Combined Cooling, Heating And Power System Research Articles

An improved operation strategy for CCHP system based on high-speed railways station case study

Operation strategy significantly affects the economic and environmental performance of combined cooling, heating and power (CCHP) system. An improved strategy following balanced heat-electrical load (FBL), which includes three sub-strategies of various redundant energy, was proposed for a CCHP system with heat pump. The proposed FBL strategy was applied to a CCHP system in a high-speed railway station, and the performance of FBL strategy was compared with that of following hybrid electric-heating load (FHL) strategy. The optimal rated gas turbine capacity was optimized firstly under various strategies to guarantee the fairness of comparison. The primary energy consumption rate, CO2 emission reduction rate, operating cost savings rate and comprehensive performance matching (CPM) parameter of the CCHP system were adopted as criteria to evaluate the system performance. Results showed that all the criteria were improved by using FBL strategy with the CPMs of the three sub-strategies increasing 20.82%, 14.8% and 18.52% respectively. Secondly, highrelevance was observed between CPM and the thermoelectric ratio. Based on analyses of other two typical loads of Harbin and Kunming, a linear function was developed between the CPM and the load thermoelectric ratio, which can provide a direct and convenient method to evaluate the CCHP performance. Finally, the sensitivity analysis of the electricity price to gas price ratio indicated that the CCHP system was not applicable when the ratio was less than 1.79. The amount of redundant energy could not be adopted as a criterion for the system performance in the comparative analysis of various operation strategies, but the increasing redundancy energy led to the degradation of the system performance under the same operation strategy.

Preliminary conceptual design and thermo-economic analysis of a combined cooling, heating and power system based on supercritical carbon dioxide cycle

Application of the supercritical carbon dioxide (sCO2) cycle to advanced nuclear reactors have confirmed a number of benefits. However, abundant low-level cooling heat is wasted in the gas cooler. A combined cooling, heating and power (CCHP) system, which integrates a sCO2 cycle with an Organic Rankine cycle (ORC) and an ejector refrigeration cycle (ERC), is proposed to realize the energy cascade utilization for nuclear power. The thermodynamic and exergoeconomic models of the novel CCHP system are established for system simulations under steady-state conditions. Parametric analysis results show that the decrease of ORC turbine back pressure or the increase of sCO2 turbine inlet temperature and ERC evaporation temperature contribute to both design thermodynamic and exergoeconomic performance. In addition, there exist optimal values of the sCO2 compressor pressure ratio and the bottoming cycle turbine inlet pressure to minimize the total product unit cost and maximize the exergetic efficiency. Furthermore, multi-objective optimization by means of a genetic algorithm is carried out to obtain the optimal design performance. The CCHP system can gain an improvement by 9.17% for the exergetic efficiency and a decrement by 5.05% for the total product unit cost compared with the stand-alone sCO2 system under the optimal condition.

A new technique for optimising of a PEMFC based CCHP system

A multi-criteria assessment of a hybrid proton exchange membrane fuel cell (PEMFC) based combined cooling, heating, and power (CCHP) system has been analysed. The assessment has been performed in terms of environment, thermodynamics, and economics point of view. The system includes an absorption chiller, a heat recovery system, a humidifier, a gas compressor, and a 5 kW PEMFC stack. To achieve optimal efficiency for the studied system, a developed model of the rhino herd (RH) optimisation algorithm has been proposed. Simulation results are applied to analyse the system in terms of annual cost, pollutant emission reduction, and energy and exergy efficiencies. The results demonstrated that using the proposed method gives lower annual GHG emission reduction. In addition, the method gives high energy and exergy efficiency, the pressure of inlet gases, and relative humidity. The final results are compared with the standard RH algorithm and NSGA-II to show the method of superiority.

Technical and economic evaluations of combined cooling, heating and power (CCHP) system with gas engine in commercial cold storages

In this paper, a combined cooling, heating and power (CCHP) system with gas engine is used to provide energy demand of a commercial cold storage and its techno-economic evaluation is performed compared to the traditional systems. Also, a cold storage facility to store orange crop during the period of entry and storage is analyzed. The thermal loads of the cold storage are calculated and an appropriate water-ammonia absorption chiller is designed and optimized. Then, changes in the energy and economic parameters are analyzed versus the main effective parameters. The results show that the use of this CCHP system under a heat supplying strategy with the possibility of selling electricity to the network, leads to reductions of fuel consumption and system operating costs about 78.85% and 81.34% compared to the conventional systems, respectively. Also, the payback periods by considering the interest rate and without it are determined 4.075 and 2.701 years, respectively. Also, according to the results obtained and the study of the ratio of fuel to power, the best operating point of the system from technical and economic viewpoints is achieved at a fraction of 80% load and the overall efficiency of the system is evaluated about 89.59%.

