Publications
163 results found
Daggash H, Heuberger C, Mac Dowell N, 2019, The role and value of negative emissions technologies in decarbonising the UK energy system, International Journal of Greenhouse Gas Control, Vol: 81, Pages: 181-198, ISSN: 1750-5836
The UK is committed to the Paris Agreement and has a legally-binding target to reduce economy-wide greenhouse gas emissions by 80% relative to 1990 levels by 2050. Meeting these targets would require deep decarbonisation, including the deployment of negative emissions technologies. This study, via a power supply capacity expansion model, investigates the potential role of bio-energy with carbon capture and storage (BECCS) and direct air capture and storage (DACS) in meeting the UK's emissions reduction targets. We show that to achieve power sector decarbonisation, a system dominated by firm and dispatchable low-carbon generators with BECCS or DACS to compensate for their associated emissions is significantly cheaper than a system dominated by intermittent renewables and energy storage. By offsetting CO2 emissions from cheaper thermal plants, thereby allowing for their continued utilisation in a carbon-constrained electricity system, BECCS and DACS can reduce the cost of decarbonisation by 37–48%. Allowing some this value transferred to accrue to NETs offers a potential route for their commercial deployment.
Harraz AA, Freeman J, Wang K, et al., 2019, Diffusion-absorption refrigeration cycle simulations in gPROMS using SAFT-γ Mie, Energy Procedia, Vol: 158, Pages: 2360-2365, ISSN: 1876-6102
Diffusion-absorption refrigeration (DAR) is a clean thermally-powered refrigeration technology that can readily be activated by low- to medium-grade renewable heat. There is an ongoing interest in identifying or designing new working fluids for performance improvement, particularly in solar applications with non-concentrating solar collectors providing heat at temperatures < 150 °C. In this work, the state-of-the-art statistical associating fluid theory (SAFT) is adopted for predicting the thermodynamic properties of suitable DAR working fluids. A first-law thermodynamic analysis is performed in the software environment gPROMS for a DAR cycle using ammonia as the refrigerant, water as the absorbent and hydrogen as the auxiliary gas. The simulation results show good agreement with experimental data generated in a prototype DAR system with a nominal cooling capacity of 100 W. In particular, at a charge pressure of 17 bar and when delivering cooling at 5 °C, the model results agree with experimental COP data to within ± 7 % over a range of heat inputs from 150 to 500 W. The maximum coefficient of performance (COP) is estimated to be 0.24 at a heat input of 250 W. The group-contribution SAFT-γ Mie equation of state is of particular interest as it offers good agreement with experimental data and provides flexibility in extending the model to test different working fluids with a high degree of fidelity. A methodology is also presented that allows the DAR thermodynamic analysis and working-fluid modelling to be integrated into a more general technology optimisation framework.
Harraz AA, Najjaran A, Sacks R, et al., 2019, Experimentally validated simulations of a diffusion absorption refrigeration system, Pages: 1045-1056
Diffusion absorption refrigeration (DAR) is a small-scale, thermally-driven cooling technology that operates passively without the need for mechanical or electrical inputs. Due to the lack of a compressor, DAR systems are charged with an auxiliary gas to enable single-pressure operation. Although DAR units have a simple construction and are easy to operate, their modelling presents challenges arising from the complexity of the physical processes that take place and govern operation. Few experimentally validated models offer a reliable prediction of the DAR system performance over a wide range of operating conditions. This paper combines results from experimental investigations on a laboratory-scale ammonia-water-hydrogen DAR system with a nominal cooling output of ∼100 W with model predictions of the performance characteristics of this system. In previous work, the DAR cycle was modelled using first-law thermodynamic analysis in the gPROMS environment for a single cooling delivery temperature and a single-charge pressure, using a group-contribution equation-of-state based on the statistical associating fluid theory (SAFT). Here, extended model validation is performed to investigate the effect of key operating parameters on system performance, including the generator heat input (varied from 150 W to 700 W), the cooling delivery temperature (set to two levels: 5 ◦C and 23 ◦C) and the system charge pressure (18 bar and 21 bar). The measured coefficient of performance (COP) was between 0.02 and 0.29. The present model predicts the maximum COP well over the heat-input range from 250 W to 550 W. Hence, the model shows good agreement with experiments, particularly when the heat-input rate is at or below the system’s design-point. Conclusions are drawn concerning the ability of models to predict this complex technology, with emphasis on part-load and off-design operation which is crucial, e.g., in solar applications.
