Primary Energy Saving Ratio Research Articles

Development and performance evaluation of a high solar contribution resorption-compression cascade heat pump for cold climates

Absorption-resorption heat pumps (ARHPs) have great potential in utilizing low-temperature solar heat for efficient winter heating, but are limited by their weak adaptability to cold climates relative to absorption heat pumps (AHPs) and vapor compression heat pumps (VCHPs). In this work, a resorption-compression cascade system consisting of ARHP and VCHP subsystems is proposed and investigated, with the goal of achieving efficient winter heating with improved solar contribution in cold climates. Thermodynamic models of the two subsystems and of the whole cascade system are developed for system feasibility verification and performance evaluations. Feasible operation temperature and pressure conditions are identified in terms of internal subsystem matching. Based on these operation conditions, the primary energy ratio (PER) – which is a key performance evaluation index – is investigated over a range of solar fractions (f). The results show that for cases without solar contribution, the PER can be generally >0.95 under feasible operating conditions. In addition, the primary energy saving ratio (PESR) and heating capacity lift ratio (εlift), as well as the heat source temperature (Th) and ambient temperature (Tamb) restriction, are all investigated and compared to those of other, competing heating systems. The results show that the proposed system can reduce the Th demand to 69 °C (with a minimum Tamb of −21 °C) and extend the operational Tamb to −31 °C (with a minimum Th of 90 °C), while importantly achieving PESR > 0.20 and εlift > 20 % under the above extreme conditions. Moreover, when integrating the system with solar heat with f > 43 %, the proposed solar-assisted system has a clear PER advantage over an equivalent VCHP system in the Tamb range from −31 °C to 10 °C, highlighting the possibility of achieving higher solar contribution in cold climates.

Experimental and theoretical investigation on a novel solar-assisted absorption-resorption heat pump (ARHP) system towards clean heating

Among thermally-activated heat pumps, absorption-resorption heat pump (ARHP) is dominant by the ability of combining with low-temperature heat for efficient space heating. In this work, an ARHP experimental prototype is developed based on the previous thermodynamic cycle and tested to obtain the operation details such as coefficient of performance (COP), supply water temperature, heating capacity and so on. The experimental and the previous theoretical results are compared and mutually verified. The exact performance of the solar-assisted ARHP heating system is then investigated and compared with that of the conventional vapor compression heat pump (VCHP) in terms of primary energy ratio (PER) and primary energy saving ratio (PESR). The experimental results show that the COP increases greatly from 1.125 to 1.353 when the heat source temperature increases from 90 °C to 150 °C at the ambient temperature and return water temperature of 0 °C and 30 °C, respectively. Under given conditions, the measured heating capacity reaches a maximum value of 18.5 kW, 9.0 % lower than the rated value. The theoretical results reveal that solar fraction above 30 % can make PER of the solar-assisted ARHP heating system comprehensively greater than that of the reference VCHP system. Optimal solar contribution to space heating can be achieved based on the proposed ARHP if solar heat is dividedly utilized in its temperature zones of 10–35 °C, 35–83 °C and above 83 °C.

Multi-objective optimization of a hybrid energy system integrated with solar-wind-PEMFC and energy storage

The move towards achieving carbon neutrality has sparked interest in combining multiple energy sources to promote renewable penetration. This paper presents a proposition for a hybrid energy system that integrates solar, wind, electrolyzer, hydrogen storage, Proton Exchange Membrane Fuel Cell (PEMFC) and thermal storage to meet the electrical and heating demands of a student dormitory in Shanghai. The proposed system is optimized to simultaneously account for multiple objectives, including economy, environmental benefits, and grid interaction, measured by Equivalent Annual Cost (EAC) for the life cycle of 20 years, Primary Energy Saving Ratio (PESR) of the heating system and Grid Interaction Level (GIL) of the electrical system. The effectiveness of the optimization results from NSGA-II is verified and compared with MOPSO to determine the optimal installation configuration and operation strategies. The results highlight the significance of energy storage in enabling greater renewable integration and the potential of hydrogen to play a vital role in the transition to a low-carbon economy. The optimal design of the proposed hybrid system can meet the power and heat demand of a student dormitory with a floor area of 2679m2. The Pareto-optimal solutions of PESR and GIL for NSGA-II fall within the range of (89 %, 104 %) and (70 %, 88 %), respectively. A significant number of Pareto-optimal solutions cluster around an EAC of approximately 160 k RMB. The optimization by MOPSO exhibited the similar results. Additionally, the sensitivity analysis provides insights into the sensitivity of objectives to changes in optimal design parameters, facilitating the design and optimization of similar hybrid energy systems integrated with a closed loop for hydrogen production and utilization in the future.

