The small solar thermal power plant is being developed with funding from EU Horizon 2020 Program. The plant is configured around a 2-kWel Organic Rankine Cycle turbine and solar field, made of Fresnel mirrors. The solar field is used to heat thermal oil to the temperature of about 240 °C. This thermal energy is used to run the Organic Rankine Cycle turbine and the heat rejected in its condenser (about 18-kWth) is utilized for hot water production and living space heating. The plant is equipped with a latent heat thermal storage to extend its operation by about 4 hours during the evening building occupancy period. The phase change material used is Solar salt with the melting/solidification point at about 220 °C. The total mass of the PCM is about 3,800 kg and the thermal storage capacity is about 100 kWh. The operation of the plant is monitored by a central controller unit. The main components of the plant are being manufactured and laboratory tested with the aim to assemble the plant at the demonstration site, located in Catalonia, Spain. At the first stage of investigations the ORC turbine will be directly integrated with the solar filed to evaluate their joint performance. During the second stage of tests, the Latent Heat Thermal Storage will be incorporated into the plant and its performance during the charging and discharging processes will be investigated. It is planned that the continuous filed tests of the whole plant will be performed during the 2018–2019 period.

Totally enclosed air to air cooled (TEAAC) generator with IC6A1A6 (as per IEC 60034-6) cooling is a widely accepted generator cooling solution for squirrel cage induction generators (SCIG) used in wind power generation, where the generator has two cooling systems, internal and external. The internal cooling is a closed loop system, where a shaft mounted mechanical fan helps in recirculating air inside the generator, and transfers the heat from the generator into an air-to-air heat exchanger. The external cooling system is a separate ventilation system creating airflow from the nacelle through the heat exchanger and removing the heat outside the nacelle with the help of an electrical fan mounted near the non-drive end of the generator. Cooling improvement of generator and bearing windings for performance enhancement is a well known research topic in turbo-generation as well as wind energy. Various winding design effort has been made in past for efficient generator cooling for turbogenerator as well as for wind turbine generator. With the increasing demand of power output, winding and bearing temperature class reaching its limit. Challenge is to come up with a solution for improving the performance of generator in terms of reducing temperature experienced by windings and at the same time reducing the cost. Detailed testing has been done on a test turbine to compare results obtained from open ventilated solution IC3A1 (as per IEC60034-6) and IC6A1A6 cooling for the squirrel cage induction generator. Paper presents advantages in case of using IC3A1 cooling where temperature of windings reduced substantially in comparison with IC6A1A6 cooling. To avoid contamination led windings and bearings hotspots, presented IC3A1 cooling configuration uses a unique design with inlet duct, filters, outlet duct and wire mesh.

In order to pursue superior cycle efficiency and lower power generation cost for the CSP plants, two S-CO 2 –Brayton–cycle–based power cycles with different utilization methods of the residual heat recover of the top S-CO 2 Brayton cycle (SCBC) are investigated to seek alternatives to the stand-alone S-CO 2 cycle as the power block of concentrated solar power plants. The residual heat released by the top S-CO 2 cycle are either utilized to drive a LiBr absorption chiller (AC) for further chilling of the CO 2 fluids exiting the precooler before entering the main compressor inlet temperature or recovered by an organic rankine cycle (ORC) for generating electricity. Thermo-economic analysis and optimization are performed for the SCBC–AC and SCBC–ORC, respectively. The results show that the thermal and exergetic efficiencies of the SCBC–AC are comparable with those of the SCBC–ORC in low pressure ratio conditions ( PR <2.7) but are apparently lower than SCBC–ORC when PR is over 2.7. The LCOE of the CSP plant integrated with SCBC–AC is more sensitive to the change of PR . The optimal PR to maximum the cycle efficiency or minimize the plant LCOE for the SCBC–ORC is higher than that for the SCBC–AC, while the optimal recuperator effectiveness to minimize the LCOE of CSP plant integrated with SCBC–ORC is lower than that of SCBC–AC. The optimization results show that the thermo-economic performance of the SCBC–AC is comparable to that of the SCBC–ORC. Significant η ex improvement and LCOE reduction can be obtained by both the two combined cycles relative to the stand-alone S-CO 2 cycle. The maximal η ex improvements obtained by the SCBC–ORC and SCBC–AC are 6.83% and 4.12%, respectively. The maximal LCOE reduction obtained by the SCBC-ORC and SCBC–AC are 0.70 ȼ / (kW·h) and 0.60 ȼ / (kW·h), respectively.

