Supplemental Heat Research Articles

INTERACTIVE IMPACT OF THE SPECTRAL COMPOSITION OF ADDITIONAL LIGHTING AND ROOT ZONE TEMPERATURE ON THE PRODUCTIVITY OF HYDROPONIC LETTUCE

Hydroponic lettuce production in greenhouses is becoming increasingly popular in Ukraine. However, there is a lack of research evaluating the impact of light spectra, root zone temperature, production systems, and lettuce varieties on yield. This study aims to determine the interactive effects of nighttime supplemental lighting, nutrient solution temperature, and production system on the growth and productivity of various lettuce varieties under suboptimal air temperatures typical for winter greenhouses. The study used three lighting regimes: no lighting (control), violet LEDs (spectrum R90:G0:B10), and warm white LEDs (spectrum R35:G42:B23). Two nutrient solution temperatures—12.6 °C (no heating) and 18.8 °C (with heating)—as well as two production systems—Nutrient Film Technique (NFT) and Constant Flood Table (CFT)—were applied for lettuce cultivation. Red and green lettuce varieties of four types were studied: leafy, heading, oakleaf, and romaine. The results showed that the absence of supplemental lighting and heating significantly reduced yield, while their combination positively influenced the dry mass of shoots. The highest productivity was achieved with the CFT system, especially when combined with violet LEDs, which had a higher red light component that stimulates plant growth. It was found that violet lighting significantly outperformed white LEDs, particularly when the nutrient solution was heated. The most sensitive lettuce varieties to root zone conditions and lighting were Adriana, Cedar, Red Sails, and Salvia. In particular, under violet LEDs, these varieties showed the highest productivity when the CFT system was used. This research suggests effective strategies for optimizing hydroponic lettuce cultivation in winter greenhouse conditions in Ukraine. The findings can be useful for farmers aiming to increase yield and product quality, as well as for optimizing costs under conditions of limited resources.

Effect of Rotational Speed on the Microstructure and Texture of Thermomechanically Affected Zone of Al6082-T6 Friction Plug Welding Joint

AbstractExperiments were performed on Al6082-T6 using friction plug welding to investigate and resolve keyhole faults. The process required using friction as supplemental heating which was from between the shoulder and base metal. Friction plug welded connections were successfully created at rotational speeds of 1600 rpm, 1800 rpm, and 2000 rpm. The weld joints have no apparent structural flaws, and the joints demonstrate distinct partition features. During them, the thermomechanically affected zone of joints displays a distinct boundary between the base metal and plug, accompanied by a pronounced, preferred orientation. It can be deduced that augmenting the plug's rotational speed, the size of grain and the composition of high-angle grain boundaries will facilitate dynamic recrystallization and lead to a more pronounced recrystallization texture composition, assuming all other parameters remain constant.

Enhancing smart building performance with waste heat recovery: Supply-side management, demand reduction, and peak shaving via advanced control systems

With the increasing use of smart building technologies in modern infrastructures, a growing focus is on developing intelligent energy systems. This study focuses on a crucial part of this transition by investigating the application of a rule-based control method to harness the heat from wastewater to warm the ventilation lines in residential buildings. This research intends to enhance the integration of smart buildings into modern energy systems by prioritizing optimal performance and using creative control methods, mainly robust rule-based control schemes, thereby addressing current gaps and contributing to overall improvement. The proposed system’s effectiveness is assessed and compared with a conventional model without the developed smart strategy from all facets. The system’s performance was assessed using hourly, monthly, seasonal, and annual metrics, with a detailed sensitivity analysis conducted to evaluate the proposed control strategy’s practicality. The findings reveal that the intelligent ventilation system achieves approximately 10% higher efficiency and conserves over 1.4 tonnes of CO2 emissions annually. Economically, the model demonstrates its feasibility through a marked reduction in heating costs, decreasing from 54.9 USD/MWh to 30.7 USD/MWh despite an initial investment of 29,032 USD. The results also show that the smart integration system maintains elevated supply air temperatures during colder months, enhancing thermal efficiency and reducing reliance on external heat sources. Economic analysis further identifies the energy wheel as the largest cost component, representing 50% of the total investment. Monthly variations in heat recovery from wastewater and production via the energy wheel suggest that integrating these elements through a dynamic control system leads to significant operational savings and reduces the need for local district heating. During peak demand periods, radiators serve as the primary heating source. Air-handling units provide necessary ventilation and supplemental heating, allowing for efficient energy distribution and management across all seasons.

