Power Cogeneration System Research Articles

Thermoeconomic assessment of a heat pump-enhanced steam and power cogeneration system under design and off-design conditions based on energy level-based exergy cost allocation method

Thermoeconomic analysis is considered a strong tool for cogeneration systems to optimize operation and set prices. In this paper, an absorption-compression heat pump enhanced steam and power cogeneration system is proposed, in which a heat pump is used to upgrade low-temperature waste heat and generate steam. The thermoeconomic performance of the proposed system is investigated under design and off-design conditions using a new thermoeconomic analysis approach with energy level-based cost allocation. As a result, the unit exergy costs of electricity and steam under the design conditions are 2.249 kW/kW and 1.714 kW/kW, respectively. The cost of electricity is higher than that of steam, and this result is opposite to that obtained by a conventional thermoeconomic method (2.063 kW/kW and 2.339 kW/kW, respectively). The costs of electricity and steam increase along with the decreasing engine load under off-design conditions, and the cost of electricity is always higher than that of steam. Finally, the thermoeconomic analysis method with energy level-based cost allocation can obtain more reasonable results and is more suitable for cogeneration systems.

Technical and Economic Assessment of Micro-Cogeneration Systems for Residential Applications

The benefits of cogeneration or combined heat and power (CHP) of large power systems are well proven. The technical and economic viability of micro-cogeneration systems is discussed in this paper as it compares to the separate production of electricity and heat. A case study for an individual household is also provided to better understand the benefits of small power cogeneration from renewable energy sources. Two micro-CHP systems are considered for analysis: the first with Stirling engine, and the second with Rankine Organic Cycle. The reference scenario is an individual household with a gas boiler and electricity from the public network. The results show that it is possible that the payback period for the micro-CHP from renewable energy sources will fall below the accepted average value (<15 years) without the support schemes. The economic and environmental benefits of small power cogeneration systems compared to the traditional scenario are highlighted.

Coordinated Control for Combined Heat and Power Load of an Integrated Energy System

Most stand-alone integrated energy systems (IES) with renewable energy can only meet the demand of electrical load, not both electrical load and thermal load. Those studies on combined heat and power cogeneration systems mainly focus on the optimal scheduling of each source, ignoring the difference in dynamic response between electrical and thermal processes. In fact, the different response speeds of electrical and thermal objects will bring in challenges to control. In order to specify and solve the issue, this paper proposes a detailed mechanism model of a standard IES. A model predictive control (MPC) controller is designed and tuned based on the state-space form of the system. The control simulation results imply the feasibility of the MPC controller in coordinating both electricity and heat.

Thermodynamic and exergic modelling of a combined cooling, heating and power system based on solid oxide fuel cell

In this research, thermodynamic and exergic analyses have been carried out on a combined cooling, heating and power cogeneration system that includes a solid oxide fuel cell and a single-effect lithium bromide absorption chiller. Results indicate that by increasing the system inlet air flow rate, the overall efficiency of the hybrid system is reduced, due to the reduction of the cell’s working temperature and exhaust gases temperature; while an increase in the working pressure of the system has no effect on its efficiency. The results also show that by raising the temperature of exhaust gases, the rate of exergy destruction diminishes, while the rate of exergy loss in the hybrid system increases. In the absorption chiller cycle, the maximum exergy destruction rate occurs in the generator, and the minimum rate is achieved in the pressure-reducing valve, between the evaporator and the condenser. Also, in the fuel cell cycle, the highest exergy destruction rate occurs in the heat exchanger of the inlet air to the cell, and the lowest exergy destruction rate occurs in the two water pumps. Moreover, the entropy generation rate and the exergy destruction rate of the fuel cell cycle are higher than those of the chiller cycle.

Application of biogas to supply the high compression ratio engine

The study concerns the use of biogas as a fuel for supplying a modified self-ignition engine. As a result of the modifications made, the compression ratio was reduced and the engine was equipped with an ignition system and an electronically activated engine throttle. The changes have made it possible to burn biogas in a high compression ratio engine. The paper presents the results of research conducted on a low power cogeneration system with engine that drives an electrical machine cooperating with a 380/400 V network. The analysis includes, among other things, the possibility of producing electricity using biogas. The paper presents the influence of regulatory parameters such as the volume and composition of the supplied gas mixture and the degree of throttle opening on the obtained engine operation indicators and the driven electric machine. The tests were carried out in relation to the obtained ecological indicators depending on the concentration in the exhaust of such substances as: HC, CO, NOx.

