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This study aims to develop, and examine a cogeneration system for electric power, hydrogen, and ammonia production. A modified Rankine cycle is configured to supply power. An electrolyze unit and an ammonia synthesis reactor are used to provide hydrogen and ammonia. The system is investigated from technical and economic aspects. The inquiry outcomes disclose that the reaction pressure and hydrogen to nitrogen molar ratio have mainly affected the ammonia production rate increment. The system energy and exergy efficiencies as well as the total unit cost of the product are at about 50.47 %, 51.41 %, and 638.3 $/GJ, respectively. The results show that the exergy destruction rate of the system is 89.797 MW. Moreover, 6.438 kg/h of hydrogen and 6.528 kg/s of ammonia are attainable. The sweeping sensitivity investigation on the economic aspect reveals that the reaction pressure, input hydrogen molar ratio, and hydrogen to nitrogen molar ratio have a positive effect on the sum unit cost of the product's decrement. Finally, the thermodynamic sensitivity examination outcomes affirm that altering reaction temperature leads to technical inefficiencies in the proposed cogeneration system. [ABSTRACT FROM AUTHOR]

A development of biomass cogeneration facilities business comes with many challenges such as operational compliance and budget constraints. Maintenance cost is often oppressing some portion of the annual budget. Apparent outage costs due to loss of production during planned operation and maintenance are crucial. It requires a strategic maintenance framework to ensure optimum performance of the biomass cogeneration business. This paper presents a Mix Integer Linear Programming optimization model for the palm oil mill-based cogeneration facility considering fuel cost, electricity cost, maintenance duration and maintenance interval. The model aims to minimize total annual operation costs to ensure tenants can depend on reliable, uninterrupted heat as they deserved from the heat supplier. The sensitivity analysis results determine the lowest annualised cost had impacted by lower fuel and outsource electricity costs, six days maintenance duration, and 1.1 maintenance intervals. [ABSTRACT FROM AUTHOR]

The paper analyses the simultaneous production of heat and electricity by cogeneration using two distinct solutions: with gas turbine and thermal engine. The analysis is made for cogeneration solutions for low and medium power. The advantages of cogeneration energy production are identified in both solutions, so the process of combined and simultaneous production of the two forms of energy achieves an effective primary energy saving (fuel) compared to the separate production of mechanical work (in a thermal power plant) and heat (in a thermal power plant). This fuel economy is reflected from an economic point of view, in the reduction of the fuel costs of the power plant and from an ecological point of view, in the reduction of the pollution of the environment. Conclusions are drawn on the opportunity of using the two solutions depending on maximum demand, power supply time, the degree of flattening (or non-uniformity) of the classified consumption curve and energy demand structure (electrical/thermal). [ABSTRACT FROM AUTHOR]

Abstract We prove that the exactness of direct limits in an abelian category with products and an injective cogenerator J is equivalent to a condition on J which is well-known to characterize pure-injectivity in module categories, and we describe an application of this result to the tilting theory. We derive our result as a consequence of a more general characterization of when inverse limits in the Eilenberg–Moore category of a monad on the category of sets preserve regular epimorphisms. [ABSTRACT FROM AUTHOR]

Abstract We introduce a new family of algebras, called Serre-formal algebras. They are Iwanaga–Gorenstein algebras for which applying any power of the Serre functor on any indecomposable projective module, the result remains a stalk complex. Typical examples are given by (higher) hereditary algebras and self-injective algebras; it turns out that other interesting algebras such as (higher) canonical algebras are also Serre-formal. Starting from a Serre-formal algebra, we consider a series of algebras – called the replicated algebras – given by certain subquotients of its repetitive algebra. We calculate the self-injective dimension and dominant dimension of all such replicated algebras and determine which of them are minimal Auslander–Gorenstein, i.e. when the two dimensions are finite and equal to each other. In particular, we show that there exist infinitely many minimal Auslander–Gorenstein algebras in such a series if, and only if, the Serre-formal algebra is twisted fractionally Calabi–Yau. We apply these results to a construction of algebras from Yamagata [29] , called SGC extensions, given by iteratively taking the endomorphism ring of the smallest generator-cogenerator. We give a sufficient condition so that the SGC extensions and replicated algebras coincide. Consequently, in such a case, we obtain explicit formulae for the self-injective dimension and dominant dimension of the SGC extension algebras. [ABSTRACT FROM AUTHOR]

