Waste Heat Recovery Potential Research Articles

EMB3Rs: A game-changer tool to support waste heat recovery and reuse

At a time when European countries try to cope with escalating energy prices while decarbonizing their economies, waste heat recovery and reuse arises as part of the solution for sustainable energy transitions. The lack of appropriate assessment tools has been pointed out as one of the main barriers to the wider deployment of waste heat recovery projects and as a reason why its potential remains largely untapped.The EMB3Rs platform emerges as an online, open-source, comprehensive and novel tool that provides an integrated assessment of different types of waste heat recovery solutions, (e.g. internal or external) and comprises several analysis dimensions (e.g. physical, geographical, technical, market, and business models). It has been developed together with stakeholders, and tested in a number of representative contexts, covering both industrial and heat network applications. This has demonstrated the enormous potential of the tool in dealing with complex simulations, while delivering accurate results within a significantly lower time-frame than traditional analysis.The EMB3Rs tool removes important barriers such as analysis costs, time and complexity for the user, and aims at supporting a wider investment in waste heat recovery and reuse by providing an integrated estimation of the costs and benefits of such projects. This paper describes the tool and illustrates how it can be applied to help unlock the potential of waste heat recovery across European countries.

Dynamic Modelling of Data Center Waste Heat Potential Integration in District Heating in Latvia

As demand for data centers (DC) has increased rapidly, so has their electricity consumption. Cooling DCs is essential to maintain optimal temperatures for the operation of servers and equipment. The consequence of the cooling process is that most of the electricity consumed in DCs, including cooling, is eventually dissipated as heat that is released into the atmosphere without any useful application. Recovering and reusing waste heat offers a sustainable solution to reduce primary energy consumption and minimize the environmental impact. Using waste heat from DCs to heat buildings can significantly improve the energy efficiency and environmental sustainability of DCs. Therefore, this research analyzes the existing potential of waste heat recovery from data centers in Latvia and proposes a system dynamic modelling approach for evaluation of the future impact of waste heat on the national heat supply. The overall waste heat generated by DCs in 2022 was 51.37 GWh at a temperature of 65 °C. By 2050, the total heat energy production potential from DCs will increase to 257 GWh, with 201 GWh being utilized.

Mapping the waste heat recovery potential of CO2 intercooling compression via ORC

The goal of the present work is the systematic mapping of the electricity savings potential of waste heat recovery (WHR) from CO2 compression intercoolers via Organic Rankine Cycle (ORC) technology. Α generalized approach covering a broad range of target CO2 discharge pressures from 50 to 500 bar for 3 to up to 8 compression stages is followed. The maximum, theoretical electricity savings based on the exergy of the heat transfer fluid (HTF) used for intercooling range between 10 % and 24 %. Considering the exergy efficiency of optimized air-cooled ORCs operating with alkanes and hydrofluoroolefins for HTF temperatures between 70 °C and 130 °C, the maximum electricity savings ratio (i.e., the electricity savings compared to the total electricity consumption of the compression unit) is about 5 %, while the installed power of the WHR-ORC ranges from about 3 to 23 kWe per kg/s of compressed CO2. Because of the intense variability of CO2 specific heat capacity over a wide range of pressures, there is a very strong dependence of the waste heat potential on the final discharge pressure and number of stages. Through optimized mixing of the HTF streams, the performance of the WHR-ORC can be improved for particular discharge pressure ranges. Proper sizing of the ORC air-cooled condenser for minimizing air-side pressure drop is critical to ensure the feasibility of WHR-ORCs. According to a techno-economic analysis, WHR-ORCs can result in discounted payback periods from 6 to 12 years and 2.5 to 4 years for 4000 and 8000 operating hours, respectively.

