Imperial College London

DrJianSong

Faculty of EngineeringDepartment of Chemical Engineering

Research Associate
 
 
 
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jian.song

 
 
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B432ABCACE ExtensionSouth Kensington Campus

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Summary

 

Publications

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41 results found

Wang Y, Song J, Chatzopoulou MA, Sunny N, Simpson MC, Wang J, Markides CNet al., 2021, A holistic thermoeconomic assessment of small-scale, distributed solar organic Rankine cycle (ΟRC) systems: Comprehensive comparison of configurations, component and working fluid selection, Energy Conversion and Management, Vol: 248, Pages: 1-19, ISSN: 0196-8904

In this paper, results from comprehensive thermoeconomic assessments of small-scale solar organic Rankine cycle (ORC) systems are presented based on weather data in London, UK, which is taken as representative of a temperate climate with modest temperature changes, mild winters and moderate summers. The assessments consider a range of: (i) solar collector types (flat-plate, evacuated-tube, and evacuated flat-plate collectors); (ii) power cycle configurations (basic/recuperative, partial/full evaporating, and subcritical/transcritical cycles); (iii) expander types (scroll, screw, and piston) and designs; and (iv) a set of suitable working fluids. All possible solar-ORC system designs are optimised by considering simultaneously key parameters in the solar field and in the power cycle in order to obtain the highest electricity generation, from which the best-performing systems are identified. Selected designs are then subjected to detailed, annual simulations considering the systems’ operation, explicitly considering off-design performance under actual varying weather conditions. The results indicate that, among all investigated designs, solar-ORC systems based on the subcritical recuperative ORC (SRORC), evacuated flat-plate collectors (EFPCs), a piston expander, and isobutane as the working fluid outperforms all the other system designs on thermodynamic performance, whilst having the highest annual electricity generation of 1,100 kW·h/year (73 kW·h/year/m2) and an overall thermal efficiency of 5.5%. This system also leads to the best economic performance with a levelised cost of energy (LCOE) of ~1 $/kW·h. Apart from the specific weather data used for these detailed system simulations, this study also proceeds to consider a wider range of climates associated with other global regions by varying the solar resource available to the system. Interestingly, it is found that the optimal solar-ORC system design remains unchanged for different cond

Journal article

Song J, Wang Y, Wang K, Wang J, Markides CNet al., 2021, Combined supercritical CO2 (SCO2) cycle and organic Rankine cycle (ORC) system for hybrid solar and geothermal power generation: Thermoeconomic assessment of various configurations, Renewable Energy, Vol: 174, Pages: 1020-1035, ISSN: 0960-1481

Hybrid solar and geothermal utilisation is a promising option for effective exploitation of renewable energy sources. Concentrated solar power (CSP) systems with geothermal preheating are acknowledged as an attractive solution, with supercritical CO2 (SCO2) cycle systems adopted for power generation thanks to the favourable properties offered by CO2 as a working fluid. In order to further improve the overall performance of such systems, organic Rankine cycle (ORC) systems can be added as bottoming cycles to recover the heat rejected from the topping SCO2 cycle system and also to utilise surplus geothermal heat available after the brine is used for preheating in the SCO2 system. This paper proposes four configurations of combined SCO2-ORC system for hybrid solar and geothermal power generation and performs detailed thermodynamic and economic assessments based on actual conditions in Seville, Spain. The results reveal that combined systems in which the geothermal-brine stream is split into two parallel flows and utilised separately by the topping SCO2 cycle and bottoming ORC systems are preferable. A split geothermal-stream combined system with the ORC working fluid first utilising geothermal heat followed in series by heat from the topping SCO2 cycle system delivers a net power output of 2940 kW, which is the maximum among all the proposed configurations and is 45% higher than that of a standalone SCO2 plant. A similar combined system with a reversed ORC flow direction such that the organic fluid is preheated first by utilising heat from the SCO2 cycle system and then by geothermal heat has a specific cost corresponding to the maximum net power output of 2880 $/kW, which is the lowest among all the configurations and is 22% lower than that of the standalone SCO2 plant. Annual performance evaluation shows that the combined systems can achieve significant improvements, ranging from 22% to 45%, over the total electricity generation of the standalone SCO2 plant, which de

Journal article

Sun F, Xie G, Song J, Li S, Markides CNet al., 2021, Thermal characteristics of in-tube upward supercritical CO2 flows and a new heat transfer prediction model based on artificial neural networks (ANN), Applied Thermal Engineering, Vol: 194, Pages: 1-13, ISSN: 1359-4311

