Low-temperature Industrial Waste Heat Research Articles

Research on the Performance of Thermoelectric Self-Powered Systems for Wireless Sensor Based on Industrial Waste Heat.

The issue of energy supply for wireless sensors is becoming increasingly severe with the advancement of the Fourth Industrial Revolution. Thus, this paper proposed a thermoelectric self-powered wireless sensor that can harvest industrial waste heat for self-powered operations. The results show that this self-powered wireless sensor can operate stably under the data transmission cycle of 39.38 s when the heat source temperature is 70 °C. Only 19.57% of electricity generated by a thermoelectric power generation system (TPGS) is available for use. Before this, the power consumption of this wireless sensor had been accurately measured, which is 326 mW in 0.08 s active mode and 5.45 μW in dormant mode. Then, the verified simulation model was established and used to investigate the generation performance of the TPGS under the Dirichlet, Neumann, and Robin boundary conditions. The minimum demand for a heat source is cleared for various data transmission cycles of wireless sensors. Low-temperature industrial waste heat is enough to drive the wireless sensor with a data transmission cycle of 30 s. Subsequently, the economic benefit of the thermoelectric self-powered system was also analyzed. The cost of one thermoelectric self-powered system is EUR 9.1, only 42% of the high-performance battery cost. Finally, the SEPIC converter model was established to conduct MPPT optimization for the TEG module and the output power can increase by up to approximately 47%. This thermoelectric self-powered wireless sensor can accelerate the process of achieving energy independence for wireless sensors and promote the Fourth Industrial Revolution.

Advanced Exergy and Exergoeconomic Analysis of Cascade High-Temperature Heat Pump System for Recovery of Low-Temperature Waste Heat

Cascade high-temperature heat pumps (CHTHPs) are often applied to recover low-temperature industrial waste heat owing to their large temperature lift. Through a comprehensive consideration of thermodynamic and economic performance, conventional and advanced exergy and exergoeconomic analyses are employed in this study to evaluate the potential for the improvement in CHTHP systems. The results show that the avoidable endogenous exergy destruction in a CHTHP system accounts for 62.26% of its total exergy destruction, indicating that most of the exergy destruction comes from the components. This suggests that CHTHP systems still have significant potential for improvement. The very low exergoeconomic factor of the total system (only 0.75%) implies that the exergy destruction cost has a great influence on the economic performance of a CHTHP system. The high- and low-temperature compressors are the two components with the highest exergy destruction, accounting for 34.14% and 26.79% of the total exergy destruction in the system, respectively. Moreover, their exergy destruction cost is much larger than that of the other components. Thus, the priorities for improvement should be the high- and low-temperature compressors. The decrease in exergy destruction in compressors produces a reduction in carbon emissions. This comprehensive analysis of thermodynamic and economic performance supplies guidance for the engineering application of CHTHPs in low-temperature waste heat recovery.

Chemistry of the iron-chlorine thermochemical cycle for hydrogen production utilizing industrial waste heat

This research presents an inventive thermochemical cycle that utilizes a reaction between iron and HCl acid for hydrogen production. The reaction occurs spontaneously at room temperature, yielding hydrogen and a FeCl2 solution as a by-product. Exploring the thermal decomposition of the FeCl2 by-product revealed that, at conditions suitable for utilization of low-temperature industrial waste heat (250 °C), chlorine gas formation can be circumvented. Instead, the resulting by-product is HCl, which is readily soluble in water, facilitating direct reuse in subsequent cycles. The utilization of low-temperature industrial heat not only optimizes resource utilization and reduces operational costs but also aligns with environmentally sustainable production processes. From the kinetic studies the activation energy was calculated to be 45 kJ/mol and kinetics curves were constructed. They showed significant kinetics at room temperature and above but rapid decrease towards lower temperatures. This is important to consider during real-scale technology optimization. The theoretical overall energy efficiency of the cycle, with 100% and 70% heat recuperation, was calculated at 68.8% and 44.8%, respectively. In practical implementation, considering the efficiency of DRI iron reduction technology and free waste heat utilization, the cycle achieved a 41.7% efficiency. Beyond its energy storage capabilities, the Iron-chlorine cycle addresses safety concerns associated with large-scale hydrogen storage, eliminating self-discharge, reducing land usage, and employing cost-effective storage materials. This technology not only facilitates seasonal energy storage but also establishes solid-state energy reserves, making it suitable for balancing grid demands during winter months using excess renewable energy accumulated in the summer.

