105 research outputs found
Temperature Effects on Biomass and Regeneration of Vegetation in a Geothermal Area.
Understanding the effects of increasing temperature is central in explaining the effects of climate change on vegetation. Here, we investigate how warming affects vegetation regeneration and root biomass and if there is an interactive effect of warming with other environmental variables. We also examine if geothermal warming effects on vegetation regeneration and root biomass can be used in climate change experiments. Monitoring plots were arranged in a grid across the study area to cover a range of soil temperatures. The plots were cleared of vegetation and root-free ingrowth cores were installed to assess above and below-ground regeneration rates. Temperature sensors were buried in the plots for continued soil temperature monitoring. Soil moisture, pH, and soil chemistry of the plots were also recorded. Data were analyzed using least absolute shrinkage and selection operator and linear regression to identify the environmental variable with the greatest influence on vegetation regeneration and root biomass. There was lower root biomass and slower vegetation regeneration in high temperature plots. Soil temperature was positively correlated with soil moisture and negatively correlated with soil pH. Iron and sulfate were present in the soil in the highest quantities compared to other measured soil chemicals and had a strong positive relationship with soil temperature. Our findings suggest that soil temperature had a major impact on root biomass and vegetation regeneration. In geothermal fields, vegetation establishment and growth can be restricted by low soil moisture, low soil pH, and an imbalance in soil chemistry. The correlation between soil moisture, pH, chemistry, and plant regeneration was chiefly driven by soil temperature. Soil temperature was negatively correlated to the distance from the geothermal features. Apart from characterizing plant regeneration on geothermal soils, this study further demonstrates a novel approach to global warming experiments, which could be particularly useful in low heat flow geothermal systems that more realistically mimic soil warming
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The effect of expansion-ratio limitations on positive-displacement, total-flow geothermal power systems
Combined steam-turbine/positive-displacement engine (PDE) geothermal power systems are analyzed thermodynamically and compared with optimized reference flash-steam plants. Three different configurations of combined systems are considered. Treated separately are the cases of self-flowing and pumped wells. Two strategies are investigated that help overcome the inherent expansion-ratio limitation of PDE's: pre-flashing and pre-mixing. Parametrically-obtained results show the required minimum PDE efficiency for the combined system to match the reference plant for various sets of design conditions
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Minutes of the fifth meeting of the centers for the analysis of thermal-mechanical energy conversion concepts
The following are included: agenda, list of participants, executive summary, and approved minutes. The appendices include the figures for some of the discussions at the meeting and drafts of contributions to the Sourcebook on the Production of Electricity from Geothermal Energy. (MHR
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Geothermal energy as a source of electricity. A worldwide survey of the design and operation of geothermal power plants
An overview of geothermal power generation is presented. A survey of geothermal power plants is given for the following countries: China, El Salvador, Iceland, Italy, Japan, Mexico, New Zealand, Philippines, Turkey, USSR, and USA. A survey of countries planning geothermal power plants is included. (MHR
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Proceedings of the Workshop on Geothermal Reservoir Engineering
An experimental simulation of an actual steam-water geothermal well based on field data obtained in New Zealand is carried out in a two-phase flow facility using dichlorotetrafluoroethane, known commercially as refrigerant 114. The simulation of steam-water flow is accomplished by a similarity theory which is achieved by using appropriate dimensionless numbers; namely, the Mach, Froude, and Reynolds numbers at the flashing front. The theory is used to scale the flow properties from that of water to that of refrigerant 114 in the two-phase region, and permits the prediction of steam-water characteristics in a flowing well, under much reduced pressure and temperature levels. Two experimental series were conducted to confront the similarity theory with actual measurements from a flowing well with significant noncondensable gases. Experimental results using refrigerant 114 indicate that the pressure distribution along the pipe can be predicted accurately in the two-phase region of a geothermal well
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Two phase flow in geothermal systems. Bi-monthly progress report, July 16-September 15, 1985
Preliminary findings of one of the early test runs of two newly constructed quick-closing valves (QCVs) are presented. The purpose was to see whether the QCVs could be activated simultaneously and closed rapidly without causing excessive over-pressure in the test section
Global Dynamics of Three Anticompetitive Systems of Difference Equations in the Plane
We investigate the global dynamics of several anticompetitive systems of rational difference equations which are special cases of general linear fractional system of the forms ., where all parameters and the initial conditions are arbitrary nonnegative numbers, such that both denominators are positive. We find the basins of attraction of all attractors of these systems
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