Sourcing Hydrogen for the Production of Sustainable Aviation Fuels

Sustainable aviation fuels (SAFs) are the near-term technological solution to decarbonize the aviation industry sector. There are several pathways to obtain biojet fuels, which can be classified into four main categories, namely oil-to-jet, alcohol-to-jet, gas-to-jet, and sugar-to-jet. All of them share the need for hydrogen to obtain a drop-in fuel that can be blended with petroleum-based jet fuel. The hydrogen input requirements affect the life cycle greenhouse gas emissions, increase the biojet fuel cost and hinder the construction of distributed processing plants. This study addresses the problem of hydrogen sourcing in the production of SAFs through a systematic literature review. Techno-economic studies of biojet fuel production using different feedstocks and conversion pathways are analyzed focusing on the methods of hydrogen provision. The technological options used to generate the required hydrogen within the conversion process itself as well as externally, along with the main strategies to reduce the hydrogen demand are identified. The production yields and the hydrogen consumption of several SAF production pathways are compared. The jet fuel yields reach values as high as 0.66 for hydroprocessing of vegetable oils with external hydrogen provision, while they drop to 0.10 for production from lignocellulosic biomass with internal hydrogen sourcing. The results of the analysis highlight the real potential of four among the most promising routes for the production of biojet fuels when the burden related to hydrogen demand is properly taken into account

Environmental Assessment of Latent Heat Thermal Energy Storage Technology System with Phase Change Material for Domestic Heating Applications

From MDPI via Jisc Publications RouterHistory: accepted 2021-10-07, pub-electronic 2021-10-13Publication status: PublishedFunder: Engineering and Physical Sciences Research Council; Grant(s): EP/S00078X/1The emissions generated by the space and water heating of UK homes need to be reduced to meet the goal of becoming carbon neutral by 2050. The combination of solar (S) collectors with latent heat thermal energy storage (LHTES) technologies with phase change materials (PCM) can potentially help to achieve this goal. However, there is limited understanding of the environmental sustainability of LHTES technologies from a full life cycle perspective. This study assesses for the first time 18 environmental impacts of a full S-LHTES-PCM system from a cradle to grave perspective and compares the results with the most common sources of heat in UK homes. The results show that the system’s main environmental hotspots are the solar collector, the PCM, the PCM tank, and the heat exchanger. The main cause of most of the impacts is the extensive consumption of electricity and heat during the production of raw materials for these components. The comparison with other sources of household heat (biomass, heat pump, and natural gas) indicates that the S-LHTES-PCM system generates the highest environmental impact in 11 of 18 categories. However, a sensitivity analysis based on the lifetime of the S-LHTES-PCM systems shows that, when the lifetime increases to 40 years, almost all the impacts are significantly reduced. In fact, a 40-year S-LHTES-PCM system has a lower global warming potential than natural gas

Perifosine as a Potential Novel Anti-Cancer Agent Inhibits EGFR/MET-AKT Axis in Malignant Pleural Mesothelioma

PI3K/AKT signalling pathway is aberrantly active and plays a critical role for cell cycle progression of human malignant pleural mesothelioma (MMe) cells. AKT is one of the important cellular targets of perifosine, a novel bio-available alkylphospholipid that has displayed significant anti-proliferative activity in vitro and in vivo in several human tumour model systems and is currently being tested in clinical trials.We tested Perifosine activity on human mesothelial cells and different mesothelioma cell lines, in order to provide evidence of its efficacy as single agent and combined therapy.We demonstrate here that perifosine, currently being evaluated as an anti-cancer agent in phase 1 and 2 clinical trials, caused a dose-dependent reduction of AKT activation, at concentrations causing MMe cell growth arrest. In this study we firstly describe that MMe cells express aside from AKT1 also AKT3 and that either the myristoylated, constitutively active, forms of the two proteins, abrogated perifosine-mediated cell growth inhibition. Moreover, we describe here a novel mechanism of perifosine that interferes, upstream of AKT, affecting EGFR and MET phosphorylation. Finally, we demonstrate a significant increase in cell toxicity when MMe cells were treated with perifosine in combination with cisplatin.This study provides a novel mechanism of action of perifosine, directly inhibiting EGFR/MET-AKT1/3 axis, providing a rationale for a novel translational approach to the treatment of MMe

Analysis and Development of Innovative Binary Cycle Power Plants for Geothermal and Combined Geo-Solar Thermal Resources

