In renewable-based microgrids, intermittency caused by some energy sources highlights the important role of energy storage systems. Nowadays, hydrogen and thermal energy storage are expected to play key roles in grid-scale applications, for facilitating effective penetration of clean energy sources. This paper, through a multilevel control framework for the energy management of a renewable and reversible solid oxide based microgrid, develops medium level controls accounting for the dynamic behaviour of storage systems. The storage systems considered are a hydrogen storage tank and a thermal energy storage based on phase change material technology. In particular, the proposed algorithm is helpful in the microgrid design phase as well as for clearly assessing high-level energy management strategies, since dynamic and transient behaviours of tanks during both charging and discharging phases are validated. In this way, top-level energy management strategies can be further refined and optimized in addition to a techno-economic design being pursued, primarily through shrinking the initial sizes of storages and thereby achieving significantly lower initial capital costs. For the analyzed microgrid, its feasibility is demonstrated by reducing by as much as 40% the size of the hydrogen tank and by up to 20% the energy capacity of the thermal storage. Finally, the proposed medium level control in a multilevel algorithm framework for a hydrogen-based microgrid is also seen to be fruitful for avoiding waste energy, which can be beneficial against the background of distributed energy systems acting in virtual power plants.

This paper proposes and examines a highly integrated microgrid based on a reversible solid oxide cell, aimed at satisfying electrical and thermal loads of a 20-unit residential complex as well as the demands of electric and fuel cell vehicles. Such a system has been conceived as a profitable ready-made solution to be embedded into existing plants already equipped with renewable energy sources (i.e., wind farm and photovoltaic panels) by means of a reversible solid oxide cell and energy storage technologies. A dynamic programming-based routine has been suitably implemented as an algorithm for both the electrical and thermal sides of the plant for managing the power split indices. In addition, an external routine has been deployed to consider economic aspects; in particular, attention has been paid to the levelized cost of energy, allowing for comparisons with current reliable energy generation technologies. The analyses involve parametric assessments of multiple reversible solid oxide cell sizes and economic discount rates while fixing the lifetime of the plant at 30 years. In accordance with the results of the optimal microgrid design, by exploiting 100% of the rSOC working time (shared by mode as 40% fuel cell and 60% electrolyzer) a simple payback period of 5.97 years is achieved along with a levelized cost of energy index value in the 0.1 (sic)/kWh-0.2 (sic)/kWh range.

In reversible solid oxide cell (rSOC)-based renewable microgrids connected to the network, control logic optimizing the power split with the grid is needed. The benefits associated with such configuration are assessed and compared to an islanded reversible microgrid, previously designed via a model-based approach. Multiple loads are met, including those of a residential complex as well as electric and fuel cell vehicle fleets. The energy storage system consists of a rSOC and hydrogen and thermal storage tanks. The targeted optimal power split annual trajectory is found through dynamic programming. Suitable simplifying assumptions are introduced to develop a fast reduced-order sub-model from the original islanded rSOC microgrid, thus conceiving the optimal control problem as a one state dynamic programming task. Due to the connection to the grid, the energy storage system no longer has to compensate for the difference between generation and demand, thus enabling economic rSOC sub-scaling. Finding the best control strategy and resizing jointly lead to capital and operating expense reductions. The optimization outcomes indicate how a 60% reduction in rSOC nominal power allows for a simple payback period of 40% less than for the islanded design, as well as for proper rSOC capacity exploitation.

The use of solar energy to preheat natural gas before a city gate station (CGS) for reducing fuel consumption and environmental emissions is investigated in a real CGS. All analyses are conducted with a 1-h time-step throughout the entire year so that seasonal climate changes are accounted for precisely. A thermodynamic analysis of the hybrid system is performed with TRNSYS and verified with THERMOFLEX so as to ensure reliability. In addition, dynamic exergetic, exergoeconomic, and exergoenvironmental analyses for the proposed system are carried out. A life cycle assessment (LCA) based on Eco-indicator 99 is performed using SIMA PRO to compute the environmental impacts for each component of the system. The exergetic, exergoeconomic, and environmental analyses are performed in Engineering Equation Solver (EES) software. To perform the transient exergetic, exergoeconomic, and environmental analyses, the results of the thermodynamic analysis from TRNSYS are automatically imported into the EES code. The advanced exergetic, exergoeconomic, and exergoenvironmental analyses are performed to better determine components that have high potentials for improving the system; potentials are considered based on the exergy destruction, exergetic cost of destruction, and environmental impacts associated with exergy destruction.

