Imperial College London

ProfessorChristosMarkides

Faculty of EngineeringDepartment of Chemical Engineering

Professor of Clean Energy Technologies
 
 
 
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Contact

 

+44 (0)20 7594 1601c.markides Website

 
 
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Location

 

404ACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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275 results found

Ramos Cabal A, Guarracino I, Mellor A, Alonso Álvarez D, Childs P, Ekins Daukes N, Markides CNet al., 2017, Solar-Thermal and Hybrid Photovoltaic-Thermal Systems for Renewable Heating, Publisher: Grantham Institute, Imperial College London

Headlines Heat constitutes about half of total global energy demand. Solar heat offers key advantages over other renewable sources for meeting this demand through distributed, integrated systems. Solar heat is a mature sustainable energy technology capable of mass deployment. There is significant scope for increasing the installed solar heat capacity in Europe. Only a few European countries are close to reaching the EU target of 1 m2 of solar-thermal installations per person. One key challenge for the further development of the solar-thermal market arises from issues related to the intermittency of the solar resource, and the requirement for storage and/or backup systems. The former increases investment costs and limits adaptability. An analysis of EU countries with good market development, suggests that obligation schemes are the best policy option for maximising installations. These do not present a direct cost to the public budget, and determine the growth of the local industry in the long term. Solar-thermal collectors can be combined with photovoltaic (PV) modules to produce hybrid PV-thermal (PV-T) collectors. These can deliver both heat and electricity simultaneously from the same installed area and at a higher overall efficiency compared to individual solar-thermal and PV panels installed separately. Hybrid PV-T technology provides a particularly promising solution when roof space is limited or when heat and electricity are required at the same time.

Report

Markides C, Tunnicliffe H, 2017, A concentrated effort, TCE The Chemical Engineer, Pages: 38-41, ISSN: 0302-0797

Concentrated solar power (CSP) has received less attention and funding compared to its more popular solar power rival, especially since photovoltaic (PV) technology is more viable in widespread smaller-scale applications. CSP has the ability to store thermal energy unlike conventional photovoltaics. CSP power stations that has storage facilities can utilize heat to generate power even when the sun is out. According to Christos Markides, reader in clean energy processes at the Department of Chemical Engineering at Imperial College London, UK, a silicon PV panel has an efficiency, in terms of solar energy transformed into electricity, or about 15%-20%, while CSP technologies will have efficiencies close to 25%. Markides and his team are researching on a slightly different CSP concept, in which H2O that drives the turbine generation cycle is also utilized as the heat transfer fluid that is sent to the parabolic collectors, rather than using an intermediate thermal oil, a process called direct steam generation. Markides is leading a five-year collaborative CSP research project with African universities - the University of Pretoria in South Africa, the University of Lagos in Nigeria, and the University of Mauritius. The project is a program grant funded by the UK Department for International Development.

Journal article

White MT, Oyewunmi OO, Haslam AJ, Markides CNet al., 2017, Industrial waste-heat recovery through integrated computer-aided working-fluid and ORC system optimisation using SAFT-γ Mie, Energy Conversion and Management, Vol: 150, Pages: 851-869, ISSN: 0196-8904

A mixed-integer non-linear programming optimisation framework is formulated and developed that combines a molecular-based, group-contribution equation of state, SAFT-γγ Mie, with a thermodynamic description of an organic Rankine cycle (ORC) power system. In this framework, a set of working fluids is described by its constituent functional groups (e.g., since we are focussing here on hydrocarbons: single bondCH3, single bondCH2single bond, etc. ), and integer optimisation variables are introduced in the description the working-fluid structure. Molecular feasibility constraints are then defined to ensure all feasible working-fluid candidates can be found. This optimisation framework facilitates combining the computer-aided molecular design of the working fluid with the power-system optimisation into a single framework, thus removing subjective and pre-emptive screening criteria, and simultaneously moving towards the next generation of tailored working fluids and optimised systems for waste-heat recovery applications. SAFT-γγ Mie has not been previously employed in such a framework. The optimisation framework, which is based here on hydrocarbon functional groups, is first validated against an alternative formulation that uses (pseudo-experimental) thermodynamic property predictions from REFPROP, and against an optimisation study taken from the literature. The framework is then applied to three industrial waste-heat recovery applications. It is found that simple molecules, such as propane and propene, are the optimal ORC working fluids for a low-grade (150 °C) heat source, whilst molecules with increasing molecular complexity are favoured at higher temperatures. Specifically, 2-alkenes emerge as the optimal working fluids for medium- and higher-grade heat-sources in the 250–350 °C temperature range. Ultimately, the results demonstrate the potential of this framework to drive the search for the next generation of ORC systems, and to

