Waste Thermal Energy Research Articles

Experimental analysis and performance of refinery fuel gas on lean and rich fuel–air premixed combustion

Refinery fuel gas (RFG) is a blend of gas streams produced as by-products in various refinery processes. Large amounts of RFG are burning around the clock in the air with thermal energy waste and adverse effects on the environment. The present work investigates experimentally the performance of different compositions of RFG from lean to rich fuel–air premixed combustion, with focus on an efficient and low-emission combustion for its heat recovery. Radiant and porous media burners are the combustion technologies used. For the radiant burner, fuel compositions are propane and ethane with an average ethane ratio of 5%, 10%, and 15% (E05, E10, E15 respectively), which are contrasted with pure propane and liquefied petroleum gas (LPG). The pure gases fluxes are fixed as 1 and 2 m3/h for low and high flame configurations, respectively. The lean fuel–air flames investigated are stable for all ethane ratios with low carbon monoxide (CO) and nitrate oxides (NOx) emissions. Maximum temperature is given by pure propane flame (besides LPG), followed by E05, E10 and E15, for both flame configurations. Then, the radiation heat flux of ethane mixtures exhibits a reduction in comparison with LPG. For the porous media burner, lean and rich fuel–air mixture composed by natural gas (NG, 97% methane) and representative flue samples of 55% (C1) and 70% (C2) methane concentration are tested. The C1 and C2 flue samples present high combustion temperatures, showing a positive swap from NG. The NG rich-fuel combustion exposes high hydrogen conversion (27%) at high equivalence ratio (ϕ=1.8). Finally, for both burners lean fuel–air premixed combustion shows high combustion efficiencies, 74.8% with E05 and 80.7% with C1 flue sample.

Service properties of porous liquid glass concrete

The article presents studies’ results of cementless lightweight concretes based on porous granular aggregate. Lightweight concrete components are specially synthesized from mixtures containing liquid sodium glass and thermal energy waste with various fineness. Thermal hardening of a matrix based on liquid glass and technogenic fillers at a temperature of 350ºС provided heat-insulating concrete with 480 kg/m3density and compressive strength of 4.7 MPa. The aim of the work is to study operational stability of lightweight concrete from genetically related components. Durability of lightweight concrete was evaluated in terms of hydro physical properties, resistance to frost and salt aggression, and cyclic heating. Methods of physical and mechanical testing of concrete have been used in the work. X-ray phase analysis and electron microscopy were used to study materials’ composition and structure. The results of complex tests showed stability of the structure of liquid glass concrete based on porous aggregate to the impact of operational factors. The lightweight concretes developed are characterized by a softening coefficient of 0.81; they withstood 50 cycles of alternating freezing and thawing, 20 cycles of cyclic exposure at a temperature of 1050ºС and 20 thermal cycles at a temperature of 250ºС; staying in aggressive sulfate and chloride magnesium solutions.

Maximum Power Extraction Control Algorithm for Hybrid Renewable Energy System

In this research, a modified fractional order proportional integral derivate (FOPID) control method is proposed for the photovoltaic (PV) and thermoelectric generator (TEG) combined hybrid renewable energy system. The faster tracking and steady-state output are aimed at the suggested maximum power point tracking (MPPT) control technique. The derivative order number (µ) value in the improved FOPID (also known as PIλDµ) control structure will be dynamically updated utilizing the value of change in PV array voltage output. During the transient, the value of µ is changeable; it’s one at the start and after reaching the maximum power point (MPP), allowing for strong tracking characteristics. TEG will use the freely available waste thermal energy created surrounding the PV array for additional power generation, increasing the system’s energy conversion efficiency. A high-gain DC-DC converter circuit is included in the system to maintain a high amplitude DC input voltage to the inverter circuit. The proposed approach’s performance was investigated using an extensive MATLAB software simulation and validated by comparing findings with the perturbation and observation (P&O) type MPPT control method. The study results demonstrate that the FOPID controller-based MPPT control outperforms the P&O method in harvesting the maximum power achievable from the PV-TEG hybrid source. There is also a better control action and a faster response.

