CHP System Research Articles

Numerical study of [formula omitted]-fuelled micro-free piston CHP system, coupled with thermophotovoltaic (TPV) and battolyser units

Hydrogen (H2) fuelled internal combustion engines (ICEs) can play an important role in small-scale applications despite low efficiency, short reactant residence time and pre-combustion issues. In this study, a hybrid green H2 production and utilisation system covering renewable-powered H2O electrolysis, micro-CHP (combined heat and power) and thermoelectric units was developed. The solar or wind powered battolyser system stores electricity and utilises it to produce H2. The produced green H2 combusts with air in the cylinder to drive the turbine and the electric generator. While the thermophotovoltaic (TPV) unit converts the heat radiation into electrical energy to maximise the power efficiency of the developed hybrid system. The result showed a better temperature distribution, higher pressure discharge on both pistons’ walls and increased energy efficiency by replacing a single-piston with the opposed piston cylinder combustor and using cylinder exit gas to generate more electricity. Steam coolant reduced the thermal stress on the cylinder wall. The mounted TPV unit on the cylinder wall converted the absorbed heat flux to 3.9 kW. The maximum power output of the solar PV and wind turbine systems was reached at an irradiance of 1200 W/m2 under ambient temperature conditions and a wind speed of 17 m/s. By using the exhaust gas from the cylinder to drive the gas turbine, 8.8 kW power output and an electrical efficiency of 31.9 % were recorded. NOx emissions <6 ppm and a CHP efficiency of 93.5 % were achieved for the developed hybrid system. The proposed system can substitute the current domestic gas boiler which is in the phase-out state.

An innovative bio-inspired Aquila technique for efficient solution of combined power and heat economic dispatch problem

In the field of power systems, the optimization challenge of combined heat and power units economic dispatch (CHPUED) holds immense importance. This study presents an improved Aquila optimization technique (IAQT) that effectively tackles the CHPUED. The primary objective of the enhanced IAQT model is to minimize the overall cost of power generation in CHP systems while satisfying demand and operational constraints. However, to achieve more accurate cost estimations and avoid suboptimal solutions, it is crucial to consider transmission losses in the optimization model. By incorporating transmission losses, the IAQT algorithm can allocate power generation resources more effectively, leading to improved system efficiency and reduced operational costs. The proposed IAQT algorithm addresses the limitations of the standard AQT and introduces novel features to enhance its search capabilities. One key limitation of the standard AQT is its heavy reliance on the best solution found during optimization. To overcome this drawback, the enhanced IAQT model eliminates the dependency on the best solution and enables a more thorough exploration of the search space. Moreover, the algorithm incorporates specific limitations and constraints for each dimension of the newly generated solutions, ensuring their feasibility and validity. The standard AQT and proposed IAQT are tested on CEC 20 benchmark functions. Moreover, the proposed approach is extensively evaluated through experimentation and testing on various scenarios, including 7–48-unit and large 96-unit systems with/without losses. Furthermore, the overall costs for the 7 unit-system are considered including the reserve constraint. The results exhibit the remarkable performance and efficiency of the enhanced IAQT model, outperforming the standard version and several previously reported results. This validation underscores the significant contribution of the study in addressing the CHPUED and highlights its potential for real-world applications.

Thermal and electrical performance analysis of a lightweight micro CHP system for recreational vehicles

