Steam-based Charging-Discharging of a PCM Heat Storage
Latent heat storage and efficient heat transport technology helps to utilize the intermittent solar energy for continuous and near isothermal applications. However, many latent heat storages face challenges of storage charging, heat retaining, and discharging the stored heat. This paper tries to address the challenges of heat transportation and storage charging-discharging issues. The heat transportation from the receiver over some distance, from outside to the kitchen, is carried out with a stainless pipeline and water as heat transfer fluids. However, the charging-discharging process is carried by conduction method with the help of fins. In addition, the stored heat is retained for about one-two days by using aerogel insulation. The latent heat is stored in a phase change material (PCM), nitrate salt (mixture of 60%NaNO3 and 40%KNO3), which melts at 222ºC and has 109 J/g specific heat of fusion. The storage has the capacity of storing up to 250ºC heat and supply this heat isothermally during baking in the liquid-solid phase transition. However, the sensible heat stored in the solid and liquid form of the PCM is used to perform additional applications that do not require uniform heat which includes bread baking, kita (large pancake) baking and water boiling. The low thermal conductivity of PCM is enhanced by using extended aluminum fins that are attached to the baking plate and extruded inward to the storage. In this paper, two-phase loop thermosyphon of steam is used to manage the long distance heat transportation required between the receiver (outside) and the storage (inside a house). The steam in the thermosyphon flow has restricted to a maximum working temperature of 250ºC. Steam is selected for its highest heat capacity, availability and stable nature. It carries heat from the collector focus point and condenses in a coiled pipe imbedded in aluminum plate placed on top of the storage. Many fins are solidly attached to this plate to conduct the heat down to the PCM inside the storage during charging. This design configuration avoids pressure development inside the PCM storage and the charging-discharging temperature is recorded in three zones (top, middle and bottom) of the storage. The experimental and numerical results show that the heat transportation, retention and charging-discharging methods are effective.
Dobson, R. T & Ruppersberg, J. C. 2007. Flow and heat transfer in a closed loop thermo syphon: part I- theoretical simulation. J. Energy in South Africa, 18:32-80.
Foong, C, W., 2011, Experimental and numerical investigations of a small scale double-reflector concentrating solar system with latent heat storage, PhD Thesis, Norwegian university of science and Technology (NTNU), P: 36-61, Published
Hussein, H.M.s., El-Ghetany, H.H & Nada, S.A. 2008. Experimental investigation of novel indirect solar cooker with indoor PCM thermal storage and cooking unit. Energy Conversion and Management, 49(8):2237-2246 (DOI: 10.1016/j.enconman.2008.01.026).
Kuravi, S., Trahan, J., Goswami, D.Y., Rahman, M.M & Stefanakos, E.K. 2013. Thermal energy storage technologies and systems for concentrating solar power plants. Prog. Energy Combust. Sci., 39:285–319.
Okello, D., Ole, J. N & Eldad, J.K. B. 2014. Experimental investigation of thermal de-stratification in rock bed TES systems for high temperature applications. Energy Conversion and Management, 86:125–131.
Robynne, E. M & Groulx, D. 2014. Experimental study of the phase change and energy characteristics inside a cylindrical latent heat energy storage system: Part 1consecutive charging and discharging. Renewable Energy, 62:571-581.
More inside the PDF
Copyright (c) 2018 Momona Ethiopian Journal of Science
This work is licensed under a Creative Commons Attribution 4.0 International License.
COPYRIGHT AND LICENSE POLICY
The Momona Ethiopian Journal of Science accepts the manuscripts for consideration with the understanding that the manuscript has not been published and is not under consideration for publication elsewhere. Only original articles will be considered for publication if they have been published previously as abstracts, but not if they have been published previously as extended abstract (>1000 words). This applies to both electronic and print versions of the journal. The authors should assign copyright ownership to the Editorial Office of MEJS in the event that the manuscript is accepted for publication in the Momona Ethiopian Journal of Science. All accepted manuscripts must be accompanied by a copyright statement signed by all authors. A copy of the copyright form will be supplied along with the final reviewed version of the manuscript that is sent for final proof- reading. Authors may make multiple copies of the form if necessary and send to the Editorial Office with author’s signature(s) even individually.
All articles published by Momona Ethiopian Journal of Science (MEJS) are Open Access under the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0). Under this license, authors retain ownership of the copyright for their content, and anyone can copy, distribute, or reuse articles as long as the author and original source are properly cited. In all these cases for re-use, the authors will be given proper credit to the original publication in MEJS.