Abstract
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% NaNO 3 and 40% KNO 3 ), 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. Keywords : Solar energy, PCM storage, Latent heat storage, Two-phase thermosyphon.
Highlights
Solar thermal energy can be stored by using sensible heat storage (SHS) or latent heat storage (LHS) using a Phase change material (PCM)
The objective of this paper is to develop thermal energy storage to store the surplus solar energy during the day and keep it for later, late evening or early morning, use by supplying nearly isothermal heat during discharging
Storage design The PCM storage is designed to be charged by a two-phase self-circulating closed loop heat carrier, a polar mounted parabolic dish with sun tracker, a fixed receiver is designed to act as an evaporator and aluminum casted plate with extruded fins down to the PCM is placed on top of the storage
Summary
Solar thermal energy can be stored by using sensible heat storage (SHS) or latent heat storage (LHS) using a Phase change material (PCM). The stored heat can be used for different applications such as cooking, space heating, hot water supply etc. Latent heat storage provides higher storage capacity, compact size, and nearly isothermal heat supply. SHS such as Momona Ethiopian Journal of Science (MEJS), V10(1):15-27, 2018 ©CNCS, Mekelle University, ISSN:2220-184X.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
