Background

Gas-fired power generation currently accounts for around 20% of global electricity production capacity and in the past twenty years it has been a popular choice for new power generation capacity, particularly in many developed countries, due to its high efficiency, low installed costs and good reliability and flexibility. Interest in natural gas fired power generation has increased recently because of the increasing availability of natural gas from shale and greater concerns about nuclear power in some countries.

A switch from coal to gas can help to reduce emissions from power generation substantially but it is not a CO₂-free generation option. In the longer term it is likely that new gas fired power plants will be required to be built and operated with CO₂ capture and storage (CCS) technology to achieve deep reductions in emissions. Most of the work on CCS has so far concentrated on coal and relatively little information on the performance and costs of gas fired power plants with CCS has been published. IEAGHG has therefore commissioned Parsons Brinckerhoff to undertake this techno-economic study on CO₂ capture at natural gas fired power plants.

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Conclusions

• Adding post combustion capture reduces the thermal efficiency of a natural gas combined cycle plant by about 7-8 percentage points, increases the capital cost per kW by about 80-120% and increases the cost of base load electricity generation by about 30-40%.
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• The cost of CO₂ emission avoidance (i.e. the carbon emission cost required to give the same electricity cost from base load NGCC plants with and without CCS) is about €65/tonne in the lowest cost case evaluated in this study (post combustion capture with a proprietary solvent). The abatement cost compared to an alternative base line such as a coal fired plant may be lower.
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• Recycling part of the cooled flue gas to the gas turbine compressor inlet would increase the CO₂ concentration in the feed to the CO₂ capture unit, which could increase the thermal efficiency by up to 0.3 percentage points and reduce the cost of electricity by up to 8 percent.
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• Natural gas combined cycle plants with CCS may operate at annual capacity factors lower than base load, particularly in electricity systems that include large amounts of other low-CO₂ generation. In the lowest cost case, reducing the annual capacity factor to 50% would increase the cost of CO₂ avoidance to €87/tonne.
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• The study indicates that, based on current technology, pre-combustion capture in natural gas fired combined cycle power plants is not economically competitive with post combustion capture.

Recommendations

• This study could be extended to assess a combination of a high efficiency proprietary post combustion capture solvent and gas turbine flue gas recycle.

• The performance and costs of natural gas fired power plants with other CO₂ capture technologies such as other liquid solvents, solid sorbents or membranes should be evaluated if sufficient input data become available.

• Further work should be undertaken to assess the operation of gas fired power plants with CCS in future electricity systems that include large amounts of other low-CO₂ generation technologies.

• IEAGHG should undertake a new study to assess the performance and costs of baseline coal fired power plants with CO₂ capture.