1,721,015 research outputs found
THERMODYNAMIC MODELING AND SIMULATION OF AN ORGANIC RANKINE CYCLE-EJECTOR HEAT PUMP-BASED TRIGENERATION SYSTEM USING A ZEOTROPIC MIXTURE
No full textTo solve the problem of low thermal efficiency of the organic Rankine cycle (ORC) and to enhance the coefficient of performance (COP) of ejector refrigeration cycle, an ORC combined with an ejector heat pump-based combined cooling, heat and power system using a zeotropic working fluid mixture is proposed in this paper. Utilization of zeotropic mixtures could improve the thermodynamic performance of ORC systems owing to superior fits of the temperature profiles of the working fluid and the heat source/sink. A thermodynamic model is built to predict the performance of the proposed trigeneration system using butane/propane zeotropic mixture. The model was validated with data obtained from the open literature. It was then applied to investigate and optimize the effect of a wide range of parameters on system performance. A detailed parametric analysis was then performed to assess the influence of generator temperature and entrainment ratio on the system's heating, cooling and power efficiencies, exergy and thermal efficiencies, and COP. The analysis also examined the effect of mass fraction on the system's power and cooling efficiencies. The results disclosed that for the zeotropic butane/propane mixture with mass fractions of 0.5/0.5, a generator temperature of 75°C and entrainment ratio of 0.5 produced a net power output of 136.3 kW, with a power efficiency of 4.6%, a heating efficiency of 95.4%, a cooling efficiency of 42.9%, and a COP of 1.43.With such thermodynamic analysis, the study demonstrated that the proposed system is feasible
Organic Rankine cycle-ejector heat pump hybrid system using low GWP zeotropic mixtures for trigeneration application
No full textThis paper presents a comprehensive study focused on improving the thermal efficiency and performance of an organic Rankine cycle (ORC) combined with an ejector heat pump (EHP) for trigeneration application. The utilization of zeotropic mixtures with low global warming potential (GWP) was proposed as a solution to address the inherent inefficiencies of the ORC at low-temperature heat sources and to enhance the coefficient of performance (COP) of the ejector refrigeration cycle. A thermodynamic model was developed to predict system performance, utilizing low-temperature heat sources such as solar or geothermal energy, along with zeotropic mixtures. The model was validated with the available literature data, demonstrating very good agreement. Five zeotropic fluid mixtures were preliminary studied, and the optimal mass fractions identified. Detailed investigations were then carried out for two of these mixtures, R1233zd(E)/propane and butane/propane, which exhibit low GWP and ozone depletion potential (ODP). The influence of generator temperature and entrainment ratio on system efficiency metrics, exergy, and COP were evaluated for these mixtures. Conclusions are drawn based on the two optimized zeotropic mixtures for maximum thermal efficiency. For R1233zd(E)/propane mixture with mass fractions 0.75/0.25 and butane/propane mixture with mass fractions 0.5/0.5 at generator temperature of 75 °C and entrainment ratio of 0.5, the systems achieved a heating capacity of 1607.9 kW and 2847.9 kW, a cooling capacity of 1037.5 kW and 1280.3 kW, and a net power output of 59.2 kW and 136.3 kW. Other related performance and efficiency parameters are included in the paper. These findings indicate the feasibility of utilizing these systems for trigeneration application. Additionally, a comparative analysis with a regenerative ORC highlighted the ORC-EHP hybrid system's advantages, including enhanced heating efficiency, cooling capacity, and overall COP. This research contributes valuable insights to advance the efficiency and sustainability of combined cooling, heat, and power systems, fostering the progression of innovative energy solutions
Internet of Things (IoT)-Based System for Smart Home Heating and Cooling Control
No full textCurrently 40% of all energy consumption comes from building services such as heating, ventilation and air cooling conditioning (HVAC) systems. To help reduce current energy consumption levels in this sector, many different tools are being investigated. One such tool is to use the Internet of Things (IoT) to target reducing wasted energy while heating and cooling buildings. This study examined an IoT-based system to control heating and cooling within the context of a Canadian residential housing. The building being simulated is one of the Canadian Centre for Housing Technology's house tested under the fall season. The simulation showed that the house could be kept in the desired comfort zone regardless of the outdoor environment. As well, the developed IoT system implemented in the simulation was able to accurately identify whether it should be heated or cooled, while not using both systems at the same time so that energy is not wasted. Some data processing was also done to estimate the energy consumption by each device and confirmed that the cooling and heating energy consumption rates were consistent with commercially available units. Overall, the simulation showed that utilising IoT was a viable method for controlling the temperature and energy consumption of a house, while future real world testing is required to measure energy savings by using this approach for monitoring and controlling heating and cooling systems
Hybrid Renewable Energy Systems with Hydrogen and Battery Storage Options for Stand-Alone Residential Building Application in Canada
