Waste Heat Recovery Techniques Research Articles

Performance Analysis of Lake Water Cooling Coupled with a Waste Heat Recovery System in the Data Center

Data centers (DCs) require continuous cooling throughout the year and produce a large amount of low-grade waste heat. Free cooling and waste heat recovery techniques are promising approaches to reduce DC energy consumption. Although previous studies have explored diverse waste heat utilization strategies, there is a significant gap in combining waste heat recovery with lake water cooling in DCs. Therefore, this study proposed a system integrating lake water cooling with waste heat recovery for DCs. To evaluate the energy-saving performance of the suggested system, the influence of waste heat recovery locations and volumes has been investigated. An analysis of the improvement in system parameters is also conducted. The study’s findings highlight that targeted recovery of waste heat from sources like chilled water or air in server rooms can significantly reduce the cooling energy demand of the system. The results show that recovering heat from the return air of IT equipment can yield a remarkable power usage effectiveness (PUE) and coefficient of performance (COP) of 1.19 and 10.17, and the energy consumption of the cooling system is reduced to 10.06%. Moreover, the outcomes reveal the potential for substantial energy savings of up to 26.05% within the proposed system by setting the chilled water and air supply temperatures to 16 and 20 °C, respectively.

A Comprehensive Review of Thermal Management in Solid Oxide Fuel Cells: Focus on Burners, Heat Exchangers, and Strategies

Solid Oxide Fuel Cells (SOFCs) are emerging as a leading solution in sustainable power generation, boasting high power-to-energy density and minimal emissions. With efficiencies potentially exceeding 60% for electricity generation alone and up to 85% when in cogeneration applications, SOFCs significantly outperform traditional combustion-based technologies, which typically achieve efficiencies of around 35–40%. Operating effectively at elevated temperatures (600 °C to 1000 °C), SOFCs not only offer superior efficiency but also generate high-grade waste heat, making them ideal for cogeneration applications. However, these high operational temperatures pose significant thermal management challenges, necessitating innovative solutions to maintain system stability and longevity. This review aims to address these challenges by offering an exhaustive analysis of the latest advancements in SOFC thermal management. We begin by contextualizing the significance of thermal management in SOFC performance, focusing on its role in enhancing operational stability and minimizing thermal stresses. The core of this review delves into various thermal management subsystems such as afterburners, heat exchangers, and advanced thermal regulation strategies. A comprehensive examination of the recent literature is presented, highlighting innovations in subsystem design, fuel management, flow channel configuration, heat pipe integration, and efficient waste heat recovery techniques. In conclusion, we provide a forward-looking perspective on the state of research in SOFC thermal management, identifying potential avenues for future advancements and their implications for the broader field of sustainable energy technologies.

A Review of Fuel Cell Powertrains for Long-Haul Heavy-Duty Vehicles: Technology, Hydrogen, Energy and Thermal Management Solutions

Long-haul heavy-duty vehicles, including trucks and coaches, contribute to a substantial portion of the modern-day European carbon footprint and pose a major challenge in emissions reduction due to their energy-intensive usage. Depending on the hydrogen fuel source, the use of fuel cell electric vehicles (FCEV) for long-haul applications has shown significant potential in reducing road freight CO2 emissions until the possible maturity of future long-distance battery-electric mobility. Fuel cell heavy-duty (HD) propulsion presents some specific characteristics, advantages and operating constraints, along with the notable possibility of gains in powertrain efficiency and usability through improved system design and intelligent onboard energy and thermal management. This paper provides an overview of the FCEV powertrain topology suited for long-haul HD applications, their operating limitations, cooling requirements, waste heat recovery techniques, state-of-the-art in powertrain control, energy and thermal management strategies and over-the-air route data based predictive powertrain management including V2X connectivity. A case study simulation analysis of an HD 40-tonne FCEV truck is also presented, focusing on the comparison of powertrain losses and energy expenditures in different subsystems while running on VECTO Regional delivery and Longhaul cycles. The importance of hydrogen fuel production pathways, onboard storage approaches, refuelling and safety standards, and fleet management is also discussed. Through a comprehensive review of the H2 fuel cell powertrain technology, intelligent energy management, thermal management requirements and strategies, and challenges in hydrogen production, storage and refuelling, this article aims at helping stakeholders in the promotion and integration of H2 FCEV technology towards road freight decarbonisation.

