419 research outputs found
A necklace of Wulff shapes
In a probabilistic model of a film over a disordered substrate, Monte-Carlo
simulations show that the film hangs from peaks of the substrate. The film
profile is well approximated by a necklace of Wulff shapes. Such a necklace can
be obtained as the infimum of a collection of Wulff shapes resting on the
substrate. When the random substrate is given by iid heights with exponential
distribution, we prove estimates on the probability density of the resulting
peaks, at small density
CCS from industrial sources
The literature concerning the application of CCS to industry is reviewed. Costs are presented for different sectors including ``high purity'' (processes which inherently produce a high concentration of CO2), cement, iron and steel, refinery and biomass. The application of CCS to industry is a field which has had much less attention than its application to the electricity production sector. Costs range from less than 2011 100/tCO 2 . In the words of a synthesis report from the United Nations Industrial Development Organisation (UNIDO) ``This area has so far not been the focus of discussions and therefore much attention needs to be paid to the application of CCS to industrial sources if the full potential of CCS is to be unlocked''
Metastable wetting
Consider a droplet of liquid on top of a grooved substrate. The wetting or
not of a groove implies the crossing of a potential barrier as the interface
has to distort, to hit the bottom of the groove. We start with computing the
free energies of the dry and wet states in the context of a simple
thermodynamical model before switching to a random microscopic version
pertaining to the Solid-on-Solid (SOS) model. For some range in parameter space
(Young angle, pressure difference, aspect ratio), the dry and wet states both
share the same free energy, which means coexistence. We compute these
coexistence lines together with the metastable regions. In the SOS case, we
describe the dynamic transition between coexisting states in wetting. We show
that the expected time to switch from one state to the other grows
exponentially with the free energy barrier between the stable states and the
saddle state, proportional to the groove's width. This random time appears to
have an exponential-like distribution
Random walk weakly attracted to a wall
We consider a random walk X_n in Z_+, starting at X_0=x>= 0, with transition
probabilities P(X_{n+1}=X_n+1|X_n=y>=1)=1/2-\delta/(4y+2\delta)
P(X_{n+1}=X_n+1|X_n=y>=1)=1/2+\delta/(4y+2\delta) and X_{n+1}=1 whenever X_n=0.
We prove that the expectation value of X_n behaves like n^{1-(\delta/2)} as n
goes to infinity when \delta is in the range (1,2). The proof is based upon the
Karlin-McGregor spectral representation, which is made explicit for this random
walk.Comment: Replacement with minor changes and additions in bibliography. Same
abstract, in plain text rather than Te
Force-velocity relation and density profiles for biased diffusion in an adsorbed monolayer
In this paper, which completes our earlier short publication [Phys. Rev.
Lett. 84, 511 (2000)], we study dynamics of a hard-core tracer particle (TP)
performing a biased random walk in an adsorbed monolayer, composed of mobile
hard-core particles undergoing continuous exchanges with a vapor phase. In
terms of an approximate approach, based on the decoupling of the third-order
correlation functions, we obtain the density profiles of the monolayer
particles around the TP and derive the force-velocity relation, determining the
TP terminal velocity, V_{tr}, as the function of the magnitude of external bias
and other system's parameters. Asymptotic forms of the monolayer particles
density profiles at large separations from the TP, and behavior of V_{tr} in
the limit of small external bias are found explicitly.Comment: Latex, 31 pages, 3 figure
Carbon Capture and Storage
Emissions of carbon dioxide, the most important long-lived anthropogenic greenhouse gas, can be reduced
by Carbon Capture and Storage (CCS). CCS involves the integration of four elements: CO 2 capture, compression of the CO2 from a gas to a liquid or a denser gas, transportation of pressurized CO 2 from the point of capture to the storage location, and isolation from the atmosphere by storage in deep underground rock formations. Considering full life-cycle emissions, CCS technology can reduce 65–85% of CO2 emissions from fossil fuel combustion from stationary sources, although greater reductions may be possible if low emission technologies are applied to activities beyond the plant boundary, such as fuel transportation.
CCS is applicable to many stationary CO2 sources, including the power generation, refining, building
materials, and the industrial sector. The recent emphasis on the use of CCS primarily to reduce emissions from coal-fired electricity production is too narrow a vision for CCS.
Interest in CCS is growing rapidly around the world. Over the past decade there has been a remarkable increase in interest and investment in CCS. Whereas a decade ago, there was only one operating CCS project and little industry or government investment in R&D, and no financial incentives to promote CCS. In 2010, numerous projects of various sizes are active, including at least five large-scale full CCS projects. In 2015, it is expected that 15 large-scale, full-chain CCS projects will be running. Governments and industry have committed over USD 26 billion for R&D, scale-up and deployment.
The technology for CCS is available today, but significant improvements are needed to support widespread
deployment. Technology advances are needed primarily to reduce the cost of capture and increase confidence in storage security. Demonstration projects are needed to address issues of process integration between CO2 capture and product generation, for instance in power, cement and steel production, obtain cost and performance data, and for industry where capture is more mature to gain needed operational experience. Large-scale storage projects in saline aquifers are needed to address issues of site characterization and site selection, capacity assessment, risk management and monitoring.
Successful experiences from five ongoing projects demonstrate that, at least on this limited scale, CCS can
be safe and effective for reducing emissions. Five commercial-scale CCS projects are operational today with over 35 million tonnes of CO2 captured and stored since 1996. Observations from commercial storage projects, commercial enhanced oil recovery projects, engineered and natural analogues as well as theoretical considerations, models, and laboratory experiments suggest that appropriately selected and managed geological storage reservoirs are very likely to retain nearly all the injected CO2 for very long times, more than long enough to provide benefits for the intended purpose of CCS.
