Alternative Heat Source Research Articles

Thermal Analysis of Infrared Heater as an Alternative Heat Source for Flexitank Application Using CFD

The heating pad was a mechanism for heating elements using steam as a heat source and heating the liquid inside a flexitank to liquidise for easy discharge completely. Alternative heat sources such as infrared, electric, and exothermic reactions may improve thermal performance for the heating process. Infrared heating is chosen for this study due to its efficient radiation heat transfer compared to conduction and convection. This study aims to determine the optimal infrared heater configuration to improve the time to liquidify fluid on the flexitank for easier discharge. Nine flexitank and infrared heater geometries were made using SolidWorks with different heater positions and heating element thicknesses. Each geometry was simulated using Ansys Mechanical to study the thermal performance of radiation heat transfer with three different heating element materials. The heat output and energy input obtained from the simulation were used to calculate heating time and energy efficiency, respectively. The effects of each parameter were studied to determine the best configuration of the infrared heater in terms of heating time, energy consumption and both. The results showed that the position of the heater plays the most crucial role in determining the heating time and energy consumption, as a heater position that produces a larger heated surface area on the flexitank can reduce heating time. The thickness of the heating element and its material contributes a minor impact on heating time and energy consumption. Increasing thickness would lower the heating time and increase energy efficiency if the thickness improves heat retention capabilities. Increasing material emissivity will increase the heating time. Higher conductive materials would use more energy compared to lower conductive materials. The heating time was improved by about 30% compared to a steam heating pad. Energy consumption was reduced by about 85% compared to a small steam generator. In conclusion, the infrared heater was a promising alternative as a heat source for flexitank applications.

The use of a trench candle as an alternative heating and light source in wartime and possible negative consequences

The use of a trench candle as an alternative heating and light source in wartime and possible negative consequences

Anisotropic MXene@polydopamine- and Dialdehyde Carboxymethyl Cellulose-Modified Collagen Aerogel Supported Form-Stable Phase Change Composites for Light-To-Heat Conversion and Energy Storage.

As a renewable alternative heat source, the inherently intermittent feature of solar energy needs to be coordinated by reliable energy conversion and storage systems for utilizing the most abundant solar energy. Phase change materials (PCMs) are supposed to be advanced mediums for storing a great deal of heat generated by solar light. However, PCMs cannot effectively absorb and utilize solar energy due to leakage, low photothermal conversion efficiency, and poor thermal conductivity. Herein, we developed a collagen-based aerogel modified by dialdehyde carboxymethyl cellulose and polydopamine-modified two-dimensional transition-metal carbide/nitride (MXene@PDA) through bidirectional freeze-drying technology for supporting PCMs, which exhibited anisotropy in structure and properties. In particular, the thermal conductivity of the aerogel was 0.0871 W/(m·K) in the axial direction and 0.0504 W/(m·K) in the radial direction, demonstrating its anisotropic thermal insulation performance. Moreover, the final aerogel composite PCMs had been obtained via impregnating the obtained aerogel supporting matrix into polyethylene glycol (PEG) and hydrophobic treatment of polydimethylsiloxane, which exhibited outstanding solar-thermal conversion ability, good thermal storage capacity, advanced leakage-proof property, and antifouling performance. The loading rate of PEG was as high as 92.2%, and the melting enthalpy was 132.6 J/g. Most importantly, the water contact angle was evaluated to be 156.8°, indicating its superior antifouling performance. This material has intensive application prospects in the fields of solar energy collection, conversion, and storage.

Self-powered sensors utilizing single-pillar thermocells with pyrolytic graphite sheet electrodes: harvesting body heat and solar thermal energy

This study investigates the development of self-powered sensors employing single-pillar thermocells to harness body heat and solar thermal energy. A pyrolytic graphite sheet was selected for its low water vapor permeability, and its surface was modified to be hydrophilic to minimize interfacial resistance. Two types of DC–DC converters, Asahi Kasei Microdevices AP4473 and matrix mercury, underwent evaluation for compatibility with these thermocells. The compact 1.5 cm3 (1 cm × 1 cm × 1.5 cm) device effectively powered the AP4473 converter, illuminating a light-emitting diode. A larger device (2.5 cm × 2.5 cm × 1.5 cm) efficiently drove the matrix mercury converter, enabling the operation of bluetooth low-power sensors. These self-powered sensors wirelessly provided humidity and temperature data using solar thermal energy for approximately 4 h per day during peak temperature differences in January. This study showcases the potential of thermocells for sustainable energy harvesting and suggests avenues for future research, such as exploring alternative heat sources like geothermal energy to power these sensors.

