Search Results (27)

The paper explores the application of heat pipes in thermal management for efficient heat dissipation, particularly in electrical equipment with high heat loads. Heat pipes are devices that transfer heat with high efficiency through the phase transition of the working medium (e.g., water, alcohol, ammonia) between the evaporator and the condenser, while they have no moving parts and are distinguished by their simplicity of construction. Different types of heat pipes—gravity, capillary, and closed loop (thermosiphon loop)—are suitable according to specific applications and requirements for the working position, temperature range, and condensate return transport. An example of an effective application is the removal of heat from the internal winding of a static energy converter transformer, where the use of a gravity heat pipe has enabled effective cooling even through epoxy insulation and kept the winding temperature below 80 °C. Other applications include the cooling of mounting plates, power transistors, and airtight cooling of electrical enclosures with the ability to dissipate lost thermal power in the order of 102 to 103 W. A significant advantage of heat pipes is also the ability to dust-tightly seal equipment and prevent the build-up of dirt, thereby increasing the reliability of the electronics. In the field of environmental technology, systems have been designed to reduce the radiant power of fireplace inserts by up to 40%, or to divert their heat output of up to about 3 kW into hot water storage tanks, thus optimising the use of the heat produced and preventing overheating of the living space. The use of nanoparticles in the working substances (e.g., Al₂O₃ in water) makes it possible to intensify the boiling process and thus increase the heat transfer intensity by up to 30% compared to pure water. The results of the presented research confirm the versatility and high efficiency of the use of heat pipes for modern cooling requirements in electronics and environmental engineering. Full article

The phasing out of most chemicals has created a demand for alternative methods to preserve grain quality and market value. Hermetic storage offers a chemical-free solution for pest control by creating an airtight environment that naturally leads to insect death. Adding oxygen scavengers can further enhance hermetic storage by accelerating oxygen depletion. However, no study has examined scaling hand warmers in hermetic storage bags used by large grain handlers and farmers. We evaluated the effects of 1, 2, or 3 hand warmers in 25-kg PICS bags and 2, 4, or 6 hand warmers in 50-kg PICS bags on oxygen consumption and grain quality. We hypothesized that doubling the number of hand warmers used in 25-kg to 50-kg PICS bags would maintain the same rate of oxygen reduction. Oxygen levels decreased as the number of hand warmers increased. Additionally, oxygen concentrations in 25-kg PICS bags with 1, 2, or 3 hand warmers closely mirrored those of 2, 4, or 6 hand warmers in 50-kg PICS bags, respectively. Using 2 or 3 hand warmers in 25-kg PICS bags and 4 or 6 hand warmers in 50-kg PICS bags reduced oxygen concentrations below the 5% threshold for pest suppression within 12 h and maintained it for at least 8 days. While a slight rise in relative humidity was observed with more hand warmers, this did not negatively affect seed moisture content or germination rates. Doubling hand warmers along with the bag size from 25 to 50 kg produced similar oxygen depletion rates. These findings are helpful for large grain handlers and farmers who use 50-kg hermetic bags to store seeds or specialty crops to maintain quality. Hermetic bags combined with hand warmers promote sustainability by reducing chemical usage and minimizing food and nutrient losses. Full article

The cowpea is a vital crop for low-resource farmers in the Sahel, but post-harvest losses due to insect pests remain a major challenge. Callosobruchus maculatus (Fabricius, 1775), is the primary pest responsible for most of the damage to stored cowpeas. Recently, Trogoderma granarium (Everts, 1898) was found infesting cowpeas in large warehouses in Niger. This study evaluated hermetic storage bags to manage both common and emerging insect pests. Treatments included (i) the Purdue Improved Crop Storage (PICS) hermetic bag; (ii) a woven polypropylene (PP) bag with a polyethylene (PE) liner and Phostoxin; and (iii) a woven PP bag without Phostoxin (control). Naturally infested cowpea grains were obtained from the Office des Produits Vivriers du Niger (OPVN) warehouse in Maradi, Niger. Infestation levels were assessed using 12 samples of 500 g each, randomly collected from each treatment at the start and end of the trial. Major pests identified were C. maculatus, T. granarium, and Tribolium sp., with initial populations of 0.83, 0.44, and 0.83 adults per 500 g of cowpea, respectively. After six months of storage, pest densities in the control increased significantly: 232-fold for C. maculatus, 7.4-fold for T. granarium, and 2.7-fold for Tribolium sp.; resulting in a 38.5% weight loss. In contrast, both the Phostoxin and the PICS hermetic bags effectively suppressed pest populations, preventing weight loss. This study confirms the efficacy of hermetic storage, such as the PICS bag, in protecting cowpeas from both common and emerging pests. Full article