Working domains of a hybrid absorption-compression heat pump for industrial applications

Absorption-compression heat pumps are especially suitable for high-temperature heat production, however, its performance at different conditions are highly influenced by the choice of ammonia-rich solution mass fraction and circulation ratio. This paper revealed the working domains of a hybrid absorption-compression heat pump for high-temperature (>130 °C) saturated steam production and obtained its optimized thermodynamic performance at different conditions. For saturated steam production, a supplied heat temperature up to 160 °C can be obtained using commercially available components with a thermal benefit compared to a gas boiler. For hot water or air production, the supplied temperature can be even higher. Moreover, a new heat coefficient of performance is proposed to evaluate the heat pump systems with both heat and power consumption. There are optimal heat coefficient of performance values for the circulation ratio and ammonia-rich solution mass fraction for the hybrid system. The results indicated that setting the ammonia-rich solution mass fraction less than 0.6 and the circulation ratio more than 0.7 is a better choice for the hybrid system in actual application. Finally, the hybrid heat pump system was used to improve the thermal performance of a saturated steam and power cogeneration system driven by an internal combustion engine. This work provides a useful guidance for the hybrid absorption-compression heat pump in actual application.

A novel solar assisted vacuum thermionic generator-absorption refrigerator cogeneration system producing electricity and cooling

A novel solar assisted cogeneration system composed of a parabolic dish collector (PDC), a vacuum thermionic generator (VTIG), and an absorption refrigerator (APR) is proposed, in which the APR harvests the rejected heat from the VTIG for further cooling production. The equivalent power output and efficiency of the proposed system are obtained by considering various irreversible losses including radiation and convection heat losses of the PDC, radiation heat losses between the cathode and anode of the VTIG, heat transfer irreversibility, irreversible effects inside the working fluid of the APR. The maximum attainable efficiency increases from 17.21% to 27.06% as the bottoming APR is hybridized into the system. Meanwhile, the corresponding power density gains a 13.47% increase. Comprehensive sensitivity analyses are conducted to examine the dependence of the proposed system performance on some decisive design parameters and operating conditions such as absorber temperature of the solar collector, solar concentration ratio, solar irradiance, work function and anodic temperature of the VTIG, heat transfer area, heat transfer coefficient, and internal irreversibility factor of APR. The obtained results may provide some new insights into development and operation of such a solar powered cogeneration system.

Life-cycle assessment of SNG and power generation: The role of implement of chemical looping combustion for carbon capture

Chemical looping combustion (CLC) is seen as a highly promising technology supporting the transition towards low-carbon societies. In this paper, a systematic assessment of the coal-based SNG (synthetic natural gas) and power cogeneration system with CLC was presented to justify the environmental unsustainability of such process. The results shows that lifetime of the oxygen carrier (OC) is the key element to determine the sustainability of decarbonized polygeneration system and the benefits from integrating CLC are significantly highlighted unless the lifetime exceeds 3000 h since the global warming impact (GWI) is almost independent. Besides, higher environmental disadvantages by using Cu-based OC (i.e. lowest energy output and highest global warming potential (GWP) by manufacturing copper oxides) as against Fe-based and Ni-based cases at the similar operating conditions. And similar environmental impacts by comparing with traditional cogeneration system that achieves a GWI of 45.03 kg/MW h increment, In addition, the effects of key parameters (e.g. steam to carbon ratio (O/C), recycling unreacted gas (Ru), etc.) on system performance and the carbon emissions allocation of products in terms of this polygeneration system have been discussed in detail.

