14,062 research outputs found
A cost-benefit analysis of a pellet boiler with electrostatic precipitator versus conventional biomass technology: A case study of an institutional boiler in Syracuse, New York
BACKGROUND: Biomass facilities have received increasing attention as a strategy to increase the use of renewable fuels and decrease greenhouse gas emissions from the electric generation and heating sectors, but these facilities can potentially increase local air pollution and associated health effects. Comparing the economic costs and public health benefits of alternative biomass fuel, heating technology, and pollution control technology options provides decision-makers with the necessary information to make optimal choices in a given location.
METHODS: For a case study of a combined heat and power biomass facility in Syracuse, New York, we used stack testing to estimate emissions of fine particulate matter (PM2.5) for both the deployed technology (staged combustion pellet boiler with an electrostatic precipitator) and a conventional alternative (wood chip stoker boiler with a multicyclone). We used the atmospheric dispersion model AERMOD to calculate the contribution of either fuel-technology configuration to ambient primary PM2.5 in a 10 km x 10 km region surrounding the facility, and we quantified the incremental contribution to population mortality and morbidity. We assigned economic values to health outcomes and compared the health benefits of the lower-emitting technology with the incremental costs.
RESULTS: In total, the incremental annualized cost of the lower-emitting pellet boiler was 1.7 million annually, greatly exceeding the differential costs even when accounting for uncertainties. Our analyses also showed complex spatial patterns of health benefits given non-uniform age distributions and air pollution levels.
CONCLUSIONS: The incremental investment in a lower-emitting staged combustion pellet boiler with an electrostatic precipitator was well justified by the population health improvements over the conventional wood chip technology with a multicyclone, even given the focus on only primary PM2.5 within a small spatial domain. Our analytical framework could be generalized to other settings to inform optimal strategies for proposed new facilities or populations.This research was supported by the New York State Energy Research and Development Authority (NYSERDA), via an award to the Northeast States for Coordinated Air Use Management (Agreement #92229). The SCICHEM work of KMZ was supported by the Electric Power Research Institute (EPRI)
Transport in polymer-gel composites: Theoretical methodology and response to an electric field
A theoretical model of electromigrative, diffusive and convectivetransport
polymer-gel composites is presented. Bulk properties are derived from the
standard electrokinetic model with an impenetrable charged sphere embedded in
an electrolyte-saturated Brinkman medium. Because the microstructure can be
carefully controlled, these materials are promising candidates for enhanced
gel-electrophoresis, chemical sensing, drug delivery, and microfluidic pumping
technologies. The methodology provides `exact' solutions for situations where
perturbations from equilibrium are induced by gradients of electrostatic
potential, concentration and pressure. While the volume fraction of the
inclusions should be small, Maxwell's well-known theory of conduction suggests
that the theory may also be accurate at moderate volume fractions. In this
work, the model is used to compute ion fluxes, electrical current density, and
convective flow induced by an applied electric field. The
electric-field-induced (electro-osmotic) flow is a sensitive indicator of the
inclusion zeta-potential and size, electrolyte concentration, and Darcy
permeability of the gel, while the electrical conductivity increment is most
often independent of the polymer gel, and is much less sensitive to particle
and electrolyte characteristics
The Rayleigh-Lamb wave propagation in dielectric elastomer layers subjected to large deformations
The propagation of waves in soft dielectric elastomer layers is investigated.
To this end incremental motions superimposed on homogeneous finite deformations
induced by bias electric fields and pre-stretch are determined. First we
examine the case of mechanically traction-free layer, which is an extension of
the Rayleigh-Lamb problem in the purely elastic case. Two other loading
configurations are accounted for too. Subsequently, numerical examples for the
dispersion relations are evaluated for a dielectric solid governed by an
augmented neo-Hookean strain energy. It is found that the the phase speeds and
frequencies strongly depend on the electric excitation and pre-stretch. These
findings lend themselves at the possibility of controlling the propagation
velocity as well as filtering particular frequencies with suitable choices of
the electric bias field
An Extra Electrostatic Energy in Semiconductors and its Impact in Nanostructures
This work revisits the classical concept of electric energy and suggests that
the common definition is likely to generate large errors when dealing with
nanostructures. For instance, deriving the electrostatic energy in
semiconductors using the traditional formula fails at giving the correct
electrostatic force between capacitor plates and reveals the existence of an
extra contribution to the standard electrostatic energy. This additional energy
is found to proceed from the generation of space charge regions which are
predicted when combining electrostatics laws with semiconductor statistics,
such as for accumulation and inversion layers. On the contrary, no such energy
exists when relying on electrostatics only, as for instance when adopting the
so-called full depletion approximation. The same holds for charged or neutral
insulators that are still consistent with the customary definition, but which
are in fact singular cases. In semiconductors, this additional free energy can
largely exceed the energy gained by the dipoles, thus becoming the dominant
term. Consequently, erroneous electrostatic forces in nanostructure systems
such as for MEMS and NEMS as well as incorrect energy calculations are expected
using the standard definition. This unexpected result clearly asks for a
generalization of electrostatic energy in matter in order to reconcile basic
concepts and to prevent flawed force evaluation in nanostructures with
electrical charges.Comment: 24 pages 8 figure
Prospects for Interstellar Propulsion
In recognition of the increasing prospects for Earth-like exoplanet discoveries and its significance for spurring future interstellar voyages of discovery, the United States Congress recently directed NASA to undertake an interstellar mission technology assessment report. In response to this legislative charge to action, NASA has undertaken a series of extramural interstellar workshops aimed at identifying and evaluating technology concepts for enabling an interstellar scientific probe mission, associated technical challenges, technology readiness level assessments, risks, potential near-term milestones, and funding requirements. This paper summarizes these activities and discusses the scientific and technical rationale for a long-term program consisting of incremental, staged technical developments that are extensible for interstellar travel to a nearby star system over many decades
Charged inclusion in nematic liquid crystals
We present a general theory of liquid crystals under inhomogeneous electric
field in a Ginzburg-Landau scheme. The molecular orientation can be deformed by
electric field when the dielectric tensor is orientation-dependent. We then
investigate the influence of a charged particle on the orientation order in a
nematic state. The director is aligned either along or perpendicular to the
local electric field around the charge, depending on the sign of the dielectric
anisotropy. The deformation becomes stronger with increasing the ratio ,
where is the charge and is the radius of the particle. Numerical
analysis shows the presence of defects around the particle for large .
They are nanometer-scale defects for microscopic ions. If the dielectric
anisotropy is positive, a Saturn ring defect appears. If it is negative, a pair
of point defects appear apart from the particle surface, each being connected
to the surface by a disclination line segment.Comment: 12 figure
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