Journal article

Oyewunmi OA, white MT, Chatzopoulou M, Haslam A, Markideset al., Integrated Computer-Aided Working-Fluid Design and Power System Optimisation: Beyond Thermodynamic Modelling, 30th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2017), Publisher: ECOS-2017

Improvements in the thermal and economic performance of organic Rankine cycle (ORC) systems are requiredbefore the technology can be successfully implemented across a range of applications. The integration ofcomputer-aided molecular design (CAMD) with a process model of the ORC facilitates the combinedoptimisation of the working-fluid and the power system in a single modelling framework, which should enablesignificant improvements in the thermodynamic performance of the system. However, to investigate theeconomic performance of ORC systems it is necessary to develop component sizing models. Currently, thegroup-contribution equations of state used within CAMD, which determine the thermodynamic properties of aworking-fluid based on the functional groups from which it is composed, only derive the thermodynamicproperties of the working-fluid. Therefore, these do not allow critical components such as the evaporator andcondenser to be sized. This paper extends existing CAMD-ORC thermodynamic models by implementinggroup-contribution methods for the transport properties of hydrocarbon working-fluids into the CAMD-ORCmethodology. Not only does this facilitate the sizing of the heat exchangers, but also allows estimates of systemcosts by using suitable cost correlations. After introducing the CAMD-ORC model, based on the SAFT-γ Mieequation of state, the group-contribution methods for determining transport properties are presented alongsidesuitable heat exchanger sizing models. Finally, the full CAMD-ORC model incorporating the componentmodels is applied to a relevant case study. Initially a thermodynamic optimisation is completed to optimise theworking-fluid and thermodynamic cycle, and then the component models provide meaningful insights into theeffect of the working-fluid on the system components.

Conference paper

Oyewunmi OA, Lecompte S, De Paepe M, Markideset al., Thermodynamic Optimization of Recuperative Sub- and Transcritical Organic Rankine Cycle Systems, 30th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2017), Publisher: ECOS-2017

There is significant interest in the deployment of organic Rankine cycle (ORC) technology for waste-heatrecovery and power generation in industrial settings. This study considers ORC systems optimized formaximum power generation using a case study of an exhaust flue-gas stream at a temperature of 380 °C asthe heat source, covering over 30 working fluids and also considering the option of featuring a recuperator.Systems based on transcritical cycles are found to deliver higher power outputs than subcritical ones, withoptimal evaporation pressures that are 4-5 times the critical pressures of refrigerants and light hydrocarbons,and 1-2 times those of siloxanes and heavy hydrocarbons. For maximum power production, a recuperator isnecessary for ORC systems with constraints imposed on their evaporation and condensation pressures. Thisincludes, for example, limiting the minimum condensation pressure to atmospheric pressure to prevent subatmosphericoperation of this component, as is the case when employing heavy hydrocarbon and siloxaneworking fluids. For scenarios where such operating constraints are relaxed, the optimal cycles do not featurea recuperator, providing some capital cost savings, with some cycles showing more than three times thegenerated power than with this component, making investments in sub-atmospheric components worthwhile.