A cold and power cogeneration system utilizing LNG cryogenic energy and low-temperature waste heat

Abstract A novel cold and power cogeneration system is proposed in this paper. In the system, a “special” absorption refrigeration cycle is designed which is driven by liquefied natural gas (LNG) cryogenic energy with ammonia-water as working fluid. And this system contains two power processes, in which ammonia and natural gas are heated respectively by low-temperature heat source and then expanse in turbines. The thermodynamic performance of the cogeneration system is simulated and analyzed. The results show that the new cogeneration system demonstrations good thermal performance. The exergy efficiency of the system is as high as 36.1%. The coefficient of performance (COP) of the refrigeration cycle is 1.6 and the generating efficiency of power cycle reaches 38.8%. Sensitive analyses are performed to evaluate the effects of key parameters on the performance of the cogeneration system. Some values of the key parameters are recommended and the variations of the main thermodynamic characters are outlined. This new cogeneration system provides a new approach for the efficient utilization of LNG cold energy.

Robust Scheduling Optimization Model for Multi-Energy Interdependent System Based on Energy Storage Technology and Ground-Source Heat Pump

The energy consumed by buildings makes up a significant part of total social energy consumption. The energy use rate of the traditional cooling and heating unit is low. A distributed cooling, heating, and power (CHP) system can achieve cascade use of energy and reduce the long-distance transportation of energy. Along with the wide use of ground-source heat pumps and energy storage technology, the combined cooling, heating, and power (CCHP) system coupled with a ground-source heat pump and energy storage technology is increasingly being used. Firstly, we proposed the construction of a CCHP system driven by distributed energy resources (DERs) including three subsystems of an electricity subsystem, a CCHP subsystem and an auxiliary heating subsystem as the object of study in this paper. Besides, with the goals of reducing carbon emissions, increasing energy efficiency, and minimizing system cost, a constraint mechanism based on the DOM-PSO (dynamic object method/particle swarm optimization) algorithm was applied. Finally, taking Tianjin Eco-City as an example, we used the PSO algorithm to analyze the operating characteristics of the cold and power cogeneration system under the uncertainty of the wind power output. The simulation results show that the joint optimization mode operation strategy can balance the results of different optimization modes by increasing the robust coefficient of wind power. Of all scenarios examined, the CCHP system coupled with the ground-source heat pump and energy storage technology performed best.

Research on Prevention and mitigation of Deep Mine Hazards in Ningzheng Mining Area

Ningzheng Mining Area, as one of the key mining areas of Longdong Energy Base in Gansu Province, whose average overburden depth of coal seams is more than 800 meters and average thickness of coal seams ranges from 8m to 14m. This paper analyzed the typical characteristics of water damage, heat damage, high mine pressure and gas disaster in Ningzheng mining area. Disaster prevention measures and two resource utilization prevention technologies (namely EMS cooling technology, Gas power generation and cogeneration system cooling technology) were put forward, the rearch has a realistic significance for the safety exploitation, comprehensive utilization of deep coal resources in China, energy conservation and emission reduction and development of circular economy.

Optimal design of cogeneration systems in total site using exergy approach

By increasingly demands on the hot and cold utilities in chemical processing industries, application of unified utility systems has extended in recent decades. Through the Total Site, accessibility to hot steam and condensing water has become more convenience. Therefore, cogeneration systems generate key product of total site, power to electricity network as well as steam to heating purposes. Also, it can be considered to consume the cold utilities to cooling destinations. In present work, defining the multiple arrangements of back pressure steam turbines, an optimal design of heat and power cogeneration systems through exergy point of view is determined. The excellent exergy efficiency and also the least amount of exergy destruction was measured to select the optimum system of arrangements. In times of need for extra power, either a condensing turbine or gas turbine system, were meant to generate deficiency of electricity in network. Then, both the extra scenarios were studied by exergy analysis. Consequently, final optimum system of cogeneration system in total site was selected. This ultimate optimal configuration is consisting the optimal steam turbines as well as the appropriate augmented scenario from exergetic viewpoint, between condensing or gas turbine systems. In addition, two case studies of utility systems were employed to confirm the applicability of proposed methodology.