Multi-objective optimization and thermo-economic analysis of an enhanced compression-absorption cascade refrigeration system and ORC integrated system for cooling and power cogeneration

Waste heat recovery techniques can greatly improve the energy efficiency and relieve the energy crisis. The integration of compression-absorption cascade refrigeration system (CACRS) and Organic Rankine Cycle (ORC) can achieve cooling and power cogeneration utilizing waste heat. However, the simultaneous optimization of integrating configuration and operating parameters has not been considered in recent studies, neglecting the complex interactive relationship within the integrated system consequently. To overcome these limitations, an enhanced CACRS-ORC integrated system, containing more coupling possibilities and more routes in driving the integrated system with waste heat, is proposed and investigated in this paper. To examine the trade-off in the economic and thermodynamic performances, a multi-objective optimization-based method, aiming at the simultaneous minimization of the total annualized cost (TAC) and the total exergy destroy (Exdestroytotal), is developed to determine the optimal configuration and operating parameters of the integrated system. The derived Pareto solutions reveal the contradictory relationship between the two objectives, and the thermo-economic analysis is executed to show the impact of system configuration and operating parameters on economy and thermodynamics. Sensitive analysis is also performed to reveal the effects of key parameters on the structural configuration and thermo-economic performances.

Integration of LiBr/H2O Absorption Heat Pump and Absorption Heat Transformer in Total Site Heat Integration

Energy efficiency is one of the main solutions to reduce CO2 emissions in the energy sector and improve primary energy intensity. Energy savings are at the centre of the numerous advantages of energy efficiency and connect to many other economic, social and environmental advantages. Total Site Heat Integration (TSHI) was introduced to maximise the heat recovery from various processes through a centralized utility system. Heat pump using absorption cycle has been identified as one of the waste heat recovery techniques. The challenges of heat pumps applications include limited temperature applications and long payback periods. However, these problems can be tackled by proper design and suitable types of heat pumps considerations. This paper integrates two different kinds of absorption cycle heat pump which are absorption heat pump (AHP) and absorption heat transformer (AHT) into the context of TSHI. This integration is able to reduce the industrial waste heat and generate quality steam. The heat generation of AHP and AHT are estimated based on the enthalpy of working fluid pair of water-lithium bromide. A case study is done to compare and verify the proposed methodology. Economic analysis is performed to compare the different integration approaches of AHP and AHT. Results showed that the integration of hybrid AHP and AHT contribute to the highest annual saving (21,351 USD/y) of utility cost compared to 12,356 USD/y for AHP system and 9,119 USD/y for AHT system.

Investigate the technical-economical feasibility of utilizing the available industrial waste thermal energy in Oman

The rapid increasing in energy demand is starting to create a burden on Oman due to its unrenewable sources of energy. Oman is formulating policies to promote using renewable energy technologies and/or minimize energy losses in industrial sectors through using waste heat recovery techniques. In this study, waste thermal energy data of five industrial companies were used to evaluate the performance of an Organic Rankine Cycle (ORC) unit. It has been found that the ORC technology might become a technically feasible solution to enhance the performance of industrial thermal cycles in Oman by converting the available waste thermal energy into an additional electric power. The level of enhancement is found to be affected (directly proportional relationship) by the range of temperature and mass flow rate of the available thermal source. With respect to environment effect, high performance was achieved at the first and the last quarters of the year where water coolant temperature is low during winter seasons, while the performance deteriorated is summer as result of high water coolant temperature. Unfortunately, using ORC at Sharq Sohar Steel Rolling Mills is inapplicable, i.e. the required parasitic load was greater than the work output of the expander. The economic feasibility calculations showed that using ORC unit at ACWA Power Barka I would be an economically feasible project in terms of payback period of approximately 6 years and revenue percentage of 85%. In contrast, the available waste heat at Areej Vegetable Oil & Derivatives cannot be economically recovered to electric power as a result of its long time-span of payback period.