Conference paper

Ramos Cabal A, Chatzopoulou MA, Guarracino I, Freeman J, Markides CNet al., 2017, Hybrid photovoltaic-thermal solar systems for combined heating, coolingand power provision in the urban environment, Energy Conversion and Management, Vol: 150, Pages: 838-850, ISSN: 0196-8904

Solar energy can play a leading role in reducing the current reliance on fossil fuels and in increasing renewable energy integration in the built environment. Hybrid photovoltaic-thermal (PV-T) systems can reach overall efficiencies in excess of 70%, with electrical fficiencies in the range of 15-20% and thermal efficiencies of 50% or higher. In most applications, the electrical output of a hybrid PV-T system is the priority, hence the contacting fluid is used to cool the PV cells to maximise their electrical performance, which imposes a limit on the fluid's downstream use. When optimising the overall output of PV-T systems for combinedheating and cooling provision, this technology can cover more than 60% of the heating and about 50% of the cooling demands of households in the urban environment. To achieve this, PV-T systems can be coupledto heat pumps or absorption refrigeration systems as viable alternatives to vapour-compression systems. This work considers the techno-economic challenges of such systems, when aiming at a low cost per kWh of energy generation of PV-T systems for co- or tri-generation in the housing sector. First, the viability and afordability of the proposed systems are studied in ten European locations, with local weather pro files, using annually and monthly averaged solar-irradiance and energy-demand data. Based on annual simulations, Seville, Rome, Madrid and Bucharest emerge as the most promising locations from those examined, and the most efficient system confi guration involves coupling PV-T panels to water-to-water heat pumps that usethe PV-T thermal output to maximise the system's COP. Hourly resolved transient models are then defi ned in TRNSYS in order to provide detailed estimates of system performance, since it is found that the temporal resolution (e.g. hourly, daily, yearly) of the simulations strongly affects their predicted performance. The TRNSYS results indicate that PV-T systems have the potential to cover 60% of the heating

Journal article

Guarracino I, Freeman J, Markides CN, 2017, Solar heat and power with thermal energy storage in the UK, SolaStor

Solar energy has the potential to cover a high fraction of thedemand for heat and electricity in residential buildings. Fig. 1 showsthe variation in incident solar irradiation received across Europe.In London the annual solar irradiation is ~1100 kWh/m2 per year,while the typical domestic energy consumption per household is~12000 kWh/year for heating and ~4000 kWh/year for electricity.Thus the solar energy received on a rooftop of ~15 m2is enoughpotentially enough to provide the entire annual demand fordomestic energy.Our research focuses on various aspects of two solar technologiesfor the combined provision of heating and power (CHP): solarorganic Rankine cycle systems with low-to-medium temperaturesolar-thermal collectors (Figs. 2-3) and hybrid photovoltaic/thermal(PVT) systems. (Fig.4).

Poster

White M, Sayma AI, Markides CN, 2017, Supersonic flow of non-ideal fluids in nozzles: An application of similitude theory and lessons for ORC turbine design and flexible use considering system performance, 1st International Seminar on Non-Ideal Compressible-Fluid Dynamics for Propulsion and Power (NICFD), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588

Conference paper

Taleb AI, Sapin PMC, Barfuß C, Fabris D, Markides CNet al., 2017, CFD Analysis of Thermally Induced Thermodynamic Loses in the Reciprocating Compression and Expansion of Real Gases, 1st International Seminar on Non-Ideal Compressible-Fluid Dynamics for Propulsion and Power, Publisher: IOP Publishing: Conference Series, ISSN: 1742-6588

The efficiency of expanders is of prime importance in determining the overallperformance of a variety of thermodynamic power systems, with reciprocating-piston expandersfavoured at intermediate-scales of application (typically 10–100 kW). Once the mechanical lossesin reciprocating machines are minimized (e.g. through careful valve design and operation), lossesdue to the unsteady thermal-energy exchange between the working fluid and the solid walls ofthe containing device can become the dominant loss mechanism. In this work, gas-spring devicesare investigated numerically in order to focus explicitly on the thermodynamic losses that arisedue to this unsteady heat transfer. The specific aim of the study is to investigate the behaviourof real gases in gas springs and to compare this to that of ideal gases in order to attain a betterunderstanding of the impact of real-gas effects on the thermally induced losses in reciprocatingexpanders and compressors. A CFD-model of a gas spring is developed in OpenFOAM. Threedifferent fluid models are compared: (1) an ideal-gas model with constant thermodynamicand transport properties; (2) an ideal-gas model with temperature-dependent properties; and(3) a real-gas model using the Peng-Robinson equation-of-state with temperature and pressure-dependent properties. Results indicate that, for simple, mono- and diatomic gases, like helium ornitrogen, there is a negligible difference in the pressure and temperature oscillations over a cyclebetween the ideal and real-gas models. However, when considering heavier (organic) molecules,such as propane, the ideal-gas model tends to overestimate the pressure compared to the real-gasmodel, especially if the temperature and pressure dependency of the thermodynamic propertiesis not taken into account. In fact, the ideal-gas model predicts higher pressures by as much as25% (compared to the real-gas model). Additionally, both ideal-gas models underestimate thethermall

