402 research outputs found
Evaluation of power generation operations in response to changes in surface water reservoir storage
We used a customized, river basin-based model of surface water rights to evaluate the response
of power plants to drought via simulated changes in reservoir storage. Our methodology
models surface water rights in 11 river basins in Texas using five cases: (1) storage decrease of
existing capacity of 10%, (2) storage decrease of 50%, (3) complete elimination of storage,
(4) storage increase of 10% (all at existing locations), and (5) construction of new reservoirs
(at new locations) with a total increase in baseline reservoir capacity for power plant cooling
of 9%. Using the Brazos River basin as a sample, we evaluated power generation operations in
terms of reliability, resiliency, and vulnerability. As simulated water storage decreases,
reliability generally decreases and resiliency and vulnerability remain relatively constant. All
three metrics remain relatively constant with increasing reservoir storage, with the exception
of one power plant. As reservoir storage changes at power plants, other water users in the
basin are also affected. In general, decreasing water storage is beneficial to other water users
in the basin, and increasing storage is detrimental for many other users. Our analysis reveals
basin-wide and individual power plant-level impacts of changing reservoir storage,
demonstrating a methodology for evaluation of the sustainability and feasibility of
constructing new reservoir storage as a water and energy management approach.Mechanical Engineerin
Can switching fuels save water? A life cycle quantification of freshwater consumption for Texas coal-and natural gas-fired electricity
Thermal electricity generation is a major consumer of freshwater for cooling, fuel extraction and air
emissions controls, but the life cycle water impacts of different fossil fuel cycles are not well understood.
Much of the existing literature relies on decades-old estimates for water intensity, particularly regarding
water consumed for fuel extraction. This work uses contemporary data from specific resource basins and
power plants in Texas to evaluate water intensity at three major stages of coal and natural gas fuel cycles:
fuel extraction, power plant cooling and power plant emissions controls. In particular, the water intensity
of fuel extraction is quantified for Texas lignite, conventional natural gas and 11 unconventional natural
gas basins in Texas, including major second-order impacts associated with multi-stage hydraulic
fracturing. Despite the rise of this water-intensive natural gas extraction method, natural gas extraction
appears to consume less freshwater than coal per unit of energy extracted in Texas because of the high
water intensity of Texas lignite extraction. This work uses new resource basin and power plant level
water intensity data to estimate the potential effects of coal to natural gas fuel switching in Texasâ power
sector, a shift under consideration due to potential environmental benefits and very low natural gas
prices. Replacing Texasâ coal-fired power plants with natural gas combined cycle plants (NGCCs) would
reduce annual freshwater consumption in the state by an estimated 53 billion gallons per year, or 60% of
Texas coal powerâs water footprint, largely due to the higher efficiency of NGCCs.Mechanical Engineerin
Valuing Distributed Energy Resources for Non-Wires Alternatives
Distributed energy resources (DER) as non-wires alternatives, regardless of
owner, have the potential to reduce system operating costs and delay system
upgrades. However, it is difficult to determine the appropriate economic signal
to incentivize DER investors to install capacity that will benefit both the DER
investors and the system operator. In an attempt to determine this co-optimal
price signal, we present a bilevel optimization framework for determining the
least cost solution to distribution system over-loads. A key output of the
framework is a spatiotemporal price signal to DER owners that simultaneously
guarantees the DER owners' required rate of return and minimizes the system
operation costs. The framework is demonstrated with a case by which the system
operator considers utility owned battery energy storage systems, traditional
system upgrades, and energy purchase from DER owners. The results show that by
valuing DER for non-wires alternatives the utility owned storage system sizes
can be reduced, less hardware upgrades are necessary, and upfront capital costs
as well as operating costs are reduced.Comment: under revie
Wasted Food, Wasted Energy: The Embedded Energy in Food Waste in the United States
This work estimates the energy embedded in wasted food annually in the United States. We calculated the energy intensity of food production from agriculture, transportation, processing, food sales, storage, and preparation for 2007 as 8080 ± 760 trillion BTU. In 1995 approximately 27% of edible food was wasted. Synthesizing these food loss figures with our estimate of energy consumption for different food categories and food production steps, while normalizing for different production volumes, shows that 2030 ± 160 trillion BTU of energy were embedded in wasted food in 2007. The energy embedded in wasted food represents approximately 2% of annual energy consumption in the United States, which is substantial when compared to other energy conservation and production proposals. To improve this analysis, nationwide estimates of food waste and an updated estimate for the energy required to produce food for U.S. consumption would be valuable
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Development of a Rooftop Collaborative Experimental Space through Experiential Learning Projects
The Solar, Water, Energy, and Thermal Laboratory
(SWEAT Lab) is a rooftop experimental space at the
University of Texas at Austin built by graduate and
undergraduate students in the Cockrell School of
Engineering. The project was funded by the Texas State
Energy Conservation Office and the Universityâs Green
Fee Grant, a competitive grant program funded by UT
Austin tuition fees to support sustainability-related projects
and initiatives on campus. The SWEAT Lab is an on-going
experiential learning facility that enables engineering
education by deploying energy and water-related projects.
To date, the lab contains a full weather station tracking
weather data, a rainwater harvesting system and rooftop
garden.
This project presented many opportunities for students to
learn first hand about unique engineering challenges. The
lab is located on the roof of the 10 story Engineering
Teaching Center (ETC) building, so students had to design
and build systems with constraints such as weight
limitations and wind resistance. Students also gained
experience working with building facilities and
management for structural additions, power, and internet
connection for instruments.