Postharvest grain losses often result from insect infestations. Hermetic storage creates airtight conditions that limit insect survival. However, oxygen depletion can be slow during hermetic storage, leading to a loss of grain quality and market value. Oxygen scavengers offer a solution to accelerate oxygen depletion. This study evaluated hand warmers as a cost-effective alternative to commercial oxygen scavengers. Experiments in sealed empty 4-gallon glass jars with 10-h hand warmers depleted oxygen faster and more cost-effectively than those with 2000 cc Oxy-Sorb oxygen absorbers. One hand warmer depleted similar amounts of oxygen as two Oxy-Sorb oxygen absorbers and reached the 5% threshold for pest suppression in 48 h. A follow-up study found that oxygen levels in empty 4-gallon jars dropped faster than in grain-filled 25-kg hermetic bags, with jars containing two or three hand warmers reaching the 5% threshold in the first 6 h. Temperature remained constant regardless of the number of hand warmers. At the same time, the relative humidity rose in empty jars but stayed stable in grain-filled hermetic bags, with no effect on grain quality. Hand warmers can potentially serve as cost-effective alternatives to commercial oxygen scavengers in hermetic storage. Full article

With the accelerating global transition to clean energy, underground hydrogen storage (UHS) has gained significant attention as a flexible and renewable energy storage technology. Ontario, Canada, as a pioneer in energy transition, offers substantial underground storage potential, with its geological conditions of salt, limestone, and sandstone providing diverse options for hydrogen storage. However, the hydrogen transport characteristics of different rock media significantly affect the feasibility and safety of energy storage projects, warranting in-depth research. This study simulates the hydrogen flow and transport characteristics in typical energy storage digital rock core models (salt rock, limestone, and sandstone) from Ontario using the improved quartet structure generation set (I-QSGS) and the lattice Boltzmann method (LBM). The study systematically investigates the distribution of flow velocity fields, directional characteristics, and permeability differences, covering the impact of hydraulic changes on storage capacity and the mesoscopic flow behavior of hydrogen in porous media. The results show that salt rock, due to its dense structure, has the lowest permeability and airtightness, with extremely low hydrogen transport velocity that is minimally affected by pressure differences. The microfracture structure of limestone provides uneven transport pathways, exhibiting moderate permeability and fracture-dominated transport characteristics. Sandstone, with its higher porosity and good connectivity, has a significantly higher transport rate compared to the other two media, showing local high-velocity preferential flow paths. Directional analysis reveals that salt rock and sandstone exhibit significant anisotropy, while limestone’s transport characteristics are more uniform. Based on these findings, salt rock, with its superior sealing ability, demonstrates the best hydrogen storage performance, while limestone and sandstone also exhibit potential for storage under specific conditions, though further optimization and validation are required. This study provides a theoretical basis for site selection and operational parameter optimization for underground hydrogen storage in Ontario and offers valuable insights for energy storage projects in similar geological settings globally. Full article

