| 1. |
- Chiu, Justin NingWei, et al.
(författare)
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A Review of Thermal Energy Storage Systems with Salt Hydrate Phase Change Materials for Comfort Cooling
- 2009
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Ingår i: 11th International Conference on Thermal Energy Storage, June 14-17 , 2009, Stockholm, Sweden..
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Konferensbidrag (refereegranskat)abstract
- This paper presents a review of cold thermal energy storage technologies. Latent heat thermal energy storage (LHTES) with phase change materials (PCMs) deserves attention as they provide high energy density and small temperature change interval upon melting/solidifying. Salt hydrates are especially interesting since they demonstrate high latent heat of fusion, high thermal conductivity, low flammability, and facilitate the use in buildings as compared to organic PCMs. A review of system performance obtained from experimental work, theoretical analyses and real case studies has however shown some material shortcomings. To reach cost effectiveness, future work in the field of LHTES with salt hydrates lies in finding suitable methods for limiting incongruent melting and subcooling without compromising the storage density. Also, system integration of LHTES in cold applications can be further developed in terms of innovative design for high power and storage capacity, load optimized sizing, controls, and elimination of PCM encapsulation.
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| 2. |
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| 3. |
- Chiu, Justin NingWei, et al.
(författare)
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System Integration of Latent Heat Thermal Energy Storage Systems for Comfort Cooling Integrated in district cooling network
- 2009
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Ingår i: 11th International Conference on Thermal Energy Storage, EFFSTOCK 2009, Stockholm, Sweden, June 14-17, 2009..
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Konferensbidrag (refereegranskat)abstract
- Latent heat thermal energy storage for comfort cooling with phase change materials (PCMs) has increasingly gained attention. For effective system integration, an optimized strategy for load shifting to cut down peak hour energy use is needed. With the focus on overall system performance, this paper addresses matching of a cold storage capacity and power to a demand while assessing the cost effectiveness of the PCM technology. A simulation model based on one office building cooling load in Stockholm Sweden was used. Storage capacity, power output and PCM cost were shown to be the predominant factors in a system design. It has been found that load leveling can cost effectively reduce the peak load by 5% to 9% in a fixed tariff system. However, with 50% reduction in today’s PCM price combined with removal of district cooling return temperature penalty, the peak power reduction rate may be increased to 30%.
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| 4. |
- Iwata, S., et al.
(författare)
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Therapeutic hypothermia can be induced and maintained using either commercial water bottles or a "phase changing material'' mattress in a newborn piglet model
- 2009
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Ingår i: Archives of Disease in Childhood. - : BMJ. - 0003-9888 .- 1468-2044. ; 94:5, s. 387-391
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Tidskriftsartikel (refereegranskat)abstract
- Background: Therapeutic hypothermia, a safe and effective treatment for neonatal encephalopathy in an intensive care setting, is not available in low-resource settings. Aims/Methods: To assess two low-tech, low-cost cooling devices for use in low-resource settings: (i) commercially available water bottles filled with tepid water (25 degrees C); (ii) a mattress made of phase changing material (PCM) with a melting point of 32 degrees C (PCM works as a heat buffer at this temperature). Eleven anaesthetised newborn piglets were studied following transient hypoxia-ischaemia. The cooling device was applied 2-26 h after hypoxia-ischaemia with a target rectal temperature (T-rectal) of 33-34 degrees C. T-rectal undershoot was adjusted using cotton blankets; the cooling device was renewed when T-rectal rose above 35 degrees C. T-rectal data during cooling were dichotomised (within or without target) to assess: (a) the total period within the target T-rectal range; (b) the stability and fluctuation of T-rectal during cooling. Results: Therapeutic hypothermia was achieved with both water bottles (n=5) and the PCM mattress (n=6). The mean (SD) time to reach target T-rectal was 1.8 (0.5) h with water bottles and 1.9 (0.3) h with PCM. PCM cooling led to a longer period within the target T-rectal range (p<0.01) and more stable cooling (p<0.05). Water bottle cooling required device renewal (in four out of five piglets). Conclusion: Simple, low-tech cooling devices can induce and maintain therapeutic hypothermia effectively in a porcine model of neonatal encephalopathy, although frequent fine tuning by adjusting the number of blankets insulating the piglet was required to maintain a stable temperature. PCM may induce more stable cooling compared with water bottles.