The potential employment of supercritical carbon dioxide (sCO2) flows in heated tubes in many applications requires accurate and reliable predictions of the thermal characteristics of these flows. However, the ability to predict such flows remains limited due to a lack of a complete fundamental understanding, with traditional prediction capabilities relying on either simple empirical correlations or highly complex and computationally demanding simulation methods both of which limit the design of next-generation systems. To overcome this challenge, a prediction model based on artificial neural network (ANN) is proposed and trained by 5780 sets of experimental wall temperature data from upward flows with a very satisfactory root mean square error (RMSE) and mean relative error that are less than 1.9 °C and 1.8%, respectively. The results confirm that the structured model can provide satisfactory prediction capabilities overall, as well specific performance with mean relative error under the normal, enhanced and deteriorated heat transfer (NHT, EHT and DHT) conditions of 1.8%, 1.6% and 1.7%, respectively. The proposed model’s ability to predict the heat transfer coefficient in these flows is also considered, and it is shown that the mean relative error is less than 2.8%. Thus, it is confirmed that it has a better prediction accuracy than traditional empirical correlations. This work indicates that such ANN methods can provide a real alternative for adoption in select thermal science and engineering applications, shedding a new light and giving added insight into the thermal characteristics of heated supercritical fluids.

Journal article

Song J, Olympios A, Mersch M, Sapin P, Markides Cet al., 2021, Integrated organic Rankine cycle (ORC) and heat pump (HP) systems for domestic heating, ECOS 2021 - The 34rth International Conference On Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, Publisher: ECOS

Space and water heating represent a significant share of the overall energy consumption in the domestic sector. Decarbonising heat, though challenging, is acknowledged as having a key role to play(as exemplifiedby the Domestic Renewable Heat Incentive launched in 2014 in the UK, amongst other)in achievingemissionsreduction targets andalleviatingproblems related to energy shortage and environmental deterioration. Novel, highly efficientheating technologies have attracted increasing interest in this context, in particular in regions with colderclimatesand higherheating demands. Specifically, thermally-driven heat-pumping technologies are a promising solution to meetingenergy-efficiency targets by increasing the effectiveheat-to-fuelratio(HFR)of heatingsystems. In this paper,thermally-driven integrated organic Rankine cycle (ORC) and heat pump (HP) systems are proposed for domestic heating applications, in which the ORC system is driven by heat from fuel (e.g., gas) combustion and generates power to drive an air-source vapour-compression HP system. A heat-transfer fluid is heatedin the condensers of the two sub-systems to the required temperature for heat provision. Two system configurations with reversed heat-transfer fluidflow directions are presented and compared. Suitable, lowglobal-warming-potential (GWP) working fluids for both the ORC and HP systems are considered and parametric optimisation is performed to determine optimal thermodynamic performanceand system layouts. In aconfiguration in whichthe heat-transfer fluidflows firstthroughthe HP condenser andthen through the ORC condenser in series,the HFRreaches values of 1.26-2.04 forair-source temperaturesranging from -15 to 15 °C and for heat provision temperaturesfrom 35 °C to 60 °C.Aperformance enhancement up to 8-19% relative to theconfiguration withthe heat-transfer fluidflowingin thereversedirection, i.e., through the ORC condenser and then theHP condenser in serie

Conference paper

Song J, Wang Y, Wang J, Markides Cet al., 2021, Optimal design of supercritical CO2 (S-CO2) cycle systems for internal combustion engine (ICE) waste-heat recovery considering heat source fluctuations, The 4th European sCO2 Conference 2021, Pages: 205-211

Supercritical CO2 (S-CO2) cycle systems have emerged as an attractive alternative for internal combustion engine (ICE) waste heat recovery thanks to the advantages offered by CO2 as a working fluid , incl uding robust performance and system compactness. The engine exhaust gases are the main available heat source from ICEs with promising thermodynamic potential for further utilisation, and whose conditions, i.e., temperature and mass flow rate, vary based on the ICE operating strategy load. These heat source variations have a critical influence on the performance of a bottoming S-CO2 cycle system, which needs to be carefully considered in the design stage. This paper explore s the optimal design of S-CO2 cycle system s for ICE waste heat recovery considering heat source fluctuations as well as the probability of their occurrence as arising from actual ICE operation. A variety of heat source conditions are selected for separate design s of an S-CO2 cycle system and performance prediction under all possible scenarios is evaluated via detailed design and off design models, so as to select the optimal design that is able to match the heat source fluctuations and exhibit the best performance from thermodynamic and economic perspectives. The advantage of this approach relative the conventional ones that only consider one specific design condition is that it avoid s either over or under sizing of the S-CO2 cycle system, which also achieves comprehensive insight of the interplay between the bottoming heat recovery system and the ICE, and provides valuable guidance for further system optimisation.

