Engine Cogeneration Research Articles

Exergetic Analyses of Detonation Engine Cogeneration Plants

Efficiency improvements are very important in all research and technology. Detonation engines are high technology devices. In the last decades they attracted attention by many researchers. However, detonation engines for cogeneration are not researched efficiently. This article is about the detonation engines cogeneration cycles which analysed by using 1. and 2. law of thermodynamics and exergy analyses methods by the authors. The exergetic performance analyses, their advantage and disadvantages of the ZND-HRSG detonation engine cogeneration cycles were obtained. The exergetic performance analyses were done for various excess air rates to obtain the variations of the combustion exit pressures and temperatures, exergy efficiencies, electric heat rates, SFC and other parameters of their performance. Also, an optimization analysis was done for the ZND-HRSG by searching the optimum values for different excess air rates. The results showed that, the ZND-HRSG cycle have the optimum values of the performance at 1.6-1.8 of the excess air rates.

Methodology for Modernizing Local Gas-Fired District Heating Systems into a Central District Heating System Using Gas-Fired Cogeneration Engines—A Case Study

Sustainability can be achieved by improving process efficiency, among other methods. In the case of heat supply systems for cities, one of the ways to increase the efficiency of fuel use, and thus reduce resource consumption and greenhouse gas emissions, is the generation of heat and electricity in one process—the use of cogeneration (CHP). The main goal of this paper is to deliver the methodology for a step-by-step modernization process for local gas-fired heating plants through the use of gas cogeneration engines in common central district heating systems. The presented methodology was applied on the basis of a real system located in north-western Poland (case study from Białogard). The profitability of cogeneration was simulated against the background of changing gas prices. The financial and environmental profit from modernization was calculated. The technical requirements that had to be met in order to adapt the existing heating system to cooperation with the new energy source were also presented. The importance of selecting the supply and return temperature of water in the heating system after modernization was emphasized. Based on investment experience, we show that installing a cogeneration engine improves a company’s financial result by 33% (calculated as the difference between the revenue from the sale of energy and the cost of gas only) and is less harmful to the environment, among other benefits, significantly reducing CO2 emissions by 78%.

Techno-economic and environmental analyses of a solar-assisted Stirling engine cogeneration system for different dwelling types in the United Kingdom

In this study, a hybrid cogeneration system that combines photovoltaic-thermal (PV-T) collectors with a Stirling engine, and a battery-pack-based energy option is proposed for residential applications. The system’s purpose is to fulfil the electrical and heating requirements of different types of houses in the United Kingdom, including detached, semi-detached and mid-terraced houses. This study includes a comprehensive assessment of the techno-economic feasibility and environmental impact of the proposed integrated energy system, after determining the appropriate sizing of the system’s components for the three different house types. The exergy efficiency of the integrated system for detached houses (with a 1 kWe-Stirling engine plus 28 m2 of PV-T collector array) is found to be higher compared to that for the semi-detached and mid-terraced house configurations, with the highest efficiency of 22 %. In terms of economic performance, detached houses have the lowest levelized cost of electricity (0.622 £/kWh), levelized cost of heat (0.147 £/kWh), and levelized cost of total energy (0.205 £/kWh). Furthermore, the system demonstrates the maximum potential reduction in CO2 emissions in detached houses. The achieved CO2 emissions reduction rates for different house configurations fall within the range of 30 % to 45 %. The proposed hybrid cogeneration system shows promise as an effective and sustainable solution to meet the energy demands of various residential house types in the United Kingdom, offering improved efficiency, cost-effectiveness, and substantial reductions in carbon emissions for detached houses.

Integration of a conical frustum PCM system for enhanced thermal energy storage in a diesel engine cogeneration system

An effective heat storage system was achieved by fabricating a 400-L cylindrical thermal energy storage (TES) tank equipped with 9 conical frustum containers. These conical frustum containers with PCM (CFC-PCM) contain paraffin wax in the upper third of the tank and water as the heat transfer fluid (HTF) in the circulation process. The TES tank was integrated with a 40 kW diesel generator, and experiments were conducted by operating the engine at six different loads. During the charging process, heat was recovered from the engine exhaust gases and jacket cooling water. The performance parameters were evaluated and reported based on the transient behavior of a hybrid sensible/latent TES tank under the charging process. The results showed that at 72.55% of the engine peak load, the energy utilization factor (EUF) and the exergy efficiency of the system were 91.17% and 81.22%, respectively. Although adding PCM to water only resulted in a 3% enhancement in heat storage capacity, it improved the durability of heat charging by providing thermal stratification and increasing charging efficiency compared to the reference state in some of the studied cases.