For comfortable use of a Recreational Vehicle (RV), there is a need to supply electrical energy to recharge the batteries and supply the installed equipment, as well as thermal energy, for hot water and ambient heating. A conventional solution for supplying electrical energy is the installation of photovoltaic modules combined with connection to an electrical grid, when possible. Water heating is generally done using a passage gas heater or hybrid gas/electric storage heater. Imported vehicles have gas heating and many other vehicles have diesel heaters. To develop an alternative to currently available energy supply methods, this work proposes the creation of a cogeneration system for RVs. From a literature review, a research gap was identified in relation to micro CHP devices for RVs. In the development of this work, a micro CHP prototype was created, with 980 W of maximum electrical power, consisting of a single-cylinder internal combustion engine, an automotive alternator and heat exchangers for heat recovery. The prototype was enclosed and instrumented, allowing to evaluate the thermal power obtained in water flowing through exhaust gases, lubricating oil and cooling air heat recovery systems, in addition to measuring the electrical power of the alternator. Operational tests were carried out with 46 different test conditions, combining variations in the engine speed (N) and in electrical load. The prototype electrical efficiency reached 10.18 % ±0.2 % at 3008 rpm with 83 % load. The maximum electrical power was 0.746 kW±0.015 kW at 3637 rpm and 100 % load. The maximum thermal energy recovery rate was 3.267 kW±0.039 kW. Utilization factor reached 65.57 % ±0.33 % at 3208 rpm with 63 % load. Compared to traditional means of providing electrical power and thermal power for RVs, the prototype proved to be more advantageous when the demand is for electrical power and space heating. However, for conditions in which the demand is for electrical power and water heating, or just electrical power, the current solutions available are still more efficient.

Low-Carbon Economic Dispatch Model of Integrated Energy System Accounting for Concentrating Solar Power and Hydrogen-Doped Combustion

Against the background of carbon peak and carbon neutralization, in order to solve the problem of poor flexibility of integrated energy systems and wind power consumption while improving the potential of hydrogen energy emission reduction, this study proposes an integrated energy system that takes into account the coupling of concentrating solar power (CSP), hydrogen-doped combustion, and power-to-gas (P2G) conversion. Firstly, a mathematical model of a CSP-CHP unit is established by introducing a CSP power station, aiming at the defect of the “heat to power” mode in the CHP system. Secondly, the energy consumption of P2G hydrogen energy production is satisfied by surplus wind power. The utilization stage of hydrogen energy is divided into supply CHP combustion and CO2 methanation, forming a CSP-P2G-HCHP collaborative framework and establishing an IES low-carbon economic dispatch model with CSP-P2G-HCHP. At the same time, the carbon trading mechanism is introduced to constrain the carbon emissions of the system. Finally, an optimization strategy with the minimum sum of the operation and maintenance cost, the energy purchase cost, the wind curtailment cost, and the carbon emission cost as the objective function is proposed, and the CPLEX solver is used to solve and carry out multi-case analysis. The simulation results show that the carbon emissions are reduced by 6.34%, the wind curtailment cost is reduced by 52.2%, and the total cost is reduced by 1.67%. The model takes into account the carbon reduction effect and operating efficiency and effectively improves the new energy consumption capacity.

Residential Micro-CHP system with integrated phase change material thermal energy storage

This paper presents an analysis and experimental investigation of the effect of integrating Phase Change Material (PCM) within a heat exchanger within a Micro Combined Heat and Power (Micro-CHP) system intended for residential applications. A commonly used Micro-CHP layout is replicated in a test rig to characterise the performance of two alternative heat exchanger arrangements. The first is a conventional arrangement where the exhaust gas produced by the prime mover is directed to an air-to-water heat exchanger to heat water and store it in a tank. In the second arrangement, PCM material is encapsulated within specially designed compartments in a heat exchanger to store part of the exhaust thermal energy from the prime mover while heating the water in the storage tank. The time needed to heat the water and discharge heat is compared for both cases, as well as the amount of thermal energy stored during the same operating period. The study also explored the potential to improve the designed unit by using different PCM materials. The test results show that adding 4.7 L capacity paraffin compartments within the heat exchanger extended the discharge time of the hot water by over 400 %, which reflects a marked improvement in the heat storage capacity of the system. This would result in a significant increase in the viable operating period of a CHP system. The one-dimensional analysis revealed that replacing the paraffin with ClimSel C58 PCM can reduce the charging time of the water tank by around 54 % improve the heat storage capacity by factor of 2.35 comparing to Paraffin. The proposed heat exchanger with encapsulated PCM has a potential in other applications such as storage of excess renewable energy or integration with heat pumps to improve matching of supply and demand and thus flexibility of an energy system with integrated intermittent renewables.