The compatibility of controlled power plants with self-sustainable models using a hybrid input/output and water-energy-carbon nexus analysis for climate change adaptation

In the present study, a novel model-based approach is detailed for optimal design and analysis of clean and economic production technologies regardless of temporal and local restrictions. Accordingly, a dual-layer mathematical model is developed in which techno-economic and life cycle analyses are integrated in the first layer using a novel self-sustainability flowchart and the nexus between the water, energy, and carbon sectors are investigated in the second layer using an input/output analysis. A water and energy intensive system consisting of non-renewable (NRES) and renewable energy subsystems (HRES), a reverse osmosis module and a fuel cycle, is studied using the approach and the results are validated and calibrated according to the relevant literature. Four scenarios including an NRES fueled by pulverized coal (I) and natural gas (II), a hybrid NRES and HRES application (III), and a power and freshwater cogeneration system (IV) are compared from both economic and environmental viewpoints. Finally, the applicability of the controlled NRES is investigated using economic, environmental, and combined environmental-economic cost of products (CEECP) and the sensitivity of the model responses with respect to the manipulating variable is studied. The results showed that CEECP was obtained to be 164.7, 134.1, 515.2, and 134.1 $/MWh in the scenarios I, II, III, and IV, respectively. Additionally, the operational water withdrawal could be decreased by 1.7–3.2% in favor of additional 0.03–0.05% of CO2-eq emissions by employing a controlled power plant.

Economic, exergy, and the environmental analysis of the use of internal combustion engines in parallel-to-network mode for office buildings

In recent times, the tendency toward the use of combined heat and power cogeneration systems to supply the electrical and heat requirements has provided the heat for the buildings in addition to the cost reduction of the power distribution networks. In this study, the Carrier Software per 15th of each month did the hourly analysis of heating, cooling, and electrical loads for a 5-floor office building with a net area of 1000 m2 (200 m2 per each floor) in Tehran City (in Iran) and besides the average loads in that month were assumed. The mechanical air-conditioning system with absorption chiller is used to supply the heating load in the second half of the year (the autumn and winter), the heat pump system and the cooling load in the first half of the year (spring and summer). Due to the average thermal, cryogenic, and electrical loads, the number of motors required for the parallel mode of the power distribution system was 4 and for the network-independent mode was 7. The results show that the annual productions of $$m_{{{\text{Co}}_{2} }} ,m_{\text{Co}} ,\;{\text{and}}\;m_{\text{No}}$$ are 648,640, 21,395, and 68,172 kg/year, respectively. The entropy production in cogeneration mode was 801,861.120 kJ/kg year. Besides, the prices of electricity in parallel-to-network and network-independent modes were calculated as 0.96 and 0.4866 US$/kWh, respectively.

Development of a PEMFC-based heat and power cogeneration system

ABSTRACTHydrogen-fed proton exchange membrane fuel cell (PEMFC) has to overcome high installation and operation cost before being adopted as a distributed power candidate. Cogeneration of power and heat is a good approach to increase hydrogen energy utilization rate. A PEMFC-based power and heat cogeneration system is proposed and established in the current study to investigate system’s technological and economical feasibility. This cogeneration of heat and power (CHP) system composes of a 2.5-kW fuel cell stack, hydrogen supply system, air supply system, water and heat management system, and heat recovery system. The control strategies to automate the system operation are realized by a programmable automation controller (PAC) system. Detailed measurement of the system is also constructed along with a web-based human–machine interface (HMI) platform to facilitate experiments and demonstration. Preliminary testing of the CHP system shows good performance of heat and power outputs. System’s electrical power conversion efficiency and thermal efficiency of the CHP system are measured at 38% and 35%, respectively. System combined efficiency therefore reached about 73%.

Intertemporal optimization of synthesis, design and operation of integrated energy systems of ships: General method and application on a system with Diesel main engines

The need to decrease fuel consumption and environmental pollution caused by ships leads to the development of complex and integrated systems that produce all forms of energy needed (mechanical, electrical and thermal) with as low fuel consumption as technically possible and economically feasible. A variety of configurations, design specifications and operating states can serve the loads. The question of which combination of those is the best under certain criteria is far from trivial, and relevant engineering decisions have to be supported by optimization procedures. As an aid for this purpose, a method has been developed and presented in this article.A superconfiguration of the system is considered and simulation models of the system and its components are developed. Instead of the three-or two-level approach followed by other methods for the solution of the triple optimization problem (synthesis-design-operation), a single-level approach is followed by the present method. As for the operation optimization, all the operating modes are optimized simultaneously. Due to the discontinuity and multimodality of the optimization problem, gradient-based methods are not particularly successful for the solution. Instead, a genetic algorithm is used. The applicability of the method is demonstrated with numerical examples, while its versatility, i.e. its adaptability to alternative conditions or values of parameters, is demonstrated by solving the problem with different sets of data, such as varying fuel price, capital cost and operation profile.Even though the application example is for a ship energy system, the method can also be applied for the optimization of land installations, such as power plants and cogeneration systems, with proper modification.

