Conventional Combined Cooling, Heating And Power System Research Articles

Integrated combined heating, cooling and electricity system based on triple-effect free-piston Stirling configuration

Conventional combined cooling, heating, and power (CCHP) systems, involving multiple energy conversion technologies, are composed of a variety of coupled subsystems with different working principles. To solve the problems of bulky structure, operational complexity, and high initial investment cost, a novel integrated combined heating, cooling, and electricity system based on the same energy conversion technology with a triple-effect free-piston Stirling configuration was proposed. Compared with the traditional system, the novel integrated system can cool, heat, and generate power using one machine without introducing additional devices. Some verification experiments were tested on a built experimental platform to validate the feasibility of the concept of this configuration. The result shows that the system was able to obtain the highest values of COPc, COPh, and the output performance coefficient of 0.26, 1.28, and 1.54, respectively, which can save 39 % of energy consumption compared with traditional independent energy-supplying systems when providing the same cooling and heating capacity and electricity under typical working conditions. It is expected that the reported result can facilitate a practical application in decentralized CCHP systems.

Performance analysis and application of a novel combined cooling, heating and power system integrated with multi-energy storage system

The dynamic fluctuations of user energy demand places the combined cooling, heating and power (CCHP) system in a perpetual state of off-design operation, leading to significant performance deterioration. Integrating an energy storage system with the CCHP system is an effective approach to this issue. However, conventional methods often segregate the storage of cooling load, heating load and power of CCHP system, limiting their conversion and resulting in suboptimal utilization and low efficiency. Therefore, this study proposes a novel CCHP system integrated with multi-energy storage system, allowing flexible release cooling load, heating load and power to meet diverse user load profiles. Mathematical modeling, thermodynamic analysis and environmental assessment are conducted. The case study demonstrates that the proposed system surpasses the conventional CCHP system in exergy efficiency ηex, primary energy rate PER, primary energy saving ratio PESR, carbon dioxide emission reduction ratio CDERR and cost saving ratio CSR of the proposed system increase by 3.1 %, 13.6 %, 9.0 %, 6.2 % and 8.4 %, respectively. The proposed system effectively balances user energy demand and energy supplied by the CCHP system, efficient utilization of diverse energies, significantly enhancing off-design performance, and yielding high efficiency, energy saving, and reduced carbon emissions.

Analysis of performance and suitable users of CCHP systems with active thermal energy storage

Introducing a thermal energy storage (TES) unit in the combined cooling, heating, and power (CCHP) system can help alleviate the supply–demand energy mismatch and improve the system performance. However, the active regulation function of TES has not been fully exerted and the applicable user scenarios of the CCHP-TES system are not clear due to the limitations of case studies. In this work, based on the supply–demand energy matching principle, an improved design of active thermal energy storage is proposed to further develop the role of TES units. Meanwhile, to overcome the limitations of case studies and obtain the universal applicable user scenarios, dimensionless user load characteristic parameters are used to analyse the correlation between the user characteristics and the system performances. The system thermodynamic model and integrated design methodology are developed. The results indicate that the average energy-saving rates of the proposed active CCHP-TES system are higher than 14.63%, and the maximum differences compared with those of the conventional CCHP system and passive CCHP-TES system are 22.27 and 29.20 percentage points, respectively. Moreover, among the user load characteristic parameters, the cooling/heating-to-electricity ratio has the greatest impact on the performances of the proposed system, the duration time of the peak electricity load the next, and the peak-to-valley ratio of electricity load the least. In most cases, the larger the cooling/heating-to-electricity ratio and the duration time of the peak electricity load are and the smaller the peak-to-valley ratio of electricity load is, the better the system performance will be. Finally, the applicable user scenarios of the proposed system are given quantitatively and the system is applicable once the peak-to-valley ratio of electricity load is less than 2 and the cooling/heating-to-electricity ratio is greater than 0.5.

