Browsing by Subject "Climate change adaptation"

Modeling studies predict that droughts and hotter water and air temperatures caused by climate warming will reduce the efficiency (η) of thermoelectric plants by 0.12-0.45% for each 1°C of warming. In Chapter 2, we evaluate these predictions using historical performance data for 39 open- and closed-loop, coal and natural gas plants from across the U.S., which operated under daily and seasonal temperature fluctuations multiples greater than future average warming projections. Seven to fourteen years of hourly water (Tw), dry-bulb air (Ta) and wet-bulb air (Twb) temperature recordings collected near each plant are regressed against efficiency to attain estimates of ∆η per 1°C increase. We find reductions in η with increased Tw (for open-loop plants) up to an order of magnitude less than previous estimates. We also find that changes in η associated with changes in Ta (open-loop plants) or Twb (closed-loop plants) are not only smaller than previous estimates but also variable, i.e. η rises with Ta or Twb for some plants and falls for others. Our findings suggest that thermoelectric plants, particularly closed-loop plants, should be more resilient to climate warming than previously expected. Moreover, our results raise questions regarding the relative impacts of climate change-induced drops in water availability versus increases in ambient temperatures on the ability of thermoelectric power plants to generate power.

In Chapter 3, we explore and compare the effects of decreased water availability and increased water temperature on once-through power plants, which are expected to suffer more of the impacts of climate change than recirculating plants. Currently, little is known about which of the constraints, water temperature or availability, has a greater impact on power generation, and how these impacts and trends may vary with plant age, nameplate capacity, fuel type, generator technology, and location. We apply seven years of historical data from 20 once-through coal and natural gas plants into a thermoelectric power generation model to simulate how changes in various external parameters (water temperature, temperature regulations, and water availability) can affect the usable capacity of these plants. We find that depending on the plant, streamflow can contribute to 0-35% of the capacity reduction, while temperature can contribute 0-17% and regulations 48-100%. We also observe that power plants located on smaller water bodies (i.e., <3000 m^3/s in this study) are more likely to be severely impacted in future climate extreme events than plants located in other areas, regardless of power plant technology.

The fourth and final chapter of this dissertation diverges from the previous chapters and examines the processes that influence the evolution of fluvio-deltaic systems at passive continental margins. Depositional and erosional patterns that were previously believed to be entirely produced by externally-derived (allogenic) processes are now being recognized as patterns that can develop from autogenic interactions (e.g., channel avulsion and delta lobe switching). In this work, we are interested in understanding how traditional, allogenically-based interpretations of these systems change when we incorporate the impacts of autogenic processes. We introduce a novel first-order numerical basin-filling model to address this question. This model differs from previous work in that external inputs (i.e., subsidence rate, base level change, sediment supply) as well as streamwise and cross-stream transport coefficients can be adjusted to simulate basins that are dominated by allogenic processes (i.e., subsidence, eustasy, and sediment supply), laterally-moving autogenic processes, or a combination of both. Because of this, the model can be used to track how autogenic and allogenic processes interact to impact the evolution of fluvio-deltaic systems as more and more autogenic forcing is introduced. Our ability to identify, separate, and understand the geomorphic and stratigraphic signals of internally-derived processes from those of external controls is critical for better understanding shelf development.