Compact automatic controlled internal combustion engine cogeneration system based on natural gas with waste heat recovery from the combustion process

Compact automatic controlled internal combustion engine cogeneration system based on natural gas with waste heat recovery from the combustion process

The impact of cogeneration plant and a storage tank in a district heating system

The goal of the study is to investigate the thermal behavior and the benefits of a cogeneration system based on two gas fired engines and of a thermal storage tank in a biomass based district heating system situated in Romania. The investigation is based on an hourly analytical model of all the district heating components: biomass boiler, natural gas cogeneration engines, storage tank and consumers. The climatic data of the location are used as input in the model. The gas cogeneration engines coupled with the heat storage tank increase the flexibility of the system and allow the production of electricity even in periods with little or no heat demand. The analytical modelling of the storage tank considering the water stratification allows the correct sizing of the storage tank, in the planning stage of the project. The total yearly heat production is divided between 81.54 % produced by the proposed cogeneration plant and 18.46 % produced by the existing biomass boiler.

Establishing the energy content of natural gas residential consumption : example with Belgian field-test applications

In the context of the much-needed energy transition, monitoring of residential energy appliances is more and more common in order to evaluate (and improve) their field-test performance in real applications. Many residential heating appliances use natural gas as energy source : residential gas boilers, gas engine heat pumps, gas absorption heat pumps; fuel cell-based cogeneration units, internal combustion engine cogeneration units, etc. Unfortunately, for simplicity and costs reasons, only the volume of the consumed natural is measured at the inlet of the monitored residential heating appliance. This volume, and the equivalent energy level that it contains and that is required for efficiency calculations, is affected by the atmospheric pressure and the temperature at the field-test site, as well as by the always varying natural gas composition. This paper demonstrates the method that has been used in Belgian field-test studies conducted on residential heating appliances to establish the energy content of the consumed natural gas.

Desiccant wheel air-conditioning system driven by gas engine cogeneration of heat and power: simulation and analysis by Dymola

Based on the combination of gas engine cogeneration of heat and power (GECHP) technology and temperature and humidity independent control air-conditioning technology, an air-conditioning system combined with desiccant wheel driven by GECHP was proposed to decrease cooling energy consumption and utilize the waste heat of gas engine. In this study, Dymola software was adopted to model the hybrid system and conduct hourly simulation throughout the cooling and heating season for two types of large public buildings: the supermarket building and the office building. Results show that the hybrid system applied to target buildings can meet the requirements of each index of air-conditioning energy supply. Comparing two types of application scenarios, the system primary energy conversion ratio of the supermarket building reaches 112%, 19% higher than that of the office building. And the system CO2 emission reduction rate per unit of capacity of the supermarket building is 0.18 kg/kWh, lower than the 0.22 kg/kWh of the office building. Therefore, the hybrid system has superior energy-saving and environmental performance and is especially suitable for high-temperature and high-humidity areas in summer as well as building application scenarios with high indoor moisture gain and fresh air demand.

Performance analyses of detonation engine cogeneration cycles

AbstractAircraft engines such as gas turbines and detonation engines have very important attention by the researchers in the last decades. However, using detonation engines for producing electrical and heat power was not researched efficiently. In this study, gas turbine and pulse detonation engines cogeneration systems were analyzed and compared by using first and second laws of thermodynamics and exergy analysis method. Three different cycles, namely, basic gas turbine, Zeldovich–von Neumann–Döring (ZND) detonation engine and steam injected regenerative ZND detonation engine cogeneration systems were investigated. The performance analyses and the advantage of these three cycles were obtained and discussed. The performance analyses were done for different compression ratios (r), and the combustion outlet temperatures and pressures, exergy efficiencies, specific fuel consumption, electrical efficiency, exergy fuel consumption, electrical heat rates and other performance parameters of the three cycles were obtained and discussed. It is found that gas turbine cogeneration systems have some advantages and disadvantages in some conditions than ZND cycle. The steam injected regenerative ZND detonation engine cogeneration systems can compete with the Brayton cycle cogeneration systems.