Ecological-Based Mining: A Coal–Water–Thermal Collaborative Paradigm in Ecologically Fragile Areas in Western China

A substantial reduction in groundwater level, exacerbated by coal mining activities, is intensifying water scarcity in western China’s ecologically fragile coal mining areas. China’s national strategic goal of achieving a carbon peak and carbon neutrality has made eco-friendly mining that prioritizes the protection and efficient use of water resources essential. Based on the resource characteristics of mine water and heat hazards, an intensive coal–water–thermal collaborative co-mining paradigm for the duration of the mining process is proposed. An integrated system for the production, supply, and storage of mining companion resources is achieved through technologies such as roof water inrush prevention and control, hydrothermal quality improvement, and deep-injection geological storage. An active preventive and control system achieved by adjusting the mining technology and a passive system centered on multi-objective drainage and grouting treatment are suggested, in accordance with the original geological characteristics and dynamic process of water inrush. By implementing advanced multi-objective drainage, specifically designed to address the “skylight-type” water inrush mode in the Yulin mining area of Shaanxi Province, a substantial reduction of 50% in water drillings and inflow was achieved, leading to stabilized water conditions that effectively ensure subsequent safe coal mining. An integrated-energy complementary model that incorporates the clean production concept of heat utilization is also proposed. The findings indicate a potential saving of 8419 t of standard coal by using water and air heat as an alternative heating source for the Xiaojihan coalmine, resulting in an impressive energy conservation of 50.2% and a notable 24.2% reduction in carbon emissions. The ultra-deep sustained water injection of 100 m3·h−1 in a single well would not rupture the formation or cause water leakage, and 7.87 × 105 t of mine water could be effectively stored in the Liujiagou Formation, presenting a viable method for mine–water management in the Ordos Basin and providing insights for green and low-carbon mining.

Disassembly analysis of hot-melt adhesive in mechanical joints

The mechanical properties of a commercially available hot-melt adhesive (HMA) have been studied under different environmental and loading conditions. To date, disassembly analyses including triggering features, design parameters, and time have not been fully investigated in the literature. In this study, experimental parametric studies have been performed on single lap joints considering the geometric features of the joint and a combination of thermo-mechanical effects. Disassembly time has been assessed through experimental analysis, considering variations in geometry, the use of alternative heat sources and different load conditions. Use of a heat gun as the heat source was found to lead to the highest variation in disassembly time compared to a static climatic chamber (i.e., industrial oven). In relation to the joint geometry, the disassembly time was mostly affected by the overlap length rather than the type or thickness of the base material. The outcomes of this study will drive the design of adhesive joints in mechanical applications, providing design-for-disassembly guidelines for the development of reversible joints employing hot-melt adhesives.

Testing The Heat Distribution of Flat Plate Type Solar Collectors for LPG Solar Hybrid Dryers at P4S Bukit Melintang

One of the uses of solar energy in agriculture is as a source of heat energy for dryers. Through the Kedaireka 2023 Matching Fund (MF) activity and in collaboration with the Independent Rural Agricultural Training Center (P4S) of Bukit Melintang, Sidrap Regency to develop a hybrid solar and LPG dryer. Thermal energy from the sun is obtained from a flat plate-type solar collector system. This research aims to obtain a flat plate-type solar collector system as an alternative heat source for hybrid dryers. The research was carried out to test the functional tool and determine its performance in converting solar energy into heat that can be used for drying equipment. The results of tests carried out on October 22, 2023, from 10.25 AM to 13.35 PM at the Agricultural Engineering Study Program, Hasanuddin University, with coordinates -5.131048, 119.485434 showed that the average environmental temperature was 36.5 °C, the highest temperature in the solar collector outlet was 57 °C which occurred at 11.15 – 11.40. and experienced a decrease in temperature until 13.35 to the lowest temperature of 42.5 °C. This shows that the solar collector can increase the temperature from 60 to 20.5 °C.