Thermodynamic analysis of a CCHP system integrated with a regenerative organic flash cycle

• A new CCHP-ST-OFC system is proposed and thermodynamically analyzed. • Effects of operating parameters on system energy performance were studied. • A negative feedback operation strategy was proposed and adopted in a studied case. • The negative feedback strategy decreases natural gas consumption by 9%. Combined cooling, heating and power (CCHP) systems have received wide attention for their potential of high efficiency and energy conservation. In this work, a novel CCHP system is designed coupling the solar thermal input (ST) system and the regenerative organic flash cycle (OFC) system. The OFC subsystem could recycle two kinds of heat sources to achieve cascade utilization of heat energy. The CCHP-ST-OFC system is evaluated by comparing with the conventional CCHP system and the CCHP-ST-ORC system (organic Rankine cycle). The effects of several operating parameters on the thermodynamic performance are discussed. Based on the negative feedback regulation, an operation strategy is proposed and applied to buildings to verify the thermodynamic economy. The results demonstrate that the electricity and heat provisions are 275.0 kW and 211.5 kW, which are 4.7 kW and 19.3 kW higher than the CCHP-ST-ORC system. The electricity of the OFC subsystem is 15.0 kW and 47% higher than the ORC system. Moreover, changing the smoke outlet temperature in the waste heat recovery equipment could effectively adjust the heat provision and power generation. The trend of the day and night power generation with the mass flow rate of the heat source is reversed. The energy provision and performance increased with the increasing partial load ratio of the internal combustion engine. The building case study reveals that the exergy efficiency of the CCHP-ST-OFC system is 38.7% and the primary energy ratio is 53.1%, respectively. Meanwhile, the natural gas consumption of the CCHP-ST-OFC system is 5.14 × 10 5 m 3 /year, with a 9% reduction than the CCHP-ST-ORC system.

Design of Promising Working Fluids for Emergent Combined Cooling, Heating, and Power (CCHP) Systems

Combined cooling, heating, and power (CCHP) systems enable the simultaneous supply of electricity, heating, and cooling, thus meeting the major energy needs of humans in a single device. Conventional CCHP systems consist of the combination of a prime mover, heating, and cooling system, each of them operating with a thermodynamically suitable working fluid. Recently, novel CCHP cycles, based on the use of a single working fluid for the whole operation, have been proposed. Since the choice of the working fluid represents a design challenge in the development of such technologies, in this work, a product design approach for the selection of suitable working fluids for emergent CCHP applications is presented. A database search is implemented to screen about 60 000 structures included in the DDB, the Design Institute for Physical Properties, and the NIST TDE databases. The screening considers thermodynamic, process-related, constructional, safety, and environmental constraints. Moreover, the tc-PR equation of state is used to ensure the quality of the calculation of thermophysical properties and the performance assessment of promising working fluids. This study shows that flammable fluids such as vinylacetylene or HFC-152 have a good potential for CCHP applications. In the case of reinforced safety restrictions, HCFO-1233zd(E) seems to be an interesting candidate since it is nonflammable and nontoxic.

Investigating the effects of integrating an absorption heat transformer with a combined cooling, heating and power system: A thermodynamic and economic analysis

Regarding the significance of low-temperature heat sources in combined cooling, heating, and power (CCHP) systems, it is necessary to find practical and economical ways to maximize the efficient use of available energies. Integrating the auxiliary cycle with the main system and changing the configuration are among the useful solutions to achieve this purpose. In this work, a combination of both solutions is presented, accordingly, an absorption heat transformer cycle (AHT) is integrated with a conventional CCHP system, which is made of organic Rankine cycle, absorption refrigeration cycle, and a heat exchanger. Three conventional CCHP systems with sequential (Configuraion1), parallel (Configuraion2) and a combination of sequential and parallel (Configuraion3) configurations are considered. It is shown that among the Configuraion1, Configuraion2, and Configuraion3, Configuraion1 has the highest energy efficiency; therefore, it is selected to be compared with the proposed integrated system with AHT. This integration affects the outputs production and also energy consumption; therefore, four different modes (standpoints) are taken into account to compare the production of power (mode A), cooling (Mode B), heating (mode C), and energy consumption (mode D) of these two systems. Also, from the exergy, environmental, and economic aspects, these two systems are compared. Regarding mode D, it is indicated that the energy and exergy efficiencies, energy consumption and carbon emission of the proposed system are improved 17.68%, 17.68%, 15.03%, and 15.02%, respectively. It is noted that for the heat source stream temperature range of 90 °C–120 °C, the proposed system has better performance than the Configuration1. Despite the additional costs of integrating AHT with the CCHP system, the proposed system has 517018.1 US$/year cost saving (which is 32.65% of the investment cost of Configuration1) if biomass is used as a heat source, which indicates its higher economic advantage than the Configuration1. Also, comparing the proposed system with Configuration1, the amount of power, cooling and heating productions are improved 27.98%, 102.15%, and 36.87%, respectively.