Review on Salt Hydrate Thermochemical Heat Transformer

The industrial sector utilizes approximately 40% of global energy consumption. A sizeable amount of waste energy is rejected at low temperatures due to difficulty recovering with existing technologies. Thermochemical heat transformers (THT) can play a role in recovering low-temperature industrial waste heat by storing it during high supply and discharging it on demand at a higher temperature. Thus, THT will enable waste heat reintegration into industrial processes, improving overall energy efficiency and lowering greenhouse gas emissions from the industrial sector. Salt hydrate is a promising thermochemical material (TCM) because it requires a low charging temperature which can be supplied by waste heat. Furthermore, its non-toxic nature allows the implementation of a simpler and less costly open system. Despite extensive research into salt hydrate materials for thermochemical energy storage (TCES) applications, a research gap is identified in their use in THT applications. This paper aims to provide a comprehensive literature review of the advancement of THT applications, particularly for systems employing salt hydrates material. A discussion on existing salt hydrate materials used in the THT prototype will be covered in this paper, including the challenges, opportunities, and suggested future research works related to salt hydrate THT application.

High-temperature heat pumps in climate pathways for selected industry sectors in Switzerland

To reach the goals of long-term energy and climate policy, the contribution of the industrial sector is important. Upgrading low temperature industrial waste heat using electric high-temperature heat pumps (HTHPs) can improve the overall energy-efficiency and mitigate CO2 emissions by replacing fossil fuels. The pulp and paper and the food and beverage industries use significant quantities of heat up to 200 °C and therefore have a high potential for the application of HTHPs. In order to assess the role of HTHPs, a techno-economic bottom-up cost optimization model is developed building on the Swiss TIMES Energy system Model (STEM). We present an advanced modeling framework including energy and material flows, with a high temporal resolution and a segregation of the temperature level of the process heat. The results show that HTHPs are cost-effective up to a temperature of 150 °C. Switzerland has the economic potential to deploy of about 100 MWth in the pulp and paper industry and 900 MWth in the food and beverage industry by 2050. Incentivizing the exploitation of this significant potential will require very high CO2 prices of several hundred €/tCO2 or additional policies to overcome investment barriers by supporting investment and flexible system-serving operation of heat pumps.

Low-Temperature Industrial Waste Heat (IWH) Recovery Using a New Design for Fast-Charging Thermal Energy Storage Units

The dynamic melting of CuO–coconut oil was addressed in a latent-heat thermal energy storage unit loaded with copper foam. In a new design, the thermal storage unit is made of a shell-tube-shaped chamber, in which a liquid flow of hot phase-change material (PCM) is allowed to enter the chamber from a port at the bottom and exit at the top. A fin is mounted in the chamber to forward the entrance PCM liquid toward the solid regions. The control equations were solved using the finite element method. The impact of foam porosity, inlet pressure, fin length, and the concentrations of CuO nanoparticles on the thermal charging time of the chamber was investigated. A fast-charging time of 15 min with a foam porosity of 0.95 was achieved. A porosity of 0.95 can provide a maximum thermal charging power of 15.1 kW/kg. The inlet pressure was a significant parameter, and increasing the inlet pressure from 0.5 kPa to 4 kPa reduced the melting time by 2.6 times. The presence of the fin is not advantageous, and even a long fin could extend the thermal charging time. Moreover, dispersed nanoparticles were not beneficial to dynamic melting and extended the thermal charging time.

