Carbon Intensity Of Electricity Research Articles

UK grid electricity carbon intensity can be reduced by enhanced oil recovery with CO2 sequestration

ABSTRACTEnhanced Oil Recovery (EOR) using CO2 coupled with Carbon Capture and Storage (CCS) can potentially accelerate CO2 storage investment through creation of a large commercial market for EOR . This article assesses how coupled a CCS-EOR scenario might contribute to decarbonization of UK grid electricity. Progressive introduction of 11 CCS-to-EOR gas-power plant projects from 2020 is estimated to store 52 Mt CO2 yr−1 from 2030. These 11 projects produce extra revenue of 1100 MM bbls of taxable EOR oil from 2020 to 2049. After each 20-year EOR project ceases, its infrastructure is paid for, and has many years of life. UK climate change targets would necessitate continued CO2 storage at low cost. Considering all greenhouse gas emissions – from power generation, CCS-EOR operations, and oil production and combustion – this project suite emits an estimated 940–1068 Mt CO2e from 2020 to 2049, while storing 1358 Mt CO2. The total average electricity grid factor in the UK reduces to 90–142 kg CO2e MWh−1, with gas generating 132 TWh yr-1. This life-cycle analysis (LCA) is unusual in linking oil production and combustion with CCS and gas-fueled electricity, yet provides a net carbon reduction, and progressively reduces net oil combustion emissions beyond 2040.

China’s electricity emission intensity in 2020 – an analysis at provincial level

In order to maintain the 2°C climate change target, global carbon intensity of electricity generation needs to achieve a short-term target of 600 g/kWh by 2020. This target is important for China, which has been the largest consumer and producer of electricity since 2011. China has set ambitious targets to reduce its electricity carbon intensity in the 13th five-year plan. For a country as large as China, the outcomes of these policies rely on the implementation strategies and effectiveness of each province. In this study, we estimate the carbon intensities of power generation in China’s provinces by 2020. Results show that despite progress in renewable energy growth most provinces are expected to have carbon intensities well above 600 g/kWh by 2020. Renewable energy sources can help reduce carbon intensities in most provinces, but the magnitude of such impacts depends on the coordination among provinces. The over-dependence on coal power generation has made carbon capture and storage a necessity for China’s provinces to reduce their carbon intensity for power generation. Therefore, government support should be addressed sooner rather than later.

Drivers of stagnating global carbon intensity of electricity and the way forward

Despite the signing of the Paris climate agreement, there is still great uncertainty regarding the world's ability to decarbonize and meet the 2°C target. In this regard, the electricity production sector deserves particular attention. The sector has the largest decarbonization potential and its share of the world's CO2 emissions from fuel combustion increased from 30% in 1990 to 36% in 2014. To better understand global trends, this study analyses the factors influencing changes in the global aggregate carbon intensity (ACI) of electricity, a measure of the level of CO2 emissions per unit of electricity produced, over the last 25 years using multidimensional index decomposition analysis. It finds that global ACI barely improved since 1990 because of a shift in electricity production from developed to developing countries with higher ACIs. This geographical shift offset consistent improvements to power generation efficiency worldwide and is likely to persist in the future. To keep the 2°C target realisable, it is imperative to enhance international cooperation to lower the ACIs of emerging economies and deepen the penetration of renewables, which have thus far performed below expectations.

Decomposition of carbon intensity in electricity production: Technological innovation and structural adjustment in China's power sector

China's power generation accounted for 24% of the world's total output, ranking first in 2015. As a suitable performance indicator, carbon intensity of electricity reflects a variation in the average level of carbon emissions per unit of electricity generated. As the largest carbon emitter among various industries, power sector is in duty bound to reduce carbon emissions and achieve sustainable development. Great progress has been made in China's power sector, which is reflected by the effects of technological innovation and structural adjustment. With logarithm transformation and integral transformation, three-dimensional decomposition model is proposed to quantitatively measure the changed carbon intensity of electricity due to technological innovation and structural adjustment. In the context of three-dimensional model, the variation of carbon intensity can be decomposed into absolute changes and/or relative changes. Furthermore, accumulative decomposition results are obtained by chain linked calculation rules. Finally, the proposed models are implemented in China's power industry to reveal its historical progress during 1980–2014. Some important conclusions are also found based on the decomposition results.