This thesis analyzes binary cycle power plants (Organic Rankine Cycles) for electricity generation from low enthalpy geothermal resources. The objective is the maximization of the net power output by means of the proper selection of the working fluid and cycle parameters. A critical review of many studies on ORCs in the scientific literature is carried out to provide a basis for an optimization study having the exergy recovery efficiency as objective function. Two working fluids are analyzed taking into account both supercritical and subcritical pressures and different temperatures of the geothermal fluid. The application of advanced techniques derived from Pinch Analysis (HEATSEP method) allowed finding also sub-optimal solutions, corresponding to small deviations of the cycle parameters from the optimal design values. These solutions, although sub-optimal from a thermodynamic point of view, may be selected when different aspects related to the technology, economics, flexibility or safety of the system are considered. The costs of the optimal thermodynamic solutions are estimated using the module costing technique that relates all capital and operating costs to the purchased cost of equipment evaluated for some base conditions. The economic results show the impact of the geothermal fluid temperature and working fluid selection on the economics of the system. The results of this study are applied to the Stillwater real binary cycle power plant that started operating in 2009 in Nevada (USA). The power plant operates at subcritical pressures with isobutane as working fluid and uses a dry cooling system as heat rejection system. Due to the limited geothermal resource the plant net power output is much lower than expected. A detailed off-design model of the power plant is developed using the software Aspen. The model is tested and adjusted against the plant data collected during the first year of operation. After validation, the model is run to evaluate the operating parameters that maximize the annual energy production. A study is then performed to increase the performance of Stillwater geothermal binary power plant with the addition of the solar source. The combination of the high exergy solar resource with the low exergy geothermal resource could provide many benefits such as the improvement of the thermal efficiency and the increase of the power output during the day and especially during the warm season, a time when the energy production of air-cooled geothermal power plants is markedly reduced. The addition of the solar heat in the Stillwater geothermal plant restores operating conditions close to design point also in presence of reduced geothermal flow rate and temperature. The detailed off-design model of Stillwater power plant is used to carry out this hybridization study. Cycle parameters are optimized for different values of the ambient temperature and solar irradiation in order to maximize the annual energy production. Two different designs of hybrid geo-solar plants, with and without storage, are compared, and the levelized cost of electricity (LCOE) of the incremental generation from solar energy is calculated. As expected, this LCOE is quite high due to the high costs of the solar collectors and could be competitive only in presence of appropriate incentives.La tesi analizza gli impianti a ciclo binario (Organic Rankine Cycles) per generazione di elettricità da risorse geotermiche a bassa entalpia. L'obiettivo è la massimizzazione della potenza netta tramite una selezione appropriata del fluido operativo e dei parametri di ciclo. La valutazione critica di molti studi sui cicli di Rankine organici ha fornito le basi per formulare uno studio di ottimizzazione avente come funzione obiettivo il rendimento di recupero exergetico. Sono analizzati due fluidi operativi considerando sia pressioni supercritiche che subcritiche e diverse temperature del fluido geotermico. L'applicazione di tecniche avanzate derivate dalla Pinch Analysis (metodo HEATSEP) ha consentito di trovare anche soluzioni sub-ottimali, corrispondenti a piccoli scostamenti dei parametri di ciclo dai valori di progetto ottimali. Queste soluzioni, sebbene sub-ottimali da un punto di vista termodinamico, potrebbero essere scelte se venissero considerati anche aspetti legati alla tecnologia, economia, flessibilità o sicurezza del sistema. I costi delle soluzioni termodinamicamente ottimali sono quindi valutati mostrando l'impatto della temperatura del fluido geotermico e della scelta del fluido operativo sull'economia del sistema. I risultati di questo studio sono applicati all'impianto reale a ciclo binario di Stillwater che iniziò l'operazione nel 2009 in Nevada (USA). L'impianto opera a pressioni subcritiche con isobutano come fluido operativo e usa un sistema di raffreddamento ad aria. A causa della limitata risorsa geotermica la potenza netta prodotta dall'impianto è molto più bassa di quella attesa. E' stato sviluppato un modello dettagliato di fuori progetto dell'impianto usando il software Aspen. Il modello è stato validato con i dati dell'impianto raccolti nel primo anno di attività. Dopo validazione il modello è utilizzato per ottenere i parametri operativi che massimizzano la produzione energetica annuale. E' stato quindi effettuato uno studio per aumentare le prestazioni dell'impianto geotermico di Stillwater con l'aggiunta della risorsa solare. I parametri di ciclo sono ottimizzati per valori differenti della temperatura ambiente e della radiazione solare per massimizzare la produzione energetica annuale. Sono confrontate due configurazioni di ciclo ibrido, con e senza accumulo, ed è calcolato il costo dell'energia elettrica (LCOE). Come atteso, questo LCOE è abbastanza elevato a causa dei costi elevati dei collettori solari e potrebbe essere competitivo solo in presenza di incentivi appropriati

High performance integrated solar combined cycles with minimum modifications to the combined cycle power plant design

