Industrial Process Heat Research Articles

Novel highly performing tandem selective solar absorber for industrial heat applications

The needed decarbonisation of the industrial sector for an efficient transition to a Net Zero future, alongside the lack of commercially competitive solar absorbers for industrial heat applications using small non-evacuated receiver tubes, has motivated the design of a new highly stable material suitable for the open-air conditions. This work demonstrates that the potential candidate is the CuCoMnOx/SiO2 tandem selective absorber, designed to coat line-focussed receiver tubes to supply thermal energy up to 450 °C for industrial process heat applications. Remarkably, with only two layers deposited on stainless-steel (SS) under optimised conditions, the material exhibits excellent optical performance, achieving a αs > 0.95 and a ε350°C = 0.16. The absorber design prioritises cost-effective industrialisation by optimising thermal treatment to lower both temperature and duration time, while fine-tuning layer thicknesses to locate optical interferences at the required wavelengths. This approach ensures outstanding reproducibility, uniformity, and efficiency, marking the first successful deposition of coatings on tubular forms. The coatings composing the absorber are characterised optically, by X-ray diffraction, scanning electron microscope, and thermogravimetric and differential scanning calorimeter techniques. In terms of durability, the absorber shows extraordinary resilience, maintaining thermal stability for 27 months at 400–450 °C in open air, and exhibiting good resistance to condensation (PC = 0.03 in the most drastic situation). Therefore, the SS-substrate/CuCoMnOx/SiO2 absorber emerges as a promising commercial material for both evacuated and non-evacuated receiver tubes, promoting the integration of concentrating solar power (CSP) technology with solar heat for industrial processes (SHIP).

High temperature heat pumps for industrial heating processes using water as refrigerant

High temperature heat pumps for industrial heating processes using water as refrigerant

Electrification or Hydrogen? The Challenge of Decarbonizing Industrial (High-Temperature) Process Heat

The decarbonization of industrial process heat is one of the bigger challenges of the global energy transition. Process heating accounts for about 20% of final energy demand in Germany, and the situation is similar in other industrialized nations around the globe. Process heating is indispensable in the manufacturing processes of products and materials encountered every day, ranging from food, beverages, paper and textiles, to metals, ceramics, glass and cement. At the same time, process heating is also responsible for significant greenhouse gas emissions, as it is heavily dependent on fossil fuels such as natural gas and coal. Thus, process heating needs to be decarbonized. This review article explores the challenges of decarbonizing industrial process heat and then discusses two of the most promising options, the use of electric heating technologies and the substitution of fossil fuels with low-carbon hydrogen, in more detail. Both energy carriers have their specific benefits and drawbacks that have to be considered in the context of industrial decarbonization, but also in terms of necessary energy infrastructures. The focus is on high-temperature process heat (>400 °C) in energy-intensive basic materials industries, with examples from the metal and glass industries. Given the heterogeneity of industrial process heating, both electricity and hydrogen will likely be the most prominent energy carriers for decarbonized high-temperature process heat, each with their respective advantages and disadvantages.

Porous Monolithic Perovskite Structures for High-Temperature Thermochemical Heat Storage in Concentrated Solar Power (CSP) Plants and Renewable Electrification of Industrial Processes

A novel approach towards thermal energy storage of surplus renewable energy (RE) is introduced via a hybrid thermochemical/sensible heat storage concept implemented with the aid of porous structures made of redox metal oxides, capable of reversible reduction/oxidation upon heating/cooling in direct contact with air, accompanied, respectively, by endothermic/ exothermic heat effects and demonstrating fully reversible dimensional changes under cyclic operation. The proposed modular storage units can be heated during the day to a level exceeding the metal oxide’s reduction onset temperature either by hot air streams from air-operated Concentrated Solar Power (CSP) tower plants or via surplus/cheap RE-electricity from photovoltaics, wind, or other renewable sources (“charging”/energy storage step). When this RE sources become non-available or upon demand, the fully charged system can transfer its energy to a controlled airflow that passes through the porous oxide block and initiates the exothermic oxidation of the reduced metal oxide. Thus, a hot air stream is produced which can be used to provide electricity or exploitable heat for industrial processes. The present work elaborates on the operating principles and the potential application of this concept and reports progress in the preparation and shaping of reticulated porous ceramics (RPCs also known as “ceramic foams”) from CaMnO3-based perovskite compositions and their preliminary testing with respect to cyclic reduction-oxidation.