Cogeneration potential of an operating diesel engine power plant

Waste heat recovery systems convert the thermal energy in waste fluid streams into useful work. Diesel engine cogeneration systems are waste recovery systems using technologies and devices with main elements being the diesel engine prime movers, the electric generator, Rankine cycle steam turbine, exhaust heat recovery boiler super heaters, and control and instrumentation devices. Diesel engines exhaust significant recoverable heat energy that can be converted to extra electricity using a Rankine cycle plant. In this study, the cogeneration potential of an operating diesel engine power plant was established. The cogeneration potential of a 119.7 MW operating power plant in Kenya is established. The study showed that subject to limits imposed by presence of sulphur in fuel and hence existence of sulphur dioxide in the exhaust, each engine of capacity 17.1 MWe has recoverable thermal energy of about 1.33 MWth while the whole plant with seven engines is about 9.3 MWth for the 7 engines at plant optimum loading conditions which can generate 8.5 MWe extra electricity under optimum conditions. The study recommends the development of up to 9 MWe Rankine cycle steam turbine-based cogeneration power plant. Diesel power plant cogeneration is a technically and economically viable strategy to increase the generation efficiency of diesel power plants and reduce the pollution intensity and financial performance of the diesel power plant leading to reduction in cost of power and higher return on investment for investors.

Evaluation of the use of cogeneration bonus as a support mechanism for the transformation of the heating system in Poland in 2019-2020

The development of cogeneration is an element of the transformation of the Polish heating sector. Consequently, the state applies various subsidy mechanisms. One of them is the cogeneration bonus, which is designed to stimulate investment in high-efficiency cogeneration. It consists in subsidizing the generated electricity to entities that won the cogeneration bonus auction and then made investments in new cogeneration engines. The purpose of this paper is to evaluate the use of the cogeneration bonus. The thesis assumes that the cogeneration bonus, despite its supportive nature, is not used by investors. This is evidenced by the low level of contracting of subsidies available in individual auctions. To achieve the objective of the study, the ratio of the volume of contracted subsidies in the cogeneration bonus auctions to the volume available for contracting in individual auctions was analyzed. The author has analyzed: the results of the auction for cogeneration bonus, sector reports, CO2 emission price, types of fuel as well as aggregated financial data of Polish heat plants. The research has an implication character, confirming lack of adequacy of cogeneration bonus to financial situation of potential investors.

Thermoeconomic Analysis in Advanced Cogeneration Systems in Buildings

In this work thermoeconomics is applied to a central thermal system covering three buildings that consists of a cogeneration engine, an aerothermal heat pump and a natural gas condensing boiler. Cogeneration systems integrated with renewable energy technologies are very attractive solutions in the building sector. Nevertheless, the use of cogeneration systems together with active envelope solutions, such as the one encountered in this work, are scarce and the efforts to enhance the synergies between both systems are even scarcer. A heat pump is connected to a so-called solar wall to provide hot air and a renewable photovoltaic system supplies the electricity consumed by the heat pump. Thermoeconomics is applied to evaluate the cost of flows based on its energy-quality. Hence, this innovative and complex system can be analysed and diagnosed by this methodology. As a result, thermoeconomics is presented as an effective tool for the detailed study of the energy cost distribution and the key to enhancing energy efficiency.

A Potential Analysis on Regional Demand Response by Air-conditioning Systems Combined with Gas Engine Cogeneration

A Potential Analysis on Regional Demand Response by Air-conditioning Systems Combined with Gas Engine Cogeneration

Assessing Local Power Generation Potentials of Photovoltaics, Engine Cogeneration, and Heat Pumps: The Case of a Major Swiss City

In this paper, we investigate the potentials of distributed generation (DG) in a medium-sized Swiss city. We show the role of private households in the sustainable energy transition process induced by Swiss energy policy. For the analysis, we define six scenarios that enable us to study the potentials and impacts of different combinations of DG technologies in terms of costs, CO2 emissions, and amounts and shares of DG provided by non-industrial end-users (essentially private households and the services sector). Three variants are investigated, one with real electricity costs and CO2 emissions, one with increased electricity costs (e.g., construction of new power plants), and one with increased CO2 emissions (e.g., due to the planned nuclear phase-out in Switzerland). We find that non-industrial entities can play an important role as prosumers. They mitigate the need for centralized generation. Within a scenario where the non-industrial energy end-users install water-water heat pumps and photovoltaics, a total reduction of the gas procurement from the grid is possible whereas the electricity demand from the grid increases by 24%. This scenario reveals higher DG electricity costs in comparison to conventional electricity supply, but the total costs of energy supply decrease due to the elimination of gas supply, and the CO2 emissions can be reduced by 68%.

