Publications
163 results found
Chiquier S, Patrizio P, Bui M, et al., 2023, A comparative analysis of the efficiency, timing, and permanence of CO<sub>2</sub> removal pathways(Vol 15, pg 4389, 2022), ENERGY & ENVIRONMENTAL SCIENCE, Vol: 16, Pages: 321-321, ISSN: 1754-5692
Ganzer C, Pratama YW, Mac Dowell N, 2022, The role and value of inter-seasonal grid-scale energy storage in net zero electricity systems, International Journal of Greenhouse Gas Control, Vol: 120, Pages: 1-13, ISSN: 1750-5836
Grid-scale inter-seasonal energy storage and its ability to balance power demand and the supply of renewable energy may prove vital to decarbonise the broader energy system. Whilst there is a focus on techno-economic analysis and battery storage, there is a relative paucity of work on grid-scale energy storage on the system level with the required temporal resolution. Here, we evaluate the potential of power-to-gas-to-power as inter-seasonal energy storage technology. Our results suggest that inter-seasonal energy storage can reduce curtailment of renewable energy, and overcapacity of intermittent renewable power. Importantly, grid scale energy storage assumes a critical role especially when the technology options for dispatchable power are limited. It appears that neither high CAPEX nor low round-trip efficiency preclude the value of the technology per se, however the rate of charge and discharge of the technology emerges as key technical characteristic. This study emphasises the rising importance of balancing seasonality in energy systems characterised by a high penetration of renewable energy, and prompts questions regarding sector integration and resilient decision-making toward a zero-carbon economy.
Romano MC, Antonini C, Bardow A, et al., 2022, Comment on "How green is blue hydrogen?", ENERGY SCIENCE & ENGINEERING, Vol: 10, Pages: 1944-1954
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- Citations: 14
Gonzalez-Garay A, Bui M, Freire Ordóñez D, et al., 2022, Hydrogen production and its applications to mobility, Annual Review of Chemical and Biomolecular Engineering, Vol: 13, Pages: 501-528, ISSN: 1947-5438
Hydrogen has been identified as one of the key elements to bolster longer-term climate neutrality and strategic autonomy for several major countries. Multiple road maps emphasize the need to accelerate deployment across its supply chain and utilization. Being one of the major contributors to global CO2 emissions, the transportation sector finds in hydrogen an appealing alternative to reach sustainable development through either its direct use in fuel cells or further transformation to sustainable fuels. This review summarizes the latest developments in hydrogen use across the major energy-consuming transportation sectors. Rooted in a systems engineering perspective, we present an analysis of the entire hydrogen supply chain across its economic, environmental, and social dimensions. Providing an outlook on the sector, we discuss the challenges hydrogen faces in penetrating the different transportation markets.
Heldebrant DJ, Kothandaraman J, Mac Dowell N, et al., 2022, Next steps for solvent-based CO<sub>2</sub> capture; integration of capture, conversion, and mineralisation, CHEMICAL SCIENCE, Vol: 13, Pages: 6445-6456, ISSN: 2041-6520
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- Citations: 16
Pratama YW, Mac Dowell N, 2022, Carbon capture and storage investment: fiddling while the planet burns, One Earth, Vol: 5, Pages: 434-442, ISSN: 2590-3322
Carbon capture and storage (CCS) has been recognized as a key technology in energy systems decarbonization. However, numerous attempts to deploy CCS failed, and the technology is still viewed as pre-commercial. Consequently, public investment in CCS has been largely limited to research, development, and demonstration (RD&D) in capture technology. While it is understood that private investment will typically focus on the development of intellectual property aimed at delivering a commercial advantage, there is a lack of evidence that public investment in CCS RD&D can deliver commercial viability. Here, we show that, while improved CCS technology in the electricity systems will deliver larger market shares to the technology developers, the benefit on overall system cost is negligible. Thus, public sector efforts should focus primarily on overcoming commercialization failures, such as the absence of CO2 transport and storage infrastructures and other deployment barriers, leaving the development of intellectual property to the private sector.
