Optimisation of a high-efficiency solar-driven organic rankine cycle for applications in the built environment

Energy security, pollution and sustainability are major challenges presently facing the international community, in response to which increasing quantities of renewable energy are to be generated in the urban environment. Consequently, recent years have seen a strong increase in the uptake of solar technologies in the building sector. In this work, the potential of a solar combined heat and power (CHP) system based on an organic Rankine cycle (ORC) engine is investigated in a domestic setting. Unlike previous studies that focus on the optimisation of the ORC subsystem, this study performs a complete system optimisation considering both the design parameters of the solar collector array and the ORC engine simultaneously. Firstly, we present thermodynamic models of different collectors, including flat-plate and evacuated-tube designs, coupled to a non-recuperative sub-critical ORC architecture that delivers power and hot water by using thermal energy rejected from the engine. Optimisation of the complete system is first conducted, aimed at identifying operating conditions for which the power output is maximised. Then, hourly dynamic simulations of the optimised system configurations are performed to complete the system sizing. Results are presented of: (i) dynamic 3-D simulations of the solar collectors together with a thermal energy storage tank, and (ii) of an optimisation analysis to identify the most suitable working fluids for the ORC engine, in which the configuration and operational constraints of the collector array are considered. The best performing working fluids (R245fa and R1233zd) are then chosen for a whole-system annual simulation in a southern European climate. The system configuration combining an evacuated-tube collector array and an ORC engine is found to be best-suited for electricity prioritisation, delivering an electrical output of 3,605¿kWh/year from a 60¿m2 collector array. In addition, the system supplies 13,175¿kWh/year in the form of domestic hot water, which is equivalent to more than 6 times the average annual household demand. A brief cost analysis and comparison with photovoltaic (PV) systems is also performed, where despite the lower PV investment cost per kWel, the levelised energy costs of the different systems are found to be similar if the economic value of the thermal output is taken into account. Finally, a discussion of the modelled solar-CHP systems results shows how these could be used for real applications and extended to other locationsPeer ReviewedPostprint (updated version

The role of Practice in Facilitating Consumer Value Co-Creation in the Higher Education Sector

Service-Dominant logic provides a framework for refinements in the concepts of valuecreation and co-creation between multiple actors. Moreover, S-D logic provides a shiftfrom outcome to process by arguing that value is not created and delivered in terms ofoutput but rather co-created in a process. Recently, the interest has focused on HigherEducation and how value is co-created between actors in Higher Education. However,it is not yet known, whether the practices within value are co-created in the HigherEducation. Drawing on S-D logic framework and practice theory, the aim of this paperis to develop and understand how practices in Higher Education such as interactingmay offer opportunities to facilitate co-creation and contribute to value in-use in thehigher education sector

Off-design operation of ORC engines with different heat exchanger architectures in waste heat recovery applications

Organic Rankine cycle (ORC) engines in waste-heat recovery applications experience variable heat-source conditions (i.e. temperature and mass flow rate variations). Therefore maximising the ORC system performance under off-design conditions is of key importance, for the financial viability and wider adoption of these systems. In this paper, the off-design performance of an ORC engine with screw expander and two heat exchanger (HEXs) architectures is investigated, while recovering heat from an internal combustion engine (ICE). Firstly, nominal system sizing results indicate that the screw expander isentropic efficiency exceeds 80%, while the plate HEXs (PHEXs) heat transfer area requirements are 50% lower, than the respective ones for double pipe (DPHEX) design. Next, the ORC engine operation is optimised at part-load (PL) ICE conditions. Although, the HEXs heat transfer coefficients decrease with part-load, the total HEX effectiveness increases, due to higher temperature difference across the working fluids. Findings also reveal that the PHEX performance is less sensitive to the off-design operation. Off-design power output maps indicate that the optimised ORC engine PL reduces to 72%, for ICE PL of 60%, while ORC engines with PHEXs generate slightly more power, for the same heat source conditions. Overall, the modelling tool developed can predict ORC performance over an operating envelope and allows the selection of optimal designs and sizes of ORC HEXs and expanders

Off-design comparison of subcritical and partial evaporating ORCs in quasi-steady state annual simulations