Heat transfer and fluid flow analysis of a solar air heater using conical jet impingement with sine-wave corrugation on absorber plate

In the pursuit of renewable energy solutions, solar air heaters emerge as a promising technology to efficiently harness solar thermal energy for diverse applications such as space heating, agricultural drying and industrial process heating. However, the system’s efficiency is often limited by the low heat transfer capability of air and the formation of laminar sub-layer over the absorber plate. This study addresses the issue by investigating the innovative use of conical jet impingement combined with sine wave corrugations on the absorber plate to enhance heat transfer in solar air heaters. The design parameters include wave amplitude ratio (0.079–0.314), throat jet diameter ratio (0.063–0.141), base jet diameter ratio (0.126–0.251), and Reynolds number (3200–19200) as the operational parameter. The computational fluid dynamics simulations are employed to solve the Reynolds-Averaged Navier-Stokes equations coupled with RNG k-ɛ turbulence model to assess the heat transfer and frictional characteristics, followed by experimental validation. The findings demonstrate a significant improvement in the system’s heat transfer rate with the Nusselt number increase by a factor of 6.71 times compared to a smooth solar air heater, while the friction factor increase by 13.87 times. Furthermore, the highest thermo-hydraulic performance parameter is found to be 2.79 corresponding to Reynolds number of 3200, wave amplitude ratio of 0.079, throat and base jet diameter ratios of 0.126 and 0.220, respectively. The proposed geometry will be helpful for academic researchers and can be adopted by the industries for various applications.

Enhancing Heat Storage Capacity: Nanoparticle and Shape Optimization for PCM Systems

ABSTRACTPhase change material (PCM)‐based heat storage systems utilize the absorption or release of latent heat during a phase change of the storage material to store thermal energy. Nevertheless, the effectiveness of these systems is restricted by the shape and structure of their confinement, as well as the heat conductivity of the storage material. This work investigates a novel method to enhance the effectiveness of PCM systems by concurrently utilizing two techniques: the inclusion of nanoparticles and the alteration of the system's geometry. Introducing nanoparticles enhances the thermal conductivity of the storage medium while altering the shape, which improves heat transfer efficiency by adjusting the surface area available for heat exchange. RT‐35 was tested for use in latent heat thermal energy storage systems for space heating and cooling. With a melting point of 35°C, RT‐35 was chosen to moderate building temperatures by storing and releasing thermal energy for space heating and cooling. The results indicate that using nanoparticles and adjusting shape can greatly enhance the effectiveness of PCM systems. By incorporating Al2O3 nanoparticles, the melting time of the PCM was reduced by 20% compared to the pure PCM, and it is more efficient than the best case of shape modification. These findings indicate that including nanoparticles and modifying the shape are effective methods to improve the performance of heat storage devices. This technology's potential surpasses this study's limits and can be utilized in diverse applications, including solar thermal energy storage, district heating and cooling, and industrial process heat.

Energy saving potential in steam systems: A techno-economic analysis of a recycling pulp and paper mill industry in Morocco