Hybrid heating in the fused filament fabrication process

AbstractAltering the heating regime of the polymer during the fused filament fabrication (FFF) process can lead to changes in both the behaviour of the polymer and the characteristics of the printed product. This study proposes replacing the traditional resistive heating system with two hybrid systems that introduce an additional temperature of 120–160 °C: one combining resistive and hot air jet heating, and the other combining resistive and infrared radiation heating. The samples printed using these hybrid systems were analysed using differential scanning calorimetry (DSC) and visually inspected. Commercial ABS and PLA filaments were used in the experimental programme. A model to evaluate the polymer’s melting during the printing process was proposed and experimentally validated. Visual testing revealed that the printed lattice structure had smaller voids, characterised by depositions that were flattened rather than circular in cross-section due to the extended time in a viscous/partially molten state. The elongation viscosity and storage modulus decreased by approximately 10%, with a slightly smaller decrease observed for the infrared radiation heat source. The glass transition temperature remained unchanged, and the molecular mobility was not affected by the additional heat. Similarly, the energy required for crystal formation was unaffected by the supplementary heat. The mechanical behaviour of the printed pieces during compression tests was also influenced by the addition of a second heat source. For both materials, a decrease in deformability was observed as the temperature of the hot air jet increased.

Comparative thermal model analysis and experimental validation for predicting performance of a pyramidal solar still with integrated pulsating heat pipe

Developing nations face a dire situation as water scarcity and pollution significantly impact various aspects of life. It's crucial to take action now to address these pressing issues and ensure a sustainable future for all. Solar desalination processes emerge as a promising solution to these pressing problems in water purification technologies.This paper reports the thermal modeling and experimental results of two solar still designs, namely (i) Pyramidal solar still with pulsating heat pipe (PHP), Modified pyramidal solar still (MPSS), and (ii) conventional pyramidal solar still (CPSS). This study uses energy balance equations to focus on MPSS and CPSS thermal modeling. In the MPSS, a PHP, in conjunction with a solar collector, provides external heat to basin water. Several models, including Dunkel, Kumar and Tiwari, Chen, and Zheng Hongfei, are utilized to estimate the performance of both MPSS and CPSS. Extensive experiments have been conducted for validation purposes. Key parameters considered for prediction and comparison include evaporative heat transfer coefficient, convective heat transfer coefficient, total heat transfer coefficient, and hourly yield. It is noted that the Kumar and Tiwari model demonstrates a superior ability to predict cumulative yield, with a percentage error of 5.81 % and 5.9 % for MPSS and CPSS, respectively, compared to the experimental cumulative yield. The theoretical average basin water temperature observed in MPSS is 64.56 °C, and CPSS is 58.8 °C. The enhancement in temperature is attributed to the supplementary heat provided by the PHP.

A Technical-Economic Assessment of Producing Hydrogen and Biofuels via Gasification of Biomass in Solar Hybridised Dual Fluidised Bed

In this work, the techno-economic performances of three conversion pathways using an upstream solar hybridised dual fluidised bed (SDFB) for biomass gasification were assessed. The annual solar share % over the solar multiple range of 1.4-3.4 varies between 7-17%, with the CO2 emissions avoided relative to the non-solar case varying between 7%-23%, using representative solar viability location in Australia. The projected break-even price varies between 5.5-6.1 AUD/kg (3.8-4.25 USD/kg) for hydrogen, 1.1-1.2 AUD/kg (0.75-0.85 USD/kg) for methanol, and 1.5-1.7 AUD/L (1.1-1.2 USD/L) for liquid fuels over the analysed oversize level of 1.4 to 3.4 at thermal storage capacity designs with less than 1% solar dumping rate for base case scenario. Overall, the derived break-even price from the SDFB gasifier configuration is higher than that of the non-solar gasifier case, yet this is dependent on the cost of supplement heat supply and carbon credit

Analysis of in-bin low-temperature and high-temperature grain drying in Alberta: Specific energy, carbon costs and policy implications