Realistic operation and strategic energy, economic and environmental analyses of a hybrid renewable energy based - micro combined heat and power

The expansion of emerging energy sources that are sustainable and cleaner has opened the chance for CHP systems to be integrated for higher efficiency and performance. Prior to the operation in a real system, the integrated micro-CHP system needs a comprehensive performance analysis. Combining with a realistic energy management, the strategic operation must be dealing with the complexity of the system components at the optimal energy serving cost and keep it environmentally friendly. This study develops and analyses the m-CHP system that integrates renewable energy sources coupled with a realistic load-based management. The components control and system management are developed through a validation of the actual data for each component and integrating them in a simulation environment using LABVIEW to ensure the system works as intended. The comprehensive assessments are conducted in terms of energy, economic and environmental aspects to evaluate the feasibility of implementing the system in the long-term practices. In addition, a critical comparison of the proposed method with the existing projects locally in Malaysia and globally is presented to illustrate the potential of the m-CHP for public and private buildings.During 25 years of the operation, the proposed m-CHP system achieved a primary energy savings ratio of 44.7 %, with a net present value of USD 17,790.42. For electrical and thermal loads, the proposed m-CHP could reduce carbon dioxide emissions by 53.1 % and 73.5 %, respectively.

A Distributed Multi-Timescale Dispatch Strategy for a City-Integrated Energy System with Carbon Capture Power Plants

In city-integrated energy systems containing electric–thermal multi-energy sources, the uncertainty of renewable energy sources and the fluctuation of loads challenge the safe, efficient, economic and stable operation of the integrated energy systems. This paper introduces a novel approach for the operation of a carbon capture plant/CHP with PV accommodation within a city-integrated energy system. The proposed strategy aims to maximize the utilization of photovoltaic (PV) power generation and carbon capture equipment, addressing issues related to small-scale CHP climbing constraints and short-term output regulation. Additionally, this paper presents a multi-timescale optimal scheduling strategy, which effectively addresses deviations caused by PV fluctuations and load changes. This was achieved through a detailed analysis of the CHP climbing constraints, carbon capture equipment operation and real-time characteristics of PV power generation. This paper introduces a fully distributed neural dynamics-based optimization algorithm designed to address multi-timescale optimization challenges. Utilizing rolling cycles, this algorithm computes both day-ahead and real-time scheduling outcomes for urban integrated energy systems. Theoretical analyses and numerical simulations were conducted to validate the precision and efficacy of the proposed model and algorithm. These analyses quantitatively evaluate the scheduling performance of PV power generation and carbon capture CHP systems across various timescales.

Exergoeconomic Analysis and Multi-Objective Optimization of an Integrated CHP System Based on Syngas-Fueled Planar Solid Oxide Fuel Cell

Exergoeconomic Analysis and Multi-Objective Optimization of an Integrated CHP System Based on Syngas-Fueled Planar Solid Oxide Fuel Cell

New Hybrid CHP System Integrating Solar Energy and Exhaust Heat Thermochemical Synergistic Conversion with Dual-Source Energy Storage

New Hybrid CHP System Integrating Solar Energy and Exhaust Heat Thermochemical Synergistic Conversion with Dual-Source Energy Storage

Multi-objective optimization of a biomass microCHP-ORC system under supercritical conditions

ORC cycle is one of the most efficient technologies for the utilization of low-grade heat. ORC systems cover a wide range of heat sources and power outputs. Apart from increasing the overall efficiency, CHP systems contribute to the decentralization of energy production, the conservation of primary fuel, the reduction of the emission of greenhouse gasses and the re-duction of the cost to the final consumer. This justifies the research activity around CHP-ORC systems. In the present paper, a steady-state thermodynamic model for a 50 kWel biomass microCHP-ORC was developed and four candidate fluids were selected: R124, isobutane, R245fa and isopentane. The multi-objective optimization under supercritical conditions was performed using the genetic algorithm. The thermal efficiency, the exergy efficiency and the total heat exchanger surface were selected as single objectives. The evaporation temperature and pressure and the pinch point temperature differences at the heat exchangers were selected as decision variables. Careful examination of the optimal results revealed a systematic ten-dency for high evaporation temperatures and pressures and low recuperator pinch point tem-perature differences. Recuperation was found beneficial in many aspects, especially at higher evaporation temperatures. Also, the use of cogeneration leads to overall system efficiencies that surpass 90%, while simultaneously saving at least 20% fuel. Lastly, isopentane was found to be the best-performing fluid.

