Life cycle assessment of novel thermochemical - biochemical biomass-to-liquid pathways for sustainable aviation and maritime fuel production.

This paper aims to carry out an integrated Life Cycle Assessment (LCA) to evaluate the environmental performance of a novel thermochemical-biochemical biomass-to-liquid pathway for sustainable aviation and maritime biofuel production. Five scenarios are defined, consideringdifferent types of biomass feedstock and biorefinery locations, in different geographically dispersed European countries. The results indicate that the replacement of conventional aviation and maritime fuels with sustainable biofuels could reduce Greenhouse Gases (GHG) by 60-86%, based on feedstock type. When the renewable share in the electricity mix reaches 100% (in 2050), the GHG emissions will experience a great decrease (26% - 68%), compared to 2022 levels. The non-renewable energy consumption will also decrease (by 56% - 83%), with results strongly affected by the electricity mix of the European country considered. This study demonstrates that the deployment of biomass-to-jet/marine fuel pathways could favor the industrial adoption of circular economy strategies for transport biofuels production.

Identifying the performance and losses of a scroll compressor with vapour injection and R1234ze(E).

This work investigates a vapour injection scroll compressor integrated in a heat pump using the refrigerant R1234ze(E). The water-to-water heat pump was tested under a wide temperature range at the evaporator and condenser sides. The test results revealed that the performance is significantly reduced for lifts of over 30 K with the coefficient of performance being even below 2 and the maximum 2 nd law efficiency was just 28%. In order to enlighten the reasons behind such significant compressor underperformance, a semi-empirical model has been extended to include vapour injection, and a new improved modelling approach for the suction pressure drop was developed and implemented considering both the turbulent and laminar inlet flow regimes. Once the accuracy of the developed semi-empirical model was verified, the model was then adjusted to account for the R1234ze(E) operation, by fine-tuning its parameters based on the test data. The main loss mechanism identified is the high suction pressure drop, due to the high friction factor, with the inlet refrigerant flow possibly being laminar instead of turbulent. This resulted in a significant reduction of the mass flow rate and volumetric efficiency, while the standard model for suction pressure drop was not able to capture this effect.

Methods based on a semi-empirical model for simulating scroll compressors with HFC and HFO refrigerants.

The aim of this work is to evaluate three methodologies regarding semi-empirical scroll compressor modeling for different refrigerants and conduct a comparative analysis of their results and accuracy. The first step is to improve a semi-empirical model for scroll compressors based on established techniques, and further enhance the physical background of some of its sub-processes leading to more accurate predictions. Focus is then given on the compressor operation when changing the refrigerant, proposing three methods in total. The first method refers to the standard model, requiring an optimization process for the calibration of all the model parameters. The second method relies on a reference refrigerant, and also uses optimization procedures, but for the fine-tuning of a small subset of the parameters. The third method is more generalized, without the need of any optimization process for the parameters identification, when fluid change occurs, leading to a very fast approach. Το evaluate the accuracy and verify the applicability of each method also related to the necessary computational time, two scroll compressors each with three different refrigerants are considered (HFCs and HFOs and their blends). The model is evaluated with the available manufacturer data, using R134a as reference refrigerant. The results show that the first method predicts the key indicators with a very high accuracy, with the maximum discrepancy of 2.06%, 4.17% and 3.18 K for the mass flow rate, electric power and discharge temperature respectively. The accuracy of the other two methods is dropping, but within acceptable levels in most of the cases. Therefore, in cases that reduced accuracy can be accepted, the third method is preferred for compressor performance prediction when changing the refrigerant, which provides results at a small fraction of time compared with the other two methods, once the parameters are calibrated for a reference case.