Optimizing grain drying process is pivotal for both economic viability and environmental sustainability. In cold countries, supplemental heating is paramount but instigates the issue of carbon release at the same time. To curve the emission, a carbon levy has been imposed that varies with fuel types. However, there is limited knowledge of the impact of field-adaptable technologies utilizing commercialized fuels on the optimal execution of grain drying. To explore this, a comprehensive three-year on-farm grain drying study was conducted in the province of Alberta, Canada. This comparative analysis centered on three critical aspects, i.e., specific energy consumption, greenhouse gas emissions (GHGs), and operating costs. Furthermore, the research extended its projections into the year 2030, accounting for the impact of gradual carbon levies on natural gas, propane, and diesel fuel systems. Resultsshowed that indirect heaters in in-bin systems were 38 % more energy-efficient than direct heaters due to better airflow and higher initial grain temperatures, while indirect heaters with diesel burners exhibited 27.8 % lower burner turndown ratios and 35.4 % higher energy consumption than natural gas counterparts. In high-temperature drying, natural gas consumption decreased as supply air temperatures rose, with double-flow dryer showing the lowest energy consumption (6.3±1.9 GJ/t) in comparison to mixed-flow and cross-flow dryer due to waste heat recovery. Heaters and Dryers operated at varying load capacities, indicated 126–135 % increase in natural gas cost with carbon levy by 2030. Achieving lower specific energy consumption in grain drying requires precise burner and process control, along with maintenance, offering valuable guidance for producers.

Impact of refrigerant undercharge faults on building indoor conditions and HVAC system operation in residential Buildings: A simulation study

This study investigates the impact of refrigerant undercharge on indoor temperature and HVAC system performance in residential buildings. Simulation models for typical residential buildings in Orlando, FL and Indianapolis, IN were developed using the ResStock database. A refrigerant undercharge fault model was then applied to the simulations with varying levels of fault intensity. The paper offers an extensive analysis, revealing that variations in supply air temperature, equipment runtime, and cooling energy consumption due to the level of refrigerant undercharge faults are notably significant on a summer representative day. Similarly, on a winter representative day, changes in supply air temperature and runtime are significant as well as changes in supplemental heat energy consumption. We find that occupants may remain oblivious to these faults during the cooling season, particularly when the HVAC system is oversized; in that case, supply air temperature data could help detect a fault. Another challenge is that during the heating season, when the supplemental heater operates, it is difficult to identify a refrigerant undercharge fault using only indoor and supply air temperature data. This study finds that supply air temperature, equipment runtime, and supplemental heater energy consumption data can help in detecting refrigerant undercharge faults.

Experimental study on Fuel Heating of A Gas Turbine Engine

In order to mitigate the latent hazards caused by fuel retention in the gas turbine and ensure a higher ignition success rate, an investigation was conducted on the impact of fuel heating on the gas turbine. By incorporating a fuel heating device into the gas turbine, experiments were carried out to evaluate its heating performance at different positions within the fuel system. The objective was to elevate the temperature of the main fuel pipe prior to ignition, thereby reducing ignition success speed and guaranteeing successful combustion initiation. The findings revealed that placing the fuel heating device at the outlet of the fuel control device met all requirements; however, positioning it before this device failed to meet expectations. Furthermore, when subjected to heat, this particular heating device did not accurately reflect actual fuel temperature; additionally, relying solely on circulating heat within the existing fuel system proved inadequate. Consequently, based on these test results, an optimal solution involving supplementary heating devices was determined - a decision that holds immense significance for ensuring steady operation of gas turbines.

DEVELOPMENT OF A SYSTEM WITH SUSTAINABLE SUPPLEMENTAL HEATING: AN ALTERNATIVE TO COMBAT WATER SCARCITY

The scarcity of water resources has led researchers to investigate and develop mechanisms for the good use of saline and brackish waters to produce drinking water. In Brazil, the water crisis has always been a reality. The objective was to carry out desalination through a prototyped system with sustainable supplementary heating, to help supply drinking water to residents who face precarious living conditions. The research is aimed at the Bailique Archipelago and Sucuriju District, located in the extreme east of the State of Amapá and bathed by the Atlantic Ocean. It presents a quali-quantitative analysis, as it involves the construction of the prototype and temperature and physical-chemical tests of water samples. Regarding the results, desalination was carried out using a prototype, with subsequent analysis of the physical-chemical conditions of the interstitial waters to correlate with the potability parameters. The supplementary heating positioned on the sides of the system converged solar rays towards the greenhouse that contains salt water inside, and a device on the glass slope collected the condensed water. The 50cm x 50cm model desalinated 890mL and the 25cm x 25cm model desalinated 190mL of water in one day, reaching a maximum temperature of 91 ºC.