Performance analysis on a novel micro-scale combined cooling, heating and power (CCHP) system for domestic utilization driven by biomass energy

The CCHP system driven by biomass energy is essential for mitigating the fossil energy crisis and reducing CO2 emission. But few research work focuses on the micro-scale system due to the limited efficiency. In this paper an efficient household CCHP system is designed, which is driven by the water steam (100 °C-120 °C) from the biomass boiler and is consisted of an R245fa power cycle with a gravity assisted thermal driven “pump”, a single-pressure R134a/DMF/He diffusion absorption refrigeration cycle, and several heat exchangers for heating supply. The models of the system are constructed, and the energy, economic and environmental indexes are evaluated. The results reveal that the higher temperature of heat source and the lower temperature of ambient could improve the thermal efficiency of the CCHP system, and realize the lower cost and CO2 emission. The highest thermal efficiency of the CCHP system can reach to 55.26%. The quarterly energy saving for summer of a 100 m2 isolated house of a rural family can reach to 5059 kW⋅h (497 kW⋅h for cooling, 3154 kW⋅h for heating and 1408 kW⋅h for power generation), which can save about 3121.40 RMB electricity bill and reduce 0.15 t CO2 emissions.

Integrated adsorption-based multigeneration systems: A critical review and future trends

This paper presents the state-of-the-art of the integration of adsorption chillers into different configurations of combined cooling, heating, and power (CCHP) systems. Adsorption chillers, as a thermally-activated cooling system, provide a great solution to the utilization of low-temperature waste heat, thus help to increase the efficiency of the existing power generating systems, and to reduce the greenhouse gasses emissions including the chlorofluorocarbons (CFC) that is used in traditional electric-powered chillers. In this study, a brief introduction to CCHP systems and the thermally-driven cooling systems is presented, and the working scheme of the adsorption cooling cycle is illustrated. The paper also focuses on the CCHP systems integrated with adsorption chillers that are driven by solar thermal energy via different solar collectors. Furthermore, multigeneration systems driven by internal combustion engines, gas turbines and fuel cells are highlighted. Finally, the integration of adsorption chillers in hybrid cooling systems and with Organic Rankine Cycles (ORC) is also presented.

Day-ahead energy management and feeder reconfiguration for microgrids with CCHP and energy storage systems

Abstract Energy management featuring distribution feeder reconfiguration (DFR) and reactive power control, improves the technical and economic efficiency of microgrids. The present work proposes a framework that leverages scenarios to jointly manage the real and reactive power dispatches of the controllable generation resources as well as the topology of the distribution feeder. Multiple operation measures are optimized including the operation cost, real power loss, the voltage stability index (VSI), and the greenhouse gas emissions of the microgrid. Hybrid Big Bang- Big Crunch (HBB-BC) algorithm is used to solve the formulated optimization problem. Non-dispatchable and dispatchable distributed generation units (DGs), as well as the battery and thermal energy storage systems (BESS and TESS), are considered as a hybrid energy system. Combined cooling, heating, and power (CCHP) units are considered as dispatchable DGs and wind and solar photovoltaic generations are considered as non-dispatchable DGs. The efficiency of the proposed model and solution algorithm is investigated using a 33-bus microgrid, and the simulation outcomes are discussed.

Technical and economic analyses of a combined cooling, heating and power system based on a hybrid microturbine (solar-gas) for a residential building

One of the ways to increase the efficiency of energy conversion and reduce the generation of pollutants in the building sector is using combined cooling, heating and power (CCHP) systems. These systems have different types of prime movers such as micro gas turbine (MGT). In this study, a novel CCHP system based on the prime mover of hybrid solar micro turbine have been simulated and the annual performance of the cycle, in actual conditions has been evaluated for a residential building in Iran. By adding solar receiver to available micro gas turbines, solar energy can provide part of the required cycle heat. The components of this cycle include: micro gas turbine, solar dishes (parabolic dishes), solar receiver, absorption chiller, auxiliary boiler, and heat recovery steam generator. The effects of changing the number of micro turbines and the area of the parabolic dishes have been studied on system performance. Also, the levelized cost of electricity (LCoE) is calculated in different prices and the best scenario is proposed. Additionally, the appropriate economic conditions are introduced and some of their technical specifications are evaluated. Ultimately, the LCoE produced by this cycle is compared to that for the photovoltaic systems.

