Imperial College London

DrNiallMac Dowell

Faculty of Natural SciencesCentre for Environmental Policy

Senior Lecturer
 
 
 
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Contact

 

+44 (0)20 7594 9298niall Website

 
 
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Location

 

141114 Prince's GardensSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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70 results found

Heuberger CF, Staffell I, Shah N, Mac Dowell Net al., Levelised Value of Electricity - A Systemic Approach to Technology Valuation, 26th European Symposium on Computer Aided Process Engineering - ESCAPE 26

CONFERENCE PAPER

Mac Dowell N, Hallett J, Mota Martinez M, Solvent selection and design for CO2 capture - how we might have been missing the point, Sustainable Energy & Fuels, ISSN: 2398-4902

JOURNAL ARTICLE

Mechleri E, rivotti P, mac Dowell N, thornhill Net al., Flexibility issues and controllability analysis of a post-combustion CO2 capture plant integrated with a natural gas power plant, 8th Trondheim Conference on CO2 Capture, Transport and Storage (TCCS-8)

CONFERENCE PAPER

Agada S, Jackson S, Kolster C, Dowell NM, Williams G, Vosper H, Williams J, Krevor Set 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

JOURNAL ARTICLE

Agada S, Kolster C, Williams G, Vosper H, Macdowell N, Krevor Set al., 2017, Sensitivity Analysis of the Dynamic CO<inf>2</inf> Storage Capacity Estimate for the Bunter Sandstone of the UK Southern North Sea, Pages: 4564-4570, ISSN: 1876-6102

© 2017 The Authors. Carbon capture and storage (CCS) in subsurface reservoirs has been identified as a potentially cost-effective way to reduce CO 2 emissions to the atmosphere. Global emissions reductions on the gigatonne scale using CCS will require regional or basin-scale deployment of CO 2 storage in saline aquifers. Thus the evaluation of both the dynamic and ultimate CO 2 storage capacity of formations is important for policy makers to determine the viability of CCS as a pillar of the greenhouse gas mitigation strategy in a particular region. We use a reservoir simulation model representing the large-scale Bunter Sandstone in the UK Southern North Sea to evaluate the dynamics and sensitivities of regional CO 2 plume transport and storage. At the basin-scale, we predict hydrogeological changes in the storage reservoir in response to multiple regional carbon sequestration development scenarios. We test the sensitivity of injection capacity to a range of target CO 2 injection rates and fluctuations in CO 2 supply. Model sensitivities varying the target injection rates indicate that in the absence of pressure management up to 3.7 Gt of CO 2 can be stored in the Bunter region over 50 years given the pressure constraints set to avoid fracturing the formation. Long-term (approx. 1000 years), our results show that up to 16 Gt of CO 2 can be stored in the Bunter region without pressure management. With pressure management, the estimate rises to 32 Gt. However, consideration must be given to the additional operational and economic requirements of pressure management using brine production.

CONFERENCE PAPER

Bhave A, Taylor RHS, Fennell P, Livingston WR, Shah N, Mac Dowell N, Dennis J, Kraft M, Pourkashanian M, Insa M, Jones J, Burdett N, Bauen A, Beal C, Smallbone A, Akroyd Jet al., 2017, Screening and techno-economic assessment of biomass-based power generation with CCS technologies to meet 2050 CO2 targets, APPLIED ENERGY, Vol: 190, Pages: 481-489, ISSN: 0306-2619

JOURNAL ARTICLE

Brandl P, Soltani SM, Fennell PS, Mac Dowell Net al., 2017, Evaluation of cooling requirements of post-combustion CO2 capture applied to coal-fired power plants, CHEMICAL ENGINEERING RESEARCH & DESIGN, Vol: 122, Pages: 1-10, ISSN: 0263-8762

JOURNAL ARTICLE

Bui M, Fajardy M, Mac Dowell N, 2017, Bio-Energy with CCS (BECCS) performance evaluation: Efficiency enhancement and emissions reduction, APPLIED ENERGY, Vol: 195, Pages: 289-302, ISSN: 0306-2619

JOURNAL ARTICLE

Cabral RP, Mac Dowell N, 2017, A novel methodological approach for achieving £/MWh cost reduction of CO<inf>2</inf> capture and storage (CCS) processes, Applied Energy, Vol: 205, Pages: 529-539, ISSN: 0306-2619

© 2017 Elsevier Ltd 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.