Thermodynamic optimization of a linear thermomagnetic motor

Thermomagnetic motors can be applied to recover low-grade thermal energy waste and convert it into mechanical energy, therefore, used as an energy harvester. The present work proposes a mathematical model to simulate the heat transfer and the thermodynamic cycle of a linear thermomagnetic motor coupled to a spring mechanism. The simulation results are the input information in a subroutine to optimize the motor design based on two objective functions: to minimize the total entropy generated and to minimize the back work ratio, defined as the ratio between the pumping power and the total produced power. The mathematical model solves coupled the energy equations for the fluid and solid phases, and the entropy generation model includes four contributions: interstitial heat transfer (finite temperature difference), axial conduction in the fluid and solid phases, and viscous dissipation. Gadolinium is used as soft magnetic material due to the availability of properties data. Four design and operating conditions constraints are taken into account: heat exchanger length, spring constant, mass flow rate, and warm stream temperature (heat source), and their optimized values are, respectively, 52 mm, 1560 N/m, 80 kg/h at any warm stream temperature ranging from 310–330 K. At these combinations, the optimum thermomagnetic motor is able to produce a net power of 5.00 ± 0.15 W with a minimum back-work ratio of about 12%. The proposed methodology can be used to optimize the design of novel thermomagnetic motors or to optimize geometric parameters and operating conditions of state-of-the-art concepts.

Model Parameterized Assessment of a Thermal Storage Unit for Engine Oil Warm-up Improvement

Despite the attention paid to components downsizing and down weighting, as well as to combustion control and exhaust gases after-treatment, friction reduction remains a promising area of intervention when it comes to the reduction of the environmental impact of internal combustion engines. The larger gain must be sought at cold starts, when the viscosity of the lubricant oil is higher and does not allow proper friction reduction. Moreover, during the first phases of engine operation, the metallic masses are not yet warm and do not contribute to the thermal stabilization of the lubricant. Further consequences of unfavourable thermal conditions are increased specific fuel consumption and pollutant emissions. Proper thermal management could effectively speed up the reaching of the design operating temperature of the oil and positively affect both homologation and on-road operation. The abundance of waste thermal energy during normal operation supports the option of on-board thermal storage for faster oil heating: water, heated by exhaust gases or residual thermal energy from previous use or by a combination of the two, can be stored inside a thermally insulated tank and serve as heating fluid in a dedicated water/oil heat exchanger. The paper presents a model based evaluation of this opportunity. The model has been validated thanks to an experimental activity carried out on an IVECO 3.0 L light-duty diesel engine, during a transient cycle (i.e., homologation one) reproduced on a dynamometric test bench. Different configurations in terms of hot storage volume, hot storage initial temperature, and the flow rate of the hot water during operation have been studied, producing optimized values for the hot water and storage unit design.

Seasonal performance and climatic adaptability of a solar-powered microchannel membrane-based absorption refrigeration system

Microchannel membrane-based absorption refrigeration system (MMARS) has vast potential to satisfy the increasing cooling demand by utilizing renewable and waste thermal energy. To maximize its potential for future large-scale applications, the geometries of the MMARS were optimized for the first time to obtain the lowest system cost under various weather conditions and cooling demands in different climate zones of China. After optimization, Kunming (mild region) has the highest levelized cooling demand cost of 0.2710 $/kWh because of its high initial cost, while Beijing (cold region) has the lowest cost of 0.1508 $/kWh due to its rich solar energy to reduce the operating cost and sufficient cooling demand to levelize the initial cost. It is worth noting that if only natural gas is counted in energy consumption, Kunming, with rich solar energy, achieves the highest seasonal COP of 2.654, but Hong Kong (hot summer and warm winter region) with insufficient solar energy only gets 1.318 because of the low proportion (48.84%) of solar energy in its heat sources. This paper provides a seasonal performance-based geometries optimization of the MMARS and studies its climatic adaptability in different climate zones, facilitating the reasonable design and application of efficient and compact absorption refrigeration systems.