Al-Saqlawi J, Madani K, Mac Dowell N, 2018, Techno-economic feasibility of grid-independent residential roof-top solar PV systems in Muscat, Oman, Energy Conversion and Management, Vol: 178, Pages: 322-334, ISSN: 0196-8904
Oman is a country characterised by high solar availability, yet very little electricity is produced using solar energy. As the residential sector is the largest consumer of electricity in Oman, we develop a novel approach, using houses in Muscat as a case study, to assess the potential of implementing roof-top solar PV/battery technologies, that operate without recourse to the electricity grid. Such systems target the complete decarbonisation of electricity demand per household and are defined in this study as grid-independent systems. The approach adopted starts with a technical assessment of grid-independent systems that evaluates the characteristics of the solar panel and the battery facility required to provide grid-independence. This is then compared to a similar grid-connected system and any techno-economic targets necessary to enhance the feasibility of residential roof-top PV systems in Muscat are identified. Such an analysis was achieved through developing a detailed techno-economic mathematical model describing four sub-systems; the solar panel DC source, the grid-independent sub-system, the grid-connected sub-system and the economic sub-system. The model was implemented in gPROMS and uses real hourly weather and climate conditions matched with real demand data, over a simulated period of 20 years. The results indicate that, in the context of the system studied, grid-independent PV systems are not feasible. However, combined with a sufficiently high electricity price, grid-independent systems can become economically feasible only with significant reductions in battery costs (>90% reductions).
Bui M, Tait P, Lucquiaud M, et al., 2018, Dynamic operation and modelling of amine-based CO2 capture at pilot scale, International Journal of Greenhouse Gas Control, Vol: 79, Pages: 134-153, ISSN: 1750-5836
This study combines pilot plant experiments and dynamic modelling to gain insight into the interaction between key process parameters in producing the dynamic response of an amine-based CO2 capture process. Three dynamic scenarios from the UKCCSRC PACT pilot plant are presented: (i) partial load stripping, (ii) capture plant ramping, and (iii) reboiler decoupling. These scenarios are representative of realistic flexible operation of non-baseload CCS power stations. Experimental plant data was used to validate a dynamic model developed in gCCS. In the capture plant ramping scenario, increased liquid-to-gas (L/G) ratio resulted in higher CO2 capture rate. The partial load stripping scenario demonstrated that the hot water flow directly affects reboiler temperature, which in turn, has an impact on the solvent lean loading and CO2 capture rate. The reboiler decoupling scenario demonstrates a similar relationship. Turning off the heat supply to the reboiler leads to a gradual decline in reboiler temperature, which increases solvent lean loading and reduces CO2 capture rate. The absorber column temperature profile is influenced by the degree of CO2 capture. For scenarios that result in lower solvent lean loading, the absorber temperature profile shifts to higher temperature (due to the higher CO2 capture rate).
Budinis S, Krevor S, Mac Dowell N, et al., 2018, An assessment of CCS costs, barriers and potential, Energy Strategy Reviews, Vol: 22, Pages: 61-81, ISSN: 2211-467X
© 2018 Elsevier Ltd Global decarbonisation scenarios include Carbon Capture and Storage (CCS) as a key technology to reduce carbon dioxide (CO2) emissions from the power and industrial sectors. However, few large scale CCS plants are operating worldwide. This mismatch between expectations and reality is caused by a series of barriers which are preventing this technology from being adopted more widely. The goal of this paper is to identify and review the barriers to CCS development, with a focus on recent cost estimates, and to assess the potential of CCS to enable access to fossil fuels without causing dangerous levels of climate change. The result of the review shows that no CCS barriers are exclusively technical, with CCS cost being the most significant hurdle in the short to medium term. In the long term, CCS is found to be very cost effective when compared with other mitigation options. Cost estimates exhibit a high range, which depends on process type, separation technology, CO2transport technique and storage site. CCS potential has been quantified by comparing the amount of fossil fuels that could be used globally with and without CCS. In modelled energy system transition pathways that limit global warming to less than 2 °C, scenarios without CCS result in 26% of fossil fuel reserves being consumed by 2050, against 37% being consumed when CCS is available. However, by 2100, the scenarios without CCS have only consumed slightly more fossil fuel reserves (33%), whereas scenarios with CCS available end up consuming 65% of reserves. It was also shown that the residual emissions from CCS facilities is the key factor limiting long term uptake, rather than cost. Overall, the results show that worldwide CCS adoption will be critical if fossil fuel reserves are to continue to be substantively accessed whilst still meeting climate targets.
