Waste Heat Recovery from a Drier Receiver of an A/C Unit Using Thermoelectric Generators

Thermoelectric generators(TEGs)are considered promising devices for waste heat recovery from various systems.The Seebeck effect can be utilized to generate power using the residual heat emitted by the filter dryer receiver(FDR)of an air conditioning(A/C)system,which would otherwise go to waste.The study aims to build a set of thermoelectric generators(TEG)to collect the waste heat of the FDR and generate low-power electricity.A novel electrical circuit with two transformers is designed and fabricated to produce a more stable voltage for operation and charging.The thermoelectric generator(TEGs)was installed on the FDR of the A/C unit.The test showed that climate conditions have a significant impact on the output power generated from the system.The results showed that the peak voltage recorded in the current study is 5.2 V per day(wet,cold,and wind weather)with an output power of 0.2 W.These values are acceptable for powering the load and charging a single battery with 3.5 V as the voltage increases battery 0.1 V/20 min charge.A case study of operating the emergency signs in a building was considered.The current heat recovery system is deemed to be easily installed and can be connected to a network of TEGs to produce more power.

Simulation Analysis of Flue Gas Waste Heat Utilization Retrofit Based on ORC System

Recovery of waste heat from boiler flue gas is an effective way to improve energy utilization efficiency.Taking a heating station heating project as an example,the existing heating system of this heating station was analyzed for its underutilized flue gas waste heat and low energy utilization rate.Rankine cycle is an effective waste heat recovery method,and a steam boiler organic Rankine cycle(ORC)cogeneration waste heat utilization method is proposed.The system model simulation is constructed and verified.First,a thermodynamic model was constructed in MATLAB and five suitable work gases were selected to analyze the effects of evaporation temperature and condensation temperature on the network and thermal efficiency of the waste heat cycle power system.Secondly,the ORC model is invoked in TRNSYS to construct the improved cogeneration system,and the rationality of the remaining heat utilization methods is determined by calculating and analyzing the thermal performance,economy,and environmental protection of the improved system.The simulation results show that the system can generate about 552,000 kWh of electricity per year,and improving the energy utilization rate from 0.72 to 0.78.

Waste heat recovery from hot steel slag on the production line:Numerical simulation,validation and industrial test

Waste heat recovery from hot steel slag was determined in a granular bed through the combination of numerical simulation and an industrial test method.First,the effective thermal conductivity of the granular bed was calculated.Then,the unsteady-state model was used to simulate the heat recovery under three different flow fields(O-type,S-type,and nonshielding type(Nontype)).Second,the simulation results were validated by in-situ industrial experiments.The two methods confirmed that the heat recovery efficiencies of the flow fields from high to low followed the order of Nontype,S-type,and O-type.Finally,heat recovery was carried out under the Nontype flow field in an industrial test.The heat recovery efficiency increased from~76%and~78%to~81%when the steel slag thickness decreased from 400 and 300 to 200 mm,corresponding to reductions in the steel slag mass from 3.96 and 2.97 to 1.98 t with a blower air volume of 14687 m^(3)/h.Therefore,the research results showed that numerical simulation can not only guide experiments on waste heat recovery but also optimize the flow field.Most importantly,the method proposed in this paper has achieved higher waste heat recovery from hot steel slag in industrial scale.

Off-Design Simulation of a CSP Power Plant Integrated with aWaste Heat Recovery System

Concentrating Solar Power(CSP)plants offer a promising way to generate low-emission energy.However,these plants face challenges such as reduced sunlight during winter and cloudy days,despite being located in high solar radiation areas.Furthermore,their dispatch capacities and yields can be affected by high electricity consumption,particularly at night.The present work aims to develop an off-design model that evaluates the hourly and annual performances of a parabolic trough power plant(PTPP)equipped with a waste heat recovery system.The study aims to compare the performances of this new layout with those of the conventional Andasol 1 plant,with the aim of assessing the improvements achieved in the new design.Based on the results,it can be concluded that the new layout has increased the annual generated power to almost 183 GWh(an increase of about 7.60% is achieved compared to the Andasol 1 layout that generates 169 GWh annually).Additionally,the proposed installation has achieved an efficiency of 20.55%,which represents a 7.87% increase compared to the previous design(19.05%).The Levelized Cost of Electricity(LCOE)of the new layout has been reduced by more than 5.8% compared to the Andasol 1 plant.Specifically,it has decreased from 13.11 to 12.35 c/kWh.This reduction in LCOE highlights the improved cost-effectiveness of the newlayout,making it amore economically viable option for generating electricity compared to the conventional Andasol 1 plant.

