1. Background and objectives of the study

Power plants built in the 1990’s and early years of the new millennium have been typically designed for base load operation, favouring higher efficiency and lower capital costs, with the main objective of minimizing the cost of electricity production. Nowadays, existing and new power plants must face the challenges of the liberalized electricity market and the requirement to cover intermediate and peak load constraints, so to respond to the daily and seasonal variation of the electricity demand. In this scenario, not only conventional natural gas combined cycles must be designed for flexible operation, but also coal-fired power plants, which are now generally required to operate in the mid merit market.

With this premise, IEA Greenhouse Gas R&D Programme has contracted Foster Wheeler (FW) to perform a study that assesses the potential flexibility of power plants with Carbon Capture and Storage (CCS). Most studies undertaken by several companies so far have assumed that these plant types will operate at base load in the near future, but it is now clear that they will need to be able to respond to the requirements of the new liberalized electricity market, otherwise it will not be possible to meet overall greenhouse gas abatement targets.

The main objectives of this study have been the following:

  • Outline current capabilities of conventional coal and natural gas fired power plants, without CCS, to operate flexibly in response to the demand of the electricity market.
  • Make a review of the information, available in the public domain, on the flexibility of the same power plants with carbon capture and storage for three leading capture technologies: pre, post and oxy-combustion.
  • Identify factors that may constrain the operating flexibility of CCS processes, possible ways of overcoming these constraints and related cost implications.
  • Make a techno-economic review of alternative energy storage techniques, like pumped hydropower, compressed air and batteries.

IEA GHG R&P Programme has already issued in the past years reports assessing natural gas and coal based power plants with leading CCS technologies, which have been considered as reference plants for the considerations of this work. Most of the information for the reference plants has been derived from the IEA GHG report “Water usage and loss Analysis in Power plants without and with CO2 capture”, completed by Foster Wheeler in 2010. Remaining information, relevant to the post-combustion capture process from natural gas-fuelled combined cycles, are partially taken from FW in-house design and partially from the IEA Report PH4/33, Nov 2004, Improvement in Power generation with post Combustion capture of CO2.

FW like to acknowledge the following companies, listed in alphabetical order, for their fruitful support to the preparation of the report:

  • Aker Clean Carbon;
  • Alstom;
  • Mitsubishi Heavy Industries (MHI);
  • UOP.