Decarbonisation of heat: Analysis of the potential of low temperature waste heat in UK industries

The UK will need to decarbonise low temperature industrial waste heat (up to ≈250 °C) to achieve net-zero greenhouse gas emission targets. Industrial waste heat production represents an opportunity for reduction in the use of primary fuels used in the production of commodities. Energy inefficient processes in addition to increased emissions raises the cost of plant operation, – an undesirable scenario for both industrial competitiveness and the environment. Less is known about the quantity and potential applications for recovered low temperature industrial waste heat in UK and the quantification and characterisation of the resource can provide the needed impetus for the development and adoption of green technologies to help achieve the 2050 Net-Zero target. In this work the potential magnitude of the low temperature industrial waste heat resource in the UK is analysed by using sector-level energy intensity values for different industries while drawing on corresponding estimates from previous studies in the USA and by closely mapping the UK Standard Industrial Classification (SIC 2007) against sectors in the USA (NAICS [North American Industry Classification System]). The assessment undertaken finds that the recoverable potential of low temperature waste heat up to ≈250 °C could be up to 83.7% of the total estimated waste heat potential in UK industry. Significant opportunities exist in this low temperature range for waste heat recovery actions at individual sites. Research and Development (R&D) into alternative improved methods for waste heat recovery, storage, and use (WHRSU) technologies could also produce significant positive environmental and industrial impact.

Is Kalina cycle or organic Rankine cycle for industrial waste heat recovery applications? A detailed performance, economic and environment based comprehensive analysis

Contrary to the increase in energy demand throughout the world, fossil fuels, which are the main energy source, is now more difficult to reach because of the pandemic, transport or bilateral relations, etc. These obstacles in obtaining fossil fuels reveal the need to minimize energy wastage by utilizing low-temperature waste heat sources releasing the atmosphere without use. Especially for the industrial fields usage of advanced heat recovery systems is necessary. In addition, it is a remarkable point that the evaluation of low-temperature thermal energy potential will contribute significantly to the reduction of carbon emissions, which is one of the most important goals in developed and developing countries. In this study, Kalina and Organic Rankine cycles, which are the most important low-temperature energy conversion systems in the utilization of low-temperature industrial waste heat with a temperature of 250 ºC and a mass flow of 10 m/s, were examined and compared to each other in terms of energy, exergy efficiency, economic outlook, and environmental effects. During the study, the turbine inlet pressure of the Kalina cycle was selected as 60, 90 and 120 bar, while the turbine inlet pressure of the organic Rankine cycle increased from 10 bar to the critical pressure of the fluid. For all selected pressure levels, the turbine inlet temperature was increased from the saturated vapor temperature of the fluid to 240 ºC. As a result, although the Kalina cycle was found economically better than the organic Rankine cycle (3.93 years), the organic Rankine cycle using n-Pentane showed a better performance than the Kalina cycle in terms of energy, exergy, and CO2 emission reduction. The thermal efficiency, exergy efficiency, payback period, and CO2 emission reduction value of the organic Rankine cycle with n-Pentane were calculated as 25.95%, 71.77%, 4.03 years, and 207.17 kg-CO2/h, respectively.

The Thermal Economy of a Circulating Medium and Low Temperature Waste Heat Recovery System of Industrial Flue Gas

The waste heat recovered by traditional industrial waste heat recovery systems is mostly high-temperature flue gas and combustible gas, while the waste heat of medium and low temperature flue gas that accounts for more than 50% of the total waste heat resources has been ignored, which is not conducive to the effective energy saving of industrial production and manufacturing process. In the meantime, few studies have concerned about the changes in the economy of circulating industrial waste heat recovery system. Therefore, to fill in this research gap, this paper aimed at the economy problem of circulating medium and low temperature industrial waste heat recovery system and carried out a series of research. The paper completed the thermodynamic analysis of different medium and low temperature waste heat recovery modes of industrial flue gas, and gave the analysis steps of the economy of circulating medium and low temperature waste heat recovery system of industrial flue gas. The effectiveness and accuracy of the thermodynamic and thermo-economic models constructed in the paper were proved by experimental results.

