479 research outputs found
IMPACTS OF ENERGY COST INCREASES ON IRRIGATED LAND VALUES
Irrigation development in the Pacific Northwest expanded rapidly during the 1960s and 1970s when economic conditions, including very cheap electricity for pumping water, were favorable for this activity. Thousands of acre of land were irrigated that required lifting water 400 feet or more. The cost of energy for irrigation pumping has risen as much as 400% in recent years, and many of these high pump lift farms are in serious economic difficulty. This study shoes that farms with pump lifts exceeding 400 feet will not be able to replace capital irrigation equipment to remain in production in the long run. Land values on these farms will be determined by dryland production alternatives leaving no rents to sustain the incentive for irrigation.Land Economics/Use, Resource /Energy Economics and Policy,
Minimum-Cost Coverage of Point Sets by Disks
We consider a class of geometric facility location problems in which the goal
is to determine a set X of disks given by their centers (t_j) and radii (r_j)
that cover a given set of demand points Y in the plane at the smallest possible
cost. We consider cost functions of the form sum_j f(r_j), where f(r)=r^alpha
is the cost of transmission to radius r. Special cases arise for alpha=1 (sum
of radii) and alpha=2 (total area); power consumption models in wireless
network design often use an exponent alpha>2. Different scenarios arise
according to possible restrictions on the transmission centers t_j, which may
be constrained to belong to a given discrete set or to lie on a line, etc. We
obtain several new results, including (a) exact and approximation algorithms
for selecting transmission points t_j on a given line in order to cover demand
points Y in the plane; (b) approximation algorithms (and an algebraic
intractability result) for selecting an optimal line on which to place
transmission points to cover Y; (c) a proof of NP-hardness for a discrete set
of transmission points in the plane and any fixed alpha>1; and (d) a
polynomial-time approximation scheme for the problem of computing a minimum
cost covering tour (MCCT), in which the total cost is a linear combination of
the transmission cost for the set of disks and the length of a tour/path that
connects the centers of the disks.Comment: 10 pages, 4 figures, Latex, to appear in ACM Symposium on
Computational Geometry 200
Fish schooling as a basis for vertical axis wind turbine farm design
Most wind farms consist of horizontal axis wind turbines (HAWTs) due to the
high power coefficient (mechanical power output divided by the power of the
free-stream air through the turbine cross-sectional area) of an isolated
turbine. However when in close proximity to neighbouring turbines, HAWTs suffer
from a reduced power coefficient. In contrast, previous research on vertical
axis wind turbines (VAWTs) suggests that closely-spaced VAWTs may experience
only small decreases (or even increases) in an individual turbine's power
coefficient when placed in close proximity to neighbours, thus yielding much
higher power outputs for a given area of land. A potential flow model of
inter-VAWT interactions is developed to investigate the effect of changes in
VAWT spatial arrangement on the array performance coefficient, which compares
the expected average power coefficient of turbines in an array to a
spatially-isolated turbine. A geometric arrangement based on the configuration
of shed vortices in the wake of schooling fish is shown to significantly
increase the array performance coefficient based upon an array of 16x16 wind
turbines. Results suggest increases in power output of over one order of
magnitude for a given area of land as compared to HAWTs.Comment: Submitted for publication in BioInspiration and Biomimetics. Note:
The technology described in this paper is protected under both US and
international pending patents filed by the California Institute of Technolog
Turbulence Transport Modeling and First Orbit Parker Solar Probe (PSP) Observations
Parker Solar Probe (PSP) achieved its first orbit perihelion on November 6,
2018, reaching a heliocentric distance of about 0.165 au (35.55 R).