No full textAs the world moves definitively towards cleaner energy and deploys resources to reduce greenhouse gas emissions, greater interest in the potential for implementing hybrid renewable energy systems (HRES) has been ignited. This study aims to investigate the technical and economic feasibility of using an HRES with hydrogen and battery storage alternatives to provide electricity for remote household use. Dynamic simulation models were developed in HOMER Pro 3.15 software to simulate and optimize the performance of the proposed microgrid (MG) systems. Two different system configurations were simulated, which consisted of various components and systems, including solar photovoltaic (PV) panels, diesel generators, hydrogen production and storage systems, and battery storage. These MG configurations were simulated and optimized for a stand-alone household in Canada. The simulation results proved that both PV-hydrogen-diesel and PV-battery-diesel systems are viable solutions for MG applications. Moreover, the results indicated that the configuration with hydrogen storage was less economical than that which utilised conventional, mature battery storage. Diesel generators played a vital role in providing backup energy to the system s, which enhanced their reliability, an important factor particularly during the harsh Canadian winter months when the electrical load was highest. It should be mentioned that it is expected that when development in hydrogen technology is further advanced and deployed in the near future, the hydrogen-based MG system cost will likely drop significantly
Performance investigation of solar organic Rankine cycle system with zeotropic working fluid mixtures for use in micro-cogeneration
No full textOverall, there are numerous sustainable sources of renewable, low-temperature heat, principally solar energy, geothermal energy, and energy produced from industrial wastes. Extended utilization of these low-temperature alternatives has a certain capacity of decreasing fossil fuel use with its associated very hazardous greenhouse gas emissions. Researchers have commonly recognized the organic Rankine cycle (ORC) as a feasible and suitable system to produce electrical power from renewable sources based on its advantageous use of volatile organic fluids as working fluids (WFs). Researchers have similarly shown an affinity to the exploitation of zeotropic mixtures as ORC WFs due to their capability to enhance the thermodynamic performance of ORC systems, an achievement supported by improved fits of the temperature profiles of the WF and the heat source/sink. This paper determines both the technical feasibility and the benefits of using zeotropic mixtures as WFs by means of a simulation study of an ORC system. This study analyzes the thermodynamic performance of ORC systems using zeotropic WF mixtures to produce electricity driven by low-temperature solar heat sources for use in buildings. A thermodynamic model is created with an ORC system with and without a regenerator. Five zeotropic mixtures with diverse compositions between 0 and 1 in 0.2 increments of R245fa/propane, R245fa/hexane, R245fa/heptane, pentane/hexane, and isopentane/hexane are assessed and compared with identify the best blends of mixtures that are able to produce superior efficiency in their system cycles. Results disclosed that R245fa/propane (0.4/0.6) with regenerator produces the highest net power output of 7.9 kW and cycle efficiency of 9.4% at the operating condition with a hot source temperature of 85 °C. The study also investigates the effects of the volume flow ratio, and evaporation and condensation temperature glide on the ORC's thermodynamic performance. Following a thorough analysis of each mixture, R245fa/propane is chosen for a parametric study to examine the effects of operating factors on the system's efficiency and sustainability index. It was found that the highest cycle efficiency and highest second law cycle efficiency of around 10.5% and 84.0%, respectively, were attained with a mass composition of 0.6/0.4 at the hot source temperature of 95 °C and cold source temperature of 20 °C with a net power output of 9.6 kW. Moreover, results revealed that for zeotropic mixtures, there is an optimal composition range within which binary mixtures are tending to work more efficiently than the component pure fluids. In addition, a significant increase in cycle efficiency can be achieved with a regenerative ORC, with cycle efficiency in the range 3.1-9.8% versus 8.6-17.4% for ORC both without and with regeneration, respectively. In conclusion, utilizing zeotropic mixtures may well expand the restriction faced in choosing WFs for solar-powered ORC-based micro-combined heat and power (CHP) systems
Internet of Things (IoT) Monitoring and Control for Smart Heating and Cooling in a Residential Building
No full textWith building sector accounting for 40% of current total energy utilization, notably within heating, ventilation, and air conditioning (HVAC) systems, the imperative to mitigate this challenge is evident. To address this issue and curtail energy usage in the sector, researchers are exploring various tools. One promising approach is leveraging the Internet of Things (IoT) to optimize energy usage during heating and cooling of buildings. This work specifically investigated an IoT-based system for monitoring and controlling heating and cooling in Canadian residential housing. The simulation focused on a house from the Canadian Centre for Housing Technology, evaluated during the fall season using two control strategies responding to outside air temperature conditions and additionally introducing time-oriented temperature in the house. The results demonstrated that