10 results on '"Furbo, Simon"'
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2. Testing of PCM Heat Storage Modules with Solar Collectors as Heat Source
- Author
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Englmair, Gerald, Dannemand, Mark, Johansen, Jakob Berg, Kong, Weiqiang, Dragsted, Janne, Furbo, Simon, and Fan, Jianhua
- Subjects
Compact Thermal Energy Storage ,PCM ,Sodium Acetate Trihydrate ,Seasonal Heat Storage ,Phase Change Material ,Stable Supercooling - Abstract
A latent heat storage based on the phase change material Sodium Acetate Trihydrate (SAT) has been tested as part of a demonstration system. The full heat storage consisted of 4 individual modules each containing about 200 kg of sodium acetate trihydrate with different additives. The aim was to actively utilize the ability of the material to supercool to obtain long storage periods. The modules were charged with solar heat supplied by 22.4 m2 evacuated tubular collectors. The investigation showed that it was possible to fully charge one module within a period of 270 minutes with clear skies. In long periods with high level of irradiance several modules were charged in parallel due to the limited heat exchange capacity of the integrated heat exchanger of the modules. After the modules were heated to more than 80° C they were set to passively cool down. Modules reached 30 °C in a period of parallel cool down without the sodium acetate trihydrate solidified in 3 of the 4 modules. Further tests showed that stable supercooling at ambient temperature is possible.
- Published
- 2016
3. Laboratory Test of a Cylindrical Heat Storage Module with Water and Sodium Acetate Trihydrate
- Author
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Dannemand, Mark, Kong, Weiqiang, Johansen, Jakob Berg, and Furbo, Simon
- Subjects
Heat storage ,Sodium acetate trihydrate ,Supercooling ,Phase change material - Abstract
Cylindrical heat storage modules with internal heat exchangers have been tested in a laboratory. The modules were filled with water and sodium acetate trihydrate with additives. The testing focused on the heat content of the storage material and the heat exchange capacity rate during charge of the module. For the tests with the phase change materials, the focus was furthermore on the stability of supercooling and cycling stability. Testing the module with sodium acetate trihydrate and 6.4% extra water showed that phase separation increased and the heat released after solidification of supercooled phase change material was reduced over 17 test cycles. The heat released after solidification of the supercooled sodium acetate trihydrate with thickening agent and graphite was stable over the test cycles. Stable supercooling was obtained in 7 out of 17 test cycles with the module with sodium acetate trihydrate with extra water and in 6 out of 35 test cycles for the module with thickening agent.
- Published
- 2016
4. Thermal conductivity enhancement of sodium acetate trihydrate by adding graphite powder and the effect on stability of supercooling
- Author
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Johansen, Jakob Berg, Dannemand, Mark, Kong, Weiqiang, Fan, Jianhua, Dragsted, Janne, and Furbo, Simon
- Subjects
Thermal conductivity ,CMC ,PCM ,SAT ,Graphite ,Sodium acetate trihydrate ,X-gum ,Seasonal heat storage ,Carbon ,Supercooling ,Carboxymethyl cellulose ,Phase change material ,Xanthan gum - Abstract
Sodium acetate trihydrate and graphite powder mixtures have been evaluated to investigate the influence of the graphite powder on the stability of supercooling. A sodium acetate and water mixture mixed with graphite powder was successfully supercooled at ambient indoor temperatures for five months. The graphite powder was stabilized using carboxymetyl cellulose and successfully tested in heating and supercooling cycles with no loss of performance. Thermal conductivity enhancing properties of graphite powder was shown in samples.Since the experiments were conducted in small scale, at 200 g per sample, large scale experiments are required to validate graphite as a thermo conductivity enhancing agent, suitable for use in seasonal heat storage applicationsutilizing SAT.
- Published
- 2015
5. Design and functionality of a segmented heat-storage prototype utilizing stable supercooling of sodium acetate trihydrate in a solar heating system.