The subcritical ORC (SCORC) is considered the industry standard due to its simple configuration, acceptable efficiency and low costs. However, it is known that alternative ORC configurations have the potential to increase efficiency. A cycle modification which closely resembles the SCORC is the partial evaporating ORC (PEORC), where a two-phase mixture of liquid-vapour enters the expander instead of superheated vapour. In theoretical studies at design conditions, higher power outputs are achieved for the PEORC compared to the SCORC. This work aims to go a step further by investigating the performance of the SCORC and PEORC under time-dependent operating conditions. A direct comparison between the SCORC and PEORC is made for identically sized systems using as input the waste heat stream of a waste incinerator plant and the changing ambient conditions. Performance maps of both cycle configurations are compiled and the benefit of an expander operating at variable speed is briefly discussed. The results indicate that for the specific case under investigation, the PEORC has an increased annually averaged net power output of 9.6% compared to the SCORC. Use of annually averaged input conditions results in an overestimation of the net power output for both the SCORC and PEORC, and furthermore, the relative improvement in power output for the PEORC is reduced to 6.8%. As such, the use of time-averaged conditions when comparing cycle architectures should preferably be avoided

A Multiancestral Genome-Wide Exome Array Study of Alzheimer Disease, Frontotemporal Dementia, and Progressive Supranuclear Palsy

Importance Previous studies have indicated a heritable component of the etiology of neurodegenerative diseases such as Alzheimer disease (AD), frontotemporal dementia (FTD), and progressive supranuclear palsy (PSP). However, few have examined the contribution of low-frequency coding variants on a genome-wide level. Objective To identify low-frequency coding variants that affect susceptibility to AD, FTD, and PSP. Design, Setting, and Participants We used the Illumina HumanExome BeadChip array to genotype a large number of variants (most of which are low-frequency coding variants) in a cohort of patients with neurodegenerative disease (224 with AD, 168 with FTD, and 48 with PSP) and in 224 control individuals without dementia enrolled between 2005-2012 from multiple centers participating in the Genetic Investigation in Frontotemporal Dementia and Alzheimer’s Disease (GIFT) Study. An additional multiancestral replication cohort of 240 patients with AD and 240 controls without dementia was used to validate suggestive findings. Variant-level association testing and gene-based testing were performed. Main Outcomes and Measures Statistical association of genetic variants with clinical diagnosis of AD, FTD, and PSP. Results Genetic variants typed by the exome array explained 44%, 53%, and 57% of the total phenotypic variance of AD, FTD, and PSP, respectively. An association with the known AD gene ABCA7 was replicated in several ancestries (discovery P = .0049, European P = .041, African American P = .043, and Asian P = .027), suggesting that exonic variants within this gene modify AD susceptibility. In addition, 2 suggestive candidate genes, DYSF (P = 5.53 × 10−5) and PAXIP1 (P = 2.26 × 10−4), were highlighted in patients with AD and differentially expressed in AD brain. Corroborating evidence from other exome array studies and gene expression data points toward potential involvement of these genes in the pathogenesis of AD. Conclusions and Relevance Low-frequency coding variants with intermediate effect size may account for a significant fraction of the genetic susceptibility to AD and FTD. Furthermore, we found evidence that coding variants in the known susceptibility gene ABCA7, as well as candidate genes DYSF and PAXIP1, confer risk for AD

Genetic prediction of ICU hospitalization and mortality in COVID-19 patients using artificial neural networks

There is an unmet need of models for early prediction of morbidity and mortality of Coronavirus disease-19 (COVID-19). We aimed to a) identify complement-related genetic variants associated with the clinical outcomes of ICU hospitalization and death, b) develop an artificial neural network (ANN) predicting these outcomes and c) validate whether complement-related variants are associated with an impaired complement phenotype. We prospectively recruited consecutive adult patients of Caucasian origin, hospitalized due to COVID-19. Through targeted next-generation sequencing, we identified variants in complement factor H/CFH, CFB, CFH-related, CFD, CD55, C3, C5, CFI, CD46, thrombomodulin/THBD, and A Disintegrin and Metalloproteinase with Thrombospondin motifs (ADAMTS13). Among 381 variants in 133 patients, we identified 5 critical variants associated with severe COVID-19: rs2547438 (C3), rs2250656 (C3), rs1042580 (THBD), rs800292 (CFH) and rs414628 (CFHR1). Using age, gender and presence or absence of each variant, we developed an ANN predicting morbidity and mortality in 89.47% of the examined population. Furthermore, THBD and C3a levels were significantly increased in severe COVID-19 patients and those harbouring relevant variants. Thus, we reveal for the first time an ANN accurately predicting ICU hospitalization and death in COVID-19 patients, based on genetic variants in complement genes, age and gender. Importantly, we confirm that genetic dysregulation is associated with impaired complement phenotype.- Pfizer Pharmaceuticals(undefined

Optimisation of high-efficiency combined heat and power systems for distributed generation