Application of Thermal Energy Harvesting from Photovoltaic Panels

This paper describes a newly developed system for harvesting thermoelectric energy from photovoltaic panels. This system helps to power monitoring systems for photovoltaic panels (PVs) in locations where there is no energy source using waste thermal energy from PVs exposed to the sun’s rays. In the study described here, the thermal energy from a PV panel was captured and transferred to a thermoelectric generator (TEG). A temperature gradient was created by reducing the temperature using an aluminium heat sink in ambient weather conditions. This temperature gradient was used to generate electricity via two TEGs. In field tests carried out in April, in Aksaray province in central Turkey, the maximum temperature gradient due to solar radiation was measured as 21.08 °C. The harvested energy was increased to a usable level of 4.1 V using a DC-to-DC converter and stored in a li-ion rechargeable battery. The maximum charge current level of the battery was 147 µA. The maximum harvested energy was 458.64 mW, and a stable level of around 350 mW was achieved. The experimental operation of the prototype system was carried out in stable weather conditions; however, weather and climatic conditions greatly affect levels of energy harvested as a result of changing temperature gradients. The energy obtained with the prototype may reduce the battery maintenance costs of PV monitoring systems and lead to the development of new such systems which cannot presently be used due to a lack of energy.

Coupled thermo-electric-mechanical modeling of hybrid thermoelectric-piezoelectric energy harvester

If piezoelectric (PE) layers are bonded on the heat sink of thermoelectric (TE) generators, waste thermal and wind energy can be simultaneously converted into electricity. This study investigates the coupled thermo-electric-mechanical behavior and the effect of material parameters and structure dimensions on the energy collection performance of this hybrid TE-PE system. The model is based on Hamilton’s principle to obtai the governing equations of hybrid system. Numerical results show that output powers of TE part and PE part could be improved simultaneously when thermal conductivity of heat sink increases. If the thermal conductivity of TE material is reduced by 20%, the output power of PE part could be reduced by 7.39%, and the output power of TE part could be increased by 44.7%. With a specific length of heat sink, the output power of PE part can be increased by 41% and the output power of TE part can be reduced by 0.72% compared to that without changing the hybrid system size. Therefore, it is possible to adjust the material parameters and structure dimensions to achieve higher performance of hybrid TE-PE system. The results obtained here may offer valuable references for optimal design of hybrid TE-PE energy harvester.

Towards a digital twin approach – Experimental analysis and energy optimization of a multi-bed adsorption system

An adsorption chiller system is one of the most promising technologies that utilize waste thermal energy to simultaneously produce cooling and potable water. However, the energy utilization optimization and detection of desiccant’s sorption capacity degradation are two unresolved issues that have severely impeded the development and commercial applications of adsorption chiller technologies. This study is pioneered to develop a digital twin platform specifically designed for an experimental four-bed two-evaporator adsorption chiller system prototype. Leveraging this platform, system monitoring, performance prediction, and optimization functions are achieved. Relying on the monitoring function, the digital twin can detect the capacity degradation of desiccant-coated heat exchangers. By employing the prediction and optimization functions, the application performance of the adsorption chiller system under varying ambient and load conditions can be simulated and optimized under real-time operating conditions. Additionally, this work projects a first-time experimental parametric study analysis for a four-bed two-evaporator adsorption chiller system prototype under a heat recovery scheme that considers fourteen operating parameters. Key results revealed that COPth reaches 0.68 when the cycle time is 2240 s. Case studies also showed that the adsorption chiller system can yield significant energy-saving performance for climatic conditions in Malaysia and Saudi Arabia. The proposed digital twin optimization method demonstrates that COPth is enhanced by 8.5 %, 9.5 %, and 8.5 %, respectively. In contrast to the conventional method, optimizing the adsorption chiller’s performance through the digital twin platform enables a reduction of the annual electricity consumption by up to 10.3 %.