- Author
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Englmair, Gerald, Moser, Christoph, Furbo, Simon, Dannemand, Mark, and Fan, Jianhua
- Subjects
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SOLAR heating , *SOLAR collectors , *HEAT storage , *SODIUM acetate , *SUPERCOOLING , *PHASE change materials - Abstract
A solar heating system with 22.4 m 2 of solar collectors, a heat storage prototype consisting of four 200 kg phase-change material (PCM) storage units, and a 735 L water tank was designed to improve solar heat supply in single-family houses. The PCM storage utilized stable supercooling of sodium acetate trihydrate composites to conserve the latent heat of fusion for long-term heat storage. A control strategy directed heat from a solar collector array to either the PCM storage or a water buffer storage. Several PCM units had to be charged in parallel when the solar collector output peaked at 16 kW. A single unit was charged with 27.4 kWh of heat within four hours on a sunny day, and the PCM temperature increased from 20 °C to 80 °C. The sensible heat from a single PCM unit was transferred to the water tank starting with about 32 kW of thermal power after it had fully melted at 80 °C. A mechanical seed crystal injection device was used to initialize the crystallisation of the sodium acetate trihydrate after it had supercooled to room temperature. The unit discharge during solidification peaked at 8 kW. Reliable supercooling was achieved in three of the four units. About 80% of latent heat of fusion was transferred from PCM units after solidification of supercooled sodium acetate trihydrate to the water tank within 5 h. Functionality tests with practical operation conditions on the novel, modular heat-storage configuration showed its applicability for domestic hot water supply and space heating. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
6. Solidification behavior and thermal conductivity of bulk sodium acetate trihydrate composites with thickening agents and graphite.
- Author
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Dannemand, Mark, Johansen, Jakob Berg, and Furbo, Simon
- Subjects
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SOLIDIFICATION , *THERMAL conductivity , *SODIUM acetate , *COMPOSITE materials , *GRAPHITE , *THICKENING agents - Abstract
Sodium acetate trihydrate is a promising phase change material for long term storage of solar thermal energy if supercooling is actively utilized. Well performing thermal energy storages need to be able to charge and discharge energy at a high rate. The relatively low thermal conductivity of the phase change material limits the heat exchange capacity rate to and from the storage. Another factor that limits the heat transfer is the contraction and expansion of the salt hydrate during the phase change. This density change causes formation of cavities inside the solid storage material. Investigations of the solidification behavior, the formation of cavities and thermal conductivity of composites based on sodium acetate trihydrate crystalizing with or without supercooling are presented in this paper. The thermal conductivity was measured with an ISOMET hot disc surface measurement probe. Samples that crystalized without supercooling tended to form solid crystals near the heat transfer surface and cavities away from the heat transfer surface. The measured thermal conductivity was up to 0.7 W/m K in solid sodium acetate trihydrate. Samples that crystalized from supercooled state formed fewer large cavities but had a lower thermal conductivity. A composite with sodium acetate trihydrate, thickening agent and 5% graphite flakes had a thermal conductivity of up to 1.1 W/m K. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
7. A solar combi-system utilizing stable supercooling of sodium acetate trihydrate for heat storage: Numerical performance investigation.
- Author
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Englmair, Gerald, Moser, Christoph, Schranzhofer, Hermann, Fan, Jianhua, and Furbo, Simon
- Subjects
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HEAT storage devices , *HEAT storage , *SODIUM acetate , *SOLAR collectors , *RENEWABLE energy sources , *ENERGY consumption of buildings - Abstract
• On-demand crystallization of sodium acetate trihydrate for heat storage. • A numerical model was validated with data from system demonstration. • Sensitivity analysis of solar collector area and heat storage volume. • Annual solar fraction of 71% with 0.6 m3 water and 1 m3 of PCM for heat storage. • 1000 kWh of heat supplied by PCM units with 5.5 annual heat storage cycles. To reduce the energy consumption of buildings significantly, a novel solar combi-system with short and long-term heat storage has been developed. A system prototype with 22.4 m2 (aperture) evacuated tubular collectors, a 735 L water tank and 4 phase change material (PCM) units each containing 150 L sodium acetate trihydrate composite has been built. Experimental investigation has shown advantages of utilization of stable supercooling of sodium acetate trihydrate in spring and autumn. In this paper, a newly developed numerical model was used to investigate the performance potential of the system with combined utilization of the water tank and the PCM units, including on-demand crystallization of supercooled sodium acetate trihydrate composites. PCM units, the water tank and the collector circuit models were validated with measurement data from system demonstration. Space heating and hot water demand patterns of a Danish single-family Passive House with a yearly heat demand of 3723 kWh were applied. Results showed that a 56% annual solar fraction of heat supply was achieved with the prototype specifications. A 69% solar fraction could be achieved with an optimized scenario including a 15% increased hot water demand. Sensitivity analysis of component sizing showed that PCM units of 200 L can be more efficiently used with a 0.6 m3 water tank. Optimal solar collector array tilt was 70°. Aperture areas between 12.8 and 22.4 m2 were found adequate for frequent utilization of a PCM volume up to 1 m3. Thus, the PCM heat storage capacity could be utilized at least 5.5 times a year. With a 22.4 m2 collector area and 5 PCM units of 200 L each, a solar fraction of 71% was calculated for the annual heat supply. Assuming full charge of a 0.6 m3 water tank and 2.8 m3 of sodium acetate trihydrate composite by electricity at the beginning of the year, the system could run 18 days without need for auxiliary heating. Thus, in periods without solar collector power available, generation maxima of wind power could be utilized. In conclusion, building heat demand could be covered close to 100% by renewable energy resources. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