Fajardy M, Chiquier S, Mac Dowell N, 2018, Investigating the BECCS resource nexus: delivering sustainable negative emissions, Energy and Environmental Science, Vol: 11, Pages: 3408-3430, ISSN: 1754-5692
Bioenergy with carbon capture and storage (BECCS), and other negative emissions technologies (NETs), are integral to all scenarios consistent with meeting global climate ambitions. BECCS's ability to promptly remove CO2 from the atmosphere in a resource efficient manner, whilst being a net energy generator to the global economy, remains controversial. Given the large range of potential outcomes, it is crucial to understand how, if at all, this technology can be deployed in a way which minimises its impact on natural resources and ecosystems, while maximising both carbon removal and power generation. In this study, we present a series of thought experiments, using the Modelling and Optimisation of Negative Emissions Technologies (MONET) framework, to provide insight into the combinations of biomass feedstock, origin, land type, and transport route, to meet a given CO2 removal target. The optimal structure of an international BECCS supply chain was found to vary both quantitatively and qualitatively as the focus shifted from conserving water, land or biomass, to maximising energy generated, with the water use in particular increasing threefold in the land and biomass use minimisation scenario, as compared to the water minimisation scenario. In meeting regional targets, imported biomass was consistently chosen over indigenous biomass in the land and water minimisation scenarios, confirming the dominance of factors such as yield, electricity grid carbon intensity, and precipitation, over transport distance. A pareto-front analysis was performed and, in addition to highlighting the strong trade-offs between BECCS resource efficiency objectives, indicated the potential for tipping points. An analysis of the sensitivity to the availability of marginal land and agricultural residues showed that (1) the availability of agricultural residues had a great impact on BECCS land, and that (2) water use and land use change, two critical sustainability indicators for BECCS, were neg
Iruretagoyena Ferrer D, Sunny N, Chadwick D, et al., 2018, Towards a low carbon economy via sorption enhanced water gas shift and alcohol reforming
Najjaran Kheirabadi A, Harraz AA, Freeman J, et al., 2018, Numerical and experimental investigations of diffusion absorption refrigeration systems for use with low temperature heat sources, ECOS 2018 - 31st International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, Publisher: ECOS
he diffusion absorption refrigeration (DAR) cycle is a technology of increasing interest thanks to its suitabilityfor providing cooling from a thermal energyinputin a range of applications. Itcan bedistinguished from other absorption refrigeration cycles by its employment of a thermally-driven bubble pump to circulate the working fluid, which gives it anability to operate entirely off-gridwithout an electricity input. In this work,we present results from an experimentalcampaign aimed atcharacterisingthe performance of aprototypeammonia-water-hydrogen DAR system with a nominal cooling capacity of 100 W,over a range of operating conditions, specifically with a view ofadaptingthe system for use in low-temperature applications. In the experiments, the heat input to the DAR generator is provided over a range of temperatures from175to215°Cby using electrical cartridge heaters. The system is charged to 22 bar, and the ammonia mass concentration of the working fluid mixture is 30%. The resulting coefficient of performance (COP) of the system is measured in the range 0.12to 0.26. A new methodology for the selection of optimal working-fluid mixtures using the state-of-the-art, statistical associating fluid theory (SAFT) approach implemented within the process modelling software gPROMS®is also presented. The experimental results will be used for futurevalidation of a thermodynamic model of the cycle. Finally,the performance of the system in a solar application is investigated, with a thermal inputprovided by an array of evacuated tube heat pipe solar collectors. The system pressure and condensation temperature are found to be key factors in determining the performance of solar-DAR systems.
Heuberger CF, Rubin ES, Staffell L, et al., 2018, Power capacity expansion planning considering endogenous technology cost learning (vol 204, pg 831, 2017), APPLIED ENERGY, Vol: 220, Pages: 974-974, ISSN: 0306-2619
Mac Dowell N, Hallett JP, 2018, Challenges and opportunities for the utilisation of ionic liquids as solvents for CO2 capture, Molecular Systems Design & Engineering, Vol: 3, Pages: 560-571, ISSN: 2058-9689
Ionic Liquids have been extensively investigated as promising materials for several gas separationprocesses, including CO2capture. They have the potential to outperform traditional solvents, interms of their capacity, selectivity, regenerability and stability. In fact, hundreds of ionic liquidshave been investigated as potential sorbents for CO2capture. However, most studies focus onenhancing 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 arange of monetised and non-monetised process performance indices. Our results demonstratethat whilst most research effort is focused on improving CO2solubility, viscosity, a transport prop-erty, and heat capacity, a thermochemical property, might preclude the use of ionic liquids, eventhose which are highly CO2-philic, and therefore increased effort on addressing the challengesassociated with heat capacity and viscosity is an urgent necessity. This work highlights a rangeof potential challenges that ionic liquids will face before they can be applied at process scale, andidentifies some key research opportunities.