Here, we study the evolution of fully developed turbulence associated with the
slow solar wind along the PSP trajectory between 35.55 R and 131.64
R in the outbound direction, comparing observations to a theoretical
turbulence transport model. Several turbulent quantities, such as the
fluctuating kinetic energy and the corresponding correlation length, the
variance of density fluctuations, and the solar wind proton temperature are
determined from the PSP SWEAP plasma data along its trajectory between 35.55
R and 131.64 R. The evolution of the PSP derived turbulent
quantities are compared to the numerical solutions of the nearly incompressible
magnetohydrodynamic (NI MHD) turbulence transport model recently developed by
Zank et al. (2017). We find reasonable agreement between the theoretical and
observed results. On the basis of these comparisons, we derive other
theoretical turbulent quantities, such as the energy in forward and backward
propagating modes, the total turbulent energy, the normalized residual energy
and cross-helicity, the fluctuating magnetic energy, and the correlation
lengths corresponding to forward and backward propagating modes, the residual
energy, and the fluctuating magnetic energy
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Solar Energetic Particles Produced by a Slow Coronal Mass Ejection at ∼0.25 au
We present an analysis of Parker Solar Probe (PSP) IS⊙IS observations of ~30–300 keV n⁻¹ ions on 2018 November 11 when PSP was about 0.25 au from the Sun. Five hours before the onset of a solar energetic particle (SEP) event, a coronal mass ejection (CME) was observed by STEREO-A/COR2, which crossed PSP about a day later. No shock was observed locally at PSP, but the CME may have driven a weak shock earlier. The SEP event was dispersive, with higher energy ions arriving before the lower energy ones. Timing suggests the particles originated at the CME when it was at ~7.4R_⊙. SEP intensities increased gradually from their onset over a few hours, reaching a peak, and then decreased gradually before the CME arrived at PSP. The event was weak, having a very soft energy spectrum (−4 to −5 spectral index). The earliest arriving particles were anisotropic, moving outward from the Sun, but later, the distribution was observed to be more isotropic. We present numerical solutions of the Parker transport equation for the transport of 30–300 keV n⁻¹ ions assuming a source comoving with the CME. Our model agrees well with the observations. The SEP event is consistent with ion acceleration at a weak shock driven briefly by the CME close to the Sun, which later dissipated before arriving at PSP, followed by the transport of ions in the interplanetary magnetic field
Quantifying the Energy Budget in the Solar Wind from 13.3-100 Solar Radii
A variety of energy sources, ranging from dynamic processes like magnetic
reconnection and waves to quasi-steady terms like the plasma pressure, may
contribute to the acceleration of the solar wind. We utilize a combination of
charged particle and magnetic field observations from the Parker Solar Probe
(PSP) to attempt to quantify the steady-state contribution of the proton
pressure, the electric potential, and the wave energy to the solar wind proton
acceleration observed by PSP between 13.3 and ~100 solar radii (RS). The proton
pressure provides a natural kinematic driver of the outflow. The ambipolar
electric potential acts to couple the electron pressure to the protons,
providing another definite proton acceleration term. Fluctuations and waves,
while inherently dynamic, can act as an additional effective steady-state
pressure term. To analyze the contributions of these terms, we utilize radial
binning of single-point PSP measurements, as well as repeated crossings of the
same stream at different distances on individual PSP orbits (i.e. "fast radial
scans"). In agreement with previous work, we find that the electric potential
contains sufficient energy to fully explain the acceleration of the slower wind
streams. On the other hand, we find that the wave pressure plays an
increasingly important role in the faster wind streams. The combination of
these terms can explain the continuing acceleration of both slow and fast wind
streams beyond 13.3 RS
Electrons in the Young Solar Wind: First Results from the Parker Solar Probe
The Solar Wind Electrons Alphas and Protons experiment on the Parker Solar
Probe (PSP) mission measures the three-dimensional electron velocity
distribution function. We derive the parameters of the core, halo, and strahl
populations utilizing a combination of fitting to model distributions and
numerical integration for electron distributions measured near
the Sun on the first two PSP orbits, which reached heliocentric distances as
small as AU. As expected, the electron core density and temperature
increase with decreasing heliocentric distance, while the ratio of electron
thermal pressure to magnetic pressure () decreases. These quantities
have radial scaling consistent with previous observations farther from the Sun,
with superposed variations associated with different solar wind streams. The
density in the strahl also increases; however, the density of the halo plateaus
and even decreases at perihelion, leading to a large strahl/halo ratio near the
Sun. As at greater heliocentric distances, the core has a sunward drift
relative to the proton frame, which balances the current carried by the strahl,
satisfying the zero-current condition necessary to maintain quasi-neutrality.
Many characteristics of the electron distributions near perihelion have trends
with solar wind flow speed, , and/or collisional age. Near the Sun,
some trends not clearly seen at 1 AU become apparent, including
anti-correlations between wind speed and both electron temperature and heat
flux. These trends help us understand the mechanisms that shape the solar wind
electron distributions at an early stage of their evolution
Observations of the 2019 April 4 Solar Energetic Particle Event at the Parker Solar Probe
A solar energetic particle event was detected by the Integrated Science Investigation of the Sun (IS⊙IS) instrument suite on Parker Solar Probe (PSP) on 2019 April 4 when the spacecraft was inside of 0.17 au and less than 1 day before its second perihelion, providing an opportunity to study solar particle acceleration and transport unprecedentedly close to the source. The event was very small, with peak 1 MeV proton intensities of ~0.3 particles (cm² sr s MeV)⁻¹, and was undetectable above background levels at energies above 10 MeV or in particle detectors at 1 au. It was strongly anisotropic, with intensities flowing outward from the Sun up to 30 times greater than those flowing inward persisting throughout the event. Temporal association between particle increases and small brightness surges in the extreme-ultraviolet observed by the Solar TErrestrial RElations Observatory, which were also accompanied by type III radio emission seen by the Electromagnetic Fields Investigation on PSP, indicates that the source of this event was an active region nearly 80° east of the nominal PSP magnetic footpoint. This suggests that the field lines expanded over a wide longitudinal range between the active region in the photosphere and the corona
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