Design and optimisation of an advanced waste heat cascade utilisation system for a large marine diesel engine

Growing energy shortages severely restricting the sustainable development of human beings, improving energy efficiency has become an urgent issue. To improve energy efficiency, the dual-pressure organic Rankine cycle, which is an efficient waste heat recovery technique for ships, has received increasing attention. Most researchers have investigated the dual-pressure organic Rankine cycle with pure working fluids, which do not yield the best thermodynamic and economic performance. In addition, some low-grade waste heat sources in the engine have been neglected. To completely recover the waste heat energy of marine engines, a novel waste heat recovery technique with a dual-pressure organic Rankine cycle system, desalination plant, and two-bed regenerative adsorption refrigeration device is presented for recovering residual heat from the exhaust gas, jacket water, charge air, and lubricating oil. Based on a comparison of the thermodynamic performance, safety, and environmental effects, the zeotropic working fluid pair dimethyl carbonate/perfluoropropane is selected. The mathematical model of the proposed integrated system is evaluated to ensure accuracy, and its critical parameters are analysed based on its thermodynamic and economic performance. A multi-objective artificial bee colony algorithm is adopted to optimise the system. The results show that the proposed integrated system can recover 354.65 kW net power and increase the thermal efficiency by 4.2% on average; at the most frequently used engine load, a refrigeration capacity of 88 kW and a fresh water rate of 146 kg/h are achieved. This work promotes the development of the energy recycling.

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.

Modeling and control of a waste heat recovery system for integrated powertrain design optimization

Abstract The growing demand for increased vehicle efficiency has led to the introduction of waste heat recovery techniques in vehicle powertrains, with the organic Rankine cycle as the most interesting technique for automotive applications. In order to integrate the design of the waste heat recovery system into the design optimization of the full powertain, a novel modeling approach is suggested for capturing the key dynamics of a waste heat recovery system with low computational effort and number of design parameters, and which is scalable with the individual components of the cycle. The model is compared with a detailed finite volume model for a given organic Rankine cycle. Secondly, the organic Rankine cycle is integrated into a parallel hybrid vehicle model, and an optimization routine is proposed for obtaining the optimal control trajectories for the powertrain over a drive cycle. The main purpose of the waste heat recovery model designed in this paper in combination with the proposed optimization algorithm is to be used for powertrain design optimization studies.

Theoretical and experimental research on the influence of initial temperature on the flammability of hydrocarbon-CO2 mixture using in organic Rankine cycle

As an effective waste heat recovery technique, the hydrocarbon-CO2 mixture based Rankine cycle is always operating on a specific temperature, which has a noticeable influence on flammability limits. Thus it is critical to research flammability limit of hydrocarbon-CO2 at various initial temperatures. Focusing on the hydrocarbon-CO2 mixture, this paper first measured its flammability limits at different initial temperatures using an experimental setup based on the ASTM E681-09. Results have shown that lower flammability limit decreases with the elevating initial temperatures while upper flammability limit increases, therefore the flammable zone expands leading to higher potential dangers. Moreover the expansion values of flammable zone from 30 °C to 70 °C have decreased by nearly 0.3 vol% with the dilute concentration changing from 0 to 0.9. A linear relationship between temperature and flammability limits of hydrocarbon-CO2 mixture has been proposed based on thermal theory and verified with experimental values. At the same time, a comprehensive method based on calculated adiabatic flame temperature theory was presented to predict the flammability limit at different temperatures with higher accuracy. The mean relative deviation between the predicted results and observed ones is 2.76% at upper flammability limit and 1.71% at lower flammability limit in the temperature range examined.