Multi-Objective Optimal Configuration of the CCHP System

The combined cooling, heating and power (CCHP) system not only has high energy efficiency but also has different load structures. Traditional separate production (SP) system and power supply system do not consider the land cost in terms of the environmental benefits, and in the aspect of the power supply reliability, the grid-connected inverter cost is also ignored. Considering the deficiency of the traditional energy supply system, this paper builds the CCHP system construction cost model. The particle swarm optimization (PSO) is adopted to find out the minimum value of the construction cost, and the optimal system construction scheme is constructed from three aspects which are system reliability, economic benefits and environmental benefits. In this paper, the typical daily data, as well as the meteorological data and the load data, in the last four years are taken as experimental dataset. The experimental results show that compared with the traditional SP system and power supply system, the CCHP system established in this paper not only achieves lower cumulative investment cost, but also has a good power supply reliability and environmental benefits.

Conventional and advanced exergoeconomic assessments of a CCHP and MED system based on solid oxide fuel cell and micro gas turbine

This paper presents an assessment of a combined cooling, heating and power (CCHP) and multi-effect desalination (MED) system based on SOFC/MGT by conventional and advanced exergoeconomic analyses. The conventional exergy analysis can reveal the sources of irreversibility in the system. The largest exergy destruction occurs in after burner followed by SOFC and MED, accounting for 20.079%, 12.986%, 12.907%, respectively. In the advanced analysis, the exergy destruction, exergy destruction cost and investment cost are split into avoidable/unavoidable and endogenous/exogenous parts to investigate the real potentials of exergy and economic performances. The advanced analysis results indicate that the major exergy destructions of most components are endogenous parts with inverter, MGT and air compressor owning the most potentials to reduce exergy destructions. The modified exergy efficiency of each component in the advanced analysis is higher than the conventional one. Finally, three possible strategies are suggested to reduce the avoidable exergy destruction cost rates.

Study on the optimization and sensitivity analysis of CCHP systems for industrial park facilities

In this paper, a comprehensive method is proposed to synergistically optimize the configuration and operation strategy of combined cooling, heating and power (CCHP) systems, considering configuration and strategy interact with each other. The mathematical model is established based on the energy flow and the energy balance relationship of CCHP system and traditional separate (SP) system with multi-objective evaluation criterion. The optimization based on an industrial park in Shanxi is carried out to find the optimal configuration and corresponding strategy. The results show that the optimized CCHP system outperforms the SP system in cost saving, energy consumption saving and CO2 emission reduction with the saving ratio of 17.37%, 33.72% and 55.76% respectively throughout the year. An analysis of the factors that affect the performance of CCHP systems is adopted in terms of: (1) price of electricity and gas; (2) the ratio of thermal load to waste heat; and (3) load rate of gas turbine. This paper may provide some new ideas for the optimization and performance improvement of CCHP systems.

Performance of gas turbine multi generation system regulated with compressor bypass extraction air energy storage

In aim to improve system efficiency and flexibility at deep peak-load operation, a novel supply-side load regulation strategy was proposed for gas turbine-based CCHP (combined cooling, heating and power) systems, where the load was regulated through compressor bypass air extraction (CBAE) for energy storage in addition to inlet guide vane (IGV) regulation strategy. The part-load performance of gas turbine with CBAE was studied and compared with the performance under IGV regulation strategy; as well, the supply-demand coupling performance of the proposed CCHP system was investigated in three different scenarios of demand-side load distributions. Taking maximum overall energy efficiency as the optimization target, the design capacity of the proposed system was optimized and analyzed. The analysis indicates that, gas turbine part-load power efficiency under CBAE regulation is inferior to that under IGV regulation, whereas the former ensures gas turbine a higher capacity of power and heating than the latter. CBAE regulation strategy greatly improves heat-power ratio and enhances load adaptability. The case study shows that at a higher heat-power ratio, the overall energy efficiency of the proposed system is 1.75% greater, while the optimal capacity of gas turbine is 8.64% lower than that of the reference one.