Conference paper

White M, Oyewunmi OA, Haslam A, Markideset al., Incorporating Computer-Aided Working-Fluid Design in the System Optimisation of an Organic Rankine Cycle Using the SAFT-γ Mie Equation of State, SAFT 2017 Conference

Conference paper

Gupta A, Markides CN, An experimental study of the autoignition of polydispersed liquid-fuel droplets in a confined high-temperature turbulent coflow, 8th European Combustion Meeting

Conference paper

White MT, Oyewunmi OA, Haslam AJ, Markides CNet al., High-efficiency industrial waste-heat recovery through computer-aided integrated working-fluid and ORC system optimisation, The 4th Sustainable Thermal Energy Management International Conference (SusTEM 2017)

In this paper, we develop a mixed-integer non-linear programming optimisation framework that combines working-fluid thermodynamic property predictions from a group-contribution equation of state, SAFT- Mie, with a thermodynamic description of an organic Rankine cycle. In this model, a number of working-fluids are described by their constituent functional groups (i.e., -CH3, -CH2, etc.), and integer optimisation variables are introduced in the description of the structure of the working-fluid. This facilitates combining the computer-aided molecular design of novel working-fluids with the power system optimisation into a single framework, thus removing subjective and pre-emptive screening criteria, and simultaneously moving towards the next generation of tailored working-fluids and optimised organic Rankine cycle systems for industrial waste-heat recovery applications. The thermodynamic model is first validated against an alternative formulation that uses (pseudo-experimental) thermodynamic property predictions from REFPROP, and against an optimisation study taken from the literature. Furthermore, molecular feasibility constraints are defined and validated in order to ensure all feasible working-fluid candidates can be found. Finally, the optimisation problem is formulated using the functional groups from the hydrocarbon family, and applied to three industrial waste-heat recovery case studies. The results demonstrate the potential of this framework to drive the search for the next generation of organic Rankine cycles, and to provide meaningful insights into which working-fluids are the optimal choices for a targeted application.

Conference paper

Willich C, Markides CN, White AJ, 2017, An investigation of heat transfer losses in reciprocating devices, APPLIED THERMAL ENGINEERING, Vol: 111, Pages: 903-913, ISSN: 1359-4311

Journal article

Ramos Cabal A, Chatzopoulou MA, Guarracino I, Freeman J, Markides CNet al., Hybrid photovoltaic-thermal solar systems for combined heating, cooling and power provision in the urban environment, 4th Sustainable Thermal Energy Management International Conference (SusTEM 2017)

Conference paper

Charogiannis, Denner, van Wachem, kalliadasis, Markideset al., 2017, Detailed Hydrodynamic Characterization of Harmonically Excited Falling-Film Flows: A Combined Experimental and Computational Study, Physical Review Fluids, Vol: 2, Pages: 014002-014002, ISSN: 2469-990X

We present results from the simultaneous application of planar laser-induced uorescence (PLIF)and particle image/tracking velocimetry, complemented by direct numerical simulations, aimed atthe detailed hydrodynamic characterization of harmonically excited liquid- lm ows falling underthe action of gravity. The experimental campaign comprises four di erent aqueous-glycerol solutionscorresponding to four Kapitza numbers (Ka= 14, 85, 350, 1800), spanning the Reynolds numberrangeRe= 2:3