On the Possibility of Using CHP From a 1.4MW Direct Fuel Cell at Kettering University Engineering Building – A Demonstration Study

The concept of using a distributed power generation and a combined heat and power principle – CHP in public buildings, commercial facilities is widely gaining public acceptance as a result of reduced energy cost, reliable power supply and environmental and health issues. By using the exhaust heat from a high temperature fuel cell at 400 oC for cogeneration, space heating, to provide warm water for facility use - (swimming pool and sporting locker room) and cooling in chillers at no additional cost, we reduce energy cost and preserve the environment. By bottoming cycle, the efficiency of the entire system is increased. A study is conducted to compare the economic impact of using the CHP system against the conventional heating system using furnaces.

Heat load model for small-scale CHP planning

Present-day world energy policy is based on two main directions: energy efficiency and environmental protection. Efficient Combined Heat and Power production is one of the energy consumption effective methods, where CHP production from the renewable fuels is preferable. [1] In order to plan for the most economical, technical and environmental optimal CHP system, it is especially important to estimate the expected heat demands and heat load profiles for the district heating area. This paper describes a method for estimation of heat load profile for a given district heating area by dividing it to three different heat load types: Temperature depended heat load; Constant heat load; User defined heat load. The paper provides a complete description of above mentioned heat load types, equations as well as calculation examples. Calculation results are compared to hourly measured heat loads to estimate accuracy of a proposed model.

Feasibility study of biogas in CHP plant for a pig farm

Cogeneration, or the Combined production of Heat and Power (CHP), is being promoted at EU level as a way of reducing green house gas (GHG) emissions from traditional power plants. For a long time, CHP systems have been used successfully in industry but it can be developed across numerous market sectors, including zootechnics farms. Currently with the rapid global economic change and the increasing needs for environmental sustainability it is timely to review pig farm heat and electrical power options to reduce costs and optimize environmental outcomes. This paper describes a feasibility study of biogas CHP plant in a medium pig farm in Italy. Biogas, produced by pig manure, is burned in CHP system to satisfy the demand of electricity and heat. Results illustrate how the utilization of gaseous product from pig farm effluent (biogas) as fuel for heat and power generation can reduce both energy cost and CO2 equivalent GHG emission in the environment.

Investigation of the technical potential of a hydrogen powered phosphoric acid fuel cell (PAFC) for CHP

Due to the fluctuating feed-in of renewable energies, controllable power plants such as highly efficient CHP plants (combined heat and power) will continue to be required to cover the residual load. Gas engines and turbines currently dominate the natural gas-based CHP market due to their low investment costs and acceptable electrical efficiency. In the event of a future fuel switch due to the energy transition from natural gas to hydrogen, fuel cell systems are becoming increasingly important due to their very high efficiency and improved dynamics in hydrogen operation and can therefore represent an alternative to gas engines and turbines. In addition to a possible fuel switch, good dynamic and full heat utilization represents an additional challenge for CHP systems. Therefore, this study aims to investigate the influence of a fuel switch from natural gas to hydrogen on the operation of a fuel cell (PAFC) in terms of efficiency, heat utilization and dynamics. It was shown that the electrical efficiency of the hydrogen-operated PAFC is significantly higher than in natural gas operation due to the omitted reformer and the associated reformer losses. In hydrogen operation, there is also no limitation of the dynamics by the reformer. Furthermore, in hydrogen operation there is a more favorable ratio of high-temperature to low-temperature heat, which facilitates the use of heat. Detailed and validated simulation models in Aspen Plus are used as the basis for this investigation.