THE EXERGETIC EFFICIENCY OF MSF PROCESS AND THE CONDITIONS OF DESALINATION BY WASTE HEAT

The exergy losses and thermodynamic efficiency of MSF plant with brine recirculation are discussed bymeans of temperature difference functions proposed by the auther.In a MSF plant,the irreversible losses are found mainly in irreversible heat-transfer and flash evaporationprocesses.However,the basic variables are the temperature drop from stage to stage and the temperaturedifferences between flashed vapor and cooling water.In this paper,the flash temperature difference func-tion,the heat transfer temperature difference function and the total temperature difference function are sug-gested.The proposed temperature difference functions of MSF plant provide a convenient tool to analyse theirreversible behavior and evaluate the exergetic efficiency of this system,because without such improvement thecalculation of the exergetic efficiency of a MSF plant according to the classical formula will be not onlyinconvenient but also insignificant.As a result of present analysis,the reasonable parameters based on theenergy consumption are easily chosen.The above-mentioned principles are confirmed by commercial plants and a pilot plant in Tianjin.

A Steady-State Evaluation of Simple Organic Rankine Cycle (SORC) with Low-Temperature Grade Waste Heat Source

The low-grade heat source recovery is usually constrained by the physical characteristics of the hot fluid medium. The present work focuses on the importance of energy recovery from low-temperature waste energy sources and its conversion to useful electrical power. The thermal performance analysis is based on the utilization of R-123, R-134a, R-290, R-245fa, R-1234ze-E, and R-1233zd-E fluids in a simple organic Rankine cycle (SORC). A waste energy source from an industrial sector is suggested to be available at a temperature greater than 110 °C. A hypothetical organic Rankine cycle of 10 kW nominal heat recovery was implemented to evaluate the cycle performance. It operates at evaporation and condensation temperatures of 90 °C and 45 °C, respectively. The selected vapor superheat degree at the expander entrance was 5 °C - 15 °C, and the liquid was subcooled by 5 °C at the discharge port of condenser. The estimated first law cycle thermal efficiency fell in the range of 6.4% - 7.7%. The results showed that the thermal efficiencies of R-134a, R-123, R-245fa, R-1233zd-E, and R-1234ze-E were higher than that of R-290 by 10% - 14%, 11% - 12%, 9% - 12%, 4% - 7% and 1% - 3%, respectively. R-1233zd-E, R-1234ze-E, and R-290 showed close thermal efficiency values, and it fell in the range of 6.7% - 7% for the (SORC) at a superheat degree of 15 °C. At the same superheat degree, the corresponding range of thermal efficiency for R-134a, R-123 and R-245fa fell within 7.5% - 7.7%. R-134a possessed the highest net power output of the (SORC);it reached a value of 0.91 kW as predicted at 15 °C superheat degree. Increasing the expander volumetric efficiency value by 10% improved the cycle thermal efficiency by 10% - 12%.

Comprehensive Energy-Saving Technology for RTO Flue Gas Waste Heat Utilization

In the automobile painting workshop,the oven will discharge harmful exhaust gas,the exhaust gas can be reused through the TNV system,the natural gas can meet the emission standard to the atmosphere after burning,and the high temperature gas discharged TNV the system can carry considerable heat.Utilization can effectively improve the economic benefits of the factory.At present,the more mature scheme is to heat the high temperature exhaust gas through the heat exchanger,which can reduce the steam consumption of the factory.Based on the analysis of the comprehensive energy saving content of waste heat utilization of RTO flue gas,this paper hopes to provide some reference and reference for readers.