Environmental impact of Danish organic tomatoes grown in greenhouses: Quantifying the reduction potential from changes in energy supply towards 2030

The demand for organic food products, including tomatoes (Solanum lycopersicum, L. 1753), is growing. Heated greenhouse production is well described through life cycle assessment (LCA), but inventories reflecting organic production conditions are inadequate or missing. At the same time, energy systems in Europe are changing, which is expected to have a considerable impact on the emissions from the energy intensive greenhouse production. Thus, this study is assessing the current environmental impacts using LCA of an organic tomato production in a heated greenhouse, and estimate the expected changes to impacts due to changes in energy supply. The assessment is based on activity data from a commercial greenhouse production. Current organic tomato production where plants are transplanted into the greenhouse in the late winter has impacts of 1.06 kg CO2 eq., 7.22 × 10−4 N eq., 3.49 × 10−5 kg Sb eq., and result in 3.12 kg C deficit from land use while consuming 24.58 MJ of energy per kg organic tomato. The impacts from earlier started tomato cultures are higher, as increased yield does not remedy increased energy use. The result from current production shows that direct energy consumption is responsible for the main impact on climate change (78%), cumulative energy demand (75%), marine eutrophication (56%) and land use (62%). However, expected future changes in the energy system towards 2030 are likely to reduce life cycle environmental impacts considerably (reduction potential for climate change impact: 69%, cumulative energy demand: 48%, eutrophication potential: 47%, mineral, fossil and renewable resource depletion: 4%, land use: 48%) as intensity of the energy supply changes. Mitigation options such as increased energy efficiency, alternative heat sources and agronomic management decisions are further discussed.

Urban low-to-medium deep borehole field regeneration with waste heat from energy efficient buildings: A techno-economic study in Nordic climate

Due to large area requirement, ground-source heat pump (GSHP) systems with shallow boreholes are difficult to implement in dense urban areas. To address this limitation, alternative heat sources can be used to reduce heat extraction from ground or to inject regenerative heat to boreholes. This study investigates the techno-economic feasibility of utilizing two commonly available waste heat sources (waste air and wastewater) in urban environment. Passive and heat pump-assisted utilization are studied for apartment and office buildings, with varied borehole depth and two levels of urban density. Long-term GSHP system operation is simulated using iterative heat balance calculation and borehole dimensioning algorithms. The results show significant reduction in required borehole length with waste heat utilization, particularly in shallow borefields, with maximum reductions of 53.9% (apartment building) and 25.8% (office building). The studied waste heat sources are shown to enable a shallow borefield for otherwise insufficient borehole spacing, providing an alternative to deeper boreholes. However, waste heat only available during summer has limited impact on field sizing compared to a seasonally stable heat source. From an economic perspective, the levelized cost of heating could be reduced by 13.5% (apartment building) and 7.3% (office building) compared to baseline without waste heat utilization.

Comparison on drying characteristic, efficiency, unit drying cost and quality of maize dried by a novel multi-crop mobile dryer, existing industrial dryer and sun drying method

This research aimed to investigate the effects of different drying methods on drying characteristic, drying efficiency, unit drying cost and quality of maize grain dried by newly developed HSTU multi-crop mobile dryer (HMMD) which was operated by alternative heating sources such as LPG and electric heater (EH), existing HSTU multi-crop industrial dryer (HMID) which was operated by rice husk fired cyclonic furnace and sun drying method. The comparative drying experiments were carried out at the drying temperature of 60±5 °C, 70±5 °C and 80 ± 10 °C for HMMD-LPG, HMMD-EH and HMID, respectively, while sun drying was accomplished at 30±5 °C. The results indicated that the HMMD was capable of drying 820 ± 10 kg maize in each batch from 29.8 ± 0.87 % (wb) moisture to 14 ± 0.56 % (wb). Drying time in HMMD-LPG, HMMD-EH, HMID, and sun drying were 8.24 ± 0.18, 7.36 ± 0.17, 10.18 ± 0.16 and 16.14 ± 0.24 h, respectively, indicated that HMMD reduced time significantly for drying of freshly harvested maize. Unit drying cost in BDT/kg for EH and LPG integrated HMMD was 2.64 ± 0.17 and 1.69 ± 0.10, respectively, while lesser unit cost was found in HMID and sun drying methods. However, drying efficiency of HMMD-LPG was the highest (64.79 ± 1.21 %) while HMID exhibited the lowest drying efficiency (49.42 ± 1.63 %). Mechanically dried grain especially by HMMD-LPG was better or comparable in terms of nutritional quality than sun dried maize. HMMD-LPG and HMMD-EH dried grain exhibited a lower ΔE value than HMID and sun dried samples which indicated that the color properties were not affected so much by the drying method. Furthermore, maize samples dried in HMMD had lower microbial loads than other products. Therefore, the HSTU multi-crop mobile dryer with alternative heating source is recommended as an alternative drying technique for quick and safe management of high moisture maize at farm level in Bangladesh and other subtropical countries in contrast to weather depended sun drying method.