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| 5. |
- Martin, Viktoria, et al.
(författare)
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Compact Heat Storage for Solar Heating Systems
- 2009
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Ingår i: Journal of solar energy engineering. - : ASME International. - 0199-6231 .- 1528-8986. ; 131:4
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Tidskriftsartikel (refereegranskat)abstract
- Energy and cost efficient solar hot water systems require some sort of integrated storage, with high energy density and high power capacity for charging and discharging being desirable properties of the storage. This paper presents the results and conclusions from the design, and experimental performance evaluation of high capacity thermal energy storage using so-called phase change materials (PCMs) as the storage media. A 140 l 15 kW h storage prototype was designed, built, and experimentally evaluated. The storage tank was directly filled with the PCM having its phase change temperature at 58 degrees C. A tube heat exchanger for charging and discharging with water was submerged in the PCM. Results from the experimental evaluation showed that hot water can be provided with a temperature of 40 degrees C for more than 2 h at an average power of 3 kW. The experimental results also show that it is possible to charge the 140 l storage with close to the theoretically calculated value of 15 kW h. Hence, this is a PCM storage solution with a storage capacity of over 100 kW h/m(3), and an average power capacity during discharging of over 20 kW/m(3). However, it is desirable to increase the heat transfer rate within the prototype. A predesign of using a finned-tube coil instead of an unfinned coil show that by using finned tube, the power capacity for discharging can be at least doubled, if not tripled.
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| 6. |
- Wang, Weilong, 1978-
(författare)
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Preparation and performance of energy storage materials and application for recovery of industrial waste heat
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Due to the rapid increase of energy consumption and the environmental concerns on climate change caused by the fossil fuel combustion, it becomes a big issue on how to use alternative renewable energy resources to replace fossil fuel and to improve energy utilization efficiency. In Sweden, there are plenty of detached buildings without connection with district heating (DH) network, which use oil to supply the hot water for space heating and tap water. One way is to extend the district heating network for supply the heat for the detached houses. However, this will need increased costs for the district heat pipeline which might not be economically variable for the area with less density of population. Another alternative is to apply so called mobilized thermal energy storage (M-TES) to transport heat from, e.g. industrial waste heat, to the end-users of the detached houses. This will enable to keep the detached houses in the same state as a distributed heat system while replacing the fossil fuels for heating demand. The mechanism of energy storage and release is on the basis of transition of phase change materials (PCMs), which can solve the problem in time and spatial mismatch between the energy supply and consumption. Polyethylene glycol (PEG) as a type of organic PCMs is studied in this licentiate thesis due to its large heat capacity and multi-melting temperatures. As a representative of organic PCMs, PEG also has some disadvantages, like encapsulation needed for preventing leakage and low thermal conductivity. To resolve those, a type of so-called form-stable energy storage materials is prepared by blending PEG with silica gel. Modified aluminium nitride (AlN) powder is then added to enhance the thermal conductivity of materials. Meanwhile, another form-stable energy storage material is prepared by mixing the melted PEG into expanded graphite (EG). The results show that two types of composite materials can keep the form stable during the transition, and AlN powder can enhance the thermal conductivities of energy storage materials. Based on the knowledge of energy storage technology, M-TES system is designed and combined with the existing heat system in Eskilstuna. The feasibility study of M-TES is carried out through the data collected from CHP plant and end-user in this licentiate thesis. The results show that there are economic and environmental benefits by using M-TES system to supply heat for detached houses.
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