Redefining power generation from carbonaceous fuels with carbonate looping combustion and gasification technologies

Following the Paris Climate Change Agreement, 197 countries, including the UK, are now obligated to reduce their anthropogenic greenhouse gas (GHG) emissions to hold the global mean temperature increase from pre-industrial levels well below 2 deg. C and pursuing efforts to limit it to 1.5 deg. C. Meeting this ambitious goal requires near-complete decarbonisation of the power sector, as it generates a third of the anthropogenic GHG emissions. To maintain its sustainability and international competitiveness, as well as to meet the environmental targets, the UK economy requires a secure supply of low-carbon electricity at an affordable cost. This is especially important in light of the forecast 30-60% increase in the peak electricity demand in the UK by 2050. Although the unabated conventional fossil fuel power systems are well-suited to flexibly meet the market demand, and thus to balance the intermittency of the renewable energy sources, they are heavy CO2 emitters.

As there are no other technologies that could significantly reduce emissions from conventional power generation from fossil fuel, which are expected to remain in the electricity mix for the foreseeable future, carbon capture and storage (CCS) is seen as crucial to decarbonising the power sector. Yet, the integration of the most mature technologies, such as oxy-combustion and chemical solvent scrubbing, to the conventional fossil fuel power plants is predicted to reduce their electric efficiency by 7-13% points. This corresponds to an increase in the electricity cost by at least 60%. Carbonate looping, which is based on the reversible carbonation reaction of CO2 with a metal oxide, is regarded as an emerging CO2 capture technology that can reduce the electric efficiency penalties to 5-8% points.

The main reason behind such improvement is the high-temperature operation (500-950 deg. C) of carbonate looping that enables high-grade heat recovery and a clean and efficient syngas generation. As this process can act as a standalone combustor or gasifier, carbonate looping combustion and gasification can be seen as an emerging class of technologies for thermochemical conversion of carbonaceous fuels whose feasibility, in conjunction with high-efficiency power cycles and/or solid oxide fuel cells, needs to be thoroughly evaluated. Following the results of the preliminary studies performed by the applicants and the developments in nuclear and solar power generation technologies, it is speculated that such novel power generation systems will have higher net thermal efficiency (>38%HHV), lower CO2 specific emissions (<100 gCO2/kWh) and affordable cost of electricity (30-60 £/kWh) compared to conventional fossil fuel power generation systems.

This proposal will employ the state-of-the-art engineering procedures to develop, and assess the feasibility of, novel power generation concepts based on the emerging carbonate looping process and high-efficiency power cycles, and/or fuel cells. These concepts will be identified through a design matrix generated during screening of carbonate looping cycles, power cycles and fuel cells. Then, the process models of the sub-systems included in the design matrix will be built using first principles and validated with data retrieved from the literature. Synthesis of novel power generation concepts will be conducted by employing the process wide approach to process modelling. The initial configurations of the concepts will be revised by employing the heat exchanger network and parametric analyses. The concepts will be then assessed in terms of thermodynamic, environmental and economic performance using both deterministic and probabilistic approach. In addition, the reliability, availability and maintainability assessment will be performed. Finally, the feasibility of the novel power generation concepts will be assessed and benchmarked against the conventional fossil fuel power plants in the multi-criteria analysis.

This project intends to inform the academic and industrial communities, as well as policy makers, electricity consumers, environmentalists and science, technology, engineering, math (STEM) students that the novel power generation systems using carbonaceous fuels are capable of ensuring the UK supply security and affordable electricity price in an environmentally-friendly manner beyond 2020. By developing novel power generation concepts, this research will provide the qualitative and quantitative evidence for high-efficiency low-emission utilisation of carbonaceous fuels in the future energy portfolio and will contribute towards wide deployment of new power generating capacity. It is expected that this project will bring benefits to UK industry, economy, environment and society.

Despite the associated costs, decarbonisation of the power generation systems by large-scale deployment of carbon capture and storage (CCS) is predicted to bring up to 15% reduction in the wholesale electricity prices in the UK by 2030, compared to a no CCS scenario. Importantly, to maintain a sustainable, resilient and internationally competitive economy in the UK, the future electricity supply security needs to be ensured and the electricity cost maintained at an affordable level, especially in light of the forecast 30-60% increase in the peak electricity demand by 2050 and the expected closure of 20% of the nuclear- and coal-based generation capacity in the UK over the coming decade. Therefore, by developing novel high-efficiency low-emission power generation systems, this research would bring further reductions to wholesale electricity prices and would contribute towards ensuring the security of the electricity supply. These benefits would be experienced by the UK economy, the companies in the power and industrial sectors, and electricity consumers.

The UK's pursuit of decarbonisation of the power sector is clearly reflected in 20% of the UK's electricity generation from renewable energy sources in 2014. Therefore, the power sector companies will benefit from new concepts for flexible power generation systems capable of balancing the intermittency of renewable capacity. The developed concepts could be also adapted to decarbonise other industries, benefiting companies in cement, lime, chemicals, hydrocarbon and steel industries. Moreover, by linking the techno-economic analysis with the probabilistic performance approach, and employing reliability, availability, maintainability and multi-criteria decision analyses for industrial practitioners will be informed how resilient the concepts are uncertainty in the operating and market conditions. These benefits will allow improving the UK economy competitiveness and will help ensure that the network, and thus the security of the electricity supply, is resilient to market variability in the mid- to long-term. Such findings could be also beneficial to the policy makers as they will learn about novel sustainable and resilient concepts for and their role in the future energy and industrial markets. This could impact their decisions regarding funding in, and support policy making surrounding, the power and industrial sectors decarbonisation. Moreover, know-how acquired in this project could lead to establishing a clean-tech company aiming at testing and commercialising the developed concepts.

Electricity consumers will learn about novel processes offering affordable cost of electricity, and environmentalists will learn that carbonaceous fuels can be utilised in a more environmentally-friendly manner ensuring sustainability and resilience of the future energy and industrial market. This research will also bring benefits to the STEM students by encouraging them to pursue a career in research and science. Through produced learning materials, the STEM students will understand the fundamentals behind clean power generation and various engineering methods employed in the development of novel processes.