Conference paper

Zhao Y, Liu M, Song J, Wang C, Yan J, Markides CNet al., 2021, Advanced exergy analysis of a Joule-Brayton pumped thermal electricity storage system with liquid-phase storage, Energy Conversion and Management, Vol: 231, Pages: 1-19, ISSN: 0196-8904

Pumped thermal electricity storage is a thermo-mechanical energy storage technology that has emerged as a promising option for large-scale (grid) storage because of its lack of geographical restrictions and relatively low capital costs. This paper focuses on a 10 MW Joule-Brayton pumped thermal electricity storage system with liquid thermal stores and performs detailed conventional and advanced exergy analyses of this system. Results of the conventional exergy analysis on the recuperated system indicate that the expander during discharge is associated with the maximum exergy destruction rate (13%). The advanced exergy analysis further reveals that, amongst the system components studied, the cold heat exchanger during discharge is associated with the highest share (95%) of the avoidable exergy destruction rate, while during charge the same component is associated with the highest share (64%) of the endogenous exergy destruction rate. Thus, the cold heat exchanger offers the largest potential for improvement in the overall system exergetic efficiency. A quantitative analysis of the overall system performance improvement potential of the recuperated system demonstrates that increasing the isentropic efficiency of the compressor and turbine from 85% to 95% significantly increases the modified overall exergetic efficiency from 37% to 57%. Similarly, by increasing the effectiveness and decreasing the pressure loss factor of all heat exchangers, from 0.90 to 0.98 and from 2.5% to 0.5% respectively, the modified overall exergetic efficiency increases from 34% to 54%. The results of exergy analyses provide novel insight into the innovation, research and development of pumped thermal electricity storage technology.

Journal article

Calise F, Cappiello FL, Vicidomini M, Song J, Pantaleo AM, Abdelhady S, Shaban A, Markides CNet al., 2021, Energy and economic assessment of energy efficiency options for energy districts: case studies in Italy and Egypt, Energies, Vol: 14, Pages: 1-24, ISSN: 1996-1073

In this research, a technoeconomic comparison of energy efficiency options for energy districts located in different climatic areas (Naples, Italy and Fayoum, Egypt) is presented. A dynamic simulation model based on TRNSYS is developed to evaluate the different energy efficiency options, which includes different buildings of conceived districts. The TRNSYS model is integrated with the plug-in Google SketchUp TRNSYS3d to estimate the thermal load of the buildings and the temporal variation. The model considers the unsteady state energy balance and includes all the features of the building’s envelope. For the considered climatic zones and for the different energy efficiency measures, primary energy savings, pay back periods and reduced CO2 emissions are evaluated. The proposed energy efficiency options include a district heating system for hot water supply, air-to-air conventional heat pumps for both cooling and space heating of the buildings and the integration of photovoltaic and solar thermal systems. The energy actions are compared to baseline scenarios, where the hot water and space heating demand is satisfied by conventional natural gas boilers, the cooling demand is met by conventional air-to-air vapor compression heat pumps and the electric energy demand is satisfied by the power grid. The simulation results provide valuable guidance for selecting the optimal designs and system configurations, as well as suggest guidelines to policymakers to define decarbonization targets in different scenarios. The scenario of Fayoum offers a savings of 67% in primary energy, but the associated payback period extends to 23 years due to the lower cost of energy in comparison to Naples.

Journal article

Zhou AZ, Li XS, Ren XD, Song J, Gu CWet al., 2020, Thermodynamic Analysis of Supercritical Carbon Dioxide Brayton Cycle Based on the Prediction of the Radial Inflow Turbine Efficiency, Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics, Vol: 41, Pages: 2891-2899, ISSN: 0253-231X

Turbine is one of the core components of the supercritical carbon dioxide (S-CO2) cycle. Generally, the radial inflow turbine is adopted for the small mass flow rate cases. The turbine efficiency is closely related to the cycle design parameters. The turbine efficiency is usually set as a constant value in S-CO2 cycle studies. According to our survey, there are few researches about the influence of the turbine efficiency prediction on the S-CO2 cycle performances. In this paper, the S-CO2 recompression cycle model based on the one dimensional (1D) radial inflow turbine is proposed. Under different cycle parameters, the comparison of S-CO2 cycle thermodynamic performances based on 1D and constant turbine efficiency is conducted. The results reveal that the proper constant turbine efficiency can be applied when cycle parameters vary. However, it's important to investigate the off-design turbine efficiency when the heat source mass flow rate changes.