Waste Heat Driven Integrated Membrane Distillation for Concentrating Nutrients and Process Water Recovery at a Thermophilic Biogas Plant

To efficiently utilize low-concentrate digestate nutrients, further treatment is needed to decrease their volume, recover process water, and increase nutrient concentrations. Membrane distillation (MD) is a thermally driven process that is advantageous due to its ability to harness low-grade waste heat to treat highly complex wastewater streams. This study assessed the techno-economic performance of integrating MD for two-fold concentrations of nutrients and the recovery of process water from digestate at a thermophilic biogas plant. Thermal assessment showed that the recovered waste heat from flue gas and digestate fully met the thermal energy demand of MD and saved 20% of boiler energy by heating incoming slurry. The permeate flux from MD was 3.5 L/(m2h) and 3.1 L/(m2h) at 66 °C and 61 °C digestate inlet temperatures during winter and summer, respectively. With internal heat recovery, the specific heat demand for MD was 80 kWh/m3 and 100 kWh/m3 in winter and summer, respectively. The unit cost of MD permeate was estimated to be 3.6 €/m3 and 4.1 €/m3 at a digestate feed temperature of 66 °C and 61 °C (with heat recovery), and 7.6 €/m3 and 9.1 €/m3 (without heat recovery) in winter and summer, respectively. However, cost sensitivity analyses showed that waste heat recovery and thermal energy cost variations had a significant impact on the MD permeate production cost. Nevertheless, the economic assessment indicated that the thermal integration of a biogas plant with industrial-scale MD digestate treatment capacity could be economically feasible, with winter being more economically favorable due to higher waste heat recovery.

Adsorbent Coatings for Adsorption Heat Transformation: From Synthesis to Application

In recent years, growing energy demands and environmental pollution caused by the extensive use of fossil fuels have inspired considerable research interest in adsorptive heat transformation (AHT). This technology offers effective utilization of low-grade solar or waste thermal energy for cooling and heating with low environmental impact. Increasing the AHT power is a keystone for further development and dissemination of this emerging technology. The AHT power is mainly determined by ad/desorption dynamics, which is significantly hindered by slow heat transfer between the adsorbent and heat exchanger. Shaping the adsorbent bed as a coating on the heat exchanger surface is considered an effective route to enhance heat transfer and increase the AHT power. In this review, the technology of adsorbent coating for AHT is comprehensively surveyed, including coating synthesis, adsorption dynamics, and use in real AHT devices. The advantages of the coated bed configuration are considered, and its challenges are outlined. Finally, recommendations for better organization of the coating’s structure for rational control of the relative contributions of heat and mass transfer are considered.

Multi-Objective Optimal Operation of Building Energy Management Systems with Thermal and Battery Energy Storage in the Presence of Load Uncertainty

This paper presents the optimal operation of a building energy management system (BEMS), with combined heat and power (CHP) generation, thermal energy storage (TES), and battery energy storage (BES), subject to load demand uncertainty. The main objective is to reduce the total operating cost (TOC) and total CO2 emission (TCOE). First, we develop two models of load demand forecasting, one for weekday and the other for weekend, using artificial neural networks, long short-term memory, and convolutional neural networks. Then, we incorporate the predicted load demand and load demand uncertainty for planning the energy dispatch of the BEMS. TES aims to store the thermal energy waste from the power generation of CHP and discharge the thermal energy to the absorption chiller to supply the cooling load. BES and spinning reserve (SR) play an important role in handling the uncertainty of the load demand. The operation of BEMS, subject to the load demand uncertainty, is formulated as a linear program. We can efficiently solve the linear program and provide an optimal solution that satisfies the dispatch constraints. Thereafter, we determine the optimal size of BES, based on economics and environmental optimal operation. The proposed BEMS is compared to the previous BEMS, without BES and SR. Furthermore, we propose the multi-objective optimal operation, where the normalization for TOC and TCOE is introduced, and the multi-objective function is defined as a linear combination of normalized TOC and TCOE. The numerical results reveal the trade-off relationship between TOC and TCOE. In particular, when TCOE is minimum, TOC becomes maximum. On the other hand, when TOC is minimum, TCOE becomes maximum. The relationship provides a method to select the operating point, as well as analyze the power flow for the multi-objective optimal operation.