Abstract We study implications on the unit interval. Like triangular norms and conorms, these implications also may have generators (additive or multiplicative). Although there are constructive proofs of the existence of generators of these operations, they rarely lead to closed formulas. Thus we lack a practical tool for computations of the generators. Recently we have shown that the generators of triangular norms can often be computed from the partial derivatives of the original operations. Here we apply a similar technique to R-implications. Some of the formulas have analogies for triangular norms, some do not. Besides, we show (and avoid) another potential problem of computation of generators of triangular norms, not mentioned before. [ABSTRACT FROM AUTHOR]

Surging in energy demand makes it necessary to improve performance of plant equipment and optimize operation of thermal power plants. Inasmuch as thermal power plants depend on fossil fuels, their optimization can be challenging due to the environmental issues which must be considered. Nowadays, the vast majority of power plants are designed based on energetic performance obtained from first law of thermodynamic. In some cases, energy balance of a system is not appropriate tool to diagnose malfunctions of the system. Exergy analysis is a powerful method for determining the losses existing in a system. Since exergy analysis can evaluate quality of the energy, it enables designers to make intricate thermodynamic systems operates more efficiently. These days, power plant optimization based on economic criteria is a critical problem because of their complex structure. In this study, a comprehensive analysis including energy, exergy, economic (3‐E) analyses, and their applications related to various thermal power plants are reviewed and scrutinized. Several thermal power plants in combined cycles are reviewed comprehensively in the present study. Results of the studies based on energy, exergy, and economic analyses are represented for each type of thermal power plants. Integrating thermal power plants with other cycles will enhance the energetic efficiency. Systems integrating will increase investment cost for the power plants. Exergy analysis provide useful information for enhancement of plants' efficiency. [ABSTRACT FROM AUTHOR]

The cogeneration installations have experienced a particular development due to the energetic crises and, as a result of the Kyoto Protocol, regarding the reduction of the emissions of greenhouse gas. Cogeneration advantages: energy efficiency, economic and ecological advantages. [ABSTRACT FROM AUTHOR]

The stationary power systems with fuel cells offer a great advantage for highly efficient production of electricity and heat. Among the existing fuel cell technologies, the solid oxide fuel cells (SOFC) are considered as a suitable technology for micro- and small-scale power units with output in the range from sub-kW to 50 kW. The hydrocarbonaceous fuel supplied to the system requires pre-treatment in order to convert it into hydrogen-rich gases directed to the anodic compartments of the fuel cell stack. The steam reforming is now considered as a leading technology in stationary applications. For prevention of carbon formation and deposition in the anodic compartments, the sufficient steam to carbon ratio (S/C ratio) has to be maintained in the fuel processor. Depending on the working condition, the SOFC-based system can become water neutral and the necessity to supply make-up water for the steam reforming can be eliminated. In the current study, two stacks connected in series were analysed to define the required parameters at the level of the stacks and at the level of system to allow operation in water neutral conditions. The results of the study are presented and the conditions for achieving water neutrality are discussed. The corresponding current densities should be in range 0.17–0.30 A/cm 2 and 0.06–0.18 A/cm 2 in the first and second stack, respectively. [ABSTRACT FROM AUTHOR]