Significant scale-up compared to existing CCS activities will be needed to achieve large reductions in CO2
emissions. A 5- to 10-fold scale-up in the size of individual projects is needed to capture and store emissions from a typical coal-fired power plant (500 to 1000 MW). A thousand fold scale-up in size of today’s CCS enterprise would be needed to reduce emissions by billions of tonnes per year (Gt/yr).
The technical potential of CCS on a global level is promising, but on a regional level is differentiated. The
primary technical limitation for CCS is storage capacity. Much more work needs to be done to realistically assess storage capacity on a worldwide, regional basis and sub-regional basis.
Worldwide storage capacity estimation is improving but more experience is needed. Estimates for oil and gas reservoirs are about 1000 GtCO2, saline aquifers are estimated to have a capacity ranging from about 4000 to 23,000 GtCO2. However, there is still considerable debate about how much storage capacity actually exists, particularly in saline aquifers. Research, geological assessments and, most importantly, commercial-scale demonstration projects will be needed to improve confidence in capacity estimates.
Costs and energy requirements for capture are high. Estimated costs for CCS vary widely, depending on the application (e.g. gas clean-up vs. electricity generation), the type of fuel, capture technology, and assumptions about the baseline technology. For example, with today’s technology, CCS would increase cost of generating electricity by 50–100%. In this case, capital costs and parasitic energy requirements of 15–30% are the major cost drivers. Research is underway to lower costs and energy requirements. Early demonstration projects are likely to cost more.
The combination of high cost and low or absent incentives for large-scale deployment are a major factor
limiting the widespread use of CCS. Due to high costs, CCS will not take place without strong incentives to limit CO2 emissions. Certainty about the policy and regulatory regimes will be crucial for obtaining access to capital to build these multi-billion dollar projects.
Environmental risks of CCS appear manageable, but regulations are needed. Regulation needs to ensure due diligence over the lifecycle of the project, but should, most importantly, also govern site selection, operating guidelines, monitoring and closure of a storage facility.
Experience so far has shown that local resistance to CO2 storage projects may appear and can lead to
cancellation of planned CCS projects. Inhabitants of the areas around geological storage sites often have concerns about the safety and effectiveness of CCS. More CCS projects are needed to establish a convincing safety record. Early engagement of communities in project design and site selection as well as credible communication can help ease resistance. Environmental organisations sometimes see CCS as a distraction from a sustainable energy future.
Social, economic, policy and political factors may limit deployment of CCS if not adequately addressed.
Critical issues include ownership of underground pore space (primarily an issue in the US); long-term liability and stewardship; GHG accounting approaches and ve rification; and regulatory oversight regimes. Governments and the private sector are making significant progress on all of these issues. Government support to lower barriers for early deployments is needed to encourage private sector adoption. Developing countries will need support for technology access, lowering the cost of CCS, developing workforce capacity and training regulators for permitting, monitoring and oversight.
CCS combined with biomass can lead to negative emissions . Such technologies are likely to be needed to achieve atmospheric stabilization of CO2 and may provide an additional incentive for CCS adoption
Scaling up climate finance in the context of Covid-19: A science-based call for financial decision-makers
The sooner we act, the lower the risks of climate change and the higher the synergies between climate action and other societal benefits. That is a clear conclusion from the IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels. Financing a rapid transition to achieve the Paris Agreement goals requires significantly more investment and investment in a different set of low emission, climate resilient assets. The Covid-19 crisis increases the imperative to scale up climate action before these goals are out of reach. In particular, it is critical to increase the ability of developing countries to realize their climate ambitions in the context of the pandemic without increasing their debt burden.This new report, Scaling up climate finance in the context of Covid-19, aims to help financial decision-makers to align finance with sustainable development, accelerating the transition to a net-zero, climate resilient economy, based on the latest scientific findings and policy developments. It proposes four sets of actions to support developing countries in achieving this transition.This report aims to help financial decision-makers to align finance with sustainable development, accelerating the transition to a net-zero, climate resilient economy, based on the latest scientific findings and policy developments. It proposes four interventions to achieve this objective in the context of Covid-19
A microscopic model for thin film spreading
A microscopic, driven lattice gas model is proposed for the dynamics and
spatio-temporal fluctuations of the precursor film observed in spreading
experiments. Matter is transported both by holes and particles, and the
distribution of each can be described by driven diffusion with a moving
boundary. This picture leads to a stochastic partial differential equation for
the shape of the boundary, which agrees with the simulations of the lattice
gas. Preliminary results for flow in a thermal gradient are discussed.Comment: 4 pages, 3 figures. Submitte
What are sources of carbon lock-in in energy-intensive industry? A case study into Dutch chemicals production
Keeping global mean temperature rise well below 2 °C requires deep emission reductions in all industrial sectors, but several barriers inhibit such transitions. A special type of barrier is carbon lock-in, defined as a process whereby various forms of increasing returns to adoption inhibit innovation and the competitiveness of low-carbon alternatives, resulting in further path dependency. Here, we explore potential carbon lock-in in the Dutch chemical industry via semi-structured interviews with eleven key actors. We find that carbon lock-in may be the result of (i) technological incompatibility between deep emission reduction options over time, (ii) system integration in chemical clusters, (iii) increasing sunk costs as firms continue to invest in incremental improvements in incumbent installations, (iv) governmental policy inconsistency between targets for energy efficiency and deep emission reductions, and (v) existing safety routines and standards. We also identify barriers that do not have the self-reinforcing character of lock-in, but do inhibit deep emission reductions. Examples include high operating costs of low-carbon options and low risk acceptance by capital providers and shareholders. Rooted in the Dutch policy setting, we discuss policy responses for avoiding carbon lock-in and overcoming barriers based on the interviews, such as transition plans for individual industries and infrastructure subsidies
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