Journal article

Fatigati F, Vittorini D, Wang Y, Song J, Markides CN, Cipollone Ret al., 2020, Design and operational control strategy for optimum off-design performance of an ORC plant for low-grade waste heat recovery, Energies, Vol: 13, Pages: 5846-5846, ISSN: 1996-1073

The applicability of organic Rankine cycle (ORC) technology to waste heat recovery (WHR) is currently experiencing growing interest and accelerated technological development. The utilization of low-to-medium grade thermal energy sources, especially in the presence of heat source intermittency in applications where the thermal source is characterized by highly variable thermodynamic conditions, requires a control strategy for off-design operation to achieve optimal ORC power-unit performance. This paper presents a validated comprehensive model for off-design analysis of an ORC power-unit, with R236fa as the working fluid, a gear pump, and a 1.5 kW sliding vane rotary expander (SVRE) for WHR from the exhaust gases of a light-duty internal combustion engine. Model validation is performed using data from an extensive experimental campaign on both the rotary equipment (pump, expander) and the remainder components of the plant, namely the heat recovery vapor generator (HRVH), condenser, reservoirs, and piping. Based on the validated computational platform, the benefits on the ORC plant net power output and efficiency of either a variable permeability expander or of sliding vane rotary pump optimization are assessed. The novelty introduced by this optimization strategy is that the evaluations are conducted by a numerical model, which reproduces the real features of the ORC plant. This approach ensures an analysis of the whole system both from a plant and cycle point of view, catching some real aspects that are otherwise undetectable. These optimization strategies are considered as a baseline ORC plant that suffers low expander efficiency (30%) and a large parasitic pumping power, with a backwork ratio (BWR) of up to 60%. It is found that the benefits on the expander power arising from a lower permeability combined with a lower energy demand by the pump (20% of BWR) for circulation of the working fluid allows a better recovery performance for the ORC plant with respect to t

Journal article

Song J, Li X, Wang K, Markides CNet al., 2020, Parametric optimisation of a combined supercritical CO2 (S-CO2) cycle and organic Rankine cycle (ORC) system for internal combustion engine (ICE) waste-heat recovery, Energy Conversion and Management, Vol: 218, Pages: 1-15, ISSN: 0196-8904

Supercritical CO2 (S-CO2) power-cycle systems are a promising technology for waste-heat recovery from internal combustion engines (ICEs). However, the effective utilisation of the heat from both the exhaust gases and cooling circuit by a standalone S-CO2 cycle system remains a challenge due to the unmatched thermal load of these heat sources, while a large amount of unexploited heat is directly rejected in the system’s pre-cooler. In this paper, a combined-cycle system for ICE waste-heat recovery is presented that couples an S-CO2 cycle to a bottoming organic Rankine cycle (ORC), which recovers heat rejected from the S-CO2 cycle system, as well as thermal energy available from the jacket-water and exhaust-gas streams that have not been utilised by the S-CO2 cycle system. Parametric optimisation is implemented to determine operating conditions for both cycles from thermodynamic and economic perspectives. With a baseline case using a standalone S-CO2 cycle system for an ICE with a rated power output of 1170 kW, our investigation reveals that the combined-cycle system can deliver a maximum net power output of 215 kW at a minimum specific investment cost (SIC) of 4670 $/kW, which are 58% and 4% higher than those of the standalone S-CO2 cycle system, respectively. A range of ICEs of different sizes are also considered, with significant performance improvements indicating a promising potential of exploiting such combined-cycle systems. This work motivates the pursuit of further performance improvements to waste-heat recovery systems from ICEs and other similar applications.

Journal article

Song J, Li X, Ren X, Tian H, Shu G, Markides Cet al., 2020, Supercritical CO2-cycle configurations for internal combustion engine waste-heat recovery: A comparative techno-economic investigation, 33rd International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2020), Publisher: ECOS

Supercritical-CO2(S-CO2) cycle systems have appeared as an attractive option for waste-heat recovery from internal combustion engines(ICEs) thanks to the advantages offered by CO2as a working fluid, which is nontoxic and non-flammable, and does not suffer decomposition at high temperatures. Since the high density of CO2in the supercritical region enables compact component design, various S-CO2cycle systemconfigurations have been presented involving different layouts and combinations of heat exchangers with which to enhance heat recovery from both engine exhaust gases and jacket waterstreams. Despite the thermodynamicperformance improvement offered by more complex configurations, the additional heat exchangers bring extra costs and therefore key thermo-economic decisions need to be considered carefully during the design and development of suchsystems. This paper seeks to conduct both thermodynamic and economic (cost) assessments of a variety of S-CO2cycle system configurationsin ICE waste-heat recovery applications, with results indicating that in some cases a significant thermodynamic performance improvement can compensate the extra costs associated with a morecomplex system structure. The comparison results across a range ofICEs can also be a valuable guide for the early-stage S-CO2cycle system design in ICE waste-heat recovery andother similar applications.