High-performance near-field thermophotovoltaics for waste heat recovery

The US industries reject nearly 20–50% of the consumed energy into the environment as waste heat. Harvesting this huge amount of heat can substantially improve the energy usage efficiency. For waste heat in the medium temperature range (~ 500–900K), traditional solid-state waste heat recovery techniques like thermoelectric generators and thermophotovoltaics (TPVs) are still suffering from relatively low efficiency or power density. In this work, we analyze a near-field TPV system consisting of a plasmonic emitter (indium tin oxide) and a narrow-bandgap photovoltaic cell (InAs) that are brought to deep sub-wavelength distances for high-efficiency and high-power-density waste heat recovery. We show that despite the inclusion of realistic nonradiative recombination rates and sub-bandgap heat transfer, such a near-field TPV system can convert heat to electricity with up to nearly 40% efficiency and 11W/cm2 power density at a 900K emitter temperature, because of the spectral reshaping and enhancement by the thermally excited surface plasmons and waveguide modes. Thus, we show that for waste heat recovery, near-field TPV systems can have performances that significantly exceed typical thermoelectric systems. We propose a modified system to further enhance the power density by using a thin metal film on the cell, achieving a counterintuitively “blocking-assisted” heat transfer and power generation in the near-field regime.

Exhaust Energy Recovery with Turbo Compounding in a Heavily Downsized Engine

Large amount of heat energy is wasted in Internal Combustion (IC) engine through the exhaust manifold, coolant, convective and radiative heat transfer. Significant amount of thermal energy waste occurring at the exhaust manifold of the IC engine can be recovered using various contemporary heat recovering techniques. The paper presented the viability of using turbo compounding waste heat recovering technique in recovering a significant amount of waste energy occurring at the exhaust of a heavily downsized engine. Electric turbo compounding (ETC) simulation using Ford Eco-Boost base line engine with modification using Hy-Boost modelled with AVL Boost software was carried out for the analysis. The simulation results show a 3% reduction in Brake Specific Fuel Consumption (BSFC), 0.5 bar Brake Mean Effective Pressure (BMEP) increase and up to 2 kW of power output were realized at engine speed of 2500 rpm. The result clearly indicates the effectiveness, viability and commercialization potentials of this waste heat recovery technique.

Improvement in Thermal Efficiency of a CI Engine Using a Waste Heat Recovery Technique

A big portion of the heat supplied to an internal combustion (IC) engine is not converted into work and wasted through the exhaust gases in surroundings. If this heat is recovered or used by some means then improvement can be obtained in engine’s overall efficiency. In the present work, an experimental work is carried out to study the effect of waste heat recovery of exhaust gas in a Compression Ignition (CI) engine. The results show that considerable reduction in engine fuel consumption can be obtained with the help of exhaust heat recovery through a heat exchanger. A significant amount of heat of exhaust gases can be recovered by vaporization of fuel using a heat exchanger.

A review of data center cooling technology, operating conditions and the corresponding low-grade waste heat recovery opportunities

Abstract The depletion of the world's limited reservoirs of fossil fuels, the worldwide impact of global warming and the high cost of energy are among the primary issues driving a renewed interest in the capture and reuse of waste energy. A major source of waste energy is being created by data centers through the increasing demand for cloud based connectivity and performance. In fact, recent figures show that data centers are responsible for more than 2% of the US total electricity usage. Almost half of this power is used for cooling the electronics, creating a significant stream of waste heat. The difficulty associated with recovering and reusing this stream of waste heat is that the heat is of low quality. In this paper, the most promising methods and technologies for recovering data center low-grade waste heat in an effective and economically reasonable way are identified and discussed. A number of currently available and developmental low-grade waste heat recovery techniques including district/plant/water heating, absorption cooling, direct power generation (piezoelectric and thermoelectric), indirect power generation (steam and organic Rankine cycle), biomass co-location, and desalination/clean water are reviewed along with their operational requirements in order to assess the suitability and effectiveness of each technology for data center applications. Based on a comparison between data centers' operational thermodynamic conditions and the operational requirements of the discussed waste heat recovery techniques, absorption cooling and organic Rankine cycle are found to be among the most promising technologies for data center waste heat reuse.