The integration of solar energy into natural gas combined cycles has been successfully demonstrated in several integrated solar combined cycles since the beginning of this decade in many countries. There are many motivations that drive investments on integrated solar combined cycles which are primarily the repowering of existing power plants, the compliance with more severe environmental laws on emissions and the mitigation of risks associated with large solar projects. Integrated solar combined cycles are usually developed as brownfield facilities by retrofitting existing natural gas combined cycles and keeping the existing equipment to minimize costs. In this work a detailed off-design model of a 390MWe three pressure level natural gas combined cycle is built to evaluate different integration schemes of solar energy which either keep the equipment of the combined cycle unchanged or include new equipment (steam turbine, heat recovery steam generator). Both power boosting and fuel saving operation strategies are analyzed in the search for the highest annual efficiency and solar share. Results show that the maximum incremental power output from solar at design solar irradiance is limited to 19MWe without modifications to the existing equipment. Higher values are attainable only including a larger steam turbine. High solar radiation-to-electrical efficiencies in the range 24\u201329% can be achieved in the integrated solar combined cycle depending on solar share and extension of tube banks in the heat recovery steam generator. Compared to power boosting, the fuel saving strategy shows lower thermal efficiencies of the integrated solar combined cycle due to the efficiency drop of gas turbine at reduced loads. Without modifications to the existing equipment the maximum solar share of the total generated electricity is only about 1%

A New Criterion to Optimize ORC Design Performance using Efficiency Correlations for Axial and Radial Turbines

Several studies on Organic Rankine Cycles (ORCs) in the literature search for the optimal cycle parameters and working fluids that maximize the net power output. Only few studies carry out a preliminary turbine design to calculate an accurate value of turbine efficiency, but this is done only after the cycle thermodynamic optimization is performed assuming a fixed and somewhat arbitrary value of turbine efficiency. Instead, a new design optimization procedure of ORCs is proposed here which embeds correlations for the design efficiency of both axial and radial turbines. The correlations are obtained from published data in the literature and use the volumetric expansion ratio (VR) and the size parameter (VH) as performance predictors. While been applied to a selected number of working fluids and single stage turbines, the procedure has a general validity being the correlations applicable to any fluid and turbine type. Results show how the turbine efficiency, and in turn the optimum cycle parameters, are influenced by the fluid properties through the turbine VH and VR values, highlighting that the procedure for working fluid selection cannot ignore the real turbine behaviour. So, the optimum design that is obtained is expected to give a behaviour much closer to reality

Solar-aided precombustion CO2 capture in natural gas combined cycles

The integration of solar energy in natural gas combined cycles has recently received much attention in the global efforts to reduce CO2 emissions. Optimum integration options have been proposed in the literature which enhance the conversion of solar thermal energy into electricity compared to solar-only power plants. The so-called \u201cIntegrated Solar Combined Cycles\u201d (ISCCs) may embed the solar heat input in the bottoming steam cycle as well as in the topping gas turbine. Another route for the efficient abatement of CO2 in natural gas combined cycles consists in the integration of hydrogen/syngas production technologies such as reforming and water-gas shift reactions. The heat required for the endothermic steam reforming reaction can be provided by burning part of the hydrogen-rich syngas or alternatively by the partial oxidation of methane and oxygen within an autothermal reformer. After CO2 removal the resulting syngas mostly containing hydrogen is burned in the gas turbine to produce electricity or may be further processed to high-purity hydrogen. In this work the integration of solar energy in natural gas combined cycles with precombustion CO2 capture is evaluated. These plants include additional high temperature heat sinks compared to a plant without CO2 capture that could be conveniently fed by solar thermal energy. Different layouts are proposed and analyzed in the search for the optimum integration. The achievable solar share and thermodynamic and environmental performance is compared against those achievable in ISCCs without CO2 capture

Analysis of Superimposed Elementary Thermodynamic Cycles: from the Brayton-Joule to Advanced Mixed (Auto-Combined) Cycles

none2The need for efficiency improvement in energy conversion systems leads to a stricter functional integration among system components. This results in structures of increasing complexity, the high performance of which are often difficult to be understood easily. To make the comprehension of these structures easier, a new approach is followed in this paper, consisting in their representation as partial or total superimposition of elementary thermodynamic cycles. Although system performance cannot, in general, be evaluated as the sum of the performance of the separate thermodynamic cycles, this kind of representation and analysis can be of great help in understanding directions of development followed in the literature for the construction of advanced energy systems, and could suggest new potential directions of work. The evolution from the simple Brayton-Joule cycle to the so called “mixed” cycles, in which heat at the turbine discharge is exploited using internal heat sinks only without using a separate bottoming section, is used to demonstrate the potentiality of the approach. Mixed cycles are named here "auto-combined cycles” to highlight the combination of different (gas and steam) cycles within the same system components.noneLAZZARETTO A.; MANENTE GLazzaretto, Andrea; Manente, Giovann