Large-Scale Geothermal Collector Systems for 5th Generation District Heating and Cooling Networks

Low temperature district heating and cooling networks (5GDHC) in combination with very shallow geothermal energy potentials enable the complete renewable heating and cooling supply of settlements up to entire city districts. With the help of 5GDHC, heating and cooling can be distributed at a low temperature level with almost no distribution losses and made useable to consumers via decentralized heat pumps (HP). Numerous renewable heat sources, from wastewater heat exchangers and low-temperature industrial waste heat to borehole heat exchangers and large-scale geothermal collector systems (LSC), can be used for these networks. The use of large-scale geothermal collector systems also offers the opportunity to shift heating and cooling loads seasonally, contributing to flexibility in the heating network. In addition, the soil can be cooled below freezing point due to the strong regeneration caused by the solar irradiation. Multilayer geothermal collector systems can be used to deliberately generate excessive cooling of individual areas in order to provide cooling energy for residential buildings, office complexes or industrial applications. Planning these systems requires expertise and understanding regarding the interaction of these technologies in the overall system. This paper provides a summary of experience in planning 5GDHC with large-scale geothermal collector systems as well as other renewable heat sources.

Performance evaluation of an absorption heat transformer for industrial heat waste recovery using the characteristic equation

In this paper we report on new experimental results of an absorption heat transformer. In order to have a concise view on the whole performance field the characteristic equation model, a novel version of ideas from the 80ies of the last century is developed. In the model insight from recent research on absorption chillers is used. The 40 kW prototype implements a single effect absorption cycle working with water as refrigerant and an aqueous LiBr solution as the solvent. As a novelty, the parameter set of the characteristic equation model has been obtained from the cycle analysis of the device based on the measurements of one single operating point. The resulting model predicts the prototype performance for driving heat temperature levels of low temperature industrial waste heat sources (60–100 °C), with variations of the temperature of the useful upgraded between 90 and 138 °C that result in gross temperature lifts (GTL) between 20 and 55 K. The measured COP values are between 0.30 and 0.48. An additional regression developed after evaluating the deviations from the model assumptions reduces the uncertainty of the model. The uncertainties for COP and upgraded heat flow rate predictions are below 11% (R2 = 0.812) and 4% (R2 = 0.918) respectively.

Towards efficient oxygen separation from air: Influence of the mean rare-earth radius on thermodynamics and kinetics of reactivity with oxygen in hexagonal Y1-xRxMnO3+δ

It is documented that the mean radius r¯ of rare-earth cations occupying Y1-xRx sublattice in Y1-xRxMnO3+δ hexagonal oxides plays a decisive role in terms of thermodynamics and kinetics of reactivity of the materials with oxygen, and consequently, influences strongly the oxygen storage performance in thermal swing processes conducted in oxygen and air. Y1-xRxMnO3+δ samples with designed r¯ being close to the critical one, at the border of stability between hexagonal- and perovskite-type phases, can reversibly incorporate/release significant amounts of oxygen in pure O2 or air atmospheres, at the moderate temperatures on the order of 200–300 °C. Characteristic temperatures of oxidation and reduction are dependent on r¯, therefore, it is possible to adjust conditions of the temperature swing operation by the chemical doping in Y1-xRxMnO3+δ with larger rare-earth elements. Crucial from a practical point of view, an increase of the oxidation temperature in such compounds greatly enhances the speed of the oxidation process (20 °C increase can reduce half-time of oxidation twice), which is found to be the limiting factor concerning the performance. Based on the comprehensive studies of the physicochemical properties of Y1-xRxMnO3+δ, the optimized Y0.95Pr0.05MnO3+δ composition is proposed, doped only with a small amount of more expensive praseodymium. The material exhibits excellent oxygen storage-related properties and is able for the effective production of oxygen in air by the thermal swing process, utilizing medium-/low-temperature industrial waste heat.