Distributed combined heat and power (CHP) systems have the potential to cover a significant amount of the global energy requirements for power, and heating. Small-to-medium scale CHP systems, in the built environment and in the industry (up to a few MWs), are typically driven by internal combustion engines (ICE). In CHP-ICE systems, more than 55% of the energy input is transferred as heat in the exhaust-gas stream and the jacket water cooling circuit. Unless these thermal outputs are utilised, the energy will be released to the atmosphere as waste heat, deteriorating the system’s efficiency. Organic Rankine cycle (ORC) engines are a promising heat-to-power technology, for converting waste heat into power. Therefore, coupling ORC engines as bottoming cycles to CHP-ICEs can maximise overall system efficiency, and reduce energy costs. In this thesis, the design of ICE-ORC CHP systems is investigated from thermodynamic, operating and economic perspectives, aiming to fully unlock the potential of such advanced high-efficiency cogeneration systems. An integrated ICE-ORC CHP optimisation tool is developed, which, unlike previous studies, captures the performance trade-offs between the two interacting engines, to optimise the combined system performance. A dynamic ICE model is developed and validated, along with a steady-state model of subcritical recuperative ORC engines. Multiple working fluids are investigated, along with naturally aspirated and turbocharged ICEs. By optimising the combined ICE-ORC CHP system simultaneously: i) the total power output increases by up to 30%, in comparison to the conventional approach where the two engines are optimised separately; ii) the electrical efficiency increases by up to 21%, in comparison to the stand-alone ICE; and iii) in the integrated system the ICE operation is adjusted to promote the ORC power output, which generates up to 15% of the total power, improving fuel efficiency. When focusing on maximising power output only, this comes at the cost of higher fuel consumption. In contrast, when optimising the integrated ICE-ORC CHP system for specific fuel consumption (SFC), the fuel consumption decreases by up to 17%. These findings prove that by taking a holistic approach in the design of ICE-ORC CHP systems, considering the combined system interactions, these can generate more power, with lower fuel consumption and costs. ORC engines in ICE-ORC CHP systems will experience variable heat-source conditions (temperature and mass flow are), while the ICE load fluctuates. To maximise the running hours of ORC engines, and improve their economic proposition, the system should maintain high efficiency, not only at the design point, but also at off-design operation. An off-design optimisation tool is therefore developed to generate optimised off-design operation maps. This work differs from previous studies in that the tool considers explicitly the time-varying operational characteristics and interactions of the ORC engine components in the integrated system. Double-pipe (DPHEX) and plate-frame heat exchanger (PHEX) models are used for sizing the ORC evaporator and condenser, and piston and screw expander models for sizing the expander. The ORC system is first sized for full-load ICE operation (design point). Then, ICE part-load (PL) conditions are obtained and new ORC operating points are optimised. Results reveal that the ORC engine power output is underestimated by up to 17%, when the off-design operational characteristics of the components are not considered. The piston expander efficiency increases by up to 16% at PL operation, while the ORC thermal efficiency increases by up to 7% at off-design operation. Optimised ORC engines with screw expanders operate always with two expansion stages. Although the latter generate slightly more power at their design point than when using piston machines, pistons perform better at off-design conditions. ORC engines with PHEXs generate 5-12% more power than DPHEX designs, while having U-values almost double that of DPHEXs. Although, heat transfer coefficients decrease by 25-30% at off-design, the HEX effectiveness increases, by up to 15%. By considering the time-varying characteristics of the ORC components, as the ICE PL reduces, the optimised ORC engine power output decreases at a lower rate: at ICE PL of 60%, the optimised ORC engine with fluids, such as R1233zd, operates at 77% of its nominal capacity (with piston expanders). An ORC thermoeconomic optimisation tool is then developed. Unlike other studies where the component types are predefined, the tool scans alternative components’ typologies, sizes, and configurations, to obtain the best-performing design. New cost correlations are presented to assist with predicting ORC costs. ORC engines optimised for maximum power output have the highest SICs, falling in the range of 1,000-7,500 GBP/kW for piston expanders, and 1,500-5,500 GBP/kW for screw expanders, due to high HEX areas, and high volumetric flow rates. In contrast, when minimising SIC, power output reduces by 15-50%, but the cost also reduces by up to 35%. In the optimised designs, the evaporator is selected to be a PHEX, the condenser is a DPHEX, whilst ORC engines with screw machines operate with two-stage expansion. Multi-objective optimisation reveals optimal ORC systems with a range of power outputs between 70-100 kW, for which increasing power by 33%, results in an increase of SIC of less than 10%. This indicates a promising range of capacities for next-generation ORC engines. ORC engines optimised for high power output result in high net present value (NPV), but also high discounted payback period (DPP). In contrast, engines optimised for low SIC achieve DPPs of 2.8-6 years, making them an attractive investment. Overall, these findings can be used by ICE and ORC engine manufacturers, and integrators, to inform component design decisions, and by ORC plant operators to maximise their system performance, under variable operating conditions.Open Acces