Differences in Direct Geothermal Energy Utilization for Heating and Cooling in Central and Northern European Countries

Geothermal energy has emerged as an alternative heating source that can replace fossil energy. This mature technology is already in use all over Europe, but there are significant differences in its use between European countries. One possible explanation for this phenomenon concerns societal differences directly related to geothermal energy, the topic that is investigated in this study. The present work proposes using the societal embeddedness level (SEL) method to analyze and compare the status of non-technical factors affecting geothermal energy use in Hungary, Iceland, Norway, Poland, and Slovakia. The method considers four dimensions: environment, stakeholder involvement, policy and regulations, and markets and financial resources. Only Iceland fully covers the four dimensions by reaching all the milestones in the SEL framework. Iceland has the advantage of a long history of active use of geothermal energy for domestic use. The other countries face challenges within several of the dimensions, while the form and cause of these challenges are specific to each country. The findings illustrate that to mitigate climate change and drive the energy transition forward, both technical and societal factors related to various renewable energy sources must be assessed.

Risk assessment in district heating: Evaluating the economic risks of inter-regional heat transfer networks with regards to uncertainties of energy prices and waste heat availability using Monte Carlo simulations

Most district heating (DH) networks are largely based on fossil or biogenic fuels. As these fuels are phased out or their use will be prioritized for other sectors respectively, significant amounts of alternative heat sources (heat pumps, waste heat, solar and geothermal energy) will be required. However, there are various uncertainties regarding the development of key factors such as energy prices and the availability of alternative heat sources. In addition, individual heat supply systems are competing with DH networks. This paper quantifies the economic risks of DH networks with respect to uncertainties in energy prices (electricity and biomass) and waste heat availability and compares them with individual heating systems. Therefore, a hypothetical inter-regional heat transfer network (“HTN”) in Austria is investigated as a case study and a Monte Carlo approach based on seasonal energy balances is used. The results show that in individual heating systems, uncertainties in energy prices have a strong influence on the economic risks. In contrast, HTNs can optimize the use of industrial waste heat at stable prices and integrate large scale heat pumps operating at low electricity prices as well as combined heat and power plants operating at high electricity prices, leading to a reduced dependency on the uncertainties of energy prices and thus a lower economic risk.

The Heat Transfer in Plate Fin Heat Exchanger for Adsorption Energy Storage: Theoretical Estimation and Experimental Verification of the Methodology for Heat Accumulation Process

Adsorption energy storage is a promising resource-saving technology that allows the rational use of alternative heat sources. One of the most important parts of the adsorption heat accumulator is the adsorber heat exchanger. The parameters of heat transfer in this unit determine how fast heat from an alternative energy source, such as the Sun, will be stored. For the design of adsorption heat accumulators, plate fin heat exchangers are mainly used. In this paper, the procedure for the estimation of the global heat transfer coefficient for the adsorber heat exchanger depending on its geometry is considered. The heat transfer coefficient for a LiCl/SiO2 sorbent flat layer under conditions of heat storage stage was measured. Based on these data, the global heat transfer coefficients for a number of industrial heat exchangers were theoretically estimated and experimentally measured for the adsorption cycle of daily heat storage. It was shown that theoretically obtained values are in good agreement with the values of the global heat transfer coefficients measured experimentally. Thus, the considered technique makes it possible to determine the most promising geometry of the plate fin heat exchanger for a given adsorption heat storage cycle without complicated experiments.