Energy, exergy, and economic analysis of a solar photovoltaic and photothermal hybrid energy supply system for residential buildings

In this study, a dynamic simulation model is developed based on the mathematical model of a solar photovoltaic and photothermal hybrid energy supply system (PV-PTHS) employing the TRNSYS simulation software. The corresponding operational control strategy for the PV-PTHS is proposed. The impact of different PV and PT areas on the performance and the energy and exergy flows of the PV-PTHS throughout the year are analyzed using simulations. In addition, the dynamic performance of the PV-PTHS on typical days is reported during the heating period, transition period, and cooling period. Also, the monthly exergy performance of the system is comprehensively analyzed. Finally, the cost-effectiveness and energy savings of the PV-PTHS are reported and compared against the single PT and single PV systems. The results show that the energy loss of the PV cells is the highest, followed by the solar collector. However, the exergy efficiency of the collector is lower than that of the PV cell in the PV-PTHS, and the low exergy efficiency of the collector results in a lower exergy efficiency of the PT subsystem (PTS). Considering similar initial investments, the PV power supply ratio of the PV-PTHS is the highest in areas with a large heating load, such as Nagqu and Yinchuan. The heat supply ratio and the cost-effectiveness of the signal PT system are the best. Overall, the proposed PV-PTHS yields the highest primary energy saving ratio (PESR) and the best cost-effectiveness for areas with a small heating load, such as Wuhan and Fuzhou.

Energy and economic assessment of a hybrid solar/gas heating system using a combined statistical-based multi-objective optimization method

The hybrid solar/gas heating systems are considered as promising technologies to reduce energy consumption and ecological impact, for a more sustainable environment. However, the complexity related to the process of hybridization often calls for multi-objective optimization problems to deal with the constraining objectives. In this paper, a multi-objective optimization methodology combining genetic algorithm, design of experiments and dynamic simulations is proposed. The present work is carried out to maximize the primary energy saving ratio (PESR), solar fraction (SF) and to minimize the levelized cost of heat of a hybrid solar/gas heating system intended for an office building located in Algiers, Algeria. The performance analysis of three control strategy modes showed how important the control strategies can improve the SF and the PESR. The suggested control mode demonstrated a seasonal SF and PESR of 40.31% and 31.32%, respectively. The proposed multi-objective optimization approach gave a better comprehensive energy and economic performance by identifying the pareto fronts. The Linear Programming Technique for Multidimensional Analysis of Preference decision-making technique was employed to determine the best optimal solution. The optimized system exhibited SF of 72.65%, PESR of 42.07% and the Levelized Cost of Heat of 0.054 $/kWh as per the design parameters, collector area of 10 m2, tank volume of 1.7 m3 and a flow rate of 0.2 kg s−1. Overall, the results showed that the proposed methodology is time-efficient and can be applied to optimize hybrid solar/gas systems.

Multi-criteria optimization of a biomass gasification-based combined cooling, heating, and power system integrated with an organic Rankine cycle in different climate zones in China

In this work, a multi-criteria optimization on a biomass gasification-based combined cooling, heating, and power system integrated with an organic Rankine cycle (ORC) is conducted. The ORC module is driven by the waste heat of the power generation unit. The criteria for the optimization comprise primary energy saving ratio (PESR), total cost saving ratio (TCSR), and CO2 reduction saving ratio (CERR). A criterion based on Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) is employed as the evaluation basis of the multi-criteria optimization. The improvement caused by ORC integration and multi-criteria optimization is investigated by comparing with the systems without the former and/or the latter one. Through case studies of a hypothetical hotel building located in six different climate zones in China, it is found that after the integration of an ORC module and multi-criteria optimization, the annual PESR, TCSR, and CERR are varied from 4.8%/−2.2%/7.0% to 8.4%/ 3.5%/12.0%, respectively, in different climate zones. The parameters of biomass and grid electricity, which are both location-related, have decisive effect on the system performance and the optimization results. Comparing with integration of an ORC module, the multi-criteria optimization has larger improvement of PESR when cooling demand is low, of TCSR when thermal demand is low, and of CERR in all the studied load conditions.

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.