Simulation study on the system performance of solar-ground source heat pump using return water of the district heating network as supplementary heating

In order to mitigate the extreme climate change and improve the utilization of renewable resources, a solar-ground source heat pump system using return water of the district heating network as supplementary heating(SGSHP-DHNSH)has been proposed. This system compared with parallel and series connections of solar assist ground source heat pump systems for simulation and analysis. The results indicate that the SGSHP-DHNSH system raises the evaporation temperature, demonstrates a high rate of renewable energy utilization, and efficiently stores heat within the buried pipes. Notably, the soil temperature in the SGSHP-DHNSH system experiences only a 0.16 °C decrease, which represents reductions of 8 % and 9.8 % compared to the series and parallel systems, respectively. Furthermore, the system COP demonstrates a commendable improvement of 20 % and 13.7 %, the evaporator inlet temperature is higher than the series and parallel systems by 6.7 °C and 5.3 °C, respectively. Moreover, the total energy consumption throughout the heating season stands at 63 MW h, reflecting a substantial 24 % and 19 % reduction in comparison to the series and parallel systems, respectively. The SGSHP-DHNSH system plays a crucial role in improving the utilization rate of renewable resources and alleviating the soil heat imbalance caused by ground source heat pump operation.

Unravelling jet quenching criteria across L* galaxies and massive cluster ellipticals

ABSTRACT In the absence of supplementary heat, the radiative cooling of halo gas around massive galaxies (Milky Way mass and above) leads to an excess of cold gas or stars beyond observed levels. Active galactic nucleus jet-induced heating is likely essential, but the specific properties of the jets remain unclear. Our previous work concludes from simulations of a halo with $10^{14} \,\mathrm{ M}_\odot$ that a successful jet model should have an energy flux comparable to the free-fall energy flux at the cooling radius and should inflate a sufficiently wide cocoon with a long enough cooling time. In this paper, we investigate three jet modes with constant fluxes satisfying the criteria, including high-temperature thermal jets, cosmic ray (CR)-dominant jets, and widely precessing kinetic jets in $10^{12}-10^{15}\, {\rm M}_{\odot }$ haloes using high-resolution, non-cosmological magnetohydrodynamic simulations with the FIRE-2 (Feedback In Realistic Environments) stellar feedback model, conduction, and viscosity. We find that scaling the jet energy according to the free-fall energy at the cooling radius can successfully suppress the cooling flows and quench galaxies without violating observational constraints. On the contrary, if we scale the energy flux based on the total cooling rate within the cooling radius, strong interstellar medium cooling dominates this scaling, resulting in a jet flux exceeding what is needed. Among the three jet types, the CR-dominant jet is most effective in suppressing cooling flows across all surveyed halo masses due to enhanced CR pressure support. We confirm that the criteria for a successful jet model work across a wider range, encompassing halo masses of $10^{12}-10^{15} {\rm M_\odot }$.

Understanding the thermodynamic effects of chemically reactive working fluids in the Stirling engine

