Tobias Erhart

Influence of Condenser Conditions on Organic Rankine Cycle Load Characteristics

A 7 MWth combined heat and power plant (CHP) based on an organic Rankine cycle (ORC) with 5.3 MWth and 1 MWel nominal output is analyzed. A district heating system serves as heat sink; the entire system is heat-led. Two examples for winter and summer operation are shown. The observed characteristics of the condenser are compared to results of a theoretical model. Variable mass flows, temperature levels (72 °C–95 °C) and temperature spreads result in varying condensation temperatures and pressure levels in the condenser (90 mbar to 150 mbar). High mass flows on the secondary side and related low temperature spreads improve the heat transfer and increase the condensation rate in the condenser. The monitoring data support the findings of a steady-state condenser model. As a consequence, advantageous load profiles according to the pressure characteristic of the system can be reached. Live steam pressure, pressure difference across the turbine, and flow rate increase. The effect on the electric efficiency is one percentage point in summer and 1.5 percentage points in winter, which translates to a difference in the electric yield of the cycle of about 10%. Furthermore, the data show that the transient sink conditions cause unsteady operation for the entire cycle.

Auf dem Weg zum nachhaltigen Stadtviertel

Wie die nachhaltige Stadt der Zukunft aussehen konnte, zeigt der Stadtteil „Scharnhauser Park“ in Ostfildern bei Stuttgart. In diesem Quartier versuchen Wissenschaftler und Investoren, einen ganzen Stadtteil so optimal wie moglich nach nachhaltigen Gesichtspunkten zu gestalten.

Low Energy City Quarters with High Renewable Fractions: Monitoring Results and Potential for Replication

The paper presents monitoring results from the implementation of energy efficient buildings, renewable energy supply systems and energy management in a sustainable neighborhood in Germany. The whole quarter has low energy standard buildings, which have been monitored for heating and electricity consumption. About 80% of the heating energy demand and 50% of the electricity consumption of the whole area is supplied by a wood fired co-generation plant with 1 MW electrical output and 5.3 MW thermal power output. In summer the heat from the network is used for decentralized absorption cooling in one of the office buildings. The main performance results of this monitored area are presented and the potential for replication are discussed.