The industrial sector represents nearly 40 % of global energy consumption, with steam systems accounting for 30 % of energy use in manufacturing. As the need for cleaner processes intensifies within African and global energy transitions, adopting energy efficiency practices becomes imperative. Governments are focusing on reducing energy losses in fossil fuel-dominated manufacturing industries, which are major producers of greenhouse gas emissions. Despite their significant energy consumption, industrial heat processes are often overlooked in efforts to reduce costs and emissions. To address this, the study examines thermal energy processes and identifies energy-saving opportunities within steam systems through a techno-economic analysis of a recycling pulp and paper mill in Morocco. This is the first study focusing specifically on steam systems within a particular industry in the country. The research uses a system approach covering steam generation, distribution, end-use, and recovery. The current system is benchmarked through a rating questionnaire, and proposed energy-saving actions include leak repair, pipe insulation, blowdown management, and improved boiler combustion efficiency. An economic study evaluates the cost-effectiveness of these opportunities. Findings reveal a 6 % reduction in thermal energy consumption, annual savings of $417 899 and nearly 482 TJ, a 6 % decrease in GHG emissions (2158.5 tons of CO2 per year), and water savings of approximately 5300 m³ per year (13 %). The total investment of $8750 has negligible payback periods. Despite diverse industrial activities, this work is useful for other industries since the fundamental components of the steam system are widely shared. Moreover, it supports the African Union's Agenda 2063 and United Nations Sustainable Development Goals by providing practical insights and recommendations for enhancing industrial energy efficiency.

Numerical investigation of an axisymmetric, dissipative, and unstable micropolar fluid flow over a stretched Riga plate incorporating mixed convection and chemical reaction

AbstractThe demand to improve the thermal performance of industrial working fluids and materials for better quality in engineering and household devices has spurred numerous studies on non‐Newtonian viscous fluids under various conditions. Researchers have explored different structures and geometries to understand and enhance the thermal propagation of fluid particles. As such, this research aims to investigate the effects of two‐dimensional unsteady boundary layer flow phenomena of a dissipative micropolar fluid over a radially stretching Riga plate when first‐order slip, thermal and solutal boundary conditions, mixed convection, and thermal radiation are all considered. Ordinary differential equations are the governing equations resulting from converting partial differential equations. The boundary layer conditions are altered and numerically solved using the Runge–Kutta fourth‐order shooting approach. Graphs and tables are used to visually analyze the physical attributes of temperature, concentration, velocity distributions, skin friction, Nusselt number, and Sherwood in relation to various factors. The results reveal significant insights into the impact of mixed convection and chemical reactions on the flow characteristics and dimensions. These findings have important implications for various engineering applications, particularly in enhancing industrial systems' heat and mass transfer processes, providing practical knowledge for improving thermal performance in real‐world applications.

Energetic and economic analysis of a novel concentrating solar air heater using linear Fresnel collector for industrial process heat

Industrial processes share a relevant portion of global energy consumption. A large variety of high energy-demanding industrial processes need hot air in the medium temperature range, provided by natural gas combustion or by electricity. Hot air is used as a medium in a large variety of processes such as drying, curing, and thermal treatments of several products and materials. Heat can be provided by solar thermal technologies aimed at the sustainable industry. Non-concentrating flat plate type solar collectors can directly heat air up to 100 °C while higher temperatures can be achieved using linear concentrating technology. In this study an innovative system using linear Fresnel collectors directly provides hot air for the industry up to 350 °C, avoiding the need for liquid heat transfer fluids. Accordingly, the installation is simplified, and lower installation and maintenance requirements are expected compared to other solar technologies. The present studies provide an energetic and economic analysis of the concentrating solar air heater, considering a medium-scale benchmark as a reference case in representative European locations. The results indicate that the solar technology here presented can be economically competitive with conventional natural gas heating, having a huge potential for fossil fuel source replacement in hot air based industrial processes.

Economic and environmental considerations for the deployment of industrial very high temperature heat pumps in European markets

Very high temperature heat pumps (VHTHP) have begun to emerge on the market during the past decade, providing an alternative to fuel-fire boilers for generating industrial process heat up to 200 °C. Large temperature lifts are common for VHTHPs, resulting in a reduced coefficient of performance (COP) compared to traditional heat pumps. Thus, the economic feasibility of operating VHTHPs becomes more dependent on local price conditions, and the environmental impact is affected by increased electricity usage. Both the economics and the environmental impact of operating industrial VHTHPs in place of fossil fuel-fired boilers in Europe are studied in this article. Discounted payback periods are estimated for the varying price conditions in Europe, and life cycle assessment tools are used to quantify the environmental impact of operating VHTHPs. Finland, Sweden, and Denmark were found to be ideal countries for VHTHP deployment, as they showcase both favorable economic conditions as well as generally small environmental impacts in the endpoint categories Human health, Climate change, and Resource usage, if local grid electricity is used. The effect on the endpoint category Ecosystem impacts was generally larger for most countries, including the aforementioned three, mostly due to the use of biomass in the electricity grid.

