With the expected further electrification of society, a greater electricity demand is to be expected, requiring improved flexibility. One proposal that meets these demands is the adaptation of the current district heating power plants by adding condensing tail turbines. Condensing tail turbines allow for further expansion of steam. A simple economic analysis showed that implementing a condensing tail with the ability to bypass 50% of the district heating resulted in an additional 2.36 million SEK (215 thousand €) in income per winter. The condensing tail turbine lacks research, especially its control strategy, leading to the novel part-load study for both a 100% and 50% capacity condensing tail of both a single- and double-flow type. For the full-load condensing tail, each bypass fraction above 0.6, meaning a 60% reduction in district heating load, showed a clear optimum which would give up to 173.5 kW gain in electricity production from adjusting the control strategy. The total gain in power from bypassing 90% of steam from the condensers amounted to 3.13 MW and 3.17 MW for the single- and double-flow turbines, respectively. A 50% capacity condensing tail showed a smaller difference, resulting in 1.7 MW for both.
Mohammed et al. (Thu,) studied this question.