Transforming Waste Heat into“Renewable Heat”

Introduction:The current worldwide electric power&heat&cool production has a negative impact on the environment by emissions and enormous leaks of low-potential waste heat.Transformation of unused industrial low power heat into“renewable heat”useful to enhance the efficiency of the system is essential and actual innovation in the field of worldwide environmental protection.By introducing and defining the terminology of low-potential,“renewable”,“green heat”has created a new,parallel category of research in the energy sector.Traditional co-generation systems produce heat for space heating and hot water and generate electricity.Moving to tri-generation allows growing demand for air conditioning for homes,offices and commercial spaces such as server rooms and switchboards to be met simultaneously or on a seasonal basis.Tri-generation,or combined cooling,heat and power,is the process by which some of the heat produced by a co-generation plant is used to generate chilled water for air conditioning or refrigeration.Usually an absorption chiller is linked to the plant to provide this functionality.The technical solution is related to the new efficient manner and system of simultaneous generation of heat/cold from multiple heat sources,which has not yet been known,but in practice required.New system also enables advantageous utilization of solar power in supporting of the cooling output.The innovative system can be operated also within the existing central heating distribution systems.

Utilization and recycling of low-temperature waste heat of stainless steel continuous annealing furnace

Stainless steel continuous annealing furnace is mainly used for heat treatment of hot-rolled strip steel.The combustion air will be enabled to heat to 520℃by waste heat recovery system,but the discharge temperature is still up to about 300℃.Owing to with development of global emphasis on energy conservation energy saving and discharge reduction,it’s significant to lower the discharge temperature to below 200℃, for the sake of achieving rational use of waste heat resource.Through the analysis of the existing heat recovery system by this study,it is proved that mixing low temperature with flue gas in high temperature standard will increase the capacity of the flue gas and deteriorate the quality of remaining heat resource.In stead of that,increasing the combustion air temperature to 600℃on the basis of stability temperature for the prerequisite of recuperator design,and giving priority to reducing fuel consumption are the better way.The recovery and recycle of low temperature gas are also be introduced.It is demonstrated by the way of setting a secondary recuperator at the exit of the primary recuperator,and using low temperature flue gas to heat the air used for drying the strip steel,the exhuast temperature of flue gas can be reduced to lower than 200℃.At the same time,the steam required for heating air is saved,the energy reserve as high as 2 300 t of standard coal per year.

Preparation of gangue ceramsite by sintering pot test and potential analysis of waste heat recovery from flue gas

Preparation of ceramsite from solid waste based on the sintering process is a new technology and had a high efficiency in improving producing capability, decreasing consumption of liquefied petroleum gas (LPG), and recovering waste heat of flue gas. An experiment sintering gangue ceramsite was conducted in a 25 kg scale sintering pot with a 100 cm height. The combustion characteristics, phase transformation, and the release profile of SO_(2)^(*) (SO and/or SO_(2)) and NO_(x)^(*) (N_(2)O, NO, and/or NO_(2)) of gangue ceramsite during the sintering process were studied by X-ray diffraction analysis, X-ray fluorescence spectrometry, thermogravimetry–differential thermogravimetry–differential scanning calorimetry, and measurement of physical properties of ceramsite and gas components of flue gas. The results showed that the gangue ceramsite had excellent properties, and its compressive strength and water absorption were 8.2–9.6 MPa and 8.9%–9.8%, respectively, far exceeding the requirement of standard (GB/T 17431.1–2010). The ignition temperature of gangue ceramsite was 443 ℃, and the ignition loss was 14.60 mass% at 1000 ℃. Kaolinite and calcite disappeared at 600 and 800 ℃, respectively. Albite disappeared and mullite formed at 1000 ℃. Two peaks of SO_(2)^(*) emissions emerged in the range of 311–346 mg m^(-3) near 500 ℃ of upper layer ceramsite and 420–489 mg m^(-3) near 1000 ℃ of lower layer ceramsite, respectively. NO_(x)^(*) emissions peak emerged in the range of 227–258 mg m^(-3) near 550 ℃ of the upper layer ceramsite, which was related to the oxidation of sulfide and the combustion of LPG. Gangue is a direct heat source for sintering of ceramsite as well. During sintering process, the heat of flue gas above and below 400 ℃ accounts for 55.9% and 30.0% of the all-output heat, respectively, and was potentially used for producing waste-heat steam or electricity as by-products and drying raw materials during its own initial sintering process, which can realize combined mass and heat utilization for the gangue and further reduce the cost of sintered gangue ceramsite.