Multi-objective optimization of a solar hybrid CCHP system based on different operation modes

Abstract This paper carries out a multi-objective optimization of a solar hybrid combined cooling, heating and power (CCHP) system, based on the objective functions of annual cost saving ratio (CSR) and primary energy saving ratio (PESR). The system is modeled in three modes: 1) following electrical load (FEL); 2) following thermal load (FTL) and 3) following thermal load and selling power to grid (FTL-S). Non-dominated Sort Genetic Algorithm- II (NSGA-II) is adopted to find the Pareto front solutions of the potentially optimal configuration and corresponding criteria. The results show a conflict between cost saving and fuel saving. By selecting the compromised optimal point, the CSR increases to 25.04% and the PESR increases to 37.86% on average. The system in FEL mode performs best in energy saving and the system in FTL-S mode performs best in economy. The solar hybrid CCHP system is also compared with other three systems: 1) conventional CCHP system; 2) CCHP system with photovoltaic assisted only and 3) CCHP system with solar collector assisted only. In the end, the sensitivity analysis is implemented and the results present that energy prices and the efficiency of major equipment have varying degrees of impact on system performance.

Performance investigation of a novel hybrid combined cooling, heating and power system with solar thermochemistry in different climate zones

To alleviate the shortage of natural gas resource and ease carbon emissions, a novel solar-driven combined cooling, heating and power (CCHP) system is designed and optimized using the genetic algorithm in the work. Different from the process of direct combustion in a conventional CCHP system, natural gas is firstly converted into syngas by a solar-driven natural gas reforming step, which is consumed in an efficient tri-generation system. Energy, economic and environmental evaluations on five office buildings in different climate zones in China are implemented to validate the advantages of the proposed system. Results show that the annual maximum primary energy saving, total cost saving, and CO2 emission reduction are 69.76%, 49.80%, and 71.55%, respectively. The system located in severe cold zones, where solar energy is abundant and building requires more heat load in whole year, achieves the highest benefits in comparison with separate systems. Furthermore, the sensitivities on the price fluctuations of electricity, natural gas and solar field to the system profits are investigated, which indicates that the influence of electricity price on the system performance is the most significant. Thus, a promising method for reducing the natural gas consumption and improving the utilization efficiency of solar energy is provided.

Performance investigation of a solar-assisted hybrid combined cooling, heating and power system based on energy, exergy, exergo-economic and exergo-environmental analyses

This paper proposes a solar-assisted hybrid combined cooling, heating and power (CCHP) system that consists of an internal combustion engine, solar heat collectors, an absorption heat pump, a heat exchanger, and a thermal storage tank. On the basis of thermodynamic modelling and validation, the hybrid system was investigated from its energy, exergy, exergo-economic and exergo-environmental performances. The heat storage ratio and supplemental heat ratio were defined to consider the dynamic off-design operations and evaluate the contributions of thermal storage and supplement under the static design conditions, whose impacts on system efficiency and unit cost of products were discussed. For a specific case study, the energy and exergy analyses with the Sankey diagrams indicated that the hybrid system achieves annual energy efficiency of 76.3% and exergy efficiency of 22.4%. The unit costs of products were determined using exergo-economic analysis based on energy level, and the costs of products including and excluding carbon dioxide emission cost were compared. Compared to the conventional CCHP system without solar energy, the hybrid system saves 11.3% of natural gas to reduce carbon dioxide emission and shortens the capital payback period by 1 year.

Complementary Configuration and Optimal Energy Flow of CCHP-ORC Systems Using a Matrix Modeling Approach

A mass of thermal energy from the combined cooling, heating, and power (CCHP) system will be wasted by the buildings with low ratio of heat to power demand. To further improve the using efficiency of the excess thermal energy, an active method, which adds the organic Rankine cycle (ORC) equipment in the CCHP system, is configured. A complementary configuration of this CCHP-ORC is also investigated. This paper presents a matrix modeling approach to establish a mathematical model of the CCHP-ORC system. The CCHP-ORC system can be viewed as a multiple input and multiple output (MIMO) model. Energy conversion of the system components is described as the efficiency matrices. Energy flow between the system components is described as dispatch matrices. Energy conversion and flow from the system input to output are modeled by a conversion matrix. The objective function and the constraints of the system are determined. The optimal operation strategies are obtained by solving the optimization problem of minimizing the evaluation criteria function. Comprehensive case studies are conducted based on a hypothetical CCHP-ORC system. The study results reveal that the effectiveness and economic efficiency of the proposed approaches outperform those obtained from conventional CCHP systems.