Conference paper

Song J, Loo P, Teo J, Markides CNet al., 2020, Thermo-economic optimization of Organic Rankine Cycle (ORC) systems for geothermal power generation: A comparative study of system configurations, Frontiers in Energy Research, Vol: 8, ISSN: 2296-598X

The suitability of organic Rankine cycle (ORC) technology for the conversion of low- and medium-grade heat sources to useful power has established this as a promising option in geothermal power-generation applications. Despite extensive research in this field, most of which has focused on parametric analyses and thermodynamic performance evaluations, there is still a lack of understanding concerning the comparative performance of different plant configurations from both thermodynamic and economic perspectives. This study seeks to investigate the thermo-economic performance of subcritical and transcritical geothermal ORC power-plants, while considering a range of working fluids and the use of superheating and/or recuperation. A specific case study based on the exploitation of a medium-temperature geothermal heat source (180 °C, 40 kg/s) is conducted. Multi-objective optimization is performed to maximize the power/exergy efficiency (i.e., resource use) and to minimize the payback period. Different optimized configurations are compared and the influence on system performance of superheating, recuperation, and subcritical vs. transcritical operation are evaluated. The results reveal that superheating is preferable for working fluids with low critical temperatures, but hinders the performance of fluids whose critical temperature is higher. Recuperation is not attractive under most operating conditions, since the thermodynamic performance improvement and cooling water saving cannot compensate the cost associated with the installation of the additional heat exchanger. Finally, transcritical ORC systems are favored thanks to the better thermal match between the heat source and the working fluid in these configurations. A more generalized geothermal heat source is then considered to explore the optimal configuration over a range of heat sources, which indicates that non-recuperated transcritical-cycle systems with working fluids whose critical temperature is close to the

Journal article

Wang Y, Song J, Oyewunmi OA, Wang J, Zhao P, Dai Y, Markides CNet al., 2020, Integrated optimisation of organic Rankine cycle systems considering dynamic responses, Pages: 577-588

The organic Rankine cycle (ORC) has emerged as a promising and attractive technology for power generation from low- and medium-temperature heat sources. While a considerable amount of research effort has been devoted to the optimisation of ORC system under steady operating conditions, dynamic responses to various fluctuations in the heat source conditions are generally ignored; such transients in the heat source, however, may lead to safety issues and significant performance losses. In this paper, an optimisation method integrated with system dynamic responses is proposed to achieve optimal operating parameters for ORC systems. This method is implemented to obtain the best thermodynamic performance, as well as a secure and safe operation of the ORC system, and to maintain the working fluid in a saturated or superheated state during the expansion process. The effects of different design constraints (i.e., evaporation pressure, condensation pressure, pinch-point temperature differences, and degree of superheat) on the system's dynamic response are investigated, in order to choose appropriate design constraints corresponding to different heat-source variations. Thermodynamic optimisation is implemented for an ORC system exploiting a heat source with different condition variations, and results of the system's dynamic responses are compared with those obtained without such considerations. It is found that the dynamic responses of ORC systems to heat-source fluctuations need to be carefully considered in the design stage of such systems, in order to ensure safe and efficient operation.

Conference paper

Song J, Li X, Ren X, Tian H, Shu G, Gu C, Markides CNet al., 2020, Thermodynamic and economic investigations of transcritical CO2-cycle systems with integrated radial-inflow turbine performance predictions, Applied Thermal Engineering, Vol: 165, ISSN: 1359-4311

Transcritical CO2 (TCO2) cycle systems have emerged as a promising power-generation technology in certain applications. In conventional TCO2-cycle system analyses reported in the literature, the turbine efficiency, which strongly determines the overall system performance, is generally assumed to be constant. This may lead to suboptimal designs and optimization results. In order to improve the accuracy and reliability of such system analyses and offer insight into how knowledge of these systems from earlier analyses can be interpreted, this paper presents a comprehensive model that couples TCO2-cycle calculations with preliminary turbine design based on the mean-line method. Turbine design parameters are optimized simultaneously to achieve the highest turbine efficiency, which replaces the constant turbine efficiency used in cycle calculations. A case study of heat recovery from an internal combustion engine (ICE) using a TCO2-cycle system with a radial-inflow turbine is then considered, with results revealing that the turbine efficiency is influenced by the system’s operating conditions, which in turn has a significant effect on system performance in both thermodynamic and economic terms. A more generalized heat source is then considered to explore more broadly the role of the turbine in determining TCO2-cycle power-system performance. The more detailed turbine-design modelling approach allows errors of the order of up to 10-20% in various predictions to be avoided for steady-state calculations, and potentially of an even greater magnitude at off-design operation. The model allows quick preliminary designs of radial-inflow turbines and reasonable turbine performance predictions under various operating conditions, and can be a useful tool for more accurate and reliable thermo-economic studies of TCO2-cycle systems.