Urban solid waste generation has drastically grown around the world, requiring creative, ecologically correct and sustainable solutions to be developed. This work considers a problem of thermodynamic optimization of extracting the most energy from a stream of hot exhaust produced by urban solid waste incineration, considering a stoichiometric combustion model, when the contact heat transfer area is fixed. For that, a mathematical model is introduced to evaluate the rate of heat generation due to the waste incineration process, and the exergetic (power) rate captured by a heat recovery steam generator (heat exchanger). The numerical results show that when the (cold) receiving stream boils in the counterflow heat exchanger; the thermodynamic optimization consists of locating the optimal capacity rate of the cold current. At the optimum, the cold side of the heat transfer surface is divided into three sections: preheating of liquid, boiling and superheating of steam. Experimental results are in good qualitative and quantitative agreement with the numerically calculated mathematical model results. Microalgae cultivated in large-scale vertical tubular compact photobiorreactors are investigated to treat the emissions produced by the incineration, and to increase the efficiency of the global system via cogeneration of co-products with high aggregated commercial value.

Development of alternative, clean and renewable energy production from different hydrocarbon materials helps to partially replace the limited resources of fossil fuels and also help reduce carbon emissions from fossil fuels that drives global warming. Biomass and bio-wastes are renewable and sustainable hydrocarbon resources, which can be used for energy and fuels production along with permanent disposal of plastic wastes. Landfills of wastes is unsustainable with additional problems of non-degradability and growing burden to the environment and society. Co-pyrolysis and co-gasification of biomass with different types of plastic wastes has shown to provide enhanced product yields and quality for syngas and liquid fuel production. To date, limited information is available on the understanding of chars produced from co-pyrolysis. The effect of co-pyrolysis on the type, quality and yield of chars produced is essential for efficient utilization of a wide variety of biomass, bio-waste and plastic waste resources. This paper provides information on the effect of plastic addition to the pyrolysis of biomass as well as the quality and quantity of char produced with different amounts of plastic waste added at different pyrolysis temperatures. TGA reactor was used for all these investigations and the quality of char produced was examined from the perspective of char combustion for energy production. Char is commonly produced as a by-product from pyrolysis and gasification reactors. Carbonization temperatures investigated were in the range of 573–773 K for 30 min using pinewood biomass, while recycled polyethylene terephthalate was used as plastic waste. The investigations revealed that chars produced from co-pyrolysis especially for carbonization temperature (T c ) of 673 K and above behaved completely differently than the chars produced from separate pyrolysis of biomass and plastic waste under the same pyrolysis conditions. These chars produced from co-pyrolysis were more uniform in their behavior in oxidation environment, with higher heat flow for almost similar quantities of chars during oxidation. This was conjectured to be from enhanced quality of chars produced having increased C content (from increased heavy aromatics and efficient loss of volatiles) during co-pyrolysis without any loss of char yield. The char yield was found to be equal or higher during co-pyrolysis compared to the weighted aggregate of individual pyrolysis. These investigations provided novel results on the behavior and capabilities of chars produced from co-pyrolysis of biomass and plastic wastes to provide a new avenue for the quality enhancement of bio-chars and efficient utilization of carbonaceous solid waste resources.

Renewable energy is one of the most promising solutions to energy shortage that may occur in the future particularly in remote areas. Solar cells suffer from the problem of high temperature, which reduces the electrical efficiency and operational life. In this study we investigate a new hybrid technique of cooling and voltage induction. A set of small generators installed on the back of a solar panel operating under the influence of heat and magnetic energy are called thermo-magneto-electric generators (TMEG). A modeling study was done using COMSOL Multiphysics5.2a (COMSOL) software as a package to simulate the physical states of the system. This study showed that a TMEG has the ability to improve the efficiency as a result of reducing the temperature. An induction voltage is also an output of the system and can be combined with the output of the solar panel composing the hybrid system.