Journal article

Herrando M, Guarracino I, del Amo A, Zabalza I, Markides CNet al., 2017, Energy Characterization and Optimization of New Heat Recovery Configurations in Hybrid PVT Systems, 11th ISES EuroSun Conference, Publisher: INTL SOLAR ENERGY SOC, Pages: 1228-1239

Conference paper

Charogiannis A, Markides CN, 2017, APPLICATION OF LASER-INDUCED FLUORESCENCE, PARTICLE VELOCIMETRY AND INFRARED THERMOGRAPHY TO HEATED FALLING-FILM FLOWS, ASME Summer Heat Transfer Conference, Publisher: AMER SOC MECHANICAL ENGINEERS

Conference paper

Kheirabadi AN, Freeman J, Cabal AR, Markides CNet al., 2017, EXPERIMENTAL INVESTIGATION OF AN AMMONIA-WATER DIFFUSION-ABSORPTION REFRIGERATOR (DAR) AT PART LOAD, ASME Summer Heat Transfer Conference, Publisher: AMER SOC MECHANICAL ENGINEERS

Conference paper

Herrando M, Ramos A, Zabalza I, Markides CNet al., 2017, Energy performance of a solar trigeneration system based on a novel hybrid PVT panel for residential applications, Pages: 1090-1101

© 2017. The Authors. The overall aim of this work is to assess the performance of high-efficiency solar trigeneration systems based on a novel hybrid photovoltaic-thermal (PVT) collector for the provision of domestic hot water (DHW), space heating (SH), cooling and electricity to residential single-family households. To this end, a TRNSYS model is developed featuring a novel hybrid PVT panel based on a new absorber-exchanger configuration coupled via a thermal store to two alternative small-scale solar heating and cooling configurations, one based on an electrically-driven vapour-compression heat pump (PVT+HP) and one on a thermally-driven absorption refrigeration unit (PVT+AR). The energy demands of a single-family house located in three different climates, namely Seville (Spain), Rome (Italy) and Paris (France), are estimated using EnergyPlus. Hourly transient simulations of the complete systems considering real weather data and reasonable areas for collector installation (< 30 m2) are conducted over a year. The household energy demands covered by the two systems indicate that the PVT+HP configuration is the most promising for the locations of Rome and Paris, covering more than 74% the DHW demand, 100% of the space heating and cooling demands, as well as an important share of the electricity demand. Meanwhile, for Seville, the PVT+AR configuration appears as a promising alternative, covering more than 80% of the DHW, around 70% of the cooling and electricity, and 54% of the space heating demands.

Conference paper

Le Brun N, Charogiannis A, Hewitt GF, Markides CNet al., 2017, TACKLING COOLANT FREEZING IN GENERATION-IV MOLTEN SALT REACTORS, 25th International Conference on Nuclear Engineering, Publisher: AMER SOC MECHANICAL ENGINEERS

Conference paper

Chatzopoulou MA, Markides CN, Modelling of advanced combined heat and power systems in building applications, 2nd Thermal and Fluid Engineering Conference TFEC2017

Conference paper

Mellor AV, Guarracino I, Llin LF, Alonso alvarez, Riverola A, Thoms S, Paul DJ, Markides C, Chemisana D, Maier S, Ekins-daukes Net al., 2016, Specially designed solar cells for hybrid photovoltaic-thermal generators, 43rd IEEE Photovoltaic Specialists Conference, Publisher: IEEE

The performance of hybrid photovoltaic-thermal systems can be improved using PV cells that are specially designed to generate both electricity and useful heat with maximum efficiency. Present systems, however, use standard PV cells that are only optimized for electrical performance. In this work, we have developed two cell-level components that will improve the thermal efficiency of PV-T collectors, with minimal loss of electrical efficiency. These are a spectrally-selective low-emissivity coating to reduce radiative thermal losses, and a nanotextured rear reflector to improve absorption of the near-infrared part of the solar spectrum for heat generation.

