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Today many of the solar cookers available in the market are direct cookers, without storage, and they are used for low to medium temperature cooking purposes. In this dissertation, experiments of heat collection, transportation and storage have been carried out using parabolic dish concentrators, steam as heat carrier and phase change material (PCM) as heat storage respectively. The design of the system has been focused to meet the demand for high temperature heat storage, in an economical, safe, robust and simplified way. The stored heat has mainly been tested for Injera baking purpose, the national food of Ethiopia, which requires intensive energy. Most households eat Injera three to four times per day. Injera needs a heat supply in the range of 180-220°C and more than 85% of Ethiopians use biomass fuel to bake this food. A nitrate salt mixture (solar salt) that has a melting point in this range of temperature was therefore selected as PCM media in this research. The research starts by developing two polar mounted parabolic dish concentrators that are suitable to closed loop self-circulation heat transportation. The first system was placed at NTNU and was coupled to an aluminum block heat storage that has PCM cavities and steam channels. This system was tested for natural and artificial heat source charging. The stored heat was tested for egg frying and water boiling. The second system, at Mekelle University, was coupled to Injera baking clay plate, which has an Imbedded coiled stainless steel steam pipe as a heating element. This system demonstrated an indirect solar Injera baking at about 160°C. However, the heating up time and the baking time interval were very long 3 hours and about 15 minutes respectively. The steam based solar Injera baking result has led to a new research line on Injera baking process and a review of its actual baking temperature. Therefore, Injera baking was tested on three different stove materials regarding its baking time, temperature and Injera quality on different baking surface temperatures. These experiments have identified the possibility of Injera baking as low as 120°C surface temperatures and the ordinary stove design can then be modified to save about 50% of its energy consumption. Another system was tested for alternative way of using solar energy indirectly. In this system, the high intensity solar radiation from the receiver’s of a double reflector parabolic dish concentrator was transported onto an absorber using a light guide. The system was designed for short distance radiation transportation and water was boiled in an experimental case. A third version of a heat storage was designed with conducting fines coupling a coiled top plate with a solar salt bed in a container below. Two units were made and tested at NTNU and Mekelle University. Injera baking tests were carried out on the top plate of the heat storage. Injera baking on a fully charged storage shows shorter baking times compared to conventional electric stoves. The system was demonstrated to the public and the Injeras baked on it and a solar cooked Ethiopian stews were served as a free lunch to the participants at Mekelle university. This was the first complete solar prepared Ethiopian food in the history of solar research in Ethiopia.

Ethiopia with a population of about 85 million meets 96% of its energy needs with bio-mass, charcoal, wood, animal dung and plant residues. More than 50% of this energy goes entirely on baking Injera. Injera the national food of the country demands 180-220 °C to be well cooked. In this article; Injera baking with solar energy on off-focus system, status of electric powered stove and the potential for solar powered stoves is discussed. The research and development of solar thermal for household energy consumption has not been well developed and adopted. One reason for this is that the system can only be used outdoor and at time of sun shine. In addition to the off-focus solar thermal application this paper discussed the integration of solar thermal with heat storage for a sustainable future use. The prototype for direct steam based baking was developed and tested in Mekelle University (Ethiopia) and Phase change material based heat storage prototype was developed and tested at NTNU. Both experiments showed the possibility of solar energy for Injera baking and its sustainability by including latent heat storage. This research gave hope to break the bottleneck related with on- focus solar cookers