| Abstract |
Inflow radial turbines, expanders and turboexpanders were first developed in the early 1930s. The first industrial application followed in the years 1934/35 in an air separation process. From the 1950s onwards, expanders were utilized in cryogenic plants for natural gas processing. In the early 1980s, the Mammoth Lakes geothermal plant in California, USA, became the first large-scale geothermal Organic Rankine Cycle (ORC) plant to utilize expanders in an ORC cycle. The successful implementation of expanders in the Mammoth Lakes project led to another successful and even larger geothermal ORC plant with turboexpanders: the Steam Boat plant in Nevada, USA, in the early 1990s. Since then, many other large-scale geothermal ORC plants have installed radial inflow turbines throughout the world. Turboexpanders have several unique design features that are ideal for applications in geothermal ORC plants. The inflow radial expander is a variable geometry turbine able to cope with the types of variations inherent to any geothermal power plant. A turboexpander with variable Inlet Guide Vanes (IGV) is perfectly suited to handle geothermal resource flow or temperature fluctuations in an efficient manner. Furthermore, daily or seasonal variations in ambient temperature can be managed with high efficiency in an ORC plant equipped with an inflow radial turbine. Temperature variations, in particular, are a major issue and can result in poor performance in other types of turbines, including axial turbines. This presentation covers the basic design, unique features and performance parameters of radial inflow turbines in geothermal ORC plants. We also provide the comparative results from a simulation study for cumulative annual electricity production by an axial and radial turbine. |