Hydrogen Addition to Natural Gas in Cogeneration Engines: Optimization of Performances Through Numerical Modeling

A numerical study of the energy conversion process occurring in a lean-charge cogenerative engine, designed to be powered by natural gas, is here conducted to analyze its performances when fueled with mixtures of natural gas and several percentages of hydrogen. The suitability of these blends to ensure engine operations is proven through a zero–one-dimensional engine schematization, where an original combustion model is employed to account for the different laminar propagation speeds deriving from the hydrogen addition. Guidelines for engine recalibration are traced thanks to the achieved numerical results. Increasing hydrogen fractions in the blend speeds up the combustion propagation, achieving the highest brake power when a 20% of hydrogen fraction is considered. Further increase of this last would reduce the volumetric efficiency by virtue of the lower mixture density. The formation of the NOx pollutants also grows exponentially with the hydrogen fraction. Oppositely, the efficiency related to the exploitation of the exhaust gases’ enthalpy reduces with the hydrogen fraction as shorter combustion durations lead to lower temperatures at the exhaust. If the operative conditions are shifted towards leaner air-to-fuel ratios, the in-cylinder flame propagation speed decreases because of the lower amount of fuel trapped in the mixture, reducing the conversion efficiencies and the emitted nitrogen oxides at the exhaust. The link between brake power and spark timing is also highlighted: a maximum is reached at an ignition timing of 21° before top dead center for hydrogen fractions between 10 and 20%. However, the exhaust gases’ temperature also diminishes for retarded spark timings. Lastly, an optimization algorithm is implemented to individuate the optimal condition in which the engine is characterized by the highest power production with the minimum fuel consumption and related environmental impact. As a main result, hydrogen addition up to 15% in volume to natural gas in real cogeneration systems is proven as a viable route only if engine operations are shifted towards leaner air-to-fuel ratios, to avoid rapid pressure rise and excessive production of pollutant emissions.

Performance Analysis of Hybrid Desiccant Cooling System with Enhanced Dehumidification Capability Using TRNSYS

In a field test of a hybrid desiccant cooling system (HDCS) linked to a gas engine cogeneration system (the latter system is hereafter referred to as the combined heat and power (CHP) system), in the cooling operation mode, the exhaust heat remained and the latent heat removal was insufficient. In this study, the performance of an HDCS was simulated at a humidity ratio of 10 g/kg in conditioned spaces and for an increasing dehumidification capacity of the desiccant rotor. Simulation models of the HDCS linked to the CHP system were based on a transient system simulation tool (TRNSYS). Furthermore, TRNBuild (the TRNSYS Building Model) was used to simulate the three-dimensional structure of cooling spaces and solar lighting conditions. According to the simulation results, when the desiccant capacity increased, the thermal comfort conditions in all three conditioned spaces were sufficiently good. The higher the ambient temperature, the higher the evaporative cooling performance was. The variation in the regeneration heat with the outdoor conditions was the most dominant factor that determined the coefficient of performance (COP). Therefore, the COP was higher under high temperature and dry conditions, resulting in less regeneration heat being required. According to the prediction results, when the dehumidification capacity is sufficiently increased for using more exhaust heat, the overall efficiency of the CHP can be increased while ensuring suitable thermal comfort conditions in the cooling space.

Technical Feasibility Analysis of a Negative Emissions Beccs System for a Livestock Waste Treatment Plant

The share of global greenhouse gas emissions from tertiary sector has increased during the last years and it has finally become a target sector to implement carbon capture and storage technologies. This study analyzes the potential application of a carbon capture system within a livestock waste treatment plant (LWTP). The main target is the technical assessment of the integration possibilities between the post-combustion carbon capture process and a real LWTP which deals with pig manure and corpse cattle. Currently, these wastes are processed to produce energy and their exploitation is regulated by Regulation (CE) no 1069/2009. The currently existing facility is able to cover energy demands (thermal and electric) through a cogeneration engine and a boiler to generate the steam required to sterilize the cattle corpses. The proposed BECCS system must fulfil the requirement of energy demands of the LWTP and be able to generate extra electricity. The carbon capture system is sized to enhance the use of the biogas produced in the LWTP and the design and operation parameters are established to ensure a high capture efficiency and the technical feasibility of the facility. Additionally, a Rankine cycle fed by waste heat from the capture process is sized and implemented to produce electricity and steam to livestock waste treatment process. Different heat integration possibilities are analyzed in the final configuration to increase the steam flow in the Rankine cycle, the self-coverage of thermal demand in the LWTP and the coverage of thermal requirement of the capture process. Lastly, the avoided CO2 emissions are calculated with respect to the current LWTP configuration.