Optimal design and performance analysis of solar hybrid CCHP system considering influence of building type and climate condition

Abstract Incorporating solar energy technologies to the conventional combined cooling, heating and power (CCHP) system has been considered as an effective solution to mitigate the looming energy and environmental challenges. The mathematical model of a conventional CCHP system hybridized with photovoltaic (PV) panels and solar thermal collectors is built in this study. The particle swarm optimization (PSO) algorithm is employed to find the optimal size of key components of the solar hybrid CCHP system. The simulation work of solar hybrid CCHP systems in three building prototypes across seven climate zones is carried out to find appropriate design schemes of these cases. Besides, some guiding principles of the design of the solar hybrid CCHP system in early stage are summarized. The results show that the system under the following thermal load (FTL) strategy is the first choice in most cases of hospitals and hotels, except for the systems of hotels in the cold and very cold zones. On the contrary, the systems in offices perform better in the following electric load (FEL) mode in the majority of climate zones except for the hot-humid zone. Generally, the average optimal integrated performance (S) values of hospitals, hotels and offices can reach 28.95%, 28.20% and 22.69%, respectively.

Off-design heating/power flexibility for steam injected gas turbine based CCHP considering variable geometry operation

Owing to the fluctuating energy demand from consumer side, combined cooling, heating and power (CCHP) system operates at off-design condition most of the time. Moreover, the heating/power surplus is a common problem for the conventional CCHP system. In order to improve the precision of performance prediction and partly relieve the heating surplus, a steam injected gas turbine (STIG) based CCHP system considering off-design condition is proposed. The system consists of a steam injected gas turbine, double-pressure heat recovery steam generator (HRSG), heat exchanger, absorption chiller and auxiliary boiler. Two different operation strategies including turbine inlet temperature (TIT) strategy and variable guide vanes (VGVs) strategy, are illustrated to access the part-load performance of gas turbine and CCHP system. The performance indicators, like primary energy saving rate (PESR), primary energy rate (PER) are set up to evaluate the thermodynamic performance of the CCHP system. A simple gas turbine (SGT) based CCHP is chosen as the comparative object and two energy demand cases are selected to validate the advancement. The results show that VGVs strategy does not improve the gas turbine efficiency significantly but bring more exhaust heat into HRSG. VGVs strategy advances the heating to power ratio, PESR and PER around the whole part load condition, i.e., PESR is elevated from 0.3254 to 0.3743 by VGVs at the half of gas turbine load without injected steam. Injecting steam is a more effective way to improve gas turbine efficiency rather than using VGVs strategy while implementing same gas turbine load. Steam injection does not always enhance the PESR, but the PER keeps decreasing as injected steam flow increases around the whole load. STIG based CCHP system with VGVs operation strategy gets the best performance among these studied approaches, and the maximum enhancement of PESR reaches 0.3171 in the proposed energy demand cases.

Multi-objective assessment, optimization and application of a grid-connected combined cooling, heating and power system with compressed air energy storage and hybrid refrigeration

As one of attractive technology of energy conservation, combined cooling, heating and power (CCHP) system has brought about widespread attention. However, the variability of users demand has limited the application of CCHP system. To ensure stable and efficient operation, the compressed air energy storage is considered to be integrated with CCHP system. A grid-connected CCHP system with compressed air energy storage (CAES) and hybrid refrigeration is proposed in this paper. The power from grid is stored in CAES at off-peak time and released at on-peak time. The hybrid refrigeration system including LiBr absorption chiller and electric compression refrigerator provides cooling load to users. A multi-objective assessment and optimization synthetically considering energy, economy and environment are presented. The multi-objective indicator used as objective function to optimize each component capacity of the proposed CCHP system. A sensitive analysis of key parameters and performance comparison with conventional CCHP system have been carried out. The results shows that when the capacity of gas turbine is 691 kW, the comprehensive performance of the proposed CCHP system is the optimal performance. The power price, natural gas price, compression ratio and turbine inlet temperature of CAES have great influence on the performance of the proposed CCHP system. Meanwhile, the multi-objective indicator’s value of the proposed CCHP system is more than conventional CCHP system 4.85%.