Energy, exergy and exergoeconomic analysis of a combined cooling, desalination and power system

Ocean thermal energy has attracted much attention for its unique advantages. Multi-generation systems are emerging as an effective solution to further improve energy efficiency and economy of ocean thermal energy conversion (OTEC) system. In this paper, a novel hybrid OTEC system combing cooling, desalination and power (CCDP) is proposed facing the actual demands of remote islands at low latitudes. The cogeneration of cooling capacity, fresh water and power are achieved by the subsystems of ejector refrigeration cycle (ERC), multi-effect distillation (MED) desalination and organic Rankine cycle (ORC). A detailed mathematical model for the proposed system is developed based on the thermodynamics and exergoeconomics. The effects of key operating parameters on the system performances are investigated from the perspectives of energy, exergy and exergoeconomic. The results indicate that the highest primary energy saving ratio (PESR) and exergy efficiency of the proposed system are up to 33.72% and 29.33%, respectively. The main sources of exergy destruction are the MED unit, generator and ejector, accounting for about 80% of the total exergy destruction. The improvement of both thermodynamic and exergoeconomic performances can be achieved at a higher generation pressure and a larger distillate production. The rise of condensing pressure is conducive to cutting down the unit costs of products, but will result in lower exergy efficiency and PESR.

Proposal and performance analysis of a novel solar-assisted resorption-subcooled compression hybrid heat pump system for space heating in cold climate condition

Absorption-resorption heat pumps (ARHPs) can efficiently utilize low-temperature solar heat for winter space heating, but are restricted by the relatively weak low ambient temperature adaptability. By combining the different strengthens of vapor compression heat pump (VCHP) and absorption-resorption heat pump (ARHP), a novel solar-assisted resorption-subcooled compression hybrid heat pump system with higher heating capacity under cold climate condition for space heating is proposed. Thermodynamic models for the hybrid system involving two subsystems are developed for performance evaluation under different operation conditions. Feasible high pressure/low pressure (PH/PL) and evaporation temperature/condensation temperature (Te/Ta) ranges for the hybrid system are revealed for component design. Based on that, performance evaluation indices like total coefficient of performance (COPtot), primary energy ratio (PER), primary energy saving ratio (PESR), coefficient from solar irradiation to heating capacity (SCOP) are investigated in terms of different PH/PL and Te/Ta values. The results showed that for the base-case, the above indices are 2.41, 1.66, 0.35 and 1.21, respectively. In addition, heat source temperature demand, heating capacity and ambient air temperature need of the hybrid system are compared with those of the conventional absorption heat pump (AHP), single ARHP and single VCHP under the same operation conditions. The results show that the hybrid system can extend the operation heat source temperature to above 72 °C, highlighting the possibility of integrating with common non-tracking solar collectors, and can extend the feasible ambient air temperature to above −20 °C. Moreover, by recovering the sub-cooling heat of VCHP subsystem for ARHP subsystem operation, the hybrid system can lift the heating capacity by over 50% based on the equivalent VCHP system.

Energy, exergy and environmental analysis of a hybrid combined cooling heating and power system integrated with compound parabolic concentrated-photovoltaic thermal solar collectors

The objective of this paper is to propose and analyze the performance of a novel hybrid combined cooling heating and power (CCHP) system coupled with compound parabolic concentrator-photovoltaic thermal (CPC-PVT) collectors. The electricity and hot water from CPC-PVT are integrated with the electricity and waste heat carried by exhaust gas and jacket water from the internal combustion engine to improve the energy performance. The thermodynamic models were constructed and validated by comparing the simulation results to those from existing studies. The thermodynamic performances were analyzed and the impacts of key parameters on the performances were discussed at the off-design condition. The levelized primary energy saving ratio (PESR) and carbon dioxide emission reduction ratio (CDERR) of the hybrid CCHP system in comparison to the CCHP system without solar energy were employed to evaluate the contribution of solar energy. The results indicated that the energy and exergy efficiencies at the design condition are 63.3% and 21.8% in summer, respectively, and 61.8% and 27.1% in winter, respectively. Compared to the CCHP system without solar energy, the hybrid system has more flexible ability to adjust the heating to electricity ratio and achieves the maximum levelized PESR of 28.6% and CDERR of 36.7%, respectively.