Conference paper

Le Brun N, Hewitt GF, Markides CN, 2016, Transient freezing of molten salts in pipe-flow systems: application to the direct reactor auxiliary cooling system (DRACS), Applied Energy, Vol: 186, Pages: 56-67, ISSN: 0306-2619

The possibility of molten-salt freezing in pipe-flow systems is a key concern for the solar-energy industry and a safety issue in the new generation of molten-salt reactors, worthy of careful consideration. This paper tackles the problem of coolant solidification in complex pipe networks by developing a transient thermohydraulic model and applying it to the ‘Direct Reactor Auxiliary Cooling System’ (DRACS), the passive-safety system proposed for the Generation-IV molten-salt reactors. The results indicate that DRACS, as currently envisioned, is prone to failure due to freezing in the air/molten-salt heat exchanger, which can occur after approximately 20 minutes, leading to reactor temperatures above 900 °C within 4 hours. The occurrence of this scenario is related to an unstable behaviour mode of DRACS in which newly formed solid-salt deposit on the pipe walls acts to decrease the flow-rate in the secondary loop, facilitating additional solid-salt deposition. Conservative criteria are suggested to facilitate preliminary assessments of early-stage DRACS designs. The present study is, to the knowledge of the authors, the first of its kind in serving to illustrate possible safety concerns in molten-salt reactors, which are otherwise considered very safe in the literature. Furthermore, and from a broader prospective, the analytical tools developed in this study can also be applied to examine the freezing propensity of molten-salt flows in other complex piping systems where standard, finite element approaches are computationally too expensive.

Journal article

Zhang K, Chen X, Markides CN, Yang Y, Shen Set al., 2016, Evaluation of ejector performance for an organic Rankine cycle combined power and cooling system, Applied Energy, Vol: 184, Pages: 404-412, ISSN: 0306-2619

Power-generation systems based on organic Rankine cycles (ORCs) are well suited and increasingly employed in the conversion of thermal energy from low temperature heat sources to power. These systems can be driven by waste heat, for example from various industrial processes, as well as solar or geothermal energy. A useful extension of such systems involves a combined ORC and ejector-refrigeration cycle (EORC) that is capable, at low cost and complexity, of producing useful power while having a simultaneous capacity for cooling that is highly desirable in many applications. A significant thermodynamic loss in such a combined energy system takes place in the ejector due to unavoidable losses caused by irreversible mixing in this component. This paper focuses on the flow and transport processes in an ejector, in order to understand and quantify the underlying reasons for these losses, as well as their sensitivity to important design parameters and operational variables. Specifically, the study considers, beyond variations to the geometric design of the ejector, also the role of changing the external conditions across this component and how these affect its performance; this is not only important in helping develop ejector designs in the first instance, but also in evaluating how the performance may shift (in fact, deteriorate) quantitatively when the device (and wider energy system within which it functions) are operated at part load, away from their design/operating points. An appreciation of the loss mechanisms and how these vary can be harnessed to propose new and improved designs leading to more efficient EROC systems, which would greatly enhance this technology’s economic and environmental potential. It is found that some operating conditions, such as a high pressure of the secondary and discharge fluid, lead to higher energy losses inside the ejector and limit the performance of the entire system. Based on the ejector model, an optimal design featuring a sm

Journal article

Morgan RG, Ibarra R, Zadrazil I, Matar OK, Hewitt GF, Markides CN, Morgan R, Ibarra R, Zadrazil I, Matar O, Hewitt G, Markides Cet al., 2016, On the role of buoyancy-driven instabilities in horizontal liquid–liquid flow, International Journal of Multiphase Flow, Vol: 89, Pages: 123-135, ISSN: 0301-9322