Case Studies and Parametric Analysis of Heliostat Performance with a Tradeoff-informed Technoeconomic Analysis Metric

Abstract The Heliostat Consortium (HelioCon) was launched in 2021 to advance heliostat technology. This work presents a collection of baseline case studies for the technoeconomic analysis (TEA) of candidate heliostat improvements for concentrating solar power (CSP) and concentrated solar thermal (CST) systems that employ central receivers. The case studies we develop include a large-scale CSP plant, a smaller, modular CSP plant, and a small CST plant used for industrial process heat. In this work, we propose a novel metric for TEA of a plant component technology that recasts relative changes in levelized system costs into component-specific capital cost budgets. This measure, which we refer to as the equivalent breakeven installed cost, is the maximum budget for the technology component that leads to improved levelized costs. Finally, we perform a parametric analysis to show the impact of candidate technologies on levelized cost of heat and, by extension, equivalent breakeven installed cost.

A new denitrification strategy based on high-temperature catalytic coatings Y2O3-BaO-ZrO2 without using ammonia in a lab-scale natural gas combustion furnace

Catalytic decomposition of NO at high temperatures without the use of ammonia, offers an eco-friendly and sustainable solution for denitrification in industrial combustion or heating processes. To simulate a complex combustion flue gas, we designed a lab-scale natural gas industrial combustion furnace specifically for assessing the impacts of Y2O3-BaO-ZrO2 catalyst coated on SiC plates on NO emissions. Various factors including the plate number, excess air ratio, combustion power, and coating position were considered. Results demonstrated that arranging the Y2O3-BaO-ZrO2 coated plates shifted the high-temperature zone of the furnace downstream. When the excess air ratio was below 1.05, the catalytic coating significantly reduced NO emission concentration at the furnace outlet by over 40 %. However, this reduction coincided with a substantial presence of unburned CO in flue gases. Placing the coated SiC plates in the constant temperature zone of 1100–1200 °C within the middle of furnace offered significant advantages in NO removal, particularly as the combustion power increased. Based on a 60-h durability evaluation of Y2O3-BaO-ZrO2 coating, the observed good high-temperature thermal and chemical stabilities further enhanced the coating’s potential for industrial application. The possible mechanism of the reduction NO by CO over coating surfaces were analyzed by in situ optical measurements. After calculation, using 12 kg Y2O3-BaO-ZrO2 catalysts might decrease at least 642 kg of ammonia consumption under ideal conditions, and significantly reduce the investment cost on existing flue gas denitrification equipment. Therefore, the investigated technology is a green and sustainable denitrification strategy, which would potentially provide a novel approach towards attaining ultra-low NO emissions.

Experimental investigation of a small-scale reversible high-temperature heat pump − organic Rankine cycle system for industrial waste heat recovery

Innovative technologies are required to mitigate the challenges of climate change. A reversible high-temperature heat pump (HTHP) − organic Rankine cycle (ORC) system can be used for effective utilisation of industrial waste heat in the lower temperature band <100 °C. The system can provide useful process heat for industrial processes by operating in HTHP mode or generating power in ORC mode. This paper presents the experimental investigation of the reversible system in both HTHP and ORC modes. A single scroll unit was selected for the compressor (HTHP) and expander (ORC) roles, keeping the system compact. A HCFO refrigerant, R1233zd(E), with a low GWP value, was chosen as the working fluid for both operating modes. When operated in HTHP mode, a maximum compressor overall isentropic efficiency of 73.4 % and a COPmech of 4.8 (ΔTlift,rside = 41 K, Tsf,ev,in = 60 °C) was obtained. In ORC mode, the maximum net power output was 512.4 W (Tsf,ev,in = 90 °C, rp = 2.3), overall cycle efficiency was 3.01 %, and overall isentropic efficiency of the expander was 54.6 %. The technical limitations encountered, and solutions put in place during the experimental testing campaign are discussed in detail.