Hermetic grain storage bags are an airtight technology that protects stored grain from environmental factors, pests, and pathogens, with proven feasibility for smallholder farmer use. We examined the determinants and barriers to the use of these bags by smallholder farmers in Malawi and found that 83% of farmers were aware of hermetic bags for grain storage, but only 11–20% had ever used them, with half of the farmers who used the bags receiving them through donations. Furthermore, only 7.2% of farmers used the bags more than once. There was no association between their receipt of donated bags and their continued use and purchase of additional bags. There were, however, strong correlations between use of hermetic bags and the age of the head of household, distance to farmer groups’ meeting points, household size, and participation in a CIP-sponsored project. Focus group discussions identified key barriers to adopting hermetic bags, including local unavailability, perceived high cost, limited knowledge of the technology, low yields, and misconceptions about the utility of the bags. Thus, while donations play a central role in introducing hermetic bags, donations alone are insufficient in ensuring their long-term adoption. Addressing the identified barriers through improved availability, reduced costs, local manufacturing, and policy interventions such as microfinancing options and better distribution networks are essential to increasing the uptake of hermetic bags by smallholder farmers in Malawi and elsewhere in sub-Saharan Africa. Full article

In every era, climate variability and frequent food shortages have made it necessary to store harvested grains for more than one season. Underground grain storage has been used since ancient times throughout the world. Italy (Cerignola) and Malta (Valletta and Floriana) have preserved rare examples of more recent (from the 16th century onward) large concentrations of grain pits, capable of accumulating substantial reserves to cope with famine or siege. No longer in operation, they represent an important part of the cultural heritage of the agricultural economy. The purpose of this narrative review was, after a geographical framing of grain pits in the Eurasian and African macro-areas, to take the Italian and Maltese grain pits as historical case studies to draw attention to the reevaluation of underground grain storage in the context of climate change and food insecurity. Today, as in the past, grain reserves play a significant role in food security in developing countries and, due to climate change and geopolitical events that can cause disruptions in grain supplies, are also increasingly important for developed countries. A comparison of traditional and modern underground storage systems reveals the great flexibility of this technology, ranging from basic pits of different sizes to large underground granaries equipped with a support structure. The advantages of underground storage, such as environmental sustainability due to thermal insulation of the soil and airtight conditions that make high energy inputs for grain cooling and pesticide use unnecessary, are still useful today, perhaps more so than in the past. Prospects for development include technical solutions involving the application of innovative information technology-based monitoring systems and the use of modern materials to ensure the performance of waterproofing, seepage control, and static safety, all tools for further evolution of this ancient storage system. Full article

Millions of smallholder farmers use airtight (hermetic) storage to preserve stored commodities. However, relying on biological agents (i.e., insects) to deplete residual oxygen in airtight containers can occasionally extend the process, potentially resulting in grain damage or nutrient loss. Current oxygen scavengers used to remove this residual oxygen are unavailable and unsuitable on smallholder farms in developing countries. We evaluated the effectiveness of germinating seeds for oxygen depletion. Treatments comprised 10, 20, and 30 germinating cowpea seeds in 2 L jars filled with infested cowpea grains. Insect mortality and grain quality were assessed after 24, 48, 72, 96, and 120 h. Progeny development was monitored for 49 days post-treatment. The results showed that all germinating seeds depleted oxygen to 5% or below within 48 h. Complete adult mortality was achieved after 72 h for both 20 and 30 germinating seeds and 120 h for 10 germinating seeds. As germinating seeds increased, egg counts decreased. No adults emerged post-treatment after insects were exposed for 96 and 120 h to hypoxia from 30 and 20 germinating seeds, respectively. However, 120 h insect exposure to hypoxia from 10 germinating seeds had negligible progeny development. Moisture content increased slightly in grains exposed to 30 germinating seeds. Germinating seeds are as effective as controlled atmospheres in accelerating insect deaths, but further research is needed for field application and their effects on stored product quality. Full article