A new hybrid photovoltaic/thermal and liquid desiccant system for trigeneration application

Conventional combined cooling, heating and power (CCHP) systems based on fossil fuels, with an acceptable energy performance, however, intensify the greenhouse effect worldwide. Using solar energy in distributed energy systems has the potential to further reduce fossil fuels consumption, and ease carbon emissions. This paper proposes a novel CCHP system by combining concentrated photovoltaic/thermal (PV/T) technology with an advanced air-handling process that realizes independent control of temperature and humidity. The heat produced from a PV/T collector is for desiccant regeneration in a two-stage liquid desiccant cycle in summer, and can be directly supplied to nearby users in winter. An office building under typical climate conditions of Beijing in 2002 was adopted to determine its various energy demands. Due to the efficient use of solar energy, annual energy saving ratio and CO2 emissions reduction ratio are predicted to be 73.28% and 74.55%, respectively. Two extreme conditions determining whether the excess heat from the PV/T collector is used were compared to demonstrate the top and bottom limitations of economic performance. The integrated performance, considering energy, environment and economic factors, reaches 37.48% when no excess heat from PV/T collector is used, and it can be further improved by thermal storage or recovering the excess heat to produce other products. This study provides a new solar utilization technology for trigeneration with advanced integrated performance.

Thermodynamic model development and performance analysis of a novel combined cooling, heating and power system integrated with trigenerative compressed air energy storage

As an energy comprehensive utilization technology, combined cooling, heating and power (CCHP) system has received much attention in many countries. Due to the variability of users demand, the CCHP system is often running at off-design condition. CCHP system integrated with energy storage system is an efficient method to improve the off-design performance of CCHP system. A novel CCHP system with trigenerative compressed air energy storage (T-CAES) is proposed in the paper, which can meet various forms energy demand of users. A comprehensive thermodynamic model of the system has been set up, and the thermodynamic performance analysis has been done. Furthermore, a sensitivity analysis is conducted by the key parameters effected on performance of CCHP system integrated with T-CAES. The comparison of thermodynamic and economic analysis between the novel CCHP system and conventional CCHP system are carried out in application of office building. The primary energy rate of novel CCHP system is 85.57%, the primary energy saving ratio of novel CCHP system is 26.87%, and the total cost saving ratio of novel CCHP system is 30.55%. The result shows that the performance of the CCHP system integrated with T-CAES is superior to conventional CCHP system.

Optimization and performance analysis of solar hybrid CCHP systems under different operation strategies

The hybridization between conventional combined cooling heating and power (CCHP) systems and solar systems has been considered as a good solution to the urgent energy and environment issues. This study develops the mathematical model of a CCHP system hybridized with PV panels and solar thermal collectors. The particle swarm optimization (PSO) algorithm is adopted to find the optimum values of design parameters. Based on the energy output characteristic of the solar hybrid CCHP system, five operation strategies of the conventional CCHP system are adjusted and applied for the solar hybrid CCHP system. The simulation work of the hybrid CCHP systems based upon a hotel building in Atlanta is carried out to find an appropriate design scheme. The results show that the hybrid CCHP system under the FEL-ECR mode is the best choice. Besides, its PESR, CO2ERR and ATCSR can reach 36.15%, 53.73% and 4.16%, respectively. Compared with a conventional CCHP system, the hybrid CCHP system achieves better energy-saving and CO2 reduction performance. However, the hybrid CCHP system consumes more annual total costs because of its high initial investment.

