laboratory expanded the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model and incorporated the fuel economy and electricity use of alternative fuel/vehicle systems simulated by the Powertrain System Analysis Toolkit (PSAT) to conduct a well-to-wheels (WTW) analysis of energy use and greenhouse gas (GHG) emissions of plug-in hybrid electric vehicles (PHEVs). The WTW results were separately calculated for the blended charge-depleting (CD) and charge-sustaining (CS) modes of PHEV operation and then combined by using a weighting factor that represented the CD vehicle-miles-traveled (VMT) share. As indicated by PSAT simulations of the CD operation, grid electricity accounted for a share of the vehicle's total energy use, ranging from 6% for a PHEV 10 to 24% for a PHEV 40, based on CD VMT shares of 23% and 63%, respectively. In addition to the PHEV's fuel economy and type of on-board fuel, the marginal electricity generation mix used to charge the vehicle impacted the WTW results, especially GHG emissions. Three North American Electric Reliability Corporation regions (4, 6, and 13) were selected for this analysis, because they encompassed large metropolitan areas (Illinois, New York, and California, respectively) and provided a significant variation of marginal generation mixes. The WTW results were also reported for the U.S. generation mix and renewable electricity to examine cases of average and clean mixes, respectively. For an all-electric range (AER) between 10 mi and 40 mi, PHEVs that employed petroleum fuels (gasoline and diesel), a blend of 85% ethanol and 15% gasoline (E85), and hydrogen were shown to offer a 40-60%, 70-90%, and more than 90% reduction in petroleum energy use and a 30-60%, 40-80%, and 10-100% reduction in GHG emissions, respectively, relative to an internal combustion engine vehicle that used gasoline. The spread of WTW GHG emissions among the different fuel production technologies and grid generation mixes was wider than the spread of petroleum energy use, mainly due to the diverse fuel production technologies and feedstock sources for the fuels considered in this analysis. The PHEVs offered reductions in petroleum energy use as compared with regular hybrid electric vehicles (HEVs). More petroleum energy savings were realized as the AER increased, except when the marginal grid mix was dominated by oil-fired power generation. Similarly, more GHG emissions reductions were realized at higher AERs, except when the marginal grid generation mix was dominated by oil or coal. Electricity from renewable sources realized the largest reductions in petroleum energy use and GHG emissions for all PHEVs as the AER increased. The PHEVs that employ biomass-based fuels (e.g., biomass-E85 and -hydrogen) may not realize GHG emissions benefits over regular HEVs if the marginal generation mix is dominated by fossil sources. Uncertainties are associated with the adopted PHEV fuel consumption and marginal generation mix simulation results, which impact the WTW results and require further research. More disaggregate marginal generation data within control areas (where the actual dispatching occurs) and an improved dispatch modeling are needed to accurately assess the impact of PHEV electrification. The market penetration of the PHEVs, their total electric load, and their role as complements rather than replacements of regular HEVs are also uncertain. The effects of the number of daily charges, the time of charging, and the charging capacity have not been evaluated in this study. A more robust analysis of the VMT share of the CD operation is also needed.

Life cycle assessment of fuels for district heating: A comparison of waste incineration, biomass- and natural gas combustion

The aim of this consequential life cycle assessment (LCA) is to compare district heating based on waste incineration with combustion of biomass or natural gas. The study comprises two options for energy recovery (combined heat and power (CHP) or heat only), two alternatives for external, marginal electricity generation (fossil lean or intense), and two alternatives for the alternative waste management (landfill disposal or material recovery). A secondary objective was to test a combination of dynamic energy system modelling and LCA by combining the concept of complex marginal electricity production in a static, environmental systems analysis. Furthermore, we wanted to increase the methodological knowledge about how waste can be environmentally compared to other fuels in district-heat production. The results indicate that combustion of biofuel in a CHP is environmentally favourable and robust with respect to the avoided type of electricity and waste management. Waste incineration is often (but not always) the preferable choice when incineration substitutes landfill disposal of waste. It is however, never the best choice (and often the worst) when incineration substitutes recycling. A natural gas fired CHP is an alternative of interest if marginal electricity has a high fossil content. However, if the marginal electricity is mainly based on non-fossil sources, natural gas is in general worse than biofuels.

97/03857 Long-run marginal electricity generation costs in Israel

97/03857 Long-run marginal electricity generation costs in Israel

Long-run marginal electricity generation costs in Israel

This paper presents two methods for calculating long-run marginal electricity generation costs based on the techniques used for long-term expansion planning. According to the first method, long-run marginal costs are calculated as incremental costs required to supply additional demands-peak, shoulder and off-peak demands, to each hourly demand group separately. These costs include the present value of capital, fuel and operation and maintenance (O&M) costs throughout the planning period. In the second method, the long-run marginal capacity cost element is calculated as an additional/reduced cost resulting from bringing forward/postponing generation capacity investments, in order to supply incremented/decremented demands in every hour throughout the planning period. The annualized marginal capacity cost is allocated among the hours according to the distribution of the unsupplied energy, and is added to the energy marginal cost to obtain the long-run marginal cost. Both methods are implemented through models used for long-term optimal generation system expansion planning. In addition, the second method uses a chronological simulation of generation system operation. A detailed case study of the Israeli electric generation system is also presented.

Decentralization and initiative: TVA returns to its roots

The Tennessee Valley Authority, a federal corporation established by Congress in 1933, is charged with the integrated regional development of the Tennessee Valley's resources, including flood control, navigation, reforestation and proper use of marginal lands, electricity generation, and agricultural and economic development. TVA's early leaders, especially David E. Lilienthal and Gordon R. Clapp, articulated a doctrine of “grass roots democracy” and “decentralization” that protected TVA from rival federal bureaucracies and provided greater flexibility and freedom in carrying out TVA's multi-purpose mission. This doctrine also led to innovations in the professionalization of TVA' s highly skilled and diverse workforce. Clapp, a recognized leader in public administration, promoted employee initiative, easy access to top management, multi-disciplinary teamwork, labor/management collaboration, and partnerships with states and localities that took account of local needs and values. The development of joint co...