Homogeneous charge compression ignition (HCCI) is a combustion technology which has received increased attention of researchers in the combustion field for its potential in achieving low oxides of nitrogen (NO x ) and soot emission in internal combustion (IC) engines. HCCI engines have advantages of higher thermal efficiency and reduced emissions in comparison to conventional internal combustion engines. In HCCI engines, ignition is controlled by the chemical kinetics, which leads to significant variation in ignition time with changes in the operating conditions. This variation limits the practical range of operation of the engine. Additionally, since HCCI engine operation combines the operating principles of both spark ignition (SI) and compression ignition (CI) engines, HCCI engine parameters such as compression ratio and injection timing may vary significantly depending on operating conditions, including the type of fuel used. As such, considerable research efforts have been focused on establishing optimal conditions for HCCI operation with both conventional and alternative fuels. In this study, numerical simulation is used to investigate the effect of compression ratio on combustion and emission characteristics of an HCCI engine fueled by pure biodiesel. Using a zero-dimensional (0-D) reactor model and a detailed reaction mechanism for biodiesel, the influence of compression ratio on the combustion and emission characteristics are studied in Chemkin-Pro. Simulation results are validated with available experimental data in terms of incylinder pressure and heat release rate to demonstrate the accuracy of the simulation model in predicting the performance of the actual engine. Analysis shows that an increase in compression ratio leads to advanced and higher peak incylinder pressure. The results also reveal that an increase in compression ratio produces advanced ignition and increased heat release rates for biodiesel combustion. Emission of NO x is observed to increase with increase in compression ratio while the effect of compression ratio on emissions of CO, CO 2 and unburned hydrocarbon (UHC) is only marginal.

The evaluation of power plant uprates has traditionally been based on the definition of several ‘typical’ operating modes based on historical data and a — more or less detailed — model of the plant that is compared in current configuration against the same base model including the modifications under consideration. For the economic assessment of the uprate, annual operating hours are allocated to the operating points, and fuel savings and/or additional output predicted by the model due to the modifications are evaluated against the expected investment cost. In this study, the authors demonstrate that this classic approach contains risks in several aspects, in particular: • the representativeness of the ‘typical’ operating modes, • the accuracy of the model, and • the correctness of the assumptions in the allocation of operating hours. Utilizing the example of an actual uprate of a heat recovery steam generator (HRSG) in a large utility plant of an Austrian steel company, a new approach for an evaluation based on ‘big data’ is presented that uses a full year of operational data in hourly granularity for both, the verification of the accuracy of the plant model, and the evaluation of the effect of the uprate. The authors also provide details of the underlying technologies that allow for both, excellent match of operational data with a fully-fledged heat balance software and fast evaluation of tens of thousands of calculation cases.

The traditional organic Rankine cycle (ORC) is operated below critical point. However, the specific heat of the working fluid undergoes tremendous change near the critical point. This can improve the thermal performance of the system due to the enhancement of heat transfer coefficient within the heat exchanger. However, the strong temperature dependence of thermo-physical properties of the working fluid especially at near the critical point requires much more efforts in designing a heat exchanger. Hence, more elaborate calculation involving stepwise integration is needed as far as accuracy is concerned. Therefore the heat exchanger is divided into several segments. The outlet temperatures of the first segment serve as the input parameters for the second segment, and the process is carried out further on. The fluid properties are calculated with the actual bulk temperature of each segment. With increasing number of segments, better resolution of temperature distribution of both heat source and working fluid within the heat exchanger is achieved. In the present study, a plate heat exchanger was numerically examined by using R-245fa as a working fluid at a supercritical condition. The effects of the working pressure and mass flow rate were examined in detail. For all cases in this study, the maximum of the total heat transfer rate was achieved by a working pressure of 3700 kPa, especially close to critical pressure. It is found that at a working pressure of 4000 kPa and mass flow rate ranging from 1 kg/s to 1.75 kg/s, the total heat transfer rate was independent of the mass flow rate.