This paper focuses on the development of a dispatch model for cogeneration systems in industrial plants. The proposed model schedules thermal and electrical outputs of the cogeneration units by minimizing total operating costs in the plant while satisfying operational constraints. The work presents a practical model that depends on easily available data in the industrial environment, i.e., efficiency data available from equipment manufacturers or machine tests. The power to heat ratio is modeled using equipment efficiency data that depends on the cogeneration unit output. This approach allows to represent feasibility regions and supplementary firings without complex thermodynamic relations that require additional data. In order to illustrate the application of the model in real systems, a potassium production plant in Brazil is studied. This case study involves two cogeneration units with supplementary firings and a boiler. Results indicate that the model allows obtaining a dispatch strategy with reduced operating costs when compared with the traditional planning used by plant operators. Three scenarios are simulated and cost savings obtained with the optimized strategy vary between 2.0% and 4.0%, when compared with the corresponding unplanned strategy. [ABSTRACT FROM AUTHOR]

In addition to electricity generation, phosphoric acid fuel cell (PAFC) produces a significant amount of waste heat. In this study, a hybrid system mainly consisting of a PAFC, a thermoelectric generator, and a thermoelectric cooler is proposed to recover the produced waste heat aiming for performance enhancement. Considering thermodynamic and electrochemical irreversible losses within the system, an analytical relationship between the dimensionless electric current of the thermoelectric element and the current density of the PAFC is derived. Analytical formulas for power density and efficiency of the hybrid system are derived. The characteristics and the optimum criteria evaluating the performance parameters are revealed for the studied system. Numerical solutions show that the power density and efficiency of the hybrid system allow 2.3% and 2.8% larger than that of a stand-alone PAFC, respectively. The present hybrid system is found to be feasible and effective. Comprehensive parametric studies are conducted to analyze the effects of operating conditions and design parameters on the proposed system. The conclusions drawn can provide theoretical guidance for PAFC performance enhancements and system designs. [ABSTRACT FROM AUTHOR]

By 1973, low oil prices had provided the production of relatively cheap electricity. A sudden increase in gas prices caused a need for developing energy technologies as well as a need for increasing the efficiency of power plants. At the same time, increased environmental awareness as well as the awareness of the growing scarcity of energy sources required greater attention to preserving the environment and the existing resources, so small and micro cogeneration plants become efficient and competitive energy producers. The United States and Canada are currently lagging behind Europe and Japan in relation to the development of micro cogeneration units, partly because of differences in heating systems, energy prices and political framework. In accordance with the Kyoto Protocol, Japan is obliged to reduce its global warming i.e. gas emissions by 6% of the 1990 level. However, CO2 emissions continue to grow, which means that it is currently estimated that Japan must reduce emissions by 14% to meet the goal. Japan should promote all possible ways to effectively reduce CO2 emissions. In this regard, it continues to give support to micro cogeneration marketing, especially for models suitable for residential buildings. It is estimated that, in the next few years, energy production by cogeneration will reach 75% of the total production at the European level. In Italy, ecological energy makes 30% of the total consumption, in the Netherlands 33%, and in Denmark and the UK it is almost completely present. [ABSTRACT FROM AUTHOR]

A reflective cavity with elliptical cross-section is proposed to couple a burner to three arrays of thermophotovoltaic (TPV) cells. Burner and photoconverter, with triangular section, are located near the two foci of the ellipse. The elliptical cavity is designed to be inserted into a thermo-electric micro-cogenerator for residential use, which exploits the TPV cells to convert visible and infrared radiation generated by the burner into electricity. Taking into account the key construction constraints, several cavity configurations, which differ for components or optical properties, are analysed by ray tracing simulations. The maximum radiation collection efficiency is 62% for the elliptical cavity and is reduced to 48% by introducing quartz protections around the burner and the receiver. A germanium-based photoconverter is developed and manufactured by metalorganic chemical vapour deposition techniques. Each photoconverter can deliver 180 mW/cm 2 (at 230 mV voltage and 55 °C) when illuminated by a blackbody spectrum at 1473 K. The manufacture of the TPV receiver is described and the thermal design aspects are considered. The use of a dichroic filter for a TPV generator configuration based on an elliptical chamber is also evaluated. [ABSTRACT FROM AUTHOR]

The article discusses the economics behind steam cogeneration systems. Cogeneration is reportedly the use of steam to generate electricity and useful heat which allows plants to reduce its dependence on external electrical energy purchases. Also tackled are the thermodynamics of cogeneration, different types of steam turbines, integration of cogeneration into an existing steam system, and control of complicated cogeneration systems.

