Abstract
In Ethiopia, there is an abundant source of solar energy that is estimated to 5.3 kWh/m2/day. However, more than 90% of the society uses biomass as a main source of energy for cooking due to lack of technologies to convert this energy. Replacing these cooking activities by using renewable energy resources decreases pollution and reduces deforestation significantly. Using the solar energy in day time has no problem. For night time however, the system needs some kind of back-up system to make the daytime solar energy available. This back-up should have high-density energy storage and constant working temperature to perform a specific application. Latent heat storage using phase change materials (PCM) is one way of storing thermal energy. In the current study, a latent heat storage that uses a PCM material is used to store the solar energy aimed at utilizing solar energy for cooking Injera, main staple bread in Ethiopia. The PCM is a mixture of 60% NaNO3 and 40% KNO3 that are known as solar salts. The storage has a welded parallel aluminum fins with a gap of 40 mm in between to enhance the thermal conductivity during the charging-discharging process of the storage. The fins are extruded outside of the storage container to enable a side charging technique for the PCM. A prototype was developed with a solar salt of 17.5 kg and is tested for charging-discharging. The numerical simulation done on ANSYS and experimental results show an agreement and the system registered a 41.6% efficiency.
Highlights
Energy storage technologies have been in use for different purposes
Six of them were attached to the phase change materials (PCM) and the remaining six attached to the fins
Six of them were attached to the PCM and the remaining six attached to the fins as the storage has symmetric features
Summary
Energy storage technologies have been in use for different purposes. There is a growing interest of solar thermal utilization. The two widely used heat storages in solar thermal applications are sensible and latent heat storages. These storages are used in different applications such as in drying, space heating, cooking, power generation. The temperature change in sensible heat storage comes as a result of the absorption of solar radiation by the material. Latent heat is the energy absorbed and released by a substance during its phase change from solid to liquid, liquid to gas and vice versa
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