Thermo-hydraulic and exergetic analysis of rectangular channel with integrated jet impingement and roughness

ABSTRACT This experimental study investigates an innovative approach to enhance surface heat transfer efficiency by employing V-pattern protrusions in conjunction with an impinging air jet. The synergy between surface roughness and the air jet induces heightened turbulence, resulting in significantly improved heat transfer performance. Various parameters on a jet plate, such as relative streamwise spacing (X/Dh), relative spanwise spacing (Y/Dh), and relative jet diameter (dJ/Dh), were systematically explored over a Reynolds number range of 4,000 to 18,000, representing the operational range. Optimal thermo-hydraulic efficiency was achieved at specific parameter values: relative streamwise spacing (X/Dh) of 1.7, relative spanwise spacing (Y/Dh) of 0.86, and relative jet diameter (dJ/Dh) of 0.086. Statistical correlations were established based on experimental data for both Nusselt number and friction factor. Furthermore, an exhaustive exergetic analysis was conducted to evaluate the thermal system’s sustainability, potential for waste heat recovery, and avenues for improvement. This study’s significance lies in its pioneering approach to augmenting heat transfer through the novel integration of V-pattern protrusions and impinging air jets. The results not only delineate optimal parameter configurations for enhancing heat transfer but also provide insights into system sustainability, waste heat recovery potential, and broader applications. By amalgamating distinct techniques, this research advances the existing literature by achieving superior thermal performance.

Validation and Application of a Finned Tube Heat Exchanger Model for Rack-Level Cooling

Abstract A thermosyphon-based modular cooling approach offers an energy efficient cooling solution with an increased potential for waste heat recovery. Central to the cooling system is an air-refrigerant finned tube heat exchanger (HX), where air is cooled by evaporating refrigerant. This work builds on a previously published two-dimensional (2D) model for the finned-tube HX by updating and validating the model using in-house experimental data collected from the proposed system using R1233zd(E) as the working fluid. The results show that key system variables such as refrigerant outlet quality, air and refrigerant outlet temperatures, and exchanger duty agree within 20% of their experimental counterparts. The validated model is then used to predict the mean heat transfer coefficient on the refrigerant side for each tube in the direction of airflow, indicating a maximum heat transfer coefficient of nearly 1200 W/(m2 K) for a HX duty of 5.3 kW among the tested cases. The validated model therefore enables accurate predictions of HX performance and provides insights into improving the heat exchange efficiency and the corresponding system performance.

Effect of hydrogen-enriched natural gas on flue gas waste heat recovery potential and condensing heat exchanger performance

Hydrogen-enriched natural gas (HENG) is one of the significant ways to store, transport, and utilize hydrogen energy. This paper presents the characteristics of HENG and flue gas, energy saving, carbon reduction, and condensate recovery potential of flue gas waste heat. Based on the theoretical and experimental study of the existing flue gas condensing heat exchanger (FGCHE) added at the rail of gas-fired boiler, the performance of the FGCHE under different hydrogen blending ratios is studied. The results show that augmenting the hydrogen blending ratio decreases the volume heating value of HENG, and CO2 content of flue gas. Meanwhile, the mass heating value of the HENG, the water vapor content, and dew point temperature of flue gas increase as the hydrogen blending ratio increases. The flue gas waste heat recovery utilization ratio and energy-saving efficiency of the FGCHE can be promoted. Moreover, the heat transfer capacity of the FGCHE using HENG is enhanced, while the flue gas flow pressure drop is reduced. Compared with the FGCHE used in pure natural gas systems, the all-hydrogen system increases the flue gas waste heat recovery amount by 62.4–120.4 %, reduces the flue gas flow pressure drop by 33.9 %, and reduces the carbon emission by 100 %.

Maisotsenko Cycle for Heat Recovery in Gas Turbines: A Fundamental Thermodynamic Assessment.

This paper reports the Maisotsenko's cycle-based waste heat recovery system with enhanced humidification to exploit the maximum waste heat recovery potential of the gas turbine. This research uses an integrated methodology coupling thermodynamic balances with heat transfer model of air saturator. The performance of the system is deduced which are assisted with sensitivity analysis indicating the optimal mass flow rate ratio (0.7-0.8) and pressure ratio (4.5-5.0) between the topping and bottoming cycles, and the air saturator split (extraction) ratio (0.5). The net-work output, energy, and exergy efficiencies of the system are found to be ≈58.39MW, ≈55.85%, and ≈52.79%, respectively. The maximum exergy destruction ratios are found as 68.2% for the combustion chamber, 16.0% for the topping turbine, 5.7% for topping compressor, 4.9% air saturator. The integration of Maisotsenko's cycle-based waste heat recovery system with a comprehensive thermodynamic model, as demonstrated in this research, offers valuable insights into enhancing the efficiency, cost-effectiveness, and environmental impact of gas turbines. By presenting fundamental equations related to thermodynamic balances, this work serves as an invaluable educational resource, equipping future researchers and students with the knowledge and skills needed to advance the study of thermodynamics and sustainable energy solutions.