Bagasse ashes from high efficiency co-generation boilers have dominant filler effect in concrete from a greatly reduced pozzolanic activity because of quartz polymorph phase changes to α-quartz, rather than the often-reported α-cristobalite for bagasse derived silica. Sugar cane bagasse ash used as filler in concretes provided substantial improvements to compressive strengths at up to ≈20%. These combined filler effect and limited pozzolanic activity improved the acid resistance as measured by both mass loss and compressive strength tests. Improved acid resistance suggests pore filling and lowered permeability from the filler effects, whereas the limited pozolanic may be sufficient to shift cement chemistry to more acid resistant silicates mineral systems compared to aluminate minerals (e.g., C 3 A to C 2 S). Similarly, drying shrinkage improved. However, in contrast the rapid chloride permeability tests indicate increased chloride ingress, suggesting increased permeability, but these maybe possibly misleading results generated from the superplasticizer. [ABSTRACT FROM AUTHOR]

Cogeneration (CHP) and Heat Pump (HP) are playing a key role in energy systems due to their high efficiency, especially, in energy refurbishment of buildings and industrial processes. This paper explored the opportunity to couple those two well-established technologies for heating purposes. Basically, the coupling entails limitations and constraints consisting of the mismatch between the power sizes of merchandised machines as well as the deriving technical issues. The main aim of this paper is to analyse the coupling procedure to help HVAC specialists in their job. This paper deals with a simple model formulation, based on the First Law of thermodynamics, for CHP/HP systems rating and off-design operations. Indeed, an analytical method was designed along with the definition of a size factor. Then, a graphical method for coupling CHP and HP was presented so as to be an expeditious tool in designing phase. Finally, two numerical applications were illustrated highlighting the energy performance gains and the high level of operation flexibility. [ABSTRACT FROM AUTHOR]

In this paper, effects of the ambient conditions on performance of cogeneration cycles are analyzed by using exergy analysis method. These cogeneration cycles are the simple cycle, the air preheating cycle, the air-fuel preheating cycle and the inlet air cooling cycle. Also, these cycles are evaluated thermodynamically for different air and fuel mass ratio and the performance of these cycles are compared. The electrical power generation increases about 10-15 % by decreasing the inlet air temperature of the compressor from 25 0C to 0 0C. However, the thermal power decreases about 10 % with decreasing inlet air temperature. During the summer, the electric power can be easily increased 2-7 % by injecting water into the inlet air of the compressor. The exergetic efficiency of cycles is decreased 11-13 %, by decreasing the compressor inlet air pressure from 101.3 kPa to 70.18 kPa. But this change decreases the electric power generation about 25 %. The highest exergy efficiency is obtained for the air-fuel preheated cycle. The simple cycle is the best among the four cycles to obtain high heat rate and heat exergy. The effects of all ambient conditions on these cycles are considered simultaneously, analyzed and compared with each other in this study. [ABSTRACT FROM AUTHOR]

In this study, some improving methods of gas turbine cogeneration cycles are applied on a simple cogeneration cycle. These methods are preheating air, preheating air and fuel, inlet air cooling by using evaporative cooling and absorption cooling. These cogeneration systems are evaluated with respect to energy efficiency (energy utilization factor), exergetic efficiency, electric and heat power, electric-heat energy rate, artificial thermal efficiency and fuel energy saving ratio and are compared with each other. In these analyses, the thermodynamic parameters such as compressing ratio, air and fuel mass ratio and compressor inlet temperatures of the cycles are used. It is concluded that these parameters can be listed from most effective to least effective as air fuel ratio, pressure ratio and compressor inlet temperature. It is also concluded that the most efficient cycle is found to be the air-fuel preheated cycle for obtaining more electric power and less heat power and the simple cycle is the most suitable one for obtaining more heat power and less electric power. [ABSTRACT FROM AUTHOR]