Multi-objective optimization and selection of hybrid combined cooling, heating and power systems considering operational flexibility

This paper proposes a multi-objective optimization model integrated with operational flexibility to optimize a hybrid combined cooling, heating and power (CCHP) system. The operational flexibility of the hybrid CCHP system is proposed and expressed by the combined indicators to show the capacity to resist performance degradation because of externally variable conditions to increase energy saving and cost saving, to reduce carbon dioxide emissions, and to enhance renewability, the ability to adjust heat and electricity, and the grid integration level. A Pareto frontier of solutions considering a larger operational flexibility with less performance degradation is obtained in genetic algorithm. The use of a multi-criteria decision making method combined with an entropy weighting method is employed to quantitatively evaluate the composite sustainability index of the Pareto schemes and choose the optimal hybrid CCHP option with the best integrated performance. The results of a case study that considers operational flexibility and optimization indicated that the potential adjustable ability was increased by 438.9%, and the grid integration level and net interaction with the grid were decreased by 3.6%. However, the increase in flexibility reduces the energetic, economic and environmental benefits achieved by the CCHP system by 5.1%, 56.4% and 3.0%, respectively.

Collaborative Optimization of Multi-Energy Complementary Combined Cooling, Heating, and Power Systems Considering Schedulable Loads

Combined cooling, heating, and power (CCHP) systems are a promising energy-efficient and environment-friendly technology. However, their performance in terms of energy, economy, and environment factors depends on the operation strategy. This paper proposes a multi-energy complementary CCHP system integrating renewable energy sources and schedulable heating, cooling, and electrical loads. The system uses schedulable loads instead of energy storage, at the same time, a collaborative optimization scheduling strategy, which integrates energy supply and load demand into a unified optimization framework to achieve the optimal system performance, is presented. Schedulable cooling and heating load models are formulated using the relationship between indoor and outdoor house temperatures. A genetic algorithm is employed to optimize the overall performance of energy, economy, and environment factors and obtain optimal day-ahead scheduling scheme. Case studies are conducted to verify the efficiency of the proposed method. Compared with a system involving thermal energy storage and demand response (DR), the proposed method exhibits a higher primary energy saving rate, greenhouse gas emission reduction rate, and operation costs saving rate of 7.44%, 6.59%, and 4.73%, respectively, for a typical summer day, thereby demonstrating the feasibility and superiority of the proposed approach.

A new optimized configuration for capacity and operation improvement of CCHP system based on developed owl search algorithm

One of the best ways to optimally consuming fossil fuel thermal energy is to utilize combined cooling, heating, and power (CCHP) systems. In such systems, by recycling heat wasted from hot gases simultaneously generating power, heat, and refrigeration from combustion, as well as water and cooling oil in electricity production systems, the overall system energy utilization efficiency can be increased to more than 85%. Analysis and optimization of the CCHP systems are mostly in accordance to the operating cost reduction without considering the emissions reduction and actual energy utilization. The present study proposes an energy flow for CCHP system to decrease the main power consumption based on a building thermal demand in Kerman area, Iran. The method introduced a developed version of the owl search algorithm to increase the efficiency of the CCHP system in comparison with the separation production system. Final simulations declare well efficient results for the presented method.

A Two-Stage Industrial Load Forecasting Scheme for Day-Ahead Combined Cooling, Heating and Power Scheduling

Smart grid systems, which have gained much attention due to its ability to reduce operation and management costs of power systems, consist of diverse components including energy storage, renewable energy, and combined cooling, heating and power (CCHP) systems. The CCHP has been investigated to reduce energy costs by using the thermal energy generated during the power generation process. For efficient utilization of CCHP and numerous power generation systems, accurate short-term load forecasting (STLF) is necessary. So far, even though many single algorithm-based STLF models have been proposed, they showed limited success in terms of applicability and coverage. This problem can be alleviated by combining such single algorithm-based models in ways that take advantage of their strengths. In this paper, we propose a novel two-stage STLF scheme; extreme gradient boosting and random forest models are executed in the first stage, and deep neural networks are executed in the second stage to combine them. To show the effectiveness of our proposed scheme, we compare our model with other popular single algorithm-based forecasting models and then show how much electric charges can be saved by operating CCHP based on the schedules made by the economic analysis on the predicted electric loads.