Traditionally, water is used in thermal power plant for heat rejection processes such as in the steam condenser for use in a Rankine cycle. Typically, research has shown that approximately 2 litres of water are required to generate 1 kWh of electricity on a wet-cooling system; which on a bigger scale could translated to more than 11000000 m 3 per year of make-up water for a 600 MWe coal-fired plant. The ever-increasing cost of water resources as well as the water resource scarcity have paved a path to dry-cooling systems which alternatively provide a significant cooling potential. However, dry-cooling systems performance are generally driven by the atmospheric conditions which at time do not meet the desired cooling temperatures resulting in significant drop in their performance. Recent developments in cooling technology suggest that hybrid systems (dry-wet) be used to insure good and manageable performances while maintaining the cost of operation at admissible range. In light of the recent draught experienced in South Africa, attention was drawn to evaluation of deluged systems performance as well as water consumption to increase the public awareness in the field. In this study, a deluged bundle was used to experimentally determine the cooling performance characteristic as well as water consumption for performance management. The above is then considered on a bigger scale to in order to open floor for further discussion on future strategies in term of the South African policy on water usage.

Surface tension and solution evaporation of aqueous solutions of sodium lauryl sulfate (SLS), ECOSURF™ EH-14, and ECOSURF™ SA-9 under natural convection is examined through experimental methods. SLS is an anionic surfactant while EH-14 and SA-9 are environmentally-friendly nonionic surfactants. Surfactants are known to affect evaporation performance of solutions and are studied in relation to water loss prevention and heat dissipation. Surfactants could be useful under drought conditions which present challenges to water management on a yearly basis in arid areas of the world. Recent water scarcity in the greater Los Angeles area, south eastern Africa nations, eastern Australia and eastern Mediterranean countries has high cost of water loss by evaporation. Surfactants are studied as a potential method of suppressing evaporation in water reservoirs. Surfactants are also studied as performance enhancers for the working fluid of heat dissipation devices, such as pulsating heat pipes used for electronics cooling. Some surfactants have been shown to lower thermal resistances and friction pressure in such devices and thereby increase their efficiency. The static surface tensions of the aqueous-surfactant solutions are measured with surface tensiometer using Wilhelmy plate method. The surfactants are shown to lower surface tension significantly from pure water. The surface tension values found at the Critical Micelle Concentration are 33.8 mN/m for SLS, 30.3 mN/m for EH-14, and 30.0 mN/m for SA-9. All three surfactants reduced natural convection water loss over 5 days with SLS showing the greatest effect on evaporation rates. The maximum evaporation reduction by each surfactant from distilled water with no surfactants after 5 days is 26.1% for SLS, 20.8% for EH-14, and 18.4% for SA-9.

High-temperature Gas-cooled Reactor Pebble-bed Module (HTR-PM) is under construction in Shidao Bay, Shandong of China. It is supposed to be the world’s first pebble-bed modular commercial demonstration plant for High Temperature Gas-cooled Reactor (HTGR). In HTR-PM project, water-Rankine cycles have been used in the power conversion system. Meanwhile, supercritical carbon dioxide (S-CO2) Brayton cycle has shown great potentials for future HTGR technology. Comparing with typical helium Brayton cycle, in S-CO2 cycle where critical properties of carbon dioxide are utilized, compressor work may reduce significantly and thermal efficiency may improve greatly. Furthermore, the general sizes of S-CO2 cycle equipment, such as heat exchanger and turbine, would be orders of magnitude smaller than water-Rankine system at similar power output. Therefore, parameters study of S-CO2 were conducted in this paper for future HTGR. Firstly, a physical model of S-CO2 Brayton cycles was built and the performance of cycles were analyzed. Secondly, compression ratio, temperature ratio, the inlet temperature of turbine, inlet parameters of compressor, and recuperated effectiveness were discussed as key cycle parameters. For heat capacities of CO2 are significantly different as a function of temperature and pressure, flow recompression was considered. Calculation was based on a split-flow cycle configuration. The split flow ratio was also analyzed. Finally, the parameters of S-CO2 cycle were optimized for HTGR. In conclusion, S-CO2 Brayton cycle will be a good option for future HTGR.