Journal article

Li X, Song J, Yu G, Liang Y, Tian H, Shu G, Markides CNet al., 2019, Organic Rankine cycle systems for engine waste-heat recovery: Heat exchanger design in space-constrained applications, Energy Conversion and Management, Vol: 199, ISSN: 0196-8904

Organic Rankine cycle (ORC) systems are a promising solution for improving internal combustion engine efficiencies, however, conflicts between the pressure drops in the heat exchangers, overall thermodynamic performance and economic viability are acute in this space-constrained application. This paper focuses on the interaction of the heat exchanger pressure drop (HEPD) and the thermo-economic performance of ORC systems in engine waste-heat recovery applications. An iterative procedure is included in the thermo-economic analysis of such systems that quantifies the HEPD in each case, and uses this information to revise the cycle and to resize the components until convergence. The newly proposed approach is compared with conventional methods in which the heat exchangers are sized after thermodynamic cycle modelling and the pressure drops through them are ignored, in order to understand and quantify the effects of the HEPD on ORC system design and working fluid selection. Results demonstrate that neglecting the HEPD leads to significant overestimations of both the thermodynamic and the economic performance of ORC systems, which for some indicators can be as high as >80% in some cases, and that this can be effectively avoided with the improved approach that accounts for the HEPD. In such space-limited applications, the heat exchangers can be designed with a smaller cross-section in order to achieve a better compromise between packaging volume, heat transfer and ORC net power output. Furthermore, we identify differences in working fluid selection that arise from the fact that different working fluids give rise to different levels of HEPD. The optimized thermo-economic approach proposed here improves the accuracy and reliability of conventional early-stage engineering design and assessments, which can be extended to other similar thermal systems (i.e., CO2 cycle, Brayton cycle, etc.) that involve heat exchangers integration in similar applications.

Journal article

Song J, Simpson M, Wang K, Markides Cet al., 2019, Thermodynamic assessment of combined supercritical CO2 (SCO2) and organic Rankine cycle (ORC) systems for concentrated solar power, International Conference on Applied Energy 2019

Concentrated solar power (CSP) systems are acknowledged as a promising technology for solar energy utilisation. Supercritical CO2 (SCO2) cycle systems have emerged as an attractive option for power generation in CSP applications due to the favourable properties of CO2 as a working fluid. In order to further improve the overall performance of such systems, organic Rankine cycle (ORC) systems can be used in bottoming-cycle configuration to recover the residual heat. This paper presents a thermodynamic performance assessment of a combined SCO2/ORC system in a CSP application using parabolic-trough collectors. The parametric analysis indicates that the heat transfer fluid (HTF) temperature at the inlet of the cold tank, and the corresponding HTF mass flow rate, have a significant influence on the overall system performance. The results suggest that the combined system can offer significant thermodynamic advantages at progressively lower temperatures. Annual simulations for a case study in Seville (Spain) show that, based on an installation area of 10,000 m2, the proposed combined cycle system could deliver an annual net electricity output of 2,680 MWh when the HTF temperature at the cold tank inlet is set to 250 °C, which is 3% higher than that of a stand-alone CO2 cycle system under the same conditions. Taking the size of the thermal storage tanks into consideration, a lower HTF temperature at the cold tank inlet and a lower mass flow rate would be desirable, and the combined system offers up to 66% more power than the stand-alone version when the HTF inlet temperature is 100 °C.

Conference paper

Unamba CK, Sapin P, Li X, Song J, Wang K, Shu G, Tian H, Markides CNet al., 2019, Operational optimisation of a non-recuperative 1-kWe organic Rankine cycle engine prototype, Applied Sciences, Vol: 9, Pages: 3024-3024, ISSN: 2076-3417

Several heat-to-power conversion technologies are being proposed as suitable for waste-heat recovery (WHR) applications, including thermoelectric generators, hot-air (e.g., Ericsson or Stirling) engines and vapour-cycle engines such as steam or organic Rankine cycle (ORC) power systems. The latter technology has demonstrated the highest efficiencies at small and intermediate scales and low to medium heat-source temperatures and is considered a suitable option for WHR in relevant applications. However, ORC systems experience variations in performance at part-load or off-design conditions, which need to be predicted accurately by empirical or physics-based models if one is to assess accurately the techno-economic potential of such ORC-WHR solutions. This paper presents results from an experimental investigation of the part-load performance of a 1-kWe ORC engine, operated with R245fa as a working fluid, with the aim of producing high-fidelity steady-state and transient data relating to the operational performance of this system. The experimental apparatus is composed of a rotary-vane pump, brazed-plate evaporator and condenser units and a scroll expander magnetically coupled to a generator with an adjustable resistive load. An electric heater is used to provide a hot oil-stream to the evaporator, supplied at three different temperatures in the current study: 100, 120 and 140 ∘ C. The optimal operating conditions, that is, pump speed and expander load, are determined at various heat-source conditions, thus resulting in a total of 124 steady-state data points used to analyse the part-load performance of the engine. A maximum thermal efficiency of 4.2 ± 0.1% is reported for a heat-source temperature of 120 ∘ C, while a maximum net power output of 508 ± 2 W is obtained for a heat-source temperature at 140 ∘ C. For a 100- ∘ C heat source, a maximum exergy efficiency of 18.7 ± 0.3% is achieved. A detailed exergy analysis all

