Abstract
In contrast to the current trend of converting waste heat into electricity in the small power range below 100 kWel by means of an ORC plant, the authors are pursuing the concept of a micro steam power plant equipped with a micro turbine. Water avoids many of the problems often associated with organic working fluids, such as flammability, toxicity, greenhouse gas effect and high fluid costs. However, water vapor makes turbine design more challenging. The physical reasons for this are repeated, and thereby it becomes clear why a velocity compounded two wheel Curtis turbine has been chosen. The used in-house 1D turbine design tool is briefly introduced. More focus is put on the shortcomings of the implemented 1D loss model and their negative impact on the current turbine design. Consequently, the authors continued actual turbine design by a parameterized approach in 3D CAD/CFD. This approach is explained, and finally, the CFD flow field and the performance maps of the designed turbine are discussed. The turbine is currently under construction and will be installed in 2022 in a waste heat recovery (WHR) plant in Nuremberg/Germany.
Highlights
Waste heat recovery (WHR) is an important building block towards an increase in energy efficiency in industry and for a successful energy transition
In contrast to the current trend of converting waste heat into electricity in the small power range below 100 kWel by means of an Organic Rankine cycle (ORC) plant, the authors are pursuing the concept of a micro steam power plant equipped with a micro turbine
In large Combined Cycle Power Plants (CCPP), a steam turbine reuses the waste heat of the upstream gas turbine (500 - 600 °C), which leads to an overall electric efficiency of more than 60% [3]
Summary
Waste heat recovery (WHR) is an important building block towards an increase in energy efficiency in industry and for a successful energy transition. Assuming a conversion efficiency of about 10%, which is realistic for small WHR units, 8 TWh per year could be extracted. This is the annual electricity production of a 1000 MW steam power plant. The maximum cycle temperatures of ORC are limited to 300-350 °C due to the danger of degradation of the working fluid. The major goal of the current project is to reduce specific costs (€/kWel) of the existing WHR system [5]
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