To advance the utilization of the solar energy and coal resources as well as improve the flexibility of coal-based power plant, an improved solar-coal hybrid system for methanol production and power generation is proposed and thermodynamically analyzed. In the proposed system, the concentrated solar energy at high-temperature is used for heating the coal gasification to produce syngas for methanol synthesis; the waste material and heat from coal-to-methanol process are efficiently recovered in the conjunct power generation system; and the surplus electric power is optionally used for methanol synthesis by electrolysis process during the off-peak period. Through employing the proposed system, the solar energy and electricity (optional) could be effectively converted into methanol as stable chemical energy together with a preferable overall system thermal efficiency. The thermodynamic analysis results showed that, the overall energy and exergy efficiencies reaches 48.6 and 47.3%, respectively; the equivalent solar-to-methanol conversion efficiency can soar to 66.2%; and the net electricity-to-methanol efficiency reaches 61.6% with the power load reducing from 48.7% to 31.0%.

In this work, the energy efficiency of the lithium-ion batteries (LIB) with graphite anode and LiFePO 4 cathode (G/LFP) at different nominal capacities and charge/discharge rates is studied through multiphysics modeling and computer simulation. After characterizing all the heat generation sources in the cell, the total heat generation in LIBs is calculated and the charge/discharge efficiency plots at different temperatures are obtained. Since G/LFP LIBs have a wide range of applications in passenger and commercial electric vehicles (EVs), the result of this study assist engineer toward more efficient battery pack design.

Due to the peculiar physical properties, supercritical carbon dioxide (sCO 2 ) is considered as a promising working fluid in power generation cycles with high reliability, simple structure and great efficiency. Compared with the general thermal systems, the variable properties of sCO 2 make the system models obtained by the traditional modelling method more complex. Besides, the pressure distribution in the system will affect the distribution of the fluid properties, the fluid properties influencing the heat transfer process will produce an impact on the temperature distribution which will in turn affect the pressure distribution through the mass flow characteristics of all components. This contribution introduces the entransy-based power flow method to analyze and optimize a recompression sCO 2 power generation system under specific boundary conditions. About the heat exchanger, by subdividing the heat transfer area into several segment, the fluid properties in each segment are considered constant. Combining the entransy dissipation thermal resistance of each segment and the energy conservation of each fluid in each segment offers the governing equations for the whole heat transfer process without any intermediate segment temperatures, based on which the power flow diagram of the overall heat transfer process is constructed. Meanwhile, the pressure drops are constrained by the mass flow characteristics of each component, and the inlet and outlet temperatures of compressors and turbines are constrained by the isentropic process constraints and the isentropic efficiencies. Combining the governing equations for the heat exchangers and the constraints for turbine and the compressors, the whole system is modeled by sequential modular method. Based on this newly developed model, applying the genetic algorithm offers the maximum thermal efficiency of the system and the corresponding optimal operating variables, such as the mass flow rate of the working fluid in the cycle, the heat capacity rate of the cold source and the recompression mass fraction under the given heat source. Furthermore, the optimization of the system under different boundary conditions is conducted to study its influence on the optimal mass flow rate of the working fluid, the heat capacity of the cold source and the maximum system thermal efficiency. The results proposes some useful design suggestions to get better performance of the recompression supercritical carbon dioxide power generation system.

Numerical models for the evaluation of cryo-adsorbent based hydrogen storage systems for fuel cell vehicles were developed and validated against experimental data. These models simultaneously solve the conservation equations for heat, mass, and momentum together with the equations for the adsorbent thermodynamics. The models also use real gas thermodynamic properties for hydrogen. Model predictions were compared to data for charging and discharging both MOF-5™ and activated carbon systems. Applications of the model include detailed finite element analysis simulations as well as full vehicle-level system analyses. The present work provides an overview of the compacted adsorbent MOF-5™ storage prototype system, as well as a detailed computational analysis and its validation using 2-liter prototype test system. The results of these validated computational analyses are then projected to a full scale vehicle system, based on an 80 KW fuel cell with a 20 kW battery. This work is part of the Hydrogen Storage Engineering Center of Excellence (HSECoE), which brings materials development and hydrogen storage technology efforts address onboard hydrogen storage in light duty vehicle applications. The HSECoE spans the design space of the vehicle requirements, balance of plant requirements, storage system components, and materials engineering. Theoretical, computational, and experimental efforts are combined to evaluate, design, analyze, and scale potential hydrogen storage systems and their supporting components against the Department of Energy (DOE) 2020 and Ultimate Technical Targets for Hydrogen Storage Systems for Light Duty Vehicles.