Estimation of industrial waste heat recovery potential in China: Based on energy consumption

Waste heat is a major source of recoverable losses in societal energy use, and the recycling of waste heat offers great potential for reducing greenhouse gas emissions. To estimate the potential of waste heat recycling in China, a combined gray relational analysis and bi-directional long- and short-term memory (GRA-BiLSTM) forecasting model is proposed to forecast China's energy consumption under the 1.5 °C scenario and 2 °C scenario, respectively. The results show that the proposed prediction model has high performance with a Mean Absolute Percentage Error value of only 4.21%. Energy consumption peaks at 7015 mtec in 2040 for the 1.5 °C scenario, and continues to increase to 7965 mtec in 2050 for the 2 °C scenario with a peak trend. Energy consumption peaks in 2040 under the 1.5 °C scenario. Energy consumption in the 2 °C scenario continues to increase and peak by 2050. In addition, the potential of waste heat recycling is estimated based on the prediction results and the organic Rankine cycle. The results show that there is a huge potential for waste heat recycling in China, with a minimum of 3.6 TWh. And the economic metrics, such as payback period(Pt), net present value(NPV), and Levelized Cost of Electricity (LCOE) were used to show the economic feasibility of the method. The results show that the payback period for different scenarios is less than 5 years, and the lowest NPV is $2597.8 million. The cost consumed for each kWh produced is much lower than the average feed-in tariff in China, and we believe that the method is economically feasible.

Information theory-based dynamic feature capture and global multi-objective optimization approach for organic Rankine cycle (ORC) considering road environment

Efficient capture and global optimization of organic Rankine cycle (ORC) operating features in road environment is the key to obtain actual waste heat recovery potential. The complexity of time-varying characteristics intensifies the nonlinear coupling relationship between ORC performance and parameters. This paper first designs and builds an ORC experimental system for recovering waste heat from internal combustion engine (ICE). The experimental system includes ICE and its measurement subsystem, ORC subsystem, expander lubrication subsystem, cooling subsystem, and ORC measurement subsystem. R245fa is used as working fluid; The expander adopts a specially designed single screw expander. The performance of ORC waste heat recovery is tested by adjusting the operating conditions of the ICE, expander, pump, and valve opening. The temperature range of waste heat is 627–686 K. Subsequently, a dynamic feature capture and global multi-objective optimization approach for ORC is proposed. The results show that the precision of dynamic feature capture can be improved at least 41.78% with the introduction of information theory in complex environment. Frequent fluctuation of vehicle speed is not conducive to the improvement of evaporator inlet temperature at working fluid side. As the speed of the vehicle is greatly reduced, the evaporator inlet temperature drops sharply. The frequent fluctuation of speed will intensify the nonlinear correlation between operating parameters and system performance and make the system performance more dependent on the coupling correlation between operating parameters. The approach proposed in this paper can provide a new idea for efficient capture of dynamic characteristics and global multi-objective optimization of ORC in road environment.

Waste heat recovery potential in the thermochemical copper–chlorine cycle for hydrogen production: Development of an efficient and cost-effective heat exchanger network

With the finite nature of fossil fuel resources and related environmental issues, it is necessary to replace fossil-fuel-based hydrogen production methods with more sustainable ones. For the clean production of hydrogen, the copper-chlorine (Cu–Cl) thermochemical cycle is a favorable choice. However, internal waste heat recovery of the cycle is essential to improve the efficacy of the system. In this paper, the waste heat recovery potential of the four-step Cu–Cl cycle is investigated, to support the design of a new cost-effective and high-performance heat exchanger network. Pinch analysis is executed to find the optimum rates of cold and hot utilities for this cycle. Three heat exchanger network cases are investigated which include case 1, without heat recovery; case 2, with 16 heat exchangers; and case 3, with 11 heat exchangers. The effect of varying design parameters on the energy system's efficiency and cost-related parameters are also explored here. Based on the pinch analysis results, the minimum heating and cooling and the maximum recoverable heat, on a normalized basis, are 333.3 kJ/mol H2, 76.9 kJ/mol H2, and 134.4 kJ/mol H2, respectively. Moreover, for cases 1, 2, and 3 the thermal efficiencies are calculated as 33.3%, 41.1%, and 40.5%, respectively. Additionally, it is observed that, when the thermal energy of the cycle is supplied from a solar power tower plant, the levelized cost of hydrogen for case 1 is 9.6 $/kg H2, for case 2 is 7.9 $/kg H2, and for case 3 is 7.8 $/kg H2.