Energy,Exergy,and Exergoeconomic Analysis of Solar-Driven Solid Oxide Electrolyzer System Integrated with Waste Heat Recovery for Syngas Production

Syngas fuel generated by solar energy integrating with fuel cell technology is one of the promising methods for future green energy solutions to carbon neutrality.This paper designs a novel solar-driven solid oxide electrolyzer system integrated with waste heat for syngas production.Solar photovoltaic and parabolic trough collecter together drive the solid oxide electrolysis cell to improve system efficiency.The thermodynamic models of components are established,and the energy,exergy,and exergoeconomic analysis are conducted to evaluate the system’s performance.Under the design work conditions,the solar photovoltaic accounts for 88.46%of total exergy destruction caused by its less conversion efficiency.The exergoeconomic analysis indicates that the fuel cell component has a high exergoeconomic factor of 89.56%due to the large capital investment cost.The impacts of key parameters such as current density,operating temperature,pressure and mole fraction on system performances are discussed.The results demonstrate that the optimal energy and exergy efficiencies are achieved at 19.04%and 19.90%when the temperature,pressure,and molar fraction of H_(2)O are 1223.15 K,0.1 MPa,and 50%,respectively.

Thermodynamics of Cascaded Waste Heat Utilization from Flue Gas and Circulating Cooling Water

A detailed thermal power plant model was developed to evaluate power plant waste heat usage in terms of the operating parameters,energy consumption,water consumption,and pollutant emissions.This model was used to analyze the bypass flue gas energy cascade utilization design which provides excellent energy savings and emission reductions.This paper then presents a design to use the low-temperature waste heat and to extract water from the flue gas.The low-grade heat can be recovered from a coal-fired unit using absorption heat pumps to increase the air preheating.This method significantly reduces the turbine steam extraction in the low pressure stages which increases the turbine power and reduces the coal consumption.This design has a small heat transfer temperature difference between the air preheater and the air warmer,resulting in a smaller exergy loss.The power output of the present design was 1024.28 MW with a coal consumption savings of 3.69 g·(kWh)^(−1).In addition,the present design extracts moisture out of the flue gas to produce 46.48 t·h^(−1)of water.The main goal of this work is to provide a theoretical analysis for studying complex thermal power plant systems and various energy conservation and CO_(2)reduction options for conventional power plants.

Effect of flue gas outlet temperature in evaporator on thermal economic performance of organic Rankine cycle system for sinter waste heat recovery

In order to improve the recovery and utilization rates of sinter waste heat effectively,the organic Rankine cycle(ORC)system with subcritical cycle was designed to recover the low-temperature sinter cooling flue gas waste heat in an annular cooler for power generation.The thermodynamic,economic and multi-objective optimization models of ORC system were established,and R600a was selected as the ORC working medium.Subsequently,the variations in system thermodynamic performance and economic performance with the ORC thermal parameters were discussed in detail,and the optimal ORC thermal parameters were determined.The results show that the system net output power increases with increasing the evaporation temperature and decreasing the condensation temperature and increases first and then,decreases with the increase in superheat degree for a given flue gas outlet temperature in the evaporator,while the heat transfer area per unit net output power appears different variation trends in various ranges of flue gas outlet temperature.Taking the sinter cooling flue gas waste heat of 160℃as the ORC heat source,the optimal thermal parameters of ORC system were the flue gas outlet temperature of 90℃,the evaporation temperature of 95℃,the superheat degree of 10℃,and the condensation temperature of 28℃.