A review of heat integration approaches for organic rankine cycle with waste heat in production processes

Production systems represent a significant source of waste heat. The waste heat cannot be reused often. Many optimization methods can give a solution for waste heat recovery. However, the results do not depend only on the method. The low-temperature waste heat makes difficulties for its recovery within the processes. Organic Rankine Cycle units can be used for low-temperature heat transformation into electricity. Linking the Organic Rankine Cycle within the heat integrated system is not simple. This depends on the influence of a few important factors. The process parameters of the working medium, the physical and chemical characteristics of the working fluid, the continuity of heat supply, and the temperature level of waste heat are necessary conditions that must be included in optimization. The optimization method should determine the optimal operating point of the Organic Rankine Cycle. The displacement of the operating point leads to decrease in the effective transformation of heat into electricity. These problems are analyzed through a review of the methods and approaches used for the integration of Organic Rankine Cycle in thermal process systems. These include Pinch technology, Non-Linear Programming, Multiple Integer Linear Programming, Genetic Algorithm, Artificial Neural Network and many different approaches for polygeneration systems. All methods were compared and systematized in a general scheme for integration of an Organic Rankine Cycle with low-temperature industrial waste heat supply. This work also includes experience in implemented and designed projects of an integrated Organic Rankine Cycle.

Experimentally economic analysis of ORC power plant with low-temperature waste heat recovery

Abstract Due to the low boiling point of organic fluids, the organic Rankine cycle (ORC) is an effective way to improve the recovery efficiency of low-temperature waste heat. An ORC power plant was established with an actual generating capacity of 16.3 kW. As the ORC technology is in the initial stage of commercial application, a technical and economic analysis has been conducted in this paper. Through analysis of each part investment of the power generation plant, it is found that the ORC system part accounts for 61% of the total initial investment, and the larger the power generation scale, the larger the proportion. An economic model has been proposed to study the economic feasibility of low-temperature industrial waste heat conversion in this plant. The influences of the installation of cooling water system, preheater, superheater, loan ratio, interest rate on electricity production cost (EPC) and profit are analyzed. According to the analysis, the lowest EPC of the plant is 0.46 Yuan/(kW • h).

Energy- and exergy-based optimal designs of a low-temperature industrial waste heat recovery system in district heating

This paper illustrates how the choice of indicators changes the design of a waste heat recovery system in district heating. A prospective system in Grenoble (France) aims to valorize waste heat from the French National Laboratory of Intense Magnetic Fields (LNCMI) by injecting it at 85 °C to the nearby district heating network. We optimize its design for three possible waste heat temperatures: 35 °C (current), 50 °C (viable) and 85 °C (innovative). As major components, the system includes a thermal storage (ranging from 10 MWh to 40 MWh) and may include a heat pump depending on the waste heat’s temperature. Different optimizations are guided by two energetic indicators (one source-oriented, the other demand-oriented) and by the overall exergy efficiency. The system’s annual performance is assessed through the Sankey and Grassman diagrams and compared between optimal designs. Yearly simulation included optimal management of the thermal storage, through mixed-integer linear programming. The demand-oriented optimal design suggests recovering waste heat at 35 °C with a heat pump and a 40-MWh storage, granting the highest coverage of residential needs (49%). On the other hand, the source-oriented optimal design suggests recovering waste heat at 85 °C without heat pump and with a 40-MWh storage, reaching the highest recovery of waste heat (55%). Exergy analysis supports the source-oriented design, as it reaches the highest global exergy efficiency (27%). Our prospective techno-economic and exergo-economic analyses should complement these results and may change some conclusions, especially regarding the storage capacity.

Improved performance of binder-free zeolite Y for low-temperature sorption heat storage

Improved performance of modified binder-free zeolite Y in mobile sorption heat storage for low-temperature industrial waste heat recovery.

New low temperature industrial waste heat district heating system based on natural gas fired boilers with absorption heat exchangers

To efficiently recover low temperature industrial waste heat, a new low temperature industrial waste heat district heating system based on natural gas fired boilers with absorption heat exchangers was proposed, and also analyzed from the perspective of thermodynamics and economics. In heating substations, absorption heat exchangers are used to greatly decrease the return water temperature of the primary heating network. The lower temperature return water helps to efficiently recover waste heat in heating station and greatly increase economic heat transmission distance. Annual primary energy efficiency and product exergy efficiency of the new district heating system are 215.0% and 42.5% respectively. When waste heat price and heat transmission heat distance are 25¥/GJ and 60km respectively, its heating cost and investment recovery period are 6¥/GJ and 0.7years respectively lower than that of current district heating systems based on natural gas fired boilers. Characterized by better thermodynamic performance and economic benefit, the new district heating system would be promising for low-temperature industrial waste heat recovery.