Adsorption Air-Conditioning for Automotive Applications: A Critical Review

The automotive industry seeks innovative solutions for energy-efficient and sustainable vehicles. Conventional air-conditioning systems consume significant energy and have environmental impacts. Adsorption technology offers a promising alternative with higher energy efficiency and reduced emissions. This review analyzes recent advancements in adsorption air-conditioning for automotive applications, including material selection and system integration. It discusses the benefits, challenges, environmental impact, and waste heat recovery potential of adsorption systems. This review explores emerging trends like hybridization with vapour-compression (VC) systems to optimize energy efficiency and sustainability. By evaluating the existing literature, this review provides insights into thermally driven technologies for automotive air-conditioning.

Lead-free and scalable GeTe-based thermoelectric module with an efficiency of 12.

GeTe-based materials with superior thermoelectric properties promise great potential for waste heat recovery. However, the lack of appropriate diffusion barrier materials (DBMs) limits not only the energy conversion efficiency but also the service reliability of the thermoelectric devices. Here, we propose a design strategy based on phase equilibria diagrams from first-principles calculations and identify transition metal germanides (e.g., NiGe and FeGe2) as the DBMs. Our validation experiment confirms the excellent chemical and mechanical stabilities of the interfaces between the germanides and GeTe. We also develop a process for scaling up the GeTe production. Combining with module geometry optimization, we fabricate an eight-pair module using mass-produced p-type Ge0.89Cu0.06Sb0.08Te and n-type Yb0.3Co4Sb12 and achieve a record-high efficiency of 12% among all reported single-stage thermoelectric modules. Our work thus paves the way for waste heat recovery based on completely lead-free thermoelectric technology.

Machine learning-based multi-objective optimization and thermodynamic evaluation of organic Rankine cycle (ORC) system for vehicle engine under road condition

Organic Rankine cycle (ORC) cooperative multi-objective optimization under dynamic driving cycle is the key to obtain the potential of waste heat recovery of internal combustion (IC) engine. The exhaust waste heat energy of IC engine has the characteristics of complex change and strong fluctuation under actual road conditions. The analysis and optimization of the performance of ORC system under single engine operation has some limitations in evaluating the actual waste heat recovery characteristics. Based on Japan10-15 road condition, this paper builds ORC system for vehicle engine model oriented to driving environment. The interaction between operating parameters of ORC system and thermodynamic and thermal economic performance is analyzed. Based on the operating characteristics of the ORC system, the thermal efficiency and power output per unit heat transfer area (POPA) data driven models are established, and the structural parameters of the network are optimized. Based on the multi-objective optimization algorithm, the thermodynamic performance of ORC system under road condition is optimized. The results show that the ORC system has a maximum thermal efficiency of 2.23% and a maximum POPA of 0.55 kW/m2 under Japan10-15 road condition. In this paper, the performance evaluation and multi-objective optimization results of ORC system under road condition can provide a certain reference for the practical application potential of ORC system.

