On the Operation of CCS Within a Diverse Energy System

That CCS will be required to operate in a flexible and load following fashion in the diverse energy landscape of the 21st century is well recognised. However, what is less well understood is how these plants will be dispatched at the unit generator scale, and what effect this will have on the performance and behaviour of the plant at the individual unit operation level. To address this gap, we couple an investment and unit commitment energy system model with a detailed plant-level model of a super-critical coal-fired power station integrated with an amine-based post-combustion CO2 capture process. We provide insight into the likely role of coal and gas CCS plants in the UK’s energy system in the 2030s, 2040s and 2050s. We then evaluate the impact that this has on the performance of an individual coal CCS plant operating in this system, and chart its evolution throughout this period. Owing to the increased frequency and duration of part-load operation, asset utilisation and average efficiency suffer. This leads to a substantially increased LCOE. This reflects the growing inadequacy of this metric for evaluating CCS technology within a diverse energy landscape. Further, as a direct consequence of the dynamic operation, the interaction of the CCS plants with the downstream CO2 transport network is characterised by highly transient behaviour, including periods during which no CO2 is injected to the transport network, implying that the transport system must therefore be designed to incorporate this variability of supply

Ética e direito no pensamento de Henrique de Lima Vaz

Versa sobre a contribuição de Henrique de Lima Vaz para a compreensão das relações entre Ética e Direito, tendo em vista a problemática fundamental do pensamento vaziano e a interpretação das teorias jusnaturalistas do contrato social

What is the Value of CCS in the Future Energy System?

Ambitions to produce electricity at low, zero, or negative carbon emissions are shifting the priorities and appreciation for new types of power generating technologies. Maintaining the balance between security of energy supply, carbon reduction, and electricity system cost during the transition of the electricity system is challenging. Few technology valuation tools consider the presence and interdependency of these three aspects, and nor do they appreciate the difference between firm and intermittent power generation. In this contribution, we present the results of a thought experiment and mathematical model wherein we conduct a systems analyses on the effects of gas-fired power plants equipped with Carbon Capture and Storage (CCS) technology in comparison with onshore wind power plants as main decarbonisation technologies. We find that while wind capacity integration is in its early stages of deployment an economic decarbonisation strategy, it ultimately results in an infrastructurally inefficient system with a required ratio of installed capacity to peak demand of nearly 2.. Due to the intermittent nature of wind power generation, its deployment requires a significant amount of reserve capacity in the form of firm capacity. While the integration of CCS-equipped capacity increases total system cost significantly, this strategy is able to achieve truly low-carbon power generation at 0.04 tCO2/MWh. Via a simple example, this work elucidates how the changing system requirements necessitate a paradigm shift in the value perception of power generation technologies

Challenges and opportunities for the utilisation of ionic liquids as solvents for CO2 capture

Ionic Liquids have been extensively investigated as promising materials for several gas separation processes, including CO 2 capture. They have the potential to outperform traditional solvents, in terms of their capacity, selectivity, regenerability and stability. In fact, hundreds of ionic liquids have been investigated as potential sorbents for CO 2 capture. However, most studies focus on enhancing equilibrium capacity, and neglect to consider other properties, such as transport prop- erties, and hence ignore the effect that the overall set of properties have on process performance, and therefore on cost. In this study, we propose a new methodology for their evaluation using a range of monetised and non-monetised process performance indices. Our results demonstrate that whilst most research effort is focused on improving CO 2 solubility, viscosity, a transport prop- erty, and heat capacity, a thermochemical property, might preclude the use of ionic liquids, even those which are highly CO 2 -philic, and therefore increased effort on addressing the challenges associated with heat capacity and viscosity is an urgent necessity. This work highlights a range of potential challenges that ionic liquids will face before they can be applied at process scale, and identifies some key research opportunities

Can BECCS efficiently and sustainably remove CO2 from the atmosphere?