Patrizio P, Sunny N, Mac Dowell N, 2022, Inefficient investments as a key to narrowing regional economic imbalances, ISCIENCE, Vol: 25
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- Citations: 1
Galan-Martin A, Vazquez D, Cobo S, et al., 2021, Delaying carbon dioxide removal in the European Union puts climate targets at risk, NATURE COMMUNICATIONS, Vol: 12
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- Citations: 22
Mac Dowell N, Sunny N, Brandon N, et al., 2021, The hydrogen economy: A pragmatic path forward, Joule, Vol: 5, Pages: 2524-2529, ISSN: 2542-4351
For hydrogen to play a meaningful role in a sustainable energy system, all elements of the value chain must scale coherently. Advocates support electrolytic (green) hydrogen or (blue) hydrogen that relies on methane reformation with carbon capture and storage; however, efforts to definitively choose how to deliver this scaling up are premature. For blue hydrogen, methane emissions must be minimized. Best in class supply chain management in combination with high rates of CO2 capture can deliver a low carbon hydrogen product. In the case of electrolytic hydrogen, the carbon intensity of power needs to be very low for this to be a viable alternative to blue hydrogen. Until the electricity grid is deeply decarbonized, there is an opportunity cost associated with using renewable energy to produce hydrogen, as opposed to integrating this with the power system. To have a realistic chance of success, net zero transition pathways need to be formulated in a way that is coherent with socio-political-economic constraints.
Negri V, Galan-Martin A, Pozo C, et al., 2021, Life cycle optimization of BECCS supply chains in the European Union, APPLIED ENERGY, Vol: 298, ISSN: 0306-2619
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- Citations: 9
Patrizio P, Fajardy M, Bui M, et al., 2021, CO<sub>2</sub> mitigation or removal: The optimal uses of biomass in energy system decarbonization, ISCIENCE, Vol: 24
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- Citations: 14
Danaci D, Bui M, Petit C, et al., 2021, En route to zerio emissions for power and industry with amine-based post-combustion capture, Environmental Science and Technology (Washington), Vol: 55, Pages: 10619-10632, ISSN: 0013-936X
As more countries commit to a net-zero GHG emission target, we need a whole energy and industrial system approach to decarbonization rather than focus on individual emitters. This paper presents a techno-economic analysis of monoethanolamine-based post-combustion capture to explore opportunities over a diverse range of power and industrial applications. The following ranges were investigated: feed gas flow rate between 1–1000 kg ·s–1, gas CO2 concentrations of 2–42%mol, capture rates of 70–99%, and interest rates of 2–20%. The economies of scale are evident when the flue gas flow rate is <20 kg ·s–1 and gas concentration is below 20%mol CO2. In most cases, increasing the capture rate from 90 to 95% has a negligible impact on capture cost, thereby reducing CO2 emissions at virtually no additional cost. The majority of the investigated space has an operating cost fraction above 50%. In these instances, reducing the cost of capital (i.e., interest rate) has a minor impact on the capture cost. Instead, it would be more beneficial to reduce steam requirements. We also provide a surrogate model which can evaluate capture cost from inputs of the gas flow rate, CO2 composition, capture rate, interest rate, steam cost, and electricity cost.
Daggash HA, Mac Dowell N, 2021, Delivering low-carbon electricity systems in sub-Saharan Africa: insights from Nigeria, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 14, Pages: 4018-4037, ISSN: 1754-5692
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- Citations: 8
Mersch M, Olympios A, Sapin P, et al., 2021, Solar-thermal heating potential in the UK: A techno-economic whole-energy system analysis, ECOS 2021 - The 34rth International Conference On Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, Publisher: ECOS
We investigate the potential of solar-thermal collectorsas a sustainable heat-generation technology in the UK. The costs and performance of commercially-available collectors are surveyed and four representative collectors are investigated using a techno-economic model of solar heating for households. A parametric study of different collectorsand storage tank sizes is conducted to assess the potential and economics of different system layouts. It is shown that moderately-sized systems with a collector area of 4m2 and a tank size of 150L can provide up to 70% of the domestic hot water demand of a typical household in the UK. Based on the data from the solar-thermal heating model at household scale, performance maps are developed to estimate the heat output from different systems under varying operating conditions. These are then used to assess solar-thermal systems in a heating-sector decarbonisation model.The model is a mixed-integer linear programming model that optimises the capacity expansion of the UK domestic heating sector until 2050 as well as the annual operating schedules of the different technologies. It is found that solar-thermal heating requires incentives in order to be competitive with hydrogen boilers or electric heat pumps. However, if solar thermal collectors are deployed, they provide significant system value by reducing the demand for carbon-neutral hydrogen or electricity. An investment incentive of £3,000per solar-thermal system leads to a deployment of over150GW of solar-thermal capacity by 2050, which reduces the annual hydrogen demand by 240 TWh compared to the baseline without solar-thermal heating, while the electricity demand increases by 90 TWh due to heat pumps and electric resistive heatersbeing used as backup heatingtechnologies.