A Distributed Energy System with Advanced Utilization of Internal Combustion Engine Waste Heat

New trigeneration system consists of an internal combustion engine,a power and cooling cogeneration system and an absorption heat transformer system.The exhaust gas is recovered by the power and cooling cogeneration subsystem producing the cooling and power.The jacket water is recovered by the absorption heat transformer subsystem producing lowpressure steam.The exergy performance and the energy saving performance which is evaluated by the primary energy saving ratio of the new distributed energy system are analyzed.The effects of the ratio of the output power and cooling of the power and cooling cogeneration subsystem and the generator outlet temperature of the absorption heat transformer subsystem to the primary energy saving ratio are considered.The contributions of the subsystems to the primary energy saving ratio are quantified.The maximum primary energy saving ratio of the new distributed energy system is 15.8%,which is 3.9 percentage points higher than that of the conventional distributed energy system due to the cascade utilization of the waste heat from the internal combustion engine.

A review of concentrated photovoltaic-thermal(CPVT) hybrid solar systems with waste heat recovery(WHR)

In conventional photovoltaic(PV) systems, a large portion of solar energy is dissipated as waste heat since the generating efficiency is usually less than 30%. As the dissipated heat can be recovered for various applications, the wasted heat recovery concentrator PV/thermal(WHR CPVT) hybrid systems have been developed. They can provide both electricity and usable heat by combining thermal systems with concentrator PV(CPV) module, which dramatically improves the overall conversion efficiency of solar energy.This paper systematically and comprehensively reviews the research and development of WHR CPVT systems. WHR CPVT systems with innovative design configurations, different theoretical evaluation models and experimental test processes for several implementations are presented in an integrated manner. We aim to provide a global point of view on the research trends, market potential, technical obstacles, and the future work which is required in the development of WHR CPVT technology. Possibly, it will offer a generic guide to the investigators who are interested in the study of WHR CPVT systems.

Energy management strategy for hybrid electric vehicle integrated with waste heat recovery system based on deep reinforcement learning

Hybrid electric vehicles(HEVs)are acknowledged to be an effective way to improve the efficiency of internal combustion engines(ICEs)and reduce fuel consumption.Although the ICE in an HEV can maintain high efficiency during driving,its thermal efficiency is approximately 40%,and the rest of the fuel energy is discharged through different kinds of waste heat.Therefore,it is important to recover the engine waste heat.Because of the great waste heat recovery performance of the organic Rankine cycle(ORC),an HEV integrated with an ORC(HEV-ORC)has been proposed.However,the addition of ORC creates a stiff and multi-energy problem,greatly increasing the complexity of the energy management system(EMS).Considering the great potential of deep reinforcement learning(DRL)for solving complex control problems,this work proposes a DRL-based EMS for an HEV-ORC.The simulation results demonstrate that the DRL-based EMS can save 2%more fuel energy than the rule-based EMS because the former provides higher average efficiencies for both engine and motor,as well as more stable ORC power and battery state.Furthermore,the battery always has sufficient capacity to store the ORC power.Consequently,DRL showed great potential for solving complex energy management problems.

Comparison of Conventional and Advanced Exergy Analysis for Dual-Loop Organic Rankine Cycle used in Engine Waste Heat Recovery

At present,the dual-loop organic Rankine cycle(DORC)is regarded as an important solution to engine waste heat recovery(WHR).Compared with the conventional exergy analysis,the advanced exergy analysis can better describe the interactions between system components and the irreversibility caused by economic or technical limitations.In order to systematically study the thermodynamic performance of DORC,the conventional and advanced exergy analyses are compared using an inline 6-cylinder 4-stroke turbocharged diesel engine.Meanwhile,the sensitivity analysis is implemented to further investigate the influence of operating parameters on avoidable-endogenous exergy destruction.The analysis result of conventional exergy analysis demonstrates that the priorities for the components that should be improved are in order of the high-temperature evaporator,the low-temperature turbine,the first low-temperature evaporator and the high-temperature condenser.The advanced exergy analysis result suggests that the avoidable exergy destruction values are the highest in the low-temperature turbine,the high-temperature evaporator and the high-temperature turbine because they have considerable endogenous-avoidable exergy destruction.The sensitivity analysis indicates that reducing the evaporation pinch point and raising the turbine efficiency can decrease the avoidable exergy destruction.