Achieving the global electricity demand and meeting the United Nations sustainable development target on reliable and sustainable energy supply by 2050 are crucial. Portable energy storage (PES) units, powered by solid-state battery cells, can offer a sustainable and cost-effective solution for regions with limited power-grid access. However, operating in high-dust and high-temperature environments presents challenges that require effective thermal management solutions. This paper is a comprehensive review of thermal management systems for PES units, with a specific focus on addressing the challenge of overheating in airtight designs. The review of various active and passive cooling systems is conducted through extensive study of the relevant literature, which is significant in providing insights into the operation, performance parameters, and design options for different cooling system technologies. The findings from this review show heat pipe (HP) technologies as key cooling-system solutions for airtight PES units. Specifically, loop and oscillating HPs, as well as the vapour chamber, offer desirable features such as compactness, low cost, and high thermal conductivity that make them superior to other alternatives for the cooling systems in PES. The insights and knowledge generated via this review will help facilitate the design and development of innovative, efficient, and reliable PES units, thereby contributing to the advancement of off-grid renewable energy applications and enabling sustainable power solutions worldwide. Furthermore, an appropriate design of PES units can help in reducing capital and maintenance costs. Full article

Hermetic storage methods are effective at protecting grain against insect pests. Biotic and abiotic factors influence oxygen depletion during hermetic storage. We investigated the dual effects of temperature and initial pest infestation level on oxygen depletion during airtight storage. Glass jars filled with cowpea grain were infested (25 or 50 adult cowpea bruchids), then hermetically sealed and stored at 20, 30, or 40 °C for 30 days. Oxygen depletion, relative humidity, and temperature were monitored. Germination, grain moisture content, grain damage and weight loss, and adult emergence were assessed. Oxygen depletion varied by temperature and insect infestation level. However, 30 °C was the optimum temperature for oxygen depletion (reaching 5% or less in 10 days) regardless of insect infestation level. No changes were observed in germination and grain moisture content, minimal grain damage, or weight loss (<1%). Only at 20 °C were adult insects able to survive after 30 days and emerged 45 days post-treatment under normoxia. Therefore, hermetic storage containers should remain closed for more than 30 days to minimize re-infestation of grain in areas where average ambient temperatures rarely exceed 23 °C. Further research is needed to assess the effect of low temperatures on oxygen depletion and insect survival in hermetic storage beyond 30 days. Full article

In this study, the feasibility of storing Marmande tomatoes (Solanum lycopersicum, cv Rojito) under hypobaric conditions was evaluated. The fruits were sorted into four lots of 72 fruits each. One lot was considered as a control, and the fruits were kept in the open box, while the fruits of the rest of the three remaining lots were enclosed in airtight containers and subjected to 101, 75 and 50 Kpa, respectively. Control fruits and airtight containers were kept at room temperature, and every three days from the beginning of the experiment the following main quality parameters were analysed: ethylene production rate, firmness, colour, total solids content, ascorbic acid, total phenolics and pigments, as well as a sensory analysis carried out by panellists. The results show that sub-atmospheric storage led a reduction in ethylene production, which was associated with a delay in ripening. The differences in the evolution of pigments were very significant, while a large degradation of chlorophylls was observed in the control fruits and in those kept at 101 kPa, in the fruits kept at 75 kPa and 50 kPa the degradation was much slower. In relation to carotenoid pigments, it was observed that sub-atmospheric treatments delayed their appearance compared to control and 101 kPa fruits. In relation to other quality parameters, it was found that control fruit and fruit held at 101 kPa softened more rapidly than fruit under sub-atmospheric conditions, whose loss of firmness was more gradual with differences found only at 9 and 12 days of storage with respect to fruit firmness at harvest. The appearance of these fruits was evaluated with the same score as at the time of harvesting, during 9 of the 12 days of the experiment, then a positive effect of sub-atmospheric treatments was also found in the sensory analysis. The results suggest that sub-atmospheric storage could be a suitable method of increasing the shelf-life of fruits. Full article