Electricity carbon intensity in European Member States: Impacts on GHG emissions of electric vehicles

The Well-To-Wheels (WTW) methodology is widely used for policy making in the transportation sector. In this paper updated WTW calculations are provided, relying on 2013 statistic data, for the carbon intensity (CI) of the European electricity mix; detail is provided for electricity consumed in each EU Member State (MS). An interesting aspect presented is the calculation of the GHG content of electricity traded between Countries, affecting the carbon intensity of the electricity consumed at national level. The amount and CI of imported electricity is a key aspect: a Country importing electricity from another Country with a lower CI of electricity will lower, after the trade, its electricity CI, while importing electricity from a Country with a higher CI will raise the CI of the importing Country. In average, the CI of electricity used in EU at low voltage in 2013 was 447 gCO2eq/kWh, which is the 17% less compared to 2009. Then, some examples of calculation of GHG emissions from the use of electric vehicles (EVs) compared to internal combustion engine vehicles are provided. The use of EVs instead of gasoline vehicles can save (about 60% of) GHG in all or in most of the EU MSs, depending on the estimated consumption of EVs. Compared with diesel, EVs show average GHG savings of around 50% and not savings at all in some EU MS.

Review of the Fuel Saving, Life Cycle GHG Emission, and Ownership Cost Impacts of Lightweighting Vehicles with Different Powertrains.

The literature analyzing the fuel saving, life cycle greenhouse gas (GHG) emission, and ownership cost impacts of lightweighting vehicles with different powertrains is reviewed. Vehicles with lower powertrain efficiencies have higher fuel consumption. Thus, fuel savings from lightweighting internal combustion engine vehicles can be higher than those of hybrid electric and battery electric vehicles. However, the impact of fuel savings on life cycle costs and GHG emissions depends on fuel prices, fuel carbon intensities and fuel storage requirements. Battery electric vehicle fuel savings enable reduction of battery size without sacrificing driving range. This reduces the battery production cost and mass, the latter results in further fuel savings. The carbon intensity of electricity varies widely and is a major source of uncertainty when evaluating the benefits of fuel savings. Hybrid electric vehicles use gasoline more efficiently than internal combustion engine vehicles and do not require large plug-in batteries. Therefore, the benefits of lightweighting depend on the vehicle powertrain. We discuss the value proposition of the use of lightweight materials and alternative powertrains. Future assessments of the benefits of vehicle lightweighting should capture the unique characteristics of emerging vehicle powertrains.

GHG emission balances and prospects of hydrogen enhanced synthetic biofuels from solid biomass in the European context

The European Commission has proposed a minimum share of 3.6% for advanced biofuels in transport in 2030. Satisfying this target using synthetic biofuels would require 48–62Mt/a of forest residue feedstock. If all biofuel plants were maximally enhanced with additional hydrogen input, the biomass demand would be reduced by 35Mt to 16–24Mt/a. As sustainable biomass is a limited resource, such drastic improvements in the efficiency of biomass use have a favourable impact on biomass availability. In this work we assume electrolysis of water as the source of hydrogen and investigate the GHG emission balances of hydrogen enhanced biofuels using the calculation method provided in the European Union’s sustainability criteria for biofuels. The required 70% emission saving compared to fossil fuels is achieved when the carbon intensity of electricity remains under 84–110gCO2/kWh, depending on the process configuration. In addition, we study the possibility that an emission factor could be allocated to the wood biomass, referring to recent discussions on climate impacts of forest bioenergy. Without hydrogen enhancement, the emission factor needs to remain below 13gCO2/MJwood to meet the 70% requirement, while for hydrogen-enhanced configurations it could increase to 36gCO2/MJwood, under the assumption of zero emission electricity.

