Transitioning to Low Carbon Power Generation by Integrating Renewables with Fossil Energy

摘要

It is expected that environmental regulations will be enacted to restrict the amount ofcarbon emissions from today’s power plants. As such, it is likely that carbon capture andsequestration (CCS) technologies will be added to both new and existing coal-fired power plantsto achieve compliance. Conventional CCS technologies, however, consume a great deal ofenergy for a given greenhouse gas footprint and hence introduce a significant energy penalty tothe net output of the plant. Most often the energy for CCS operation is proposed to come fromfossil sources with a large CO_2 emission rate. The Office of Systems, Analyses, and Planning atthe National Energy Technology Laboratory is evaluating the integration of both biomass andsolar energy into new and existing coal-fired power plants as a means to offset the powerpenalties and boost emissions benefits associated with CCS.Adding renewable biomass as a fuel in power cycles can reduce lifecycle greenhouse gas(GHG) emissions without incorporating conventional CCS technologies. The reduction of powerplant CO_2 emissions resulting from co-utilization of biomass with coal is directly proportional tothe amount of biomass fed to the plant; however this benefit is partially offset by the fossilgeneratedemissions associated with the fuel’s production and transportation to the plant. Thisportion of the paper will discuss the overall GHG benefits of supplying and co-firing biomassalong with coal in select state of the art greenfield power applications with varying carboncapture technologies. Carbon capture technologies included in this examination are PulverizedCoal (PC) plants with amine-based post-combustion carbon capture, PC oxy-combustion andpre-combustion capture in Integrated Gasification Combined Cycle (IGCC) systems. Each planttype will have multiple combinations of biomass feed percentage and overall carbon capturepercentage.This paper will also discuss ways to reduce the power plant derate associated withincorporating CCS technology into existing plants. In this section it is proposed that the capacityderate associated with retrofitting a PC plant with CCS be overcome via the integration of asupplemental, low-carbon energy source. Here solar thermal energy is considered as a method toregenerate CO_2 capture solvents, thereby absolving a large portion of the parasitic penaltyassociated with the technology, and biomass combustion to supply the auxiliary steam and powerloads associated with amine-based CCS. For purposes of this study, monoethanol amine (MEA)was selected as the CO_2 capture solvent.The intent of this study is to determine the technical, economic and environmentalperformance of different power generation technologies when supplemented with low carbon,solar and biomass energy resources. The value of the renewable resource will be presented inthe context of its contribution to: plant efficiency, overall fuel usage, level of lifecycle GHG