Low-temperature Storage Systems Research Articles

Scalable façade-integrated PVT-systems for upward extensions in the urban context

This article presents a building concept, realised in a timber demonstration house. It is characterized by vertical, façade-integrated PVT collectors and a newly developed active layer as low-temperature storage system. We developed a scalable and transferable energy system design. Especially for multi-storey additions, where the roof area does not grow with the floor space, the concept increases - very much needed - power and energy density in urban areas. The novelty of the presented concept is the sole reliance on vertically mounted PVT-Panels as a heat source, without any seasonal energy storage (e.g., ice storage or geothermal) in combination with the active layer storage below the underfloor heating. Together they allow scaling of energy storage and solar gains with the usable space in the urban context of adding floors to existing buildings.

The effect of temperature and humidity of storage on maize seed quality

Orthodox seed storage involves storage conditions under low temperature and humidity. Various factors affecting seed storage include: the initial moisture content of seeds, the use of packaging or an airtight packaging and low temperature storage system. Seed storage using different temperatures and humidity will affect the quality of the seeds during the storage period. Storage using room temperature is very crucial particularly on seeds that have deteriorated during handling process prior to storage. In addition, the rate of seed quality decline is relatively drastic. The use of low temperature and air humidity can keep the viability and vigor of seeds even though it has deteriorated. Thus, the quality of seeds during the storage period is strongly influenced by the quality of the initial seed (before storage), seed moisture content, temperature and humidity during the storage period.

Horticultural, systems-engineering and economic evaluations of short-term plant storage techniques as a labor management tool for vegetable grafting nurseries.

This transdisciplinary study has a three-fold systems approach in evaluating a horticultural technology: 1) horticultural evaluations, 2) economic and resource analyses, and 3) systems engineering analyses, using low temperature storage as an example technology. Vegetable grafting is a technique to produce value-added seedlings but requires labor intensive nursery operations. Low temperature storage of seedlings for a short period of time can reduce peak production, but has not been evaluated at the extent demonstrated in this paper. Seedlings of 22 genotypes of Cucurbitaceae (cucurbit family) and Solanaceae (nightshade family) were evaluated for storability under selected temperatures and photosynthetic photon flux. Storability of Cucurbitaceous seedlings varied between 2 to 4 weeks at 12°C and 13 μmol m-2 s-1. Solanaceous seedlings were generally storable for 4 weeks at 12°C and 13 μmol m-2 s-1, but tomato seedlings could be stored for 4 weeks at 10°C and 5 μmol m-2 s-1. Capital and weekly operational costs of a low temperature storage system with a design that meets environmental requirements were estimated as $671 to $708 per m2 footprint and $0.79 to $2.21 per m2 footprint per week, respectively. Electricity costs per plant was less than 0.1 cents for 2 to 4 weeks of storage. Using a schedule-optimization heuristic and a logistics simulator previously developed for grafting nursery operations, six production scenarios consisting of two crops (tomato or watermelon) and three production peak patterns were examined to evaluate the impact of including low temperature storage. While the overall average costs of grafting labor were not significantly different, maximum labor demand and grafting labor cost during the peak production week were reduced by 31% to 50% and 14% to 30% by using storage, respectively. Therefore, low temperature storage can be an effective means to address the issue of labor management in grafting nurseries.

히트펌프를 이용한 농산물 건조 및 저온저장 시스템 (II) - 사과의 저온저장 성능 -

Heat pump systems are recognized to be heating and cooing systems. In this study, to check the practical application possibility of heat pump systems as low temperature storage systems and get basic data, apples of a long term storage items were stored and performance of low temperature storage and quality changes of apples were evaluated. Cooling coefficient of performance of the system was from 1.1 to 1.3. Although ambient air temperature varied widely from <TEX>$-13^{\circ}C$</TEX> to <TEX>$29.6^{\circ}C$</TEX> during low temperature storage period from January to June, the average temperature of low temperature storage chamber was <TEX>$1.1^{\circ}C$</TEX> at setting temperature of <TEX>$1.5^{\circ}C$</TEX>. Sucrose of apples stored by the heat pump decreased from initial sucrose of 15.4% (Brix number) to final sucrose of 14.3%. Weight loss ratio of apples was 9.7% and internal and external view of apples after low temperature storage were very satisfactory with the naked eye.

히트펌프를 이용한 농산물 건조 및 저온저장 시스템 (I) - 건조 성능 -

Korean farmers have purchased agricultural dryer and low temperature storage system apart. In this study, the system was designed and constructed to investigate the practical application possibility of the air to air heat pump as drying and low temperature storage system for agricultural products with providing basic data. The performance and drying characteristics of the system evaluated by drying red pepper. The value of coefficient of performance of the system for heating was from 1.8 to 2.2 when ambient air temperature varied from 13<TEX>$^{\circ}C$</TEX> to 23<TEX>$^{\circ}C$</TEX>. For operating the heat pump as dryer for drying red pepper by setting three drying air temperature of 50, 55 and 60<TEX>$^{\circ}C$</TEX>, specific moisture extraction rates meaning amount of energy consumption for removing moisture of 1kg from red pepper were 1.095, 1.017 and 1.094 kg<TEX>$_{water}$</TEX>/kWh, respectively. The drying period up to moisture ratio of 0.02 were 31, 26 and 21 hour, respectively. The lightness, redness, yellowness and chroma differences of red pepper dried by the heat pump dryer were lowered than those of red pepper dried by conventional heated air dryer except for yellowness difference at drying air temperature of 60<TEX>$^{\circ}C$</TEX>.