한국의 스마트 그리드를 위한 신재생에너지원 생산과 활용률 간의 상관관계 분석

In order to prohibit global warming, various kinds of regulatory policies have been established in the whole world. One example is the establishment of the Renewable Portfolio Standard. It requires the increased portion in energy production from renewable energy sources. The Republic of Korea adopted the act on the promotion of the development, use, and diffusion of new and renewable energy since 2012. However, in spite of the effort on the consideration of the renewable energy sources, it was reported the carbon intensity of electricity in Korea was not that low in 2015. Thus, it is required to examine the recent state of the utilization degree of the renewable energy sources in Korea. This paper analyzed the statistical data provided by Korea Power Exchange (KPX) to examine any problems and solutions for generating electricity from the renewable energy sources. We focused on the generation capacity provided by the power plants participated in the market, the electric power trading amount, and the utilization coefficient for 10 years. By analyzing the data, we provide an alternative to solve some imbalance among the factors contributing to renewable energy use.

Carbon intensity of electricity in ASEAN: Drivers, performance and outlook

The Association of Southeast Asian Nations (ASEAN), with its ten member countries, has a total population exceeding 600 million. Its energy-related CO2 emissions have been growing and in 2013 amounted to 3.6% of total global emissions. About 40% of ASEAN's energy-related CO2 emissions are currently attributable to electricity production. In view of this high share, we study the CO2 emissions of ASEAN's electricity production sector with a focus on the aggregate emission intensity (ACI) given by the level of CO2 emissions for each unit of electricity produced. Drivers of ACI are analysed for individual countries and spatial analysis is conducted by comparing factors contributing to differences between the ACIs of individual countries and that of the ASEAN average. Arising from these analyses and in light of the current developments, it is concluded that drastic actions need to be taken both at the national and regional levels in order to reduce growth in the region's electricity-related CO2 emissions. Two key policy issues, namely overcoming national circumstances to improve electricity generation mix and improving power generation efficiency, are further discussed.

Comparative analysis of energy intensity and carbon emissions in wastewater treatment in USA, Germany, China and South Africa

Currently almost all wastewater treatment plants (WWTPs) require a large amount of energy input to process the influent, mostly as electricity, and the associated carbon emissions are in aggregate significant. In order to achieve carbon neutrality, it is important to understand direct and indirect carbon emissions generated by WWTPs. Here, we focused on electricity use in WWTPs as it is a major source of carbon emissions. Specifically, we compared the electricity intensity and associated carbon emissions of WWTPs in four countries: the USA, Germany, China, and South Africa. We found that 100% energy self-sufficient WWTPs are feasible by a combination of increased energy efficiency and energy harvesting from the wastewater. Carbon emissions of WWTPs depend strongly on the electricity fuel mix, wastewater treatment technologies, treatment capacity, and influent and effluent water quality. A few WWTPs operating in developed countries (USA and Germany) have already achieved almost 100% (or higher) electricity self-sufficiency through energy efficiency and harvesting biogas and electricity. In comparison with Germany, WWTPs in the USA are more heterogeneous and the range of unit carbon emission intensity is much wider. In some areas where the organic content in wastewater is lower and less biogas is produced, it is still possible to achieve energy self-sufficiency by using thermal energy from wastewater. Industrial wastewater in China in general consumes more electricity and the carbon intensity of electricity is also higher, resulting in much higher unit carbon emissions as compared with other countries. In megacities such as Shanghai, larger capacity of centralized WWTPs can decrease the unit carbon emissions significantly. These findings provide a global perspective on the state of WWTPs and are helpful to improve the understanding, designing and operating of WWTPs from the perspective of achieving carbon neutrality.

