Overall CO2 Efficiency Assessment for A Low Carbon Energy System

  • Zhanghua Zheng

Student thesis: Doctoral ThesisPhD


Decarbonization of the power sector is of great importance for the transition to a sustainable and low-carbon world economy. Estimating carbon efficiency in the power sector is a key step to grasp the impact of demand-side usage changes and evaluate their potential environmental benefits. In order to quantify the environmental benefits of demand-side usage changes, Average Emission Factor (AEF) and Marginal Emission Factor (MEF) have been proposed in the electrical power sector. AEF is defined as the ratio of the total CO2 emitted in the system to the total electricity generated. It is an effective factor for reporting on CO2 emissions at system level and on an average basis, but the current AEF model lacks clarity on the factors actually affecting the estimation. MEF is defined as the incremental change in carbon emissions as a result of a change in demand. However, previous MEF assessments did not consider key technical limitations, such as ramp-rate constraint for generators and network constraints, and carbon trading mechanisms. This thesis improves the estimation for both AEF and MEF and key achievements can be summarized as:1). A novel model of estimating AEF, with its application to GB, US and China’s electricity system.2). Improvement on conventional MEF model by considering ramp-rate constraint in dispatch order.3). Sensitivity studies on MEF using current fuel prices and future fuel prices.4). A new model of estimating MEF considering both the utilization level of generators and the carbon costs when determining the dispatch order.5). The effect of power network on MEF estimation, with a comparison of congested scenarios and non-congested scenario.
Date of Award8 Sept 2014
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorFurong Li (Supervisor)


  • CO2 emissions
  • power sector
  • average emission factor
  • marginal emission factor
  • demand response

Cite this