the house could consistently maintain a desired comfort level, irrespective of the outdoor conditions. Moreover, the developed IoT system accurately determined whether heating or cooling was required, efficiently avoiding simultaneous usage of both systems to prevent energy wastage. A comparison between the two control strategies revealed that the enhanced one exhibited significant improvement in energy consumption compared to the previous approach. Specifically, during fall, the IoT-based system using the improved control strategy demonstrated an average of 21% and 30% lower energy consumption for heating and cooling modes, respectively. Clearly, adopting wise control strategies proved to be an effective means of reducing energy consumption. In conclusion, this simulation effectively demonstrated the potential of IoT in monitoring and controlling household temperatures, leading to reduced energy consumption. However, it is recommended further field measurement is necessary to quantify the energy reductions when implementing this method for smart home HVAC systems
Optimal Design and Cost Analysis of Microgrid Hybrid Renewable Energy Systems with Hydrogen Production and Storage and Battery
No full textConcern about controlling climate change, and recognition of the urgent need to reduce the quantum of greenhouse gases emitted worldwide, has kindled interest in alternative sources of energy. Particular attention is currently on microgrid (MG) hybrid renewable energy systems. This work has been undertaken to appraise the viability of applying MGs with both hydrogen production and storage, and battery options to supply electricity for off-grid applications. Simulation models were created in HOMER platform to analyze and optimize the performance of the considered configurations for an off-grid residential building in Canada. Two distinct system arrangements were assessed, which comprised of photovoltaic (PV) panels, wind turbines (WTs), fuel cells (FCs), electrolysers, hydrogen tanks, battery storage, diesel generators, converters, and controllers. The outcomes demonstrated that both systems are viable selections. Furthermore, it was proven that the MG battery-based system is the better arrangement for the household considered that results to the minimum levelized cost of energy (COE) and a renewable fraction (RF) of 0.36/kWh and 82.2%, respectively, compared to the hydrogen-based one, which has a COE and an RF of 0.57/kWh and 70.1%, respectively. With increasing recognition of, and interest in hydrogen technology, it is hoped that advances and discoveries in this beneficial technology will naturally be made, leading to significant reductions in the present costliness of operating the system
Recent Advances in Small-Scale Carbon Capture Systems for Micro-Combined Heat and Power Applications
Full text linkTo restrict global warming and relieve climate change, the world economy requires to decarbonize and reduce carbon dioxide (CO2) emissions to net-zero by mid-century. Carbon capture and storage (CCS), and carbon capture and utilization (CCU), by which CO2 emissions are captured from sources such as fossil power generation and combustion processes, and further either reused or stored, are recognized worldwide as key technologies for global warming mitigation. This paper provides a review of the latest published literature on small-scale carbon capture (CC) systems as applied in micro combined heat and power cogeneration systems for use in buildings. Previous studies have investigated a variety of small- or micro-scale combined heat and power configurations defined by their prime mover for CC integration. These include the micro gas turbine, the hybrid micro gas turbine and solid-state fuel cell system, and the biomass-fired organic Rankine cycle, all of which have been coupled with a post-combustion, amine-based absorption plant. After these configurations are defined, their performance is discussed. Considerations for optimizing the overall system parameters are identified using the same sources. The paper considers optimization of modifications to the micro gas turbine cycles with exhaust gas recirculation, humidification, and more advanced energy integration for optimal use of waste heat. Related investigations are based largely on numerical studies, with some preliminary experimental work undertaken on the Turbec T100 micro gas turbine. A brief survey is presented of some additional topics, including storage and utilization options, commercially available CC technologies, and direct atmospheric capture. Based on the available literature, it was found that carbon capture for small-scale systems introduces a large energy penalty due to the low concentration of CO2 in exhaust gases. Further development is required to decrease the energy loss from CC for economic feasibility on a small scale. For the micro gas turbine, exhaust gas recirculation, selective gas recirculation, and humidification were shown to improve overall system economic performance and efficiency. However, the highest global efficiencies were achieved by leveraging turbine exhaust waste heat to reduce the thermal energy requirement for solvent regeneration in the CC plant during low- or zero-heating loads. It was shown that although humidification cycles improved micro gas turbine cycle efficiencies, this may not be the best option to improve global efficiency if turbine waste heat is properly leveraged based on heating demands. The biomass-organic Rankine cycle and hybrid micro gas turbine, and solid-state fuel cell systems with CC, are in early developmental stages and require more research to assess their feasibility. However, the hybrid micro gas turbine and solid-state fuel cell energy system with CC was shown numerically to reach high global efficiency (51.4% LHV). It was also shown that the biomass-fired organic Rankine cycle system could result in negative emissions when coupled with a CC plant. In terms of costs, it was found that utilization through enhanced oil recovery was a promising strategy to offset the cost of carbon capture. Direct atmospheric capture was determined to be less economically feasible than capture from concentrated point sources; however, it has the benefit of negative carbon emissions
