Hannah Chalmers

Flexible Operation of Coal Fired Power Plants with Postcombustion Capture of Carbon Dioxide

Carbon capture and storage is one family of technologies that could be used to significantly reduce global carbon dioxide (C O2 ) emissions. This paper reviews the likely flexibility of power plants with postcombustion capture, with a focus on an improved characterization of the dynamic performance of power plants with C O2 capture. The literature has focused on design and optimization for steady state operation of power plants with capture, often at a single design point. When dynamic behavior is considered, it is possible that designs should be altered for best overall plant performance. Economic trade-offs between improving transport and storage scheme flexibility and constraining power plant operations should also be carefully analyzed, particularly if the captured C O2 is to be used in another process such as enhanced oil recovery. Another important aspect of real plant operation will be adhering to legislative requirements. Further work is required to identify mechanisms that allow flexible operatio...

Comparing post-combustion CO2 capture operation at retrofitted coal-fired power plants in the Texas and Great Britain electric grids

This work analyses the carbon dioxide (CO2) capture system operation within the Electric Reliability Council of Texas (ERCOT) and Great Britain (GB) electric grids using a previously developed first-order hourly electricity dispatch and pricing model. The grids are compared in their 2006 configuration with the addition of coal-based CO2 capture retrofits and emissions penalties from 0 to 100 US dollars per metric ton of CO2 (USD/tCO2). CO2 capture flexibility is investigated by comparing inflexible CO2 capture systems to flexible ones that can choose between full- and zero-load CO2 capture depending on which operating mode has lower costs or higher profits. Comparing these two grids is interesting because they have similar installed capacity and peak demand, and both are isolated electricity systems with competitive wholesale electricity markets. However, differences in capacity mix, demand patterns, and fuel markets produce diverging behaviours of CO2 capture at coal-fired power plants. Coal-fired facilities are primarily base load in ERCOT for a large range of CO2 prices but are comparably later in the dispatch order in GB and consequently often supply intermediate load. As a result, the ability to capture CO2 is more important for ensuring dispatch of coal-fired facilities in GB than in ERCOT when CO2 prices are high. In GB, higher overall coal prices mean that CO2 prices must be slightly higher than in ERCOT before the emissions savings of CO2 capture offset capture energy costs. However, once CO2 capture is economical, operating CO2 capture on half the coal fleet in each grid achieves greater emissions reductions in GB because the total coal-based capacity is 6 GW greater than in ERCOT. The market characteristics studied suggest greater opportunity for flexible CO2 capture to improve operating profits in ERCOT, but profit improvements can be offset by a flexibility cost penalty.

Carbon capture and storage deployment in the UK: What next after the UK Government's competition?

Abstract In November 2007, the UK Government set the direction for initial commercial-scale demonstration of carbon capture and storage (CCS) in the UK. It announced the rules for a competition to identify a demonstration of post-combustion capture project at a pulverized coal power plant, linked to a full chain of CCS, including carbon dioxide transport to an offshore storage site. Because there are several options for further demonstration and initial deployment projects to build on this initial effort, the UK Government will need to decide its priorities for CCS deployment. Regardless of the route, a successful transition to widespread use of CCS would have to overcome significant technical, commercial, regulatory, and political challenges. This article considers the significance of understanding and using lessons learned from previous major UK energy sector transitions to manage the development, demonstration, and deployment of CCS. The past transitions considered here are not perfect analogies, but they do suggest a range of potential futures for CCS deployment in the UK. They also provide insights into possible drivers and triggers for deployment and the general business environment required for a successful transition to widespread commercial use of CCS in the UK.

Valuing power plant flexibility with CCS: the case of post-combustion capture retrofits

An important development in recent years has been increased interest in retrofitting CO2 capture at existing power plants. In parallel, it has also been suggested that flexible operation of power plants with CO2 capture could be important in at least some jurisdictions. It is likely that retrofitted power plants could have significant ‘built-in’ flexibility, but this potential is often not considered in studies of the economic performance of power plants with CO2 capture. This paper makes a contribution to filling this gap by developing methods for first order screening analysis of flexible operation of power plants with CO2 capture and applying them to the case study example of an appropriately integrated retrofit of post-combustion capture at a coal-fired power plant. The quantitative analysis suggests that rich solvent storage could be an attractive option on a short-run basis for some fuel, CO2 and electricity price combinations. Results from first order analysis can then be used to determine which operating modes should (and shouldn’t) be included in further, more detailed design studies.

Retrofitting CO2 capture-ready fossil plants with post-combustion capture: Part 2 – Requirements for natural gas combined cycle plants using solvent-based flue gas scrubbing

Abstract A number of natural gas combined cycle (NGCC) power stations recently permitted in the UK have been required to be CO2 capture ready so that carbon capture and storage can be retrofitted once it is commercially viable (or legally required). Several options for future CO2 capture from NGCC units can be envisaged including post-combustion capture technology using flue gas scrubbing with aqueous solvents. When an NGCC plant is designed to be ready for a retrofit with post-combustion capture, one of the most important technical considerations is the steam extraction pressure and flow to provide the energy necessary for solvent regeneration. This is determined by the choice of solvent used, but new solvents are being developed and the exact future requirements, in perhaps 10–20 years time, cannot be predicted. Ways in which designs for the steam cycle of NGCC plants can cope with this challenge are presented. Several alternatives to mitigate the loss of power output of NGCC plants retrofitted with post-combustion capture and to achieve improved plant flexibility are also assessed and compared.