Horizontal flows of two initially stratified immiscible liquids with matched refractive indices, namely an aliphatic hydrocarbon oil (Exxsol D80) and an aqueous-glycerol solution, are investigated by combining two laser-based optical-diagnostic measurement techniques. Specifically, high-speed Planar Laser-Induced Fluorescence (PLIF) is used to provide spatiotemporally resolved phase information, while high-speed Particle Image and Tracking Velocimetry (PIV/PVT) are used to provide information on the velocity field in both phases. The two techniques are applied simultaneously in a vertical plane through the centreline of the investigated pipe flow, illuminated by a single laser-sheet in a time-resolved manner (at a frequency of 1–2 kHz depending on the flow condition). Optical distortions due to the curvature of the (transparent) circular tube test-section are corrected with the use of a graticule (target). The test section where the optical-diagnostic methods are applied is located 244 pipe-diameters downstream of the inlet section, in order to ensure a significant development length. The experimental campaign is explicitly designed to study the long-length development of immiscible liquid–liquid flows by introducing the heavier (aqueous) phase at the top of the channel and above the lighter (oil) phase that is introduced at the bottom, which corresponds to an unstably-stratified “inverted” inlet orientation in the opposite orientation to that in which the phases would naturally separate. The main focus is to evaluate the role of the subsequent interfacial instabilities on the resulting long-length flow patterns and characteristics, also by direct comparison to an existing liquid–liquid flow dataset generated in previous work, downstream of a “normal” inlet orientation in which the oil phase was introduced over the aqueous phase in a conventional stably-stratified inlet orientation. To the best knowledge of the authors this

Journal article

White AJ, McTigue JD, Markides CN, 2016, Analysis and optimisation of packed-bed thermal reservoirs for electricity storage applications, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART A-JOURNAL OF POWER AND ENERGY, Vol: 230, Pages: 739-754, ISSN: 0957-6509

Journal article

Oyewunmi OA, Kirmse CJW, Markides CN, HEAT EXCHANGER ANALYSIS OF AZEOTROPE MIXTURES IN ORGANIC RANKINE CYCLES, UK Heat Transfer Conference

Conference paper

Delangle ACC, 2016, MODELLING AND OPTIMISATION OF A DISTRICT HEATING NETWORK’S MARGINAL EXTENSION

District heating networks have a key role to play in tackling greenhouse gas emissions associated with urban energy systems. In this context, renewed attention has recently been paid to them and there is a global trend towards the acceleration of district heating expansion. If several existing networks even plan to extend, little work has been carried out on district heating networks expansion in the literature. The following thesis develops a methodology to find the best district heating network expansion strategy under given constraints. After analysing the heat demand and establishing buildings connection scenarios, the model developed optimises the energy centre expansion over a twelve years’ time horizon. Spatial expansion aspects are also included. The optimisation approach was applied to the case of the Barkantine district heating network in the Isle of Dogs, London. The model demonstrated that depending on the optimisation performed (costs or greenhouse gas emissions), some connection strategies have to be privileged. It also proved that district heating scheme’s financial viability may be affected by the connection scenario chosen, highlighting the necessity of planning strategies for district heating networks. The proposed approach can be adapted to other district heating network schemes and modified to integrate more aspects and constraints.

Thesis dissertation

Georgiou S, Markides CN, Shah N, 2016, Decarbonisation of food supply chains from an energetic perspective through optimisation and technological modelling: A holistic approach, Perspectives on Environmental Change DTP Conference 2016

Poster

Freeman J, Ramos Cabal A, Mac Dowel N, Markides CNet al., An experimentally validated model of a solar-cooling system based on an ammonia-water diffusion-absorption cycle, The 8th International Conference on Applied Energy – ICAE2016

An experimentally validated thermodynamic model of a domestic-scale solar-cooling system based on an ammonia-water diffusion-absorption refrigeration (DAR) cycle is presented. The model combines sub-component descriptions of a DAR unit and a suitably sized (matched) solar-collector array, which are validated separately;outdoor tests are performed on an evacuated-tube (ET) collector over a range of solar-irradiance conditions, while a 150-W (nominal rating) DAR unit is tested in the laboratory with a thermal input provided by controlled electrical heaters. A COP of 0.2 is reported for the DARunit when operating with a generator temperature of 155 °C and a system charge pressure of 20.7 bar. Using the experimentally validated solar-cooling system model, it is found that the area of the collector array required to power the system depends strongly on the type of collector. Annual simulations are also performed in various geographical regions order to predict the system’s cooling output. It is found that a single DAR unit with a 3-m2 ET arrayhas the potential to provide 150-200 kWh per year of coolingin a southern European climate, which amounts approximately to the per capita demand for space cooling in residential dwellings in the same region.

Conference paper

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