Optimizing consumptions in the field of civil construction led to define energy labels for residential buildings. To calculate the building energy demand the EPgl was determined, i.e. the annual consumption per m 2 of primary energy. This paper examines the technical solutions useful to optimize the energy demands for heating during space-heating season and domestic hot water production (thanks to energy analysis softwares as MC11300 and TRNSYS) and, at the same time, to take into account the financial issues those interventions implied. The total inside heated surface of the building case study is 1204.00 m 2 , hence the inside heated volume is about 3250.80 m 3 . Besides the more traditional interventions concerning the building envelope and its systems, the paper examined the performance of a system obtained through the combination of a cogenerator (CHP) and a heat pump (HP), thus, substituting the conventional boilers of the buildings. CHP+HP solution increases the most the energy label of the building (from a D class with EPgl = 59.62 kW h m −2 year −1 , to an A class, with EPgl = 25.64 kW h m −2 year −1 ), determining an annual energy cost saving of 3,114 € year −1 , allowing to amortize installation costs (54,560 €) in a reasonable payback period, i.e. 15.4 years. This innovative solution in the residential sector can be realized through retrofit interventions on existing buildings, hence it leads the current dwelling towards nZEB with a remarkable benefits for the environment. [ABSTRACT FROM AUTHOR]

The installation of 19 biopower plants for the electricity cogeneration during the whole year has begun in Cuban sugar mills. As biomass fuel they will use the bagasse produced during the sugar harvest, and to complete the rest of the year they will use marabou and energy cane. The latter will originate juices not suitable for sugar production, but good as source of carbon for alcoholic fermentation. Nevertheless, not all these mills have an annexed alcohol distillery, what encouraged looking for solutions to their preservation. To this aim, face to face interviews were carried out, the available experimental data on preservation of industrial juices of energy cane were used and processed with the DataFit 9.0.59 software to obtain mathematical prediction models for the behavior in time of the preserved juices, with the restriction variables Brix > 70%, Acidity < 1,5% and UfcT/g < 160 000. It was determined that the simple technology uses the existent industrial equipment, the preservation during 180 days is feasible and contribute with $ 9,57 CUP/t in a preliminary way to the economic feasibility. It is suggested to use this new raw material for alcohol production as soon as possible, to reduce storage costs. [ABSTRACT FROM AUTHOR]

Let S be a monoid. A right S--act A is said to be retractable if for each subact B of A, Hom(A, B) ≄ Θ. In this paper we define an S--act A to be coretractable if Hom(A/B, A) ≄ {0}, for every proper subact B of A. Our objective is to characterize retractable and coretractable acts by properties of underlying sets and monoids and investigate the relation between these properties of acts with some "projective or injective likes" properties. Clearly every generator is retractable and every cogenerator is coretractable in the category of S--acts. It turns out that for a monoid S with a left zero all free acts are coretractable if and only if Hom(A, S) ≄ {0}, for each S--act A. [ABSTRACT FROM AUTHOR]

Cogeneration is considered as one of the promising energy efficient techniques for producing electricity and useful thermal energy from a single fuel source. This paper describes a feasibility study of the implementation of different cogeneration options to a paper mill to evaluate their energy saving potentials and economic benefits. The investigated systems in this paper are gas turbine, steam turbine and combined cycle cogeneration options evaluated and compared based on energy utilisation factor and Annualised Life Cycle Cost (ALCC) analysis. The results of energy analysis show that all Combined Heat and Power (CHP) systems satisfy the thermal energy needs of the mill while the combined cycle cogeneration option generates the highest amount of electric energy equal to 10.91 MW. The gas turbine cogeneration system is shown as the most advantageous system from overall energy point of view with the highest energy utilisation factor of 78% meeting the heat and electric requirements of the mill and exporting 21,329 MWh of additional electricity to the grid. Economic feasibility results also show that an overall saving of 5.12 million US$ can be achieved by implementing the gas turbine cogeneration system to the mill making it as the best cogeneration option with the least overall ALCC of 1.34 million US$ and the maximum percentage of CO 2 emission reduction (68%) when compared with the other options. [ABSTRACT FROM AUTHOR]