Homan S, Mac Dowell N, Brown S, 2021, Grid frequency volatility in future low inertia scenarios: Challenges and mitigation options, APPLIED ENERGY, Vol: 290, ISSN: 0306-2619
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- Citations: 22
Fajardy M, Morris J, Gurgel A, et al., 2021, The economics of bioenergy with carbon capture and storage (BECCS) deployment in a 1.5 degrees C or 2 degrees C world, GLOBAL ENVIRONMENTAL CHANGE-HUMAN AND POLICY DIMENSIONS, Vol: 68, Pages: 1-18, ISSN: 0959-3780
Bioenergy with carbon capture and storage (BECCS) and afforestation are key negative emission technologies suggested in many studies under 2 °C or 1.5 °C scenarios. However, these large-scale land-based approaches have raised concerns about their economic impacts, particularly their impact on food prices, as well as their environmental impacts. Here we focus on quantifying the potential scale of BECCS and its impact on the economy, taking into account technology and economic considerations, but excluding sustainability and political aspects. To do so, we represent all major components of BECCS technology in the MIT Economic Projection and Policy Analysis model. We find that BECCS could make a substantial contribution to emissions reductions in the second half of the century under 1.5 and 2 °C climate stabilization goals, with its deployment driven by revenues from carbon dioxide permits. Results show that global economic costs and the carbon prices needed to hit the stabilization targets are substantially lower with the technology available, and BECCS acts as a true backstop technology at carbon prices around $240 per tonne of carbon dioxide. If driven by economics alone, BECCS deployment increases the use of productive land for bioenergy production, causing substantial land use changes. However, the projected impact on commodity prices is quite limited at the global scale, with global commodity price indices increasing by less than 5% on average. The effect is larger at the regional scale (up to 15% in selected regions), though significantly lower than previous estimates. While BECCS deployment is likely to be constrained for environmental and/or political reasons, this study shows that the large-scale deployment of BECCS is not detrimental to agricultural commodity prices and could reduce the costs of meeting stabilization targets. Still, it is crucial that policies consider carbon dioxide removal as a complement to drastic carbon dioxide emissions red
Bui M, Zhang D, Fajardy M, et al., 2021, Delivering carbon negative electricity, heat and hydrogen with BECCS – Comparing the options, International Journal of Hydrogen Energy, Vol: 46, Pages: 15298-15321, ISSN: 0360-3199
Biomass can be converted into a range of different end-products; and when combined with carbon capture and storage (CCS), these processes can provide negative CO2 emissions. Biomass conversion technologies differ in terms of costs, system efficiency and system value, e.g. services provided, market demand and product price. The aim of this study is to comparatively assess a combination of BECCS pathways to identify the applications which offer the most valuable outcome, i.e. maximum CO2 removal at minimum cost, ensuring that resources of sustainable biomass are utilised efficiently. Three bioenergy conversion pathways are evaluated in this study: (i) pulverised biomass-fired power plants which generate electricity (BECCS), (ii) biomass-fuelled combined heat and power plants (BE-CHP-CCS) which provide both heat and electricity, and (iii) biomass-derived hydrogen production with CCS (BHCCS). The design and optimisation of the BECCS supply chain network is evaluated using the Modelling and Optimisation of Negative Emissions Technology framework for the UK (MONET-UK), which integrates biogeophysical constraints and a wide range of biomass feedstocks. The results show that indigenous sources of biomass in the UK can remove up to 56 /yr from the atmosphere without the need to import biomass. Regardless of the pathway, Bio-CCS deployment could materially contribute towards meeting a national CO2 removal target and provide a substantial contribution to a national-scale energy system. Finally, it was more cost-effective to deploy all three technologies (BECCS, BE-CHP-CCS and BHCCS) in combination rather than individually.
Cuellar-Franca RM, Garcia-Gutierrez P, Hallett JP, et al., 2021, A life cycle approach to solvent design: challenges and opportunities for ionic liquids - application to CO<sub>2</sub> capture, REACTION CHEMISTRY & ENGINEERING, Vol: 6, Pages: 258-278, ISSN: 2058-9883
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- Citations: 9
Brandl P, Bui M, Hallett JP, et al., 2021, Beyond 90% capture: Possible, but at what cost?, International Journal of Greenhouse Gas Control, Vol: 105, Pages: 1-16, ISSN: 1750-5836
Carbon capture and storage (CCS) will have an essential role in meeting our climate change mitigation targets. CCS technologies are technically mature and will likely be deployed to decarbonise power, industry, heat, and removal of CO2 from the atmosphere. The assumption of a 90% CO2 capture rate has become ubiquitous in the literature, which has led to doubt around whether CO2 capture rates above 90% are even feasible. However, in the context of a 1.5 °C target, going beyond 90% capture will be vital, with residual emissions needing to be indirectly captured via carbon dioxide removal (CDR) technologies. Whilst there will be trade-offs between the cost of increased rates of CO2 capture, and the cost of offsets, understanding where this lies is key to minimising the dependence on CDR. This study quantifies the maximum limit of feasible CO2 capture rate for a range of power and industrial sources of CO2, beyond which abatement becomes uneconomical. In no case, was a capture rate of 90% found to be optimal, with capture rates of up to 98% possible at a relatively low marginal cost. Flue gas composition was found to be a key determinant of the cost of capture, with more dilute streams exhibiting a more pronounced minimum. Indirect capture by deploying complementary CDR is also assessed. The results show that current policy initiatives are unlikely to be sufficient to enable the economically viable deployment of CCS in all but a very few niche sectors of the economy.