A mixed integer nonlinear programming (MINLP) supply chain optimisation framework for carbon negative electricity generation using biomass to energy with CCS (BECCS) in the UK

The co-firing of biomass and fossil fuels in conjunction with CO2 capture and storage (CCS) has the potential to lead to the generation of relatively inexpensive carbon negative electricity. In this work, we use a mixed integer nonlinear programming (MINLP) model of carbon negative energy generation in the UK to examine the potential for existing power generation assets to act as a carbon sink as opposed to a carbon source. Via a Pareto front analysis, we examine the technical and economic compromises implicit in transitioning from a dedicated fossil fuel only to a carbon negative electricity generation network. A price of approximately £30–50/tCO2 appears sufficient to incentivise a reduction of carbon intensity of electricity from a base case of 800kg/MWh to less than 100kg/MWh. However, the price required to incentivise the generation of carbon negative electricity is in the region of £120–175/t of CO2. In order for biomass to energy with CCS (BECCS) to be commercially attractive, the power plants in question must operate at a high load factor and high rates of CO2 capture. The relative fuel cost is a key determinant of required carbon price. Increasing biomass availability also reduces the cost of generating carbon negative electricity; however one must be cognisant of land use change implications.

A framework for allocating greenhouse gas emissions from electricity generation to plug-in electric vehicle charging

Abstract This paper describes a number of different allocation methods for assigning greenhouse gas emissions from electricity generation to charging plug-in electric vehicles. These methods for calculating the carbon intensity of electricity are discussed in terms of merits and drawbacks and are placed into a framework to aid in understanding the relation with other allocation methods. Three independent decisions are used to define these methods (average vs. marginal, aggregate vs. temporally-explicit, and retrospective vs. prospective). This framework is important because the use of different methods can lead to very different carbon intensities and studies or analyses that do not properly identify the methods used can confuse policymakers and stakeholders, especially when compared to other studies using different methods.

Multicriteria optimization of a distributed energy supply system for an industrial area

In the paper a multi-objective optimization model for distributed energy supply systems optimization is presented. The superstructure of the system comprehends a district heating network that connects the users to each other, small-scale CHP systems, large centralized solar plant and a thermal storage. The optimization has to determine the optimal structure of the system, the size of each component inside the optimal solution and the optimal operation strategy. The multi-objective optimization is based on a MILP (Mixed Integer Linear Programming) model and takes into account as objective function a linear combination of the annual cost for owning, maintaining and operating the whole system and the CO2 emissions associated to the system operation. The model allows to obtain different optimal solutions by varying the relative weight of the economic and the environmental objectives. In this way the Pareto Front is identified and the possible improvements in both economic and environmental terms can be highlighted. The model has been applied to a specific case study and it has been optimized for different superstructure configurations and for two different values of the electricity carbon intensity. The obtained results show that the solar plant, coupled with the optimal thermal storage, allows reaching both environmental and economic goals.

Fuel electricity and plug-in electric vehicles in a low carbon fuel standard

Electricity is unique among the alternative fuels in a low carbon fuel standard (LCFS) policy, in that demand from vehicles is the major barrier to its usage, not supply. This paper presents a policy discussion and policy recommendations on a number of topics related to the regulation and incentives for fuel electricity within the LCFS. In the near-term, the LCFS will have a limited role in incentivizing the use of electricity and lowering the carbon intensity of electricity, and electricity will play a small role in meeting LCFS targets. Calculating a carbon intensity value for electricity is a complex process, requiring many decisions and trade-offs to be made, including allocation methods, system boundaries, temporal resolution and how to treat electricity demand for vehicle charging. These choices along with other regulatory decisions about who can obtain LCFS credits will influence the incentives for providing electricity and charging infrastructure relative to other low-carbon fuels as well as across different electricity providers. The paper discusses how fuel electricity would fit into an LCFS, identifying those special characteristics that could reduce the effectiveness of the policy. It also provides specific recommendations to enable better policy design that appropriately incentivizes the use of low-carbon fuels.