The increasing use of smartphone technology in people's daily lives and its continuous development lead to the inevitable use of mobile applications because of their easy access anytime and anywhere. In this study, a new Android application for smartphones is developed and presented for the remote control of a micro-cogeneration system from a mobile device without the need to be near the system. The mobile application consists of five different windows through which real-time data on the most important variables of the system can be observed at any time. Additionally, the application allows the user to select the system's desired operating mode among a total of five possibilities. Alarms and warnings are also shown along with the detailed status of the main variables of the groups forming the system. Moreover, the application can graphically show the progression of variables at any time, and a history of the changes to the system is available. An experimental practice based on the "use of current mobile applications" for a subject of the Master of Thermal Engineering is proposed as a pedagogical method that involves the procedure "learning by doing," in which students can realize the great advantages of using these technologies. [ABSTRACT FROM AUTHOR]

Life cycle energy use and GHG emissions are assessed for coal-based synthetic natural gas (SNG) and power cogeneration/polygenereation (PG) technology and its competitive alternatives. Four main SNG applications are considered, including electricity generation, steam production, SNG vehicle and battery electric vehicle (BEV). Analyses show that if SNG is produced from a single product plant, the lower limits of its life cycle energy use and GHG emissions can be comparable to the average levels of coal-power and coal-BEV pathways, but are still higher than supercritical and ultra supercritical (USC) coal-power and coal-BEV pathways. If SNG is coproduced from a PG plant, when it is used for power generation, steam production, and driving BEV car, the life cycle energy uses for PG based pathways are typically lower than supercritical coal-power pathways, but are still 1.6–2.4% higher than USC coal-power pathways, and the average life cycle GHG emissions are lower than those of all coal-power pathways including USC units. If SNG is used to drive vehicle car, the life cycle energy use and GHG emissions of PG-SNGV-power pathway are both much higher than all combined coal-BEV and coal-power pathways, due to much higher energy consumption in a SNG driven car than in a BEV car. The coal-based SNG and power cogeneration technology shows comparable or better energy and environmental performances when compared to other coal-based alternatives, and is a good option to implement China’s clean coal technologies. [ABSTRACT FROM AUTHOR]

We investigate one-dimensional 'generalized convolution behaviors' (gen. beh.) that comprise differential and delay-differential behaviors in particular. We thus continue work of, for instance, Brethé, van Eijndhoven, Fliess, Gluesing-Luerssen, Habets, Loiseau, Mounier, Rocha, Vettori, Willems, Yamamoto, Zampieri of the last twenty-five years. The signal space for these behaviors is the space E of smooth complex-valued functions on the real line. The ring of operators is the commutative integral domain E′ of distributions with compact support with its convolution product that acts on E by a variant of the convolution product and makes it an E′-module. Both E and E′ carry their standard topologies. Closed E′-submodules of finite powers of E were introduced and studied by Schwartz already in 1947 under the name 'invariant varieties' and are called gen. beh. here. A gen. beh. is called a behavior if it can be described by finitely many convolution equations. The ring E′ is not noetherian and therefore the standard algebraic arguments from one-dimensional differential systems theory have to be completed by methods of topological algebra. Standard constructions like elimination or taking (closed) images of behaviors may lead to gen. beh. and therefore the consideration of the latter is mandatory. It is not known whether all gen. beh. are indeed behaviors, but we show that many of them are, in particular all autonomous ones. The E′-module E is neither injective nor a cogenerator and, in particular, does not admit elimination in Willems' sense. But the signal submodule PE of all polynomial-exponential signals is injective for finitely generated modules and thus admits elimination. This is a useful replacement and approximation of the injectivity of E since the polynomial-exponential part of any gen. beh. is dense in it. We also describe a useful replacement of the cogenerator property and thus establish a strong relation between convolution equations and their solution spaces. Input/output structures of gen. beh. exist and are used to prove that also many nonautonomous generalized behaviors are indeed behaviors. The E′-torsion elements of E, i.e., the smooth functions which satisfy at least one nonzero convolution equation, are called 'mean-periodic functions' and were studied by many outstanding analysts. Their results are significant for gen. beh. [ABSTRACT FROM AUTHOR]