Daggash HA, Patzschke CF, Heuberger CF, et al., 2018, Closing the carbon cycle to maximise climate change mitigation: Power-to-Methanol vs Power-to-Direct Air Capture, Sustainable Energy and Fuels, Vol: 2, Pages: 1153-1169, ISSN: 2398-4902
It is broadly recognised that CO2 capture and storage (CCS) and associated negative emissions technologies (NETs) are vital to meeting the Paris agreement target. The hitherto failure to deploy CCS on the required scale has led to the search for options to improve its economic return. CO2 capture and utilisation (CCU) has been proposed as an opportunity to generate value from waste CO2 emissions and improve the economic viability of CCS, with the suggestion of using curtailed renewable energy as a core component of this strategy. This study sets out to quantify (a) the amount of curtailed renewable energy that is likely to be available in the coming decades, (b) the amount of fossil CO2 emissions which can be avoided by using this curtailed energy to convert CO2 to methanol for use as a transport fuel – power-to-fuel, with the counterfactual of using that curtailed energy to directly remove CO2 from the atmosphere via direct air capture (DAC) and subsequent underground storage, power-to-DAC. In 2015, the UK curtailed 1277 GWh of renewable power, or 1.5% of total renewable power generated. Our analysis shows that the level of curtailed energy is unlikely to increase beyond 2.5% until renewable power accounts for more than 50% of total installed capacity. This is unlikely to be the case in the UK before 2035. It was found that: (1) power-to-DAC could achieve 0.23–0.67 tCO2 avoided MWh−1 of curtailed power, and (2) power-to-Fuel could achieve 0.13 tCO2 avoided MWh−1. The power-to-fuel concept was estimated to cost $209 tCO2 avoided−1 in addition to requiring an additional $430–660 tCO2 avoided−1 to finally close the carbon cycle by air capture. The power-to-DAC concept was found to cost only the $430–660 tCO2 avoided−1 for air capture. For power-to-fuel to become profitable, hydrogen prices would need to be less than or equal to $1635 tH2−1 or methanol prices must increase to $960 tMeOH−1. Absent this ch
Fajardy M, Mac Dowell N, 2018, The energy return on investment of BECCS: is BECCS a threat to energy security?, Energy and Environmental Science, Vol: 11, Pages: 1581-1594, ISSN: 1754-5692
Compliance with long term climate targets whilst maintaining energy security is understood to relyheavily on the large-scale deployment of negative emissions technologies (NETs). One option,Bioenergy with Carbon Capture and Storage (BECCS) is prominent in Integrated AssessmentModels (IAMs), with projected annual contributions of 8 – 16.5 GtCO2/yr of atmospheric carbondioxide removal whilst contributing 150 – 300 EJ/yr, or 14 to 20% of global primary energy supply,in 2100. Implicit in these scenarios is the assumption that BECCS is a net producer of energy.However, relatively energy intensive biomass supply chains and low power generation efficiencycould challenge this ubiquitous assumption. Deploying an energy negative technology at thisscale could thus represent a threat to energy security. In this contribution, we evaluate the energyreturn on investment (EROI) of an archetypal BECCS facility. In order to highlight the importanceof biomass sourcing, two feedstock scenarios are considered: use of domestic biomass pellets(UK) and import of biomass pellets from Louisiana, USA. We use the Modelling and Optimisationof Negative Emissions Technologies (MONET) framework to explicitly account for growing, pre-treating, transporting and converting the feedstock in a 500 MW BECCS facility. As an example,we illustrate how the net electricity balance (NElB) of a UK-based BECCS facility can be eitherpositive or negative, as a function of supply chain decisions. Power plant efficiency, fuel efficiencyfor transport, transport distance, moisture content, drying method, as well as yield were identifiedas key factors that need to be carefully managed to maximise BECCS net electricity balance. Akey insight of this contribution is that, given an annual carbon removal target, increasing BECCS’power generation efficiency by using a more advanced biomass conversion and CO2capturetechnology could improve BECCS net electricity balance, but at the cos
Schnellmann MA, Heuberger CF, Scott SA, et al., 2018, Quantifying the role and value of chemical looping combustion in future electricity systems via a retrosynthetic approach, International Journal of Greenhouse Gas Control, Vol: 73, Pages: 1-15, ISSN: 1750-5836
Carbon capture and sequestration of CO2from the combustion of fossil fuels in thermal power plants is expected to be important in the mitigation of climate change. Deployment however falls far short of what is required. A key barrier is the perception by developers and investorsthat these technologies are too inefficient, expensive and risky. To address these issues, we have developed a novel retrosynthetic approach to evaluate technologies and their design based on the demands of the system in which they would operate. We have applied it to chemical looping combustion (CLC), a promising technology, which enables carbon dioxide emissions to be inherently captured from the combustion of fossil fuels. Our approach has provided unique insight into the potential role and value of different CLC variants in future electricity systems and the likely impact of their integration on the optimal capacity mix, the operational and system cost, and dispatch patterns. The three variants investigated couldall provide significant value by reducing the total investment and operational cost of a future electricity system. The minimisation of capital cost appears to be key for the attractiveness of CLC, rather than other factors such as higher efficiency or loweroxygen carrier costs.