Due to continuous growth in population and sharp increase in energy and food demand, research on alternative energy sources independent of fossil fuels has increased over the last decade. Moreover, limitations on greenhouse gas emissions by developed and developing countries are imposing much pressure on the energy sector worldwide to use renewable energy sources such as solar, wind, biomass, hydro, and geothermal. Food production is one of the biggest industries in the world, and it consumes a large amount of energy in the form of heat and electricity. In this work, agro-product drying technologies powered by solar energy are presented and discussed. Different types of solar dryers based on direct, indirect and mixed modes are described. Moreover, energy, exergy, economic, and environmental analyses for these technologies are presented to determine the main parameters affecting the dryer performance. The results indicate that the air mass flow rate, temperature, moisture content, and drying time are the most important parameters in solar dryer performance. Finally, a comparative assessment of the performance of different existing solar dryer has been highlighted with a detail scope of future works.

A multi-objective optimization of a combined air cooled gas turbine and steam turbine system is carried out using non-dominated sorting genetic algorithm II (NSGA-II). In the optimization process, performance and environmental aspects of the system are considered, and the first level of exergy destruction splitting is incorporated. Such parameters as second law efficiency, ratio of total avoidable exergy destruction rate to total exergy destruction rate, and CO2 emission in exhaust gases, are considered as the objective functions. Once the model of the system is constructed in engineering equation solver (EES) software and validated, the gas turbine inlet temperature and compressor pressure ratio are considered as the decision variables based on the performed sensitivity analysis. Then, EES is coupled with MATLAB and the multi-objective optimization is performed for various values of gas turbine blade cooling air fractions. By comparing the obtained Pareto optimal points with those of the base case, considerable improvements in the values of the objective functions are observed.

Energy storage technologies, including storage types, categorizations and comparisons, are critically reviewed. Most energy storage technologies are considered, including electrochemical and battery energy storage, thermal energy storage, thermochemical energy storage, flywheel energy storage, compressed air energy storage, pumped energy storage, magnetic energy storage, chemical and hydrogen energy storage. Recent research on new energy storage types as well as important advances and developments in energy storage, are also included throughout.

Electrical energy storage systems are indispensable elements in a renewable power generation plant, since sources such as solar and wind are by nature intermittent and therefore not always available when necessary. Reversible solid oxide cells (rSOCs) can be fruitfully integrated within renewable microgrids, thus providing an effective solution to the mismatch between energy demand and production from renewable sources. The ob-jective of this work is the development of a modeling tool enabling both optimal sizing and proper year-through energy management of an rSOC-based renewable microgrid, supplying electricity and hydrogen to a residential complex and a passenger car fleet consisting of both electric and fuel cell vehicles. This innovative multiple load energy system entails developing suitable modeling tools to properly account for the randomness of both renewable energy production and load demand, the latter being treated via historical data and Monte Carlo-based procedures. To this aim, both hydrogen and thermal storage systems are involved in the plant design, whereas their charge sustaining management, here adopted to guarantee self-sufficiency features as required by robust and resilient distributed systems, are addressed through suited constraints. The resulting constrained optimization tool yields both design data and control guidelines, which can serve as a basis for subsequent development of low-level control strategies, as well as the refined design of grid-connected rSOC-based microgrids. A technoeconomic assessment shows that the payback period is reasonable, ranging between 6 and 10 years depending on the rSOC cost scenario.

The feasibility of solar-assisted absorption heat pumps for space heating is assessed with exergoeconomics and compared with gas boilers and solar heating systems for the town of Sarein in Iran. In the study, single-effect LiBr/H2O and NH3/H2O absorption and absorption compression-assisted heat pumps are analyzed for heating loads of 50-2 MW. Using the geothermal hot springs located in Sarein as heat sources for refrigerant evaporation, the problem of freezing is prevented. In addition, a multi-objective optimization is performed to specify the optimal design points considering the temperatures of the evaporator and generator as decision parameters. Simulations show that the gas boiler and the solar heating system have the lowest and second lowest values of exergy efficiency, at about 45% and 35% lower than the exergy efficiency for NH3/H2O absorption systems. The maximum achievable exergy efficiency for the NH3/H2O and LiBr/H2O absorption systems are 0.23 and 0.25, respectively. But, the solar heating system has the highest product unit cost, mainly due to its high capital costs. The minimum obtainable product unit costs for the NH3/H2O and LiBr/H2O absorption systems occur in April, and are about 22 $/GJ and 55 $/GJ, respectively.