Finite Element and Temperature Distribution Analysis over the Heat Pipe Boundary

Abstract: Researcher undergoes with various research activities to minimize the energy wastage and a researchers drawn their attention towards the recovery or storage of wasted energy but still there is a need of proper application and execution of the done research. The heat depletion through heat pipe heat exchanger is an excellent device to recover waste energy. The heat pipe heat exchanger not only is the effective way of storing the waste thermal energy but also it also prevents global warming. Heat pipes are inert, extremely consistent and provides with high heat transfer rates with minimal heat loss. These heat pipes are finding their way into sensitive applications such as notebook computers. A heat pipe is designed for cooling application in a computer has been evaluated through thermal analysis. The developed model of heat pipes used to draw a comparison with various parameters

Preparation and performance characterization of steel slag-based thermal storage composites for waste recycling and thermal energy storage

ABSTRACT At present, the steel industry produces a large amount of steel slag during the smelting process, which causes serious pollution to the environment and land. Therefore, new technologies must be used to deal with steel slag. In this study, the steel slag powder refined by the wet grinding technology is used as the matrix material, MgO as material additive, and the clay is used as the binder to prepare a new type of composite heat storage material. The results indicate that the mass ratio of wet grinding steel slag powder, MgO powder and clay is 6:3:1, the composite heat storage material can have a strong compressive strength of 70.9 MPa. The thermal conductivity of the heat storage material is 0.98 W/m⋅K and can reach 1.27 J/g⋅K at 720 ℃, which has good thermal conductivity and long service life. When the heat storage material rises to 900 ℃, the heat storage density can reach 905 J/g, with good heat storage performance and thermal cycle stability. The objective is to develop sustainable and low-cost thermal energy storage material for industry waste heat recovery and in renewable energy applications. At the same time, this valuable market for slag in the energy field provide a new way to directly utilize steel slag with extraordinary economic and environmental benefits.

Optimal design of dual-stage combined cycles to recover LNG cold energy and low-temperature waste thermal energy for sustainable power generation

To overcome the shortcomings of the low net power output of a single power generation cycle for LNG cold energy recovery, investigating dual-stage combined cycles with different cycle configurations under the same heat and cold source conditions is mandatory. Hence, this study proposes 12 dual-stage combined power generation cycles to utilize LNG cold energy and low-temperature (below 200 °C ) waste thermal energy. The developed method adopts an organic Rankine cycle and Brayton cycle as the bottoming cycle and the organic Rankine cycle, Brayton cycle, and supercritical carbon dioxide power cycle as the topping cycle with parallel and serial configurations. The optimization results show that the thermodynamic and economic performance are compared quantitatively. The optimally combined cycle is a dual-stage serial organic Rankine cycle with the highest specific net power output of 202.15 kJ/kg and lowest levelized cost of electricity of 0.11 $/kWh. Regarding the parallel configuration, it can enhance thermal and exergy efficiency via its internal heat integration. Moreover, the evaporation and condensation pressure of the bottoming cycle has a more significant influence on the optimally combined cycle than the topping cycle. Overall, this study paves the way to design economics-efficient dual-stage combined cycles for sustainable power generation by utilizing LNG cold energy and low-temperature waste thermal energy.

Porous Fly Ash/Aluminosilicate Microspheres-Based Composites Containing Lightweight Granules Using Liquid Glass as Binder