Landera A, Mac Dowell N, George A, 2021, Development of robust models for the prediction of Reid vapor pressure (RVP) in fuel blends and their application to oxygenated biofuels using the SAFT-γ approach, FUEL, Vol: 283, ISSN: 0016-2361
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- Citations: 5
Denbow C, Le Brun N, Dowell NM, et al., 2020, The potential impact of Molten Salt Reactors on the UK electricity grid, Journal of Cleaner Production, Vol: 276, Pages: 1-18, ISSN: 0959-6526
The UK electricity grid is expected to supply a growing electricity demand and also to cope with electricity generation variability as the country pursues a low-carbon future. Molten Salt Reactors (MSRs) could offer a solution to meet this demand thanks to their estimated low capital costs, low operational risk, and promise of reliably dispatchable low-carbon electricity. In the published literature, there is little emphasis placed on estimating or modelling the future impact of MSRs on electricity grids. Previous modelling efforts were limited to quantifying the value of renewable energy sources, energy storage and carbon capture technologies. To date, no study has assessed or modelled MSRs as a competing power generation source for meeting decarbonization targets. Given this gap, the main objective of this paper is to explore the cost benefits for policy makers, consumers, and investors when MSRs are deployed between 2020 and 2050 for electricity generation in the UK. This paper presents results from electricity systems optimization (ESO) modelling of the costs associated with the deployment of 1350 MWe MSRs, from 2025 onwards to 2050, and compares this against a UK grid with no MSR deployment. Results illustrate a minimum economic benefit of £1.25 billion for every reactor installed over this time period. Additionally, an investment benefit occurs for a fleet of these reactors which have a combined net present value (NPV) of £22 billion in 2050 with a payback period of 23 years if electricity is sold competitively to consumers at a price of £60/MWh.
Sunny N, Mac Dowell N, Shah N, 2020, What is needed to deliver carbon-neutral heat using hydrogen and CCS?, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 13, Pages: 4204-4224, ISSN: 1754-5692
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- Citations: 39
Ku AY, Cook PJ, Hao P, et al., 2020, Cross-regional drivers for CCUS deployment, CLEAN ENERGY, Vol: 4, Pages: 202-232, ISSN: 2515-4230
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- Citations: 8
Patrizio P, Pratama YW, Mac Dowell N, 2020, Socially equitable energy system transitions, Joule, Vol: 4, Pages: 1700-1713, ISSN: 2542-4351
The European transition to a net-zero economy by 2050 implies a wide range of changes that may adversely affect certain industrial sectors, communities, and regions. However, these impacts are entirely obscured by conventional least-cost analyses. Thus, this work compares the socio-economic impacts of various strategies to decarbonize the energy system by 2050 within the framework of the Sustainable Development Goals (SDGs). We demonstrate that transitions that protect domestic strategic assets and preserve key industrial sectors correspondingly deliver a socially equitable transition. Adopting a technology-agnostic approach to decarbonizing the European electricity system maximizes the associated co-benefits and potentially increases the gross value added (GVA) to the economy by 50% relative to a business as usual scenario. This new way of thinking about the economic transition fundamentally reframes the discussion from one of cost to one of opportunity.