Journal article

Li X, Song J, Simpson M, Wang K, Sapin P, Shu G, Tian H, Markides Cet al., 2019, THERMO-ECONOMIC COMPARISON OF ORGANIC RANKINE AND CO2 CYCLE SYSTEMS FOR LOW-TO-MEDIUM TEMPERATURE APPLICATIONS, 5th International Seminar on ORC Power Systems

Conference paper

Xia L, Li X, Song J, Ren X, Gu Cet al., 2019, Design and Analysis of S-CO2 Cycle and Radial Turbine for SOFC Vehicle Waste-Heat Recovery, JOURNAL OF THERMAL SCIENCE, Vol: 28, Pages: 559-570, ISSN: 1003-2169

Journal article

Zhou AZ, Song J, Ren XD, Li XSet al., 2019, The Study and Analysis of Supercritical Carbon Dioxide Brayton Cycle and Its Radial Inflow Turbine, Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics, Vol: 40, Pages: 1233-1239, ISSN: 0253-231X

The thermodynamic parameters of supercritical carbon dioxide (S-CO2) are preliminarily designed in this study and the output power is about 1.5 MW. The design of a radial inflow turbine, one of the core components of the S-CO2 cycle, is accomplished. Numerical simulation and study of off-design performance are also conducted. The simulation results show that the overall flow parameters including mass flow rate and efficiency achieves the design goals, and the calculation values are in good agreement with design values trend. The prediction results of off-design performance are consistent with the simulation ones.

Journal article

Unamba C, Li X, Song J, Wang K, Shu G, Tian H, Sapin P, Markides CNet al., 2019, Off-design performance of a 1-kWe organic Rankine cycle (ORC) system, 32nd International Conference on Efficiency, Costs, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2019), Publisher: ECOS

Several heat-to-power conversion technologies are being proposed as suitable for waste heat recovery (WHR) applications, including thermoelectric generators, hot-air (e.g., Ericsson or Stirling) engines, and vapour-cycle engines such as steam or organic Rankine cycle (ORC) power systems. The latter has demonstrated the highest efficiencies at low and intermediate scales and heat-source temperatures. However, ORC systems suffer a deterioration in performance at part-load or off-design conditions, and the high global warming potential (GWP) or flammability of common working fluids is an increasing concern. This paper presents the experimental investigation of a 1-kWe ORC test facility under time-varying heat-source conditions. It aims to compare the part-load performance of various architectures with different working fluids, namely: (i) R245fa, which is widely used in ORC systems, and (ii) low-GWP HFOs. The experimental apparatus is composed of a rotary-vane pump, brazed-plate evaporators and condensers, and a scroll expander with an adjustable load. An electric heater is used to provide a hot oil stream at three different temperatures: 80, 100 and 120 °C. The optimal operating conditions, i.e., pump speed and expander load, are determined for each architecture at various heat-source conditions. A maximum thermal efficiency of 2.8% is reported for a heat-source temperature of 100 °C, while a maximum net power output of 430 W is obtained for a heat source at 120 °C. An exergy analysis allows us to quantify the contribution of each component to the overall exergy destruction. The share of the evaporator, condenser and expander units remain major for all three heat-source conditions, while the exergy destroyed in the pump is negligible in comparison (below 4%).

Conference paper

Song J, Ren X-D, Li X-S, Gu C-W, Zhang M-Met al., 2018, One-dimensional model analysis and performance assessment of Tesla turbine, APPLIED THERMAL ENGINEERING, Vol: 134, Pages: 546-554, ISSN: 1359-4311

Journal article

Song J, Li X-S, Ren X-D, Gu C-Wet al., 2018, Performance improvement of a preheating supercritical CO2 (S-CO2) cycle based system for engine waste heat recovery, ENERGY CONVERSION AND MANAGEMENT, Vol: 161, Pages: 225-233, ISSN: 0196-8904