Apples are stored at temperatures close to 0 °C and high relative humidity (up to 95%) under controlled atmosphere conditions. Under these conditions, the cyclic operation of the refrigeration machine and the associated temperature fluctuations can lead to localized undershoots of the dew point on fruit surfaces. The primary question for the present study was to prove that such condensation processes can be measured under practical conditions during apple storage. Using the example of a measuring point in the upper apple layer of a large bin in the supply air area, this evidence was provided. Using two independent measuring methods, a wetness sensor attached to the apple surface and determination of climatic conditions near the fruit, the phases of condensation, namely active condensation and evaporation, were measured over three weeks as a function of the operating time of the cooling system components (refrigeration machine, fans, defrosting regime). The system for measurement and continuous data acquisition in the case of an airtight CA-storage room is presented and the influence of the operation of the cooling system components in relation to condensation phenomena was evaluated. Depending on the set point specifications for ventilation and defrost control, condensed water was present on the apple surface between 33.4% and 100% of the duration of the varying cooling/re-warming cycles. Full article

Using low-quality maize, resulting from insect pests and fungal attack, for formulating feed reduces chicken performance. This study evaluated the effectiveness of hermetic storage bags to keep insect pest and mycotoxin levels in check in yellow maize. The study was conducted in storehouses at three poultry farms in Dormaa Ahenkro, Bono Region, Ghana. The experiment was set up in a Randomized Complete Block Design with ZeroFly® Hermetic (ZFH), Purdue Improved Crop Storage (PICS), and Polypropylene (PP) bags as treatments. In each treatment, twelve 50 kg samples of untreated maize were each put in 100 kg capacity bags. Two bags in each treatment were destructively sampled monthly for 6 months. The number of insects was significantly higher in the PP bag (161.00 ± 4.25), compared to the PICS and ZFH bags: 7.00 ± 0.29 and 4.50 ± 0.76, respectively. The PICS and ZFH bags had less insect damage and lower weight loss than the PP bags. Aflatoxin and fumonisin levels were below the recommended safe thresholds of 15 ppb and 4 ppm, respectively, in all the bags. With the exception of ash, proximate analyses were higher for all variables in the PICS and ZFH bags. The study showed that PICS and ZFH bags conserved maize quality better than the PP bag. Full article

Background: Bacteria are readily nourished in airtight environments with high humidity, such as storage cabinets, clothing closets, and corners, where ventilation is normally low and humidity is high. Objectives: We characterized the role of humidity and ventilation in bacterial growth and genus distribution at different temperatures (26 °C and 34 °C). Methods: Fresh pork, which was used as the substrate for bacterial culture, was placed in storage cabinets. Bacterial growth and genera distribution on the surface of pork placed in a storage cabinet under different temperatures (26 °C and 34 °C); relative humidity levels (RH: 50%, 70%, 90%); and ventilation conditions (no ventilation and low, medium, and high levels of ventilation) were assessed by rDNA sequencing. Results: Increased ventilation and reduced humidity significantly decreased bacterial growth at 26 °C and 34 °C. The contribution of increased ventilation to the reduction in bacterial growth exceeded that of decreased humidity. Ventilation had the greatest effect on reducing bacterial growth compared to the unventilated conditions at 70% RH. At 34 °C, medium and high levels of ventilation were required to reduce bacterial growth. High temperatures greatly increased bacterial growth, but ventilation could reduce the degree of this increase. Full article

Hermetic bags are effective at curbing grain losses due to insect pests, but their use remains low due to unavailability among smallholder farmers. This study used primary data from actors within the Purdue Improved Crop Storage (PICS) supply chain network, mostly the private sector, in Ethiopia, Tanzania, and Uganda, to understand the challenges and opportunities in improving the availability of hermetic bags in rural areas. It finds that supply-side distribution approaches played a critical role in improving PICS bag availability. Some of the supply-side constraints included poor inventory management, pricing, and limited access to capital. Inventory management can be improved through better forecasting using sales records and prediction of farmers’ harvests. Improved access to credit during peak season can improve the timely supply and reduce stockouts. Marketing inefficiency appears to be fueled by a high-profit margin at the distributor level. Using all available distribution channels in addition to ag-input dealers will enhance the availability of the bags in rural communities. Full article