Energy production through residual heat harvesting from domestic/commercial fridges using nanostructured thermoelectric modules

Refrigerated food product merchants want their products to be well lit and attractive to customers on a 24 h daily basis. However, provide continuous illumination is both unappealing and inefficient. Refrigeration systems are considered as high energy consumption appliances. It is estimated that in those systems energy losses in the form of heat are more significant in the gas compressor and condenser than in the rest of the system, which reach up to 78%. Furthermore, if one takes into account that it represents a free heat source because it is a by-product of compressed gas and is covered by the cost of operating the gas compressor then compressor and condenser are an alternative heat source for the recovery of residual thermal energy, and convert it into electricity in a clean way for further purpose. In the present work, as proof of concept, a thermoelectric converter prototype for the self-powering of refrigerator's lighting system has been developed. System is based on enhanced performance nanostructured thermoelectric modules which present an increment of around 35% on the maximum output power in comparison to a reference device commercially available. Amazingly, the thermoelectric converter is capable to efficiently harvest heat from fridge condenser system, and power up continuously fridge lighting system itself. Hence, taking into consideration the global fridge volume in use is estimated to increase up to 9.5 billion by 2050, present proposal could have significant impacts and benefits to society, both energy and environmental context.

Development and analysis of a powder bed friction stir (PBFS) additive manufacturing process for aluminum alloys: A study on friction-stirring pitch (ω/v) and print location

Metallic components fabricated with powder bed fusion additive manufacturing (AM) processes are known to have defects arising from liquid-solid phase transformation. Friction stirring can be an effective alternative source of heat, as evidenced in some of the recently developed powder deposition-based solid-state AM processes. However, they possess practical issues such as making compacted powder feedstock beforehand, consolidation of powder filler inside the tool during deposition followed by necessary extrusion, and significant flash formation, among a few. This paper proposed a novel powder bed friction stir (PBFS) additive manufacturing process inside a specifically designed mould that could potentially mitigate such issues in the existing technologies. The process was successfully demonstrated by building single-track and parallel double-track 3D structures layer-by-layer from an AA6061 powder bed using a rotating non-consumable friction stirring tool. Furthermore, for a better understanding of the underlying process mechanics, deposits were analyzed for their surface topography, microstructural evolution, and mechanical performance under different heat inputs as well as different print locations. Different heat inputs were applied by varying the friction-stirring pitch (FS pitch) from ‘Low’ to ‘High’. The print locations analysis was carried out in a parallel double-track fabricated at the optimal FS pitch. The results revealed that the ‘High’ FS pitch yielded an increased percentage of recrystallized grains and a fraction of high-angle grain boundaries as well as a larger average grain size due to the high heat input, better material intermixing, and the dominance of continuous dynamic recrystallization. As a result, an improved mechanical performance, except for the microhardness, was observed. The ‘High’ FS pitch also exhibited an improved surface topography. The results also revealed that the relative dominance of the re-stirring-induced recrystallization and the reheating-induced plastic deformation was the key factor for the variation of the microstructure in the longitudinal, transverse, and short-transverse directions. A gradual decrease in the tensile strength was observed from the ‘Top’ to the ‘Bottom’ segments of the overlapped region, contrary to the central region of a track.

Optimizing the Technological Processes in Cogeneration Power Plants Based on Stirling Engines

The article outlines the advantages of using Stirling engines in small-capacity cogeneration power plants: versatility of the thermodynamic cycle, high efficiency, high environmental cleanliness of working fluids and spent media, the ability to operate on almost all types of conventional fuels and alternative heat sources. The characteristic features of cogeneration power plants based on the Stirling engine are given. The specific features of modeling the thermal cycle circuit and selecting its optimal parameters are considered taking a Stirling liquid piston engine as an example. To solve the practical problem of engine optimization, an economic criterion is proposed as a totality of engine operating parameters. Simulation results are presented, which show that Stirling liquid piston engines can be a promising option as energy converters in installations with a liquid metal coolant.

Inovasi Teknologi Pemanas Kumparan sebagai Solusi Berkelanjutan dalam Proses Pembakaran Bata untuk Mengatasi Dampak Lingkungan Negatif

This research aims to design and develop coil heater technology as an alternative heat source to replace wood in the brick-firing process. The research methodology involves the design of an efficient and environmentally friendly coil heater and its implementation in the brick production process. In this study, the performance of the coil heater is analyzed to ensure that the generated heat is sufficient for the brick-firing requirements. The research findings indicate that coil heater technology is capable of providing the necessary heat to achieve optimal temperatures in the brick-firing process. Furthermore, the use of this coil heater technology successfully reduces dependence on wood as the primary fuel source. The implementation of coil heater technology in the brick-making industry is expected to make a positive contribution to the environment and the sustainability of natural resources. This research stimulates innovation in the development of alternative technologies that can reduce carbon footprints and improve the overall efficiency and sustainability of brick production processes.