Energetic Investigation and Economic Feasibility for a University Campus in Romania towards Becoming an Energy Supplier

This research investigates and evaluates the University Politehnica of Bucharest (UPB) possibilities to become an energy self-supplying by building up its own power plant and becoming an energy distributor. The campus has already been connected to the national natural gas supplying pipe and the local district heating and electrical network.A set of criteria was used to evaluate the feasibility of this project. Technical, financial, and environmental considerations were taken into account to determine the most suitable solution. The feasibility study assumed three proposals of an energy supply system considered for the university buildings / campus. Gas-fired heating plant, gas-fired Internal Combustion Engine cogeneration plant and gas fired Internal Combustion Engine for cogeneration with an Organic Rankine Cycle ORC.The details of each proposal were discussed to obtain the optimum solution. Elaborate. It was found from a financial and environmental perspective that the most feasible project is gas-fired Internal Combustion Engine cogeneration, considering profit revenue from selling / exporting power to the domestic electricity grid. And the Net Present Value was around one million euros for 15 years life.

Modeling, multi-objective optimization and comparison of fire and water tube heat recovery steam generators for gas engine cogeneration plants

An innovative modeling and optimizing of fire and water tube heat recovery steam generators (HRSG) for gas engine cogeneration plant are performed here. In modeling section, the equations of ɛ-NTU, LMTD and heat transfer coefficients for one-phase flow and two-phase flow are organized to form a nonlinear system of equations. Furthermore, in the next step, two pairs of objective functions (annual expenses—exergy destruction rate and annual expenses—thermal effectiveness) are selected for multi-objective optimization of HRSG by the use of genetic algorithm for one, two and three MW gas engine cogeneration plants. Results for a 2 MW gas engine (as an example) show that the fire tube HRSG total expenses are 50% lower than that for water tube HRSG. In this situation, for water and fire tube boilers, the effectiveness and cost are 0.9, 40,000 ($/year) and 0.9, 20,000 ($/year), respectively. Furthermore, the exergy destruction rates are close and equal to 1373.45 kW and 1366.2 kW for water tube and fire tube boilers, respectively. Moreover, for each gas engine, six equations with thirty constant coefficients are obtained to explain the behavior of HRSG outlet exhaust gas temperature, pinch temperature difference, steam generation mass flow rate, working pressure, thermal effectiveness and exergy destruction rate at partial load.

Possibilities of the power optimization in the Stirling cogeneration engine fuelled by the natural gas

As the energy efficiency is at the heart of the integrated European Union energy policy, which aims to protect the environment through various research projects, the application of the Stirling engine for diffused electricity generation is one of the possible paths for low-carbon application. That is today particularly topical, just looking at the major interest paid at European level at the energy communities, also in terms of incentives and policies facilitating and supporting such initiatives. Although the tested engine V-160 runs on natural gas, its emissions can be neglected in comparison with the internal combustion engines, due to the much more favourable external combustion under the lower pressures and temperatures, as well as to the working medium, which is helium. Next step, becoming every day more and more relevant, will be using hydrogen as a clean (and green) fuel. A major advantage of the proposed engine for use in power generation is the constant speed under different loads. According to the thorough parametric analysis after 200 hours of operation of the engine at the University of Rome La Sapienza, new evidence of the possibilities of performance improvement was obtained. Compared to the Stirling engine with low temperature difference, it has a much lower Schmidt factor of about 21%, which means that a real thermodynamic efficiency of the cycle could be improved. The scope of the analysis was to determine the power that is changed due to the mass of helium and the power that is changed due to the temperature difference. Based on the experimental data, it is found that the temperature difference and the mass of the working medium have a reciprocal relationship. In such a working condition, the engine power is simultaneously increased due to the greater mass of helium, but at the same time decreased due to the decrease in the temperature difference, which is not valid for other types of Stirling engines. The resulting power can be optimized according to a new expression, presented in the paper.