Fuel cells are among the most promising technologies for clean power generation. Solid oxide fuel cells (SOFC) are characterized by high efficiency, fuel flexibility and a wide range of operating conditions. SOFC are the preferred fuel cell technology for micro-combined heat and power (micro-CHP) units, but they are prone to rapid performance degradation when exposed to thermal and electrical cycling. To overcome this issue, alternative methods are sought to assure high durability and long-lasting operation by mitigating the cycling. This can be achieved by limiting the number of cycles and maintaining stable operating conditions. One of the proposed solutions is to create a hybrid system combining an SOFC stack with a molten salt (NaNiCl) battery module. The NaNiCl battery is well known for its high energy density, high durability and zero electrochemical self-discharge. This hybrid system is a solution in which the fuel cell stack and the battery module are thermally and electrically integrated and operate as a part of a cogenerator. Since both modules operate at elevated temperature, heat generated in the stack can be partially used to maintain a sufficient operating temperature of the battery pack. The SOFC/battery hybrid enables high operational flexibility which is achieved by proper selection of the power ratios between the two components. In this configuration the battery pack can be used to stabilize operation of the fuel cell stack and to allow for load-following operation of the hybrid. To evaluate the operation of a SOFC/battery, the dynamic models of the battery and fuel cell stack were developed in Aspen Hysys 8.5. The simulator enables predictive modeling of various operating conditions corresponding to the different power demand profiles. In the transitional states of the telecommunication system, the hybrid unit can either charge or discharge the battery without cycling the fuel cell stack. Simulations are needed to evaluate the performance of the SOFC/battery hybrid system, in particular to analyze the capability to follow the load profile during operation in island mode. [ABSTRACT FROM AUTHOR]

Domains of generalized probability have been introduced in order to provide a general construction of random events, observables and states. It is based on the notion of a cogenerator and the properties of product. We continue our previous study and show how some other quantum structures fit our categorical approach. We discuss how various epireflections implicitly used in the classical probability theory are related to the transition to fuzzy probability theory and describe the latter probability theory as a genuine categorical extension of the former. We show that the IF-probability can be studied via the fuzzy probability theory. We outline a 'tensor modification' of the fuzzy probability theory. [ABSTRACT FROM AUTHOR]

A simplified model of a polymer electrolyte membrane (PEM) fuel cell has been suggested for simulating packaged commercial fuel cell systems. PEM fuel cell systems are used in building cogeneration applications because of their high efficiency, low transmission loss and pollution, flexible scalability, and low noise. In conventional cogeneration applications, optimization techniques are utilized to size a system and determine proper operational strategies using simulations. To evaluate the performance of a building cogeneration system, a fuel cell model should be concise but accurate to allow its implementation in a whole-building simulation program. Some existing models are appropriate for building applications, but they have some limitations in modeling when a commercial packaged fuel cell system is used. To overcome these problems, a simplified fuel cell model is suggested for commercial packaged fuel cells by adding some new variables and validating through experimental and published data. This model is relatively simple compared to other models but can be easily utilized in some limited cases with performance predictions. [ABSTRACT FROM AUTHOR]

Let C and R he unital rings, and 7, un injective cogenerator for right C-modules. For an R, C-himodule U, let U* = Homc(U, Z), R' = EndR(U) and BiendR(U) = EndR',(U), the hiendomorphism ring of U. Under suitable requirements on U we show that B := BiendR(U) can he identified with a suhring of B := BiendR(U*), and study conditions for the reverse inclusion and density of B in B. In the case C is contained in the center of R we describe BiendR(R*) in terms of the Arens products in R** and study Arens regularity of R in the context of duality of modules. We characterize Arens regular algebras over fields. [ABSTRACT FROM AUTHOR]