Heuberger CF, Staffell I, Shah N, et al., 2018, Impact of myopic decision-making and disruptive events in power systems planning, Nature Energy, Vol: 3, Pages: 634-640, ISSN: 1520-8524
The delayed deployment of low-carbon energy technologies is impeding energy system decarbonization. The continuing debate about the cost-competitiveness of low-carbon technologies has led to a strategy of waiting for a ‘unicorn technology’ to appear. Here, we show that myopic strategies that rely on the eventual manifestation of a unicorn technology result in either an oversized and underutilized power system when decarbonization objectives are achieved, or one that is far from being decarbonized, even if the unicorn technology becomes available. Under perfect foresight, disruptive technology innovation can reduce total system cost by 13%. However, a strategy of waiting for a unicorn technology that never appears could result in 61% higher cumulative total system cost by mid-century compared to deploying currently available low-carbon technologies early on.
Heuberger C, Mac Dowell N, 2018, Real-world challenges with a rapid transition to 100 % renewable power systems, Joule, Vol: 2, Pages: 367-370, ISSN: 2542-4351
Bui M, Adjiman CS, Bardow A, et al., 2018, Carbon capture and storage (CCS): the way forward, Energy and Environmental Science, Vol: 11, Pages: 1062-1176, ISSN: 1754-5692
Carbon capture and storage (CCS) is broadly recognised as having the potential to play a key role in meeting climate change targets, delivering low carbon heat and power, decarbonising industry and, more recently, its ability to facilitate the net removal of CO2 from the atmosphere. However, despite this broad consensus and its technical maturity, CCS has not yet been deployed on a scale commensurate with the ambitions articulated a decade ago. Thus, in this paper we review the current state-of-the-art of CO2 capture, transport, utilisation and storage from a multi-scale perspective, moving from the global to molecular scales. In light of the COP21 commitments to limit warming to less than 2 °C, we extend the remit of this study to include the key negative emissions technologies (NETs) of bioenergy with CCS (BECCS), and direct air capture (DAC). Cognisant of the non-technical barriers to deploying CCS, we reflect on recent experience from the UK's CCS commercialisation programme and consider the commercial and political barriers to the large-scale deployment of CCS. In all areas, we focus on identifying and clearly articulating the key research challenges that could usefully be addressed in the coming decade.
Galán-Martín A, Pozo C, Azapagic A, et al., 2018, Time for global action: an optimised cooperative approach towards effective climate change mitigation, Energy and Environmental Science, Vol: 11, Pages: 572-581, ISSN: 1754-5692
The difficulties in climate change negotiations together with the recent withdrawal of the U.S. from the Paris Agreement call for new cooperative mechanisms to enable a resilient international response. In this study we propose an approach to aid such negotiations based on quantifying the benefits of interregional cooperation and distributing them among the participants in a fair manner. Our approach is underpinned by advanced optimisation techniques that automate the screening of millions of alternatives for differing levels of cooperation, ultimately identifying the most cost-effective solutions for meeting emission targets. We apply this approach to the Clean Power Plan, a related act in the U.S. aiming at curbing carbon emissions from electricity generation, but also being withdrawn. We find that, with only half of the states cooperating, the cost of electricity generation could be reduced by US$41 billion per year, while simultaneously cutting carbon emissions by 68% below 2012 levels. These win–win scenarios are attained by sharing the emission targets and trading electricity among the states, which allows exploiting regional advantages. Fair sharing of dividends may be used as a key driver to spur cooperation since the global action to mitigate climate change becomes beneficial for all participants. Even if global cooperation remains elusive, it is worth trying since the mere cooperation of a few states leads to significant benefits for both the U.S. economy and the climate. These findings call on the U.S. to reconsider its withdrawal but also boost individual states to take initiative even in the absence of federal action.
