The results in this work show the influence of long-term operation on the decomposition of working fluids in eight different organic rankine cycle (ORC) power plants (both heat-led and electricity-led) in a range of 900 ${\mathrm{kW}}_{\mathrm{el}}$ to 2 ${\mathrm{MW}}_{\mathrm{el}}$ . All case study plants are using octamethyltrisiloxane (MDM) as a working fluid; the facilities are between six to 12 years old. Detailed analyses, including the fluid distribution throughout the cycle, are conducted on one system. All presented fluid samples are analyzed via head space gas chromatography mass spectrometry (HS-GC-MS). Besides the siloxane composition, the influence of contaminants, such as mineral oil-based lubricants (and their components), is examined. In most cases, the original working fluid degrades to fractions of siloxanes with a lower boiling point (low boilers) and fractions with a higher boiling point (high boilers). As a consequence of the analyses, a new fluid recycling and management system was designed and tested in one case study plant (Case Study #8). Pre-post comparisons of fluid samples prove the effectiveness of the applied methods. The results show that the recovery of used working fluid offers an alternative to the purchase of fresh fluid, since operating costs can be significantly reduced. For large facilities, the prices for new fluid range from € 15 per liter (in 2006) to € 22 per liter (in 2013), which is a large reinvestment, especially in light of filling volumes of 4000 liters to 7000 liters per unit. Using the aforementioned method, a price of € 8 per liter of recovered MDM can be achieved.

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.

Controlled natural ventilation in office buildings can ensure the indoor thermal comfort while reducing the life cycle energy consumption for ventilation, compared to mechanical ventilation systems (e.g. HVAC). Natural ventilation is mostly used in moderate climate zones where air conditioning is not a standard. During intermediate seasons, buildings with HVAC systems can additionally use natural ventilation to reduce energy consumption. However, in dense urban areas, natural ventilation can be problematic in terms of acoustic comfort. Here, a box-type window can serve as a compromise between thermal and acoustic comfort. Due to the more complex handling of the box-type window, an automated (electric driven) novel box-type window approach was developed within the imaF project, a part of the iCity initiative. The following article describes the basics of automated natural ventilation, acoustic characterization as well as architectural integration of this window type and the optimization of the airflow through box-type windows. The results show that the proposed geometry can provide sound insulation while providing an appropriate air exchange rate.