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Phase Changing Material in Solar Thermal Energy Storage

Phase Changing Material in Solar Thermal Energy Storage. Tiffany Wu Energy Technology and Policy University of Texas at Austin. ( www.powerfromthesun.net/chapter1/Chapter1.htm ). Contents. Introduction Benefits and Drawbacks of PCM PCM Options Encapsulation

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Phase Changing Material in Solar Thermal Energy Storage

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  1. Phase Changing Material in Solar Thermal Energy Storage Tiffany Wu Energy Technology and Policy University of Texas at Austin (www.powerfromthesun.net/chapter1/Chapter1.htm )

  2. Contents • Introduction • Benefits and Drawbacks of PCM • PCM Options • Encapsulation • Increasing Thermal Conductivity • Conclusion

  3. Most systems have a disconnect between supply and demand Intermittent solar energy supply can be maximized with a heat storage system Thermal energy can be stored both as sensible and latent heat Continued efforts to find a phase changing material is currently underway Introduction (Fath, 1998; Kousksou, 2007; Pasupathy, 2008)

  4. Benefits and Drawbacks of PCM Benefits: • Higher storage density than sensible heat • Smaller volume • Smaller temperature change between storing and releasing energy Drawbacks: • High cost • Corrosiveness • Density change • Low thermal conductivity • Phase separation • Incongruent melting • Supercooling (Pasupathy, 2008)

  5. PCM Options (Pasupathy, 2008)

  6. PCM Options Inorganic Glauber’s salt, calcium chloride hexahydrate, sodium thiosulfate penthydrate, sodium carbonate decahydrate Benefits: • Low cost and readily available • High volumetric storage density • Relatively high thermal conductivity Drawbacks: • Corrosive • Decomposition • Incongruent melting • Supercooling (Pasupathy, 2008; Farid, 2004)

  7. PCM Options Organic Paraffin waxes and fatty acids Benefits: • Melts congruently • Chemically and physically stable • High heat of fusion Drawbacks: • More expensive and flammable • Low thermal conductivity in solid state • Lower heat storage capacity per volume (Pasupathy, 2008; Farid, 2004)

  8. PCM Options

  9. Encapsulation • Prevents reactivity towards environment • Compatible with stainless steel, polypropylene, and polyolefin • Controls volume as phases change • Prevents large drops in heat transfer rates (Farid, 2004)

  10. (Kenisarin, 2007)

  11. Increasing Thermal Conductivity • Metallic fillers • Metal matrix structures • Finned tubes Aluminum filling with VSP 25 and VSP 50 Finned Tubes PCM-Graphite Matrix (Farid, 2004; Kenisarin, 2007)

  12. Total solidification time of PCM is shorter with fins and lessing rings, but the total quantity of stored heat is slightly smaller The VSP25 filling provided the highest thermal conductivity of 1W/(mK), which is about six times that of pure paraffin (Kenisarin, 2007)

  13. Conclusion • Thermal energy storage is imperative to make solar energy more reliable and competitive • Further research in phase changing material can improve the efficiency of energy storage • Design of the system is also important in optimizing energy storage

  14. References • Aghbalou, F., F. Badia, and J. Illa. “Exergetic Optimization of Solar Collector and Thermal Energy Storage System.” International Journal of Heat and Mass Transfer 49.7-8 (Apr. 2006): 1255-1263. ScienceDirect. Elsevier. 16 Nov. 2007 <http://www.sciencedirect.com/>. • Badescu, Viorel. “Model of a Thermal Energy Storage Device Integrated into a Solar Assisted Heat Pump System for Space Heating.” Energy Conversion and Management 44.10 (June 2003): 1589-1604. ScienceDirect. Elsevier. 16 Nov. 2007 <http://www.sciencedirect.com/>. • Denholm, Paul, and Robert M. Margolis. “Evaluating the Limits of Solar Photovoltaics (PVs) in Electric Power Systems Utilizing Energy Storage and Other Enabling Technologies.” Energy Policy 35.9 (Sept. 2007): 4424-4433. ScienceDirect. Elsevier. 16 Nov. 2007 <http://www.sciencedirect.com/>. • Farid, Mohammed M., et al. “A Review on Phase Change Energy Storage: Materials and Applications.” Energy Conversion and Management 45.9-19 (June 2004): 1597-1615. ScienceDirect. Elsevier. 17 Nov. 2007 <http://www.sciencedirect.com.ezproxy.lib.utexas.edu/>. • Fath, Hassan E. S. “Technical Assessment of Solar Thermal Energy Storage Technologies.” Renewable Energy 13.1-4 (Summer 1998): 35-40. ScienceDirect. Elsevier. 17 Nov. 2007 <http://www.sciencedirect.com.ezproxy.lib.utexas.edu/>. • Kenisarin, Murat, and Khamid Mahkamov. “Solar Energy Storage Using Phase Change Materials.” Renewable and Sustainable Energy Reviews 11.9 (Dec. 2007): 1913-1965. ScienceDirect. Elsevier. 17 Nov. 2007 <http://www.sciencedirect.com.ezproxy.lib.utexas.edu/>. • Koca, Ahmet, et al. “Energy and Exergy Analysis of a Latent Heat Storage System with Phase Change Material for a Solar Collector.” Renewable Energy (May 2007): 1-8. ScienceDirect. Elsevier. 16 Nov. 2007 <http://www.sciencedirect.com/>. • Kousksou, T., et al. “Second Law Analysis of Latent Thermal Storage for Solar System.” Solar Energy Materials and Solar Cells 91.14 (Sept. 2007): 1275-1281. ScienceDirect. Elsevier. 19 Nov. 2007 <http://www.sciencedirect.com.ezproxy.lib.utexas.edu/>. • Pasupathy, A., R. Velraj, and R. V. Seeniraj. “Phase Change Material-based Building Architecture for Thermal Management in Residential and Commercial Establisments.” Renewable & Sustainable Energy Reviews 12.1 (Jan. 2008): 39-64. ScienceDirect. Elsevier. 18 Nov. 2007 <http://www.sciencedirect.com/>. • Regin, A. Felix, S. C. Solanki, and J. S. Saini. “Heat Transfer Characteristics of Thermal Energy Storage System Using PCM Capsules: A Review.” Renewable and Sustainable Energy Reviews (Aug. 2007): 1-14. ScienceDirect. Elsevier. 20 Nov. 2007 <http://www.sciencedirect.com.ezproxy.lib.utexas.edu/>.

  15. Other Applications • Cooling of heat and electrical engines • Cooling: use of off-peak rates • Cooling: food, wine, milk products (absorbing peaks in demand), greenhouses • Heating and hot water: using off-peak rates • Medical applications: transportation of blood, operating tables, hot–cold therapies • Passive storage in bio-climatic building/architecture (HDPE, paraffin) • Safety: temperature level maintenance in rooms with computers or electrical/electronic appliances • Smoothing exothermic temperature peaks in chemical reactions • Solar power plants • Spacecraft thermal systems • Thermal comfort in vehicles • Thermal protection of electronic devices (integrated in the appliance) • Thermal protection of food: transport, hotel trade, ice-cream, etc. • Thermal storage of solar energy (Kenisarin, 2007)

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