Techno-economic analysis of large-scale green hydrogen production and storage

Producing clean energy and minimising energy waste are essential to achieve the United Nations sustainable development goals such as Sustainable Development Goal 7 and 13. This research analyses the techno-economic potential of waste heat recovery from multi-MW scale green hydrogen production. A 10 MW proton exchange membrane electrolysis process is modelled with a heat recovery system coupled with an organic Rankine cycle (ORC) to drive the mechanical compression of hydrogen. The technical results demonstrate that when implementing waste heat recovery coupled with an ORC, the first-law efficiency of electrolyser increases from 71.4% to 98%. The ORC can generate sufficient power to drive the hydrogen's compression from the outlet pressure at the electrolyser 30 bar, up to 200 bar. An economic analysis is conducted to calculate the levelised cost of hydrogen (LCOH) of system and assess the feasibility of implementing waste heat recovery coupled with ORC. The results reveal that electricity prices dominate the LCOH. When electricity prices are low (e.g., dedicated offshore wind electricity), the LCOH is higher when implementing heat recovery. The additional capital expenditure and operating expenditure associated with the ORC increases the LCOH and these additional costs outweigh the savings generated by not purchasing electricity for compression. On the other hand, heat recovery and ORC become attractive and feasible when grid electricity prices are higher.

Compositing effects for high thermoelectric performance of Cu2Se-based materials

Thermoelectric materials can realize direct conversion between heat and electricity, showing excellent potential for waste heat recovery. Cu2Se is a typical superionic conductor thermoelectric material having extraordinary ZT values, but its superionic feature causes poor service stability and low mobility. Here, we reported a fast preparation method of self-propagating high-temperature synthesis to realize in situ compositing of BiCuSeO and Cu2Se to optimize the service stability. Additionally, using the interface design by introducing graphene in these composites, the carrier mobility could be obviously enhanced, and the strong phonon scatterings could lead to lower lattice thermal conductivity. Ultimately, the Cu2Se-BiCuSeO-graphene composites presented excellent thermoelectric properties with a ZTmax value of ~2.82 at 1000 K and a ZTave value of ~1.73 from 473 K to 1000 K. This work provides a facile and effective strategy to largely improve the performance of Cu2Se-based thermoelectric materials, which could be further adopted in other thermoelectric systems.

A synergistic multi-objective optimization mixed nonlinear dynamic modeling approach for organic Rankine cycle (ORC) under driving cycle

Organic Rankine cycle (ORC) synergistic multi-objective optimization is the key to obtain the actual waste heat recovery potential under dynamic driving cycle. The ORC operation shows uncertainty and hysteresis under the disturbance of variable high temperature waste heat source. In this paper, a synergistic multi-objective optimization mixed nonlinear dynamic modeling approach is proposed by deeply integrating data selection, feature dimensionality reduction, integrated system, neural network modeling mechanism, ensemble learning mechanism and synergistic multi-objective optimization. Compared with direct modeling, the nonlinear dynamic modeling approach can reduce the data volume by 27.65 % on average. The decision variables and construction time are reduced at least by 69.1 % and 24.26 % on average, respectively. Generalization ability is improved by at least 28.14 % on average. Taking thermodynamic performance, economic performance, thermoeconomic performance and environmental impact as optimization objectives, a synergistic multi-objective optimization of ORC comprehensive performance under driving cycle is carried out. The optimal emissions of CO2 equivalent (ECE) will suppress the optimal power output of per unit heat transfer area (POPA) to a certain extent. A decrease in optimal ECE is accompanied by an increase in optimal electricity production cost. The approach proposed in this paper can provide new ideas and solutions for ORC dynamic modeling and synergistic multi-objective optimization under road conditions.

Assessment of waste heat recovery potential in greenhouse ventilation systems using dynamic pinch analysis

A major factor contributing to the energy efficiency of greenhouses is ventilation losses. The present paper aims at developing a systematic method based on dynamic Pinch Analysis (PA) approach to investigate the heat recovery potential of greenhouse ventilation systems. The heat integration possibility of ventilation waste heat is studied over the course of a year for a greenhouse located in Saskatoon, Canada. The analysis is conducted for a system including a heat pump connected to seasonal heat storage, and an air handling unit. In the first step, a greenhouse climate model is developed to provide the required input data for the PA (i.e., greenhouse thermal and dehumidification loads). Then, a clustering technique is proposed to reduce the heat integration scenarios to a manageable size by limiting the analysis to a set of typical days representing the whole year. Finally, dynamic energy targeting is performed using the composite curves concept of PA to find the maximum heat recovery and minimum energy requirements of the greenhouse. The results showed 55% heat recovery potential for the greenhouse under study. Application of the proposed method can help to find realistic estimations on feasible heat recovery ratios and utility and equipment costs in the early stages of the greenhouse design.