8. Experimental investigations on heat content of supercooled sodium acetate trihydrate by a simple heat loss method.
- Author
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Kong, Weiqiang, Dannemand, Mark, Johansen, Jakob Berg, Fan, Jianhua, Dragsted, Janne, Englmair, Gerald, and Furbo, Simon
- Subjects
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SUPERCOOLING , *SODIUM acetate , *HEAT losses , *ENTHALPY , *PHASE separation , *XANTHAN gum - Abstract
Sodium acetate trihydrate is a phase change material that can be used for long term heat storage in solar heating systems because of its relatively high heat of fusion, a melting temperature of 58 °C and its ability to supercool stable. In practical applications sodium acetate trihydrate tend to suffer from phase separation which is the phenomenon where anhydrous salt settles to the bottom over time. This happens especially in supercooled state. The heat released from the crystallization of supercooled sodium acetate trihydrate with phase separation will be lower than the heat released from sodium acetate trihydrate without phase separation. Possible ways of avoiding or reducing the problem of phase separation were investigated. A wide variety of composites of sodium acetate trihydrate with additives including extra water, thickening agents, solid and liquid polymers have been experimentally investigated by a simple heat loss method. The aim was to find compositions of maximum heat released from the crystallization of supercooled sodium acetate trihydrate samples at ambient temperature. It was found that samples of sodium acetate trihydrate with 0.5–2% (wt.%) Carboxy-Methyl Cellulose, 0.3–0.5 % (wt.%) Xanthan Gum or 1–2% (wt.%) of some solid or liquid polymers as additives had significantly higher heat contents compared to samples of sodium acetate trihydrate suffering from phase separation. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
9. Experimental investigations on cylindrical latent heat storage units with sodium acetate trihydrate composites utilizing supercooling.
- Author
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Dannemand, Mark, Johansen, Jakob Berg, Kong, Weiqiang, and Furbo, Simon
- Subjects
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LATENT heat , *HEAT storage , *SODIUM acetate , *SUPERCOOLING , *STAINLESS steel , *HEAT exchangers , *SOLIDIFICATION - Abstract
Latent heat storage units utilizing stable supercooling of sodium acetate trihydrate (SAT) composites were tested in a laboratory. The stainless steel units were 1.5 m high cylinders with internal heat exchangers of tubes with fins. One unit was tested with 116 kg SAT with 6% extra water. Another unit was tested with 116.3 kg SAT with 0.5% Xanthan rubber as a thickening agent and 4.4% graphite powder. The heat exchange capacity rate during charge was significantly lower for the unit with SAT and Xanthan rubber compared to the unit with SAT and extra water. This was due to less convection in the thickened phase change material after melting. The heat content in the fully charged state and the heat released after solidification of the supercooled SAT mixtures at ambient temperature was higher for the unit with the thickened SAT mixture. The heat discharged after solidification of the supercooled SAT with extra water decreased over repeating charge and discharge cycles while the heat discharged from the SAT with Xanthan rubber remained stable. In both units, the solidification started spontaneously in the majority of the test cycles. This was due to the design of the unit or the method for handling the expansion and contraction of the SAT during charge and discharge. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
10. Experimental investigations on prototype heat storage units utilizing stable supercooling of sodium acetate trihydrate mixtures.
- Author
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Dannemand, Mark, Dragsted, Janne, Fan, Jianhua, Johansen, Jakob Berg, Kong, Weiqiang, and Furbo, Simon
- Subjects
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HEAT storage , *PROTOTYPES , *SUPERCOOLING , *SODIUM acetate , *PHASE change materials , *CARBOXYMETHYLCELLULOSE - Abstract
Laboratory tests of two heat storage units based on the principle of stable supercooling of sodium acetate trihydrate (SAT) mixtures were carried out. One unit was filled with 199.5 kg of SAT with 9% extra water to avoid phase separation of the incongruently melting salt hydrate. The other unit was filled with 220 kg SAT mixture thickened with 1% carboxymethyl cellulose. The heat exchange capacity rate during the charging of the unit with the extra water was significantly higher than for the unit with the thickening agent due to the different levels of convection. The SAT mixtures in the units were stable and supercooled at indoor ambient temperatures for up to two months, after which the units were discharged. The energy discharged after solidification of the supercooled SAT and water mixture was 194 kJ/kg in the first test cycle, dropping to 179 kJ/kg after 20 test cycles. The energy discharged from the unit with SAT and the thickening agent after solidification was stable at 205 kJ/kg over 6 test cycles. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
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