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Abstract A Triangle Cycle with a piston engine expansion unit is used to convert low temperature heat into electrical energy. In this process, the isentropic efficiency of the expansion unit is considered to be unknown, and a theoretical approach for the calculation of isentropic efficiency is presented. A number of influences are taken into account – dead volume, residual mass, liquid injection performance and wall heat transfer. Various working fluids are investigated in a wide range of temperatures (333K–573K), engine speeds (5 Hz–30 Hz) and stroke volumes (0.1 L–50 L). The isentropic efficiency of water as working fluid is in the range of 0.75–0.88 and drops significantly for high stroke volumes and engine speeds. In general, injection mass has the most impact on isentropic efficiency because it influences dead volume and injection performance. The injection mass increases with vapor density and therefore is significantly influenced by working fluid and temperatures. The Triangle Cycle is compared with Organic Rankine Cycles by using determined isentropic efficiency. The exergetic efficiency of the Triangle Cycle using water is up to 35–70% higher than that of supercritical Organic Rankine Cycles in situations with a heat source temperature of up to 450K.

The demand for gas turbines with increasing power and efe ciency calls for extremely high temperatures in the hot-gas sections of the engines. These temperatures can only be realized by employing sophisticated cooling schemes. Inadequate cooling may result in excessive material temperatures with reduced reliability and a lifetime of those parts subjected to the hot gas. Based on a survey of the different cooling techniques employed in modern gasturbineenginesandtheirapplicationin gasturbinecombustors, aswellasturbinecomponents,modernaspects and future developments are discussed. Results from laboratory experiments that help to understand the physical phenomena arepresented, as well as theoretical analyses. Thepossibleuse of ceramicmaterialsisdemonstrated by means of tests carried out at the Institut f ¨ ur Thermische Str ¨ omungsmaschinen, University of Karlsruhe. Besides describing current techniques, new developments are assessed and goals for future research are discussed.

The design and assessment of net-zero buildings commonly focus exclusively on the operational phase, ignoring the embodied environmental impacts over the building life cycle. An analysis is presented on the consequences of integrating embodied impacts into the assessment of the environmental advantageousness of net-zero concepts. Fundamental issues needing consideration in the design process - based on the evaluation of primary energy use and related greenhouse gas emissions - are examined by comparing three net-zero building design and assessment cases: (1) no embodied impacts included, net balance limited to the operation stage only; (2) embodied impacts included but evaluated separately from the operation stage; and (3) embodied impacts included with the operation stage in a life cycle approach. A review of recent developments in research, standardization activities and design practice and the presentation of a case study of a residential building in Norway highlight the critical importance of performance indicator definitions and system boundaries. A practical checklist is presented to guide the process of incorporating embodied impacts across the building life cycle phases in net-zero design. Its implications are considered on overall environmental impact assessment of buildings. Research and development challenges, as well as recommendations for designers and other stakeholders, are identified.

AbstractImproving the long-term stability of perovskite solar cells is critical to the deployment of this technology. Despite the great emphasis laid on stability-related investigations, publications lack consistency in experimental procedures and parameters reported. It is therefore challenging to reproduce and compare results and thereby develop a deep understanding of degradation mechanisms. Here, we report a consensus between researchers in the field on procedures for testing perovskite solar cell stability, which are based on the International Summit on Organic Photovoltaic Stability (ISOS) protocols. We propose additional procedures to account for properties specific to PSCs such as ion redistribution under electric fields, reversible degradation and to distinguish ambient-induced degradation from other stress factors. These protocols are not intended as a replacement of the existing qualification standards, but rather they aim to unify the stability assessment and to understand failure modes. Finally, we identify key procedural information which we suggest reporting in publications to improve reproducibility and enable large data set analysis.

Abstract We propose a novel transparent electrode consisting of silver (Ag)–aluminum doped zinc oxide (AZO)–nickel (Ni) deposited at room temperature on glass and polyethylene terephthalate (PET) for flexible organic photovoltaics. The electrode combines the high electrical conductivity and mechanical ductility of Ag, the transparency and antireflection of AZO and the high work function and stability of Ni. Environmental stability results confirmed that the electrode maintains its optical and electrical properties at both elevated temperature (500 °C) and under damp heat conditions (85 °C and 85% relative humidity). To demonstrate its functional potential, the electrode has been used as the transparent anode in an organic solar cell (OSC), which shows an efficiency of 2.6%, very close to the value (2.9%) obtained in a similar cell using the widely used indium tin oxide (ITO). With respect to ITO, the proposed transparent electrode has several advantages, including mechanical flexibility, room temperature processing and low cost.

Thermoacoustic technology emerges as a sustainable and low-carbon method for energy conversion, leveraging environmentally friendly working mediums and independence from electricity. This study presents the development of a multimode heat-driven thermoacoustic system designed to utilize medium/low-grade heat sources for room-temperature cooling and heating. We constructed both a simulation model and an experimental prototype for a single-unit direct-coupled thermoacoustic system, exploring its performance in heating-only, cooling-only, and hybrid heating and cooling modes. Internal characteristic analysis including an examination of internal exergy loss and a distribution analysis of key parameters was first conducted in the hybrid cooling and heating mode. The results indicated a positive-focused traveling-wave-dominant acoustic field within the thermoacoustic core unit, enhancing energy conversion efficiency. The output system performance was subsequently tested under different working conditions in the heating-only and cooling-only modes. A maximum output heating power of 2.3 kW and a maximum COPh of 1.41 were observed in the heating-only mode. Meanwhile, a cooling power of 748 W and a COPc of 0.4 were obtained in the typical cooling condition at 7 °C when operating in cooling-only mode. These findings underscore the promising potential of thermoacoustic systems for efficiently utilizing medium/low-grade heat sources for cooling and/or heating applications in the future.