A Planar-Cavity Receiver Configuration for High-Temperature Solar Thermal Processes

Next-generation concentrating solar thermal power (CSP) technologies target a wide spectrum of applications including electricity generation, thermochemical processes, and industrial process heat for broad decarbonization potential. Many of these applications require higher temperatures than those of current commercial nitrate salt systems. Particulate materials are promising candidates for next-generation high-temperature heat transfer and low-cost storage media and can facilitate operation over a wide temperature range. However these materials necessitate novel receiver configurations to accept the high incident flux concentrations that enable high solar-to-thermal receiver efficiency. One option is a novel light-trapping planar cavity receiver configuration in which small cavity-like structures are formed from opaque planar surfaces such that a high incident flux concentration at the cavity aperture is reduced to a wall-absorbed solar flux concentration that is manageable within limited wall-to-particle heat transfer rates. The paper introduces the receiver configuration and provides calculated optical performance for a preliminary 50 MWt receiver design.

Greenhouse Gas Mitigation Potential Through Clean Energy for Cement Production in India

Abstract A preliminary approach has been made to assess the concentrated solar energy applications in cement production as well as greenhouse gas mitigation potential. The work starts with identification of processes that utilize thermal energy in cement production. Then, a cluster of cement plants located at different locations in the country has been made. Also, the availability of solar radiation and wind speed at each plant location have been identified. Subsequently, the solar industrial process heating systems have been developed for different locations in the country. Further, solar reactor output, number of heliostats, total land area and mirror surface have been estimated. All these estimations are done by considering three types of thermal losses in solar reactors, i.e., 15, 30 and 45%, respectively. Solar energy can provide a total of 738.11 PJ of thermal energy, which is needed to fulfill the process heating requirement of the calcination process for the manufacturing of cement in India. Solar industrial process heating systems for cement production in India can reduce yearly CO2 emissions by 2457–7648 thousand tons.

Design and assessment of a concentrating solar thermal system for industrial process heat with a copper slag packed-bed thermal energy storage

Decarbonising the industrial sector is a key part of climate change mitigation targets, and Solar Heat for Industrial Process (SHIP) is a promising technology to achieve this. However, one of the drawbacks of SHIP systems is that they rely on an intermittent energy source. Therefore, sensible energy storage has emerged as a potential solution. In addition, solid byproducts have been proposed as a low-cost but effective material for thermal energy storage (TES). This work presents a SHIP system model coupled with a copper slag-packed-bed TES (PBTES) model using air as heat transfer fluid. The TES has been implemented to preheat the makeup water of the tank where steam is generated. A system design was carried out using a parametric analysis to find a solar field size and a corresponding TES volume. The resulting system was simulated, and the operating variables were analysed in detail. The results show that it is possible to generate 20% more energy due to the storage system. Additionally, a techno-economic analysis indicates that the SHIP with PBTES system results in a payback period of 14 years and a savings of CO2 emissions of 30tCO2.

An in‐depth comparative analysis of entropy generation and heat transfer in micropolar‐Williamson, micropolar‐Maxwell, and micropolar‐Casson binary nanofluids within PTSCs