Energy, exergy and exergo-economic analysis of a novel SOFC based CHP system integrated with organic Rankine cycle and biomass co-gasification

This paper proposes a novel SOFC based cogeneration system, consisting of biomass co-gasification, SOFC power generation and ORC waste heat recovery, to achieve the efficient and clean utilization of poultry litter. Based on the conceptual design, the energy, exergy and exergo-economic analysis are conducted, including sensitivity analysis, uncertainty analysis and multi-objective optimization. Results show that when using straw as the co-gasification biomass with poultry litter, the highest energy utilization efficiency of 44.70 % is obtained with the electricity and heat production of 162.02 kW and 52.41 kW, respectively. The biomass gasifier and the SOFC stack have the highest exergy destruction, accounting for 24.43 % and 19.99 % of the total. Sensitivity analysis presents complex results concerning mass fraction of poultry litter, water content, equivalent air ratio and water-carbon ratio, etc. The optimal solution for the current optimization problem is obtained. When poultry litter mass fraction is fixed at 25 %, TSOFC = 852 °C and uf = 0.73, the exergy efficiency is obtained as 41.95 % and the overall exergy cost per unit is obtained as 42.35 $/GJ. This paper investigates a novel cogeneration system relying on the biomass co-gasification of poultry litter, providing a new solution for poultry litter treatment and sustainable development of agriculture, forestry and husbandry.

Recovery of Flared Natural Gas with High CO&lt;sub&gt;2&lt;/sub&gt; Content Using SOFC CHP System: Feasibility Study for Neem-Field, Sudan

Flared natural gas emissions are one of the main sources of environmental pollution and global warming. To recover this gas, the presence of impurities like CO2 in high concentrations forces oil producers to escape from investing in such intensive processing. Several implementations of no flaring methods have been reported in the literature, however, there have been limited concerning the bulk-CO2 natural gases. This research developed an innovative idea for the use of the SOFC CHP system to recover flared bulk-CO2 associated gas of Neem-Field in Western Sudan. The exergy of the system and the performance of the SOFCs are investigated in this paper, in addition to environmental and economic analysis. The simulation (Cycle-Tempo©) results demonstrate that the proposed system can generate 1 MW electrical power and 0.068 MW thermal energy with efficiency approached 43.3% (based on LHV). The exergy analysis showed that 38% of system losses occurred in the air preheaters. Instead of conventional gas-burning, recovering the flared gas reduced the equivalent CO2 GHGs emissions by 80%. Overall, the novel solution found to be environmentally friendly, and economically appealing with a total capital investment estimated to be US$1.175 million and a cost of electricity (COE) of 4.07 cents per kWh.

Multi-objective optimization application for a coupled light water small modular reactor-combined heat and power cycle (cogeneration) systems

The goal of this research is to propose a way to maximize small modular reactor (SMR) utilization to gain better market feasibility in support of carbon neutrality. For that purpose, a comprehensive tool was developed, combining off-design thermohydraulic models, economic objective models (levelized cost of electricity, annual profit), non-economic models (saved CO2), a parameter input sampling method (Latin hypercube sampling, LHS), and a multi-objective evolutionary algorithm (Non-dominated Sorting Algorithm-2, NSGA2 method) for optimizing a SMR-combined heat and power cycle (CHP) system design. Considering multiple objectives, it was shown that NSGA2+LHS method can find better optimal solution sets with similar computational costs compared to a conventional weighted sum (WS) method. Out of multiple multi-objective optimal design configurations for a 105 MWe design generation rating, a chosen reference SMR-CHP system resulted in its levelized cost of electricity (LCOE) below $60/MWh for various heat prices, showing economic competitiveness for energy market conditions similar to South Korea. Examined economic feasibility may vary significantly based on CHP heat prices, and extensive consideration of the regional heat market may be required for SMR-CHP regional optimization. Nonetheless, with reasonable heat market prices (e.g. district heating prices comparable to those in Europe and Korea), SMR can still become highly competitive in the energy market if coupled with a CHP system.

Experimental and numerical characterization of hydrogen combustion in a reverse-flow micro gas turbine combustor