Ganzer C, Mac Dowell N, 2020, A comparative assessment framework for sustainable production of fuels and chemicals explicitly accounting for intermittency, SUSTAINABLE ENERGY & FUELS, Vol: 4, Pages: 3888-3903, ISSN: 2398-4902
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- Citations: 6
Firth AEJ, Mac Dowell N, Fennell PS, et al., 2020, Assessing the economic viability of wetland remediation of wastewater, and the potential for parallel biomass valorisation, Environmental Science: Water Research & Technology, Vol: 6, Pages: 2103-2121, ISSN: 2053-1400
Constructed wetlands have been shown to consistently remove a wide range of pollutants from contaminated water. However, no wide-ranging studies exist on the economic viability of this technology. This paper performs a high-level economic comparison between wetland remediation and conventional water remediation technologies, for a wide range of contaminant inputs, outputs, and flow rates. The cases considered are nutrient removal from wastewater, and remediation of low-pH and circumneutral acid mine drainage (AMD). The first-order P-k-C* model is used for nutrient removal, while a zeroth-order model is used for AMD remediation, with removal rate data taken from the literature. The number of wetland cells employed was found to significantly affect the overall cost of nutrient removal, allowing savings of up to 86% and 42% for biochemical oxygen demand and phosphorus removal, particularly for low concentrations and flow rates. For integrated secondary and tertiary treatment, wetland remediation was economically competitive down to stringent effluent standards. A sensitivity analysis was performed on sizing and costing parameters of nutrient removal wetlands, with required wetland size found to be most strongly correlated with the assumed removal rate, and land costs found to have relatively little effect on overall costs. Wetland remediation of AMD was only found to be economically favourable for less severe conditions and lower flow rates when treating low-pH drainage, and was heavily influenced by the acidity removal rate. However, the majority of site data from literature was found to fall within this range of conditions. For circumneutral AMD, wetland remediation was found to be cheaper for all simulated cases. The feasibility of offsetting wetland remediation costs through biomass valorisation was investigated for a range of products, with area requirements for minimum economic production identified as the principal barrier.
Fajardy M, Mac Dowell N, 2020, Recognizing the value of collaboration in delivering carbon dioxide removal, One Earth, Vol: 3, Pages: 214-225, ISSN: 2590-3322
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.
Pozo C, Galán-Martín Á, Reiner DM, et al., 2020, Equity in allocating carbon dioxide removal quotas, Nature Climate Change, Vol: 10, Pages: 640-646, ISSN: 1758-678X
The first nationally determined contributions to the Paris Agreement include no mention of the carbon dioxide removal (CDR) necessary to reach the Paris targets, leaving open the question of how and by whom CDR will be delivered. Drawing on existing equity frameworks, we allocate CDR quotas globally according to Responsibility, Capability and Equality principles. These quotas are then assessed in the European Union context by accounting for domestic national capacity of a portfolio of CDR options, including bioenergy with carbon capture and storage, reforestation and direct air capture. We find that quotas vary greatly across principles, from 33 to 325 GtCO2 allocated to the European Union, and, due to biophysical limits, only a handful of countries could meet their quotas acting individually. These results support strengthening cross-border cooperation while highlighting the need to urgently deploy CDR options to mitigate the risk of failing to meet the climate targets equitably.
Olympios A, Hoisenpoori P, Mersch M, et al., 2020, Optimal design of low-temperature heat-pumping technologies and implications to the whole energy system, The 33rd International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems.
This paper presents a methodology for identifying optimal designs for air-source heat pumps suitable for domestic heating applications from the whole-energy system perspective, accounting explicitly for a trade-off between cost and efficiency, as well as for the influence of the outside air temperature during off-design operation. The work combines dedicated brazed-plate and plate-fin heat-exchanger models with compressor efficiency maps, as well as equipment costing techniques, in order to develop a comprehensive technoeconomic model of a low-temperature air-source heat pump with a single-stage-compressor, based on the vapour-compression cycle. The cost and performance predictions are validated against manufacturer data and a non-linear thermodynamic optimisation model is developed to obtain optimal component sizes for a set of competing working fluids and design conditions. The cost and off-design performance of different configurations are integrated into a whole-energy system capacity-expansion and unit-dispatch model of the UK power and heat system. The aim is to assess the system value of proposed designs, as well as the implications of their deployment on the power generation mix and total transition cost of electrifying domestic heat in the UK as a pathway towards meeting a national net-zero emission target by 2050. Refrigerant R152a appears to have the best design and off-design performance, especially compared to the commonly used R410a. The size of the heat exchangers has a major effect on heat pump performance and cost. From a wholesystem perspective, high-performance heat pumps enable a ~20 GW (~10%) reduction in the required installed power generation capacity compared to smaller-heat-exchanger, low-performance heat pumps, which in turn requires lower and more realistic power-grid expansion rates. However, it is shown that the improved performance as a result of larger heat exchangers does not compensate overall for the increased technology cost, with
Al-Qahtani A, Gonzalez-Garay A, Bernardi A, et al., 2020, Electricity grid decarbonisation or green methanol fuel? A life-cycle modelling and analysis of today's transportation-power nexus, APPLIED ENERGY, Vol: 265, ISSN: 0306-2619
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- Citations: 21
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