Novel geothermal driven CCHP systems integrating ejector transcritical CO2 and Rankine cycles: Thermodynamic modeling and parametric study

With recent technical advances, Combined Cooling, Heating and Power (CCHP) system offers a practical and economical alternative to conventional energy conversion systems. Benefits of these systems are more marked with employing efficient thermodynamic cycle and using renewable energy resources. In this regard in the present work, a novel geothermal driven CCHP system, in which the ejector transcritical CO2 cycle is integrated with conventional Rankine cycle, is proposed (system a). The proposed system is then modified by replacing the gas cooler with an internal heat exchanger to make a more efficient CCHP system (system b). To investigate the first and second law performance of the proposed systems, thermodynamic models are developed and parametric analysis is carried out to examine the influences of design variables. The results indicated that, the gas cooler of conventional system can be replaced by an internal heat exchanger for a wide range of practical operating conditions and this replacement can improve the exergy efficiency, net output power and output cooling respectively by 30.9%, 49.1% and 75.8% at the expense of 39.1% reduction in heating output. Also a comparison is made between the two proposed systems in this work with similar systems (based on ejector transcritical CO2 cycle) proposed previously by other researchers and superiority of proposed systems in this paper is revealed and discussed.

Exergy and exergoeconimic analysis and multi-criteria optimisation of 1 MW installed CCHP system (a case study in Kashan University)

The present study deals with exergy and exergo-economic evaluation of a 1 MW combined cooling, heat and power (CCHP) system, composed of a natural gas prime mover internal combustion engine located in the main campus of the University of Kashan, Kashan, Iran. Using appropriate linking between engineering equation solver (EES) and MATLAB software, thermal and economic modelling and multi-criteria optimisation (MCO) have been performed. The optimisation results showed that the minimum total exergy destruction rate occurs for the exhaust gas extraction factor of 0.68, which causes $33.52/h total cost rate. For this case, among all of the system components the highest exergy destruction rate of 1,700 kW belongs to the engine. In addition, the results of the genetic algorithm-based multi-objective optimisation represented that the optimisation causes $2.68/h decrease in total cost rate and reduction of 4,512 kW in exergy destruction rate.

Proposal and performance comparison of various solar-driven novel combined cooling, heating and power system topologies

In the present research work, three novel topologies (Configuration-1, Configuration-2 and Configuration-3) of solar energy driven combined cooling, heating and power (CCHP) system are proposed to identify eco-friendly system for future energy demand and human comfort. The proposed CCHP systems consist of solar thermal evacuated U-tube collector, organic Rankine cycle for power, ejector refrigeration cycle for cooling and heat exchanger for heating. Through theoretical analysis, the thermodynamic (energy and exergy) performances of all three configurations are investigated by utilizing solar energy and compared by estimating the objective functions like performance index, irreversibility, exergy efficiency, net work output, heating output, entrainment ratio and cooling output. The objective functions are analyzed on the basis of generator temperature, evaporator temperature, condenser temperature and solar intensity as decision variables. The practical feasibility of the proposed systems is discussed as well. It is revealed that configuration-1 has maximum overall exergy efficiency and power output while configuration-3 has maximum performance index and heating output as compared to other configurations. Configuration-2 has maximum cooling output as compared to other configurations. In overall, Configuration-3 is best considering higher energy performance, lower number of components (compactness), wider operating range and energy demand flexibility while other configurations also have their merits.

Optimized scheduling of multi-region Gas and Power Complementary system considering tiered gas tariff

Integrated Energy System (IES) based on Combined Cooling, Heating and Power (CCHP) technology has been proved as an efficient approach, which can resolve energy and environment issues and meanwhile bring economic benefits. For areas with fragile grid infrastructure and abundant oil, gas and renewable resources, various types of energy sources can complement each other and be cooperated as a unity, by operating the energy networks across regions as a single IES through the implementation of multi-region Gas and Power Complementary (GPC) system. Conventionally, the typical optimized scheduling of GPC system does not consider the complementarity among areas with diverse device and load characteristics. Since changes and developments have occurred in power-to-gas conversion technologies and intra-regional CCHP system, traditional models need to be updated and improved along with the application of tiered gas price. Based on the existing coupled power-gas flow scheduling model, this paper proposed a multi-region optimized scheduling model where the CCHP systems operated inside a region and power-gas complementarity could be achieved among multiple regions. Mixed Integer Linear Programming (MILP) was used to obtain the optimal solution of this scheduling model. The compressor linearization model was designed in order to describe transmission loss of the gas network and perfect the power-gas flow model as well. Results of cases proved that considerable environmental benefits could be achieved when Combined Heating and Power (CHP) equipment was introduced in the multi-region GPC system. Finally, combined with the tiered gas tariff, the total operation cost of regions could be reduced and the day-ahead economic optimized scheduling could be improved. It also showed that the operating parameters in each region expressed different sensitivity to gas price due to the flow constraints. Moreover, compared with battery energy storage systems, power-to-gas conversion technology would be more prospective because it could significantly boost the system operating efficiency.