This paper presents recent advances by an international team of five countries – Canada, U.S., China, Slovenia and Romania – on the development and scale-up of the copper chlorine (Cu-Cl) cycle for thermochemical hydrogen production using nuclear or solar energy. Electrochemical cell analysis and membrane characterization for the CuCl/HCl electrolysis process are presented. Constituent solubility in the ternary CuCl/HCl/H2O system and XRD measurements are reported in regards to the CuCl2 crystallization process. Materials corrosion in high temperature copper chloride salts and performance of coatings of reactor surface alloys are examined. Finally, system integration is examined, with respect to scale-up of unit operations, cascaded heat pumps for heat upgrading, and linkage of heat exchangers with solar and nuclear plants. 1* Corresponding Author: Professor and Dean, Faculty of Engineering and Applied Science, Memorial University of Newfoundland, St. John’s, NL, A1B 3X5, Email: gnaterer@mun.ca; Phone: (709) 864-8864 2 Manager, Hydrogen Isotopes Technology Branch, Canadian Nuclear Laboratories, Chalk River, Ontario, Canada, K0J 1J0 3 Professor of Mechanical Engineering, UOIT, 2000 Simcoe Street North, Oshawa, Ontario, Canada, L1H 7K4 4 Professor of Mechanical Engineering, UOIT, 2000 Simcoe Street North, Oshawa, Ontario, Canada, L1H 7K4 5 Professor of Mechanical Engineering, UOIT, 2000 Simcoe Street North, Oshawa, Ontario, Canada, L1H 7K4 6 Hydrogen Project Manager, UOIT, 2000 Simcoe Street North, Oshawa, Ontario, Canada, L1H 7K4 7 Professor, College of Energy, Xiamen University, Xiamen City, Fujian Province, China, 361102 8 Associate Professor of Chemistry, UOIT, 2000 Simcoe Street North, Oshawa, Ontario, Canada, L1H 7K4 9 Associate Professor, Faculty of Energy Systems and Nuclear Science, UOIT, 2000 Simcoe Street North, Oshawa, Ontario, Canada, L1H 7K4 10 Associate Professor of Mechanical Engineering, UOIT, 2000 Simcoe Street North, Oshawa, Ontario, Canada, L1H 7K4 11 Professor, Faculty of Energy Systems and Nuclear Science, UOIT, 2000 Simcoe Street North, Oshawa, Ontario, Canada, L1H 7K4 12 Assistant Professor of Mechanical Engineering, Memorial University of Newfoundland, St. John’s, NL, A1B 3X5 13 Professor of Mechanical Engineering, Director, Centre for Advanced Coatings Technologies, University of Toronto, Toronto, Ontario, Canada, M5S 3E5 14 Professor of Energy and Mineral Engineering, Pennsylvania State University, 207 Hosler Building, University Park, PA 16802

In this paper, a parallel flow double-effect water-lithium bromide absorption refrigeration cycle is investigated using comprehensive exergy-based analyses. The exergy destruction of each device is calculated and used for further analysis. The performance of the system is optimized for maximum coefficient of performance and exergy efficiency, considering the distribution ratio as a variable using the Golden Section method. The maximum coefficient of performance, i.e. 1.295, is obtained at a high pressure generator temperature of 169.6 degrees C, and the maximum exergy efficiency, i.e. 0.225, is obtained at a high pressure generator temperature of 142.7 degrees C. Advanced exergy analysis, a state of the art thermodynamic method, is employed for diagnosing equipment and cycle malfunctions. Not only can the aforementioned analysis pinpoint the source of irreversibility, it also provides the avoidable irreversibility as well. The results show that the endogenous part of the exergy destruction is much larger than the exogenous part, implying it is better to focus on component efficiencies to improve system performance. Moreover, the unavoidable part of the total exergy destruction is much larger than the avoidable portion, indicating that exergy destruction cannot be decreased owing to technical limitations of equipment.

Combined cycles are used for various reasons, including to increase the efficiency of power generation system. In this study, a gas turbine cycle is combined with a pressurized water reactor (PWR) power plant to increase the total plant efficiency. In this novel cycle, saturated steam produced in the steam generators of the nuclear power plant is superheated by the hot combustion gases exiting the gas turbine. An exergoeconomic analysis is carried out and the effects of compressor pressure ratio and gas turbine inlet temperature are investigated on the net power output, the first and second law efficiencies, the total cost rate and the specific cost of the produced work. The results show that there is an optimum pressure ratio for each gas turbine inlet temperature. The combined cycle total cost rate and the specific cost of the produced work for a gas turbine inlet temperature of 1500 K and a compressor pressure ratio of 13 are determined to be 41,882 $/h and 31.63 $/MWh, respectively. (C) 2018 Elsevier Ltd. All rights reserved.

Exergy analysis, thermoeconomics, and combined pinch and exergy analyses are useful methods for improving design and performance of processes such as thermal power plants. However, these methods are usually applied separately. In this paper, the methods are applied simultaneously to the 423-MW Neka combined-cycle power plant and the 315-MW Ramin steam power plant to evaluate and compare the performance of the systems and their components under different load conditions. To perform these analyses, a computer simulation and analysis program is developed. The simulator can predict the cycle behavior for different operating conditions with relative errors of less than 1.5%. The models are refined using performance test data from these plants. The system information is displayed graphically to visualize the performance of the systems for different conditions by applying combined pinch-exergy analysis. To better illustrate the plant performance and benefits of knowing the exergy destructions, the exergy destruction level (EDL) and the exergy cost destruction level (ECDL) are proposed and applied. Correspondingly, a new graphical representation is developed to illustrate the performance of each component based on exergoeconomic analysis, providing enhanced combined pinch-exergy and EDL/ECDL representations.