JOURNAL ARTICLE

Fajardy M, Mac Dowell N, 2017, Can BECCS deliver sustainable and resource efficient negative emissions?, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 10, Pages: 1389-1426, ISSN: 1754-5692

JOURNAL ARTICLE

Heuberger CF, Rubin ES, Staffell I, Shah N, Mac Dowell Net al., 2017, Power capacity expansion planning considering endogenous technology cost learning, Applied Energy, Vol: 204, Pages: 831-845, ISSN: 0306-2619

© 2017 Elsevier Ltd We present an power systems optimisation model for national-scale power supply capacity expansion considering endogenous technology cost reduction (ESO-XEL). The mixed-integer linear program minimises total system cost while complying with operational constraints, carbon emission targets, and ancillary service requirements. A data clustering technique and the relaxation of integer scheduling constraints is evaluated and applied to decrease the model solution time. Two cost learning curves for the different power technologies are derived: one assuming local learning effects, the other accounting for global knowledge spill-over. A piece-wise linear formulation allows the integration of the exponential learning curves into the ESO-XEL model. The model is applied to the UK power system in the time frame of 2015 to 2050. The consideration of cost learning effects moves optimal investment timings to earlier planning years and influences the competitiveness of technologies. In addition, the maximum capacity build rate parameter influences the share of power generation significantly; the possibility of rapid capacity build-up is more important for total system cost reduction by 2050 than accounting for technology cost reduction.

JOURNAL ARTICLE

Heuberger CF, Staffell I, Shah N, Dowell NMet al., 2017, A systems approach to quantifying the value of power generation and energy storage technologies in future electricity networks, Computers & Chemical Engineering, ISSN: 0098-1354

JOURNAL ARTICLE

Heuberger CF, Staffell I, Shah N, Dowell NM, Davison Jet al., 2017, An MILP Modeling Approach to Systemic Energy Technology Valuation in the 21<sup>st</sup> Century Energy System, Pages: 6358-6365, ISSN: 1876-6102

© 2017 The Authors. New cannot be measured with old. The transformation of the electricity system from a network of fossil-based dispatchable power plants to one with large amounts of intermittent renewable power generation, flexible loads and markets, requires a concurrent development of new evaluation tools and metrics. The focus of this research is to investigate the value of power technologies in order to support decision making on optimal power system design and operation. Technology valuation metrics need to consider the complexity and interdependency of environmental and security objectives, rather than focusing on individual cost-competitiveness of technologies outside of the power system. We present the System Value as a new technology valuation metric, based on a mixed-integer linear program (MILP) formulation of a national-scale electricity system. The Electricity System Optimization model is able to capture detailed technical operation of the individual power plants as well as environmental and security requirements on the system level. We present a case study on the System Value of onshore wind power plants in comparison with Carbon Capture and Storage (CCS) equipped gas-fired power plants in a 2035 UK electricity system. Under the given emission constraints, the deployment of both technologies reduce total system cost of electricity generation. In the case of CCS-equipped power plants the reductions in total system cost are 2 to 5 times higher than for the deployment of onshore wind capacity.

CONFERENCE PAPER

Heuberger CF, Staffell I, Shah N, Mac Dowell Net al., 2017, The changing costs of technology and the optimal investment timing in the power sector

REPORT

Heuberger CF, Staffell I, Shah N, MacDowell Net al., 2017, What is the Value of CCS in the Future Energy System?, Pages: 7564-7572, ISSN: 1876-6102

© 2017 The Authors. 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 t CO2 /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. Published by Elsevier Ltd.

CONFERENCE PAPER

Kolster C, Mechleri E, Krevor S, Mac Dowell Net al., 2017, The role of CO<inf>2</inf> purification and transport networks in carbon capture and storage cost reduction, International Journal of Greenhouse Gas Control, Vol: 58, Pages: 127-141, ISSN: 1750-5836

© 2017 Elsevier Ltd A number of Carbon Capture and Storage projects (CCS) are under way around the world, but the technology's high capital and operational costs act as a disincentive to large-scale deployment. In the case of both oxy-combustion and post-combustion CO 2 capture, the CO 2 compression and purification units (CO 2 CPU) are vital, but costly, process elements needed to bring the raw CO 2 product to a quality that is adequate for transport and storage. Four variants of the CO 2 CPU were modelled in Aspen HYSYS each of which provide different CO 2 product purities at different capital and operating costs. For each unit, a price of CO 2 is calculated by assuming that it is an independent entity in which to invest and the internal rate of return (IRR) must be greater or equal to the minimum rate o f return on investment. In this study, we test the hypothesis that, owing to the fact that CO 2 will likely be transported in multi-source networks, not all CO 2 streams will need to be of high purity, and that it may be possible to combine several sources of varying purity to obtain an end-product that is suitable for storage. We find that, when considering study generated costs for an example network in the UK, optimally combining these different sources into one multi-source transport network subject to a minimum CO 2 purity of 96% can reduce the price of captured CO 2 by 17%.