Experimental Analysis of Atypically Long Finned Oscillating Heat Pipe for Ventilation Waste Heat Recovery Application

Oscillating heat pipes(OHP)which are constructed from a serpentine-arranged capillary tube possess a desirable aerodynamic form factor and provide for relatively high heat transfer rates via cyclic evaporation and condensation of an encapsulated working fluid with no internal wicking structure required.In last two decades,OHP has been extensively investigated for its potential application in thermal management of various applications.This study presents an experimental investigation on the heat transfer performance of an atypically long finned OHP.The heat transfer performance of the proposed OHP was analyzed and compared with a bare tube OHP with similar overall dimensions.Results show that a unit row of finned OHP filled with n-pentane with fill ratio of 70%can recover up to(400±40)W of heat from a typical waste exhaust air stream.The additional pressure drop due to fins was estimated to be(6.8±2)Pa resulting in an increase of 1–2 W of fan power consumption.The average heat recovery rate via finned OHP was found to be almost 80%more than bare tube OHP filled with same working fluid with same fill ratio.

Comprehensive evaluation of marine waste heat recovery technologies based on Hierarchy-Grey correlation analysis

In this study,comprehensive evaluation of the technologies on waste heat recovery technologies for maritime applications has been carried out.We have focused our research on exhaust gas turbine system(EGT),thermodynamic organic rankine cycle(RC),Kalina cycle(KC)and thermoelectric generators(TG),which are the most appropriate and most up-to-date techniques for recovering power from marine engines.Each technology has its own advantages and disadvantages,so the comprehensive evaluation of these technologies is essential to accurately determine which technology will be applied to which target.This belongs to the multi-criteria decision(MCDM)process.The combined assessment methodology,consisting of gray correlation and analysis hierarchy processes,has been applied to evaluate four waste heat recovery techniques in terms of technical,economic,social and environmental aspects.According to the comparison results,the exhaust gas turbine system has been evaluated as the most promising technology among the various WHR technologies that can be applied to marine engines.Sensitivity analysis suggests that if investment cost of TG falls to about the same level as the one of EGT,TG could be the best method among these technologies.Reduction of investment cost of TG technology could be realized by development of low cost thermoelectric material.We have analyzed the correlation between each cost through DOE analysis and investigate the effect of individual costs on the total cost.This work helps in identifying the most suitable heat recovery technologies for marine engine.

A four-dimensional interaction-based appraisal approach towards the performance enhancement of a vehicular waste heat recovery system

The non-linear multifactorial impacts on fuel-saving potential constrain the practical performance of the vehicular waste heat recovery system(WHRS). This study proposed a four-dimensional interaction-based appraisal approach to interpreting these impacts for enhancing WHRS's in-vehicle performance. The interaction incorporates a heat exchanger, configuration, engine,and vehicle. The proposed approach comprises two successive steps, emphasizing evaluation under the rated(Step 1) and off-design(Step 2) heat source conditions. A case study of waste heat recovery from a passenger vehicle was conducted to evaluate the in-vehicle performance of a novel co-split system and two single-split ones(with/without a regenerator) through this approach. The novel system theoretically modifies vehicular performance but remains ambiguous concerning real-world behaviour, which is assessed and verified by the proposed approach. Two key factors determining vehicular performance were identified by Step 1, namely, net power output and engine backpressure. As the co-split system modified both factors, its fuel-saving potential could be increased by up to 20.3% compared with single-split systems. Also, the limiting factor for off-design performance was pinpointed by Step 2, namely, the mismatch between the heat source and working fluid, which led to the solution, i.e., the synergistic split regulation of the working fluid and heat source. An up to 8.8% improvement in net power output was achieved by the co-split system at off-design heat sources compared with fixed split ratios. Consequently, the approach enables holistic performance improvement of the vehicular WHRS under design/off-design heat source conditions.