In the past two years, six major Carbon Capture Storage (CCS) projects in the UK have been shelved.
Its potential for carbon emission reductions within carbon-intensive industries like steel and cement is now being lost due to a lack of action, writes Dr Dawid Hanak, assistant professor in clean energy, Cranfield University.
The problems are rooted in the bald figures used on performance. And these can be misleading. Standard calculations being referred to claim an efficiency penalty of at least 7% points compared with conventional power plants without CCS, increasing the cost of electricity by at least 60%. Unfair comparisons are then being made with renewable power generation when the actual whole-life cost of moving to renewables isn’t being taken into account.
We are in a critical transition phase between ‘black’ and ‘green’ technologies. To get to the low-carbon world we all need to be part of, there has to be realism about the practicalities involved. What’s needed is more sophisticated assessments of feasibility in order for more clear-sighted decisions to be made on CCS, and its role in decarbonising economies in the transition to 100% renewable energy generation.
It’s a fantasy that the UK, as well as many other nations, can avoid carbon emissions in the near term. While decommissioning coal-fired power stations has made an instant impact on CO2 figures, other future emissions reductions will be much more difficult to achieve without CCS.
CCS is also critical for the transition period while we deal with the major problems associated with the basic intermittency of most renewable options: the need for large-scale battery storage in particular, for which there are no current solutions. Renewables are the future, but we need to find practical, sustainable ways to get there first.
CCS technologies are becoming more sophisticated, with enhanced forms of calcium looping in particular having the potential to reduce the efficiency penalties. Calcium looping is a process where carbon dioxide can be separated from other gases – and so captured and stored away – through reversible reaction with metal oxides, such as lime, to form metal carbonates.
Work at Cranfield has identified opportunities for using new methods that improve a less effective aspect of calcium looping, the need for both high-purity oxygen production to support regeneration of the sorbent at high temperature and for efficient heat utilisation, by using indirectly heated reactors and an advanced supercritical CO2 power cycle.
Yet the data supporting the commercial viability of calcium looping at an industrial scale is still not sufficient to drive further development and adoption. So other high-potential CCS methods, like new forms of calcium looping, have become overlooked and more time is lost.
Our work at Cranfield has looked at developing an evidence base for governments and industry that will support commercial deployment of CCS. We have developed new concepts for power generation systems based on calcium looping combustion process and evaluated their economic performance using commercial tools.
We believe this will not only provide more accurate and reliable data, but will also directly speak to decision makers and will support further investment in CCS. In contrast to levelised cost of electricity, which is commonly used in the CCS community, we have employed the net present value approach that, in addition to the investment costs, also takes into account the scale factor of equipment, taxes, interest and depreciation, so cash flows during construction and operation years of the power generation system.
Moreover, we have derived correlations for the capital costs for each piece of equipment that allow for a bottom-up cost estimation that is closer to the industrial practice.
To identify the benefits of new power generation concepts based on calcium looping combustion process, we have compared their key performance indicators, such as the break-even electricity price and the efficiency penalty, with a conventional coal-fired power plant without CCS and more mature CCS technologies.
Our analysis confirmed that a more mature CCS technology, the established approach of amine scrubbing results in an efficiency penalty of 9.4% points when retrofitted to a coal-fired power plant; the penalty in terms of electricity price is €36.80 per Megawatt generated per hour (MWh), assuming there is no carbon tax.
Comparatively, the new calcium looping combustion process with advanced supercritical CO2 power cycle shows no efficiency penalty with an electricity price penalty of around 11.5 €/MWh. Importantly, we estimated that the lowest cost of CO2 avoided, which corresponds to the minimum market value of carbon tax at which there will be no electricity price penalty associated with CCS, for the new calcium looping combustion process will be 16.3 € per tonne of CO2.
As this is below the current market values of carbon tax of 18–25 €/tCO2, our analysis confirms that there are economic incentives for the government and industry to implement CCS at a scale.
This is in addition to the environmental benefits. While a coal-fired station pours out more than 796 kg of CO2 for every MWh, this is reduced dramatically to around 91.5 kg/MWh, allowing the energy industry and other sectors to work more effectively to hitting carbon emission reduction targets.
Overall, our work at Cranfield has shown how some of the emerging CCS technologies can reduce carbon capture costs compared with more traditional methods by more than 25% – transforming the picture in terms of the economic viability of using CCS.