Multi-objective optimal analysis on the distributed energy system with solar driven metal oxide redox cycle based fuel production

Solar energy driven cerium dioxide (CeO2) thermochemical cycle based fuel production is considered to be a promising technology that can integrate with a combined cooling, heating and power (CCHP) system owing to the pollution free property and favorable chemical reaction kinetics characteristics. In this study a combined cooling, heating, power and fuel (CCHPF) distributed energy system is devised to improve the energy utilization efficiency and reduce the dependence on conventional fossil fuels. To realize the efficient and cost-effectively operations of the system, a constrained multi-objective optimization problem with aims of maximizing primary energy saving ratio (PESR) and minimizing CO2 emission and energy cost is proposed to search for the optimal operation strategy and schedule. A potent optimization method that capitalizes on the advantages of the non-dominated sorting genetic algorithm-II (NSGA-II) and the random walk with directional exploitation (RWDE) algorithm is developed to solve the proposed optimization problem more effectively. The fuzzy decision making method is tailored to determine the final operation strategies of the CCHPF system from the obtained Pareto front according to the decision maker preferences. Numerical results show that the proposed system realizes the supply-demand balance, the optimal dispatch of the energy and the efficient economic operation. In comparison with existing CCHP systems, the energy utilization efficiency of the developed CCHPF system increases by 0.60% and 17.65%, CO2 emission decreases by 13.79% and 3.77%, as well as economic cost reduces 0.29% and 6.33% on a typical winter and summer days, respectively. The research findings provide new insights for improving the coordinated operation of distributed renewable energy system and alleviating energy crisis and environmental pollution.

Performance analysis of a combined power and refrigeration cycle

In this paper a novel combined power and refrigeration cycle is proposed based on the ocean thermal energy conversion (OTEC) system, i.e. the Kalina cycle. In this combined cycle, solar energy is employed to raise the heat source temperature. Cooling capacity is generated concurrently by the ejector refrigeration cycle (ERC) which works on the exhaust heat extracted from the turbine in the Kalina cycle. Ammonia-water and isobutane are selected as the working fluid of Kalina cycle and ERC respectively. To evaluate the performance of the proposed cycle, the process is simulated in the commercial package ASPEN PLUS. It is found that, compared with the Kalina cycle, the proposed cycle has a higher primary energy ratio (PER) of 29.2% though it has a lower power output. Besides, the exergy efficiency and the primary energy saving ratio (PESR) in the proposed cycle reach as high as 41.88% and 8.3% respectively. It is also demonstrated that when the inlet pressure of the turbine exceeds 2.9 MPa and the outlet pressure of the turbine is between 1.3 and 1.6 MPa in the test range, the proposed cycle is better than the stand-alone systems from the energy saving perspective. Furthermore, parametric analysis shows that the inlet and outlet pressure of the turbine, the inlet temperature of the turbine, the basic concentration of ammonia-water, the generation pressure, ejector entrainment ratio and the outlet temperature of the condenser II have significant effects on the output of the turbine, refrigeration output, exergy efficiency, COP, PER as well as PESR.

Multi-criteria optimization for a biomass gasification-integrated combined cooling, heating, and power system based on life-cycle assessment

A multi-criteria optimization for a biomass gasification-integrated combined cooling, heating, and power (CCHP) system based on life-cycle assessment is carried out. The criteria comprise primary energy saving ratio (PESR), total cost saving ratio (TCSR), and CO2 emission reduction ratio (CERR). The overall-performance criterion, Cl, is obtained with Technique for Order of Preference by Similarity to Ideal Solutions (TOPSIS). Results show that the Cl reaches its maximum when the nominal electric output is 1572.8 kW, the biomass feedstock type is wood pellet, and the operation strategy is following the electric load (FEL). The PESR, TCSR, CERR, and Cl are 0.101, 0.271, 0.498, and 0.867, respectively. By comparing with reference systems, it is found that in FEL mode, the system is improved because of higher energy utilization efficiency and better use of economic and environmental advantages of biomass. In following the thermal load (FTL) mode, economic performance is compromised for optimal overall performance. Sensitivity analysis is carried out to find out the effect of variation of various parameters on optimization results. It is found that the variation of a single-aspect parameter could affect the system performance on all aspects. The variation of primary energy consumption per unit electricity from the grid (pecen,g) has the greatest effect on optimization results. The corresponding variation ranges of PESR, TCSR, and CERR owing to its variation are from −0.063/0.231/0.473 to 0.284/0.295/0.624 and from −0.029/0.101/0.314 to 0.194/0.123/0.379 in FEL and FTL modes.