Thermodynamic model development, experimental validation and performance analysis of a MW CCHP system integrated with dehumidification system

Combined cooling, heating and power (CCHP) systems, which have the advantages of energy saving and environmental protection, have attracted more and more attentions. Great deals of works have been done, but most of them are theoretical research. It is still lack of experimental research for large scale CCHP system in practical application, and an overall off-design thermodynamic model is also desired to simulate or exam the system performance. In this work, a novel CCHP system integrated with dehumidification system is proposed for further utilizing waste heat, in which an internal combustion engine (ICE) is used as prime mover, its heat of flue gas and the heat of jacket water above 81 °C are used to drive absorption chiller, and the heat of jacket water below 81 °C is used to drive absorption dehumidifier. A comprehensive off-design thermodynamic model and evaluation of the system is established. The tested results of a MW CCHP system integrated with dehumidification system are used to validate the model, and the thermodynamic performance analysis is also carried out. The thermodynamic performance comparison between the CCHP system integrated with dehumidification system and conventional CCHP system has been done. The results show that: the simulated values are basically in keeping with those experimental results; when the output power of ICE is 1200 kW, the primary energy rate of the MW CCHP system can go up to 84.0%, the primary energy saving ratio achieves 32.77%, and exergy efficiency is 42.45%; the thermodynamic performance of the proposed CCHP system is better than conventional CCHP system.

Performance analysis of a liquid absorption dehumidifier driven by jacket-cooling water of a diesel engine in a CCHP system

This article addresses the tough problem of effectively utilizing the low-grade residual heat of jacket-cooling water (JCW) from an internal combustion engine in combined cooling, heating, and power (CCHP) systems. An experimental platform was set up for this purpose, in which the JCW was used as a heat source to drive a LiCl liquid absorption dehumidifier (LAD). The thermodynamic model of the LAD in a CCHP system was established to correlate heat- and mass-transfer of the LAD with the output power of the engine, and the performance of the system was analyzed. An experiment and modelling study showed that increasing the output power of the engine resulted in increases in both the JCW temperature and the LAD dehumidifying capacity, leading to lower relative humidity of the outlet air. A thermodynamic performance comparison of the CCHP system with and without a LAD was performed, and the thermodynamic performance of the CCHP system with the LAD was superior to a conventional CCHP system without it.

Off-design performances of gas turbine-based CCHP combined with solar and compressed air energy storage with organic Rankine cycle

The conventional CCHP systems often operate at part load and cause power surplus under the operation mode of power following thermal load. In order to improve the energy efficiency of CCHP systems, a novel combined cooling, heating and power (CCHP) system combined with compressed air energy storage (CAES) was proposed. However, the output power of CAES was probably not high due to the low temperature of high-pressure air at air turbine inlet. In this paper, solar energy was introduced to heat the high-pressure air from air storage cavern. For the further energy utilization of the air turbine exhaust with relatively high temperature, an organic Rankine cycle (ORC) was proposed to recover the heat carried by air turbine exhaust. To obtain the off-design characteristics of the proposed system, the typical off-design models of gas turbine, compressor and air turbine were built through the performance equations of each component. The sensitivity analysis on S-CAES with ORC system was investigated to evaluate the effects of several key parameters on its performances. The results show that the energy efficiency and exergy efficiency of S-CAES with ORC system reach 98.30% and 68.94% respectively, in a whole round trip cycle. A case study of the proposed system in a typical hotel building with 180,000 m2 located in South China concludes that, compared with the conventional CCHP, the energy consumption can be reduced by 124.78 GJ, 33.82 GJ and 62.1 GJ and the average energy efficiency increased by 7.72%, 1.47% and 3.61% in summer, transition season and winter typical days, respectively.

Investigation of the Cofiring of Methane and Biosyngas for Combined Cooling, Heating, and Power Generation with Zero Carbon Dioxide Emissions

AbstractA new chemical looping combustion (CLC) of biosyngas and methane in a system with combined cooling, heating, and power (CCHP) is presented. The aim of the integration of CLC into the CCHP system is to obtain zero CO2 emissions and to reduce exergy destruction within the combustion process. With the increase in the biomass‐to‐methane mass ratio from 0 to 1 (referred to as 100 %), the total energy output increases from 637.17 to 746.62 kW, and there is a simultaneous reduction of both the energy and exergy efficiencies from 91.70 to 82.10 % and from 43.32 to 37.84 %, respectively. However, the primary energy savings ratio benefits from an increase of the biomass mass ratio (from 0 to 1) and increases from 42.80 to 46.36 %. Furthermore, a conventional CCHP system is developed and simulated for comparison. To discuss the feasibility of this process, the effect of the gas conversion ratio in the CLC system on the overall efficiency was analyzed and the autothermal operation strategy of CLC was considered.