A supplemental main steam condenser cooling system is under development, which utilizes a phase change material (PCM). This PCM rejects heat to the cool atmosphere at night until it is fully frozen. The frozen PCM is available for condenser cooling during peak daytime electric demand. Three calcium chloride hexahydrate (CaCl 2 ·6H 2 O)-based PCMs were selected for development after being characterized using differential scanning calorimetry (DSC). Additives to minimize supercooling and phase separation have demonstrated good performance after long and short-term thermal cycling. Corrosion testing under both isothermal and cycling conditions was conducted to determine long-term compatibility between several common metals and the selected PCMs. Several metals were demonstrated to have acceptably low corrosion rates for long-term operation, despite continual immersion in the selected hydrated salts. A system optimization model was developed, which utilizes a 3D modeling approach called the Layered Thermal Resistance (LTR) model. This model efficiently models the nonlinear, transient solidification process by applying analytic equations to layers of PCM. Good agreement was found between this model and more traditional computational fluid dynamics (CFD) modeling. Next phases of the work includes prototype testing and a techno-economic analysis of the technology.

Static, or motionless, mixers are widely used in applications that involve chemical reactions, heat transfer, blending of fluids, or a combination of these. Within those applications, mixing can affect various parameters such as heat or mass transfer rates, process operating time, cost, safety, and product quality. Therefore, it is crucial to assess the performance of static mixers. In general, their performance is evaluated based on their ability to carry out mixing while minimizing energy loss. To accomplish this, a novel mixing parameter, the M number, is proposed and evaluated. The M number is a unitless parameter that describes the effects of the mixer using entropy change and pressure drop. The parameter is compared to another method of mixing evaluation that relies on Covariance (CoV) change across the mixer. Computational Fluid Dynamics (CFD) is executed using both methods to evaluate two static mixers and compare the results of each method. Potential applications for the M number are discussed and its limitations are noted.

Performance improvement of heat recovery systems has huge potential for energy conservation but puzzles researchers due to the nonlinear coupled properties. The traditional modelling approaches focus on individual components, which introduces numerous non-independent variables and further complicates the system optimization. In this contribution, through the thermo-electric analogy method, the equivalent power flow diagram is built based on the system layout, then the corresponding governing equations are derived according to the circuitous philosophy, which reveals the overall transfer and conversion laws of heat. Then, by analyzing the pressure variations of fluids in various components, the flow resistance balance equations are established, which describes the pressure distribution in circulation loop. Moreover, through combining with the coupling relations between the temperatures and pressures of fluids, the inherent physical constraints among operating parameters are revealed by introducing few intermediate variables, which provides convenience for model computation. On this basis, through reasonably matching the mass flow rates of working fluids, the net power generation is maximized under variable working conditions. The optimization results indicate the parameters variation of flue gas significantly impacts the optimal operating state of system, while the empirical constant backpressure operation strategy apparently deviates from the optimums, and the most deviation reaches 8.2%.

This paper addresses modeling, design, and experimental assessment of a Gamma type low-temperature differential free-piston Stirling engine. The most advanced third-order design analysis method is used to model, simulate and optimize the engine. Moreover, the paper provides an experimental parametric investigation of engine physical parameters and operating conditions on the engine performance. The experimental test results are presented for a model validation, which shows about a 5% to 10% difference in the simulation results. The aim of this study is to design a Stirling engine capable of harvesting low-temperature waste heat effectively and economically and convert it to power. The engine prototype is designed to increase the engine performance by eliminating the main losses occurred in conventional Kinematic engines. Thus, elastic diaphragm pistons are used in this prototype to eliminate the surface friction of the moving parts, the use of lubricant, and to provide appropriate seals. In addition, flat plate heat exchangers, linear flexure bearing, a stainless-steel regenerator and a polyurethane displacer are outlined as the main components of the engine. Experiments successfully confirm the design models for output power and efficiency. Furthermore, it is revealed that the displacer-to-piston natural frequency ratio is an important design point for free-piston Stirling engines and should be addressed in the design for optimum power output.