Optimizing the insulation thickness of walls and roofs of existing buildings based on primary energy consumption, global cost and pollutant emissions

An optimization model used to determine the optimum insulation thickness (OIT) of walls and roofs of existing buildings was established. Primary energy saving ratio (PESR), global cost saving ratio (GCSR) and pollutant emission reduction ratio (PERR) were used as evaluation criteria. Least square method was used to fit the polynomials which indicated the relationship between annual air-conditioning demand and insulation thickness. An existing building was used as the basis of the case study. The average relative error on annual heating and cooling demand was 0.23% and 0.035%, respectively, which indicated the accuracy of both fitting polynomials. Four types of heat and cold sources were considered to be used for the case building, respectively. Sensitivity analysis was carried out to investigate the impact of economic and energy factors on the optimization results. Results showed that the OIT of walls and roofs could be obtained by using the optimization model. The OIT of walls and roofs, building performance indicators and overall evaluation criterion during building envelope retrofit depended on the weight coefficients of evaluation criteria and types of heat and cold sources. The impact of sensitivity factors on the optimization results for the four types of heat and cold sources were different.

Assessment of a novel heat-driven cycle to produce shaft power and refrigeration

This paper proposes a novel combined cooling and power (CCHP) system based on a composition of a Rankine, gas refrigeration (reverse Brayton), liquid desiccant, ejector, and evaporative cooling cycles. The two proposed configurations, called the original cycle (OC) and the enhanced cycle (EC), utilize heat rejected by the Rankine cycle via its condenser in order to regenerate the liquid desiccant cycle. The desiccant cycle allows the cooling systems to decouple sensible and latent loads, and potentially reduce water consumption relative to pure evaporative cooling. Based on our thermodynamic calculations, the OC and EC are more feasible from an energy-saving viewpoint compared with separate systems that provide the same services for sensible heat ratios (SHR) less than 14% and 39%, respectively. At a fixed heat source input of about 2.4 MWth at 210 °C, the OC is capable of generating 103 kWe of electrical power, 181 kWth of sensible cooling, 1631 kWth of latent cooling capacity, and fresh water at 2.7 m3/h capacity. At a SHR of 10%, the OC can achieve an exergy efficiency and primary energy saving ratio (PESR) of 24% and 28%, respectively. Similarly, and at the same thermal energy input, the EC can supply 354 kWe, 400 kWth, and 1199 kWth, and 1.8 m3/h of electrical power, sensible cooling capacity, latent cooling capacity, and fresh water capacity, respectively, at a SHR of 25%. Furthermore, the EC is more efficient than both the OC and stand-alone conventional systems as it shows a higher exergy efficiency of 53% and PESR of 29%.

A comparison of battery and phase change coolth storage in a PV cooling system under different climates

Energy storage in PV cooling systems is desirable to supply on-site loads during solar outages. Current storage methods of such systems typically use battery storage to store surplus electricity generated by solar panels or coolth thermal energy storage (CTES) to store excess cooling capacity produced by an electric-driven chiller. This study compares three cooling system configurations – no energy storage, with a battery storage, and with a phase change CTES, for a residential building under the climate of Shanghai, Madrid and Brisbane. System simulation of each configuration was conducted using TRNSYS. A CTES component was programmed externally using effectiveness-NTU method. Both energy storage methods were compared with regard to energy change during a summer day, power consumption and primary energy saving ratio (PESR) during the cooling season. In addition, performance of a single battery and a single CTES were evaluated under various operational conditions. The results showed good energy performance of both storage cases. The PESR of battery case and coolth storage case were 2.8 times and 1.9 times higher than that of a reference case with no energy storage.

Energy and exergy analysis of novel combined cooling and power (CCP) cycles

This paper presents energy and exergy analyses of the basic combined cooling and power (BCCP) cycle as well as three modified CCP cycles. These modified CCP cycles are brought together by an appropriate combination of the organic Rankine cycles (ORCs) and ejector refrigeration cycle (ERC) to produce power and refrigeration, simultaneously. The performance of different working fluids for each CCP cycle is investigated using isobutane as a fixed working fluid of the ERC and R123, R245fa, and isobutane as working fluids of the ORCs. Energy and exergy analyses are conducted showing that the thermal efficiency, primary energy saving ratio (PESR), exergy efficiency, and overall exergy destruction ratio can be improved by 24.5, 134, 72, and 32% throughout the presented state-of-art modification as well as working fluid selection, respectively. Thus, selection of R123/isobutane as working fluid and CCP cycle incorporating both recuperation and turbine bleeding as cogeneration system are the most appropriate selection from thermodynamics and environment viewpoints. Moreover, exergy analysis demonstrated that the generator accounts for the major losses in the overall exergy destruction between all components. At the end, parametric study is conducted to examine the effects of different key thermodynamic parameters on performance of different cycles. It is shown that one can obtain a higher PESR by increasing of the generator pressure and ejector mass entrainment ratio or by decreasing of the evaporator pressure and condenser temperature. It is also found that increasing of the generator pressure and ejector mass entrainment ratio or decreasing of the evaporator pressure and condenser temperature will increase the thermal efficiency. Moreover, a higher exergy efficiency can also be obtained by increasing of the generator pressure as well as the ejector mass entrainment ratio.