Patrizio P, Leduc S, Kraxner F, et al., 2018, Reducing US Coal Emissions Can Boost Employment, Joule, Vol: 2, Pages: 2633-2648, ISSN: 2542-4351
Summary Concerns have been voiced that implementing climate change mitigation measures could come at the cost of employment, especially in the context of the US coal sector. However, repurposing US coal plants presents an opportunity to address emission mitigation and job creation, if the right technology change is adopted. In this study, the transformation of the US coal sector until 2050 is modeled to achieve ambitious climate targets. Results show that the cost-optimal strategy for meeting 2050 emission reductions consistent with 2°C stabilization pathways is through the early deployment of BECCS and by replacing 50% of aging coal plants with natural gas plants. This strategy addresses the concerns surrounding employment for coal workers by retaining 40,000 jobs, and creating 22,000 additional jobs by mid-century. Climate change mitigation does not have to come at the cost of employment, and policymakers could seek to take advantage of the social co-benefits of mitigation.
Heuberger C, Staffell I, Shah N, et al., 2017, A systems approach to quantifying the value of power generation and energy storage technologies in future electricity networks, Computers and Chemical Engineering, Vol: 107, Pages: 247-256, ISSN: 0098-1354
A new approach is required to determine a technology's value to the power systems of the 21st century. Conventional cost-based metrics are incapable of accounting for the indirect system costs associated with intermittent electricity generation, in addition to environmental and security constraints. In this work, we formalise a new concept for power generation and storage technology valuation which explicitly accounts for system conditions, integration challenges, and the level of technology penetration. The centrepiece of the system value (SV) concept is a whole electricity systems model on a national scale, which simultaneously determines the ideal power system design and unit-wise operational strategy. It brings typical Process Systems Engineering thinking into the analysis of power systems. The model formulation is a mixed-integer linear optimisation and can be understood as hybrid between a generation expansion and a unit commitment model. We present an analysis of the future UK electricity system and investigate the SV of carbon capture and storage equipped power plants (CCS), onshore wind power plants, and grid-level energy storage capacity. We show how the availability of different low-carbon technologies impact the optimal capacity mix and generation patterns. We find that the SV in the year 2035 of grid-level energy storage is an order of magnitude greater than that of CCS and wind power plants. However, CCS and wind capacity provide a more consistent value to the system as their level of deployment increases. Ultimately, the incremental system value of a power technology is a function of the prevalent system design and constraints.
Kolster C, Masnadi MS, Krevor S, et al., 2017, CO2 enhanced oil recovery: a catalyst for gigatonne-scale carbon capture and storage deployment?, Energy and Environmental Science, Vol: 10, Pages: 2594-2608, ISSN: 1754-5692
Using carbon dioxide for enhanced oil recovery (CO2-EOR) has been widely cited as a potential catalyst for gigatonne-scale carbon capture and storage (CCS) deployment. Carbon dioxide enhanced oil recovery could provide revenues for CO2 capture projects in the absence of strong carbon taxes, providing a means for technological learning and economies of scale to reduce the cost of CCS. We develop an open-source techno-economic Model of Iterative Investment in CCS with CO2-EOR (MIICE), using dynamic technology deployment modeling to assess the impact of CO2-EOR on the deployment of CCS. Synthetic sets of potential CCS with EOR projects are created with typical field characteristics and dynamic oil and CO2 production profiles. Investment decisions are made iteratively over a 35 year simulation period, and long-term changes to technology cost and revenues are tracked. Installed capacity at 2050 is used as an indicator, with 1 gigatonne per year of CO2 capture used as a benchmark for successful large-scale CCS deployment. Results show that current CO2 tax and oil price conditions do not incentivize gigatonne-scale investment in CCS. For current oil prices ($45 per bbl–$55 per bbl), the final CO2 tax must reach $70 per tCO2 for gigatonne-scale deployment. If oil price alone is expected to induce CCS deployment and learning, oil prices above $85 per bbl are required to promote the development of a gigatonne-scale CCS industry. Nonlinear feedbacks between early deployment and learning result in large changes in final state due to small changes in initial conditions. We investigate the future of CCS in five potential ‘states of the world’: an optimistic ‘Base Case’ with a low CO2 tax and low oil price, a ‘Climate Action’ world with high CO2 tax, a ‘High Oil’ world with high oil prices, a ‘Depleting Resources’ world with an increasing deficit in oil supply, and a ‘Forward Learning’ world where mechan
Kolster C, Agada S, Mac Dowell N, et al., 2017, The impact of time-varying CO2 injection rate on large scale storage in the UK Bunter Sandstone, International Journal of Greenhouse Gas Control, Vol: 68, Pages: 77-85, ISSN: 1750-5836