With the Birdâs eye view of UT Austin campus, this unique
laboratory offers a new perspective and dimension to
applied student research projects at UT Austin.Cockrell School of Engineerin
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Workshop Report: Developing a Research Agenda for the Energy Water Nexus
The
energy
water
nexus
has
attracted
public
scrutiny
because
of
the
concerns
about
their
interdependence
and
the
possibility
for
cascading
vulnerabilities
from
one
system
to
the
other.
There
are
trends
toward
more
water-Ââintensive
energy
(such
as
biofuels
,
unconventional
oil
and
gas
production,
and
regulations
driving
more
water
consumption
for
thermoelectric
power
production
)
and
more
energy-Ââintensive
water
(such
as
desalination,
or
deeper
ground
water
pumping
and
production).
In
addition
demographic
trends
of
population
and
economic
growth
will
likely
drive
up
total
and
per
capita
water
and
energy
demand,
and
due
to
climate
change
related
distortions
of
the
hydrologic
cycle,
it
is
expected
that
the
existing
interdependencies
will
be
come
even
more
of
a
concern.
Therefore,
developing
a
research
agenda
and
strategy
to
mitigate
potential
vulnerabilities
and
to
meet
economic
and
environmental
targets
for
efficiently
using
energy
and
water
would
be
very
worthwhile.
To
address
these
concerns,
the
National
Science
Foundation
(NSF)
sponsored
a
workshop
on
June
10-Ââ11,
2013
in
Arlington,
VA
(at
NSF
headquarters)
to
bring
together
technical,
academic,
and
industry
experts
from
across
the
country
to
help
develop
such
a
research
agenda.
The
workshop
was
sponsored
by
NSF
Grant
Number
CBET
1341032
from
the
Division
of
Chemical,
Bioengineering,
Environmental
and
Transport
Systems.
Supporting
programs
were:
Thermal
Transport
Processes,
Environmental
Sustainability,
and
Environmental
Engineering.Center for Research in Water Resource
Implementation of Brackish Groundwater Desalination Using Wind-Generated Electricity: A Case Study of the Energy-Water Nexus in Texas
Growing populations and periodic drought conditions have exacerbated water stress in many areas worldwide. In response, some municipalities have considered desalination of saline water as a freshwater supply. Unfortunately, desalination requires a sizeable energy investment. However, renewable energy technologies can be paired with desalination to mitigate concern over the environmental impacts of increased energy use. At the same time, desalination can be operated in an intermittent way to match the variable availability of renewable resources. Integrating wind power and brackish groundwater desalination generates a high-value product (drinking water) from low-value resources (saline water and wind power without storage). This paper presents a geographically-resolved performance and economic method that estimates the energy requirements and profitability of an integrated wind-powered reverse osmosis facility treating brackish groundwater. It is based on a model that incorporates prevailing natural and market conditions such as average wind speeds, total dissolved solids content, brackish well depth, desalination treatment capacity, capital and operation costs of wind and desalination facilities, brine disposal costs, and electricity and water prices into its calculation. The model is illustrated using conditions in Texas (where there are counties with significant co-location of wind and brackish water resources). Results from this case study indicate that integrating wind turbines and brackish water reverse osmosis (BWRO) systems is economically favorable in a few municipal locations in West TexasMechanical Engineerin
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Air quality impacts of using overnight electricity generation to cahrge plug-in hybrid electric vehicles for daytime use
The air quality impacts of replacing 20% of the gasoline powered light duty vehicle miles
traveled with plug-in hybrid electric vehicles (PHEVs) in the region served by the Pennsylvania,
New Jersey, Maryland classic grid are examined. Unutilized, base-load nighttime electricity
generating capacity is assumed to charge PHEVs that would subsequently be used during urban
commutes. The net impact of this scenario on the emissions of precursors to the formation of
ozone is an increase in nitrogen oxide (NOx), volatile organic compound (VOC) and CO
emissions from electricity generating units during nighttime hours, and a greater decrease in
NOx, VOC and CO from mobile emissions in urban areas during daytime hours. The changes
in maximum daily 8 h ozone concentrations, predicted using a regional photochemical model
(CAMx), are decreases in ozone concentrations between 2 and 6 ppb that are widespread across
the urban areas, and increases in ozone concentrations of up to 8 ppb in highly localized areas.
Air quality indicators beyond maximum daily ozone concentration are also evaluated, and in
general indicate air quality improvements associated with the use of PHEVs. However, a
limited number of air quality indicators worsened with the use of PHEVs, suggesting that
overall impacts of the use of PHEVs will be complex.Mechanical Engineerin
Where does solar-aided seawater desalination make sense? A method for identifying sustainable sites
AbstractGlobal water planners are increasingly considering seawater desalination as an alternative to traditional freshwater supplies. Since desalination is both expensive and energy intensive, taking advantage of favorable natural and societal conditions while siting desalination facilities can provide significant financial and environmental returns. Currently, policy makers do not use a location-specific integrated analytical framework to determine where natural and societal conditions are conducive to desalination. This analysis seeks to fill that gap by demonstrating a multi-criteria, geographically-resolved methodology for identifying suitable regions for desalination infrastructure where 1) available renewable resources can offset part of the fossil energy load; 2) feedwater characteristics reduce the total energy needed for desalination; and 3) human populations have capacity and willingness to pay for desalinated water. This work demonstrates the method with a quantitative global analysis that identifies favorable sites for solar-aided seawater reverse osmosis desalination (SWRO) based on specific target criteria. Location-based data about natural conditions (solar insolation, ocean salinity, and ocean temperature) are integrated and mapped with social indicators (water stress, prevailing water prices, and population) to identify regions where solar-aided SWRO has the highest potential. This work concludes that water-stressed tropical and subtropical cities show the highest potential for economically sustainable solar-aided SWRO
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