Carbon capture and storage: the ten year challenge

Abstract Carbon capture and storage (CCS) could play a significant role in reducing global CO2 emissions. It has the unique characteristic of keeping fossil carbon in the ground by allowing fossil fuels to be used, but with the CO2 produced being safely stored in a geological formation. Initial versions of the key component technologies are at a sufficient level of maturity to build integrated commercial-scale demonstration plants. If CCS is to reach its full potential to contribute to global efforts to mitigate the risk of dangerous climate change, it is urgent that a number of actions begin now in order to be ready for CCS deployment from around 2020 using proven designs that can be built in large numbers. This article discusses some key challenges for CCS, with a focus on development in the next decade, highlighting the potential benefits of a two tranche programme for integrated commercial-scale demonstration to develop proven reference plant designs and reviewing the importance of distinguishing between different classes of CCS according to their ability to significantly reduce CO2 emissions associated with fossil fuel use. It also identifies some ongoing CCS projects and initiatives and examines some possible implications of current policy discussions for technology development.

Operational Flexibility of Future Generation Portfolios Using High Spatial- and Temporal-Resolution Wind Data

Increasing amounts of variable renewable energy sources will cause fundamental and structural changes to thermal power plant operating regimes. Maintaining key reserve requirements will lead to an increase in power plant start-ups and cycling operations for some units. An enhanced unit commitment model with energy storage and flexible CO2 capture is formulated. High-resolution on-/offshore wind data for the U.K., and probabilistic wind power forecast, model wind imbalances at operational timescales. The strategic use of flexible CO2 capture and energy storage helps maintain reserve levels, decreasing power plant cycling operations and wind curtailment. A temporally explicit variability assessment of net demand illustrates the generation flexibility requirements and the nonlinear impacts of increasing wind capacity on power plant operating regimes.

Carbon capture and storage: More energy or less carbon?

Innovations in energy supply have traditionally been valued because they make more energy available than would otherwise be the case and/or make it available at lower cost. Carbon capture and storage (CCS) can also be viewed in this way to some extent, for example, as a means to keep coal as an electricity generation fuel in Europe and the USA. But the underlying driver for CCS is really that less fossil carbon is being emitted to the atmosphere. Since long-term cumulative emissions are the determining factor for climate change, long-term retention of stored CO2 is important. Long-term “leakage” risks also apply, however, to fossil fuels that are displaced in the short term by nonfossil energy sources (i.e., nuclear, renewables) since the fossil fuels may subsequently be used and the CO2 released to the atmosphere. If CCS is to achieve effective reductions in CO2 emissions to the atmosphere, however, it is important that projects are either near carbon-neutral, able to capture around 90% or more of the fo...

Retrofitting CO2 Capture to Existing Power Plants as a Fast Track Mitigation Strategy

Carbon capture and storage (CCS) is often identified as an important technology for mitigating global carbon dioxide (CO2 ) emissions. For example, the IEA currently suggests that 160GW of CCS may need to be installed globally by 2030 as part of action to limit greenhouse gas concentrations to 550ppm-CO2 eq, with a further 190GW CCS capacity required if a 450ppm-CO2 eq target is to be achieved. Since global rollout of proven CCS technologies is not expected to commence until 2020 at the earliest this represents a very challenging build rate. In these circumstances retrofitting CO2 capture to existing plants, probably particularly post-combustion capture on pulverized coal-fired plants, could play an important role in the deployment of CCS as a global strategy for implementing CO2 emissions reductions. Retrofitting obviously reduces the construction activity required for CCS deployment, since fewer additional new power plants are required. Retrofitting CCS to an existing fleet is also an effective way to significantly reduce CO2 emissions from this sector of the electricity generation mix; it is obviously not possible to effect an absolute reduction in coal power sector CO2 emissions simply by adding new plants with CCS to the existing fleet. Although it has been proposed that plants constructed now and in the future can be ‘capture ready’, much of the existing fleet will not have been designed to be suitable for retrofit of CO2 capture. Some particular challenges that may be faced by utilities and investors considering a retrofit project are discussed. Since it is expected that post-combustion capture retrofits to pulverized coal plants will be the most widely applied option for retrofit to the existing fleet (probably regardless of whether base plants were designed to be capture ready or not), a review of the technical and potential economic performance of this option is presented. Power cycle performance penalties when capture is retrofitted need to be addressed, but satisfactory options appear to exist. It also seems likely that the economic performance of post-combustion capture retrofit could be competitive when compared to other options requiring more significant capital expenditure. Further work is, however, required both to develop a generally accepted methodology for assessing retrofit economics (including consideration of the implications of lost output after retrofit under different electricity selling price assumptions) and to apply general technical principles to case studies where site-specific constraints are considered in detail. The overall conclusion from the screening-level analysis reported in this paper is that, depending on project-specific and market-specific conditions, retrofit could be an attractive option, especially for fast track initial demonstration and deployment of CCS. Any unnecessary regulatory or funding barriers to retrofit of existing plants and to their effective operation with CCS should, therefore, be avoided.Copyright

Chapter 2:Fossil Power Generation with Carbon Capture and Storage (CCS): Policy Development for Technology Deployment

In recent years, there has been growing concern that carbon dioxide (and other greenhouse gas) emissions from fossil fuel use could cause dangerous climate change, with serious negative impacts on human activities.1,2 In this context, it is expected that the net CO2 emissions from fossil fuels must ...