The Stirling engine, renowned for its high theoretical efficiency, is capable of partaking an active role in the current energy transition. Given its closed-cycle operation, the choice of the working fluid is pivotal in designing the Stirling engine. Dinitrogen tetroxide N2O4 has been extensively investigated in the past, based on the ideal gas thermodynamic model, as a chemically reactive working fluid for Stirling cycles. This molecule reversibly and rapidly dissociates into nitrogen dioxide NO2–and recombines into N2O4–under the influence of thermodynamic transformations throughout the cycle, in accordance with chemical equilibrium. Addressing discrepancies in previous studies, this work aims at assessing a wide range of theoretical chemically reactive gases as working fluids in a Stirling cycle, employing the ideal gas mixture model. The behavior of each reactive fluid is examined throughout the cycle, and the thermodynamic performance is evaluated. Therefore, this work quantifies and analyzes the thermodynamic performance of a chemically reactive Stirling engine. Results indicate a slight increase in the net specific work output with certain reactive fluids, offering a thermal efficiency comparable to that of inert working fluids. In addition, it is emphasized that for chemically reactive working fluids, the isochoric heat exchange within the internal regenerator is incomplete due to chemical reactions, in contrast to the case of inert fluids. To address this, either a supplementary heat source, heat sink, or both are required during the isochoric processes. Furthermore, chemically reactive fluids in the Stirling engine induce irreversibility in the internal regenerator, stemming from heat exchange across a finite temperature difference, penalizing the thermal efficiency of the engine for the majority of reactive fluids studied.

An Analysis of Households Choice of Solid Fuels as a Primary and Supplementary Heating Fuel

The residential sector in Ireland is a large user of solid fuels for space heating purposes. Solid fuels are commonly used to supplement other forms of heating rather than as the primary source. Using a survey data set of Irish households and a multinomial logit approach, differences between the household characteristics of primary and supplementary solid fuel users are identified, including for levels of education, age of dwelling, location and pro-environmental attitudes. Evidence also shows that increases in income lead to a transition away from primary solid fuel use but not supplementary consumption, suggesting that an energy stacking model explains the household’s choice of heating fuels in Ireland. Given the established effects that solid fuels have on air quality and the scale of supplementary solid fuel use, policies to promote a transition to cleaner fuels need to account for the clear differences in the features of the two user groups.

Characterising the effects of geometry on the natural convection heat transfer in closed even-span gable-roof greenhouses

Over the years, researchers have attempted to reduce the heat loss that arises from the natural convection in confined even-span gable-roof greenhouses due to the temperature difference between the floor and the walls (particularly at night and during winter). However, the effect that the geometry of these greenhouses has on this natural convection does not appear to have been systematically investigated.To address this, this study examined the influence of aspect ratio and roof pitch of greenhouses on the natural convection inside them. In this vein, a numerical model was developed using computational fluid dynamics (CFD) and validated against experimental data. It was found that decreasing the aspect ratio and roof pitch typically reduced the natural convection heat transfer, with changes of up to 25% for aspect ratios and 15% for roof pitch angles being observed. This suggests that a low-profile greenhouse with a low roof pitch offered the best opportunity for reducing heat loss. That said, under some conditions a multicellular flow regime can occur, and this leads to an increase in the heat transferred from the greenhouse. Hence, the choice of aspect ratio and roof pitch angle require careful consideration.Finally, a parametric relationship was developed to assist greenhouse designers determine their heat loss for a range of greenhouse geometries. Designers of greenhouses are encouraged to take advantage of the proposed relationship to develop model-based control strategies that minimize supplementary heating and deliver energy efficient greenhouses into the future.

The techno-economics of transmitting heat at high temperatures in insulated pipes over large distances

This study reports a systematic techno-economic assessment of the cost-optimal transmission for air as the heat transfer fluid at temperatures of up to 1200 °C, at scales of 1 to 1000 MW and at distances of up to 10 km. It employs a steady state heat transfer analysis, with energy balances, to assess the effect of scale, temperature and insulation on the heat losses and efficiency of the thermal transmission system, following by a techno-economic assessment. The sensitivity of the Levelised Cost of Heat, LCOHtr, to variations in thermal scale, operating temperature, distance, refractory and insulation thickness, ratio of the thickness of refractory and insulation, cost of any supplementary heat and lifetime is reported. The results show that LCOHtr decreases with an increase in thermal scale, as expected. The role of insulation is much more complex, since increasing the thickness of thermal barrier increases both cost and efficiency of the transmission, requiring an economic optimum to be determined for each of the various conditions assessed. Parameters are also coupled because a higher cost of supplied energy/ heat justifies the use of more insulation material. For a large GW scale thermal system, we estimate that it is possible to achieve a minimum overall LCOHtr,min of 0.16–0.36 USD/GJ/km of the length of the thermal transmission system, excluding additional location-specific costs such as land-access and local construction costs. These estimated costs are sufficiently attractive to justify ongoing development of systems to transport renewable heat to industry from sources such as concentrated solar thermal energy.

