Andrew Swift

Desalination coupled with salinity-gradient solar ponds

Thermal desalination by salinity-gradient solar ponds (SGSP) is one of the most promising solar desalination technologies. Solar ponds combine solar energy collection with long-term storage and can provide reliable thermal energy at temperature ranges from 50 to 90°C. Solar-pond-powered desalination has been studied since 1987 at the El Paso Solar Pond Project, El Paso, Texas. From 1987 to 1992, the research mainly focused on the technical feasibility of thermal desalination coupled with solar ponds. Since 1999, the research has focused on long-term reliability, improvement of thermodynamic efficiency, and economics. During this period, a small multi-effect, multi-stage flash distillation (MEMS) unit, a membrane distillation unit, and a brine concentration and recovery system (BCRS) were tested over a broad range of operating conditions. The most important variables for the MEMS operation were flash range, concentration level of reject brine, and circulation rate of the first effect. The brine concentration and recovery system is part of the goal of developing a systems approach combining salinity-gradient solar pond technology with multiple process desalination and brine concentration. This systems approach, called zero discharge desalination, proposes concentrating brine reject streams down to near NaCl saturated solutions and using the solution to make additional solar ponds. In addition to presenting the test results on the MEMS and BCRS units, this paper also presents a summary of solar pond operation experiences obtained from the 16-year operation at the El Paso solar pond.

Dynamic LES Modeling of a Diurnal Cycle

Abstract The diurnally varying atmospheric boundary layer observed during the Wangara (Australia) case study is simulated using the recently proposed locally averaged scale-dependent dynamic subgrid-scale (SGS) model. This tuning-free SGS model enables one to dynamically compute the Smagorinsky coefficient and the subgrid-scale Prandtl number based on the local dynamics of the resolved velocity and temperature fields. It is shown that this SGS-model-based large-eddy simulation (LES) has the ability to faithfully reproduce the characteristics of observed atmospheric boundary layers even with relatively coarse resolutions. In particular, the development, magnitude, and location of an observed nocturnal low-level jet are depicted quite well. Some well-established empirical formulations (e.g., mixed layer scaling, spectral scaling) are recovered with good accuracy by this SGS parameterization. The application of this new-generation dynamic SGS modeling approach is also briefly delineated to address several pr...

Topics in Gradient Maintenance and Salt Recycling in an Operational Solar Pond

Since 1986, the 3355 m{sup 2} salt gradient solar pond facility in El Paso, Texas, has operated with a temperature difference between the upper and lower zones of 55 to 75{degrees}C while delivering industrial process heat, grid-connected electrical power, and thermal energy for the experimental production of desalted water. Because the El Paso solar pond is an inland facility, it is necessary to recycle the salt in a sustainable salt management system. A method that uses the main pond surface for initial brine concentration and short-term storage was developed after it became evident that the original evaporation pond system was undersized. This paper examines the method for brine concentration and storage, the effects of a brine storage zone on pond operation, and the installation of an enhanced evaporation net system and an automatic scanning injection system. A short description of the performance history and current status of the project is also included.

Design and implementation of a fuzzy logic yaw controller

This paper describes a fuzzy logic controller (FLC) designed and implemented to control the yaw angle of a 10 kW fixed speed teetered-rotor wind turbine presently being commissioned at the University of Texas at El Paso. The technical challenge of this project is that the wind turbine represents a highly stochastic nonlinear system. The problems associated with the wind turbine yaw control are of a similar nature as those experienced with position control of high inertia equipment like tracking antenna, gun turrets, and overhead cranes. Furthermore, the wind turbine yaw controller must be extremely cost-effective and highly reliable in order to be economically viable compared to the fossil fueled power generators.