Age and petrogenesis of mafic granulites from central Madurai block, south India: implications on regional tectonics

AbstractThe Precambrian Southern Granulite Terrane (SGT) of south India is well-known for the preservation of high- to ultrahigh-temperature (HT-UHT) granulites, prominently exposed in its central part forming a linear belt referred to as the Kambam UHT belt. This belt also hosts widespread occurrences of mafic granulites that are observed in close spatial association with the HT-UHT granulites. This study presents detailed petrology, geochemistry and geochronology of representative mafic granulites from the area to understand their petrogenesis and tectonic setting. The results demonstrate that mafic granulites are low- to medium-K tholeiites, with continental arc affinity, formed by the partial melting of a subduction-modified enriched mantle source. The composition of the parent mantle source is modelled with a spinel/garnet lherzolite contribution ratio between 100/0 and 70/30, suggesting the mixing of spinel and garnet bearing melts during asthenosphere upwelling. Zircon U–Pb geochronology of mafic granulites constrains their emplacement between 612 Ma and 625 Ma, that subsequently underwent metamorphism between 581 Ma and 531 Ma. This overlaps with the timing of HT-UHT metamorphism in the Kambam UHT belt bracketed between 593 and 532 Ma. Zircon Hf isotopic studies reveal parent magma generation from reworked melting sources involving Archean and Proterozoic components. These results propose an alternative heat source for the formation of HT-UHT granulites in the Kambam UHT belt which can be designated as a major terrane boundary within the SGT.

Configuration method for combined heat and power plants with flexible electricity regulation

A net-zero emissions target has been set as the long-term climate goals by many countries and regions. Efficient utilization of renewable energy is an essential way to solve energy and environmental problems. China needs to change its fossil-based energy mix and achieve a deep low-carbon transition in the energy sector. The future development of thermal power plants is focused on improving the power peak-shaving capacity while ensuring a heating supply with economical and feasible methods. This study presents a reasonable evaluation model to analyze different cogeneration plant power peak shaving modes. It proposes an optimal configuration method for combined heat and power generation plant power peak shaving systems by combining their characteristics and applicability. The basic principle of this method is that the most profitable mode for each power peak-shaving depth must be selected to achieve the best overall economic benefit of the system. The absorption heat pump waste heat recovery method, the electric heat pump waste heat recovery method and the electric boiler method are suitable for bearing the base load, waist load and peak load of the power peak shaving, respectively. The analysis results of influence economic factors show that as the heating price of the alternative heat source increases, the electric heat pump waste heat recovery method assumes a larger capacity for power peak shaving. When the heating price of alternative heat sources is 30 yuan/GJ (about the heating cost of a coal-fired boiler) and 100 yuan/GJ (about the heating cost of a gas-fired boiler), the electric heat pump waste heat recovery method should bear the depth peak-shaving demand with the duration higher than 360 h and 110 h respectively.

High-Throughput Metal 3D Printing Pen Enabled by a Continuous Molten Droplet Transfer.

In metal additive manufacturing (AM), arc plasma is attracting attention as an alternative heat source to expensive lasers to enable the use of various metal wire materials with a high deposition efficiency. However, the stepwise material deposition and resulting limited number of degrees of freedom limit their potential for high-throughput and large-scale production for industrial applications. Herein, a high-throughput metal 3D printing pen (M3DPen) strategy is proposed based on an arc plasma heat source by harnessing the surface tension of the molten metal for enabling continuous material deposition without a downward flow by gravity. The proposed approach differs from conventional arc-based metal AM in that it controls the solidification and cooling time between interlayers of a point-by-point deposition path, thereby allowing for continuous metal 3D printing of freestanding and overhanging structures at once. The resulting mechanical properties and unique microstructures by continuous metal deposition that occur due to the difference in the thermal conditions of the molten metal under cooling are also investigated. This technology can be applied to a wide range of alloy systems and industrial manufacturing, thereby providing new possibilities for metal 3D printing.