Dynamic Modeling of a Solar-To-Hydrogen Flexible High Temperature Steam Electrolysis Plant

Sustainble hydrogen production for use as a renewable combustible fuel and clean chemical feedstock is an important objective as the world moves towards a renewable energy future. High temperature steam electrolysis is a promising hydrogen production technology due to its reduced electric input that is offset by heat input into steam generation and steam superheating. An option to provide this heat is to use concentrating solar thermal technology that can sustainably provide heat input while renewable electricity is used for the electrolysis reaction. In this work, a solar-to-hydrogen high temperature steam electrolysis plant is designed and dynamically modeled, showing continuous hydrogen production by utilizing supplemental heating and efficient recuperative heating from the electrolysis product streams. Through this design, over 90% of the required heat input for the process can by met by a combination of solar and recuperative heat. Additionally, the plant can flexibility operate by ramping down hydrogen production and through flexible heat integration, which intelligently integrates solar heat based on solar conditions. Smooth operation with flexible hydrogen production is demonstrated which decreases electrical input during on-peak grid times and also decreases the total supplemental heat load over the course of a day from 26.1% to 24.5%. In addition, by using flexible heat integration, the plant can increase its solar heat usage by 4.1% relative to a base case. Both options for flexibility show efficient use of solar thermal energy to sustainably and continuously produce hydrogen.

Dimensional Variation and Parametrical Feasibility for Utilizing Aluminum Cast-House Flue Gases to Supplement Heat for the Organic Rankine Cycle (ORC)

Dimensional Variation and Parametrical Feasibility for Utilizing Aluminum Cast-House Flue Gases to Supplement Heat for the Organic Rankine Cycle (ORC)

Application of Solar Energy to Liquify Beewax

This study investigates the feasibility of using solar energy for melting recycled older combs and capping wax byproducts to create raw beeswax. The solar-driven beeswax melter is composed of a stainless steel container, a lean-to structure featuring polycarbonate sheet covers, a wooden solar heater, and parallel arrays of PV solar panels. The research contrasts three distinct approaches for melting beeswax: the conventional water bath technique, exclusive reliance on solar energy for melting, and the combination of solar energy and supplementary heat from solar panels. The traditional water bath method's effectiveness and the bulk temperature of the liquified beeswax were gauged. In the case of the solar-powered wax melting setups, the process's efficiency, the melted wax's bulk temperature, and various macroclimatic factors such as sunlight radiation, temperature, and relative humidity were documented. Based on the experimental outcomes, the beeswax melting efficiency was determined to be 73.4% for the traditional water bath method, whereas it escalated to 85.5% and 87.2% for the solar approaches, respectively. Hence, the utilization of solar techniques for beeswax melting is recommended.

Microstructure and mechanical properties of AlTiCrFe and AlTiCrCu alloys processed by Laser Powder Bed Fusion

Additive manufacturing (AM) of aluminium alloys urges new alloy compositions to meet the requirements for high-strength and processability of the engineering products. This research focuses on the development of two Al alloys, AlTiCrFe and AlTiCrCu, with the goal to exploit the potential of transition element additions for grain refinement and increasing strength. Robust processability and build rates are reached for the two alloys, with no cracks and high density up to 99.8%. AlTiCrFe shows a bimodal microstructure, with the presence of ultrafine and fine grained zones, that can be attributed to a dual precipitation stage. Al3Ti precipitates are present in the ultrafine grained zone, confirming the effectivity of Ti as grain refiner. In addition, Al6Fe precipitates are present in the fine grained region, as a consequence of the later precipitation stage. AlTiCrCu, on the contrary, shows an homogeneous ultrafine grain microstructure, with Cu segregating at the grain boundaries. SAED analyses confirm the phase identification with the presence of high volume density cubic precipitates of Al3Ti_L12. AlTiCrFe and AlTiCrCu exhibit a yield strength value of 363 ± 1 MPa and 340 ± 1 MPa, respectively. These findings indicate that the two alloys open up new possibilities for a novel class of aluminium alloys for AM, leveraging the incorporation of transition elements, which aids in achieving strength during the as-built state, eliminating the requirement for supplementary heat treatment.