Thermodynamic and environmental evaluation of biomass and coal co-fuelled gasification chemical looping combustion with CO2 capture for combined cooling, heating and power production

This work presents a detailed investigation of biomass and coal co-fuelled gasification chemical looping combustion for combined cooling, heating and power (BCCLC-CCHP) generation system from both thermodynamic and environmental aspects. Addition of biomass (corn stover) as blending fuel not only provides possibility of utilizing renewable energy, but also greatly reduces greenhouse gas emissions. The application of chemical looping combustion for oxidation of syngas is aimed at inherent separation of CO2 without extra energy penalty. At based design conditions, the energy efficiency and exergy efficiency can reach 60.16% and 22.16% in summer, respectively. Three key parameters, namely oxygen to carbon ratio (O/C), operating temperature of air reactor in the chemical looping combustion and share of corn, are considered to analyze their influences on system performances. O/C ratio is not sensitive to energy output, however an optimum value of O/C=0.42 is found to obtain maximum system efficiency and primary energy saving ratio (PESR). Increasing AR operating temperature benefits power generation but lowers down cooling and heating production. Increasing corn mass share from absence to 50wt.% to replace part of coal results in energy efficiency losses by approximately 6 point percentages but the PESR is increased by up to 5 point percentages. Capture of photosynthetically-derived CO2 (from corn) by CLC offers negatively cradle-to-grave greenhouse gas emissions in the BCCLC-CCHP process when corn mass share is higher than 15%.

GA/AHP-based optimal design of a hybrid CCHP system considering economy, energy and emission

Integration of CCHP systems into large buildings provides considerable advantages, as far as the economy, energy consumption and environment related issues are concerned. In this paper, the integration of a hybrid CCHP system into a commercial building is studied. The hybrid CCHP system consists of a renewable and a non-renewable CHP component, photovoltaic/thermal (PV/T) panels and internal combustion engine (ICE). Three objective functions are considered based on cost saving, energy saving and emission reduction goals where are determined as annual operating cost ratio (AOCR), primary energy saving ratio (PESR) and carbon emission reduction ratio (CERR). Considering each objective function, the GA optimization is applied in three different approaches as a single objective optimization problem to find the best size of the system components. Then, using Analytic Hierarchy Process (AHP), which is one of the most used Multi-Criteria Decision Making (MCDM) procedures, the most profitable answer is determined from the three answers achieved in the optimization process.The results showed a good performance of the system. In PESR optimization, which is selected as the best system size, values of 32.96%, 17.25% and 14.79% was achieved for AOCR, PESR and CERR, respectively.

Pre-feasibility of building cooling heating and power system with thermal energy storage considering energy supply–demand mismatch

Natural-gas-driven building cooling heating and power (BCHP) system shows high energy efficiency and low greenhouse gases emission, but is of dissatisfactory performance under part load working conditions due to the non-synchronized and fluctuating thermal and electrical demands. Integrating thermal energy storage (TES) device with BCHP system proves to be an effective way to improve the performance of the whole system. In this paper, the applicability of TES–BCHP system is investigated according to the relationship between user load demands and system energy supply. Based on the supply thermal power ratio of the prime mover and the required one of users, a new parameter, the degree of mismatch (DM), is defined. Moreover, the analytical relationship between primary energy saving ratio (PESR) of TES–BCHP system and DM is established, under following thermal load (FTL) and following electrical load (FEL) respectively for three typical working conditions. The results show that the more DM approaches to unity, the higher PESR of TES–BCHP will be, and that the exportability of the co-generated electricity is favorable for energy saving. It also indicates that TES–BCHP is more applicable for those where the heating demand is dominant. This work is of great significance in further understanding the energy saving mechanism between TES and BCHP and guiding the design of practical TES–BCHP systems.