Carbon capture and storage (CCS) is expected to play a key role in meeting targets set by the Paris Agreement and for meeting legally binding greenhouse gas emissions targets set within the UK (Energy and Climate Change Committee, 2016). Energy systems models have been essential in identifying the importance of CCS but they neglect to impose constraints on the availability and use of geologic CO2 storage reservoirs. In this work we analyse reservoir performance sensitivities to varying CO2 storage demand for three sets of injection scenarios designed to encompass the UK's future low carbon energy market. We use the ECLIPSE reservoir simulator and a model of part of the Southern North Sea Bunter Sandstone saline aquifer. From a first set of injection scenarios we find that varying amplitude and frequency of injection on a multi-year basis has little effect on reservoir pressure response and plume migration. Injectivity varies with site location due to variations in depth and regional permeability. In a second set of injection scenarios, we show that with envisioned UK storage demand levels for a large coal fired power plant, it makes no difference to reservoir response whether all injection sites are deployed upfront or gradually as demand increases. Meanwhile, there may be an advantage to deploying infrastructure in deep sites first in order to meet higher demand later. However, deep-site deployment will incur higher upfront cost than shallow-site deployment. In a third set of injection scenarios, we show that starting injection at a high rate with ramping down, a low rate with ramping up or at a constant rate makes little difference to the overall injectivity of the reservoir. Therefore, such variability is not essential to represent CO2 storage in energy systems models resolving plume and pressure evolution over decadal timescales.
Bui M, Fajardy M, Mac Dowell N, 2017, Bio-energy with carbon capture and storage (BECCS): Opportunities for performance improvement, Fuel, Vol: 213, Pages: 164-175, ISSN: 0016-2361
This study evaluates the performance of a 500 MW pulverised fuel BECCS system. A performance matrix is developed to assess the opportunities for BECCS performance improvement in terms of: energy efficiency, carbon intensity, and pollutant emissions. The effect of fuel properties was analysed for variable (i) coal type (high/medium sulphur content), (ii) biomass type (wheat straw and wood chips), (iii) moisture content, and (iv) biomass co-firing proportion %. It was observed that the co-firing of biomass increased the quantity and quality of waste heat available for recovery from the exhaust gas. The opportunities to improve energy efficiency in the BECCS system include enhancing heat recovery and using high performance solvents for CO2 capture, such as biphasic materials. Implementing these approaches increased the power generation efficiency from 31%HHV (conventional MEA system) to 38%HHV (using an advanced biphasic solvent with heat recovery). Furthermore, power generation efficiency was found to influence the carbon intensity on an annual basis and annual capacity (load factor) of the BECCS system. Significant reductions to SOX emissions were achieved by increasing biomass co-firing % or using low sulphur coal.
Mac Dowell N, Hallett J, Mota Martinez M, 2017, Solvent selection and design for CO2 capture - how we might have been missing the point, Sustainable Energy & Fuels, Vol: 1, Pages: 2078-2090, ISSN: 2398-4902
Carbon capture and storage (CCS) is a vital technology for the cost-effective mitigation of anthropogenic CO2 emissions. However, a key obstacle to its deployment on a large scale remains its cost – both capital and operating costs. In this context, the development of improved sorbents is a key research priority. Consequently, there is a vast global effort to develop new materials for this purpose, with literally thousands of new materials having been proposed since the beginning of the millennium. One common element of these contributions is that they focus on the equilibrium capacity of the material to absorb CO2 and rarely, if ever, other key factors such as transport properties. To date, the majority of this effort has cost significant amounts of time and resources and has almost exclusively focused on developing sorbents with increased CO2 capacity and/or reduced heat of regeneration. Given that sorbent regeneration largely dictates operational cost, this would, on the surface, appear rational. However, it is vital to recall that the cost structure of $ per MWh of electricity generated is composed of contributions from both capital and operational costs. Consequently, this single-minded focus on equilibrium CO2 capacity and heat of regeneration excludes the contribution of transport and kinetic properties which determine the equipment size and thus the capital cost. Therefore, in order to develop sorbents which will result in a non-negligible cost reduction, it is essential to move beyond equilibrium-based metrics of sorbent performance. In this paper, we present a new methodological approach for sorbent screening which explicitly includes rate-based phenomena. Our approach uses both monetised and non-monetised performance indicators. Our results suggest that whilst equilibrium CO2 capacity is a key determinant of process performance, transport properties (e.g., viscosity) and other thermophysical properties (e.g., heat capacity) have a significant effect
Fajardy M, Mac Dowell N, 2017, Correction: Can BECCS deliver sustainable and resource efficient negative emissions?, Energy and Environmental Science, Vol: 10, Pages: 2267-2267, ISSN: 1754-5692
Heuberger CF, Rubin ES, Staffell I, et al., 2017, Power Generation Expansion Considering Endogenous Technology Cost Learning, 27th European Symposium on Computer Aided Process Engineering, Publisher: Elsevier
We present a mixed-integer linear formulation of a long-term power generation capacityexpansion problem including endogenous learning of technology investment cost. Weconsider a national-scale power system composed of up to 2000 units of 15 differentpower supply technologies, including international interconnectors for electricity importand export, and grid-level energy storage. We reformulate the non-convex learning curvemodel into a piecewise linear representation of the cumulative investment cost as a functionof cumulative installed capacity. The model is applied to a power system representativeof Great Britain for the years 2015 to 2050. We find that the consideration oftechnology cost learning rate influences the optimal capacity expansion and has systemicimplications on the profitability of the power units.