AbstractSolar energy holds promise as a sustainable and environmentally friendly source of power. In this study, we focus on improving the thermal efficiency of parabolic trough solar collectors (PTSCs) by investigating the performance of three different binary micropolar nanofluids – micropolar‐Casson, micropolar‐Maxwell, and micropolar‐Williamson – when used as heat transfer fluids within these collectors, with engine oil as the base fluid. The problem studied revolves around enhancing the heat transfer characteristics within PTSCs, crucial for maximizing energy conversion efficiency in solar power generation. By exploring the behavior of these nanofluids under various flow conditions, we aim to optimize the design and operation of PTSC systems for improved performance and sustainability. The importance of this research lies in its potential to significantly enhance the efficiency of solar energy harvesting, thereby contributing to the transition toward cleaner energy sources and reducing dependence on fossil fuels. Additionally, the findings have implications for diverse applications, including solar aviation, solar‐powered maritime vessels, solar thermal power plants, industrial process heating, and solar‐driven water pumping mechanisms, where improved heat transfer efficiency is paramount for enhancing overall system performance and reducing operational costs. Furthermore, the investigation delves into the influence of various factors governing the flow of these binary micropolar nanofluids within PTSC setups, including aspects such as velocity, thermal characteristics, entropy generation, skin friction, drag force, and local Nusselt number. The results notably reveal substantial enhancements in thermal efficiency, with maximal relative enhancements quantified as 22.1768%, 19.3662%, and 17.7349% for micropolar‐Casson, micropolar‐Maxwell, and micropolar‐Williamson nanofluids, respectively.

Fabrication, Modeling, and Testing of a Prototype Thermal Energy Storage Containment

Abstract Increasing penetration of variable renewable energy resources requires the deployment of energy storage at a range of durations. Long-duration energy storage (LDES) technologies will fulfill the need to firm variable renewable energy resource output year round; lithium-ion batteries are uneconomical at these durations. Thermal energy storage (TES) is one promising technology for LDES applications because of its siting flexibility and ease of scaling. Particle-based TES systems use low-cost solid particles that have higher temperature limits than the molten salts used in traditional concentrated solar power systems. A key component in particle-based TES systems is the containment silo for the high-temperature (&amp;gt;1100 ∘C) particles. This study combined experimental testing and computational modeling methods to design and characterize the performance of a particle containment silo for LDES applications. A laboratory-scale silo prototype was built and validated the congruent transient finite element analysis (FEA) model. The performance of a commercial-scale silo was then characterized using the validated model. The commercial-scale model predicted a storage efficiency above 95% after 5 days of storage with a design storage temperature of 1200 ∘C. Insulation material and concrete temperature limits were considered as well. The validation of the methodology means the FEA model can simulate a range of scenarios for future applications. This work supports the development of a promising LDES technology with implications for grid-scale electrical energy storage, but also for thermal energy storage for industrial process heating applications.

Energy-efficient production of sustainable industrial process heat with a parabolic dish-conical cavity solar collector

Industrial decarbonization in response to global carbon neutrality requires vast process heat to be supplied in a low-carbon manner. Solar energy is regarded as one of the most promising alternatives to fossil fuel applied for heat-driven industrial processes, however, lack of effective approaches to improve the solar-thermal conversion efficiency is a longstanding issue. Here, we propose an efficient approach to produce industrial process heat based on a novel concentrated solar collector, mainly consisting of a parabolic dish concentrator and a conical cavity receiver. Results showed that the collector was competent to supply the process heat meeting various low-temperature industrial occasions, and there was an optimum flow rate to achieve a trade-off between the outlet temperature of working fluid and thermal efficiency of the solar collector. The thermal efficiency of the proposed solar collector was 2.7%–27.5% higher than that of most other existing collectors used for production of low-temperature process heat, and such a superior solar-thermal conversion efficiency was a consequence of the reduction in energy losses between the solar receiver and surroundings as confirmed by the comprehensive energy analysis performed in this study.

Impact of Temperature and Optical Error on the Combined Optical and Thermal Efficiency of Solar Tower Systems for Industrial Process Heat

Concentrating solar thermal (CST) power towers can provide high flux concentrations at commercial scale. As a result, CST towers exhibit potential for high-temperature solar industrial process heat (SIPH) applications. However, at higher operating temperatures, thermal radiation losses can be significant. This study explores the trade-off between thermal and optical losses for SIPH applications using a collection of three case studies at operating temperatures that range from 900-1,550 °C. We assume blackbody radiation to represent the thermal losses at the receiver and we use ray tracing to estimate the optical losses. The results show the impact of process temperature on the maximum attainable system efficiency, as well as the higher flux concentration requirements as the temperature increases.