For a triangulated category with products we prove a formal criterion in order to satisfy Brown representability for covariant functors. We apply this criterion for showing that both homotopy category of projective modules and homotopy category of projective complexes satisfy this kind of representability. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental investigations of the ORC system equipped with the expansion valve simulating microturbine operation. The aim of the research was to verify the correct functioning of the installation components and to access the technical condition of the thermal insulation in the heating and cooling mode with regard to the design assumptions. The research was conducted for different values of medium flow rates. The images were acquired using the thermal imaging camera FLIR E50, which is equipped with a specialized software. On the basis of the experimental results, the heat losses have been estimated, together with the places which were the major source of loss (the so-called thermal bridges). It was shown experimentally that the application of a thermal imaging camera can constitute a simple and fast thermal diagnostics method for installations of this type. [ABSTRACT FROM AUTHOR]

Singular curves, which are projections of singular extremals, play a special role in control theory and the theory of distributions. In this paper, we show that singular velocities, tangent to singular curves, determine affine distributions that are simultaneously of an even-rank and co-rank 2. If D is such a distribution, then its singular velocities span a distribution C (of a rank two times smaller than that of D) that, together with its Lie square, forms the initial distribution, i.e., $D={C^{D}}+\left [{C^{D}},{C^{D}}\right ]$. We also provide canonical constructions of vector fields that are C generators, canonical differential forms that are D cogenerators, and some functional invariants related to distribution of the considered type. [ABSTRACT FROM AUTHOR]

Heating by gas combustion, by use of different types of systems and plants, is widespread in residential and industrial environments. One example is the gas stove, the heat-radiating unit of which operates autonomously with a local gas feed and, possibly, electricity for an optional fan convector. A thermoelectric generator (TEG) can be integrated within this type of autonomous gas heater for local production of electric power, to support electrical auxiliaries, where desired, without the need for any connection to the electricity grid. This approach can lead to easier installation and operation and increases overall efficiency. A new prototype of an autonomous gas heater has been implemented by integration of a TEG device of simple and robust design, easily operated by the end user. A small amount of heat is withdrawn and converted into electricity by the TEG. This enables self-sustaining operation and, moreover, powers new ancillary functions (e.g. fan convector) without extra electrical requirements and no need for an electrical connection. [ABSTRACT FROM AUTHOR]

In this paper, we give a relationship between projective generators (resp., injective cogenerators) in the category of R-modules and the counterparts in the category of complexes of R-modules. As a consequence, we get that complexes of W-Gorenstein modules are actually [InlineMediaObject not available: see fulltext.]-Gorenstein complexes whenever W is a subcategory of R-modules satisfying W ⊥ W, where [InlineMediaObject not available: see fulltext.] is the subcategory of exact complexes with all cycles in W. We also study when all cycles of a [InlineMediaObject not available: see fulltext.]-Gorenstein complexes are W-Gorenstein modules. [ABSTRACT FROM AUTHOR]

Let MR be a non-zero module and F : σ[MR]xσ;[MR] → Mod-ℤ a bifunctor. The F-reversibility of M is defined by F(X; Y) = 0 ⇒ F(Y;X) = 0 for all non-zero X; Y in σ[MR]. Hom (resp. Rej)- reversibility of M is characterized in different ways. Among other things, it is shown that RR (RR) is Hom-reversible if and only if R =Ⅹni=1 Ri such that each Ri is a perfect ring with a unique simple module (up to isomorphism). In particular, for a duo ring, the concepts of perfectness and Hom-reversibility coincide. [ABSTRACT FROM AUTHOR]

Highlights: [•] A SOFC based cogeneration/trigeneration system is proposed for Hotels in Hong Kong. [•] A payback period analysis is performed for the proposed system. [•] With government subsidy at 50% of the total cost, the payback is within 5 years. [•] Reduction in SOFC cost and government support are the key economic factors. [Copyright &y& Elsevier]