Dynamic Simulation of Organic Rankine Cycle-Assisted Ground-Source Heat Pump Based Micro-Cogeneration System in Cold Climates: A Case Study in Canada
No full textAs the energy needed for heating and cooling involves a substantial amount (>80%) of residential energy utilisation in Canada, there is a demand for ultra-efficient energy systems for heating, cooling, and power generation. Two efficient systems to assist these systems are ground-source heat pumps (GSHPs) and organic Rankine cycles (ORCs). Of particular interest, this paper presents the integration of these two systems in a parallel configuration. A transient simulation model developed in TRNSYS program has been utilised to simulate the thermal performance of the combined ORC-GSHP based microco/ trigeneration system. This later supplies heating and cooling to the residential load during the heating mode as required, with the capability to switch to a charging mode, where the ORC unit is directly coupled to the ground heat exchanger (GHE), which operates as a thermal energy storage and provides energy to the GSHP. The feasibility of this combined system configuration as well as its comparison with a conventional GSHP system are investigated for use in residential application in Ottawa, Canada temperature conditions. Results disclosed that the proposed micro-cogeneration system had the operating hours and performance of the GSHP improved by the addition of the ORC unit, resulting in about 11.8% reduction in hours in the colder city of Ottawa. The COP (coefficient of performance) of the GSHP system sustained a much higher value overall due to the addition of the ORC system to maintain the GHE storage temperature. In terms of net energy reduction between the conventional GSHP system and the ORC assisted one, results revealed that Ottawa had energy usage reduction of 82.0%, demonstrating that the addition of an ORC to provide heating and recharge the GHE of a GSHP system has many advantages that could be accomplished by the end-user
Thermodynamic, economic and sustainability analysis of solar organic rankine cycle system with zeotropic working fluid mixtures for micro-cogeneration in buildings
Full text linkGlobally there are several viable sources of renewable, low-temperature heat (below 130◦C), particularly solar energy, geothermal energy, and energy generated from industrial wastes. Increased exploitation of these low-temperature options has the definite potential of reducing fossil fuel consumption with its attendant very harmful greenhouse gas emissions. Researchers have universally identified the organic Rankine cycle (ORC) as a practicable and suitable system to generate electrical power from renewable sources based on its beneficial usage of volatile organic fluids as working fluids (WFs). In recent times, researchers have also shown a preference towards deployment of zeotropic mixtures as ORC WFs because of their capacity to improve thermodynamic performance of ORC systems, a feat enabled through the greater matching of the temperature profiles of the WF and the heat source/sink. This paper demonstrates the thermodynamic, economic and sustainability feasibility, and the notable advantages of using zeotropic mixtures as WFs through a simulation study of an ORC system. The study examines first the thermodynamic performance of ORC systems using zeotropic mixtures to generate electricity powered by a low-temperature solar heat source for building applications. A thermodynamic model is developed with a solar-driven ORC system both with and excluding a regenerator. Twelve zeotropic mixtures with varying compositions are evaluated and compared to identify the best combinations of mixtures that can yield high performance and high efficiency in their system cycles. The study also examines the effects of the volume flow ratio, and evaporation and condensation temperature glides on the ORC’s thermodynamic performance. Following a detailed analysis of each mixture, R245fa/propane and butane/propane are selected for parametric study to investigate the influence of operating parameters on the system’s efficiency and sustainability index. For zeotropic mixtures, results disclosed that there is an optimal composition range within which binary mixtures are inclined to perform more efficiently than the component pure fluids. In addition, a substantial enhancement in cycle efficiency can be obtained by a regenerative ORC, with cycle efficiency ranging between 3.1–9.8% and 8.6–17.4% for ORC both without and with regeneration, respectively. Results also revealed that exploiting zeotropic mixtures could enlarge the limitation experienced in selecting WFs for low-temperature solar ORCs. Moreover, a detailed economic with a sensitivity analysis of the solar ORC system was performed to evaluate the cost of the electricity and other economic criteria. The outcome of this investigation should be useful in the thermo-economic feasibility assessments of solar-driven ORC systems using working fluid mixtures to find the optimum operating range for maximum performance and minimum cost
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