Journal article

Zhou A, Song J, Li X, Ren X, Gu Cet al., 2018, Aerodynamic design and numerical analysis of a radial inflow turbine for the supercritical carbon dioxide Brayton cycle, APPLIED THERMAL ENGINEERING, Vol: 132, Pages: 245-255, ISSN: 1359-4311

Journal article

Song J, Li X-S, Ren X-D, Gu C-Wet al., 2018, Performance analysis and parametric optimization of supercritical carbon dioxide (S-CO2) cycle with bottoming Organic Rankine Cycle (ORC), ENERGY, Vol: 143, Pages: 406-416, ISSN: 0360-5442

Journal article

Song J, Ren XD, Gu CW, 2018, Investigation of engine waste heat recovery using supercritical CO<inf>2</inf> (S-CO<inf>2</inf>) cycle system

Primary energy consumption of diesel engines is increasingrapidly and strict emission standards are introduced by thegovernment. Interests in engine waste heat recovery have beenrenewed to alleviate the energy shortage and emission issues.Supercritical CO2 (S-CO2) cycle has emerged as a promisingmethod considering its compact structure and system safety levelin addition to the environmental friendly characteristics. Thispaper explores the potential of using S-CO2 cycle system forengine waste heat recovery. Both heat load from the lowtemperature jacket cooling water and the high temperatureengine exhaust gas are intended to be recovered. In the originalsystem, the jacket cooling water is used to preheat the S-CO2working fluid and the engine exhaust gas is utilized in thepreheater. As an optimized scheme, system with two preheatersis presented. The engine exhaust gas is further cooled in a hightemperature preheater after the jacket cooling water in the lowtemperature preheater. The available heat load from these twoheat sources can be entirely recovered. However, the increasingpreheating temperature suppresses the regeneration effect. Aregeneration branch is then added in the system. Part of the SCO2 working fluid from the compressor goes into a lowtemperature regenerator and then converges with the other partfrom the two preheats. A deeper utilization of the regenerationheat load is achieved and performance enhancement of the SCO2 cycle system is expected. The maximum net power outputof the system with regeneration branch reaches 82.8 kW, whichresults in an 8.5% increment on the engine power output.

Conference paper

Song J, Ren XD, Gu CW, 2017, Performance Analysis of Dual-loop Heat Recovery System, Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics, Vol: 38, Pages: 1491-1495, ISSN: 0253-231X

A dual-loop system is designed to recover the waste heat of a diesel engine in this paper. The high-temperature (HT) loop utilizes the heat load of the engine exhaust gas, and the low-temperature (LT) loop uses the heat load of the jacket cooling water and the residual heat of the HT loop sequentially. These two loops are coupled via a shared heat exchanger. Water is selected as the working fluid for the HT loop while organic fluids are used in the LT loop. The influence of the HT loop parameters on the performance of the LT loop is evaluated. The simulation results reveal that under different operating conditions of the HT loop, the pinch point of the LT loop occurs at different locations and therefore, results in different evaporation temperatures and other thermal parameters. The maximum net power output of the dual-loop ORC system reaches 115.1 kW, which leads to an increase of 11.6% on the original power output of the diesel engine.

Journal article

Song J, Gu C-W, Li X-S, 2017, Performance estimation of Tesla turbine applied in small scale Organic Rankine Cycle (ORC) system, APPLIED THERMAL ENGINEERING, Vol: 110, Pages: 318-326, ISSN: 1359-4311

Journal article

Song J, Gu CW, 2017, 1-D model analysis of Tesla Turbine for small scale Organic Rankine Cycle (ORC) system

Energy shortage and environmental deterioration are two crucial issues that the developing world has to face. In order to solve these problems, conversion of low grade energy is attracting broad attention. Among all of the existing technologies, Organic Rankine Cycle (ORC) has been proven to be one of the most effective methods for the utilization of low grade heat sources. Turbine is a key component in ORC system and it plays an important role in system performance. Traditional turbine expanders, the axial flow turbine and the radial inflow turbine are typically selected in large scale ORC systems. However, in small and micro scale systems, traditional turbine expanders are not suitable due to large flow loss and high rotation speed. In this case, Tesla turbine allows a low-cost and reliable design for the organic expander that could be an attractive option for small scale ORC systems. A 1-D model of Tesla turbine is presented in this paper, which mainly focuses on the flow characteristics and the momentum transfer. This study improves the 1-D model, taking the nozzle limit expansion ratio into consideration, which is related to the installation angle of the nozzle and the specific heat ratio of the working fluid. The improved model is used to analyze Tesla turbine performance and predict turbine efficiency. Thermodynamic analysis is conducted for a small scale ORC system. The simulation results reveal that the ORC system can generate a considerable net power output. Therefore, Tesla turbine can be regarded as a potential choice to be applied in small scale ORC systems.

Conference paper

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