Experimental study on organic Rankine cycle utilizing R245fa, R123 and their mixtures to investigate the maximum power generation from low-grade heat

The main purpose of this paper is experimentally comparing of organic Rankine cycle (ORC) system, by using R245fa, R123 and their mixtures to generate maximum net power on simulated low-temperature industrial waste heat. Four mass fractions of R245fa:R123 have been injected into the system with the ratios of 1:0, 2:1, 1:2 and 0:1 to test the system performance separately. To imitate industrial low-temperature waste heat, the heat source temperature is fixed at 110 °C and 120 °C with specified mass flow rate of heat source. Focusing on the change of mass flow rate of working fluid and expander inlet superheating, experiment results show that the system heat input increases when mass flow rate of working fluid increases. All four mass fractions of working fluids generate maximum net power when the system mass flow rate is around 0.15 kg/s. The case of pure R245fa generates a maximum net power 1.56 kW with an electrical efficiency of about 3.9% when heat source temperature is fixed at 110 °C. While, the case of mixture R245fa:R123 = 2:1 generates a maximum net power 1.66 kW with an electrical efficiency of about 4.4% when heat source temperature input is fixed at 120 °C.

Pushing desalination recovery to the maximum limit: Membrane and thermal processes integration

The economics of seawater desalination processes has been continuously improving as a result of desalination market expansion. Presently, reverse osmosis (RO) processes are leading in global desalination with 53% share followed by thermally driven technologies 33%, but in Gulf Cooperation Council (GCC) countries their shares are 42% and 56% respectively due to severe feed water quality. In RO processes, intake, pretreatment and brine disposal cost 25% of total desalination cost at 30–35% recovery. We proposed a tri-hybrid system to enhance overall recovery up to 81%. The conditioned brine leaving from RO processes supplied to proposed multi-evaporator adsorption cycle driven by low temperature industrial waste heat sources or solar energy. RO membrane simulation has been performed using WinFlow and IMSDesign commercial softwares developed by GE and Nitto. Detailed mathematical model of overall system is developed and simulation has been conducted in FORTRAN. The final brine reject concentration from tri-hybrid cycle can vary from 166,000ppm to 222,000ppm if RO retentate concentration varies from 45,000ppm to 60,000ppm. We also conducted economic analysis and showed that the proposed tri-hybrid cycle can achieve highest recovery, 81%, and lowest energy consumption, 1.76kWhelec/m3, for desalination reported in the literature up till now.

Honeycomb filters made from mesoporous composite material for an open sorption thermal energy storage system to store low-temperature industrial waste heat

Today, a significant amount of low-temperature (< 100°C) industrial waste heat is directly discharged to the atmosphere. In this study, a new mesoporous composite material was developed as a sorption thermal energy storage material by utilizing its sorption and desorption properties. The composite material was formed by adding calcium chloride (CaCl2) to a mesoporous ceramic honeycomb filter. The main component of this ceramic is Wakkanai siliceous shale (WSS), which is found in northern Japan. The material test results demonstrated the following: (1) the composite material can sorb more water than the original ceramic material without dropping the CaCl2 solution; (2) it can be regenerated at around 100°C; and (3) after 25 repetitive regeneration/sorption cycles, no decomposition or cracks were observed. The sorption isotherm was also undamaged.An open sorption thermal energy storage system was proposed, and the experimental setup was constructed. A low regeneration temperature (80–100°C) of the storage medium was achieved with this open system. In the case of the 22.4 wt% CaCl2 supported with the honeycomb filter (926.2g; 2 L), air was heated to a temperature greater than 40°C for a duration of 432min by supplying air at 25°C at a flow rate of 3.0 m3/h when the regeneration temperature was 80°C. The volumetric heat storage density obtained was 272MJ/m3, and the coefficient of the heat extraction performance during the heat release process was 65%.