Mining is the typical method of extracting coal, but it can only recover 20%–25% of global coal resources. Mining has many challenges and requires much time, resources, and personnel. A new method of coal extraction, underground coal gasification (UCG), could address some of these problems while greatly expanding recoverable coal resources. Underground coal gasification is a gasification process applied to in situ coal seams. When combined with carbon capture and storage, UCG has significant potential for providing a relatively clean energy source. This chapter reviews key concepts and technologies of UCG, providing insights into this developing coal extraction method. A case study is also presented that illustrates the modeling and analysis of UCG and assesses the feasibility of using an auxiliary power plant and utilizing waste heat rejected syngas processing, to supply the required energy associated with amine-based carbon dioxide capture and compression processes.

There are two procedures to solve reliability problems: analytical techniques and stochastic simulation. Each has advantages and disadvantages. One of the important analytical techniques for repairable systems is the Markov method. This method uses state space to consider all states that may occur. To use this method for complex systems, the model of the system must be simplified. For this purpose, many states are removed from the space state. In this way, although the probabilities of the states are calculated, these probabilities are often not accurate. In the present work, a new approach is proposed that considers both the simplified system and the calculation of the probability of each state accurately. The new method can calculate the probabilities by taking into account minimum states. Site utility systems are used to illustrate the procedure for applying this method. Site utilities have several repairable components (e.g. steam turbine, gas turbine, HRSG, de-aerator, boiler). So, this system can generate a large and complex state space for which it is difficult to calculate the probability. The new procedure can reduce the number of states and aggregates of the exploded state space due to the high number of components. The results show that the new procedure can predict state probabilities with high accuracy.

A multi-output energy-generation system for providing electricity and cooling for a grid-independent Ontario dairy farm is investigated. A range of biogas-fed micro turbines coupled with absorption refrigeration units and an organic Rankine cycle for heat recovery are considered to meet the electrical and cooling needs of farm sizes between 250 and 6000 cows. An energy analysis is conducted for the entire system and each subsystem. It is found that absorption refrigerators make best use of the energy in the exhaust stream, and increasing the amount of energy input to this subsystem increases overall system energy efficiency. Overall system energy efficiencies vary from 9 to 40%, increasing with farm size, while the energy efficiency of the bottoming cycle is 32-40% depending on farm size. For the range of configurations considered, electricity generation exceeds the farm's internal energy requirements, presenting opportunities for the sale of electricity.

Two configurations of double-flash geothermal power plants, one is combined with water desalination and one integrated with absorption heat transformation and water desalination, are proposed and investigated from the viewpoint of exergoeconomics. The main purpose of investigated systems is the simultaneous generation of electrical power and distilled water. A three-objective optimization procedure is performed to determine the optimal design points, considering for all configurations the decision parameters to be the pressures of low and high-pressure flash chambers and the temperatures of the evaporator and generator. The optimization aims to minimize the product unit cost, while maximizing the electric power generated and the production rate of distilled water. The Pareto frontiers for each configuration are drawn as part of the procedure. It is shown that, at constant and equal pressures of the high-pressure flash chamber, the product unit cost for the system combined with the absorption heat transformer is the lower of the two systems considered. In addition, under the optimized conditions, the product unit costs are approximately equal for the two studied configurations. However, the value of generated power for the system with an absorption heat transformer is about 17% greater than for the alternate system. Moreover, the system integrated with an absorption heat transformer has higher thermal and exergy efficiencies, at about 20% and 3%, respectively.

The present paper reports the results from modelling and experimentation with a lithium-ion battery pack operating at room temperature and under varying discharge rates. The variation in the internal resistance of the cell with change in the temperature is investigated experimentally. The prismatic Li-ion battery pack is discharged at 1C, 2C, 3C and 4C and significant parameters, such as pack voltage, temperature, and state of charge, are obtained. This is accomplished by connecting three LiFePO4 20 A h capacity prismatic batteries in series and applying 18 thermocouples at various locations on the surface of all three cells. The results show that there is a significant increase in battery surface temperature with an increase in discharge rate. The highest average surface temperature of the battery pack (56.5 degrees C) is observed experimentally at a 4C discharge rate, and the lowest (30.7 inverted perpendicular C) at 1C based on modelling. Similarly, the maximum total heat generation (59.2 kJ) is observed at 4C experimentally and the minimum (37.5 degrees C) at 1C from modelling. A comparison of the modelling results with the experimentally determined temperature, voltage and heat generation shows good agreement. Also, the internal resistance of the cell is observed to increase as the state of charge decreases, and to decrease with increasing cell temperature.