Bioenergy combined with carbon capture and storage, BECCS, could provide firm base load power while removing CO2 from the atmosphere. This unique feature makes it the predominant solution in the IPCC AR5 scenarios (IPCC, 2014) where it accounts for a substantial fraction of primary energy supply in half of the emissions pathways (Fuss et al., 2014). Such a demand for biomass would require large, integrated supply chains, whose embedded emissions could not only challenge the carbon negativity of BECCS – the underpinning concept of this option – but would also compete with other resources – such as water and land - already affected by global warming (UN Water, 2005). In this contribution, we present a whole-systems analysis of the biomass supply chain associated with a range of bioenergy materials – both energy dedicated crops (miscanthus, switchgrass, short rotation coppice willow), and agricultural residues (wheat straw) – supplied from different regions and land types, and converted in dedicated fired power stations in conjunction with post-combustion CCS technology. The water, carbon and energy footprints of each combination were calculated and their impact on the overall system net water intensity, power generation efficiency, and carbon intensity was measured. The model was evaluated with a range of values for each input parameter to capture the high variability and uncertainty in literature data. In order to describe the dynamic greenhouse gases (GHG) emissions of such as system, a yearly accounting of the emissions was carried out over a BECCS power plant lifetime, and the system carbon breakeven time was determined (Withers et al., 2015). Finally, a sensitivity analysis was carried out on the dynamic GHG emissions profile, and alternate scenarios involving organic chemicals, biofuels with and without CCS and carbon neutral electricity were investigated. Direct and indirect land use changes (Fargione et al., 2008; Plevin et al., 2010; Searchinger et al., 2008) effects were measured on both static and dynamic balances, and were found to be driving the results and uncertainty range. Overall we concluded that depending on conditions of its deployment, BECCS could lead to both carbon positive and negative balances. The most sustainable case study, miscanthus-based BECCS from Brazil, could lead to break-even times between 1 year if grown on marginal land, and 50 years on a forest land. Regulating and rewarding policies will have to integrate this local specificity in order to assure BECCS sustainable development. References Fargione, J., Hill, J., Tilman, D., Polasky, S., & Hawthorne, P. (2008). Land Clearing and the Biofuel Carbon Debt. Science, 319(February), 1235–1237. Fuss, S., Canadell, J. G., Peters, G. P., Tavoni, M., Andrew, R. M., Ciais, P., … Yamagata, Y. (2014). Betting on negative emissions. Nature Climate Change, 4(10), 850–853. IPCC. (2014). Climate Change 2014, Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Plevin, R. J., O’HARE, M., Jones, A. D., Torn, M. S., & Gibbs, H. K. (2010). The greenhouse gas emissions from indirect land use change are uncertain, but potentially much greater than previously estimated. Environmental Science & Technology., 44(21), 8015–8021. Searchinger, T., Heimlich, R., Houghton, R. A., Dong, F., Elobeid, A., Fabiosa, J., … Yu, T. (2008). Emissions from Land-Use Change. Science, 423(February), 1238–1241. UN Water. (2005). Coping with water scarcity: Challenge of the twenty-first century. Waterlines, 24(1), 28–29. https://doi.org/10.3362/0262-8104.2005.038 Withers, M. R., Malina, R., & Barrett, S. R. H. (2015). Carbon, climate, and economic breakeven times for biofuel from woody biomass from managed forests. Ecological Economics, 112, 45–52

Recognizing the value of collaboration in delivering carbon dioxide removal

In delivering the Paris climate target, bioenergy with carbon capture and storage (BECCS) is likely to play an important role, both as a climate mitigation and a carbon dioxide removal technology. However, regional drivers of BECCS sustainability and cost remain broadly unknown and the regional attribution of a global CO2 removal burden remains largely undetermined. This study explores the mechanisms behind cost-optimal BECCS deployment with evolving regional CO2 removal targets and energy sectors to provide insights into the ways in which different regional players will interact as a function of their bio-geophysical endowments and their ability to trade these assets. An important finding is that inter-regional cooperation—in choosing the right burden-sharing principle to establish regional targets—and collaboration—in trading negative emissions credits and biomass—are central to sustainably and affordably meeting these targets. This multilateralism in biomass and carbon credits trading constitutes important value creation opportunities for key providers of CO2 removal.The authors thank Imperial College London for the funding of a President's PhD Scholarship, as well as the Greenhouse Gas Removal (GGR) grant, funded by the Natural Environment Research Council (NERC), under grant NE/P019900/1. The authors also thank Solène Chiquier from Imperial College London for curating the CO2 storage capacity dataset

A novel methodological approach for achieving $/MWh cost reduction of CO2 capture and storage (CCS) processes

Carbon capture and storage is widely recognised as essential for the cost effective decarbonisation of the power and industrial sectors. However its capital and operating costs remain a barrier to deployment, with significant reduction in the cost per unit of decarbonised product considered vital. In the context of power generation, this is best expressed in terms of cost per MWh of electricity generated. To achieve a meaningful reduction in the cost of low carbon electricity, capital costs must also be reduced. Thus, this work presents a novel approach for identifying system improvements via a combination of process integration and intensification based on minimisation of thermodynamic losses. Application of this methodology to an oxy-combustion CCS process led to a 3% increase of net efficiency and a 13% reduction of £/MWh of electricity

Can BECCS Deliver Sustainable and Resource-efficient Negative Emissions?