JOURNAL ARTICLE

Kolster C, Mechleri E, Krevor S, Mac Dowell Net al., 2017, The role of CO2 purification and transport networks in carbon capture and storage cost reduction, INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL, Vol: 58, Pages: 127-141, ISSN: 1750-5836

JOURNAL ARTICLE

Leeson D, Fennell P, Mac Dowell N, Shah Net al., 2017, Simultaneous design of separation sequences and whole process energy integration, Chemical Engineering Research and Design, Vol: 125, Pages: 166-180, ISSN: 0263-8762

© 2017 Institution of Chemical Engineers This paper presents a novel methodology for the optimisation of the preliminary design of heat-integrated multicomponent distillation sequences. This is achieved through use of a reduced process superstructure where the role of splitting each adjacent key component pair is assigned to an individual separation column, greatly reducing the size and complexity of the problem. This methodology uses information about other process streams on site with which heat can be exchanged within the initial design in order to find a plant-wide optimal separation configuration with the aim of reducing the cost of heating provided by utilities including those used for heating and cooling process streams. In order that this model can be formulated as a mixed-integer linear program, this model utilises a discretised temperature grid where stream temperatures are allowed to vary. This methodology was tested on an example of a mixed alkane feed stream, with the sequence changing dependent on the degree of process integration. The method was found to have the potential for significant cost reductions compared to a heuristic design, with the example exhibiting a cost saving of over 50% and a reduction in CO 2 associated with process heating of almost 60%, though the magnitude of these savings is highly dependent on the specific example to which it is applied.

JOURNAL ARTICLE

Leeson D, Mac Dowell N, Shah N, Petit C, Fennell PSet 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, as well as other high purity sources, INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL, Vol: 61, Pages: 71-84, ISSN: 1750-5836

JOURNAL ARTICLE

Mac Dowell N, Fajardy M, 2017, Inefficient power generation as an optimal route to negative emissions via BECCS?, Environmental Research Letters, Vol: 12, ISSN: 1748-9326

Current ambitions to limit climate change to no more than 1.5 °C–2 °C by the end of the 21st century rely heavily on the availability of negative emissions technologies (NETs)—bioenergy with CO2 capture and storage (BECCS) and direct air capture in particular. In this context, these NETs are providing a specific service by removing CO2 from the atmosphere, and therefore investors would expect an appropriate risk-adjusted rate of return, varying as a function of the quantity of public money involved. Uniquely, BECCS facilities have the possibility to generate both low carbon power and remove CO2 from the atmosphere, but in an energy system characterised by high penetration of intermittent renewable energy such as wind and solar power plants, the dispatch load factor of such BECCS facilities may be small relative to their capacity. This has the potential to significantly under utilise these assets for their primary purpose of removing CO2 from the atmosphere. In this study, we present a techno-economic environmental evaluation of BECCS plants with a range of operating efficiencies, considering their full- and part-load operation relative to a national-scale annual CO2 removal target. We find that in all cases, a lower capital cost, lower efficiency BECCS plant is superior to a higher cost, higher efficiency facility from both environmental and economic perspectives. We show that it may be preferable to operate the BECCS facility in base-load fashion, constantly removing CO2 from the atmosphere and dispatching electricity on an as-needed basis. We show that the use of this 'spare capacity' to produce hydrogen for, e.g. injection to a natural gas system for the provision of low carbon heating can add to the overall environmental and economic benefit of such a system. The only point where this hypothesis appears to break down is where the CO2 emissions associated with the biomass supply chain are sufficiently large so as to eliminate the service of CO

JOURNAL ARTICLE

Mac Dowell N, Fennell PS, Shah N, Maitland GCet al., 2017, The role of CO2 capture and utilization in mitigating climate change, Nature Climate Change, Vol: 7, Pages: 243-249, ISSN: 1758-678X

JOURNAL ARTICLE

Mechleri E, Brown S, Fennell PS, Mac Dowell Net al., 2017, CO2 capture and storage (CCS) cost reduction via infrastructure right-sizing, CHEMICAL ENGINEERING RESEARCH & DESIGN, Vol: 119, Pages: 130-139, ISSN: 0263-8762

JOURNAL ARTICLE

Mechleri E, Fennell PS, Dowell NM, 2017, Flexible Operation Strategies for Coal- and gas-CCS Power Stations under the UK and USA Markets, Pages: 6543-6551, ISSN: 1876-6102

© 2017 The Authors. The increased penetration of the intermittent renewable energy has increased the demand for flexible electricity supply. In this work, we evaluate four distinct strategies for flexible operation of CCS power plants: load following, solvent storage, exhaust gas by-pass and variable solvent regeneration (VSR) for coal- and gas-CCS power stations. With the aim to decoupling the power and capture plants in order to maximize profits, a multi-period dynamic optimisation problem was formulated and solved in the context of UK- and US-type markets. It was found that whilst the flexible operation strategies are strongly affected by the different markets, in all cases the variable solvent regeneration strategy was found to be the most profitable.