Low-temperature waste heat recovery from internal combustion engines and power output improvement through dual-expander organic Rankine cycle technology

Energy, being the driving force behind the economic development, there has been continued efforts to develop alternative energy-utilisation strategies. Due to lower heat utilisation efficiency of internal combustion engines, they provide a huge potential of waste heat recovery by organic Rankine cycle technology. The present work is devoted towards the waste heat recovery from engine coolant. This study provides the complete thermodynamic analyses, cycle configuration, system size design and selection of working fluid for the development of the stand-alone engine-coolant based ORC. The system performance at fluctuating flow of jacket cooling water with engine speed and load is investigated. The effect of changing mass flow rate of heat source, which leads to varying heat input available to be recovered from the engine coolant is considered with fixed temperature of 90°C. Methodology has been presented to enhance the cycle thermal efficiency with the use of dual expander at part load conditions, by parallelising the flow to attain the favourable input conditions for the expanders over wider variation of heat input. R245fa showed the highest performance characteristics giving cycle efficiency and work output of 4.72% and 0.97 kW, respectively at dual expander operating mode. The control strategy to switch to the dual expander is based upon its evaluation of actual isentropic efficiency and optimum working range. The present study establishes the importance of considering the continually varying heat-input conditions and its effect on the key components, unlikely assuming its performance to be constant. And to capture their varying characteristics and integrate its effect on the overall system to provide operational controlling at off-design conditions to attain flatter efficiency at wider operating conditions for system optimisation.

Evaluation on the waste heat recovery potential of thermoacoustically-driven cryocoolers for solid oxide fuel cells

Heat accumulation significantly affects the long-term stability of solid oxide fuel cell (SOFC) during operation. Harvesting the waste heat for additional applications can provide dual benefits. A novel hybrid system coupling a thermoacoustically-driven cryocooler (TDC) to a SOFC is proposed, aiming to recover the released waste heat for additional cooling production. Performance indicators assessing the hybrid system are derived by considering a variety of irreversible losses, from which the generic performance properties for such a hybrid system are determined. In comparison to a standalone SOFC system, the effectiveness and advantage of the combined system are shown. It is found that the maximum power density, the corresponding energetic efficiency and the exergetic efficiency of the proposed hybrid system are improved compared to that of the standalone SOFC system. Extensive parametric studies indicate that an increase in working temperature, working pressure of the SOFC, engine stage number or cooling temperature in the TDC improve the proposed system performance, while increasing the heat transfer coefficient worsens the performance.

Assessing the waste heat recovery potential of liquid organic hydrogen carrier chains

Proper thermal management can improve the efficiency of hydrogen storage chains based on liquid organic hydrogen carriers (LOHC). The energy and exergy efficiencies of 24 LOHC chains, which are differentiated by two hydrogen sources (SEL: hydrogen from electrolyzer and SINDU: industrial by-product), three hydrogen consumers (CPEMFC: proton exchange membrane fuel cell, CSOFC: solid oxide fuel cell, and CINDU: industrial consumer), and four LOHC pairs are calculated based on thermodynamic modeling. Possible strategies for the heat integration between the heat sources (including hydrogenation heat, heat generated by hydrogen consumer, and the high-temperature LOHC fluids) and the heat sinks (including LOHC preheating, hydrogen preheating, dehydrogenation, and external heating purposes) are designed for these chains. In the four selected LOHC pairs, dibenzyltoluene (DBT) is found to be the most favorable LOHC pair for the implementation of WHR strategies, mainly because of low heat demand for preheating (8.9% of the stored hydrogen energy) and a high dehydrogenation rate. The WHR strategies significantly improve the energy efficiency of LOHC chains by up to 21.7% points for the chains with CINDU and 40.8% points for chains with CSOFC or CPEMFC, which makes LOHC chains more efficient than traditional compressed or liquid hydrogen chains in several scenarios, i.e., the DBT chain with CPEMFC have the highest energy efficiency (70.4% for SEL/69.5% for SINDU), while the DBT chain with SINDU and CSOFC has the highest exergy efficiency (60.6%). For the remaining combinations of the remaining hydrogen sources and consumers, the compressed hydrogen chains are the most efficient.