agada S, jackson S, kolster C, et al., 2017, The impact of energy systems demands on pressure limited CO 2 storage in the Bunter Sandstone of the UK Southern North Sea, International Journal of Greenhouse Gas Control, Vol: 65, Pages: 128-136, ISSN: 1750-5836
National techno-economic pathways to reduce carbon emissions are required for the United Kingdom to meet its decarbonisation obligations as mandated by the Paris Agreement. Analysis using energy systems models indicate that carbon capture and storage is a key technology for the UK to achieve its mitigation targets at lowest cost. There is potential to significantly improve upon the representation of the CO2 storage systems used in these models, but sensitivities of a given reservoir system to future development pathways must be evaluated. To investigate this we generate a range of numerical simulations of CO2 injection into the Bunter Sandstone of the UK Southern North Sea, considered to be one of the most important regional aquifers for CO2 storage. The scenarios investigate the sensitivity of CO2 storage to characteristics of regional development including number of injection sites and target rates of CO2 injection. This enables an evaluation of the impact of a range of deployment possibilities reflecting the range of scenarios that may be explored in an energy system analysis. The results show that limitations in achieving target injection rates are encountered at rates greater than 2 MtCO2/year-site due to local pressure buildup. The areal location of injection sites has minimal impact on the results because the Bunter Sandstone model has good regional connectivity. Rather, the depth of the site is the most important factor controlling limits on CO2 injection due to the relationship between the limiting pressure and the lithostatic pressure gradient. The potential for model simplification is explored by comparison of reservoir simulation with analytical models of average reservoir pressure and near-site pressure. The numerical simulations match average pressure buildup estimated with the “closed-box” analytical model of Zhou et al. (2008) over a 50 year injection period. The pressure buildup at individual sites is estimated using the Mathias et al. (
Psarras P, Krutka H, Fajardy M, et al., 2017, Slicing the pie: how big could carbon dioxide removal be?, WILEY INTERDISCIPLINARY REVIEWS-ENERGY AND ENVIRONMENT, Vol: 6, ISSN: 2041-8396
Heuberger C, Staffell I, Shah N, et al., 2017, What is the Value of CCS in the Future Energy System?, 13th International Conference on Greenhouse Gas Control Technologies, Publisher: Elsevier, Pages: 7564-7572, ISSN: 1876-6102
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.
Leeson D, Fennell P, Shah N, et al., 2017, A Techno-economic analysis and systematic review of carbon capture and storage (CCS) applied to the iron and steel, cement, oil refining and pulp and paper industries., 13th International Conference on Greenhouse Gas Control Technologies (GHGT), Publisher: Elsevier, Pages: 6297-6302, ISSN: 1876-6102
A systematic review into the literature surrounding industrial carbon capture has been performed, with a particular focus on costs per tonne of CO2 avoided. The authors have reviewed 250 research articles in order to extract data regarding industrial CCS, focusing on four main carbon-emitting industries; the iron and steel industry, the refining industry, the pulp and paper industry and the cement industry. Only 25 costs were returned as part of the search, and across the four industries they suggested that the cost of carbon capture on industries after conversion to 2013 US Dollars is $20-140 per tonne of CO2 avoided. The highest costs were found using amine scrubbing, the most mature technology, with other less mature technologies reporting lower costs, for example, calcium looping applied to the cement industry was reported to have costs of in the range of $20-75 per tonne avoided, with the only lower costs reported being in the pulp and paper industry reported between $16 and $35. However, the paucity of costing data increases the uncertainty surrounding industrial CCS, meaning that more economic data are required before any conclusive decisions can be made.
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