Three dimensional scattering center imaging techniques

Two methods to image scattering centers in 3-D are presented. The first method uses 2-D images generated from Inverse Synthetic Aperture Radar (ISAR) measurements taken by two vertically offset antennas. This technique is shown to provide accurate 3-D imaging capability which can be added to an existing ISAR measurement system, requiring only the addition of a second antenna. The second technique uses target impulse responses generated from wideband radar measurements from three slightly different offset antennas. This technique is shown to identify the dominant scattering centers on a target in nearly real time. The number of measurements required to image a target using this technique is very small relative to traditional imaging techniques

Vortex-induced vibration of catenary riser: reduced-order modeling and lock-in analysis using wake oscillator

A new reduced-order model capable of analyzing the vortex-induced vibration of catenary riser in the ocean current has been developed. This semi analytical-numerical approach is versatile and allows for a significant reduction in computational effort for the analysis of fluid-riser interactions. The incoming current flow is assumed to be steady, uniform, unidirectional and perpendicular to the riser plane of initial equilibrium curvatures

Integral Glass Encapsulation for Solar Arrays

Work reported was performed during the period from August 1977 to December 1978. The program objective was to continue the development of electrostatic bonding (ESB) as an encapsulation technique for terrestrial cells. Economic analyses shows that this process can be a cost-effective method of producing reliable, long lifetime solar modules. When considered in sufficient volume, both material and equipment costs are competitive with conventional encapsulation systems. In addition, the possibility of integrating cell fabrication into the encapsulation process, as in the case of the preformed cell contacts discussed in this report, offers the potential of significant overall systems cost reduction

Geothermal systems simulation: A case study

Geothermal reservoir simulation is a key step for developing sustainable and efficient strategies for the exploitation of geothermal resources. It is applied in the assessment of several areas of reservoir engineering, such as reservoir performance and re-injection programs, pressure decline in depletion, phase transition conditions, and natural evolution of hydrothermal convection systems. Fluid flow and heat transfer in rock masses, fluid-rock chemical interaction and rock mass deformation are some of the processes addressed in reservoir modelling. The case study of the Las Tres Virgenes (LTV) geothermal field (10 MWe), Baja California Sur, Mexico is presented. Three dimensional (3D) natural state simulations were carried out from emplacement and cooling of two spherical magma chambers using a conductive approach. A conceptual model of the volcanic system was developed on a lithostratigraphic and geochronological basis. Magma chamber volumes were established from eruptive volumes estimations. The thermophysical properties of the medium were assumed to correspond to the dominant rock in each lithological unit as an initial value, and further calibration was made considering histograms of experimentally obtained thermophysical properties of rocks. As the boundaries of the model lie far from the thermal anomaly, we assumed specified temperature boundaries. A Finite Volume (FV) numerical scheme was implemented in a Fortran 90 code to solve the heat equation. Static formation temperatures from well logs were used for validation of the numerical results. Good agreement was observed in those geothermal wells dominated by conductive heat transfer. For other wells, however, it is clear that conduction alone cannot explain observed behaviour, three-dimensional convective models are being implemented for future multiphysics simulations

Groundwater reinjection and heat dissipation: lessons from the operation of a large groundwater cooling system in Central London

The performance of a large open-loop groundwater cooling scheme in a shallow alluvial aquifer at a prominent public building in Central London has been monitored closely over its first 2 years of operation. The installed system provided cooling to the site continuously for a period of 9 months between June 2012 and April 2013. During this period, c. 131300 m3 of groundwater was abstracted from a single pumping well and recharged into a single injection borehole. The amount of heat rejected in this period amounts to c. 1.37 GWh. A programme of hydraulic testing was subsequently undertaken over a 3 month period between July and October 2013 to evaluate the performance of the injection borehole. The data indicate no significant change in injection performance between commissioning trials undertaken in 2010 and the most recent period of testing, as evidenced by comparison of injection pressures for given flow rates in 2010 and 2013. Continuous temperature monitoring of the abstracted water, the discharge and a number of observation wells demonstrates the evolution of a heat plume in the aquifer in response to heat rejection and subsequent dissipation of this heat during the 18 month planned cessation

Direct Use of Low Enthalpy Deep Geothermal Resources in the East African Rift Valley

Geothermal energy is already harnessed across East Africa to provide hundreds of megawatts of electricity, with significant plans for future expansion towards generation at the gigawatt scale. This power generation utilizes the high steam temperatures (typically more than 200 °C) that are available in several locations in Kenya, Ethiopia and elsewhere. The presence of these high enthalpy resources has deflected attention from the often attractive low and medium enthalpy resources present across a more extensive portion of the region. Geothermally heated water at cooler temperatures (less than 90 °C) could be widely produced by drilling shallower and cheaper boreholes than those required for power production. This low enthalpy resource could be widely exploitable throughout the Rift Valley, offering a low carbon, sustainable, reliable and commercially competitive source of heating, drying and cooling (via absorption chillers) to local farmers and growers, and for low temperature commercial and industrial uses. Applications of this type would displace expensive fossil fuels, reducing costs and carbon emissions as well as improving the region’s energy and food security. The power input for pump systems can be accommodated by relatively small generators, so direct heat projects could be beneficial to consumers in areas with no grid access