CONFERENCE PAPER

Mechleri E, Fennell PS, Mac Dowell N, 2017, Optimisation and evaluation of flexible operation strategies for coal- and gas-CCS power stations with a multi-period design approach, INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL, Vol: 59, Pages: 24-39, ISSN: 1750-5836

Thermal power plants are increasingly required to balance power grids by compensating for the intermittent electricity supply from renewable energy resources. As CO2 capture and storage is integrated with both coal- and gas-fired power plants, it is vital that the emission mitigation technology does not compromise their ability to provide this high-value service. Therefore, developing optimal process operation strategies is vital to maximise both the value provided by and the profitability of these important assets. In this work, we present models of coal- and gas-fired power plants, integrated with a post-combustion CO2 capture process using a 30 wt% monoethanolamine (MEA) solvent. With the aim to decoupling the power and capture plants in order to facilitate profit maximising behaviour, a multi-period dynamic optimisation problem was formulated and solved using these models. Four distinct scenarios were evaluated: load following, solvent storage, exhaust gas by-pass and variable solvent regeneration (VSR). It was found that for both coal- and gas-fired power plants, the VSR strategy is consistently the most profitable option. The performance of the exhaust by-pass scenario is a strong function of the carbon prices and is only selected at very low carbon prices. The viability of the solvent storage strategy was found to be a strong function of the capital cost associated with the solvent storage infrastructure. When the cost of the solvent tanks has been paid off, then the solvent storage scenario is 3.3% and 8% more profitable than the baseline for the pulverised coal and gas-fired power plants, respectively. Sensitivity analyses showed that, for all strategies, the flexibility benefit declined with reduced carbon and fuel prices, while a “peakier” electricity market, characteristic of one with significant quantities of intermittent renewables deployment, more significantly rewarded flexible operation.

JOURNAL ARTICLE

Mechleri E, Lawal A, Ramos A, Davison J, Mac Dowell Net al., 2017, Process control strategies for flexible operation of post-combustion CO2 capture plants, INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL, Vol: 57, Pages: 14-25, ISSN: 1750-5836

JOURNAL ARTICLE

Mota-Martinez MT, Hallett J, MacDowell N, 2017, Screening Solvents Properties for CO<inf>2</inf> Capture Based on the Process Performance, Pages: 1551-1557, ISSN: 1876-6102

© 2017 The Authors. Deployment of carbon capture and storage (CCS) technologies is the one of the key strategies to decarbonise the energy system in order to abate the consequences of climate change. Nevertheless, carbon capture is facing some challenges that are deterring its implementation. The capital costs are considered to be very high, and the energy required for solvent regeneration imposes an efficiency penalty on the power plant with which it is integrated. Therefore, it is imperative to seek for opportunities to reduce the overall cost of the CCS. This work focuses on the design strategies for new solvents for the capture of CO 2 from power plants. We have developed a process performance indexed screening tool to assess the suitability of new solvents based on economic, energetic and environmental performance indices. The physicochemical properties of the solvents that lead to reduction of the capture cost have been determined. Published by Elsevier Ltd.

CONFERENCE PAPER

Porter RTJ, Fairweather M, Kolster C, Mac Dowell N, Shah N, Woolley RMet al., 2017, Cost and performance of some carbon capture technology options for producing different quality CO2 product streams, INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL, Vol: 57, Pages: 185-195, ISSN: 1750-5836

JOURNAL ARTICLE

Psarras P, Krutka H, Fajardy M, Zhang Z, Liguori S, Mac Dowell N, Wilcox Jet al., 2017, Slicing the pie: how big could carbon dioxide removal be?, WILEY INTERDISCIPLINARY REVIEWS-ENERGY AND ENVIRONMENT, Vol: 6, ISSN: 2041-8396

JOURNAL ARTICLE

Adams T, Mac Dowell N, 2016, Off-design point modelling of a 420 MW CCGT power plant integrated with an amine-based post-combustion CO2 capture and compression process, APPLIED ENERGY, Vol: 178, Pages: 681-702, ISSN: 0306-2619

JOURNAL ARTICLE

Alhajaj A, Mac Dowell N, Shah N, 2016, A techno-economic analysis of post-combustion CO2 capture and compression applied to a combined cycle gas turbine: Part I. A parametric study of the key technical performance indicators, INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL, Vol: 44, Pages: 26-41, ISSN: 1750-5836

JOURNAL ARTICLE

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