This study conducts experimental and numerical investigations on a stagnation-point, reverse-flow combustor to examine the effect of its design features on the combustion behavior and emission characteristics of non-premixed, turbulent hydrogen/air flames. The study covers a wide range of equivalence ratios, from ultra-lean to stoichiometric, and thermal power inputs varying between 5 kW and 20 kW. The main motivation behind this design is to achieve passive recirculation of flue gas within the combustor to enhance dilution of the incoming charge, thus potentially leading to relatively uniform thermal fields, lower temperatures, and suppressed NOx emissions. This design concept is implemented in a micro gas turbine – a practical energy conversion device tapped to play a major role in decarbonizing CHP systems suitable for small-scale industries. Optical chemiluminescence measurements, in addition to thermocouple-based temperature and Quantum Cascade Laser (QCL) spectroscopy-based exhaust emissions measurements, were conducted for all the test cases. Spatial OH* signal intensity is used as heat release signature to identify distinct features of the test flames, allowing for useful information on the nature and dynamics of the combustion process within the combustor. The results show stable hydrogen/air flames for all the operating conditions; however, a more distributed combustion is observed at higher powers for all the given equivalence ratios. Relatively higher NOx emissions at φ >0.2 suggest the lower achieved mixing between burnt and fresh gases, particularly in the non-preheated case, prevent a thorough dilution of the fresh mixture. The latter is necessary to achieve low-temperature, uniform thermal fields – an essential for low thermal NOx emissions in gas turbine combustors. Further, CFD results show that preheating considerably changes flow field dynamics and recirculation pattern for better mixing; however, this also dramatically increases thermal NOx emission, with the lowest levels observed at φ = 0.2, while the peak occurs at φ = 0.4. Finally, a ‘brute-force’ sensitivity analysis shows that thermal NO and NNH pathways contribute the most to NO formation in hydrogen/air flames.

Designing and performance assessment of a hybrid CAES based CHP system integrated with solar energy and heat pump

In this paper, a novel combined heat and power system based on compressed air energy storage (CAES) coupled with a solar collector system was introduced. Based on the significant effect of heat pumps in improving heat quality, the heat pump and solar energy are adopted to improve energy storage and economic performance. To maximize the effective utilization of solar energy, the energy dispatch scheme of the system has been studied in detail. The system's performance under multiple operating conditions has been evaluated. Moreover, to further explore the optimization potential of the solar-coupled compressed air energy storage system, important factors such as the distribution proportion of thermal oil and key temperature have been emphasized and analyzed. The optimization of key temperature, distribution proportion of thermal oil, and operating conditions can enhance the cascade utilization of energy, and also provide a comprehensive approach for the design and optimization of the proposed system. Parametric sensitivity analysis was first conducted. Results show that the charging pressure should be close to the discharging pressure and there is no local optimal distribution ratio for the thermal oil. The optimal condition under design constraints is also determined, the system power efficiency, energy efficiency, and power-to-power efficiency reached 0.297, 0.851, and 0.570, while the levelized cost of storage of the system is 0.527 $/kWh, the dynamic payback period is 9.516 and simple payback period is 7.428 under the specified conditions. The output power and heat in 6 h of discharging are 3829.50 kWh and 7147.48 kWh, respectively, with a total investment cost of 7373.57k$. Moreover, the exergy and economic analyses were then conducted. The highest exergy losses were caused by the solar collector system with 29.01% of the total loss. The turbines and the solar system also had the highest economic cost, indicating directions for further optimization.

Comparative study on thermodynamic analysis of solid oxide fuel cells supplied with methanol or ammonia

The increasing demand for green hydrogen and power production necessitates the development of novel and upgraded power generation technologies. The solid oxide fuel cell combined heat and power (SOFC–CHP) system is a promising solution due to its high efficiency, clean operation, and fuel flexibility. In practical terms, SOFCs can operate using a variety of fuels such as alcoholic fuel, hydrogen, ammonia, etc. Recently, methanol and ammonia have become noteworthy alternative fuel options as it possesses advantages such as low transportation cost and high hydrogen storage capacity. In this paper, we have established two SOFC–CHP models fueled by methanol or ammonia integrated with the steam Rankine cycle. A comprehensive thermodynamic model is proposed for energy and exergy analyses. Sensitivity analysis is performed to study the system's characteristics. The results show that the SOFC–CHP system fueled by ammonia exhibits superior performance, the maximum electrical power, efficiency, and exergy efficiency is 430W, 7% and 10% greater than the methanol fueled system. The operating temperature is about 30K higher in methanol supplied system. The largest thermal power difference can reach 0.65 kW. Overall, the ammonia fueled SOFC–CHP system shows greater potential than that fueled by methanol.