열전소자를 이용한 자동차 엔진 배기 폐열 회수 시스템 해석 모델 개발

최근 엔진 효율 향상을 위하여 열전 소자를 이용한 자동차 엔진 폐열 회수 기술이 주목 받고 있다. 열전소자 해석 모델링은 많이 개발 되었으나, 특정한 시스템 해석 모델과 함께 적용된 사례는 찾아보기 어렵다. 따라서, 본 연구에서는 열전소자를 이용하여 디젤 엔진의 배기 폐열 에너지 회수율을 평가할 수 있는 해석 모델을 1-D 상용 프로그램인 AMESim을 이용하여 개발하였다. 개발한 열전소자 해석 모델은 다양한 소자 종류에 따른 열전 발전 효율 및 폐열 회수율 평가가 가능한 모델이며, 디젤 엔진 해석 모델은 현재 상용화된 모든 디젤 엔진을 모사할 수 있는 모델이다. 여러 운전 조건에서 디젤 엔진의 폐열로부터 하나의 열전소자를 사용하여 회수 가능한 에너지는 약 544.75W이고, 전기로 변환될 수 있는 동력은 약 40.4W이었다. 본 연구에서 개발한 해석 모델은 같은 해석 프로그램에서 연동하여 해석을 용이하게 수행할 수 있기에 추후 열전소자를 이용한 디젤 엔진의 배기 폐열 회수 시스템 개발 시 회수율을 예상하고 시스템 최적화를 수행할 수 있는 방법을 제공할 것으로 기대된다. 【Recently, the waste heat recovery technique using thermoelectric generator (TEG) in automotive engine has emerged to improve thermal efficiency in commercial vehicle. It is not difficult to recognize the numerous attempts that have been made to develop the TEG simulation model, but it is hard to find the model in conjunction with a particular heat engine system. In this study, 1-D commercial software AMESim was used to develop a computational model that can assess waste heat recovery from a diesel engine exhaust using TEG. The developed TEG simulation model can be used for evaluating the TEG performance of various types of TE module, and the diesel engine model can simulate any type of on and off-road diesel engines. The simulation results demonstrated that approximately 544.75W could be recovered from the engine exhaust and 40.4W could be directly converted into electricity using one TE module. The models developed in this study can be easily coupled with each other in the same computational program; thus, the models are expected to provide a viable tool for developing and optimizing a TEG waste heat recovery system in an automotive diesel engine.】

Optimization of a methane autothermal reforming-based hydrogen production system with low CO2 emissions

The aim of this work is to develop a hydrogen production system with respect to saving energy and reducing carbon dioxide. Methane and carbon dioxide are major feedstocks of an autothermal reformer (ATR) and a CO2 reformer, respectively. The waste heat recovery technique is applied to build a stand-alone ideal heat-integrated system. The proposed system configuration and optimal operating conditions are verified with the Aspen HYSYS® simulator.

Review on Waste Heat Recovery Techniques in Air Conditioning Application

The world today is facing a lot of difficulties in energy management and energy saving technologies is the need of the hour. This paper reviews the various techniques for heat recovery from Air Conditioning systems. The types of heat recovery techniques under consideration are: Fixed Plate, Heat Pipe, Rotary Wheel and Run-Around. A comparison of the development of these technologies has been done. For performance rating the efficiency of technology is considered.