Multi-objective optimization and flexibility analysis of a cogeneration system using thermorisk and thermoeconomic analyses

In the present study, an optimal power and freshwater cogeneration system is proposed to meet the global requirements sustainably. A Rankine cycle (RC), an organic Rankine cycle (ORC) and a reverse osmosis (RO) module are integrated to form the proposed system. The performance of the system is investigated using thermo-mathematical models allocating seven organic fluids in the bottoming ORC. A novel evolutionary algorithm-based multi-objective optimization approach is applied using thermorisk and thermoeconomic analyses. Thus, an optimal configuration is determined at both global and local scales. Finally, a flexibility analysis is performed to the optimal configuration considering probable uncertainties in the market. The optimization results showed that the total accidental risk impact and the total product cost rate improved by 2.49–48.73% and 5.67–62.41%, respectively, depending on the employed organic fluid. The highest exergetic efficiency and the minimum specific power consumption were obtained as 52.74% and 4.111 kWh/m3, allocating R245fa in the optimal system. The system enjoying R123 had the widest flexibility range without any increases in the optimum total product costs.

Steam explosion pretreatment improved the biomethanization of coffee husks

This study evaluated the potential of energy generation using a combined heat and power co-generation system (CHP) from biogas produced during the anaerobic digestion of coffee husks (CH) pretreated with steam explosion. Pretreatment conditions assessed were time (1, 5, 15 and 60min) and temperature (120, 180 and 210°C). Polysaccharides solubilisation and biogas production were not correlated. While pretreatment with severities higher than 4 resulted in a highest solubilisation of cellulose, hemicelluloses and lignin; however, furans concentration in those cases hindered biomass biodegradation. Considering a CHP, all pretreatment conditions were worthwhile when compared to non-pretreated CH. The best condition was 120°C for 60min, in which a 2.37 severity showed the highest methane yield (144.96NmLCH4gCOD−1) and electricity production (0.59kWhkgCH−1). However, even better results could be achieved using 120°C for only 5min, which would lead to a larger amount of CH daily processed.

Exergy based parametric analysis of a cooling and power co-generation system for the life support system of extravehicular spacesuits

Providing electric power and managing the thermal condition for the astronaut are two of the essential functions of the spacesuit life support system in a distance extravehicular activity. This paper proposed a new conceptual portable life support system which combines the cooling and power supply functions for the astronauts with the metal-hydride, fuel cell and absorption chiller. The cooling and power balance models were developed on basis of the first-law of thermodynamics. The second-law based entropy generation, exergy destruction and exergetic efficiency models of the integrated life support system were established. A parametric study was performed to evaluate the effects of varying working conditions, including the hydride metal types, operating temperatures of the fuel cells, heat transfer effectiveness of the evaporator and the concentration of the working fluid pair used in the absorption chiller, on the exergy-based performance of the new life support system. Results indicate that the energetic efficiency and the exergetic efficiency of the integrated PLSS can up to 86.98% and 59.07% respectively.

Comparative Analysis Between District Heating and Geothermal Heat Pump System

In Seoul, most of the new private buildings were mandated renewable energy installations more than 12% of total energy use in 2015. There are solar power, solar heat, geothermal, sunlight collecting, fuel cell, and small cogeneration systems in applicable renewable energy. Accordingly, some reconstruction apartments want to apply geothermal heat pump systems as heating and cooling. This has resulted in reducing the demand for district heating since district heating had been supplied in these areas. From the point of view of district heating suppliers, new competitor such as heating by geothermal heat pump system seems to appear in district heating market. District heating system is considered preferentially to apply in heating area abroad due to its high efficiency. However, district heating isn't recognized properly as a renewable energy in domestic situation. Therefore, in this study, we analysed primary energy use and greenhouse gas reductions of district heating and geothermal heat pump system. As a result, primary energy use and greenhouse gas reduction of district heating system are bigger than them of geothermal heat pump system.