The modern energy-saving vector of development in building materials science is being implemented in a complex way through the development of new heat-insulating materials with the simultaneous exclusion of low-ecological cement from them. This article presents the results of the development of resource-saving technology for a heat-insulating composite material. The research is devoted to the development of scientific ideas about the technology and properties of effective cementless lightweight concretes. The aim of the work is to create a heat-insulating composite material based on porous granules and a matrix from mixtures of liquid glass and thermal energy waste. The novelty of the work lies in establishing the patterns of formation of a stable structure of a porous material during thermal curing of liquid glass with technogenic fillers. Studies of liquid glass mixtures with different contents of fly ash and aluminosilicate microspheres revealed the possibility of controlling the properties of molding masses in a wide range. To obtain a granular material, liquid glass mixtures of plastic consistency with a predominance of aluminosilicate microspheres are proposed. The matrix of composite materials is formed by a mobile mixture of liquid glass and a combined filler, in which fly ash predominates. The parameters of heat treatment of granular and composite materials are established to ensure the formation of a strong porous waterproof structure. The possibility of regulating the structure of composite materials due to different degrees of filling the liquid glass matrix with porous granules is shown. A heat-insulating concrete based on porous aggregate has been developed, characterized by the genetic commonality of the matrix and the granular component, density of 380–650 kg/m3, thermal conductivity of 0.095–0.100 W/(m °C) and strength of 3.5–9.0 MPa, resistance under conditions of variable values of humidity and temperature. A basic technological scheme for the joint production of granular and composite materials from liquid glass mixtures is proposed.

Use of Zeolites in the Capture and Storage of Thermal Energy by Water Desorption-Adsorption Cycles.

In this work, four zeolite-bearing materials (three naturally occurring and one of synthetic origin) were considered for thermal energy capture and storage. Such materials can store thermal energy as heat of desorption of the water present therein, heat that is given back when water vapor is allowed to be re-adsorbed by zeolites. This study was carried out by determining the loss of water after different activation thermal treatments, the water adsorption kinetics and isotherm after an activation step of the zeolites, the intergranular and intragranular porosity, and the thermal conductivity of the zeolite-bearing materials. Moreover, the thermal stability of the framework of the zeolites of the four materials tested was investigated over a large number of thermal cycles. The results indicate that zeolite 13X was the most suitable material for thermal energy storage and suggest its use in the capture and storage of thermal energy that derives from thermal energy waste.

Thermoelectric-Powered Supercapacitors Based on Ni–Mn Nanowires Driven by Quadripartite Electrolyte

Thermal energy is copiously available, especially low-grade heat which is typically wasted as a byproduct without use. Tapping into this immense energy reservoir with cost-effective technologies may become a key element for an energy-sustainable economy and society. The utilization of this waste thermal energy holds great potential in space applications for generating electric energy without using a solar panel. With this approach of harvesting heat energy, Ni–Mn composite nanowire-based electrodes synthesized via the electrochemical deposition technique are used to assemble a thermoelectric-powered supercapacitor. For charging purpose, the thermoelectric phenomenon of a quadripartite gel electrolyte [K3Fe(CN)6 + K4Fe(CN)6 + KOH + PVA] is tested. High-grade flexible copper tape used as a substrate can withstand high temperature and is perfectly suitable for thermoelectric devices. The fabricated symmetric device attained a high specific capacitance of 556 F/g at 4 mA in addition to a high energy density of 173.75 W h/kg at 3 kW/kg. Moreover, the fabricated thermoelectric-powered device attains a maximum voltage of ∼60 mV as a result of a temperature difference in the range of 8–10 °C. The proposed supercapacitor offers opportunities for the development of future devices that simultaneously harvest and store energy.

A novel hydrogen production system to storage the waste thermal energy of power plants

A novel hydrogen production system to storage the waste thermal energy of power plants

Miniaturized in-plane π-type thermoelectric device composed of a II–IV semiconductor thin film prepared by microfabrication

A miniaturized in-plane π-type thermoelectric device based on an epitaxial thin film of the II–IV compound thermoelectric semiconductor Mg2Sn0.8Ge0.2 was developed utilizing the microfabrication techniques of photolithography and dry etching. Highly reliable thermoelectric device operation was successfully achieved. The microfabricated thermoelectric device generated a relatively high output voltage of 0.58 V and an output power of 0.6 μW, corresponding to a comparatively high output power density of 21 mW·cm−2. The successful demonstration of a microfabricated thin-film-based thermoelectric device paves the way toward novel thermoelectric applications for self-powered Internet of Things devices and systems, as well as applications involving the effective use of the waste thermal energy generated from high heat density during the operation of electronic devices and systems.