System Description

A geothermal hydrothermal system consists of a geothermal reservoir, wells, and a power plant. "Hydrothermal" means that the geothermal reservoir contains copious amounts of steam or hot water that can be brought to the surface.

A representative system using a water-cooled flashed-steam power plant is shown in Figure 1. The system include s technical processes to find reservoirs (exploration), to measure and manage reservoirs, and to match power plant designs to the characteristics of reservoirs. The geothermal reservoir contains hot aqueous fluids. The fluids ar e produced through wells similar to oil wells, and piped to the power plant. Geothermal steam or vaporized secondar y working fluids drive a turbine-generator to make electricity. Waste heat is ejected to the atmosphere through condensers and cooling towers. Remnant geothermal liquids, including any excess condensate, are pumped back int o the reservoir through injection wells. If present, non-condensible gases are removed from the system by gas ejectio n equipment and released to the atmosphere after any treatment mandated by emission regulations. Some emissio n control systems may produce sludges or solids that are disposed of in landfills. The nominal size characterized her e is 50 MWe, the size commonly used by industry for system comparisons. Real-world system sizes range from 0.5 to 180 MWe.

Figure 1. Geothermal hydrothermal electric system with flashed steam power plant schematic.

The technology design, performance, and cost of these systems are markedly affected by the reservoir temperature . In general, the higher the temperature, the lower the cost, because higher temperature fluids contain more availabl e work. To reflect that variation, this Technology Characterization (TC) includes systems useful for high-temperatur e reservoirs (flashed-steam systems) a nd for moderate-temperature reservoirs ("binary" systems). Substantial detail about current performance and costs under a wide variety of reservoir conditions and power plant technologies is availabl e from the recent DOE/EPRI Next Generation Geothermal Power Plant (NGGPP) study, from which much of th e information in this TC is drawn [1]. Additional general background information on geothermal electric technologie s and resources can be found in [2] and [3].

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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