Shaping our food – an overview of crop and livestock breeding

You may not have thought about why tomatoes look the way they do, why our pets and farm animals are so calm and friendly, or how it is possible to get a watermelon without any seeds in it. Although the breeding of plants and livestock have shaped more or less everything we eat, few people know about the scientific achievements and the tedious work that results in the food we see on our plates every day. With this book we wish to give an overview of the background of domestication and breeding, from the beginning of farming more than 10,000 years ago to the molecular work of today. We present the basics of the structures and functions of genes, describe why and how different breeding methods are applied to crops and livestock, and give some insight into legislation surrounding the use of biotechnology in breeding in the EU and in Sweden. We also provide an overview of different products produced through genetic modification, a summary of the economic impact of such crops, and some ethical issues related to breeding in general and to genetic modification in particular

Optimisation of a high-efficiency solar-driven organic rankine cycle for applications in the built environment

Energy security, pollution and sustainability are major challenges presently facing the international community, in response to which increasing quantities of renewable energy are to be generated in the urban environment. Consequently, recent years have seen a strong increase in the uptake of solar technologies in the building sector. In this work, the potential of a solar combined heat and power (CHP) system based on an organic Rankine cycle (ORC) engine is investigated in a domestic setting. Unlike previous studies that focus on the optimisation of the ORC subsystem, this study performs a complete system optimisation considering both the design parameters of the solar collector array and the ORC engine simultaneously. Firstly, we present thermodynamic models of different collectors, including flat-plate and evacuated-tube designs, coupled to a non-recuperative sub-critical ORC architecture that delivers power and hot water by using thermal energy rejected from the engine. Optimisation of the complete system is first conducted, aimed at identifying operating conditions for which the power output is maximised. Then, hourly dynamic simulations of the optimised system configurations are performed to complete the system sizing. Results are presented of: (i) dynamic 3-D simulations of the solar collectors together with a thermal energy storage tank, and (ii) of an optimisation analysis to identify the most suitable working fluids for the ORC engine, in which the configuration and operational constraints of the collector array are considered. The best performing working fluids (R245fa and R1233zd) are then chosen for a whole-system annual simulation in a southern European climate. The system configuration combining an evacuated-tube collector array and an ORC engine is found to be best-suited for electricity prioritisation, delivering an electrical output of 3,605¿kWh/year from a 60¿m2 collector array. In addition, the system supplies 13,175¿kWh/year in the form of domestic hot water, which is equivalent to more than 6 times the average annual household demand. A brief cost analysis and comparison with photovoltaic (PV) systems is also performed, where despite the lower PV investment cost per kWel, the levelised energy costs of the different systems are found to be similar if the economic value of the thermal output is taken into account. Finally, a discussion of the modelled solar-CHP systems results shows how these could be used for real applications and extended to other locationsPeer Reviewe

Off-design optimisation of organic Rankine cycle (ORC) engines with different heat exchangers and volumetric expanders in waste heat recovery applications

Organic Rankine cycle (ORC) engines in real applications experience variable heat-source conditions. In this paper, the off-design performance of small- to medium-scale ORC engines recovering heat from stationary internal combustion engines (ICEs) is investigated. Of particular interest are the employment of screw vs. piston expanders, and two heat exchanger (HEX) architectures. Unlike previous studies where the performance of the expander and HEX are assumed fixed during off-design operation, here we consider explicitly their varying and interacting characteristics within the overall system. Nominal sizing results reveal indicated isentropic efficiencies > 80% for twin-screw and > 85% for piston expanders. Following nominal design, the ORC engine operation is optimised for ICE part-load (PL) operation. Although the heat transfer coefficients in the evaporator decrease by up to 30% at PL, the effectiveness in this HEX increases by 20% due to the larger temperature differences across the component. The screw expander efficiency reduces by up to 3% at off-design operation, whilst that of the piston expander increases by up to 16%. Optimised off-design maps indicate that the ORC engine power output reduces to 77% (piston) or 68% (screw) of its full-load value when the ICE operates at 60% PL, and that ORC engines with plate HEXs generate 5-11% more power than those with double-pipe HEX designs. Under variable ICE operation, smaller ORC engines with piston expanders generate more power than larger engines with screw expanders, highlighting the resilient off-design operation of piston machines. The modelling tool developed here can predict ORC performance over a wide operating envelope and provides performance maps that can be used by operators to optimise ORC engine operation in variable conditions and by ORC vendors to inform component design decisions