Influence of the carbon intensity of electricity on carbon savings from CHP

The carbon intensity of electricity is a key input to calculations of carbon emissions from buildings, and can be decisive in the selection of low- and zero-carbon technologies. The origin of the value for the carbon intensity of electricity is not well understood and its derivation is investigated. The carbon savings from gas-fired combined heat and power (CHP) vary greatly depending on the carbon intensity of electricity. The current debate about the effectiveness of CHP centres on detailed considerations about which values for the carbon intensity of electricity should be used. The expected future decarbonization of the electricity supply grid would considerably reduce carbon intensities, thus the longer-term trends in carbon intensity and their effect on the carbon savings from CHP are of greater importance. A new expression has been developed to describe the carbon savings from CHP and trigeneration as a function of varying carbon intensity of electricity. While CHP can offer limited carbon savings in the short-term, the future decarbonization of the electricity grid means that CHP will soon be among the most carbon-intensive technologies, and the use of trigeneration will cease to provide carbon savings even sooner. L'intensité carbone de l'électricité est un élément clé de calcul des émissions de carbone des bâtiments et peut être décisive dans le choix des technologies bas carbone et zéro carbone. L'origine de la valeur de l'intensité carbone de l'électricité n'est pas bien comprise et son mode de calcul est étudié. Les économies de carbone réalisées grâce à la production combinée chaleur-électricité (PCCE) issue du gaz varient considérablement selon l'intensité carbone de l'électricité. Les débats actuels sur l'efficacité de la production combinée chaleur-électricité (PCCE) se concentrent sur des considérations détaillées relatives aux valeurs qui devraient être utilisées concernant l'intensité carbone de l'électricité. La future décarbonisation prévue du réseau de distribution d'électricité réduirait considérablement les intensités carbone, de sorte que les tendances à plus long terme en matière d'intensité carbone et leur effet sur les économies de carbone réalisées grâce à la PCCE sont de la plus grande importance. Il a été élaboré une nouvelle expression permettant de décrire les économies de carbone réalisées grâce à la PCCE et à la trigénération comme étant une fonction de l'intensité carbone variable de l'électricité. Bien que la PCCE puisse assurer à court terme des économies de carbone limitées, la future décarbonisation du réseau de distribution d'électricité signifie que la PCCE figurera bientôt au nombre des technologies affichant les plus fortes intensités carbone et que l'utilisation de la trigénération cessera encore plus tôt d'assurer des économies d'énergie. Mots clés: réglementation du bâtiment, émissions de carbone, intensité carbone de l'électricité, production combinée chaleur-électricité (PCCE), technologies bas carbone et zéro carbone, bâtiments bas carbone, trigénération

Interactions between electricity-saving measures and carbon emissions from power generation in England and Wales

The relationship between electricity demand reduction and the consequent change in carbon emissions is central to greenhouse gas emissions policy. This paper examines this relationship for the power system of England and Wales. Previous analysis showed that the commonly used conversion factor based on the system average emission factor significantly underestimates these savings (Hitchin and Pout, 2002. The carbon intensity of electricity: how many kgC per kWhe?. Building Serv. Eng. Res. Technol. 23(4)). Thus any policy analysis based on the system-average emission factor will under-estimate the potential for carbon savings from reductions in electricity demand. The present paper extends the previous analysis by using more detailed modelling to explore differences between demand reductions of differing load shape and magnitude; and the sensitivity of these figures to changes of the fuel mix of the generation system. The new analysis confirms that the carbon savings are consistently greater than those calculated from the annual system average emission factors, and that they vary with end use and scale of demand reduction. However, no systematic differences between end-uses could be discerned. It is therefore recommended that a general incremental carbon emission factor should be used for initial assessments irrespective of end-use. Under current expectations of changes to the generation fuel mix, the incremental carbon intensity will fall more rapidly than the system-average mix. A similar reduction in carbon intensity is also present in the other scenarios explored, but is sometimes more and sometimes less marked.

The carbon intensity of electricity: how many kgC per kWhe?

While it is relatively easy to describe how a change in electricity demand causes a change in carbon emissions from a system of grid-supplied power, it is by no means easy to quantify this. The following have all been used to determine the carbon emissions from changes in electricity demand: • the system-average carbon intensity (that is, the ratio between all carbon emitted to all power distributed); • the carbon intensity of the typical marginal plant; and • the carbon intensity of new plant built or avoided. All of these are valid in certain circumstances, but in others can give misleading results. This paper brings together existing information and new results of modeling a limited number of situations to propose, pro tem, a working set of figures for England and Wales, together with recommendation for their application. Further modelling and analysis is proposed to refine thesefigures.