Negative emissions technologies (NETs) in general and Bioenergy with CO2 Capture and Storage (BECCS) in particular are commonly regarded as vital yet controversial to meeting our climate goals. In this contribution we present a whole-systems analysis of the BECCS value chain associated with the cultivation, harvesting, transport and conversion in dedicated biomass power stations in conjunction with CCS, of a range of biomass resources – both dedicated energy crops (miscanthus, switchgrass, short rotation coppice willow), and agricultural residues (wheat straw). We explicitly consider the implications of sourcing the biomass from different regions, climates and land types. The water, carbon and energy footprints of each value chain were calculated, and their impact on the overall system water, carbon and power efficiencies were evaluated. An extensive literature review was performed and a statistical analysis of the available data is presented. In order to describe the dynamic greenhouse gas balance of such as system, a yearly accounting of the emissions was performed over the lifetime of a BECCS facility, and the carbon breakeven time (Withers et al., 2015) and lifetime net CO2 removal from the atmosphere were determined. The effects of direct and indirect land use change were included (Searchinger et al., 2008; Fargione et al., 2008; Plevin et al., 2010), and were found to be a key determinant of the viability of a BECCS project. Overall we conclude that, depending on the conditions of its deployment, BECCS could lead to both carbon positive and negative results. The total quantity of CO2 removed from the atmosphere over the project lifetime and the carbon breakeven time were observed to be highly case specific. This has profound implications for the policy frameworks required to incentivise and regulate the widespread deployment of BECCS technology. The results of a sensitivity analysis on the model combined with the investigation of alternate supply chain scenarios elucidated key levers to improve the sustainability of BECCS: 1) measuring and limiting the impacts of direct and indirect land use change, 2) using carbon neutral power and organic fertilizer, 3) minimising biomass transport, and prioritising sea over road transport, 4) maximising the use of carbon negative fuels, and, 5) exploiting alternative biomass processing options, e.g., natural drying or torrefaction. A key conclusion is that, regardless of the biomass and region studied, the sustainability of BECCS relies heavily on intelligent management of the supply chain. References Fargione, J., Hill, J., Tilman, D., Polasky, S., & Hawthorne, P. (2008). Land Clearing and the Biofuel Carbon Debt. Science, 319(February), 1235–1237. Plevin, R. J., O’HARE, M., Jones, A. D., Torn, M. S., & Gibbs, H. K. (2010). The greenhouse gas emissions from indirect land use change are uncertain, but potentially much greater than previously estimated. Environmental Science & Technology., 44(21), 8015–8021. Searchinger, T., Heimlich, R., Houghton, R. A., Dong, F., Elobeid, A., Fabiosa, J., … Yu, T. (2008). Emissions from Land-Use Change. Science, 423(February), 1238–1241. Withers, M. R., Malina, R., & Barrett, S. R. H. (2015). Carbon, climate, and economic breakeven times for biofuel from woody biomass from managed forests. Ecological Economics, 112, 45–52

Carbon capture from natural gas combined cycle power plants: Solvent performance comparison at an industrial scale

Natural gas is an important source of energy. This article addresses the problem of integrating an existing natural gas combined cycle (NGCC) power plant with a carbon capture process using various solvents. The power plant and capture process have mutual interactions in terms of the flue gas flow rate and composition vs. the extracted steam required for solvent regeneration. Therefore, evaluating solvent performance at a single (nominal) operating point is not indicative and solvent performance should be considered subject to the overall process operability and over a wide range of operating conditions. In the present research, a novel optimization framework was developed in which design and operation of the capture process are optimized simultaneously and their interactions with the upstream power plant are fully captured. The developed framework was applied for solvent comparison which demonstrated that GCCmax, a newly developed solvent, features superior performances compared to the monoethanolamine baseline solvent